1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2024 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2024 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2024 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * Debugger Adapter Protocol:: The Debugger Adapter Protocol.
163 * JIT Interface:: Using the JIT debugging interface.
164 * In-Process Agent:: In-Process Agent
166 * GDB Bugs:: Reporting bugs in @value{GDBN}
168 @ifset SYSTEM_READLINE
169 * Command Line Editing: (rluserman). Command Line Editing
170 * Using History Interactively: (history). Using History Interactively
172 @ifclear SYSTEM_READLINE
173 * Command Line Editing:: Command Line Editing
174 * Using History Interactively:: Using History Interactively
176 * In Memoriam:: In Memoriam
177 * Formatting Documentation:: How to format and print @value{GDBN} documentation
178 * Installing GDB:: Installing @value{GDBN}
179 * Maintenance Commands:: Maintenance Commands
180 * Remote Protocol:: GDB Remote Serial Protocol
181 * Agent Expressions:: The @value{GDBN} Agent Expression Mechanism
182 * Target Descriptions:: How targets can describe themselves to
184 * Operating System Information:: Getting additional information from
186 * Trace File Format:: @value{GDBN} trace file format
187 * Index Section Format:: .gdb_index section format
188 * Debuginfod:: Download debugging resources with @code{debuginfod}
189 * Man Pages:: Manual pages
190 * Copying:: GNU General Public License says
191 how you can copy and share @value{GDBN}
192 * GNU Free Documentation License:: The license for this documentation
193 * Concept Index:: Index of @value{GDBN} concepts
194 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
195 functions, and Python data types
203 @unnumbered Summary of @value{GDBN}
205 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
206 going on ``inside'' another program while it executes---or what another
207 program was doing at the moment it crashed.
209 @value{GDBN} can do four main kinds of things (plus other things in support of
210 these) to help you catch bugs in the act:
214 Start your program, specifying anything that might affect its behavior.
217 Make your program stop on specified conditions.
220 Examine what has happened, when your program has stopped.
223 Change things in your program, so you can experiment with correcting the
224 effects of one bug and go on to learn about another.
227 You can use @value{GDBN} to debug programs written in C and C@t{++}.
228 For more information, see @ref{Supported Languages,,Supported Languages}.
229 For more information, see @ref{C,,C and C++}.
231 Support for D is partial. For information on D, see
235 Support for Modula-2 is partial. For information on Modula-2, see
236 @ref{Modula-2,,Modula-2}.
238 Support for OpenCL C is partial. For information on OpenCL C, see
239 @ref{OpenCL C,,OpenCL C}.
242 Debugging Pascal programs which use sets, subranges, file variables, or
243 nested functions does not currently work. @value{GDBN} does not support
244 entering expressions, printing values, or similar features using Pascal
248 @value{GDBN} can be used to debug programs written in Fortran, although
249 it may be necessary to refer to some variables with a trailing
252 @value{GDBN} can be used to debug programs written in Objective-C,
253 using either the Apple/NeXT or the GNU Objective-C runtime.
256 * Free Software:: Freely redistributable software
257 * Free Documentation:: Free Software Needs Free Documentation
258 * Contributors:: Contributors to GDB
262 @unnumberedsec Free Software
264 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
265 General Public License
266 (GPL). The GPL gives you the freedom to copy or adapt a licensed
267 program---but every person getting a copy also gets with it the
268 freedom to modify that copy (which means that they must get access to
269 the source code), and the freedom to distribute further copies.
270 Typical software companies use copyrights to limit your freedoms; the
271 Free Software Foundation uses the GPL to preserve these freedoms.
273 Fundamentally, the General Public License is a license which says that
274 you have these freedoms and that you cannot take these freedoms away
277 @node Free Documentation
278 @unnumberedsec Free Software Needs Free Documentation
280 The biggest deficiency in the free software community today is not in
281 the software---it is the lack of good free documentation that we can
282 include with the free software. Many of our most important
283 programs do not come with free reference manuals and free introductory
284 texts. Documentation is an essential part of any software package;
285 when an important free software package does not come with a free
286 manual and a free tutorial, that is a major gap. We have many such
289 Consider Perl, for instance. The tutorial manuals that people
290 normally use are non-free. How did this come about? Because the
291 authors of those manuals published them with restrictive terms---no
292 copying, no modification, source files not available---which exclude
293 them from the free software world.
295 That wasn't the first time this sort of thing happened, and it was far
296 from the last. Many times we have heard a GNU user eagerly describe a
297 manual that he is writing, his intended contribution to the community,
298 only to learn that he had ruined everything by signing a publication
299 contract to make it non-free.
301 Free documentation, like free software, is a matter of freedom, not
302 price. The problem with the non-free manual is not that publishers
303 charge a price for printed copies---that in itself is fine. (The Free
304 Software Foundation sells printed copies of manuals, too.) The
305 problem is the restrictions on the use of the manual. Free manuals
306 are available in source code form, and give you permission to copy and
307 modify. Non-free manuals do not allow this.
309 The criteria of freedom for a free manual are roughly the same as for
310 free software. Redistribution (including the normal kinds of
311 commercial redistribution) must be permitted, so that the manual can
312 accompany every copy of the program, both on-line and on paper.
314 Permission for modification of the technical content is crucial too.
315 When people modify the software, adding or changing features, if they
316 are conscientious they will change the manual too---so they can
317 provide accurate and clear documentation for the modified program. A
318 manual that leaves you no choice but to write a new manual to document
319 a changed version of the program is not really available to our
322 Some kinds of limits on the way modification is handled are
323 acceptable. For example, requirements to preserve the original
324 author's copyright notice, the distribution terms, or the list of
325 authors, are ok. It is also no problem to require modified versions
326 to include notice that they were modified. Even entire sections that
327 may not be deleted or changed are acceptable, as long as they deal
328 with nontechnical topics (like this one). These kinds of restrictions
329 are acceptable because they don't obstruct the community's normal use
332 However, it must be possible to modify all the @emph{technical}
333 content of the manual, and then distribute the result in all the usual
334 media, through all the usual channels. Otherwise, the restrictions
335 obstruct the use of the manual, it is not free, and we need another
336 manual to replace it.
338 Please spread the word about this issue. Our community continues to
339 lose manuals to proprietary publishing. If we spread the word that
340 free software needs free reference manuals and free tutorials, perhaps
341 the next person who wants to contribute by writing documentation will
342 realize, before it is too late, that only free manuals contribute to
343 the free software community.
345 If you are writing documentation, please insist on publishing it under
346 the GNU Free Documentation License or another free documentation
347 license. Remember that this decision requires your approval---you
348 don't have to let the publisher decide. Some commercial publishers
349 will use a free license if you insist, but they will not propose the
350 option; it is up to you to raise the issue and say firmly that this is
351 what you want. If the publisher you are dealing with refuses, please
352 try other publishers. If you're not sure whether a proposed license
353 is free, write to @email{licensing@@gnu.org}.
355 You can encourage commercial publishers to sell more free, copylefted
356 manuals and tutorials by buying them, and particularly by buying
357 copies from the publishers that paid for their writing or for major
358 improvements. Meanwhile, try to avoid buying non-free documentation
359 at all. Check the distribution terms of a manual before you buy it,
360 and insist that whoever seeks your business must respect your freedom.
361 Check the history of the book, and try to reward the publishers that
362 have paid or pay the authors to work on it.
364 The Free Software Foundation maintains a list of free documentation
365 published by other publishers, at
366 @url{http://www.fsf.org/doc/other-free-books.html}.
369 @unnumberedsec Contributors to @value{GDBN}
371 Richard Stallman was the original author of @value{GDBN}, and of many
372 other @sc{gnu} programs. Many others have contributed to its
373 development. This section attempts to credit major contributors. One
374 of the virtues of free software is that everyone is free to contribute
375 to it; with regret, we cannot actually acknowledge everyone here. The
376 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
377 blow-by-blow account.
379 Changes much prior to version 2.0 are lost in the mists of time.
382 @emph{Plea:} Additions to this section are particularly welcome. If you
383 or your friends (or enemies, to be evenhanded) have been unfairly
384 omitted from this list, we would like to add your names!
387 So that they may not regard their many labors as thankless, we
388 particularly thank those who shepherded @value{GDBN} through major
390 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
391 Jim Blandy (release 4.18);
392 Jason Molenda (release 4.17);
393 Stan Shebs (release 4.14);
394 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
395 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
396 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
397 Jim Kingdon (releases 3.5, 3.4, and 3.3);
398 and Randy Smith (releases 3.2, 3.1, and 3.0).
400 Richard Stallman, assisted at various times by Peter TerMaat, Chris
401 Hanson, and Richard Mlynarik, handled releases through 2.8.
403 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
404 in @value{GDBN}, with significant additional contributions from Per
405 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
406 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
407 much general update work leading to release 3.0).
409 @value{GDBN} uses the BFD subroutine library to examine multiple
410 object-file formats; BFD was a joint project of David V.
411 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
413 David Johnson wrote the original COFF support; Pace Willison did
414 the original support for encapsulated COFF.
416 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
418 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
419 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
421 Jean-Daniel Fekete contributed Sun 386i support.
422 Chris Hanson improved the HP9000 support.
423 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
424 David Johnson contributed Encore Umax support.
425 Jyrki Kuoppala contributed Altos 3068 support.
426 Jeff Law contributed HP PA and SOM support.
427 Keith Packard contributed NS32K support.
428 Doug Rabson contributed Acorn Risc Machine support.
429 Bob Rusk contributed Harris Nighthawk CX-UX support.
430 Chris Smith contributed Convex support (and Fortran debugging).
431 Jonathan Stone contributed Pyramid support.
432 Michael Tiemann contributed SPARC support.
433 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
434 Pace Willison contributed Intel 386 support.
435 Jay Vosburgh contributed Symmetry support.
436 Marko Mlinar contributed OpenRISC 1000 support.
438 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
440 Rich Schaefer and Peter Schauer helped with support of SunOS shared
443 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
444 about several machine instruction sets.
446 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
447 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
448 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
449 and RDI targets, respectively.
451 Brian Fox is the author of the readline libraries providing
452 command-line editing and command history.
454 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
455 Modula-2 support, and contributed the Languages chapter of this manual.
457 Fred Fish wrote most of the support for Unix System Vr4.
458 He also enhanced the command-completion support to cover C@t{++} overloaded
461 Hitachi America (now Renesas America), Ltd. sponsored the support for
462 H8/300, H8/500, and Super-H processors.
464 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
466 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
469 Toshiba sponsored the support for the TX39 Mips processor.
471 Matsushita sponsored the support for the MN10200 and MN10300 processors.
473 Fujitsu sponsored the support for SPARClite and FR30 processors.
475 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
478 Michael Snyder added support for tracepoints.
480 Stu Grossman wrote gdbserver.
482 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
483 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
485 The following people at the Hewlett-Packard Company contributed
486 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
487 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
488 compiler, and the Text User Interface (nee Terminal User Interface):
489 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
490 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
491 provided HP-specific information in this manual.
493 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
494 Robert Hoehne made significant contributions to the DJGPP port.
496 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
497 development since 1991. Cygnus engineers who have worked on @value{GDBN}
498 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
499 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
500 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
501 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
502 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
503 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
504 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
505 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
506 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
507 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
508 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
509 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
510 Zuhn have made contributions both large and small.
512 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
513 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
515 Jim Blandy added support for preprocessor macros, while working for Red
518 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
519 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
520 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
521 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
522 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
523 with the migration of old architectures to this new framework.
525 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
526 unwinder framework, this consisting of a fresh new design featuring
527 frame IDs, independent frame sniffers, and the sentinel frame. Mark
528 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
529 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
530 trad unwinders. The architecture-specific changes, each involving a
531 complete rewrite of the architecture's frame code, were carried out by
532 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
533 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
534 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
535 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
538 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
539 Tensilica, Inc.@: contributed support for Xtensa processors. Others
540 who have worked on the Xtensa port of @value{GDBN} in the past include
541 Steve Tjiang, John Newlin, and Scott Foehner.
543 Michael Eager and staff of Xilinx, Inc., contributed support for the
544 Xilinx MicroBlaze architecture.
546 Initial support for the FreeBSD/mips target and native configuration
547 was developed by SRI International and the University of Cambridge
548 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
549 ("CTSRD"), as part of the DARPA CRASH research programme.
551 Initial support for the FreeBSD/riscv target and native configuration
552 was developed by SRI International and the University of Cambridge
553 Computer Laboratory (Department of Computer Science and Technology)
554 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
555 SSITH research programme.
557 The original port to the OpenRISC 1000 is believed to be due to
558 Alessandro Forin and Per Bothner. More recent ports have been the work
559 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
562 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
563 the Linux kernel BPF virtual architecture. This work was sponsored by
567 @chapter A Sample @value{GDBN} Session
569 You can use this manual at your leisure to read all about @value{GDBN}.
570 However, a handful of commands are enough to get started using the
571 debugger. This chapter illustrates those commands.
574 In this sample session, we emphasize user input like this: @b{input},
575 to make it easier to pick out from the surrounding output.
578 @c FIXME: this example may not be appropriate for some configs, where
579 @c FIXME...primary interest is in remote use.
581 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
582 processor) exhibits the following bug: sometimes, when we change its
583 quote strings from the default, the commands used to capture one macro
584 definition within another stop working. In the following short @code{m4}
585 session, we define a macro @code{foo} which expands to @code{0000}; we
586 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
587 same thing. However, when we change the open quote string to
588 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
589 procedure fails to define a new synonym @code{baz}:
598 @b{define(bar,defn(`foo'))}
602 @b{changequote(<QUOTE>,<UNQUOTE>)}
604 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
607 m4: End of input: 0: fatal error: EOF in string
611 Let us use @value{GDBN} to try to see what is going on.
614 $ @b{@value{GDBP} m4}
615 @c FIXME: this falsifies the exact text played out, to permit smallbook
616 @c FIXME... format to come out better.
617 @value{GDBN} is free software and you are welcome to distribute copies
618 of it under certain conditions; type "show copying" to see
620 There is absolutely no warranty for @value{GDBN}; type "show warranty"
623 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
628 @value{GDBN} reads only enough symbol data to know where to find the
629 rest when needed; as a result, the first prompt comes up very quickly.
630 We now tell @value{GDBN} to use a narrower display width than usual, so
631 that examples fit in this manual.
634 (@value{GDBP}) @b{set width 70}
638 We need to see how the @code{m4} built-in @code{changequote} works.
639 Having looked at the source, we know the relevant subroutine is
640 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
641 @code{break} command.
644 (@value{GDBP}) @b{break m4_changequote}
645 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
649 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
650 control; as long as control does not reach the @code{m4_changequote}
651 subroutine, the program runs as usual:
654 (@value{GDBP}) @b{run}
655 Starting program: /work/Editorial/gdb/gnu/m4/m4
663 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
664 suspends execution of @code{m4}, displaying information about the
665 context where it stops.
668 @b{changequote(<QUOTE>,<UNQUOTE>)}
670 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
672 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
676 Now we use the command @code{n} (@code{next}) to advance execution to
677 the next line of the current function.
681 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
686 @code{set_quotes} looks like a promising subroutine. We can go into it
687 by using the command @code{s} (@code{step}) instead of @code{next}.
688 @code{step} goes to the next line to be executed in @emph{any}
689 subroutine, so it steps into @code{set_quotes}.
693 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
695 530 if (lquote != def_lquote)
699 The display that shows the subroutine where @code{m4} is now
700 suspended (and its arguments) is called a stack frame display. It
701 shows a summary of the stack. We can use the @code{backtrace}
702 command (which can also be spelled @code{bt}), to see where we are
703 in the stack as a whole: the @code{backtrace} command displays a
704 stack frame for each active subroutine.
707 (@value{GDBP}) @b{bt}
708 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
710 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
712 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
713 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
715 #4 0x79dc in expand_input () at macro.c:40
716 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
720 We step through a few more lines to see what happens. The first two
721 times, we can use @samp{s}; the next two times we use @code{n} to avoid
722 falling into the @code{xstrdup} subroutine.
726 0x3b5c 532 if (rquote != def_rquote)
728 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
729 def_lquote : xstrdup(lq);
731 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
734 538 len_lquote = strlen(rquote);
738 The last line displayed looks a little odd; we can examine the variables
739 @code{lquote} and @code{rquote} to see if they are in fact the new left
740 and right quotes we specified. We use the command @code{p}
741 (@code{print}) to see their values.
744 (@value{GDBP}) @b{p lquote}
745 $1 = 0x35d40 "<QUOTE>"
746 (@value{GDBP}) @b{p rquote}
747 $2 = 0x35d50 "<UNQUOTE>"
751 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
752 To look at some context, we can display ten lines of source
753 surrounding the current line with the @code{l} (@code{list}) command.
759 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
761 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
764 538 len_lquote = strlen(rquote);
765 539 len_rquote = strlen(lquote);
772 Let us step past the two lines that set @code{len_lquote} and
773 @code{len_rquote}, and then examine the values of those variables.
777 539 len_rquote = strlen(lquote);
780 (@value{GDBP}) @b{p len_lquote}
782 (@value{GDBP}) @b{p len_rquote}
787 That certainly looks wrong, assuming @code{len_lquote} and
788 @code{len_rquote} are meant to be the lengths of @code{lquote} and
789 @code{rquote} respectively. We can set them to better values using
790 the @code{p} command, since it can print the value of
791 any expression---and that expression can include subroutine calls and
795 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
797 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
802 Is that enough to fix the problem of using the new quotes with the
803 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
804 executing with the @code{c} (@code{continue}) command, and then try the
805 example that caused trouble initially:
811 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
818 Success! The new quotes now work just as well as the default ones. The
819 problem seems to have been just the two typos defining the wrong
820 lengths. We allow @code{m4} exit by giving it an EOF as input:
824 Program exited normally.
828 The message @samp{Program exited normally.} is from @value{GDBN}; it
829 indicates @code{m4} has finished executing. We can end our @value{GDBN}
830 session with the @value{GDBN} @code{quit} command.
833 (@value{GDBP}) @b{quit}
837 @chapter Getting In and Out of @value{GDBN}
839 This chapter discusses how to start @value{GDBN}, and how to get out of it.
843 type @samp{@value{GDBP}} to start @value{GDBN}.
845 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
849 * Invoking GDB:: How to start @value{GDBN}
850 * Quitting GDB:: How to quit @value{GDBN}
851 * Shell Commands:: How to use shell commands inside @value{GDBN}
852 * Logging Output:: How to log @value{GDBN}'s output to a file
856 @section Invoking @value{GDBN}
858 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
859 @value{GDBN} reads commands from the terminal until you tell it to exit.
861 You can also run @code{@value{GDBP}} with a variety of arguments and options,
862 to specify more of your debugging environment at the outset.
864 The command-line options described here are designed
865 to cover a variety of situations; in some environments, some of these
866 options may effectively be unavailable.
868 The most usual way to start @value{GDBN} is with one argument,
869 specifying an executable program:
872 @value{GDBP} @var{program}
876 You can also start with both an executable program and a core file
880 @value{GDBP} @var{program} @var{core}
883 You can, instead, specify a process ID as a second argument or use option
884 @code{-p}, if you want to debug a running process:
887 @value{GDBP} @var{program} 1234
892 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
893 can omit the @var{program} filename.
895 Taking advantage of the second command-line argument requires a fairly
896 complete operating system; when you use @value{GDBN} as a remote
897 debugger attached to a bare board, there may not be any notion of
898 ``process'', and there is often no way to get a core dump. @value{GDBN}
899 will warn you if it is unable to attach or to read core dumps.
901 You can optionally have @code{@value{GDBP}} pass any arguments after the
902 executable file to the inferior using @code{--args}. This option stops
905 @value{GDBP} --args gcc -O2 -c foo.c
907 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
908 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
910 You can run @code{@value{GDBP}} without printing the front material, which describes
911 @value{GDBN}'s non-warranty, by specifying @code{--silent}
912 (or @code{-q}/@code{--quiet}):
915 @value{GDBP} --silent
919 You can further control how @value{GDBN} starts up by using command-line
920 options. @value{GDBN} itself can remind you of the options available.
930 to display all available options and briefly describe their use
931 (@samp{@value{GDBP} -h} is a shorter equivalent).
933 All options and command line arguments you give are processed
934 in sequential order. The order makes a difference when the
935 @samp{-x} option is used.
939 * File Options:: Choosing files
940 * Mode Options:: Choosing modes
941 * Startup:: What @value{GDBN} does during startup
942 * Initialization Files:: Initialization Files
946 @subsection Choosing Files
948 When @value{GDBN} starts, it reads any arguments other than options as
949 specifying an executable file and core file (or process ID). This is
950 the same as if the arguments were specified by the @samp{-se} and
951 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
952 first argument that does not have an associated option flag as
953 equivalent to the @samp{-se} option followed by that argument; and the
954 second argument that does not have an associated option flag, if any, as
955 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
956 If the second argument begins with a decimal digit, @value{GDBN} will
957 first attempt to attach to it as a process, and if that fails, attempt
958 to open it as a corefile. If you have a corefile whose name begins with
959 a digit, you can prevent @value{GDBN} from treating it as a pid by
960 prefixing it with @file{./}, e.g.@: @file{./12345}.
962 If @value{GDBN} has not been configured to included core file support,
963 such as for most embedded targets, then it will complain about a second
964 argument and ignore it.
966 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
967 form equivalents, the method used to search the file system for the
968 symbol and/or executable file is the same as that used by the
969 @code{file} command. @xref{Files, ,file}.
971 Many options have both long and short forms; both are shown in the
972 following list. @value{GDBN} also recognizes the long forms if you truncate
973 them, so long as enough of the option is present to be unambiguous.
974 (If you prefer, you can flag option arguments with @samp{--} rather
975 than @samp{-}, though we illustrate the more usual convention.)
977 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
978 @c way, both those who look for -foo and --foo in the index, will find
982 @item -symbols @var{file}
984 @cindex @code{--symbols}
986 Read symbol table from file @var{file}.
988 @item -exec @var{file}
990 @cindex @code{--exec}
992 Use file @var{file} as the executable file to execute when appropriate,
993 and for examining pure data in conjunction with a core dump.
997 Read symbol table from file @var{file} and use it as the executable
1000 @item -core @var{file}
1001 @itemx -c @var{file}
1002 @cindex @code{--core}
1004 Use file @var{file} as a core dump to examine.
1006 @item -pid @var{number}
1007 @itemx -p @var{number}
1008 @cindex @code{--pid}
1010 Connect to process ID @var{number}, as with the @code{attach} command.
1012 @item -command @var{file}
1013 @itemx -x @var{file}
1014 @cindex @code{--command}
1016 Execute commands from file @var{file}. The contents of this file is
1017 evaluated exactly as the @code{source} command would.
1018 @xref{Command Files,, Command files}.
1020 @item -eval-command @var{command}
1021 @itemx -ex @var{command}
1022 @cindex @code{--eval-command}
1024 Execute a single @value{GDBN} command.
1026 This option may be used multiple times to call multiple commands. It may
1027 also be interleaved with @samp{-command} as required.
1030 @value{GDBP} -ex 'target sim' -ex 'load' \
1031 -x setbreakpoints -ex 'run' a.out
1034 @item -init-command @var{file}
1035 @itemx -ix @var{file}
1036 @cindex @code{--init-command}
1038 Execute commands from file @var{file} before loading the inferior (but
1039 after loading gdbinit files).
1042 @item -init-eval-command @var{command}
1043 @itemx -iex @var{command}
1044 @cindex @code{--init-eval-command}
1046 Execute a single @value{GDBN} command before loading the inferior (but
1047 after loading gdbinit files).
1050 @item -early-init-command @var{file}
1051 @itemx -eix @var{file}
1052 @cindex @code{--early-init-command}
1054 Execute commands from @var{file} very early in the initialization
1055 process, before any output is produced. @xref{Startup}.
1057 @item -early-init-eval-command @var{command}
1058 @itemx -eiex @var{command}
1059 @cindex @code{--early-init-eval-command}
1060 @cindex @code{-eiex}
1061 Execute a single @value{GDBN} command very early in the initialization
1062 process, before any output is produced.
1064 @item -directory @var{directory}
1065 @itemx -d @var{directory}
1066 @cindex @code{--directory}
1068 Add @var{directory} to the path to search for source and script files.
1072 @cindex @code{--readnow}
1074 Read each symbol file's entire symbol table immediately, rather than
1075 the default, which is to read it incrementally as it is needed.
1076 This makes startup slower, but makes future operations faster.
1079 @anchor{--readnever}
1080 @cindex @code{--readnever}, command-line option
1081 Do not read each symbol file's symbolic debug information. This makes
1082 startup faster but at the expense of not being able to perform
1083 symbolic debugging. DWARF unwind information is also not read,
1084 meaning backtraces may become incomplete or inaccurate. One use of
1085 this is when a user simply wants to do the following sequence: attach,
1086 dump core, detach. Loading the debugging information in this case is
1087 an unnecessary cause of delay.
1091 @subsection Choosing Modes
1093 You can run @value{GDBN} in various alternative modes---for example, in
1094 batch mode or quiet mode.
1102 Do not execute commands found in any initialization files
1103 (@pxref{Initialization Files}).
1108 Do not execute commands found in any home directory initialization
1109 file (@pxref{Initialization Files,,Home directory initialization
1110 file}). The system wide and current directory initialization files
1116 @cindex @code{--quiet}
1117 @cindex @code{--silent}
1119 ``Quiet''. Do not print the introductory and copyright messages. These
1120 messages are also suppressed in batch mode.
1122 @kindex set startup-quietly
1123 @kindex show startup-quietly
1124 This can also be enabled using @code{set startup-quietly on}. The
1125 default is @code{off}. Use @code{show startup-quietly} to see the
1126 current setting. Place @code{set startup-quietly on} into your early
1127 initialization file (@pxref{Initialization Files,,Initialization
1128 Files}) to have future @value{GDBN} sessions startup quietly.
1131 @cindex @code{--batch}
1132 Run in batch mode. Exit with status @code{0} after processing all the
1133 command files specified with @samp{-x} (and all commands from
1134 initialization files, if not inhibited with @samp{-n}). Exit with
1135 nonzero status if an error occurs in executing the @value{GDBN} commands
1136 in the command files. Batch mode also disables pagination, sets unlimited
1137 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1138 off} were in effect (@pxref{Messages/Warnings}).
1140 Batch mode may be useful for running @value{GDBN} as a filter, for
1141 example to download and run a program on another computer; in order to
1142 make this more useful, the message
1145 Program exited normally.
1149 (which is ordinarily issued whenever a program running under
1150 @value{GDBN} control terminates) is not issued when running in batch
1154 @cindex @code{--batch-silent}
1155 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1156 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1157 unaffected). This is much quieter than @samp{-silent} and would be useless
1158 for an interactive session.
1160 This is particularly useful when using targets that give @samp{Loading section}
1161 messages, for example.
1163 Note that targets that give their output via @value{GDBN}, as opposed to
1164 writing directly to @code{stdout}, will also be made silent.
1166 @item -return-child-result
1167 @cindex @code{--return-child-result}
1168 The return code from @value{GDBN} will be the return code from the child
1169 process (the process being debugged), with the following exceptions:
1173 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1174 internal error. In this case the exit code is the same as it would have been
1175 without @samp{-return-child-result}.
1177 The user quits with an explicit value. E.g., @samp{quit 1}.
1179 The child process never runs, or is not allowed to terminate, in which case
1180 the exit code will be -1.
1183 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1184 when @value{GDBN} is being used as a remote program loader or simulator
1189 @cindex @code{--nowindows}
1191 ``No windows''. If @value{GDBN} comes with a graphical user interface
1192 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1193 interface. If no GUI is available, this option has no effect.
1197 @cindex @code{--windows}
1199 If @value{GDBN} includes a GUI, then this option requires it to be
1202 @item -cd @var{directory}
1204 Run @value{GDBN} using @var{directory} as its working directory,
1205 instead of the current directory.
1207 @item -data-directory @var{directory}
1208 @itemx -D @var{directory}
1209 @cindex @code{--data-directory}
1211 Run @value{GDBN} using @var{directory} as its data directory.
1212 The data directory is where @value{GDBN} searches for its
1213 auxiliary files. @xref{Data Files}.
1217 @cindex @code{--fullname}
1219 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1220 subprocess. It tells @value{GDBN} to output the full file name and line
1221 number in a standard, recognizable fashion each time a stack frame is
1222 displayed (which includes each time your program stops). This
1223 recognizable format looks like two @samp{\032} characters, followed by
1224 the file name, line number and character position separated by colons,
1225 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1226 @samp{\032} characters as a signal to display the source code for the
1229 @item -annotate @var{level}
1230 @cindex @code{--annotate}
1231 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1232 effect is identical to using @samp{set annotate @var{level}}
1233 (@pxref{Annotations}). The annotation @var{level} controls how much
1234 information @value{GDBN} prints together with its prompt, values of
1235 expressions, source lines, and other types of output. Level 0 is the
1236 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1237 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1238 that control @value{GDBN}, and level 2 has been deprecated.
1240 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1244 @cindex @code{--args}
1245 Change interpretation of command line so that arguments following the
1246 executable file are passed as command line arguments to the inferior.
1247 This option stops option processing.
1249 @item -baud @var{bps}
1251 @cindex @code{--baud}
1253 Set the line speed (baud rate or bits per second) of any serial
1254 interface used by @value{GDBN} for remote debugging.
1256 @item -l @var{timeout}
1258 Set the timeout (in seconds) of any communication used by @value{GDBN}
1259 for remote debugging.
1261 @item -tty @var{device}
1262 @itemx -t @var{device}
1263 @cindex @code{--tty}
1265 Run using @var{device} for your program's standard input and output.
1266 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1268 @c resolve the situation of these eventually
1270 @cindex @code{--tui}
1271 Activate the @dfn{Text User Interface} when starting. The Text User
1272 Interface manages several text windows on the terminal, showing
1273 source, assembly, registers and @value{GDBN} command outputs
1274 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1275 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1276 Using @value{GDBN} under @sc{gnu} Emacs}).
1278 @item -interpreter @var{interp}
1279 @cindex @code{--interpreter}
1280 Use the interpreter @var{interp} for interface with the controlling
1281 program or device. This option is meant to be set by programs which
1282 communicate with @value{GDBN} using it as a back end.
1283 @xref{Interpreters, , Command Interpreters}.
1285 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1286 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1287 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1288 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1289 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1290 interfaces are no longer supported.
1293 @cindex @code{--write}
1294 Open the executable and core files for both reading and writing. This
1295 is equivalent to the @samp{set write on} command inside @value{GDBN}
1299 @cindex @code{--statistics}
1300 This option causes @value{GDBN} to print statistics about time and
1301 memory usage after it completes each command and returns to the prompt.
1304 @cindex @code{--version}
1305 This option causes @value{GDBN} to print its version number and
1306 no-warranty blurb, and exit.
1308 @item -configuration
1309 @cindex @code{--configuration}
1310 This option causes @value{GDBN} to print details about its build-time
1311 configuration parameters, and then exit. These details can be
1312 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1317 @subsection What @value{GDBN} Does During Startup
1318 @cindex @value{GDBN} startup
1320 Here's the description of what @value{GDBN} does during session startup:
1325 Performs minimal setup required to initialize basic internal state.
1328 @cindex early initialization file
1329 Reads commands from the early initialization file (if any) in your
1330 home directory. Only a restricted set of commands can be placed into
1331 an early initialization file, see @ref{Initialization Files}, for
1335 Executes commands and command files specified by the @samp{-eiex} and
1336 @samp{-eix} command line options in their specified order. Only a
1337 restricted set of commands can be used with @samp{-eiex} and
1338 @samp{eix}, see @ref{Initialization Files}, for details.
1341 Sets up the command interpreter as specified by the command line
1342 (@pxref{Mode Options, interpreter}).
1346 Reads the system wide initialization file and the files from the
1347 system wide initialization directory, @pxref{System Wide Init Files}.
1350 Reads the initialization file (if any) in your home directory and
1351 executes all the commands in that file, @pxref{Home Directory Init
1354 @anchor{Option -init-eval-command}
1356 Executes commands and command files specified by the @samp{-iex} and
1357 @samp{-ix} options in their specified order. Usually you should use the
1358 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1359 settings before @value{GDBN} init files get executed and before inferior
1363 Processes command line options and operands.
1366 Reads and executes the commands from the initialization file (if any)
1367 in the current working directory as long as @samp{set auto-load
1368 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1369 Directory}). This is only done if the current directory is different
1370 from your home directory. Thus, you can have more than one init file,
1371 one generic in your home directory, and another, specific to the
1372 program you are debugging, in the directory where you invoke
1373 @value{GDBN}. @xref{Init File in the Current Directory during
1377 If the command line specified a program to debug, or a process to
1378 attach to, or a core file, @value{GDBN} loads any auto-loaded
1379 scripts provided for the program or for its loaded shared libraries.
1380 @xref{Auto-loading}.
1382 If you wish to disable the auto-loading during startup,
1383 you must do something like the following:
1386 $ gdb -iex "set auto-load python-scripts off" myprogram
1389 Option @samp{-ex} does not work because the auto-loading is then turned
1393 Executes commands and command files specified by the @samp{-ex} and
1394 @samp{-x} options in their specified order. @xref{Command Files}, for
1395 more details about @value{GDBN} command files.
1398 Reads the command history recorded in the @dfn{history file}.
1399 @xref{Command History}, for more details about the command history and the
1400 files where @value{GDBN} records it.
1403 @node Initialization Files
1404 @subsection Initialization Files
1405 @cindex init file name
1407 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1408 from several initialization files. These initialization files use the
1409 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1410 processed by @value{GDBN} in the same way.
1412 To display the list of initialization files loaded by @value{GDBN} at
1413 startup, in the order they will be loaded, you can use @kbd{gdb
1416 @cindex early initialization
1417 The @dfn{early initialization} file is loaded very early in
1418 @value{GDBN}'s initialization process, before the interpreter
1419 (@pxref{Interpreters}) has been initialized, and before the default
1420 target (@pxref{Targets}) is initialized. Only @code{set} or
1421 @code{source} commands should be placed into an early initialization
1422 file, and the only @code{set} commands that can be used are those that
1423 control how @value{GDBN} starts up.
1425 Commands that can be placed into an early initialization file will be
1426 documented as such throughout this manual. Any command that is not
1427 documented as being suitable for an early initialization file should
1428 instead be placed into a general initialization file. Command files
1429 passed to @code{--early-init-command} or @code{-eix} are also early
1430 initialization files, with the same command restrictions. Only
1431 commands that can appear in an early initialization file should be
1432 passed to @code{--early-init-eval-command} or @code{-eiex}.
1434 @cindex general initialization
1435 In contrast, the @dfn{general initialization} files are processed
1436 later, after @value{GDBN} has finished its own internal initialization
1437 process, any valid command can be used in these files.
1439 @cindex initialization file
1440 Throughout the rest of this document the term @dfn{initialization
1441 file} refers to one of the general initialization files, not the early
1442 initialization file. Any discussion of the early initialization file
1443 will specifically mention that it is the early initialization file
1446 As the system wide and home directory initialization files are
1447 processed before most command line options, changes to settings
1448 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1449 command line options and operands.
1451 The following sections describe where @value{GDBN} looks for the early
1452 initialization and initialization files, and the order that the files
1455 @subsubsection Home directory early initialization files
1457 @value{GDBN} initially looks for an early initialization file in the
1458 users home directory@footnote{On DOS/Windows systems, the home
1459 directory is the one pointed to by the @env{HOME} environment
1460 variable.}. There are a number of locations that @value{GDBN} will
1461 search in the home directory, these locations are searched in order
1462 and @value{GDBN} will load the first file that it finds, and
1463 subsequent locations will not be checked.
1465 On non-macOS hosts the locations searched are:
1468 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1469 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1471 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1472 by the environment variable @env{HOME}, if it is defined.
1474 The file @file{.gdbearlyinit} within the directory pointed to by the
1475 environment variable @env{HOME}, if it is defined.
1478 By contrast, on macOS hosts the locations searched are:
1481 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1482 directory pointed to by the environment variable @env{HOME}, if it is
1485 The file @file{.gdbearlyinit} within the directory pointed to by the
1486 environment variable @env{HOME}, if it is defined.
1489 It is possible to prevent the home directory early initialization file
1490 from being loaded using the @samp{-nx} or @samp{-nh} command line
1491 options, @pxref{Mode Options,,Choosing Modes}.
1493 @anchor{System Wide Init Files}
1494 @subsubsection System wide initialization files
1496 There are two locations that are searched for system wide
1497 initialization files. Both of these locations are always checked:
1501 @item @file{system.gdbinit}
1502 This is a single system-wide initialization file. Its location is
1503 specified with the @code{--with-system-gdbinit} configure option
1504 (@pxref{System-wide configuration}). It is loaded first when
1505 @value{GDBN} starts, before command line options have been processed.
1507 @item @file{system.gdbinit.d}
1508 This is the system-wide initialization directory. Its location is
1509 specified with the @code{--with-system-gdbinit-dir} configure option
1510 (@pxref{System-wide configuration}). Files in this directory are
1511 loaded in alphabetical order immediately after @file{system.gdbinit}
1512 (if enabled) when @value{GDBN} starts, before command line options
1513 have been processed. Files need to have a recognized scripting
1514 language extension (@file{.py}/@file{.scm}) or be named with a
1515 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1516 commands. @value{GDBN} will not recurse into any subdirectories of
1521 It is possible to prevent the system wide initialization files from
1522 being loaded using the @samp{-nx} command line option, @pxref{Mode
1523 Options,,Choosing Modes}.
1525 @anchor{Home Directory Init File}
1526 @subsubsection Home directory initialization file
1527 @cindex @file{gdbinit}
1528 @cindex @file{.gdbinit}
1529 @cindex @file{gdb.ini}
1531 After loading the system wide initialization files @value{GDBN} will
1532 look for an initialization file in the users home
1533 directory@footnote{On DOS/Windows systems, the home directory is the
1534 one pointed to by the @env{HOME} environment variable.}. There are a
1535 number of locations that @value{GDBN} will search in the home
1536 directory, these locations are searched in order and @value{GDBN} will
1537 load the first file that it finds, and subsequent locations will not
1540 On non-Apple hosts the locations searched are:
1542 @item $XDG_CONFIG_HOME/gdb/gdbinit
1543 @item $HOME/.config/gdb/gdbinit
1544 @item $HOME/.gdbinit
1547 While on Apple hosts the locations searched are:
1549 @item $HOME/Library/Preferences/gdb/gdbinit
1550 @item $HOME/.gdbinit
1553 It is possible to prevent the home directory initialization file from
1554 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1555 @pxref{Mode Options,,Choosing Modes}.
1557 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1558 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1559 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1560 uses the standard name, but if it finds a @file{gdb.ini} file in your
1561 home directory, it warns you about that and suggests to rename the
1562 file to the standard name.
1564 @anchor{Init File in the Current Directory during Startup}
1565 @subsubsection Local directory initialization file
1567 @value{GDBN} will check the current directory for a file called
1568 @file{.gdbinit}. It is loaded last, after command line options
1569 other than @samp{-x} and @samp{-ex} have been processed. The command
1570 line options @samp{-x} and @samp{-ex} are processed last, after
1571 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1574 If the file in the current directory was already loaded as the home
1575 directory initialization file then it will not be loaded a second
1578 It is possible to prevent the local directory initialization file from
1579 being loaded using the @samp{-nx} command line option, @pxref{Mode
1580 Options,,Choosing Modes}.
1583 @section Quitting @value{GDBN}
1584 @cindex exiting @value{GDBN}
1585 @cindex leaving @value{GDBN}
1588 @kindex quit @r{[}@var{expression}@r{]}
1589 @kindex exit @r{[}@var{expression}@r{]}
1590 @kindex q @r{(@code{quit})}
1591 @item quit @r{[}@var{expression}@r{]}
1592 @itemx exit @r{[}@var{expression}@r{]}
1594 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1595 @code{q}), the @code{exit} command, or type an end-of-file
1596 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1597 @value{GDBN} will terminate normally; otherwise it will terminate using
1598 the result of @var{expression} as the error code.
1602 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1603 terminates the action of any @value{GDBN} command that is in progress and
1604 returns to @value{GDBN} command level. It is safe to type the interrupt
1605 character at any time because @value{GDBN} does not allow it to take effect
1606 until a time when it is safe.
1608 If you have been using @value{GDBN} to control an attached process or
1609 device, you can release it with the @code{detach} command
1610 (@pxref{Attach, ,Debugging an Already-running Process}).
1612 @node Shell Commands
1613 @section Shell Commands
1615 If you need to execute occasional shell commands during your
1616 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1617 just use the @code{shell} command.
1622 @cindex shell escape
1623 @item shell @var{command-string}
1624 @itemx !@var{command-string}
1625 Invoke a shell to execute @var{command-string}.
1626 Note that no space is needed between @code{!} and @var{command-string}.
1627 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1628 exists, determines which shell to run. Otherwise @value{GDBN} uses
1629 the default shell (@file{/bin/sh} on GNU and Unix systems,
1630 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1633 You may also invoke shell commands from expressions, using the
1634 @code{$_shell} convenience function. @xref{$_shell convenience
1637 The utility @code{make} is often needed in development environments.
1638 You do not have to use the @code{shell} command for this purpose in
1643 @cindex calling make
1644 @item make @var{make-args}
1645 Execute the @code{make} program with the specified
1646 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1652 @cindex send the output of a gdb command to a shell command
1654 @item pipe [@var{command}] | @var{shell_command}
1655 @itemx | [@var{command}] | @var{shell_command}
1656 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1657 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1658 Executes @var{command} and sends its output to @var{shell_command}.
1659 Note that no space is needed around @code{|}.
1660 If no @var{command} is provided, the last command executed is repeated.
1662 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1663 can be used to specify an alternate delimiter string @var{delim} that separates
1664 the @var{command} from the @var{shell_command}.
1669 (@value{GDBP}) p var
1679 (@value{GDBP}) pipe p var|wc
1681 (@value{GDBP}) |p var|wc -l
1685 (@value{GDBP}) p /x var
1693 (@value{GDBP}) ||grep red
1697 (@value{GDBP}) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1698 this contains a PIPE char
1699 (@value{GDBP}) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1700 this contains a PIPE char!
1706 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1707 can be used to examine the exit status of the last shell command launched
1708 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1709 @xref{Convenience Vars,, Convenience Variables}.
1711 @node Logging Output
1712 @section Logging Output
1713 @cindex logging @value{GDBN} output
1714 @cindex save @value{GDBN} output to a file
1716 You may want to save the output of @value{GDBN} commands to a file.
1717 There are several commands to control @value{GDBN}'s logging.
1720 @kindex set logging enabled
1721 @item set logging enabled [on|off]
1722 Enable or disable logging.
1723 @cindex logging file name
1724 @item set logging file @var{file}
1725 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1726 @item set logging overwrite [on|off]
1727 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1728 you want @code{set logging enabled on} to overwrite the logfile instead.
1729 @item set logging redirect [on|off]
1730 By default, @value{GDBN} output will go to both the terminal and the logfile.
1731 Set @code{redirect} if you want output to go only to the log file.
1732 @item set logging debugredirect [on|off]
1733 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1734 Set @code{debugredirect} if you want debug output to go only to the log file.
1735 @kindex show logging
1737 Show the current values of the logging settings.
1740 You can also redirect the output of a @value{GDBN} command to a
1741 shell command. @xref{pipe}.
1743 @chapter @value{GDBN} Commands
1745 You can abbreviate a @value{GDBN} command to the first few letters of the command
1746 name, if that abbreviation is unambiguous; and you can repeat certain
1747 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1748 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1749 show you the alternatives available, if there is more than one possibility).
1752 * Command Syntax:: How to give commands to @value{GDBN}
1753 * Command Settings:: How to change default behavior of commands
1754 * Completion:: Command completion
1755 * Command Options:: Command options
1756 * Help:: How to ask @value{GDBN} for help
1759 @node Command Syntax
1760 @section Command Syntax
1762 A @value{GDBN} command is a single line of input. There is no limit on
1763 how long it can be. It starts with a command name, which is followed by
1764 arguments whose meaning depends on the command name. For example, the
1765 command @code{step} accepts an argument which is the number of times to
1766 step, as in @samp{step 5}. You can also use the @code{step} command
1767 with no arguments. Some commands do not allow any arguments.
1769 @cindex abbreviation
1770 @value{GDBN} command names may always be truncated if that abbreviation is
1771 unambiguous. Other possible command abbreviations are listed in the
1772 documentation for individual commands. In some cases, even ambiguous
1773 abbreviations are allowed; for example, @code{s} is specially defined as
1774 equivalent to @code{step} even though there are other commands whose
1775 names start with @code{s}. You can test abbreviations by using them as
1776 arguments to the @code{help} command.
1778 @cindex repeating commands
1779 @kindex RET @r{(repeat last command)}
1780 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1781 repeat the previous command. Certain commands (for example, @code{run})
1782 will not repeat this way; these are commands whose unintentional
1783 repetition might cause trouble and which you are unlikely to want to
1784 repeat. User-defined commands can disable this feature; see
1785 @ref{Define, dont-repeat}.
1787 The @code{list} and @code{x} commands, when you repeat them with
1788 @key{RET}, construct new arguments rather than repeating
1789 exactly as typed. This permits easy scanning of source or memory.
1791 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1792 output, in a way similar to the common utility @code{more}
1793 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1794 @key{RET} too many in this situation, @value{GDBN} disables command
1795 repetition after any command that generates this sort of display.
1797 @kindex # @r{(a comment)}
1799 Any text from a @kbd{#} to the end of the line is a comment; it does
1800 nothing. This is useful mainly in command files (@pxref{Command
1801 Files,,Command Files}).
1803 @cindex repeating command sequences
1804 @kindex Ctrl-o @r{(operate-and-get-next)}
1805 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1806 commands. This command accepts the current line, like @key{RET}, and
1807 then fetches the next line relative to the current line from the history
1811 @node Command Settings
1812 @section Command Settings
1813 @cindex default behavior of commands, changing
1814 @cindex default settings, changing
1816 Many commands change their behavior according to command-specific
1817 variables or settings. These settings can be changed with the
1818 @code{set} subcommands. For example, the @code{print} command
1819 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1820 settings changeable with the commands @code{set print elements
1821 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1823 You can change these settings to your preference in the gdbinit files
1824 loaded at @value{GDBN} startup. @xref{Startup}.
1826 The settings can also be changed interactively during the debugging
1827 session. For example, to change the limit of array elements to print,
1828 you can do the following:
1830 (@value{GDBP}) set print elements 10
1831 (@value{GDBP}) print some_array
1832 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1835 The above @code{set print elements 10} command changes the number of
1836 elements to print from the default of 200 to 10. If you only intend
1837 this limit of 10 to be used for printing @code{some_array}, then you
1838 must restore the limit back to 200, with @code{set print elements
1841 Some commands allow overriding settings with command options. For
1842 example, the @code{print} command supports a number of options that
1843 allow overriding relevant global print settings as set by @code{set
1844 print} subcommands. @xref{print options}. The example above could be
1847 (@value{GDBP}) print -elements 10 -- some_array
1848 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1851 Alternatively, you can use the @code{with} command to change a setting
1852 temporarily, for the duration of a command invocation.
1855 @kindex with command
1856 @kindex w @r{(@code{with})}
1858 @cindex temporarily change settings
1859 @item with @var{setting} [@var{value}] [-- @var{command}]
1860 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1861 Temporarily set @var{setting} to @var{value} for the duration of
1864 @var{setting} is any setting you can change with the @code{set}
1865 subcommands. @var{value} is the value to assign to @code{setting}
1866 while running @code{command}.
1868 If no @var{command} is provided, the last command executed is
1871 If a @var{command} is provided, it must be preceded by a double dash
1872 (@code{--}) separator. This is required because some settings accept
1873 free-form arguments, such as expressions or filenames.
1875 For example, the command
1877 (@value{GDBP}) with print array on -- print some_array
1880 is equivalent to the following 3 commands:
1882 (@value{GDBP}) set print array on
1883 (@value{GDBP}) print some_array
1884 (@value{GDBP}) set print array off
1887 The @code{with} command is particularly useful when you want to
1888 override a setting while running user-defined commands, or commands
1889 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1892 (@value{GDBP}) with print pretty on -- my_complex_command
1895 To change several settings for the same command, you can nest
1896 @code{with} commands. For example, @code{with language ada -- with
1897 print elements 10} temporarily changes the language to Ada and sets a
1898 limit of 10 elements to print for arrays and strings.
1903 @section Command Completion
1906 @cindex word completion
1907 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1908 only one possibility; it can also show you what the valid possibilities
1909 are for the next word in a command, at any time. This works for @value{GDBN}
1910 commands, @value{GDBN} subcommands, command options, and the names of symbols
1913 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1914 of a word. If there is only one possibility, @value{GDBN} fills in the
1915 word, and waits for you to finish the command (or press @key{RET} to
1916 enter it). For example, if you type
1918 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1919 @c complete accuracy in these examples; space introduced for clarity.
1920 @c If texinfo enhancements make it unnecessary, it would be nice to
1921 @c replace " @key" by "@key" in the following...
1923 (@value{GDBP}) info bre@key{TAB}
1927 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1928 the only @code{info} subcommand beginning with @samp{bre}:
1931 (@value{GDBP}) info breakpoints
1935 You can either press @key{RET} at this point, to run the @code{info
1936 breakpoints} command, or backspace and enter something else, if
1937 @samp{breakpoints} does not look like the command you expected. (If you
1938 were sure you wanted @code{info breakpoints} in the first place, you
1939 might as well just type @key{RET} immediately after @samp{info bre},
1940 to exploit command abbreviations rather than command completion).
1942 If there is more than one possibility for the next word when you press
1943 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1944 characters and try again, or just press @key{TAB} a second time;
1945 @value{GDBN} displays all the possible completions for that word. For
1946 example, you might want to set a breakpoint on a subroutine whose name
1947 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1948 just sounds the bell. Typing @key{TAB} again displays all the
1949 function names in your program that begin with those characters, for
1953 (@value{GDBP}) b make_@key{TAB}
1954 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1955 make_a_section_from_file make_environ
1956 make_abs_section make_function_type
1957 make_blockvector make_pointer_type
1958 make_cleanup make_reference_type
1959 make_command make_symbol_completion_list
1960 (@value{GDBP}) b make_
1964 After displaying the available possibilities, @value{GDBN} copies your
1965 partial input (@samp{b make_} in the example) so you can finish the
1968 If the command you are trying to complete expects either a keyword or a
1969 number to follow, then @samp{NUMBER} will be shown among the available
1970 completions, for example:
1973 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1975 (@value{GDBP}) print -elements@tie{}
1979 Here, the option expects a number (e.g., @code{100}), not literal
1980 @code{NUMBER}. Such metasyntactical arguments are always presented in
1983 If you just want to see the list of alternatives in the first place, you
1984 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1985 means @kbd{@key{META} ?}. You can type this either by holding down a
1986 key designated as the @key{META} shift on your keyboard (if there is
1987 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1989 If the number of possible completions is large, @value{GDBN} will
1990 print as much of the list as it has collected, as well as a message
1991 indicating that the list may be truncated.
1994 (@value{GDBP}) b m@key{TAB}@key{TAB}
1996 <... the rest of the possible completions ...>
1997 *** List may be truncated, max-completions reached. ***
2002 This behavior can be controlled with the following commands:
2005 @kindex set max-completions
2006 @item set max-completions @var{limit}
2007 @itemx set max-completions unlimited
2008 Set the maximum number of completion candidates. @value{GDBN} will
2009 stop looking for more completions once it collects this many candidates.
2010 This is useful when completing on things like function names as collecting
2011 all the possible candidates can be time consuming.
2012 The default value is 200. A value of zero disables tab-completion.
2013 Note that setting either no limit or a very large limit can make
2015 @kindex show max-completions
2016 @item show max-completions
2017 Show the maximum number of candidates that @value{GDBN} will collect and show
2021 @cindex quotes in commands
2022 @cindex completion of quoted strings
2023 Sometimes the string you need, while logically a ``word'', may contain
2024 parentheses or other characters that @value{GDBN} normally excludes from
2025 its notion of a word. To permit word completion to work in this
2026 situation, you may enclose words in @code{'} (single quote marks) in
2027 @value{GDBN} commands.
2029 A likely situation where you might need this is in typing an
2030 expression that involves a C@t{++} symbol name with template
2031 parameters. This is because when completing expressions, GDB treats
2032 the @samp{<} character as word delimiter, assuming that it's the
2033 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2036 For example, when you want to call a C@t{++} template function
2037 interactively using the @code{print} or @code{call} commands, you may
2038 need to distinguish whether you mean the version of @code{name} that
2039 was specialized for @code{int}, @code{name<int>()}, or the version
2040 that was specialized for @code{float}, @code{name<float>()}. To use
2041 the word-completion facilities in this situation, type a single quote
2042 @code{'} at the beginning of the function name. This alerts
2043 @value{GDBN} that it may need to consider more information than usual
2044 when you press @key{TAB} or @kbd{M-?} to request word completion:
2047 (@value{GDBP}) p 'func<@kbd{M-?}
2048 func<int>() func<float>()
2049 (@value{GDBP}) p 'func<
2052 When setting breakpoints however (@pxref{Location Specifications}), you don't
2053 usually need to type a quote before the function name, because
2054 @value{GDBN} understands that you want to set a breakpoint on a
2058 (@value{GDBP}) b func<@kbd{M-?}
2059 func<int>() func<float>()
2060 (@value{GDBP}) b func<
2063 This is true even in the case of typing the name of C@t{++} overloaded
2064 functions (multiple definitions of the same function, distinguished by
2065 argument type). For example, when you want to set a breakpoint you
2066 don't need to distinguish whether you mean the version of @code{name}
2067 that takes an @code{int} parameter, @code{name(int)}, or the version
2068 that takes a @code{float} parameter, @code{name(float)}.
2071 (@value{GDBP}) b bubble(@kbd{M-?}
2072 bubble(int) bubble(double)
2073 (@value{GDBP}) b bubble(dou@kbd{M-?}
2077 See @ref{quoting names} for a description of other scenarios that
2080 For more information about overloaded functions, see @ref{C Plus Plus
2081 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2082 overload-resolution off} to disable overload resolution;
2083 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2085 @cindex completion of structure field names
2086 @cindex structure field name completion
2087 @cindex completion of union field names
2088 @cindex union field name completion
2089 When completing in an expression which looks up a field in a
2090 structure, @value{GDBN} also tries@footnote{The completer can be
2091 confused by certain kinds of invalid expressions. Also, it only
2092 examines the static type of the expression, not the dynamic type.} to
2093 limit completions to the field names available in the type of the
2097 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2098 magic to_fputs to_rewind
2099 to_data to_isatty to_write
2100 to_delete to_put to_write_async_safe
2105 This is because the @code{gdb_stdout} is a variable of the type
2106 @code{struct ui_file} that is defined in @value{GDBN} sources as
2113 ui_file_flush_ftype *to_flush;
2114 ui_file_write_ftype *to_write;
2115 ui_file_write_async_safe_ftype *to_write_async_safe;
2116 ui_file_fputs_ftype *to_fputs;
2117 ui_file_read_ftype *to_read;
2118 ui_file_delete_ftype *to_delete;
2119 ui_file_isatty_ftype *to_isatty;
2120 ui_file_rewind_ftype *to_rewind;
2121 ui_file_put_ftype *to_put;
2126 @node Command Options
2127 @section Command options
2129 @cindex command options
2130 Some commands accept options starting with a leading dash. For
2131 example, @code{print -pretty}. Similarly to command names, you can
2132 abbreviate a @value{GDBN} option to the first few letters of the
2133 option name, if that abbreviation is unambiguous, and you can also use
2134 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2135 in an option (or to show you the alternatives available, if there is
2136 more than one possibility).
2138 @cindex command options, raw input
2139 Some commands take raw input as argument. For example, the print
2140 command processes arbitrary expressions in any of the languages
2141 supported by @value{GDBN}. With such commands, because raw input may
2142 start with a leading dash that would be confused with an option or any
2143 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2144 -pretty} or printing negative @code{p}?), if you specify any command
2145 option, then you must use a double-dash (@code{--}) delimiter to
2146 indicate the end of options.
2148 @cindex command options, boolean
2150 Some options are described as accepting an argument which can be
2151 either @code{on} or @code{off}. These are known as @dfn{boolean
2152 options}. Similarly to boolean settings commands---@code{on} and
2153 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2154 @code{enable} can also be used as ``true'' value, and any of @code{0},
2155 @code{no} and @code{disable} can also be used as ``false'' value. You
2156 can also omit a ``true'' value, as it is implied by default.
2158 For example, these are equivalent:
2161 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2162 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2165 You can discover the set of options some command accepts by completing
2166 on @code{-} after the command name. For example:
2169 (@value{GDBP}) print -@key{TAB}@key{TAB}
2170 -address -max-depth -object -static-members
2171 -array -memory-tag-violations -pretty -symbol
2172 -array-indexes -nibbles -raw-values -union
2173 -elements -null-stop -repeats -vtbl
2176 Completion will in some cases guide you with a suggestion of what kind
2177 of argument an option expects. For example:
2180 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2185 Here, the option expects a number (e.g., @code{100}), not literal
2186 @code{NUMBER}. Such metasyntactical arguments are always presented in
2189 (For more on using the @code{print} command, see @ref{Data, ,Examining
2193 @section Getting Help
2194 @cindex online documentation
2197 You can always ask @value{GDBN} itself for information on its commands,
2198 using the command @code{help}.
2201 @kindex h @r{(@code{help})}
2204 You can use @code{help} (abbreviated @code{h}) with no arguments to
2205 display a short list of named classes of commands:
2209 List of classes of commands:
2211 aliases -- User-defined aliases of other commands
2212 breakpoints -- Making program stop at certain points
2213 data -- Examining data
2214 files -- Specifying and examining files
2215 internals -- Maintenance commands
2216 obscure -- Obscure features
2217 running -- Running the program
2218 stack -- Examining the stack
2219 status -- Status inquiries
2220 support -- Support facilities
2221 tracepoints -- Tracing of program execution without
2222 stopping the program
2223 user-defined -- User-defined commands
2225 Type "help" followed by a class name for a list of
2226 commands in that class.
2227 Type "help" followed by command name for full
2229 Command name abbreviations are allowed if unambiguous.
2232 @c the above line break eliminates huge line overfull...
2234 @item help @var{class}
2235 Using one of the general help classes as an argument, you can get a
2236 list of the individual commands in that class. If a command has
2237 aliases, the aliases are given after the command name, separated by
2238 commas. If an alias has default arguments, the full definition of
2239 the alias is given after the first line.
2240 For example, here is the help display for the class @code{status}:
2243 (@value{GDBP}) help status
2248 @c Line break in "show" line falsifies real output, but needed
2249 @c to fit in smallbook page size.
2250 info, inf, i -- Generic command for showing things
2251 about the program being debugged
2252 info address, iamain -- Describe where symbol SYM is stored.
2253 alias iamain = info address main
2254 info all-registers -- List of all registers and their contents,
2255 for selected stack frame.
2257 show, info set -- Generic command for showing things
2260 Type "help" followed by command name for full
2262 Command name abbreviations are allowed if unambiguous.
2266 @item help @var{command}
2267 With a command name as @code{help} argument, @value{GDBN} displays a
2268 short paragraph on how to use that command. If that command has
2269 one or more aliases, @value{GDBN} will display a first line with
2270 the command name and all its aliases separated by commas.
2271 This first line will be followed by the full definition of all aliases
2272 having default arguments.
2273 When asking the help for an alias, the documentation for the aliased
2276 A user-defined alias can optionally be documented using the
2277 @code{document} command (@pxref{Define, document}). @value{GDBN} then
2278 considers this alias as different from the aliased command: this alias
2279 is not listed in the aliased command help output, and asking help for
2280 this alias will show the documentation provided for the alias instead of
2281 the documentation of the aliased command.
2284 @item apropos [-v] @var{regexp}
2285 The @code{apropos} command searches through all of the @value{GDBN}
2286 commands and aliases, and their documentation, for the regular expression specified in
2287 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2288 which stands for @samp{verbose}, indicates to output the full documentation
2289 of the matching commands and highlight the parts of the documentation
2290 matching @var{regexp}. For example:
2301 alias -- Define a new command that is an alias of an existing command
2302 aliases -- User-defined aliases of other commands
2310 apropos -v cut.*thread apply
2314 results in the below output, where @samp{cut for 'thread apply}
2315 is highlighted if styling is enabled.
2319 taas -- Apply a command to all threads (ignoring errors
2322 shortcut for 'thread apply all -s COMMAND'
2324 tfaas -- Apply a command to all frames of all threads
2325 (ignoring errors and empty output).
2326 Usage: tfaas COMMAND
2327 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2332 @item complete @var{args}
2333 The @code{complete @var{args}} command lists all the possible completions
2334 for the beginning of a command. Use @var{args} to specify the beginning of the
2335 command you want completed. For example:
2341 @noindent results in:
2352 @noindent This is intended for use by @sc{gnu} Emacs.
2355 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2356 and @code{show} to inquire about the state of your program, or the state
2357 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2358 manual introduces each of them in the appropriate context. The listings
2359 under @code{info} and under @code{show} in the Command, Variable, and
2360 Function Index point to all the sub-commands. @xref{Command and Variable
2366 @kindex i @r{(@code{info})}
2368 This command (abbreviated @code{i}) is for describing the state of your
2369 program. For example, you can show the arguments passed to a function
2370 with @code{info args}, list the registers currently in use with @code{info
2371 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2372 You can get a complete list of the @code{info} sub-commands with
2373 @w{@code{help info}}.
2377 You can assign the result of an expression to an environment variable with
2378 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2379 @code{set prompt $}.
2383 In contrast to @code{info}, @code{show} is for describing the state of
2384 @value{GDBN} itself.
2385 You can change most of the things you can @code{show}, by using the
2386 related command @code{set}; for example, you can control what number
2387 system is used for displays with @code{set radix}, or simply inquire
2388 which is currently in use with @code{show radix}.
2391 To display all the settable parameters and their current
2392 values, you can use @code{show} with no arguments; you may also use
2393 @code{info set}. Both commands produce the same display.
2394 @c FIXME: "info set" violates the rule that "info" is for state of
2395 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2396 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2400 Here are several miscellaneous @code{show} subcommands, all of which are
2401 exceptional in lacking corresponding @code{set} commands:
2404 @kindex show version
2405 @cindex @value{GDBN} version number
2407 Show what version of @value{GDBN} is running. You should include this
2408 information in @value{GDBN} bug-reports. If multiple versions of
2409 @value{GDBN} are in use at your site, you may need to determine which
2410 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2411 commands are introduced, and old ones may wither away. Also, many
2412 system vendors ship variant versions of @value{GDBN}, and there are
2413 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2414 The version number is the same as the one announced when you start
2417 @kindex show copying
2418 @kindex info copying
2419 @cindex display @value{GDBN} copyright
2422 Display information about permission for copying @value{GDBN}.
2424 @kindex show warranty
2425 @kindex info warranty
2427 @itemx info warranty
2428 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2429 if your version of @value{GDBN} comes with one.
2431 @kindex show configuration
2432 @item show configuration
2433 Display detailed information about the way @value{GDBN} was configured
2434 when it was built. This displays the optional arguments passed to the
2435 @file{configure} script and also configuration parameters detected
2436 automatically by @command{configure}. When reporting a @value{GDBN}
2437 bug (@pxref{GDB Bugs}), it is important to include this information in
2443 @chapter Running Programs Under @value{GDBN}
2445 When you run a program under @value{GDBN}, you must first generate
2446 debugging information when you compile it.
2448 You may start @value{GDBN} with its arguments, if any, in an environment
2449 of your choice. If you are doing native debugging, you may redirect
2450 your program's input and output, debug an already running process, or
2451 kill a child process.
2454 * Compilation:: Compiling for debugging
2455 * Starting:: Starting your program
2456 * Arguments:: Your program's arguments
2457 * Environment:: Your program's environment
2459 * Working Directory:: Your program's working directory
2460 * Input/Output:: Your program's input and output
2461 * Attach:: Debugging an already-running process
2462 * Kill Process:: Killing the child process
2463 * Inferiors Connections and Programs:: Debugging multiple inferiors
2464 connections and programs
2465 * Threads:: Debugging programs with multiple threads
2466 * Forks:: Debugging forks
2467 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2471 @section Compiling for Debugging
2473 In order to debug a program effectively, you need to generate
2474 debugging information when you compile it. This debugging information
2475 is stored in the object file; it describes the data type of each
2476 variable or function and the correspondence between source line numbers
2477 and addresses in the executable code.
2479 To request debugging information, specify the @samp{-g} option when you run
2482 Programs that are to be shipped to your customers are compiled with
2483 optimizations, using the @samp{-O} compiler option. However, some
2484 compilers are unable to handle the @samp{-g} and @samp{-O} options
2485 together. Using those compilers, you cannot generate optimized
2486 executables containing debugging information.
2488 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2489 without @samp{-O}, making it possible to debug optimized code. We
2490 recommend that you @emph{always} use @samp{-g} whenever you compile a
2491 program. You may think your program is correct, but there is no sense
2492 in pushing your luck. For more information, see @ref{Optimized Code}.
2494 Older versions of the @sc{gnu} C compiler permitted a variant option
2495 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2496 format; if your @sc{gnu} C compiler has this option, do not use it.
2498 @value{GDBN} knows about preprocessor macros and can show you their
2499 expansion (@pxref{Macros}). Most compilers do not include information
2500 about preprocessor macros in the debugging information if you specify
2501 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2502 the @sc{gnu} C compiler, provides macro information if you are using
2503 the DWARF debugging format, and specify the option @option{-g3}.
2505 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2506 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2507 information on @value{NGCC} options affecting debug information.
2509 You will have the best debugging experience if you use the latest
2510 version of the DWARF debugging format that your compiler supports.
2511 DWARF is currently the most expressive and best supported debugging
2512 format in @value{GDBN}.
2516 @section Starting your Program
2522 @kindex r @r{(@code{run})}
2525 Use the @code{run} command to start your program under @value{GDBN}.
2526 You must first specify the program name with an argument to
2527 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2528 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2529 command (@pxref{Files, ,Commands to Specify Files}).
2533 If you are running your program in an execution environment that
2534 supports processes, @code{run} creates an inferior process and makes
2535 that process run your program. In some environments without processes,
2536 @code{run} jumps to the start of your program. Other targets,
2537 like @samp{remote}, are always running. If you get an error
2538 message like this one:
2541 The "remote" target does not support "run".
2542 Try "help target" or "continue".
2546 then use @code{continue} to run your program. You may need @code{load}
2547 first (@pxref{load}).
2549 The execution of a program is affected by certain information it
2550 receives from its superior. @value{GDBN} provides ways to specify this
2551 information, which you must do @emph{before} starting your program. (You
2552 can change it after starting your program, but such changes only affect
2553 your program the next time you start it.) This information may be
2554 divided into four categories:
2557 @item The @emph{arguments.}
2558 Specify the arguments to give your program as the arguments of the
2559 @code{run} command. If a shell is available on your target, the shell
2560 is used to pass the arguments, so that you may use normal conventions
2561 (such as wildcard expansion or variable substitution) in describing
2563 In Unix systems, you can control which shell is used with the
2564 @env{SHELL} environment variable. If you do not define @env{SHELL},
2565 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2566 use of any shell with the @code{set startup-with-shell} command (see
2569 @item The @emph{environment.}
2570 Your program normally inherits its environment from @value{GDBN}, but you can
2571 use the @value{GDBN} commands @code{set environment} and @code{unset
2572 environment} to change parts of the environment that affect
2573 your program. @xref{Environment, ,Your Program's Environment}.
2575 @item The @emph{working directory.}
2576 You can set your program's working directory with the command
2577 @kbd{set cwd}. If you do not set any working directory with this
2578 command, your program will inherit @value{GDBN}'s working directory if
2579 native debugging, or the remote server's working directory if remote
2580 debugging. @xref{Working Directory, ,Your Program's Working
2583 @item The @emph{standard input and output.}
2584 Your program normally uses the same device for standard input and
2585 standard output as @value{GDBN} is using. You can redirect input and output
2586 in the @code{run} command line, or you can use the @code{tty} command to
2587 set a different device for your program.
2588 @xref{Input/Output, ,Your Program's Input and Output}.
2591 @emph{Warning:} While input and output redirection work, you cannot use
2592 pipes to pass the output of the program you are debugging to another
2593 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2597 When you issue the @code{run} command, your program begins to execute
2598 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2599 of how to arrange for your program to stop. Once your program has
2600 stopped, you may call functions in your program, using the @code{print}
2601 or @code{call} commands. @xref{Data, ,Examining Data}.
2603 If the modification time of your symbol file has changed since the last
2604 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2605 table, and reads it again. When it does this, @value{GDBN} tries to retain
2606 your current breakpoints.
2611 @cindex run to main procedure
2612 The name of the main procedure can vary from language to language.
2613 With C or C@t{++}, the main procedure name is always @code{main}, but
2614 other languages such as Ada do not require a specific name for their
2615 main procedure. The debugger provides a convenient way to start the
2616 execution of the program and to stop at the beginning of the main
2617 procedure, depending on the language used.
2619 The @samp{start} command does the equivalent of setting a temporary
2620 breakpoint at the beginning of the main procedure and then invoking
2621 the @samp{run} command.
2623 @cindex elaboration phase
2624 Some programs contain an @dfn{elaboration} phase where some startup code is
2625 executed before the main procedure is called. This depends on the
2626 languages used to write your program. In C@t{++}, for instance,
2627 constructors for static and global objects are executed before
2628 @code{main} is called. It is therefore possible that the debugger stops
2629 before reaching the main procedure. However, the temporary breakpoint
2630 will remain to halt execution.
2632 Specify the arguments to give to your program as arguments to the
2633 @samp{start} command. These arguments will be given verbatim to the
2634 underlying @samp{run} command. Note that the same arguments will be
2635 reused if no argument is provided during subsequent calls to
2636 @samp{start} or @samp{run}.
2638 It is sometimes necessary to debug the program during elaboration. In
2639 these cases, using the @code{start} command would stop the execution
2640 of your program too late, as the program would have already completed
2641 the elaboration phase. Under these circumstances, either insert
2642 breakpoints in your elaboration code before running your program or
2643 use the @code{starti} command.
2647 @cindex run to first instruction
2648 The @samp{starti} command does the equivalent of setting a temporary
2649 breakpoint at the first instruction of a program's execution and then
2650 invoking the @samp{run} command. For programs containing an
2651 elaboration phase, the @code{starti} command will stop execution at
2652 the start of the elaboration phase.
2654 @anchor{set exec-wrapper}
2655 @kindex set exec-wrapper
2656 @item set exec-wrapper @var{wrapper}
2657 @itemx show exec-wrapper
2658 @itemx unset exec-wrapper
2659 When @samp{exec-wrapper} is set, the specified wrapper is used to
2660 launch programs for debugging. @value{GDBN} starts your program
2661 with a shell command of the form @kbd{exec @var{wrapper}
2662 @var{program}}. Quoting is added to @var{program} and its
2663 arguments, but not to @var{wrapper}, so you should add quotes if
2664 appropriate for your shell. The wrapper runs until it executes
2665 your program, and then @value{GDBN} takes control.
2667 You can use any program that eventually calls @code{execve} with
2668 its arguments as a wrapper. Several standard Unix utilities do
2669 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2670 with @code{exec "$@@"} will also work.
2672 For example, you can use @code{env} to pass an environment variable to
2673 the debugged program, without setting the variable in your shell's
2677 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2681 This command is available when debugging locally on most targets, excluding
2682 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2684 @kindex set startup-with-shell
2685 @anchor{set startup-with-shell}
2686 @item set startup-with-shell
2687 @itemx set startup-with-shell on
2688 @itemx set startup-with-shell off
2689 @itemx show startup-with-shell
2690 On Unix systems, by default, if a shell is available on your target,
2691 @value{GDBN}) uses it to start your program. Arguments of the
2692 @code{run} command are passed to the shell, which does variable
2693 substitution, expands wildcard characters and performs redirection of
2694 I/O. In some circumstances, it may be useful to disable such use of a
2695 shell, for example, when debugging the shell itself or diagnosing
2696 startup failures such as:
2700 Starting program: ./a.out
2701 During startup program terminated with signal SIGSEGV, Segmentation fault.
2705 which indicates the shell or the wrapper specified with
2706 @samp{exec-wrapper} crashed, not your program. Most often, this is
2707 caused by something odd in your shell's non-interactive mode
2708 initialization file---such as @file{.cshrc} for C-shell,
2709 $@file{.zshenv} for the Z shell, or the file specified in the
2710 @env{BASH_ENV} environment variable for BASH.
2712 @anchor{set auto-connect-native-target}
2713 @kindex set auto-connect-native-target
2714 @item set auto-connect-native-target
2715 @itemx set auto-connect-native-target on
2716 @itemx set auto-connect-native-target off
2717 @itemx show auto-connect-native-target
2719 By default, if the current inferior is not connected to any target yet
2720 (e.g., with @code{target remote}), the @code{run} command starts your
2721 program as a native process under @value{GDBN}, on your local machine.
2722 If you're sure you don't want to debug programs on your local machine,
2723 you can tell @value{GDBN} to not connect to the native target
2724 automatically with the @code{set auto-connect-native-target off}
2727 If @code{on}, which is the default, and if the current inferior is not
2728 connected to a target already, the @code{run} command automaticaly
2729 connects to the native target, if one is available.
2731 If @code{off}, and if the current inferior is not connected to a
2732 target already, the @code{run} command fails with an error:
2736 Don't know how to run. Try "help target".
2739 If the current inferior is already connected to a target, @value{GDBN}
2740 always uses it with the @code{run} command.
2742 In any case, you can explicitly connect to the native target with the
2743 @code{target native} command. For example,
2746 (@value{GDBP}) set auto-connect-native-target off
2748 Don't know how to run. Try "help target".
2749 (@value{GDBP}) target native
2751 Starting program: ./a.out
2752 [Inferior 1 (process 10421) exited normally]
2755 In case you connected explicitly to the @code{native} target,
2756 @value{GDBN} remains connected even if all inferiors exit, ready for
2757 the next @code{run} command. Use the @code{disconnect} command to
2760 Examples of other commands that likewise respect the
2761 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2762 proc}, @code{info os}.
2764 @kindex set disable-randomization
2765 @item set disable-randomization
2766 @itemx set disable-randomization on
2767 This option (enabled by default in @value{GDBN}) will turn off the native
2768 randomization of the virtual address space of the started program. This option
2769 is useful for multiple debugging sessions to make the execution better
2770 reproducible and memory addresses reusable across debugging sessions.
2772 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2773 On @sc{gnu}/Linux you can get the same behavior using
2776 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2779 @item set disable-randomization off
2780 Leave the behavior of the started executable unchanged. Some bugs rear their
2781 ugly heads only when the program is loaded at certain addresses. If your bug
2782 disappears when you run the program under @value{GDBN}, that might be because
2783 @value{GDBN} by default disables the address randomization on platforms, such
2784 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2785 disable-randomization off} to try to reproduce such elusive bugs.
2787 On targets where it is available, virtual address space randomization
2788 protects the programs against certain kinds of security attacks. In these
2789 cases the attacker needs to know the exact location of a concrete executable
2790 code. Randomizing its location makes it impossible to inject jumps misusing
2791 a code at its expected addresses.
2793 Prelinking shared libraries provides a startup performance advantage but it
2794 makes addresses in these libraries predictable for privileged processes by
2795 having just unprivileged access at the target system. Reading the shared
2796 library binary gives enough information for assembling the malicious code
2797 misusing it. Still even a prelinked shared library can get loaded at a new
2798 random address just requiring the regular relocation process during the
2799 startup. Shared libraries not already prelinked are always loaded at
2800 a randomly chosen address.
2802 Position independent executables (PIE) contain position independent code
2803 similar to the shared libraries and therefore such executables get loaded at
2804 a randomly chosen address upon startup. PIE executables always load even
2805 already prelinked shared libraries at a random address. You can build such
2806 executable using @command{gcc -fPIE -pie}.
2808 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2809 (as long as the randomization is enabled).
2811 @item show disable-randomization
2812 Show the current setting of the explicit disable of the native randomization of
2813 the virtual address space of the started program.
2818 @section Your Program's Arguments
2820 @cindex arguments (to your program)
2821 The arguments to your program can be specified by the arguments of the
2823 They are passed to a shell, which expands wildcard characters and
2824 performs redirection of I/O, and thence to your program. Your
2825 @env{SHELL} environment variable (if it exists) specifies what shell
2826 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2827 the default shell (@file{/bin/sh} on Unix).
2829 On non-Unix systems, the program is usually invoked directly by
2830 @value{GDBN}, which emulates I/O redirection via the appropriate system
2831 calls, and the wildcard characters are expanded by the startup code of
2832 the program, not by the shell.
2834 @code{run} with no arguments uses the same arguments used by the previous
2835 @code{run}, or those set by the @code{set args} command.
2840 Specify the arguments to be used the next time your program is run. If
2841 @code{set args} has no arguments, @code{run} executes your program
2842 with no arguments. Once you have run your program with arguments,
2843 using @code{set args} before the next @code{run} is the only way to run
2844 it again without arguments.
2848 Show the arguments to give your program when it is started.
2852 @section Your Program's Environment
2854 @cindex environment (of your program)
2855 The @dfn{environment} consists of a set of environment variables and
2856 their values. Environment variables conventionally record such things as
2857 your user name, your home directory, your terminal type, and your search
2858 path for programs to run. Usually you set up environment variables with
2859 the shell and they are inherited by all the other programs you run. When
2860 debugging, it can be useful to try running your program with a modified
2861 environment without having to start @value{GDBN} over again.
2865 @item path @var{directory}
2866 Add @var{directory} to the front of the @env{PATH} environment variable
2867 (the search path for executables) that will be passed to your program.
2868 The value of @env{PATH} used by @value{GDBN} does not change.
2869 You may specify several directory names, separated by whitespace or by a
2870 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2871 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2872 is moved to the front, so it is searched sooner.
2874 You can use the string @samp{$cwd} to refer to whatever is the current
2875 working directory at the time @value{GDBN} searches the path. If you
2876 use @samp{.} instead, it refers to the directory where you executed the
2877 @code{path} command. @value{GDBN} replaces @samp{.} in the
2878 @var{directory} argument (with the current path) before adding
2879 @var{directory} to the search path.
2880 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2881 @c document that, since repeating it would be a no-op.
2885 Display the list of search paths for executables (the @env{PATH}
2886 environment variable).
2888 @kindex show environment
2889 @item show environment @r{[}@var{varname}@r{]}
2890 Print the value of environment variable @var{varname} to be given to
2891 your program when it starts. If you do not supply @var{varname},
2892 print the names and values of all environment variables to be given to
2893 your program. You can abbreviate @code{environment} as @code{env}.
2895 @kindex set environment
2896 @anchor{set environment}
2897 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2898 Set environment variable @var{varname} to @var{value}. The value
2899 changes for your program (and the shell @value{GDBN} uses to launch
2900 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2901 values of environment variables are just strings, and any
2902 interpretation is supplied by your program itself. The @var{value}
2903 parameter is optional; if it is eliminated, the variable is set to a
2905 @c "any string" here does not include leading, trailing
2906 @c blanks. Gnu asks: does anyone care?
2908 For example, this command:
2915 tells the debugged program, when subsequently run, that its user is named
2916 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2917 are not actually required.)
2919 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2920 which also inherits the environment set with @code{set environment}.
2921 If necessary, you can avoid that by using the @samp{env} program as a
2922 wrapper instead of using @code{set environment}. @xref{set
2923 exec-wrapper}, for an example doing just that.
2925 Environment variables that are set by the user are also transmitted to
2926 @command{gdbserver} to be used when starting the remote inferior.
2927 @pxref{QEnvironmentHexEncoded}.
2929 @kindex unset environment
2930 @anchor{unset environment}
2931 @item unset environment @var{varname}
2932 Remove variable @var{varname} from the environment to be passed to your
2933 program. This is different from @samp{set env @var{varname} =};
2934 @code{unset environment} removes the variable from the environment,
2935 rather than assigning it an empty value.
2937 Environment variables that are unset by the user are also unset on
2938 @command{gdbserver} when starting the remote inferior.
2939 @pxref{QEnvironmentUnset}.
2942 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2943 the shell indicated by your @env{SHELL} environment variable if it
2944 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2945 names a shell that runs an initialization file when started
2946 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2947 for the Z shell, or the file specified in the @env{BASH_ENV}
2948 environment variable for BASH---any variables you set in that file
2949 affect your program. You may wish to move setting of environment
2950 variables to files that are only run when you sign on, such as
2951 @file{.login} or @file{.profile}.
2953 @node Working Directory
2954 @section Your Program's Working Directory
2956 @cindex working directory (of your program)
2957 Each time you start your program with @code{run}, the inferior will be
2958 initialized with the current working directory specified by the
2959 @kbd{set cwd} command. If no directory has been specified by this
2960 command, then the inferior will inherit @value{GDBN}'s current working
2961 directory as its working directory if native debugging, or it will
2962 inherit the remote server's current working directory if remote
2967 @cindex change inferior's working directory
2968 @anchor{set cwd command}
2969 @item set cwd @r{[}@var{directory}@r{]}
2970 Set the inferior's working directory to @var{directory}, which will be
2971 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2972 argument has been specified, the command clears the setting and resets
2973 it to an empty state. This setting has no effect on @value{GDBN}'s
2974 working directory, and it only takes effect the next time you start
2975 the inferior. The @file{~} in @var{directory} is a short for the
2976 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2977 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2978 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2981 You can also change @value{GDBN}'s current working directory by using
2982 the @code{cd} command.
2986 @cindex show inferior's working directory
2988 Show the inferior's working directory. If no directory has been
2989 specified by @kbd{set cwd}, then the default inferior's working
2990 directory is the same as @value{GDBN}'s working directory.
2993 @cindex change @value{GDBN}'s working directory
2995 @item cd @r{[}@var{directory}@r{]}
2996 Set the @value{GDBN} working directory to @var{directory}. If not
2997 given, @var{directory} uses @file{'~'}.
2999 The @value{GDBN} working directory serves as a default for the
3000 commands that specify files for @value{GDBN} to operate on.
3001 @xref{Files, ,Commands to Specify Files}.
3002 @xref{set cwd command}.
3006 Print the @value{GDBN} working directory.
3009 It is generally impossible to find the current working directory of
3010 the process being debugged (since a program can change its directory
3011 during its run). If you work on a system where @value{GDBN} supports
3012 the @code{info proc} command (@pxref{Process Information}), you can
3013 use the @code{info proc} command to find out the
3014 current working directory of the debuggee.
3017 @section Your Program's Input and Output
3022 By default, the program you run under @value{GDBN} does input and output to
3023 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3024 to its own terminal modes to interact with you, but it records the terminal
3025 modes your program was using and switches back to them when you continue
3026 running your program.
3029 @kindex info terminal
3031 Displays information recorded by @value{GDBN} about the terminal modes your
3035 You can redirect your program's input and/or output using shell
3036 redirection with the @code{run} command. For example,
3043 starts your program, diverting its output to the file @file{outfile}.
3046 @cindex controlling terminal
3047 Another way to specify where your program should do input and output is
3048 with the @code{tty} command. This command accepts a file name as
3049 argument, and causes this file to be the default for future @code{run}
3050 commands. It also resets the controlling terminal for the child
3051 process, for future @code{run} commands. For example,
3058 directs that processes started with subsequent @code{run} commands
3059 default to do input and output on the terminal @file{/dev/ttyb} and have
3060 that as their controlling terminal.
3062 An explicit redirection in @code{run} overrides the @code{tty} command's
3063 effect on the input/output device, but not its effect on the controlling
3066 When you use the @code{tty} command or redirect input in the @code{run}
3067 command, only the input @emph{for your program} is affected. The input
3068 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3069 for @code{set inferior-tty}.
3071 @cindex inferior tty
3072 @cindex set inferior controlling terminal
3073 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3074 display the name of the terminal that will be used for future runs of your
3078 @item set inferior-tty [ @var{tty} ]
3079 @kindex set inferior-tty
3080 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3081 restores the default behavior, which is to use the same terminal as
3084 @item show inferior-tty
3085 @kindex show inferior-tty
3086 Show the current tty for the program being debugged.
3090 @section Debugging an Already-running Process
3095 @item attach @var{process-id}
3096 This command attaches to a running process---one that was started
3097 outside @value{GDBN}. (@code{info files} shows your active
3098 targets.) The command takes as argument a process ID. The usual way to
3099 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3100 or with the @samp{jobs -l} shell command.
3102 @code{attach} does not repeat if you press @key{RET} a second time after
3103 executing the command.
3106 To use @code{attach}, your program must be running in an environment
3107 which supports processes; for example, @code{attach} does not work for
3108 programs on bare-board targets that lack an operating system. You must
3109 also have permission to send the process a signal.
3111 When you use @code{attach}, the debugger finds the program running in
3112 the process first by looking in the current working directory, then (if
3113 the program is not found) by using the source file search path
3114 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3115 the @code{file} command to load the program. @xref{Files, ,Commands to
3118 @anchor{set exec-file-mismatch}
3119 If the debugger can determine that the executable file running in the
3120 process it is attaching to does not match the current exec-file loaded
3121 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3122 handle the mismatch. @value{GDBN} tries to compare the files by
3123 comparing their build IDs (@pxref{build ID}), if available.
3126 @kindex exec-file-mismatch
3127 @cindex set exec-file-mismatch
3128 @item set exec-file-mismatch @samp{ask|warn|off}
3130 Whether to detect mismatch between the current executable file loaded
3131 by @value{GDBN} and the executable file used to start the process. If
3132 @samp{ask}, the default, display a warning and ask the user whether to
3133 load the process executable file; if @samp{warn}, just display a
3134 warning; if @samp{off}, don't attempt to detect a mismatch.
3135 If the user confirms loading the process executable file, then its symbols
3136 will be loaded as well.
3138 @cindex show exec-file-mismatch
3139 @item show exec-file-mismatch
3140 Show the current value of @code{exec-file-mismatch}.
3144 The first thing @value{GDBN} does after arranging to debug the specified
3145 process is to stop it. You can examine and modify an attached process
3146 with all the @value{GDBN} commands that are ordinarily available when
3147 you start processes with @code{run}. You can insert breakpoints; you
3148 can step and continue; you can modify storage. If you would rather the
3149 process continue running, you may use the @code{continue} command after
3150 attaching @value{GDBN} to the process.
3155 When you have finished debugging the attached process, you can use the
3156 @code{detach} command to release it from @value{GDBN} control. Detaching
3157 the process continues its execution. After the @code{detach} command,
3158 that process and @value{GDBN} become completely independent once more, and you
3159 are ready to @code{attach} another process or start one with @code{run}.
3160 @code{detach} does not repeat if you press @key{RET} again after
3161 executing the command.
3164 If you exit @value{GDBN} while you have an attached process, you detach
3165 that process. If you use the @code{run} command, you kill that process.
3166 By default, @value{GDBN} asks for confirmation if you try to do either of these
3167 things; you can control whether or not you need to confirm by using the
3168 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3172 @section Killing the Child Process
3177 Kill the child process in which your program is running under @value{GDBN}.
3180 This command is useful if you wish to debug a core dump instead of a
3181 running process. @value{GDBN} ignores any core dump file while your program
3184 On some operating systems, a program cannot be executed outside @value{GDBN}
3185 while you have breakpoints set on it inside @value{GDBN}. You can use the
3186 @code{kill} command in this situation to permit running your program
3187 outside the debugger.
3189 The @code{kill} command is also useful if you wish to recompile and
3190 relink your program, since on many systems it is impossible to modify an
3191 executable file while it is running in a process. In this case, when you
3192 next type @code{run}, @value{GDBN} notices that the file has changed, and
3193 reads the symbol table again (while trying to preserve your current
3194 breakpoint settings).
3196 @node Inferiors Connections and Programs
3197 @section Debugging Multiple Inferiors Connections and Programs
3199 @value{GDBN} lets you run and debug multiple programs in a single
3200 session. In addition, @value{GDBN} on some systems may let you run
3201 several programs simultaneously (otherwise you have to exit from one
3202 before starting another). On some systems @value{GDBN} may even let
3203 you debug several programs simultaneously on different remote systems.
3204 In the most general case, you can have multiple threads of execution
3205 in each of multiple processes, launched from multiple executables,
3206 running on different machines.
3209 @value{GDBN} represents the state of each program execution with an
3210 object called an @dfn{inferior}. An inferior typically corresponds to
3211 a process, but is more general and applies also to targets that do not
3212 have processes. Inferiors may be created before a process runs, and
3213 may be retained after a process exits. Inferiors have unique
3214 identifiers that are different from process ids. Usually each
3215 inferior will also have its own distinct address space, although some
3216 embedded targets may have several inferiors running in different parts
3217 of a single address space. Each inferior may in turn have multiple
3218 threads running in it.
3221 The commands @code{info inferiors} and @code{info connections}, which will be
3222 introduced below, accept a space-separated @dfn{ID list} as their argument
3223 specifying one or more elements on which to operate. A list element can be
3224 either a single non-negative number, like @samp{5}, or an ascending range of
3225 such numbers, like @samp{5-7}. A list can consist of any combination of such
3226 elements, even duplicates or overlapping ranges are valid. E.g.@:
3227 @samp{1 4-6 5 4-4} or @samp{1 2 4-7}.
3229 To find out what inferiors exist at any moment, use @w{@code{info
3233 @kindex info inferiors [ @var{id}@dots{} ]
3234 @item info inferiors
3235 Print a list of all inferiors currently being managed by @value{GDBN}.
3236 By default all inferiors are printed, but the ID list @var{id}@dots{} can be
3237 used to limit the display to just the requested inferiors.
3239 @value{GDBN} displays for each inferior (in this order):
3243 the inferior number assigned by @value{GDBN}
3246 the target system's inferior identifier
3249 the target connection the inferior is bound to, including the unique
3250 connection number assigned by @value{GDBN}, and the protocol used by
3254 the name of the executable the inferior is running.
3259 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3260 indicates the current inferior.
3264 @c end table here to get a little more width for example
3267 (@value{GDBP}) info inferiors
3268 Num Description Connection Executable
3269 * 1 process 3401 1 (native) goodbye
3270 2 process 2307 2 (extended-remote host:10000) hello
3273 To get information about the current inferior, use @code{inferior}:
3278 Shows information about the current inferior.
3282 @c end table here to get a little more width for example
3285 (@value{GDBP}) inferior
3286 [Current inferior is 1 [process 3401] (helloworld)]
3289 To find out what open target connections exist at any moment, use
3290 @w{@code{info connections}}:
3293 @kindex info connections [ @var{id}@dots{} ]
3294 @item info connections
3295 Print a list of all open target connections currently being managed by
3296 @value{GDBN}. By default all connections are printed, but the ID list
3297 @var{id}@dots{} can be used to limit the display to just the requested
3300 @value{GDBN} displays for each connection (in this order):
3304 the connection number assigned by @value{GDBN}.
3307 the protocol used by the connection.
3310 a textual description of the protocol used by the connection.
3315 An asterisk @samp{*} preceding the connection number indicates the
3316 connection of the current inferior.
3320 @c end table here to get a little more width for example
3323 (@value{GDBP}) info connections
3324 Num What Description
3325 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3326 2 native Native process
3327 3 core Local core dump file
3330 To switch focus between inferiors, use the @code{inferior} command:
3333 @kindex inferior @var{infno}
3334 @item inferior @var{infno}
3335 Make inferior number @var{infno} the current inferior. The argument
3336 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3337 in the first field of the @samp{info inferiors} display.
3340 @vindex $_inferior@r{, convenience variable}
3341 The debugger convenience variable @samp{$_inferior} contains the
3342 number of the current inferior. You may find this useful in writing
3343 breakpoint conditional expressions, command scripts, and so forth.
3344 @xref{Convenience Vars,, Convenience Variables}, for general
3345 information on convenience variables.
3347 You can get multiple executables into a debugging session via the
3348 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3349 systems @value{GDBN} can add inferiors to the debug session
3350 automatically by following calls to @code{fork} and @code{exec}. To
3351 remove inferiors from the debugging session use the
3352 @w{@code{remove-inferiors}} command.
3355 @anchor{add_inferior_cli}
3356 @kindex add-inferior
3357 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3358 Adds @var{n} inferiors to be run using @var{executable} as the
3359 executable; @var{n} defaults to 1. If no executable is specified,
3360 the inferiors begins empty, with no program. You can still assign or
3361 change the program assigned to the inferior at any time by using the
3362 @code{file} command with the executable name as its argument.
3364 By default, the new inferior begins connected to the same target
3365 connection as the current inferior. For example, if the current
3366 inferior was connected to @code{gdbserver} with @code{target remote},
3367 then the new inferior will be connected to the same @code{gdbserver}
3368 instance. The @samp{-no-connection} option starts the new inferior
3369 with no connection yet. You can then for example use the @code{target
3370 remote} command to connect to some other @code{gdbserver} instance,
3371 use @code{run} to spawn a local program, etc.
3373 @kindex clone-inferior
3374 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3375 Adds @var{n} inferiors ready to execute the same program as inferior
3376 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3377 number of the current inferior. This command copies the values of the
3378 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3379 current inferior to the new one. It also propagates changes the user
3380 made to environment variables using the @w{@code{set environment}} and
3381 @w{@code{unset environment}} commands. This is a convenient command
3382 when you want to run another instance of the inferior you are debugging.
3385 (@value{GDBP}) info inferiors
3386 Num Description Connection Executable
3387 * 1 process 29964 1 (native) helloworld
3388 (@value{GDBP}) clone-inferior
3391 (@value{GDBP}) info inferiors
3392 Num Description Connection Executable
3393 * 1 process 29964 1 (native) helloworld
3394 2 <null> 1 (native) helloworld
3397 You can now simply switch focus to inferior 2 and run it.
3399 @anchor{remove_inferiors_cli}
3400 @kindex remove-inferiors
3401 @item remove-inferiors @var{infno}@dots{}
3402 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3403 possible to remove an inferior that is running with this command. For
3404 those, use the @code{kill} or @code{detach} command first.
3408 To quit debugging one of the running inferiors that is not the current
3409 inferior, you can either detach from it by using the @w{@code{detach
3410 inferior}} command (allowing it to run independently), or kill it
3411 using the @w{@code{kill inferiors}} command:
3414 @kindex detach inferiors @var{infno}@dots{}
3415 @item detach inferior @var{infno}@dots{}
3416 Detach from the inferior or inferiors identified by @value{GDBN}
3417 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3418 still stays on the list of inferiors shown by @code{info inferiors},
3419 but its Description will show @samp{<null>}.
3421 @kindex kill inferiors @var{infno}@dots{}
3422 @item kill inferiors @var{infno}@dots{}
3423 Kill the inferior or inferiors identified by @value{GDBN} inferior
3424 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3425 stays on the list of inferiors shown by @code{info inferiors}, but its
3426 Description will show @samp{<null>}.
3429 After the successful completion of a command such as @code{detach},
3430 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3431 a normal process exit, the inferior is still valid and listed with
3432 @code{info inferiors}, ready to be restarted.
3435 To be notified when inferiors are started or exit under @value{GDBN}'s
3436 control use @w{@code{set print inferior-events}}:
3439 @kindex set print inferior-events
3440 @cindex print messages on inferior start and exit
3441 @item set print inferior-events
3442 @itemx set print inferior-events on
3443 @itemx set print inferior-events off
3444 The @code{set print inferior-events} command allows you to enable or
3445 disable printing of messages when @value{GDBN} notices that new
3446 inferiors have started or that inferiors have exited or have been
3447 detached. By default, these messages will be printed.
3449 @kindex show print inferior-events
3450 @item show print inferior-events
3451 Show whether messages will be printed when @value{GDBN} detects that
3452 inferiors have started, exited or have been detached.
3455 Many commands will work the same with multiple programs as with a
3456 single program: e.g., @code{print myglobal} will simply display the
3457 value of @code{myglobal} in the current inferior.
3460 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3461 get more info about the relationship of inferiors, programs, address
3462 spaces in a debug session. You can do that with the @w{@code{maint
3463 info program-spaces}} command.
3466 @kindex maint info program-spaces
3467 @item maint info program-spaces
3468 Print a list of all program spaces currently being managed by
3471 @value{GDBN} displays for each program space (in this order):
3475 the program space number assigned by @value{GDBN}
3478 the name of the executable loaded into the program space, with e.g.,
3479 the @code{file} command.
3482 the name of the core file loaded into the program space, with e.g.,
3483 the @code{core-file} command.
3488 An asterisk @samp{*} preceding the @value{GDBN} program space number
3489 indicates the current program space.
3491 In addition, below each program space line, @value{GDBN} prints extra
3492 information that isn't suitable to display in tabular form. For
3493 example, the list of inferiors bound to the program space.
3496 (@value{GDBP}) maint info program-spaces
3497 Id Executable Core File
3500 Bound inferiors: ID 1 (process 21561)
3503 Here we can see that no inferior is running the program @code{hello},
3504 while @code{process 21561} is running the program @code{goodbye}. On
3505 some targets, it is possible that multiple inferiors are bound to the
3506 same program space. The most common example is that of debugging both
3507 the parent and child processes of a @code{vfork} call. For example,
3510 (@value{GDBP}) maint info program-spaces
3511 Id Executable Core File
3513 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3516 Here, both inferior 2 and inferior 1 are running in the same program
3517 space as a result of inferior 1 having executed a @code{vfork} call.
3521 * Inferior-Specific Breakpoints:: Controlling breakpoints
3524 @node Inferior-Specific Breakpoints
3525 @subsection Inferior-Specific Breakpoints
3527 When debugging multiple inferiors, you can choose whether to set
3528 breakpoints for all inferiors, or for a particular inferior.
3531 @cindex breakpoints and inferiors
3532 @cindex inferior-specific breakpoints
3533 @kindex break @dots{} inferior @var{inferior-id}
3534 @item break @var{locspec} inferior @var{inferior-id}
3535 @itemx break @var{locspec} inferior @var{inferior-id} if @dots{}
3536 @var{locspec} specifies a code location or locations in your program.
3537 @xref{Location Specifications}, for details.
3539 Use the qualifier @samp{inferior @var{inferior-id}} with a breakpoint
3540 command to specify that you only want @value{GDBN} to stop when a
3541 particular inferior reaches this breakpoint. The @var{inferior-id}
3542 specifier is one of the inferior identifiers assigned by @value{GDBN},
3543 shown in the first column of the @samp{info inferiors} output.
3545 If you do not specify @samp{inferior @var{inferior-id}} when you set a
3546 breakpoint, the breakpoint applies to @emph{all} inferiors of your
3549 You can use the @code{inferior} qualifier on conditional breakpoints as
3550 well; in this case, place @samp{inferior @var{inferior-id}} before or
3551 after the breakpoint condition, like this:
3554 (@value{GDBP}) break frik.c:13 inferior 2 if bartab > lim
3558 Inferior-specific breakpoints are automatically deleted when the
3559 corresponding inferior is removed from @value{GDBN}. For example:
3562 (@value{GDBP}) remove-inferiors 2
3563 Inferior-specific breakpoint 3 deleted - inferior 2 has been removed.
3566 A breakpoint can't be both inferior-specific and thread-specific
3567 (@pxref{Thread-Specific Breakpoints}), or task-specific (@pxref{Ada
3568 Tasks}); using more than one of the @code{inferior}, @code{thread}, or
3569 @code{task} keywords when creating a breakpoint will give an error.
3572 @section Debugging Programs with Multiple Threads
3574 @cindex threads of execution
3575 @cindex multiple threads
3576 @cindex switching threads
3577 In some operating systems, such as GNU/Linux and Solaris, a single program
3578 may have more than one @dfn{thread} of execution. The precise semantics
3579 of threads differ from one operating system to another, but in general
3580 the threads of a single program are akin to multiple processes---except
3581 that they share one address space (that is, they can all examine and
3582 modify the same variables). On the other hand, each thread has its own
3583 registers and execution stack, and perhaps private memory.
3585 @value{GDBN} provides these facilities for debugging multi-thread
3589 @item automatic notification of new threads
3590 @item @samp{thread @var{thread-id}}, a command to switch among threads
3591 @item @samp{info threads}, a command to inquire about existing threads
3592 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3593 a command to apply a command to a list of threads
3594 @item thread-specific breakpoints
3595 @item @samp{set print thread-events}, which controls printing of
3596 messages on thread start and exit.
3597 @item @samp{set libthread-db-search-path @var{path}}, which lets
3598 the user specify which @code{libthread_db} to use if the default choice
3599 isn't compatible with the program.
3602 @cindex focus of debugging
3603 @cindex current thread
3604 The @value{GDBN} thread debugging facility allows you to observe all
3605 threads while your program runs---but whenever @value{GDBN} takes
3606 control, one thread in particular is always the focus of debugging.
3607 This thread is called the @dfn{current thread}. Debugging commands show
3608 program information from the perspective of the current thread.
3610 @cindex @code{New} @var{systag} message
3611 @cindex thread identifier (system)
3612 @c FIXME-implementors!! It would be more helpful if the [New...] message
3613 @c included GDB's numeric thread handle, so you could just go to that
3614 @c thread without first checking `info threads'.
3615 Whenever @value{GDBN} detects a new thread in your program, it displays
3616 the target system's identification for the thread with a message in the
3617 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3618 whose form varies depending on the particular system. For example, on
3619 @sc{gnu}/Linux, you might see
3622 [New Thread 0x41e02940 (LWP 25582)]
3626 when @value{GDBN} notices a new thread. In contrast, on other systems,
3627 the @var{systag} is simply something like @samp{process 368}, with no
3630 @c FIXME!! (1) Does the [New...] message appear even for the very first
3631 @c thread of a program, or does it only appear for the
3632 @c second---i.e.@: when it becomes obvious we have a multithread
3634 @c (2) *Is* there necessarily a first thread always? Or do some
3635 @c multithread systems permit starting a program with multiple
3636 @c threads ab initio?
3638 @anchor{thread numbers}
3639 @cindex thread number, per inferior
3640 @cindex thread identifier (GDB)
3641 For debugging purposes, @value{GDBN} associates its own thread number
3642 ---always a single integer---with each thread of an inferior. This
3643 number is unique between all threads of an inferior, but not unique
3644 between threads of different inferiors.
3646 @cindex qualified thread ID
3647 You can refer to a given thread in an inferior using the qualified
3648 @var{inferior-num}.@var{thread-num} syntax, also known as
3649 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3650 number and @var{thread-num} being the thread number of the given
3651 inferior. For example, thread @code{2.3} refers to thread number 3 of
3652 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3653 then @value{GDBN} infers you're referring to a thread of the current
3656 Until you create a second inferior, @value{GDBN} does not show the
3657 @var{inferior-num} part of thread IDs, even though you can always use
3658 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3659 of inferior 1, the initial inferior.
3661 @anchor{thread ID lists}
3662 @cindex thread ID lists
3663 Some commands accept a space-separated @dfn{thread ID list} as
3664 argument. A list element can be:
3668 A thread ID as shown in the first field of the @samp{info threads}
3669 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3673 A range of thread numbers, again with or without an inferior
3674 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3675 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3678 All threads of an inferior, specified with a star wildcard, with or
3679 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3680 @samp{1.*}) or @code{*}. The former refers to all threads of the
3681 given inferior, and the latter form without an inferior qualifier
3682 refers to all threads of the current inferior.
3686 For example, if the current inferior is 1, and inferior 7 has one
3687 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3688 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3689 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3690 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3694 @anchor{global thread numbers}
3695 @cindex global thread number
3696 @cindex global thread identifier (GDB)
3697 In addition to a @emph{per-inferior} number, each thread is also
3698 assigned a unique @emph{global} number, also known as @dfn{global
3699 thread ID}, a single integer. Unlike the thread number component of
3700 the thread ID, no two threads have the same global ID, even when
3701 you're debugging multiple inferiors.
3703 From @value{GDBN}'s perspective, a process always has at least one
3704 thread. In other words, @value{GDBN} assigns a thread number to the
3705 program's ``main thread'' even if the program is not multi-threaded.
3707 @vindex $_thread@r{, convenience variable}
3708 @vindex $_gthread@r{, convenience variable}
3709 @vindex $_inferior_thread_count@r{, convenience variable}
3710 The debugger convenience variables @samp{$_thread} and
3711 @samp{$_gthread} contain, respectively, the per-inferior thread number
3712 and the global thread number of the current thread. You may find this
3713 useful in writing breakpoint conditional expressions, command scripts,
3714 and so forth. The convenience variable @samp{$_inferior_thread_count}
3715 contains the number of live threads in the current inferior.
3716 @xref{Convenience Vars,, Convenience Variables}, for general
3717 information on convenience variables.
3719 When running in non-stop mode (@pxref{Non-Stop Mode}), where new
3720 threads can be created, and existing threads exit, at any time,
3721 @samp{$_inferior_thread_count} could return a different value each
3722 time it is evaluated.
3724 If @value{GDBN} detects the program is multi-threaded, it augments the
3725 usual message about stopping at a breakpoint with the ID and name of
3726 the thread that hit the breakpoint.
3729 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3732 Likewise when the program receives a signal:
3735 Thread 1 "main" received signal SIGINT, Interrupt.
3739 @anchor{info_threads}
3740 @kindex info threads
3741 @item info threads @r{[}-gid@r{]} @r{[}@var{thread-id-list}@r{]}
3743 Display information about one or more threads. With no arguments
3744 displays information about all threads. You can specify the list of
3745 threads that you want to display using the thread ID list syntax
3746 (@pxref{thread ID lists}).
3748 @value{GDBN} displays for each thread (in this order):
3752 the per-inferior thread number assigned by @value{GDBN}
3755 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3756 option was specified
3759 the target system's thread identifier (@var{systag})
3762 the thread's name, if one is known. A thread can either be named by
3763 the user (see @code{thread name}, below), or, in some cases, by the
3767 the current stack frame summary for that thread
3771 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3772 indicates the current thread.
3776 @c end table here to get a little more width for example
3779 (@value{GDBP}) info threads
3781 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3782 2 process 35 thread 23 0x34e5 in sigpause ()
3783 3 process 35 thread 27 0x34e5 in sigpause ()
3787 If you're debugging multiple inferiors, @value{GDBN} displays thread
3788 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3789 Otherwise, only @var{thread-num} is shown.
3791 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3792 indicating each thread's global thread ID:
3795 (@value{GDBP}) info threads
3796 Id GId Target Id Frame
3797 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3798 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3799 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3800 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3803 On Solaris, you can display more information about user threads with a
3804 Solaris-specific command:
3807 @item maint info sol-threads
3808 @kindex maint info sol-threads
3809 @cindex thread info (Solaris)
3810 Display info on Solaris user threads.
3814 @kindex thread @var{thread-id}
3815 @item thread @var{thread-id}
3816 Make thread ID @var{thread-id} the current thread. The command
3817 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3818 the first field of the @samp{info threads} display, with or without an
3819 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3821 @value{GDBN} responds by displaying the system identifier of the
3822 thread you selected, and its current stack frame summary:
3825 (@value{GDBP}) thread 2
3826 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3827 #0 some_function (ignore=0x0) at example.c:8
3828 8 printf ("hello\n");
3832 As with the @samp{[New @dots{}]} message, the form of the text after
3833 @samp{Switching to} depends on your system's conventions for identifying
3836 @anchor{thread apply all}
3837 @kindex thread apply
3838 @cindex apply command to several threads
3839 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3840 The @code{thread apply} command allows you to apply the named
3841 @var{command} to one or more threads. Specify the threads that you
3842 want affected using the thread ID list syntax (@pxref{thread ID
3843 lists}), or specify @code{all} to apply to all threads. To apply a
3844 command to all threads in descending order, type @kbd{thread apply all
3845 @var{command}}. To apply a command to all threads in ascending order,
3846 type @kbd{thread apply all -ascending @var{command}}.
3848 The @var{flag} arguments control what output to produce and how to handle
3849 errors raised when applying @var{command} to a thread. @var{flag}
3850 must start with a @code{-} directly followed by one letter in
3851 @code{qcs}. If several flags are provided, they must be given
3852 individually, such as @code{-c -q}.
3854 By default, @value{GDBN} displays some thread information before the
3855 output produced by @var{command}, and an error raised during the
3856 execution of a @var{command} will abort @code{thread apply}. The
3857 following flags can be used to fine-tune this behavior:
3861 The flag @code{-c}, which stands for @samp{continue}, causes any
3862 errors in @var{command} to be displayed, and the execution of
3863 @code{thread apply} then continues.
3865 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3866 or empty output produced by a @var{command} to be silently ignored.
3867 That is, the execution continues, but the thread information and errors
3870 The flag @code{-q} (@samp{quiet}) disables printing the thread
3874 Flags @code{-c} and @code{-s} cannot be used together.
3877 @cindex apply command to all threads (ignoring errors and empty output)
3878 @item taas [@var{option}]@dots{} @var{command}
3879 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3880 Applies @var{command} on all threads, ignoring errors and empty output.
3882 The @code{taas} command accepts the same options as the @code{thread
3883 apply all} command. @xref{thread apply all}.
3886 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3887 @item tfaas [@var{option}]@dots{} @var{command}
3888 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3889 Applies @var{command} on all frames of all threads, ignoring errors
3890 and empty output. Note that the flag @code{-s} is specified twice:
3891 The first @code{-s} ensures that @code{thread apply} only shows the thread
3892 information of the threads for which @code{frame apply} produces
3893 some output. The second @code{-s} is needed to ensure that @code{frame
3894 apply} shows the frame information of a frame only if the
3895 @var{command} successfully produced some output.
3897 It can for example be used to print a local variable or a function
3898 argument without knowing the thread or frame where this variable or argument
3901 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3904 The @code{tfaas} command accepts the same options as the @code{frame
3905 apply} command. @xref{Frame Apply,,frame apply}.
3908 @cindex name a thread
3909 @item thread name [@var{name}]
3910 This command assigns a name to the current thread. If no argument is
3911 given, any existing user-specified name is removed. The thread name
3912 appears in the @samp{info threads} display.
3914 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3915 determine the name of the thread as given by the OS. On these
3916 systems, a name specified with @samp{thread name} will override the
3917 system-give name, and removing the user-specified name will cause
3918 @value{GDBN} to once again display the system-specified name.
3921 @cindex search for a thread
3922 @item thread find [@var{regexp}]
3923 Search for and display thread ids whose name or @var{systag}
3924 matches the supplied regular expression.
3926 As well as being the complement to the @samp{thread name} command,
3927 this command also allows you to identify a thread by its target
3928 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3932 (@value{GDBP}) thread find 26688
3933 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3934 (@value{GDBP}) info thread 4
3936 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3939 @kindex set print thread-events
3940 @cindex print messages on thread start and exit
3941 @item set print thread-events
3942 @itemx set print thread-events on
3943 @itemx set print thread-events off
3944 The @code{set print thread-events} command allows you to enable or
3945 disable printing of messages when @value{GDBN} notices that new threads have
3946 started or that threads have exited. By default, these messages will
3947 be printed if detection of these events is supported by the target.
3948 Note that these messages cannot be disabled on all targets.
3950 @kindex show print thread-events
3951 @item show print thread-events
3952 Show whether messages will be printed when @value{GDBN} detects that threads
3953 have started and exited.
3956 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3957 more information about how @value{GDBN} behaves when you stop and start
3958 programs with multiple threads.
3960 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3961 watchpoints in programs with multiple threads.
3963 @anchor{set libthread-db-search-path}
3965 @kindex set libthread-db-search-path
3966 @cindex search path for @code{libthread_db}
3967 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3968 If this variable is set, @var{path} is a colon-separated list of
3969 directories @value{GDBN} will use to search for @code{libthread_db}.
3970 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3971 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3972 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3975 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3976 @code{libthread_db} library to obtain information about threads in the
3977 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3978 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3979 specific thread debugging library loading is enabled
3980 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3982 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3983 refers to the default system directories that are
3984 normally searched for loading shared libraries. The @samp{$sdir} entry
3985 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3986 (@pxref{libthread_db.so.1 file}).
3988 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3989 refers to the directory from which @code{libpthread}
3990 was loaded in the inferior process.
3992 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3993 @value{GDBN} attempts to initialize it with the current inferior process.
3994 If this initialization fails (which could happen because of a version
3995 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3996 will unload @code{libthread_db}, and continue with the next directory.
3997 If none of @code{libthread_db} libraries initialize successfully,
3998 @value{GDBN} will issue a warning and thread debugging will be disabled.
4000 Setting @code{libthread-db-search-path} is currently implemented
4001 only on some platforms.
4003 @kindex show libthread-db-search-path
4004 @item show libthread-db-search-path
4005 Display current libthread_db search path.
4007 @kindex set debug libthread-db
4008 @kindex show debug libthread-db
4009 @cindex debugging @code{libthread_db}
4010 @item set debug libthread-db
4011 @itemx show debug libthread-db
4012 Turns on or off display of @code{libthread_db}-related events.
4013 Use @code{1} to enable, @code{0} to disable.
4015 @kindex set debug threads
4016 @kindex show debug threads
4017 @cindex debugging @code{threads}
4018 @item set debug threads @r{[}on@r{|}off@r{]}
4019 @itemx show debug threads
4020 When @samp{on} @value{GDBN} will print additional messages when
4021 threads are created and deleted.
4025 @section Debugging Forks
4027 @cindex fork, debugging programs which call
4028 @cindex multiple processes
4029 @cindex processes, multiple
4030 On most systems, @value{GDBN} has no special support for debugging
4031 programs which create additional processes using the @code{fork}
4032 function. When a program forks, @value{GDBN} will continue to debug the
4033 parent process and the child process will run unimpeded. If you have
4034 set a breakpoint in any code which the child then executes, the child
4035 will get a @code{SIGTRAP} signal which (unless it catches the signal)
4036 will cause it to terminate.
4038 However, if you want to debug the child process there is a workaround
4039 which isn't too painful. Put a call to @code{sleep} in the code which
4040 the child process executes after the fork. It may be useful to sleep
4041 only if a certain environment variable is set, or a certain file exists,
4042 so that the delay need not occur when you don't want to run @value{GDBN}
4043 on the child. While the child is sleeping, use the @code{ps} program to
4044 get its process ID. Then tell @value{GDBN} (a new invocation of
4045 @value{GDBN} if you are also debugging the parent process) to attach to
4046 the child process (@pxref{Attach}). From that point on you can debug
4047 the child process just like any other process which you attached to.
4049 On some systems, @value{GDBN} provides support for debugging programs
4050 that create additional processes using the @code{fork} or @code{vfork}
4051 functions. On @sc{gnu}/Linux platforms, this feature is supported
4052 with kernel version 2.5.46 and later.
4054 The fork debugging commands are supported in native mode and when
4055 connected to @code{gdbserver} in either @code{target remote} mode or
4056 @code{target extended-remote} mode.
4058 By default, when a program forks, @value{GDBN} will continue to debug
4059 the parent process and the child process will run unimpeded.
4061 If you want to follow the child process instead of the parent process,
4062 use the command @w{@code{set follow-fork-mode}}.
4065 @kindex set follow-fork-mode
4066 @item set follow-fork-mode @var{mode}
4067 Set the debugger response to a program call of @code{fork} or
4068 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
4069 process. The @var{mode} argument can be:
4073 The original process is debugged after a fork. The child process runs
4074 unimpeded. This is the default.
4077 The new process is debugged after a fork. The parent process runs
4082 @kindex show follow-fork-mode
4083 @item show follow-fork-mode
4084 Display the current debugger response to a @code{fork} or @code{vfork} call.
4087 @cindex debugging multiple processes
4088 On Linux, if you want to debug both the parent and child processes, use the
4089 command @w{@code{set detach-on-fork}}.
4092 @kindex set detach-on-fork
4093 @item set detach-on-fork @var{mode}
4094 Tells gdb whether to detach one of the processes after a fork, or
4095 retain debugger control over them both.
4099 The child process (or parent process, depending on the value of
4100 @code{follow-fork-mode}) will be detached and allowed to run
4101 independently. This is the default.
4104 Both processes will be held under the control of @value{GDBN}.
4105 One process (child or parent, depending on the value of
4106 @code{follow-fork-mode}) is debugged as usual, while the other
4111 @kindex show detach-on-fork
4112 @item show detach-on-fork
4113 Show whether detach-on-fork mode is on/off.
4116 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4117 will retain control of all forked processes (including nested forks).
4118 You can list the forked processes under the control of @value{GDBN} by
4119 using the @w{@code{info inferiors}} command, and switch from one fork
4120 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4121 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4123 To quit debugging one of the forked processes, you can either detach
4124 from it by using the @w{@code{detach inferiors}} command (allowing it
4125 to run independently), or kill it using the @w{@code{kill inferiors}}
4126 command. @xref{Inferiors Connections and Programs, ,Debugging
4127 Multiple Inferiors Connections and Programs}.
4129 If you ask to debug a child process and a @code{vfork} is followed by an
4130 @code{exec}, @value{GDBN} executes the new target up to the first
4131 breakpoint in the new target. If you have a breakpoint set on
4132 @code{main} in your original program, the breakpoint will also be set on
4133 the child process's @code{main}.
4135 On some systems, when a child process is spawned by @code{vfork}, you
4136 cannot debug the child or parent until an @code{exec} call completes.
4138 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4139 call executes, the new target restarts. To restart the parent
4140 process, use the @code{file} command with the parent executable name
4141 as its argument. By default, after an @code{exec} call executes,
4142 @value{GDBN} discards the symbols of the previous executable image.
4143 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4147 @kindex set follow-exec-mode
4148 @item set follow-exec-mode @var{mode}
4150 Set debugger response to a program call of @code{exec}. An
4151 @code{exec} call replaces the program image of a process.
4153 @code{follow-exec-mode} can be:
4157 @value{GDBN} creates a new inferior and rebinds the process to this
4158 new inferior. The program the process was running before the
4159 @code{exec} call can be restarted afterwards by restarting the
4165 (@value{GDBP}) info inferiors
4166 (@value{GDBP}) info inferior
4167 Id Description Executable
4170 process 12020 is executing new program: prog2
4171 Program exited normally.
4172 (@value{GDBP}) info inferiors
4173 Id Description Executable
4179 @value{GDBN} keeps the process bound to the same inferior. The new
4180 executable image replaces the previous executable loaded in the
4181 inferior. Restarting the inferior after the @code{exec} call, with
4182 e.g., the @code{run} command, restarts the executable the process was
4183 running after the @code{exec} call. This is the default mode.
4188 (@value{GDBP}) info inferiors
4189 Id Description Executable
4192 process 12020 is executing new program: prog2
4193 Program exited normally.
4194 (@value{GDBP}) info inferiors
4195 Id Description Executable
4202 @code{follow-exec-mode} is supported in native mode and
4203 @code{target extended-remote} mode.
4205 You can use the @code{catch} command to make @value{GDBN} stop whenever
4206 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4207 Catchpoints, ,Setting Catchpoints}.
4209 @node Checkpoint/Restart
4210 @section Setting a @emph{Bookmark} to Return to Later
4215 @cindex snapshot of a process
4216 @cindex rewind program state
4218 On certain operating systems@footnote{Currently, only
4219 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4220 program's state, called a @dfn{checkpoint}, and come back to it
4223 Returning to a checkpoint effectively undoes everything that has
4224 happened in the program since the @code{checkpoint} was saved. This
4225 includes changes in memory, registers, and even (within some limits)
4226 system state. Effectively, it is like going back in time to the
4227 moment when the checkpoint was saved.
4229 Thus, if you're stepping thru a program and you think you're
4230 getting close to the point where things go wrong, you can save
4231 a checkpoint. Then, if you accidentally go too far and miss
4232 the critical statement, instead of having to restart your program
4233 from the beginning, you can just go back to the checkpoint and
4234 start again from there.
4236 This can be especially useful if it takes a lot of time or
4237 steps to reach the point where you think the bug occurs.
4239 To use the @code{checkpoint}/@code{restart} method of debugging:
4244 Save a snapshot of the debugged program's current execution state.
4245 The @code{checkpoint} command takes no arguments, but each checkpoint
4246 is assigned a small integer id, similar to a breakpoint id.
4248 @kindex info checkpoints
4249 @item info checkpoints
4250 List the checkpoints that have been saved in the current debugging
4251 session. For each checkpoint, the following information will be
4258 @item Source line, or label
4261 @kindex restart @var{checkpoint-id}
4262 @item restart @var{checkpoint-id}
4263 Restore the program state that was saved as checkpoint number
4264 @var{checkpoint-id}. All program variables, registers, stack frames
4265 etc.@: will be returned to the values that they had when the checkpoint
4266 was saved. In essence, gdb will ``wind back the clock'' to the point
4267 in time when the checkpoint was saved.
4269 Note that breakpoints, @value{GDBN} variables, command history etc.
4270 are not affected by restoring a checkpoint. In general, a checkpoint
4271 only restores things that reside in the program being debugged, not in
4274 @kindex delete checkpoint @var{checkpoint-id}
4275 @item delete checkpoint @var{checkpoint-id}
4276 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4280 Returning to a previously saved checkpoint will restore the user state
4281 of the program being debugged, plus a significant subset of the system
4282 (OS) state, including file pointers. It won't ``un-write'' data from
4283 a file, but it will rewind the file pointer to the previous location,
4284 so that the previously written data can be overwritten. For files
4285 opened in read mode, the pointer will also be restored so that the
4286 previously read data can be read again.
4288 Of course, characters that have been sent to a printer (or other
4289 external device) cannot be ``snatched back'', and characters received
4290 from eg.@: a serial device can be removed from internal program buffers,
4291 but they cannot be ``pushed back'' into the serial pipeline, ready to
4292 be received again. Similarly, the actual contents of files that have
4293 been changed cannot be restored (at this time).
4295 However, within those constraints, you actually can ``rewind'' your
4296 program to a previously saved point in time, and begin debugging it
4297 again --- and you can change the course of events so as to debug a
4298 different execution path this time.
4300 @cindex checkpoints and process id
4301 Finally, there is one bit of internal program state that will be
4302 different when you return to a checkpoint --- the program's process
4303 id. Each checkpoint will have a unique process id (or @var{pid}),
4304 and each will be different from the program's original @var{pid}.
4305 If your program has saved a local copy of its process id, this could
4306 potentially pose a problem.
4308 @subsection A Non-obvious Benefit of Using Checkpoints
4310 On some systems such as @sc{gnu}/Linux, address space randomization
4311 is performed on new processes for security reasons. This makes it
4312 difficult or impossible to set a breakpoint, or watchpoint, on an
4313 absolute address if you have to restart the program, since the
4314 absolute location of a symbol will change from one execution to the
4317 A checkpoint, however, is an @emph{identical} copy of a process.
4318 Therefore if you create a checkpoint at (eg.@:) the start of main,
4319 and simply return to that checkpoint instead of restarting the
4320 process, you can avoid the effects of address randomization and
4321 your symbols will all stay in the same place.
4324 @chapter Stopping and Continuing
4326 The principal purposes of using a debugger are so that you can stop your
4327 program before it terminates; or so that, if your program runs into
4328 trouble, you can investigate and find out why.
4330 Inside @value{GDBN}, your program may stop for any of several reasons,
4331 such as a signal, a breakpoint, or reaching a new line after a
4332 @value{GDBN} command such as @code{step}. You may then examine and
4333 change variables, set new breakpoints or remove old ones, and then
4334 continue execution. Usually, the messages shown by @value{GDBN} provide
4335 ample explanation of the status of your program---but you can also
4336 explicitly request this information at any time.
4339 @kindex info program
4341 Display information about the status of your program: whether it is
4342 running or not, what process it is, and why it stopped.
4346 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4347 * Continuing and Stepping:: Resuming execution
4348 * Skipping Over Functions and Files::
4349 Skipping over functions and files
4351 * Thread Stops:: Stopping and starting multi-thread programs
4355 @section Breakpoints, Watchpoints, and Catchpoints
4358 A @dfn{breakpoint} makes your program stop whenever a certain point in
4359 the program is reached. For each breakpoint, you can add conditions to
4360 control in finer detail whether your program stops. You can set
4361 breakpoints with the @code{break} command and its variants (@pxref{Set
4362 Breaks, ,Setting Breakpoints}), to specify the place where your program
4363 should stop by line number, function name or exact address in the
4366 On some systems, you can set breakpoints in shared libraries before
4367 the executable is run.
4370 @cindex data breakpoints
4371 @cindex memory tracing
4372 @cindex breakpoint on memory address
4373 @cindex breakpoint on variable modification
4374 A @dfn{watchpoint} is a special breakpoint that stops your program
4375 when the value of an expression changes. The expression may be a value
4376 of a variable, or it could involve values of one or more variables
4377 combined by operators, such as @samp{a + b}. This is sometimes called
4378 @dfn{data breakpoints}. You must use a different command to set
4379 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4380 from that, you can manage a watchpoint like any other breakpoint: you
4381 enable, disable, and delete both breakpoints and watchpoints using the
4384 You can arrange to have values from your program displayed automatically
4385 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4389 @cindex breakpoint on events
4390 A @dfn{catchpoint} is another special breakpoint that stops your program
4391 when a certain kind of event occurs, such as the throwing of a C@t{++}
4392 exception or the loading of a library. As with watchpoints, you use a
4393 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4394 Catchpoints}), but aside from that, you can manage a catchpoint like any
4395 other breakpoint. (To stop when your program receives a signal, use the
4396 @code{handle} command; see @ref{Signals, ,Signals}.)
4398 @cindex breakpoint numbers
4399 @cindex numbers for breakpoints
4400 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4401 catchpoint when you create it; these numbers are successive integers
4402 starting with one. In many of the commands for controlling various
4403 features of breakpoints you use the breakpoint number to say which
4404 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4405 @dfn{disabled}; if disabled, it has no effect on your program until you
4408 @cindex breakpoint ranges
4409 @cindex breakpoint lists
4410 @cindex ranges of breakpoints
4411 @cindex lists of breakpoints
4412 Some @value{GDBN} commands accept a space-separated list of breakpoints
4413 on which to operate. A list element can be either a single breakpoint number,
4414 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4415 When a breakpoint list is given to a command, all breakpoints in that list
4419 * Set Breaks:: Setting breakpoints
4420 * Set Watchpoints:: Setting watchpoints
4421 * Set Catchpoints:: Setting catchpoints
4422 * Delete Breaks:: Deleting breakpoints
4423 * Disabling:: Disabling breakpoints
4424 * Conditions:: Break conditions
4425 * Break Commands:: Breakpoint command lists
4426 * Dynamic Printf:: Dynamic printf
4427 * Save Breakpoints:: How to save breakpoints in a file
4428 * Static Probe Points:: Listing static probe points
4429 * Error in Breakpoints:: ``Cannot insert breakpoints''
4430 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4434 @subsection Setting Breakpoints
4436 @c FIXME LMB what does GDB do if no code on line of breakpt?
4437 @c consider in particular declaration with/without initialization.
4439 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4442 @kindex b @r{(@code{break})}
4443 @vindex $bpnum@r{, convenience variable}
4444 @cindex latest breakpoint
4445 Breakpoints are set with the @code{break} command (abbreviated
4446 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4447 number of the breakpoint you've set most recently:
4450 Breakpoint 1 at 0x11c6: file zeoes.c, line 24.
4455 A breakpoint may be mapped to multiple code locations for example with
4456 inlined functions, Ada generics, C@t{++} templates or overloaded function names.
4457 @value{GDBN} then indicates the number of code locations in the breakpoint
4461 Breakpoint 2 at 0x1179: some_func. (3 locations)
4467 @vindex $_hit_bpnum@r{, convenience variable}
4468 @vindex $_hit_locno@r{, convenience variable}
4469 When your program stops on a breakpoint, the convenience variables
4470 @samp{$_hit_bpnum} and @samp{$_hit_locno} are respectively set to the number of
4471 the encountered breakpoint and the number of the breakpoint's code location:
4473 Thread 1 "zeoes" hit Breakpoint 2.1, some_func () at zeoes.c:8
4474 8 printf("some func\n");
4482 Note that @samp{$_hit_bpnum} and @samp{$bpnum} are not equivalent:
4483 @samp{$_hit_bpnum} is set to the breakpoint number @b{last hit}, while
4484 @samp{$bpnum} is set to the breakpoint number @b{last set}.
4487 If the encountered breakpoint has only one code location, @samp{$_hit_locno}
4490 Breakpoint 1, main (argc=1, argv=0x7fffffffe018) at zeoes.c:24
4499 The @samp{$_hit_bpnum} and @samp{$_hit_locno} variables can typically be used
4500 in a breakpoint command list.
4501 (@pxref{Break Commands, ,Breakpoint Command Lists}). For example, as
4502 part of the breakpoint command list, you can disable completely the
4503 encountered breakpoint using @kbd{disable $_hit_bpnum} or disable the
4504 specific encountered breakpoint location using
4505 @kbd{disable $_hit_bpnum.$_hit_locno}.
4506 If a breakpoint has only one location, @samp{$_hit_locno} is set to 1
4507 and the commands @kbd{disable $_hit_bpnum} and
4508 @kbd{disable $_hit_bpnum.$_hit_locno} both disable the breakpoint.
4510 You can also define aliases to easily disable the last hit location or
4511 last hit breakpoint:
4513 (gdb) alias lld = disable $_hit_bpnum.$_hit_locno
4514 (gdb) alias lbd = disable $_hit_bpnum
4518 @item break @var{locspec}
4519 Set a breakpoint at all the code locations in your program that result
4520 from resolving the given @var{locspec}. @var{locspec} can specify a
4521 function name, a line number, an address of an instruction, and more.
4522 @xref{Location Specifications}, for the various forms of
4523 @var{locspec}. The breakpoint will stop your program just before it
4524 executes the instruction at the address of any of the breakpoint's
4527 When using source languages that permit overloading of symbols, such
4528 as C@t{++}, a function name may refer to more than one symbol, and
4529 thus more than one place to break. @xref{Ambiguous
4530 Expressions,,Ambiguous Expressions}, for a discussion of that
4533 It is also possible to insert a breakpoint that will stop the program
4534 only if a specific thread (@pxref{Thread-Specific Breakpoints}),
4535 specific inferior (@pxref{Inferior-Specific Breakpoints}), or a
4536 specific task (@pxref{Ada Tasks}) hits that breakpoint.
4539 When called without any arguments, @code{break} sets a breakpoint at
4540 the next instruction to be executed in the selected stack frame
4541 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4542 innermost, this makes your program stop as soon as control
4543 returns to that frame. This is similar to the effect of a
4544 @code{finish} command in the frame inside the selected frame---except
4545 that @code{finish} does not leave an active breakpoint. If you use
4546 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4547 the next time it reaches the current location; this may be useful
4550 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4551 least one instruction has been executed. If it did not do this, you
4552 would be unable to proceed past a breakpoint without first disabling the
4553 breakpoint. This rule applies whether or not the breakpoint already
4554 existed when your program stopped.
4556 @item break @dots{} if @var{cond}
4557 Set a breakpoint with condition @var{cond}; evaluate the expression
4558 @var{cond} each time the breakpoint is reached, and stop only if the
4559 value is nonzero---that is, if @var{cond} evaluates as true.
4560 @samp{@dots{}} stands for one of the possible arguments described
4561 above (or no argument) specifying where to break. @xref{Conditions,
4562 ,Break Conditions}, for more information on breakpoint conditions.
4564 The breakpoint may be mapped to multiple locations. If the breakpoint
4565 condition @var{cond} is invalid at some but not all of the locations,
4566 the locations for which the condition is invalid are disabled. For
4567 example, @value{GDBN} reports below that two of the three locations
4571 (@value{GDBP}) break func if a == 10
4572 warning: failed to validate condition at location 0x11ce, disabling:
4573 No symbol "a" in current context.
4574 warning: failed to validate condition at location 0x11b6, disabling:
4575 No symbol "a" in current context.
4576 Breakpoint 1 at 0x11b6: func. (3 locations)
4579 Locations that are disabled because of the condition are denoted by an
4580 uppercase @code{N} in the output of the @code{info breakpoints}
4584 (@value{GDBP}) info breakpoints
4585 Num Type Disp Enb Address What
4586 1 breakpoint keep y <MULTIPLE>
4587 stop only if a == 10
4588 1.1 N* 0x00000000000011b6 in ...
4589 1.2 y 0x00000000000011c2 in ...
4590 1.3 N* 0x00000000000011ce in ...
4591 (*): Breakpoint condition is invalid at this location.
4594 If the breakpoint condition @var{cond} is invalid in the context of
4595 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4596 define the breakpoint. For example, if variable @code{foo} is an
4600 (@value{GDBP}) break func if foo
4601 No symbol "foo" in current context.
4604 @item break @dots{} -force-condition if @var{cond}
4605 There may be cases where the condition @var{cond} is invalid at all
4606 the current locations, but the user knows that it will be valid at a
4607 future location; for example, because of a library load. In such
4608 cases, by using the @code{-force-condition} keyword before @samp{if},
4609 @value{GDBN} can be forced to define the breakpoint with the given
4610 condition expression instead of refusing it.
4613 (@value{GDBP}) break func -force-condition if foo
4614 warning: failed to validate condition at location 1, disabling:
4615 No symbol "foo" in current context.
4616 warning: failed to validate condition at location 2, disabling:
4617 No symbol "foo" in current context.
4618 warning: failed to validate condition at location 3, disabling:
4619 No symbol "foo" in current context.
4620 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4623 This causes all the present locations where the breakpoint would
4624 otherwise be inserted, to be disabled, as seen in the example above.
4625 However, if there exist locations at which the condition is valid, the
4626 @code{-force-condition} keyword has no effect.
4629 @item tbreak @var{args}
4630 Set a breakpoint enabled only for one stop. The @var{args} are the
4631 same as for the @code{break} command, and the breakpoint is set in the same
4632 way, but the breakpoint is automatically deleted after the first time your
4633 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4636 @cindex hardware breakpoints
4637 @item hbreak @var{args}
4638 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4639 @code{break} command and the breakpoint is set in the same way, but the
4640 breakpoint requires hardware support and some target hardware may not
4641 have this support. The main purpose of this is EPROM/ROM code
4642 debugging, so you can set a breakpoint at an instruction without
4643 changing the instruction. This can be used with the new trap-generation
4644 provided by SPARClite DSU and most x86-based targets. These targets
4645 will generate traps when a program accesses some data or instruction
4646 address that is assigned to the debug registers. However the hardware
4647 breakpoint registers can take a limited number of breakpoints. For
4648 example, on the DSU, only two data breakpoints can be set at a time, and
4649 @value{GDBN} will reject this command if more than two are used. Delete
4650 or disable unused hardware breakpoints before setting new ones
4651 (@pxref{Disabling, ,Disabling Breakpoints}).
4652 @xref{Conditions, ,Break Conditions}.
4653 For remote targets, you can restrict the number of hardware
4654 breakpoints @value{GDBN} will use, see @ref{set remote
4655 hardware-breakpoint-limit}.
4658 @item thbreak @var{args}
4659 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4660 are the same as for the @code{hbreak} command and the breakpoint is set in
4661 the same way. However, like the @code{tbreak} command,
4662 the breakpoint is automatically deleted after the
4663 first time your program stops there. Also, like the @code{hbreak}
4664 command, the breakpoint requires hardware support and some target hardware
4665 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4666 See also @ref{Conditions, ,Break Conditions}.
4669 @cindex regular expression
4670 @cindex breakpoints at functions matching a regexp
4671 @cindex set breakpoints in many functions
4672 @item rbreak @var{regex}
4673 Set breakpoints on all functions matching the regular expression
4674 @var{regex}. This command sets an unconditional breakpoint on all
4675 matches, printing a list of all breakpoints it set. Once these
4676 breakpoints are set, they are treated just like the breakpoints set with
4677 the @code{break} command. You can delete them, disable them, or make
4678 them conditional the same way as any other breakpoint.
4680 In programs using different languages, @value{GDBN} chooses the syntax
4681 to print the list of all breakpoints it sets according to the
4682 @samp{set language} value: using @samp{set language auto}
4683 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4684 language of the breakpoint's function, other values mean to use
4685 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4687 The syntax of the regular expression is the standard one used with tools
4688 like @file{grep}. Note that this is different from the syntax used by
4689 shells, so for instance @code{foo*} matches all functions that include
4690 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4691 @code{.*} leading and trailing the regular expression you supply, so to
4692 match only functions that begin with @code{foo}, use @code{^foo}.
4694 @cindex non-member C@t{++} functions, set breakpoint in
4695 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4696 breakpoints on overloaded functions that are not members of any special
4699 @cindex set breakpoints on all functions
4700 The @code{rbreak} command can be used to set breakpoints in
4701 @strong{all} the functions in a program, like this:
4704 (@value{GDBP}) rbreak .
4707 @item rbreak @var{file}:@var{regex}
4708 If @code{rbreak} is called with a filename qualification, it limits
4709 the search for functions matching the given regular expression to the
4710 specified @var{file}. This can be used, for example, to set breakpoints on
4711 every function in a given file:
4714 (@value{GDBP}) rbreak file.c:.
4717 The colon separating the filename qualifier from the regex may
4718 optionally be surrounded by spaces.
4720 @kindex info breakpoints
4721 @cindex @code{$_} and @code{info breakpoints}
4722 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4723 @itemx info break @r{[}@var{list}@dots{}@r{]}
4724 Print a table of all breakpoints, watchpoints, and catchpoints set and
4725 not deleted. Optional argument @var{n} means print information only
4726 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4727 For each breakpoint, following columns are printed:
4730 @item Breakpoint Numbers
4732 Breakpoint, watchpoint, or catchpoint.
4734 Whether the breakpoint is marked to be disabled or deleted when hit.
4735 @item Enabled or Disabled
4736 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4737 that are not enabled.
4739 Where the breakpoint is in your program, as a memory address. For a
4740 pending breakpoint whose address is not yet known, this field will
4741 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4742 library that has the symbol or line referred by breakpoint is loaded.
4743 See below for details. A breakpoint with several locations will
4744 have @samp{<MULTIPLE>} in this field---see below for details.
4746 Where the breakpoint is in the source for your program, as a file and
4747 line number. For a pending breakpoint, the original string passed to
4748 the breakpoint command will be listed as it cannot be resolved until
4749 the appropriate shared library is loaded in the future.
4753 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4754 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4755 @value{GDBN} on the host's side. If it is ``target'', then the condition
4756 is evaluated by the target. The @code{info break} command shows
4757 the condition on the line following the affected breakpoint, together with
4758 its condition evaluation mode in between parentheses.
4760 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4761 allowed to have a condition specified for it. The condition is not parsed for
4762 validity until a shared library is loaded that allows the pending
4763 breakpoint to resolve to a valid location.
4766 @code{info break} with a breakpoint
4767 number @var{n} as argument lists only that breakpoint. The
4768 convenience variable @code{$_} and the default examining-address for
4769 the @code{x} command are set to the address of the last breakpoint
4770 listed (@pxref{Memory, ,Examining Memory}).
4773 @code{info break} displays a count of the number of times the breakpoint
4774 has been hit. This is especially useful in conjunction with the
4775 @code{ignore} command. You can ignore a large number of breakpoint
4776 hits, look at the breakpoint info to see how many times the breakpoint
4777 was hit, and then run again, ignoring one less than that number. This
4778 will get you quickly to the last hit of that breakpoint.
4781 For a breakpoints with an enable count (xref) greater than 1,
4782 @code{info break} also displays that count.
4786 @value{GDBN} allows you to set any number of breakpoints at the same place in
4787 your program. There is nothing silly or meaningless about this. When
4788 the breakpoints are conditional, this is even useful
4789 (@pxref{Conditions, ,Break Conditions}).
4791 @cindex multiple locations, breakpoints
4792 @cindex breakpoints, multiple locations
4793 It is possible that a single logical breakpoint is set at several code
4794 locations in your program. @xref{Location Specifications}, for
4797 A breakpoint with multiple code locations is displayed in the
4798 breakpoint table using several rows---one header row, followed by one
4799 row for each code location. The header row has @samp{<MULTIPLE>} in
4800 the address column. Each code location row contains the actual
4801 address, source file, source line and function of its code location.
4802 The number column for a code location is of the form
4803 @var{breakpoint-number}.@var{location-number}.
4808 Num Type Disp Enb Address What
4809 1 breakpoint keep y <MULTIPLE>
4811 breakpoint already hit 1 time
4812 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4813 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4816 You cannot delete the individual locations from a breakpoint. However,
4817 each location can be individually enabled or disabled by passing
4818 @var{breakpoint-number}.@var{location-number} as argument to the
4819 @code{enable} and @code{disable} commands. It's also possible to
4820 @code{enable} and @code{disable} a range of @var{location-number}
4821 locations using a @var{breakpoint-number} and two @var{location-number}s,
4822 in increasing order, separated by a hyphen, like
4823 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4824 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4825 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4826 all of the locations that belong to that breakpoint.
4828 Locations that are enabled while their parent breakpoint is disabled
4829 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4830 column. For example:
4833 (@value{GDBP}) info breakpoints
4834 Num Type Disp Enb Address What
4835 1 breakpoint keep n <MULTIPLE>
4836 1.1 y- 0x00000000000011b6 in ...
4837 1.2 y- 0x00000000000011c2 in ...
4838 1.3 n 0x00000000000011ce in ...
4841 @cindex pending breakpoints
4842 It's quite common to have a breakpoint inside a shared library.
4843 Shared libraries can be loaded and unloaded explicitly,
4844 and possibly repeatedly, as the program is executed. To support
4845 this use case, @value{GDBN} updates breakpoint locations whenever
4846 any shared library is loaded or unloaded. Typically, you would
4847 set a breakpoint in a shared library at the beginning of your
4848 debugging session, when the library is not loaded, and when the
4849 symbols from the library are not available. When you try to set
4850 breakpoint, @value{GDBN} will ask you if you want to set
4851 a so called @dfn{pending breakpoint}---breakpoint whose address
4852 is not yet resolved.
4854 After the program is run, whenever a new shared library is loaded,
4855 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4856 shared library contains the symbol or line referred to by some
4857 pending breakpoint, that breakpoint is resolved and becomes an
4858 ordinary breakpoint. When a library is unloaded, all breakpoints
4859 that refer to its symbols or source lines become pending again.
4861 This logic works for breakpoints with multiple locations, too. For
4862 example, if you have a breakpoint in a C@t{++} template function, and
4863 a newly loaded shared library has an instantiation of that template,
4864 a new location is added to the list of locations for the breakpoint.
4866 Except for having unresolved address, pending breakpoints do not
4867 differ from regular breakpoints. You can set conditions or commands,
4868 enable and disable them and perform other breakpoint operations.
4870 @value{GDBN} provides some additional commands for controlling what
4871 happens when the @samp{break} command cannot resolve the location spec
4872 to any code location in your program (@pxref{Location
4875 @kindex set breakpoint pending
4876 @kindex show breakpoint pending
4878 @item set breakpoint pending auto
4879 This is the default behavior. When @value{GDBN} cannot resolve the
4880 location spec, it queries you whether a pending breakpoint should be
4883 @item set breakpoint pending on
4884 This indicates that when @value{GDBN} cannot resolve the location
4885 spec, it should create a pending breakpoint without confirmation.
4887 @item set breakpoint pending off
4888 This indicates that pending breakpoints are not to be created. If
4889 @value{GDBN} cannot resolve the location spec, it aborts the
4890 breakpoint creation with an error. This setting does not affect any
4891 pending breakpoints previously created.
4893 @item show breakpoint pending
4894 Show the current behavior setting for creating pending breakpoints.
4897 The settings above only affect the @code{break} command and its
4898 variants. Once a breakpoint is set, it will be automatically updated
4899 as shared libraries are loaded and unloaded.
4901 @cindex automatic hardware breakpoints
4902 For some targets, @value{GDBN} can automatically decide if hardware or
4903 software breakpoints should be used, depending on whether the
4904 breakpoint address is read-only or read-write. This applies to
4905 breakpoints set with the @code{break} command as well as to internal
4906 breakpoints set by commands like @code{next} and @code{finish}. For
4907 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4910 You can control this automatic behaviour with the following commands:
4912 @kindex set breakpoint auto-hw
4913 @kindex show breakpoint auto-hw
4915 @item set breakpoint auto-hw on
4916 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4917 will try to use the target memory map to decide if software or hardware
4918 breakpoint must be used.
4920 @item set breakpoint auto-hw off
4921 This indicates @value{GDBN} should not automatically select breakpoint
4922 type. If the target provides a memory map, @value{GDBN} will warn when
4923 trying to set software breakpoint at a read-only address.
4926 @value{GDBN} normally implements breakpoints by replacing the program code
4927 at the breakpoint address with a special instruction, which, when
4928 executed, given control to the debugger. By default, the program
4929 code is so modified only when the program is resumed. As soon as
4930 the program stops, @value{GDBN} restores the original instructions. This
4931 behaviour guards against leaving breakpoints inserted in the
4932 target should gdb abrubptly disconnect. However, with slow remote
4933 targets, inserting and removing breakpoint can reduce the performance.
4934 This behavior can be controlled with the following commands::
4936 @kindex set breakpoint always-inserted
4937 @kindex show breakpoint always-inserted
4939 @item set breakpoint always-inserted off
4940 All breakpoints, including newly added by the user, are inserted in
4941 the target only when the target is resumed. All breakpoints are
4942 removed from the target when it stops. This is the default mode.
4944 @item set breakpoint always-inserted on
4945 Causes all breakpoints to be inserted in the target at all times. If
4946 the user adds a new breakpoint, or changes an existing breakpoint, the
4947 breakpoints in the target are updated immediately. A breakpoint is
4948 removed from the target only when breakpoint itself is deleted.
4951 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4952 when a breakpoint breaks. If the condition is true, then the process being
4953 debugged stops, otherwise the process is resumed.
4955 If the target supports evaluating conditions on its end, @value{GDBN} may
4956 download the breakpoint, together with its conditions, to it.
4958 This feature can be controlled via the following commands:
4960 @kindex set breakpoint condition-evaluation
4961 @kindex show breakpoint condition-evaluation
4963 @item set breakpoint condition-evaluation host
4964 This option commands @value{GDBN} to evaluate the breakpoint
4965 conditions on the host's side. Unconditional breakpoints are sent to
4966 the target which in turn receives the triggers and reports them back to GDB
4967 for condition evaluation. This is the standard evaluation mode.
4969 @item set breakpoint condition-evaluation target
4970 This option commands @value{GDBN} to download breakpoint conditions
4971 to the target at the moment of their insertion. The target
4972 is responsible for evaluating the conditional expression and reporting
4973 breakpoint stop events back to @value{GDBN} whenever the condition
4974 is true. Due to limitations of target-side evaluation, some conditions
4975 cannot be evaluated there, e.g., conditions that depend on local data
4976 that is only known to the host. Examples include
4977 conditional expressions involving convenience variables, complex types
4978 that cannot be handled by the agent expression parser and expressions
4979 that are too long to be sent over to the target, specially when the
4980 target is a remote system. In these cases, the conditions will be
4981 evaluated by @value{GDBN}.
4983 @item set breakpoint condition-evaluation auto
4984 This is the default mode. If the target supports evaluating breakpoint
4985 conditions on its end, @value{GDBN} will download breakpoint conditions to
4986 the target (limitations mentioned previously apply). If the target does
4987 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4988 to evaluating all these conditions on the host's side.
4992 @cindex negative breakpoint numbers
4993 @cindex internal @value{GDBN} breakpoints
4994 @value{GDBN} itself sometimes sets breakpoints in your program for
4995 special purposes, such as proper handling of @code{longjmp} (in C
4996 programs). These internal breakpoints are assigned negative numbers,
4997 starting with @code{-1}; @samp{info breakpoints} does not display them.
4998 You can see these breakpoints with the @value{GDBN} maintenance command
4999 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
5002 @node Set Watchpoints
5003 @subsection Setting Watchpoints
5005 @cindex setting watchpoints
5006 You can use a watchpoint to stop execution whenever the value of an
5007 expression changes, without having to predict a particular place where
5008 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
5009 The expression may be as simple as the value of a single variable, or
5010 as complex as many variables combined by operators. Examples include:
5014 A reference to the value of a single variable.
5017 An address cast to an appropriate data type. For example,
5018 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
5019 address (assuming an @code{int} occupies 4 bytes).
5022 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
5023 expression can use any operators valid in the program's native
5024 language (@pxref{Languages}).
5027 You can set a watchpoint on an expression even if the expression can
5028 not be evaluated yet. For instance, you can set a watchpoint on
5029 @samp{*global_ptr} before @samp{global_ptr} is initialized.
5030 @value{GDBN} will stop when your program sets @samp{global_ptr} and
5031 the expression produces a valid value. If the expression becomes
5032 valid in some other way than changing a variable (e.g.@: if the memory
5033 pointed to by @samp{*global_ptr} becomes readable as the result of a
5034 @code{malloc} call), @value{GDBN} may not stop until the next time
5035 the expression changes.
5037 @cindex software watchpoints
5038 @cindex hardware watchpoints
5039 Depending on your system, watchpoints may be implemented in software or
5040 hardware. @value{GDBN} does software watchpointing by single-stepping your
5041 program and testing the variable's value each time, which is hundreds of
5042 times slower than normal execution. (But this may still be worth it, to
5043 catch errors where you have no clue what part of your program is the
5046 On some systems, such as most PowerPC or x86-based targets,
5047 @value{GDBN} includes support for hardware watchpoints, which do not
5048 slow down the running of your program.
5052 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
5053 Set a watchpoint for an expression. @value{GDBN} will break when the
5054 expression @var{expr} is written into by the program and its value
5055 changes. The simplest (and the most popular) use of this command is
5056 to watch the value of a single variable:
5059 (@value{GDBP}) watch foo
5062 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
5063 argument, @value{GDBN} breaks only when the thread identified by
5064 @var{thread-id} changes the value of @var{expr}. If any other threads
5065 change the value of @var{expr}, @value{GDBN} will not break. Note
5066 that watchpoints restricted to a single thread in this way only work
5067 with Hardware Watchpoints.
5069 Similarly, if the @code{task} argument is given, then the watchpoint
5070 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
5072 Ordinarily a watchpoint respects the scope of variables in @var{expr}
5073 (see below). The @code{-location} argument tells @value{GDBN} to
5074 instead watch the memory referred to by @var{expr}. In this case,
5075 @value{GDBN} will evaluate @var{expr}, take the address of the result,
5076 and watch the memory at that address. The type of the result is used
5077 to determine the size of the watched memory. If the expression's
5078 result does not have an address, then @value{GDBN} will print an
5081 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
5082 of masked watchpoints, if the current architecture supports this
5083 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
5084 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
5085 to an address to watch. The mask specifies that some bits of an address
5086 (the bits which are reset in the mask) should be ignored when matching
5087 the address accessed by the inferior against the watchpoint address.
5088 Thus, a masked watchpoint watches many addresses simultaneously---those
5089 addresses whose unmasked bits are identical to the unmasked bits in the
5090 watchpoint address. The @code{mask} argument implies @code{-location}.
5094 (@value{GDBP}) watch foo mask 0xffff00ff
5095 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
5099 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5100 Set a watchpoint that will break when the value of @var{expr} is read
5104 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5105 Set a watchpoint that will break when @var{expr} is either read from
5106 or written into by the program.
5108 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
5109 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
5110 This command prints a list of watchpoints, using the same format as
5111 @code{info break} (@pxref{Set Breaks}).
5114 If you watch for a change in a numerically entered address you need to
5115 dereference it, as the address itself is just a constant number which will
5116 never change. @value{GDBN} refuses to create a watchpoint that watches
5117 a never-changing value:
5120 (@value{GDBP}) watch 0x600850
5121 Cannot watch constant value 0x600850.
5122 (@value{GDBP}) watch *(int *) 0x600850
5123 Watchpoint 1: *(int *) 6293584
5126 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
5127 watchpoints execute very quickly, and the debugger reports a change in
5128 value at the exact instruction where the change occurs. If @value{GDBN}
5129 cannot set a hardware watchpoint, it sets a software watchpoint, which
5130 executes more slowly and reports the change in value at the next
5131 @emph{statement}, not the instruction, after the change occurs.
5133 @cindex use only software watchpoints
5134 You can force @value{GDBN} to use only software watchpoints with the
5135 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
5136 zero, @value{GDBN} will never try to use hardware watchpoints, even if
5137 the underlying system supports them. (Note that hardware-assisted
5138 watchpoints that were set @emph{before} setting
5139 @code{can-use-hw-watchpoints} to zero will still use the hardware
5140 mechanism of watching expression values.)
5143 @item set can-use-hw-watchpoints
5144 @kindex set can-use-hw-watchpoints
5145 Set whether or not to use hardware watchpoints.
5147 @item show can-use-hw-watchpoints
5148 @kindex show can-use-hw-watchpoints
5149 Show the current mode of using hardware watchpoints.
5152 For remote targets, you can restrict the number of hardware
5153 watchpoints @value{GDBN} will use, see @ref{set remote
5154 hardware-breakpoint-limit}.
5156 When you issue the @code{watch} command, @value{GDBN} reports
5159 Hardware watchpoint @var{num}: @var{expr}
5163 if it was able to set a hardware watchpoint.
5165 Currently, the @code{awatch} and @code{rwatch} commands can only set
5166 hardware watchpoints, because accesses to data that don't change the
5167 value of the watched expression cannot be detected without examining
5168 every instruction as it is being executed, and @value{GDBN} does not do
5169 that currently. If @value{GDBN} finds that it is unable to set a
5170 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5171 will print a message like this:
5174 Expression cannot be implemented with read/access watchpoint.
5177 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5178 data type of the watched expression is wider than what a hardware
5179 watchpoint on the target machine can handle. For example, some systems
5180 can only watch regions that are up to 4 bytes wide; on such systems you
5181 cannot set hardware watchpoints for an expression that yields a
5182 double-precision floating-point number (which is typically 8 bytes
5183 wide). As a work-around, it might be possible to break the large region
5184 into a series of smaller ones and watch them with separate watchpoints.
5186 If you set too many hardware watchpoints, @value{GDBN} might be unable
5187 to insert all of them when you resume the execution of your program.
5188 Since the precise number of active watchpoints is unknown until such
5189 time as the program is about to be resumed, @value{GDBN} might not be
5190 able to warn you about this when you set the watchpoints, and the
5191 warning will be printed only when the program is resumed:
5194 Hardware watchpoint @var{num}: Could not insert watchpoint
5198 If this happens, delete or disable some of the watchpoints.
5200 Watching complex expressions that reference many variables can also
5201 exhaust the resources available for hardware-assisted watchpoints.
5202 That's because @value{GDBN} needs to watch every variable in the
5203 expression with separately allocated resources.
5205 If you call a function interactively using @code{print} or @code{call},
5206 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5207 kind of breakpoint or the call completes.
5209 @value{GDBN} automatically deletes watchpoints that watch local
5210 (automatic) variables, or expressions that involve such variables, when
5211 they go out of scope, that is, when the execution leaves the block in
5212 which these variables were defined. In particular, when the program
5213 being debugged terminates, @emph{all} local variables go out of scope,
5214 and so only watchpoints that watch global variables remain set. If you
5215 rerun the program, you will need to set all such watchpoints again. One
5216 way of doing that would be to set a code breakpoint at the entry to the
5217 @code{main} function and when it breaks, set all the watchpoints.
5219 @cindex watchpoints and threads
5220 @cindex threads and watchpoints
5221 In multi-threaded programs, watchpoints will detect changes to the
5222 watched expression from every thread.
5225 @emph{Warning:} In multi-threaded programs, software watchpoints
5226 have only limited usefulness. If @value{GDBN} creates a software
5227 watchpoint, it can only watch the value of an expression @emph{in a
5228 single thread}. If you are confident that the expression can only
5229 change due to the current thread's activity (and if you are also
5230 confident that no other thread can become current), then you can use
5231 software watchpoints as usual. However, @value{GDBN} may not notice
5232 when a non-current thread's activity changes the expression. (Hardware
5233 watchpoints, in contrast, watch an expression in all threads.)
5236 @xref{set remote hardware-watchpoint-limit}.
5238 @node Set Catchpoints
5239 @subsection Setting Catchpoints
5240 @cindex catchpoints, setting
5241 @cindex exception handlers
5242 @cindex event handling
5244 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5245 kinds of program events, such as C@t{++} exceptions or the loading of a
5246 shared library. Use the @code{catch} command to set a catchpoint.
5250 @item catch @var{event}
5251 Stop when @var{event} occurs. The @var{event} can be any of the following:
5254 @item throw @r{[}@var{regexp}@r{]}
5255 @itemx rethrow @r{[}@var{regexp}@r{]}
5256 @itemx catch @r{[}@var{regexp}@r{]}
5258 @kindex catch rethrow
5260 @cindex stop on C@t{++} exceptions
5261 The throwing, re-throwing, or catching of a C@t{++} exception.
5263 If @var{regexp} is given, then only exceptions whose type matches the
5264 regular expression will be caught.
5266 @vindex $_exception@r{, convenience variable}
5267 The convenience variable @code{$_exception} is available at an
5268 exception-related catchpoint, on some systems. This holds the
5269 exception being thrown.
5271 There are currently some limitations to C@t{++} exception handling in
5276 The support for these commands is system-dependent. Currently, only
5277 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5281 The regular expression feature and the @code{$_exception} convenience
5282 variable rely on the presence of some SDT probes in @code{libstdc++}.
5283 If these probes are not present, then these features cannot be used.
5284 These probes were first available in the GCC 4.8 release, but whether
5285 or not they are available in your GCC also depends on how it was
5289 The @code{$_exception} convenience variable is only valid at the
5290 instruction at which an exception-related catchpoint is set.
5293 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5294 location in the system library which implements runtime exception
5295 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5296 (@pxref{Selection}) to get to your code.
5299 If you call a function interactively, @value{GDBN} normally returns
5300 control to you when the function has finished executing. If the call
5301 raises an exception, however, the call may bypass the mechanism that
5302 returns control to you and cause your program either to abort or to
5303 simply continue running until it hits a breakpoint, catches a signal
5304 that @value{GDBN} is listening for, or exits. This is the case even if
5305 you set a catchpoint for the exception; catchpoints on exceptions are
5306 disabled within interactive calls. @xref{Calling}, for information on
5307 controlling this with @code{set unwind-on-terminating-exception}.
5310 You cannot raise an exception interactively.
5313 You cannot install an exception handler interactively.
5316 @item exception @r{[}@var{name}@r{]}
5317 @kindex catch exception
5318 @cindex Ada exception catching
5319 @cindex catch Ada exceptions
5320 An Ada exception being raised. If an exception name is specified
5321 at the end of the command (eg @code{catch exception Program_Error}),
5322 the debugger will stop only when this specific exception is raised.
5323 Otherwise, the debugger stops execution when any Ada exception is raised.
5325 When inserting an exception catchpoint on a user-defined exception whose
5326 name is identical to one of the exceptions defined by the language, the
5327 fully qualified name must be used as the exception name. Otherwise,
5328 @value{GDBN} will assume that it should stop on the pre-defined exception
5329 rather than the user-defined one. For instance, assuming an exception
5330 called @code{Constraint_Error} is defined in package @code{Pck}, then
5331 the command to use to catch such exceptions is @kbd{catch exception
5332 Pck.Constraint_Error}.
5334 @vindex $_ada_exception@r{, convenience variable}
5335 The convenience variable @code{$_ada_exception} holds the address of
5336 the exception being thrown. This can be useful when setting a
5337 condition for such a catchpoint.
5339 @item exception unhandled
5340 @kindex catch exception unhandled
5341 An exception that was raised but is not handled by the program. The
5342 convenience variable @code{$_ada_exception} is set as for @code{catch
5345 @item handlers @r{[}@var{name}@r{]}
5346 @kindex catch handlers
5347 @cindex Ada exception handlers catching
5348 @cindex catch Ada exceptions when handled
5349 An Ada exception being handled. If an exception name is
5350 specified at the end of the command
5351 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5352 only when this specific exception is handled.
5353 Otherwise, the debugger stops execution when any Ada exception is handled.
5355 When inserting a handlers catchpoint on a user-defined
5356 exception whose name is identical to one of the exceptions
5357 defined by the language, the fully qualified name must be used
5358 as the exception name. Otherwise, @value{GDBN} will assume that it
5359 should stop on the pre-defined exception rather than the
5360 user-defined one. For instance, assuming an exception called
5361 @code{Constraint_Error} is defined in package @code{Pck}, then the
5362 command to use to catch such exceptions handling is
5363 @kbd{catch handlers Pck.Constraint_Error}.
5365 The convenience variable @code{$_ada_exception} is set as for
5366 @code{catch exception}.
5369 @kindex catch assert
5370 A failed Ada assertion. Note that the convenience variable
5371 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5375 @cindex break on fork/exec
5376 A call to @code{exec}.
5378 @anchor{catch syscall}
5380 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5381 @kindex catch syscall
5382 @cindex break on a system call.
5383 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5384 syscall is a mechanism for application programs to request a service
5385 from the operating system (OS) or one of the OS system services.
5386 @value{GDBN} can catch some or all of the syscalls issued by the
5387 debuggee, and show the related information for each syscall. If no
5388 argument is specified, calls to and returns from all system calls
5391 @var{name} can be any system call name that is valid for the
5392 underlying OS. Just what syscalls are valid depends on the OS. On
5393 GNU and Unix systems, you can find the full list of valid syscall
5394 names on @file{/usr/include/asm/unistd.h}.
5396 @c For MS-Windows, the syscall names and the corresponding numbers
5397 @c can be found, e.g., on this URL:
5398 @c http://www.metasploit.com/users/opcode/syscalls.html
5399 @c but we don't support Windows syscalls yet.
5401 Normally, @value{GDBN} knows in advance which syscalls are valid for
5402 each OS, so you can use the @value{GDBN} command-line completion
5403 facilities (@pxref{Completion,, command completion}) to list the
5406 You may also specify the system call numerically. A syscall's
5407 number is the value passed to the OS's syscall dispatcher to
5408 identify the requested service. When you specify the syscall by its
5409 name, @value{GDBN} uses its database of syscalls to convert the name
5410 into the corresponding numeric code, but using the number directly
5411 may be useful if @value{GDBN}'s database does not have the complete
5412 list of syscalls on your system (e.g., because @value{GDBN} lags
5413 behind the OS upgrades).
5415 You may specify a group of related syscalls to be caught at once using
5416 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5417 instance, on some platforms @value{GDBN} allows you to catch all
5418 network related syscalls, by passing the argument @code{group:network}
5419 to @code{catch syscall}. Note that not all syscall groups are
5420 available in every system. You can use the command completion
5421 facilities (@pxref{Completion,, command completion}) to list the
5422 syscall groups available on your environment.
5424 The example below illustrates how this command works if you don't provide
5428 (@value{GDBP}) catch syscall
5429 Catchpoint 1 (syscall)
5431 Starting program: /tmp/catch-syscall
5433 Catchpoint 1 (call to syscall 'close'), \
5434 0xffffe424 in __kernel_vsyscall ()
5438 Catchpoint 1 (returned from syscall 'close'), \
5439 0xffffe424 in __kernel_vsyscall ()
5443 Here is an example of catching a system call by name:
5446 (@value{GDBP}) catch syscall chroot
5447 Catchpoint 1 (syscall 'chroot' [61])
5449 Starting program: /tmp/catch-syscall
5451 Catchpoint 1 (call to syscall 'chroot'), \
5452 0xffffe424 in __kernel_vsyscall ()
5456 Catchpoint 1 (returned from syscall 'chroot'), \
5457 0xffffe424 in __kernel_vsyscall ()
5461 An example of specifying a system call numerically. In the case
5462 below, the syscall number has a corresponding entry in the XML
5463 file, so @value{GDBN} finds its name and prints it:
5466 (@value{GDBP}) catch syscall 252
5467 Catchpoint 1 (syscall(s) 'exit_group')
5469 Starting program: /tmp/catch-syscall
5471 Catchpoint 1 (call to syscall 'exit_group'), \
5472 0xffffe424 in __kernel_vsyscall ()
5476 Program exited normally.
5480 Here is an example of catching a syscall group:
5483 (@value{GDBP}) catch syscall group:process
5484 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5485 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5486 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5488 Starting program: /tmp/catch-syscall
5490 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5491 from /lib64/ld-linux-x86-64.so.2
5497 However, there can be situations when there is no corresponding name
5498 in XML file for that syscall number. In this case, @value{GDBN} prints
5499 a warning message saying that it was not able to find the syscall name,
5500 but the catchpoint will be set anyway. See the example below:
5503 (@value{GDBP}) catch syscall 764
5504 warning: The number '764' does not represent a known syscall.
5505 Catchpoint 2 (syscall 764)
5509 If you configure @value{GDBN} using the @samp{--without-expat} option,
5510 it will not be able to display syscall names. Also, if your
5511 architecture does not have an XML file describing its system calls,
5512 you will not be able to see the syscall names. It is important to
5513 notice that these two features are used for accessing the syscall
5514 name database. In either case, you will see a warning like this:
5517 (@value{GDBP}) catch syscall
5518 warning: Could not open "syscalls/i386-linux.xml"
5519 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5520 GDB will not be able to display syscall names.
5521 Catchpoint 1 (syscall)
5525 Of course, the file name will change depending on your architecture and system.
5527 Still using the example above, you can also try to catch a syscall by its
5528 number. In this case, you would see something like:
5531 (@value{GDBP}) catch syscall 252
5532 Catchpoint 1 (syscall(s) 252)
5535 Again, in this case @value{GDBN} would not be able to display syscall's names.
5539 A call to @code{fork}.
5543 A call to @code{vfork}.
5545 @item load @r{[}@var{regexp}@r{]}
5546 @itemx unload @r{[}@var{regexp}@r{]}
5548 @kindex catch unload
5549 The loading or unloading of a shared library. If @var{regexp} is
5550 given, then the catchpoint will stop only if the regular expression
5551 matches one of the affected libraries.
5553 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5554 @kindex catch signal
5555 The delivery of a signal.
5557 With no arguments, this catchpoint will catch any signal that is not
5558 used internally by @value{GDBN}, specifically, all signals except
5559 @samp{SIGTRAP} and @samp{SIGINT}.
5561 With the argument @samp{all}, all signals, including those used by
5562 @value{GDBN}, will be caught. This argument cannot be used with other
5565 Otherwise, the arguments are a list of signal names as given to
5566 @code{handle} (@pxref{Signals}). Only signals specified in this list
5569 One reason that @code{catch signal} can be more useful than
5570 @code{handle} is that you can attach commands and conditions to the
5573 When a signal is caught by a catchpoint, the signal's @code{stop} and
5574 @code{print} settings, as specified by @code{handle}, are ignored.
5575 However, whether the signal is still delivered to the inferior depends
5576 on the @code{pass} setting; this can be changed in the catchpoint's
5581 @item tcatch @var{event}
5583 Set a catchpoint that is enabled only for one stop. The catchpoint is
5584 automatically deleted after the first time the event is caught.
5588 Use the @code{info break} command to list the current catchpoints.
5592 @subsection Deleting Breakpoints
5594 @cindex clearing breakpoints, watchpoints, catchpoints
5595 @cindex deleting breakpoints, watchpoints, catchpoints
5596 It is often necessary to eliminate a breakpoint, watchpoint, or
5597 catchpoint once it has done its job and you no longer want your program
5598 to stop there. This is called @dfn{deleting} the breakpoint. A
5599 breakpoint that has been deleted no longer exists; it is forgotten.
5601 With the @code{clear} command you can delete breakpoints according to
5602 where they are in your program. With the @code{delete} command you can
5603 delete individual breakpoints, watchpoints, or catchpoints by specifying
5604 their breakpoint numbers.
5606 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5607 automatically ignores breakpoints on the first instruction to be executed
5608 when you continue execution without changing the execution address.
5613 Delete any breakpoints at the next instruction to be executed in the
5614 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5615 the innermost frame is selected, this is a good way to delete a
5616 breakpoint where your program just stopped.
5618 @item clear @var{locspec}
5619 Delete any breakpoint with a code location that corresponds to
5620 @var{locspec}. @xref{Location Specifications}, for the various forms
5621 of @var{locspec}. Which code locations correspond to @var{locspec}
5622 depends on the form used in the location specification @var{locspec}:
5626 @itemx @var{filename}:@var{linenum}
5627 @itemx -line @var{linenum}
5628 @itemx -source @var{filename} -line @var{linenum}
5629 If @var{locspec} specifies a line number, with or without a file name,
5630 the command deletes any breakpoint with a code location that is at or
5631 within the specified line @var{linenum} in files that match the
5632 specified @var{filename}. If @var{filename} is omitted, it defaults
5633 to the current source file.
5635 @item *@var{address}
5636 If @var{locspec} specifies an address, the command deletes any
5637 breakpoint with a code location that is at the given @var{address}.
5639 @item @var{function}
5640 @itemx -function @var{function}
5641 If @var{locspec} specifies a function, the command deletes any
5642 breakpoint with a code location that is at the entry to any function
5643 whose name matches @var{function}.
5646 Ambiguity in names of files and functions can be resolved as described
5647 in @ref{Location Specifications}.
5649 @cindex delete breakpoints
5651 @kindex d @r{(@code{delete})}
5652 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5653 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5654 list specified as argument. If no argument is specified, delete all
5655 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5656 confirm off}). You can abbreviate this command as @code{d}.
5660 @subsection Disabling Breakpoints
5662 @cindex enable/disable a breakpoint
5663 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5664 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5665 it had been deleted, but remembers the information on the breakpoint so
5666 that you can @dfn{enable} it again later.
5668 You disable and enable breakpoints, watchpoints, and catchpoints with
5669 the @code{enable} and @code{disable} commands, optionally specifying
5670 one or more breakpoint numbers as arguments. Use @code{info break} to
5671 print a list of all breakpoints, watchpoints, and catchpoints if you
5672 do not know which numbers to use.
5674 Disabling and enabling a breakpoint that has multiple locations
5675 affects all of its locations.
5677 A breakpoint, watchpoint, or catchpoint can have any of several
5678 different states of enablement:
5682 Enabled. The breakpoint stops your program. A breakpoint set
5683 with the @code{break} command starts out in this state.
5685 Disabled. The breakpoint has no effect on your program.
5687 Enabled once. The breakpoint stops your program, but then becomes
5690 Enabled for a count. The breakpoint stops your program for the next
5691 N times, then becomes disabled.
5693 Enabled for deletion. The breakpoint stops your program, but
5694 immediately after it does so it is deleted permanently. A breakpoint
5695 set with the @code{tbreak} command starts out in this state.
5698 You can use the following commands to enable or disable breakpoints,
5699 watchpoints, and catchpoints:
5703 @kindex dis @r{(@code{disable})}
5704 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5705 Disable the specified breakpoints---or all breakpoints, if none are
5706 listed. A disabled breakpoint has no effect but is not forgotten. All
5707 options such as ignore-counts, conditions and commands are remembered in
5708 case the breakpoint is enabled again later. You may abbreviate
5709 @code{disable} as @code{dis}.
5712 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5713 Enable the specified breakpoints (or all defined breakpoints). They
5714 become effective once again in stopping your program.
5716 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5717 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5718 of these breakpoints immediately after stopping your program.
5720 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5721 Enable the specified breakpoints temporarily. @value{GDBN} records
5722 @var{count} with each of the specified breakpoints, and decrements a
5723 breakpoint's count when it is hit. When any count reaches 0,
5724 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5725 count (@pxref{Conditions, ,Break Conditions}), that will be
5726 decremented to 0 before @var{count} is affected.
5728 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5729 Enable the specified breakpoints to work once, then die. @value{GDBN}
5730 deletes any of these breakpoints as soon as your program stops there.
5731 Breakpoints set by the @code{tbreak} command start out in this state.
5734 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5735 @c confusing: tbreak is also initially enabled.
5736 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5737 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5738 subsequently, they become disabled or enabled only when you use one of
5739 the commands above. (The command @code{until} can set and delete a
5740 breakpoint of its own, but it does not change the state of your other
5741 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5745 @subsection Break Conditions
5746 @cindex conditional breakpoints
5747 @cindex breakpoint conditions
5749 @c FIXME what is scope of break condition expr? Context where wanted?
5750 @c in particular for a watchpoint?
5751 The simplest sort of breakpoint breaks every time your program reaches a
5752 specified place. You can also specify a @dfn{condition} for a
5753 breakpoint. A condition is just a Boolean expression in your
5754 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5755 a condition evaluates the expression each time your program reaches it,
5756 and your program stops only if the condition is @emph{true}.
5758 This is the converse of using assertions for program validation; in that
5759 situation, you want to stop when the assertion is violated---that is,
5760 when the condition is false. In C, if you want to test an assertion expressed
5761 by the condition @var{assert}, you should set the condition
5762 @samp{! @var{assert}} on the appropriate breakpoint.
5764 Conditions are also accepted for watchpoints; you may not need them,
5765 since a watchpoint is inspecting the value of an expression anyhow---but
5766 it might be simpler, say, to just set a watchpoint on a variable name,
5767 and specify a condition that tests whether the new value is an interesting
5770 Break conditions can have side effects, and may even call functions in
5771 your program. This can be useful, for example, to activate functions
5772 that log program progress, or to use your own print functions to
5773 format special data structures. The effects are completely predictable
5774 unless there is another enabled breakpoint at the same address. (In
5775 that case, @value{GDBN} might see the other breakpoint first and stop your
5776 program without checking the condition of this one.) Note that
5777 breakpoint commands are usually more convenient and flexible than break
5779 purpose of performing side effects when a breakpoint is reached
5780 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5782 Breakpoint conditions can also be evaluated on the target's side if
5783 the target supports it. Instead of evaluating the conditions locally,
5784 @value{GDBN} encodes the expression into an agent expression
5785 (@pxref{Agent Expressions}) suitable for execution on the target,
5786 independently of @value{GDBN}. Global variables become raw memory
5787 locations, locals become stack accesses, and so forth.
5789 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5790 when its condition evaluates to true. This mechanism may provide faster
5791 response times depending on the performance characteristics of the target
5792 since it does not need to keep @value{GDBN} informed about
5793 every breakpoint trigger, even those with false conditions.
5795 Break conditions can be specified when a breakpoint is set, by using
5796 @samp{if} in the arguments to the @code{break} command. @xref{Set
5797 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5798 with the @code{condition} command.
5800 You can also use the @code{if} keyword with the @code{watch} command.
5801 The @code{catch} command does not recognize the @code{if} keyword;
5802 @code{condition} is the only way to impose a further condition on a
5807 @item condition @var{bnum} @var{expression}
5808 Specify @var{expression} as the break condition for breakpoint,
5809 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5810 breakpoint @var{bnum} stops your program only if the value of
5811 @var{expression} is true (nonzero, in C). When you use
5812 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5813 syntactic correctness, and to determine whether symbols in it have
5814 referents in the context of your breakpoint. If @var{expression} uses
5815 symbols not referenced in the context of the breakpoint, @value{GDBN}
5816 prints an error message:
5819 No symbol "foo" in current context.
5824 not actually evaluate @var{expression} at the time the @code{condition}
5825 command (or a command that sets a breakpoint with a condition, like
5826 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5828 @item condition -force @var{bnum} @var{expression}
5829 When the @code{-force} flag is used, define the condition even if
5830 @var{expression} is invalid at all the current locations of breakpoint
5831 @var{bnum}. This is similar to the @code{-force-condition} option
5832 of the @code{break} command.
5834 @item condition @var{bnum}
5835 Remove the condition from breakpoint number @var{bnum}. It becomes
5836 an ordinary unconditional breakpoint.
5839 @cindex ignore count (of breakpoint)
5840 A special case of a breakpoint condition is to stop only when the
5841 breakpoint has been reached a certain number of times. This is so
5842 useful that there is a special way to do it, using the @dfn{ignore
5843 count} of the breakpoint. Every breakpoint has an ignore count, which
5844 is an integer. Most of the time, the ignore count is zero, and
5845 therefore has no effect. But if your program reaches a breakpoint whose
5846 ignore count is positive, then instead of stopping, it just decrements
5847 the ignore count by one and continues. As a result, if the ignore count
5848 value is @var{n}, the breakpoint does not stop the next @var{n} times
5849 your program reaches it.
5853 @item ignore @var{bnum} @var{count}
5854 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5855 The next @var{count} times the breakpoint is reached, your program's
5856 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5859 To make the breakpoint stop the next time it is reached, specify
5862 When you use @code{continue} to resume execution of your program from a
5863 breakpoint, you can specify an ignore count directly as an argument to
5864 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5865 Stepping,,Continuing and Stepping}.
5867 If a breakpoint has a positive ignore count and a condition, the
5868 condition is not checked. Once the ignore count reaches zero,
5869 @value{GDBN} resumes checking the condition.
5871 You could achieve the effect of the ignore count with a condition such
5872 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5873 is decremented each time. @xref{Convenience Vars, ,Convenience
5877 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5880 @node Break Commands
5881 @subsection Breakpoint Command Lists
5883 @cindex breakpoint commands
5884 You can give any breakpoint (or watchpoint or catchpoint) a series of
5885 commands to execute when your program stops due to that breakpoint. For
5886 example, you might want to print the values of certain expressions, or
5887 enable other breakpoints.
5891 @kindex end@r{ (breakpoint commands)}
5892 @item commands @r{[}@var{list}@dots{}@r{]}
5893 @itemx @dots{} @var{command-list} @dots{}
5895 Specify a list of commands for the given breakpoints. The commands
5896 themselves appear on the following lines. Type a line containing just
5897 @code{end} to terminate the commands.
5899 To remove all commands from a breakpoint, type @code{commands} and
5900 follow it immediately with @code{end}; that is, give no commands.
5902 With no argument, @code{commands} refers to the last breakpoint,
5903 watchpoint, or catchpoint set (not to the breakpoint most recently
5904 encountered). If the most recent breakpoints were set with a single
5905 command, then the @code{commands} will apply to all the breakpoints
5906 set by that command. This applies to breakpoints set by
5907 @code{rbreak}, and also applies when a single @code{break} command
5908 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5912 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5913 disabled within a @var{command-list}.
5915 Inside a command list, you can use the command
5916 @kbd{disable $_hit_bpnum} to disable the encountered breakpoint.
5918 If your breakpoint has several code locations, the command
5919 @kbd{disable $_hit_bpnum.$_hit_locno} will disable the specific breakpoint
5920 code location encountered. If the breakpoint has only one location,
5921 this command will disable the encountered breakpoint.
5923 You can use breakpoint commands to start your program up again. Simply
5924 use the @code{continue} command, or @code{step}, or any other command
5925 that resumes execution.
5927 Any other commands in the command list, after a command that resumes
5928 execution, are ignored. This is because any time you resume execution
5929 (even with a simple @code{next} or @code{step}), you may encounter
5930 another breakpoint---which could have its own command list, leading to
5931 ambiguities about which list to execute.
5934 If the first command you specify in a command list is @code{silent}, the
5935 usual message about stopping at a breakpoint is not printed. This may
5936 be desirable for breakpoints that are to print a specific message and
5937 then continue. If none of the remaining commands print anything, you
5938 see no sign that the breakpoint was reached. @code{silent} is
5939 meaningful only at the beginning of a breakpoint command list.
5941 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5942 print precisely controlled output, and are often useful in silent
5943 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5945 For example, here is how you could use breakpoint commands to print the
5946 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5952 printf "x is %d\n",x
5957 One application for breakpoint commands is to compensate for one bug so
5958 you can test for another. Put a breakpoint just after the erroneous line
5959 of code, give it a condition to detect the case in which something
5960 erroneous has been done, and give it commands to assign correct values
5961 to any variables that need them. End with the @code{continue} command
5962 so that your program does not stop, and start with the @code{silent}
5963 command so that no output is produced. Here is an example:
5974 @node Dynamic Printf
5975 @subsection Dynamic Printf
5977 @cindex dynamic printf
5979 The dynamic printf command @code{dprintf} combines a breakpoint with
5980 formatted printing of your program's data to give you the effect of
5981 inserting @code{printf} calls into your program on-the-fly, without
5982 having to recompile it.
5984 In its most basic form, the output goes to the GDB console. However,
5985 you can set the variable @code{dprintf-style} for alternate handling.
5986 For instance, you can ask to format the output by calling your
5987 program's @code{printf} function. This has the advantage that the
5988 characters go to the program's output device, so they can recorded in
5989 redirects to files and so forth.
5991 If you are doing remote debugging with a stub or agent, you can also
5992 ask to have the printf handled by the remote agent. In addition to
5993 ensuring that the output goes to the remote program's device along
5994 with any other output the program might produce, you can also ask that
5995 the dprintf remain active even after disconnecting from the remote
5996 target. Using the stub/agent is also more efficient, as it can do
5997 everything without needing to communicate with @value{GDBN}.
6001 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
6002 Whenever execution reaches a code location that results from resolving
6003 @var{locspec}, print the values of one or more @var{expressions} under
6004 the control of the string @var{template}. To print several values,
6005 separate them with commas.
6007 @item set dprintf-style @var{style}
6008 Set the dprintf output to be handled in one of several different
6009 styles enumerated below. A change of style affects all existing
6010 dynamic printfs immediately. (If you need individual control over the
6011 print commands, simply define normal breakpoints with
6012 explicitly-supplied command lists.)
6016 @kindex dprintf-style gdb
6017 Handle the output using the @value{GDBN} @code{printf} command. When
6018 using this style, it is possible to use the @samp{%V} format specifier
6019 (@pxref{%V Format Specifier}).
6022 @kindex dprintf-style call
6023 Handle the output by calling a function in your program (normally
6024 @code{printf}). When using this style the supported format specifiers
6025 depend entirely on the function being called.
6027 Most of @value{GDBN}'s format specifiers align with those supported by
6028 the @code{printf} function, however, @value{GDBN}'s @samp{%V} format
6029 specifier extension is not supported by @code{printf}. When using
6030 @samp{call} style dprintf, care should be taken to ensure that only
6031 format specifiers supported by the output function are used, otherwise
6032 the results will be undefined.
6035 @kindex dprintf-style agent
6036 Have the remote debugging agent (such as @code{gdbserver}) handle the
6037 output itself. This style is only available for agents that support
6038 running commands on the target. This style does not support the
6039 @samp{%V} format specifier.
6042 @item set dprintf-function @var{function}
6043 Set the function to call if the dprintf style is @code{call}. By
6044 default its value is @code{printf}. You may set it to any expression
6045 that @value{GDBN} can evaluate to a function, as per the @code{call}
6048 @item set dprintf-channel @var{channel}
6049 Set a ``channel'' for dprintf. If set to a non-empty value,
6050 @value{GDBN} will evaluate it as an expression and pass the result as
6051 a first argument to the @code{dprintf-function}, in the manner of
6052 @code{fprintf} and similar functions. Otherwise, the dprintf format
6053 string will be the first argument, in the manner of @code{printf}.
6055 As an example, if you wanted @code{dprintf} output to go to a logfile
6056 that is a standard I/O stream assigned to the variable @code{mylog},
6057 you could do the following:
6060 (@value{GDBP}) set dprintf-style call
6061 (@value{GDBP}) set dprintf-function fprintf
6062 (@value{GDBP}) set dprintf-channel mylog
6063 (@value{GDBP}) dprintf 25,"at line 25, glob=%d\n",glob
6064 Dprintf 1 at 0x123456: file main.c, line 25.
6065 (@value{GDBP}) info break
6066 1 dprintf keep y 0x00123456 in main at main.c:25
6067 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
6072 Note that the @code{info break} displays the dynamic printf commands
6073 as normal breakpoint commands; you can thus easily see the effect of
6074 the variable settings.
6076 @item set disconnected-dprintf on
6077 @itemx set disconnected-dprintf off
6078 @kindex set disconnected-dprintf
6079 Choose whether @code{dprintf} commands should continue to run if
6080 @value{GDBN} has disconnected from the target. This only applies
6081 if the @code{dprintf-style} is @code{agent}.
6083 @item show disconnected-dprintf off
6084 @kindex show disconnected-dprintf
6085 Show the current choice for disconnected @code{dprintf}.
6089 @value{GDBN} does not check the validity of function and channel,
6090 relying on you to supply values that are meaningful for the contexts
6091 in which they are being used. For instance, the function and channel
6092 may be the values of local variables, but if that is the case, then
6093 all enabled dynamic prints must be at locations within the scope of
6094 those locals. If evaluation fails, @value{GDBN} will report an error.
6096 @node Save Breakpoints
6097 @subsection How to save breakpoints to a file
6099 To save breakpoint definitions to a file use the @w{@code{save
6100 breakpoints}} command.
6103 @kindex save breakpoints
6104 @cindex save breakpoints to a file for future sessions
6105 @item save breakpoints [@var{filename}]
6106 This command saves all current breakpoint definitions together with
6107 their commands and ignore counts, into a file @file{@var{filename}}
6108 suitable for use in a later debugging session. This includes all
6109 types of breakpoints (breakpoints, watchpoints, catchpoints,
6110 tracepoints). To read the saved breakpoint definitions, use the
6111 @code{source} command (@pxref{Command Files}). Note that watchpoints
6112 with expressions involving local variables may fail to be recreated
6113 because it may not be possible to access the context where the
6114 watchpoint is valid anymore. Because the saved breakpoint definitions
6115 are simply a sequence of @value{GDBN} commands that recreate the
6116 breakpoints, you can edit the file in your favorite editing program,
6117 and remove the breakpoint definitions you're not interested in, or
6118 that can no longer be recreated.
6121 @node Static Probe Points
6122 @subsection Static Probe Points
6124 @cindex static probe point, SystemTap
6125 @cindex static probe point, DTrace
6126 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
6127 for Statically Defined Tracing, and the probes are designed to have a tiny
6128 runtime code and data footprint, and no dynamic relocations.
6130 Currently, the following types of probes are supported on
6131 ELF-compatible systems:
6135 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
6136 @acronym{SDT} probes@footnote{See
6137 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
6138 for more information on how to add @code{SystemTap} @acronym{SDT}
6139 probes in your applications.}. @code{SystemTap} probes are usable
6140 from assembly, C and C@t{++} languages@footnote{See
6141 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
6142 for a good reference on how the @acronym{SDT} probes are implemented.}.
6144 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
6145 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
6149 @cindex semaphores on static probe points
6150 Some @code{SystemTap} probes have an associated semaphore variable;
6151 for instance, this happens automatically if you defined your probe
6152 using a DTrace-style @file{.d} file. If your probe has a semaphore,
6153 @value{GDBN} will automatically enable it when you specify a
6154 breakpoint using the @samp{-probe-stap} notation. But, if you put a
6155 breakpoint at a probe's location by some other method (e.g.,
6156 @code{break file:line}), then @value{GDBN} will not automatically set
6157 the semaphore. @code{DTrace} probes do not support semaphores.
6159 You can examine the available static static probes using @code{info
6160 probes}, with optional arguments:
6164 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6165 If given, @var{type} is either @code{stap} for listing
6166 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
6167 probes. If omitted all probes are listed regardless of their types.
6169 If given, @var{provider} is a regular expression used to match against provider
6170 names when selecting which probes to list. If omitted, probes by all
6171 probes from all providers are listed.
6173 If given, @var{name} is a regular expression to match against probe names
6174 when selecting which probes to list. If omitted, probe names are not
6175 considered when deciding whether to display them.
6177 If given, @var{objfile} is a regular expression used to select which
6178 object files (executable or shared libraries) to examine. If not
6179 given, all object files are considered.
6181 @item info probes all
6182 List the available static probes, from all types.
6185 @cindex enabling and disabling probes
6186 Some probe points can be enabled and/or disabled. The effect of
6187 enabling or disabling a probe depends on the type of probe being
6188 handled. Some @code{DTrace} probes can be enabled or
6189 disabled, but @code{SystemTap} probes cannot be disabled.
6191 You can enable (or disable) one or more probes using the following
6192 commands, with optional arguments:
6194 @anchor{enable probes}
6196 @kindex enable probes
6197 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6198 If given, @var{provider} is a regular expression used to match against
6199 provider names when selecting which probes to enable. If omitted,
6200 all probes from all providers are enabled.
6202 If given, @var{name} is a regular expression to match against probe
6203 names when selecting which probes to enable. If omitted, probe names
6204 are not considered when deciding whether to enable them.
6206 If given, @var{objfile} is a regular expression used to select which
6207 object files (executable or shared libraries) to examine. If not
6208 given, all object files are considered.
6210 @kindex disable probes
6211 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6212 See the @code{enable probes} command above for a description of the
6213 optional arguments accepted by this command.
6216 @vindex $_probe_arg@r{, convenience variable}
6217 A probe may specify up to twelve arguments. These are available at the
6218 point at which the probe is defined---that is, when the current PC is
6219 at the probe's location. The arguments are available using the
6220 convenience variables (@pxref{Convenience Vars})
6221 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6222 probes each probe argument is an integer of the appropriate size;
6223 types are not preserved. In @code{DTrace} probes types are preserved
6224 provided that they are recognized as such by @value{GDBN}; otherwise
6225 the value of the probe argument will be a long integer. The
6226 convenience variable @code{$_probe_argc} holds the number of arguments
6227 at the current probe point.
6229 These variables are always available, but attempts to access them at
6230 any location other than a probe point will cause @value{GDBN} to give
6234 @c @ifclear BARETARGET
6235 @node Error in Breakpoints
6236 @subsection ``Cannot insert breakpoints''
6238 If you request too many active hardware-assisted breakpoints and
6239 watchpoints, you will see this error message:
6241 @c FIXME: the precise wording of this message may change; the relevant
6242 @c source change is not committed yet (Sep 3, 1999).
6244 Stopped; cannot insert breakpoints.
6245 You may have requested too many hardware breakpoints and watchpoints.
6249 This message is printed when you attempt to resume the program, since
6250 only then @value{GDBN} knows exactly how many hardware breakpoints and
6251 watchpoints it needs to insert.
6253 When this message is printed, you need to disable or remove some of the
6254 hardware-assisted breakpoints and watchpoints, and then continue.
6256 @node Breakpoint-related Warnings
6257 @subsection ``Breakpoint address adjusted...''
6258 @cindex breakpoint address adjusted
6260 Some processor architectures place constraints on the addresses at
6261 which breakpoints may be placed. For architectures thus constrained,
6262 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6263 with the constraints dictated by the architecture.
6265 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6266 a VLIW architecture in which a number of RISC-like instructions may be
6267 bundled together for parallel execution. The FR-V architecture
6268 constrains the location of a breakpoint instruction within such a
6269 bundle to the instruction with the lowest address. @value{GDBN}
6270 honors this constraint by adjusting a breakpoint's address to the
6271 first in the bundle.
6273 It is not uncommon for optimized code to have bundles which contain
6274 instructions from different source statements, thus it may happen that
6275 a breakpoint's address will be adjusted from one source statement to
6276 another. Since this adjustment may significantly alter @value{GDBN}'s
6277 breakpoint related behavior from what the user expects, a warning is
6278 printed when the breakpoint is first set and also when the breakpoint
6281 A warning like the one below is printed when setting a breakpoint
6282 that's been subject to address adjustment:
6285 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6288 Such warnings are printed both for user settable and @value{GDBN}'s
6289 internal breakpoints. If you see one of these warnings, you should
6290 verify that a breakpoint set at the adjusted address will have the
6291 desired affect. If not, the breakpoint in question may be removed and
6292 other breakpoints may be set which will have the desired behavior.
6293 E.g., it may be sufficient to place the breakpoint at a later
6294 instruction. A conditional breakpoint may also be useful in some
6295 cases to prevent the breakpoint from triggering too often.
6297 @value{GDBN} will also issue a warning when stopping at one of these
6298 adjusted breakpoints:
6301 warning: Breakpoint 1 address previously adjusted from 0x00010414
6305 When this warning is encountered, it may be too late to take remedial
6306 action except in cases where the breakpoint is hit earlier or more
6307 frequently than expected.
6309 @node Continuing and Stepping
6310 @section Continuing and Stepping
6314 @cindex resuming execution
6315 @dfn{Continuing} means resuming program execution until your program
6316 completes normally. In contrast, @dfn{stepping} means executing just
6317 one more ``step'' of your program, where ``step'' may mean either one
6318 line of source code, or one machine instruction (depending on what
6319 particular command you use). Either when continuing or when stepping,
6320 your program may stop even sooner, due to a breakpoint or a signal. (If
6321 it stops due to a signal, you may want to use @code{handle}, or use
6322 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6323 or you may step into the signal's handler (@pxref{stepping and signal
6328 @kindex c @r{(@code{continue})}
6329 @kindex fg @r{(resume foreground execution)}
6330 @item continue @r{[}@var{ignore-count}@r{]}
6331 @itemx c @r{[}@var{ignore-count}@r{]}
6332 @itemx fg @r{[}@var{ignore-count}@r{]}
6333 Resume program execution, at the address where your program last stopped;
6334 any breakpoints set at that address are bypassed. The optional argument
6335 @var{ignore-count} allows you to specify a further number of times to
6336 ignore a breakpoint at this location; its effect is like that of
6337 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6339 The argument @var{ignore-count} is meaningful only when your program
6340 stopped due to a breakpoint. At other times, the argument to
6341 @code{continue} is ignored.
6343 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6344 debugged program is deemed to be the foreground program) are provided
6345 purely for convenience, and have exactly the same behavior as
6349 To resume execution at a different place, you can use @code{return}
6350 (@pxref{Returning, ,Returning from a Function}) to go back to the
6351 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6352 Different Address}) to go to an arbitrary location in your program.
6354 A typical technique for using stepping is to set a breakpoint
6355 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6356 beginning of the function or the section of your program where a problem
6357 is believed to lie, run your program until it stops at that breakpoint,
6358 and then step through the suspect area, examining the variables that are
6359 interesting, until you see the problem happen.
6363 @kindex s @r{(@code{step})}
6365 Continue running your program until control reaches a different source
6366 line, then stop it and return control to @value{GDBN}. This command is
6367 abbreviated @code{s}.
6370 @c "without debugging information" is imprecise; actually "without line
6371 @c numbers in the debugging information". (gcc -g1 has debugging info but
6372 @c not line numbers). But it seems complex to try to make that
6373 @c distinction here.
6374 @emph{Warning:} If you use the @code{step} command while control is
6375 within a function that was compiled without debugging information,
6376 execution proceeds until control reaches a function that does have
6377 debugging information. Likewise, it will not step into a function which
6378 is compiled without debugging information. To step through functions
6379 without debugging information, use the @code{stepi} command, described
6383 The @code{step} command only stops at the first instruction of a source
6384 line. This prevents the multiple stops that could otherwise occur in
6385 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6386 to stop if a function that has debugging information is called within
6387 the line. In other words, @code{step} @emph{steps inside} any functions
6388 called within the line.
6390 Also, the @code{step} command only enters a function if there is line
6391 number information for the function. Otherwise it acts like the
6392 @code{next} command. This avoids problems when using @code{cc -gl}
6393 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6394 was any debugging information about the routine.
6396 @item step @var{count}
6397 Continue running as in @code{step}, but do so @var{count} times. If a
6398 breakpoint is reached, or a signal not related to stepping occurs before
6399 @var{count} steps, stepping stops right away.
6402 @kindex n @r{(@code{next})}
6403 @item next @r{[}@var{count}@r{]}
6404 Continue to the next source line in the current (innermost) stack frame.
6405 This is similar to @code{step}, but function calls that appear within
6406 the line of code are executed without stopping. Execution stops when
6407 control reaches a different line of code at the original stack level
6408 that was executing when you gave the @code{next} command. This command
6409 is abbreviated @code{n}.
6411 An argument @var{count} is a repeat count, as for @code{step}.
6414 @c FIX ME!! Do we delete this, or is there a way it fits in with
6415 @c the following paragraph? --- Vctoria
6417 @c @code{next} within a function that lacks debugging information acts like
6418 @c @code{step}, but any function calls appearing within the code of the
6419 @c function are executed without stopping.
6421 The @code{next} command only stops at the first instruction of a
6422 source line. This prevents multiple stops that could otherwise occur in
6423 @code{switch} statements, @code{for} loops, etc.
6425 @kindex set step-mode
6427 @cindex functions without line info, and stepping
6428 @cindex stepping into functions with no line info
6429 @itemx set step-mode on
6430 The @code{set step-mode on} command causes the @code{step} command to
6431 stop at the first instruction of a function which contains no debug line
6432 information rather than stepping over it.
6434 This is useful in cases where you may be interested in inspecting the
6435 machine instructions of a function which has no symbolic info and do not
6436 want @value{GDBN} to automatically skip over this function.
6438 @item set step-mode off
6439 Causes the @code{step} command to step over any functions which contains no
6440 debug information. This is the default.
6442 @item show step-mode
6443 Show whether @value{GDBN} will stop in or step over functions without
6444 source line debug information.
6447 @kindex fin @r{(@code{finish})}
6449 Continue running until just after function in the selected stack frame
6450 returns. Print the returned value (if any). This command can be
6451 abbreviated as @code{fin}.
6453 Contrast this with the @code{return} command (@pxref{Returning,
6454 ,Returning from a Function}).
6456 @kindex set print finish
6457 @kindex show print finish
6458 @item set print finish @r{[}on|off@r{]}
6459 @itemx show print finish
6460 By default the @code{finish} command will show the value that is
6461 returned by the function. This can be disabled using @code{set print
6462 finish off}. When disabled, the value is still entered into the value
6463 history (@pxref{Value History}), but not displayed.
6466 @kindex u @r{(@code{until})}
6467 @cindex run until specified location
6470 Continue running until a source line past the current line, in the
6471 current stack frame, is reached. This command is used to avoid single
6472 stepping through a loop more than once. It is like the @code{next}
6473 command, except that when @code{until} encounters a jump, it
6474 automatically continues execution until the program counter is greater
6475 than the address of the jump.
6477 This means that when you reach the end of a loop after single stepping
6478 though it, @code{until} makes your program continue execution until it
6479 exits the loop. In contrast, a @code{next} command at the end of a loop
6480 simply steps back to the beginning of the loop, which forces you to step
6481 through the next iteration.
6483 @code{until} always stops your program if it attempts to exit the current
6486 @code{until} may produce somewhat counterintuitive results if the order
6487 of machine code does not match the order of the source lines. For
6488 example, in the following excerpt from a debugging session, the @code{f}
6489 (@code{frame}) command shows that execution is stopped at line
6490 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6494 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6496 (@value{GDBP}) until
6497 195 for ( ; argc > 0; NEXTARG) @{
6500 This happened because, for execution efficiency, the compiler had
6501 generated code for the loop closure test at the end, rather than the
6502 start, of the loop---even though the test in a C @code{for}-loop is
6503 written before the body of the loop. The @code{until} command appeared
6504 to step back to the beginning of the loop when it advanced to this
6505 expression; however, it has not really gone to an earlier
6506 statement---not in terms of the actual machine code.
6508 @code{until} with no argument works by means of single
6509 instruction stepping, and hence is slower than @code{until} with an
6512 @item until @var{locspec}
6513 @itemx u @var{locspec}
6514 Continue running your program until either it reaches a code location
6515 that results from resolving @var{locspec}, or the current stack frame
6516 returns. @var{locspec} is any of the forms described in @ref{Location
6518 This form of the command uses temporary breakpoints, and
6519 hence is quicker than @code{until} without an argument. The specified
6520 location is actually reached only if it is in the current frame. This
6521 implies that @code{until} can be used to skip over recursive function
6522 invocations. For instance in the code below, if the current location is
6523 line @code{96}, issuing @code{until 99} will execute the program up to
6524 line @code{99} in the same invocation of factorial, i.e., after the inner
6525 invocations have returned.
6528 94 int factorial (int value)
6530 96 if (value > 1) @{
6531 97 value *= factorial (value - 1);
6538 @kindex advance @var{locspec}
6539 @item advance @var{locspec}
6540 Continue running your program until either it reaches a code location
6541 that results from resolving @var{locspec}, or the current stack frame
6542 returns. @var{locspec} is any of the forms described in @ref{Location
6543 Specifications}. This command is similar to @code{until}, but
6544 @code{advance} will not skip over recursive function calls, and the
6545 target code location doesn't have to be in the same frame as the
6550 @kindex si @r{(@code{stepi})}
6552 @itemx stepi @var{arg}
6554 Execute one machine instruction, then stop and return to the debugger.
6556 It is often useful to do @samp{display/i $pc} when stepping by machine
6557 instructions. This makes @value{GDBN} automatically display the next
6558 instruction to be executed, each time your program stops. @xref{Auto
6559 Display,, Automatic Display}.
6561 An argument is a repeat count, as in @code{step}.
6565 @kindex ni @r{(@code{nexti})}
6567 @itemx nexti @var{arg}
6569 Execute one machine instruction, but if it is a function call,
6570 proceed until the function returns.
6572 An argument is a repeat count, as in @code{next}.
6576 @anchor{range stepping}
6577 @cindex range stepping
6578 @cindex target-assisted range stepping
6579 By default, and if available, @value{GDBN} makes use of
6580 target-assisted @dfn{range stepping}. In other words, whenever you
6581 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6582 tells the target to step the corresponding range of instruction
6583 addresses instead of issuing multiple single-steps. This speeds up
6584 line stepping, particularly for remote targets. Ideally, there should
6585 be no reason you would want to turn range stepping off. However, it's
6586 possible that a bug in the debug info, a bug in the remote stub (for
6587 remote targets), or even a bug in @value{GDBN} could make line
6588 stepping behave incorrectly when target-assisted range stepping is
6589 enabled. You can use the following command to turn off range stepping
6593 @kindex set range-stepping
6594 @kindex show range-stepping
6595 @item set range-stepping
6596 @itemx show range-stepping
6597 Control whether range stepping is enabled.
6599 If @code{on}, and the target supports it, @value{GDBN} tells the
6600 target to step a range of addresses itself, instead of issuing
6601 multiple single-steps. If @code{off}, @value{GDBN} always issues
6602 single-steps, even if range stepping is supported by the target. The
6603 default is @code{on}.
6607 @node Skipping Over Functions and Files
6608 @section Skipping Over Functions and Files
6609 @cindex skipping over functions and files
6611 The program you are debugging may contain some functions which are
6612 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6613 skip a function, all functions in a file or a particular function in
6614 a particular file when stepping.
6616 For example, consider the following C function:
6627 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6628 are not interested in stepping through @code{boring}. If you run @code{step}
6629 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6630 step over both @code{foo} and @code{boring}!
6632 One solution is to @code{step} into @code{boring} and use the @code{finish}
6633 command to immediately exit it. But this can become tedious if @code{boring}
6634 is called from many places.
6636 A more flexible solution is to execute @kbd{skip boring}. This instructs
6637 @value{GDBN} never to step into @code{boring}. Now when you execute
6638 @code{step} at line 103, you'll step over @code{boring} and directly into
6641 Functions may be skipped by providing either a function name, linespec
6642 (@pxref{Location Specifications}), regular expression that matches the function's
6643 name, file name or a @code{glob}-style pattern that matches the file name.
6645 On Posix systems the form of the regular expression is
6646 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6647 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6648 expression is whatever is provided by the @code{regcomp} function of
6649 the underlying system.
6650 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6651 description of @code{glob}-style patterns.
6655 @item skip @r{[}@var{options}@r{]}
6656 The basic form of the @code{skip} command takes zero or more options
6657 that specify what to skip.
6658 The @var{options} argument is any useful combination of the following:
6661 @item -file @var{file}
6662 @itemx -fi @var{file}
6663 Functions in @var{file} will be skipped over when stepping.
6665 @item -gfile @var{file-glob-pattern}
6666 @itemx -gfi @var{file-glob-pattern}
6667 @cindex skipping over files via glob-style patterns
6668 Functions in files matching @var{file-glob-pattern} will be skipped
6672 (@value{GDBP}) skip -gfi utils/*.c
6675 @item -function @var{linespec}
6676 @itemx -fu @var{linespec}
6677 Functions named by @var{linespec} or the function containing the line
6678 named by @var{linespec} will be skipped over when stepping.
6679 @xref{Location Specifications}.
6681 @item -rfunction @var{regexp}
6682 @itemx -rfu @var{regexp}
6683 @cindex skipping over functions via regular expressions
6684 Functions whose name matches @var{regexp} will be skipped over when stepping.
6686 This form is useful for complex function names.
6687 For example, there is generally no need to step into C@t{++} @code{std::string}
6688 constructors or destructors. Plus with C@t{++} templates it can be hard to
6689 write out the full name of the function, and often it doesn't matter what
6690 the template arguments are. Specifying the function to be skipped as a
6691 regular expression makes this easier.
6694 (@value{GDBP}) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6697 If you want to skip every templated C@t{++} constructor and destructor
6698 in the @code{std} namespace you can do:
6701 (@value{GDBP}) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6705 If no options are specified, the function you're currently debugging
6708 @kindex skip function
6709 @item skip function @r{[}@var{linespec}@r{]}
6710 After running this command, the function named by @var{linespec} or the
6711 function containing the line named by @var{linespec} will be skipped over when
6712 stepping. @xref{Location Specifications}.
6714 If you do not specify @var{linespec}, the function you're currently debugging
6717 (If you have a function called @code{file} that you want to skip, use
6718 @kbd{skip function file}.)
6721 @item skip file @r{[}@var{filename}@r{]}
6722 After running this command, any function whose source lives in @var{filename}
6723 will be skipped over when stepping.
6726 (@value{GDBP}) skip file boring.c
6727 File boring.c will be skipped when stepping.
6730 If you do not specify @var{filename}, functions whose source lives in the file
6731 you're currently debugging will be skipped.
6734 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6735 These are the commands for managing your list of skips:
6739 @item info skip @r{[}@var{range}@r{]}
6740 Print details about the specified skip(s). If @var{range} is not specified,
6741 print a table with details about all functions and files marked for skipping.
6742 @code{info skip} prints the following information about each skip:
6746 A number identifying this skip.
6747 @item Enabled or Disabled
6748 Enabled skips are marked with @samp{y}.
6749 Disabled skips are marked with @samp{n}.
6751 If the file name is a @samp{glob} pattern this is @samp{y}.
6752 Otherwise it is @samp{n}.
6754 The name or @samp{glob} pattern of the file to be skipped.
6755 If no file is specified this is @samp{<none>}.
6757 If the function name is a @samp{regular expression} this is @samp{y}.
6758 Otherwise it is @samp{n}.
6760 The name or regular expression of the function to skip.
6761 If no function is specified this is @samp{<none>}.
6765 @item skip delete @r{[}@var{range}@r{]}
6766 Delete the specified skip(s). If @var{range} is not specified, delete all
6770 @item skip enable @r{[}@var{range}@r{]}
6771 Enable the specified skip(s). If @var{range} is not specified, enable all
6774 @kindex skip disable
6775 @item skip disable @r{[}@var{range}@r{]}
6776 Disable the specified skip(s). If @var{range} is not specified, disable all
6779 @kindex set debug skip
6780 @item set debug skip @r{[}on|off@r{]}
6781 Set whether to print the debug output about skipping files and functions.
6783 @kindex show debug skip
6784 @item show debug skip
6785 Show whether the debug output about skipping files and functions is printed.
6793 A signal is an asynchronous event that can happen in a program. The
6794 operating system defines the possible kinds of signals, and gives each
6795 kind a name and a number. For example, in Unix @code{SIGINT} is the
6796 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6797 @code{SIGSEGV} is the signal a program gets from referencing a place in
6798 memory far away from all the areas in use; @code{SIGALRM} occurs when
6799 the alarm clock timer goes off (which happens only if your program has
6800 requested an alarm).
6802 @cindex fatal signals
6803 Some signals, including @code{SIGALRM}, are a normal part of the
6804 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6805 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6806 program has not specified in advance some other way to handle the signal.
6807 @code{SIGINT} does not indicate an error in your program, but it is normally
6808 fatal so it can carry out the purpose of the interrupt: to kill the program.
6810 @value{GDBN} has the ability to detect any occurrence of a signal in your
6811 program. You can tell @value{GDBN} in advance what to do for each kind of
6814 @cindex handling signals
6815 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6816 @code{SIGALRM} be silently passed to your program
6817 (so as not to interfere with their role in the program's functioning)
6818 but to stop your program immediately whenever an error signal happens.
6819 You can change these settings with the @code{handle} command.
6822 @kindex info signals
6826 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6827 handle each one. You can use this to see the signal numbers of all
6828 the defined types of signals.
6830 @item info signals @var{sig}
6831 Similar, but print information only about the specified signal number.
6833 @code{info handle} is an alias for @code{info signals}.
6835 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6836 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6837 for details about this command.
6840 @item handle @var{signal} @r{[} @var{signal} @dots{} @r{]} @r{[}@var{keywords}@dots{}@r{]}
6841 Change the way @value{GDBN} handles each @var{signal}. Each
6842 @var{signal} can be the number of a signal or its name (with or
6843 without the @samp{SIG} at the beginning); a list of signal numbers of
6844 the form @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning
6845 all the known signals, except @code{SIGINT} and @code{SIGTRAP}, which
6846 are used by @value{GDBN}. Optional argument @var{keywords}, described
6847 below, say what changes to make to all of the specified signals.
6851 The keywords allowed by the @code{handle} command can be abbreviated.
6852 Their full names are:
6856 @value{GDBN} should not stop your program when this signal happens. It may
6857 still print a message telling you that the signal has come in.
6860 @value{GDBN} should stop your program when this signal happens. This implies
6861 the @code{print} keyword as well.
6864 @value{GDBN} should print a message when this signal happens.
6867 @value{GDBN} should not mention the occurrence of the signal at all. This
6868 implies the @code{nostop} keyword as well.
6872 @value{GDBN} should allow your program to see this signal; your program
6873 can handle the signal, or else it may terminate if the signal is fatal
6874 and not handled. @code{pass} and @code{noignore} are synonyms.
6878 @value{GDBN} should not allow your program to see this signal.
6879 @code{nopass} and @code{ignore} are synonyms.
6883 When a signal stops your program, the signal is not visible to the
6885 continue. Your program sees the signal then, if @code{pass} is in
6886 effect for the signal in question @emph{at that time}. In other words,
6887 after @value{GDBN} reports a signal, you can use the @code{handle}
6888 command with @code{pass} or @code{nopass} to control whether your
6889 program sees that signal when you continue.
6891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6896 You can also use the @code{signal} command to prevent your program from
6897 seeing a signal, or cause it to see a signal it normally would not see,
6898 or to give it any signal at any time. For example, if your program stopped
6899 due to some sort of memory reference error, you might store correct
6900 values into the erroneous variables and continue, hoping to see more
6901 execution; but your program would probably terminate immediately as
6902 a result of the fatal signal once it saw the signal. To prevent this,
6903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6906 @cindex stepping and signal handlers
6907 @anchor{stepping and signal handlers}
6909 @value{GDBN} optimizes for stepping the mainline code. If a signal
6910 that has @code{handle nostop} and @code{handle pass} set arrives while
6911 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6912 in progress, @value{GDBN} lets the signal handler run and then resumes
6913 stepping the mainline code once the signal handler returns. In other
6914 words, @value{GDBN} steps over the signal handler. This prevents
6915 signals that you've specified as not interesting (with @code{handle
6916 nostop}) from changing the focus of debugging unexpectedly. Note that
6917 the signal handler itself may still hit a breakpoint, stop for another
6918 signal that has @code{handle stop} in effect, or for any other event
6919 that normally results in stopping the stepping command sooner. Also
6920 note that @value{GDBN} still informs you that the program received a
6921 signal if @code{handle print} is set.
6923 @anchor{stepping into signal handlers}
6925 If you set @code{handle pass} for a signal, and your program sets up a
6926 handler for it, then issuing a stepping command, such as @code{step}
6927 or @code{stepi}, when your program is stopped due to the signal will
6928 step @emph{into} the signal handler (if the target supports that).
6930 Likewise, if you use the @code{queue-signal} command to queue a signal
6931 to be delivered to the current thread when execution of the thread
6932 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6933 stepping command will step into the signal handler.
6935 Here's an example, using @code{stepi} to step to the first instruction
6936 of @code{SIGUSR1}'s handler:
6939 (@value{GDBP}) handle SIGUSR1
6940 Signal Stop Print Pass to program Description
6941 SIGUSR1 Yes Yes Yes User defined signal 1
6945 Program received signal SIGUSR1, User defined signal 1.
6946 main () sigusr1.c:28
6949 sigusr1_handler () at sigusr1.c:9
6953 The same, but using @code{queue-signal} instead of waiting for the
6954 program to receive the signal first:
6959 (@value{GDBP}) queue-signal SIGUSR1
6961 sigusr1_handler () at sigusr1.c:9
6966 @cindex extra signal information
6967 @anchor{extra signal information}
6969 On some targets, @value{GDBN} can inspect extra signal information
6970 associated with the intercepted signal, before it is actually
6971 delivered to the program being debugged. This information is exported
6972 by the convenience variable @code{$_siginfo}, and consists of data
6973 that is passed by the kernel to the signal handler at the time of the
6974 receipt of a signal. The data type of the information itself is
6975 target dependent. You can see the data type using the @code{ptype
6976 $_siginfo} command. On Unix systems, it typically corresponds to the
6977 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6980 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6981 referenced address that raised a segmentation fault.
6985 (@value{GDBP}) continue
6986 Program received signal SIGSEGV, Segmentation fault.
6987 0x0000000000400766 in main ()
6989 (@value{GDBP}) ptype $_siginfo
6996 struct @{...@} _kill;
6997 struct @{...@} _timer;
6999 struct @{...@} _sigchld;
7000 struct @{...@} _sigfault;
7001 struct @{...@} _sigpoll;
7004 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
7008 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
7009 $1 = (void *) 0x7ffff7ff7000
7013 Depending on target support, @code{$_siginfo} may also be writable.
7015 @cindex Intel MPX boundary violations
7016 @cindex boundary violations, Intel MPX
7017 On some targets, a @code{SIGSEGV} can be caused by a boundary
7018 violation, i.e., accessing an address outside of the allowed range.
7019 In those cases @value{GDBN} may displays additional information,
7020 depending on how @value{GDBN} has been told to handle the signal.
7021 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
7022 kind: "Upper" or "Lower", the memory address accessed and the
7023 bounds, while with @code{handle nostop SIGSEGV} no additional
7024 information is displayed.
7026 The usual output of a segfault is:
7028 Program received signal SIGSEGV, Segmentation fault
7029 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
7030 68 value = *(p + len);
7033 While a bound violation is presented as:
7035 Program received signal SIGSEGV, Segmentation fault
7036 Upper bound violation while accessing address 0x7fffffffc3b3
7037 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
7038 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
7039 68 value = *(p + len);
7043 @section Stopping and Starting Multi-thread Programs
7045 @cindex stopped threads
7046 @cindex threads, stopped
7048 @cindex continuing threads
7049 @cindex threads, continuing
7051 @value{GDBN} supports debugging programs with multiple threads
7052 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
7053 are two modes of controlling execution of your program within the
7054 debugger. In the default mode, referred to as @dfn{all-stop mode},
7055 when any thread in your program stops (for example, at a breakpoint
7056 or while being stepped), all other threads in the program are also stopped by
7057 @value{GDBN}. On some targets, @value{GDBN} also supports
7058 @dfn{non-stop mode}, in which other threads can continue to run freely while
7059 you examine the stopped thread in the debugger.
7062 * All-Stop Mode:: All threads stop when GDB takes control
7063 * Non-Stop Mode:: Other threads continue to execute
7064 * Background Execution:: Running your program asynchronously
7065 * Thread-Specific Breakpoints:: Controlling breakpoints
7066 * Interrupted System Calls:: GDB may interfere with system calls
7067 * Observer Mode:: GDB does not alter program behavior
7071 @subsection All-Stop Mode
7073 @cindex all-stop mode
7075 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
7076 @emph{all} threads of execution stop, not just the current thread. This
7077 allows you to examine the overall state of the program, including
7078 switching between threads, without worrying that things may change
7081 Conversely, whenever you restart the program, @emph{all} threads start
7082 executing. @emph{This is true even when single-stepping} with commands
7083 like @code{step} or @code{next}.
7085 In particular, @value{GDBN} cannot single-step all threads in lockstep.
7086 Since thread scheduling is up to your debugging target's operating
7087 system (not controlled by @value{GDBN}), other threads may
7088 execute more than one statement while the current thread completes a
7089 single step. Moreover, in general other threads stop in the middle of a
7090 statement, rather than at a clean statement boundary, when the program
7093 You might even find your program stopped in another thread after
7094 continuing or even single-stepping. This happens whenever some other
7095 thread runs into a breakpoint, a signal, or an exception before the
7096 first thread completes whatever you requested.
7098 @cindex automatic thread selection
7099 @cindex switching threads automatically
7100 @cindex threads, automatic switching
7101 Whenever @value{GDBN} stops your program, due to a breakpoint or a
7102 signal, it automatically selects the thread where that breakpoint or
7103 signal happened. @value{GDBN} alerts you to the context switch with a
7104 message such as @samp{[Switching to Thread @var{n}]} to identify the
7107 @anchor{set scheduler-locking}
7109 On some OSes, you can modify @value{GDBN}'s default behavior by
7110 locking the OS scheduler to allow only a single thread to run.
7113 @item set scheduler-locking @var{mode}
7114 @cindex scheduler-locking
7115 @cindex scheduler locking mode
7116 @cindex lock scheduler
7117 Set the scheduler locking mode. It applies to normal execution,
7118 record mode, and replay mode. @var{mode} can be one of
7123 There is no locking and any thread may run at any time.
7126 Only the current thread may run when the inferior is resumed. New
7127 threads created by the resumed thread are held stopped at their entry
7128 point, before they execute any instruction.
7131 Behaves like @code{on} when stepping, and @code{off} otherwise.
7132 Threads other than the current never get a chance to run when you
7133 step, and they are completely free to run when you use commands like
7134 @samp{continue}, @samp{until}, or @samp{finish}.
7136 This mode optimizes for single-stepping; it prevents other threads
7137 from preempting the current thread while you are stepping, so that the
7138 focus of debugging does not change unexpectedly. However, unless
7139 another thread hits a breakpoint during its timeslice, @value{GDBN}
7140 does not change the current thread away from the thread that you are
7144 Behaves like @code{on} in replay mode, and @code{off} in either record
7145 mode or during normal execution. This is the default mode.
7148 @item show scheduler-locking
7149 Display the current scheduler locking mode.
7152 @cindex resume threads of multiple processes simultaneously
7153 By default, when you issue one of the execution commands such as
7154 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
7155 threads of the current inferior to run. For example, if @value{GDBN}
7156 is attached to two inferiors, each with two threads, the
7157 @code{continue} command resumes only the two threads of the current
7158 inferior. This is useful, for example, when you debug a program that
7159 forks and you want to hold the parent stopped (so that, for instance,
7160 it doesn't run to exit), while you debug the child. In other
7161 situations, you may not be interested in inspecting the current state
7162 of any of the processes @value{GDBN} is attached to, and you may want
7163 to resume them all until some breakpoint is hit. In the latter case,
7164 you can instruct @value{GDBN} to allow all threads of all the
7165 inferiors to run with the @w{@code{set schedule-multiple}} command.
7168 @kindex set schedule-multiple
7169 @item set schedule-multiple
7170 Set the mode for allowing threads of multiple processes to be resumed
7171 when an execution command is issued. When @code{on}, all threads of
7172 all processes are allowed to run. When @code{off}, only the threads
7173 of the current process are resumed. The default is @code{off}. The
7174 @code{scheduler-locking} mode takes precedence when set to @code{on},
7175 or while you are stepping and set to @code{step}.
7177 @item show schedule-multiple
7178 Display the current mode for resuming the execution of threads of
7183 @subsection Non-Stop Mode
7185 @cindex non-stop mode
7187 @c This section is really only a place-holder, and needs to be expanded
7188 @c with more details.
7190 For some multi-threaded targets, @value{GDBN} supports an optional
7191 mode of operation in which you can examine stopped program threads in
7192 the debugger while other threads continue to execute freely. This
7193 minimizes intrusion when debugging live systems, such as programs
7194 where some threads have real-time constraints or must continue to
7195 respond to external events. This is referred to as @dfn{non-stop} mode.
7197 In non-stop mode, when a thread stops to report a debugging event,
7198 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7199 threads as well, in contrast to the all-stop mode behavior. Additionally,
7200 execution commands such as @code{continue} and @code{step} apply by default
7201 only to the current thread in non-stop mode, rather than all threads as
7202 in all-stop mode. This allows you to control threads explicitly in
7203 ways that are not possible in all-stop mode --- for example, stepping
7204 one thread while allowing others to run freely, stepping
7205 one thread while holding all others stopped, or stepping several threads
7206 independently and simultaneously.
7208 To enter non-stop mode, use this sequence of commands before you run
7209 or attach to your program:
7212 # If using the CLI, pagination breaks non-stop.
7215 # Finally, turn it on!
7219 You can use these commands to manipulate the non-stop mode setting:
7222 @kindex set non-stop
7223 @item set non-stop on
7224 Enable selection of non-stop mode.
7225 @item set non-stop off
7226 Disable selection of non-stop mode.
7227 @kindex show non-stop
7229 Show the current non-stop enablement setting.
7232 Note these commands only reflect whether non-stop mode is enabled,
7233 not whether the currently-executing program is being run in non-stop mode.
7234 In particular, the @code{set non-stop} preference is only consulted when
7235 @value{GDBN} starts or connects to the target program, and it is generally
7236 not possible to switch modes once debugging has started. Furthermore,
7237 since not all targets support non-stop mode, even when you have enabled
7238 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7241 In non-stop mode, all execution commands apply only to the current thread
7242 by default. That is, @code{continue} only continues one thread.
7243 To continue all threads, issue @code{continue -a} or @code{c -a}.
7245 You can use @value{GDBN}'s background execution commands
7246 (@pxref{Background Execution}) to run some threads in the background
7247 while you continue to examine or step others from @value{GDBN}.
7248 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7249 always executed asynchronously in non-stop mode.
7251 Suspending execution is done with the @code{interrupt} command when
7252 running in the background, or @kbd{Ctrl-c} during foreground execution.
7253 In all-stop mode, this stops the whole process;
7254 but in non-stop mode the interrupt applies only to the current thread.
7255 To stop the whole program, use @code{interrupt -a}.
7257 Other execution commands do not currently support the @code{-a} option.
7259 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7260 that thread current, as it does in all-stop mode. This is because the
7261 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7262 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7263 changed to a different thread just as you entered a command to operate on the
7264 previously current thread.
7266 @node Background Execution
7267 @subsection Background Execution
7269 @cindex foreground execution
7270 @cindex background execution
7271 @cindex asynchronous execution
7272 @cindex execution, foreground, background and asynchronous
7274 @value{GDBN}'s execution commands have two variants: the normal
7275 foreground (synchronous) behavior, and a background
7276 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7277 the program to report that some thread has stopped before prompting for
7278 another command. In background execution, @value{GDBN} immediately gives
7279 a command prompt so that you can issue other commands while your program runs.
7281 If the target doesn't support async mode, @value{GDBN} issues an error
7282 message if you attempt to use the background execution commands.
7284 @cindex @code{&}, background execution of commands
7285 To specify background execution, add a @code{&} to the command. For example,
7286 the background form of the @code{continue} command is @code{continue&}, or
7287 just @code{c&}. The execution commands that accept background execution
7293 @xref{Starting, , Starting your Program}.
7297 @xref{Attach, , Debugging an Already-running Process}.
7301 @xref{Continuing and Stepping, step}.
7305 @xref{Continuing and Stepping, stepi}.
7309 @xref{Continuing and Stepping, next}.
7313 @xref{Continuing and Stepping, nexti}.
7317 @xref{Continuing and Stepping, continue}.
7321 @xref{Continuing and Stepping, finish}.
7325 @xref{Continuing and Stepping, until}.
7329 Background execution is especially useful in conjunction with non-stop
7330 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7331 However, you can also use these commands in the normal all-stop mode with
7332 the restriction that you cannot issue another execution command until the
7333 previous one finishes. Examples of commands that are valid in all-stop
7334 mode while the program is running include @code{help} and @code{info break}.
7336 You can interrupt your program while it is running in the background by
7337 using the @code{interrupt} command.
7344 Suspend execution of the running program. In all-stop mode,
7345 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7346 only the current thread. To stop the whole program in non-stop mode,
7347 use @code{interrupt -a}.
7350 @node Thread-Specific Breakpoints
7351 @subsection Thread-Specific Breakpoints
7353 When your program has multiple threads (@pxref{Threads,, Debugging
7354 Programs with Multiple Threads}), you can choose whether to set
7355 breakpoints on all threads, or on a particular thread.
7358 @cindex breakpoints and threads
7359 @cindex thread breakpoints
7360 @kindex break @dots{} thread @var{thread-id}
7361 @item break @var{locspec} thread @var{thread-id}
7362 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7363 @var{locspec} specifies a code location or locations in your program.
7364 @xref{Location Specifications}, for details.
7366 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7367 to specify that you only want @value{GDBN} to stop the program when a
7368 particular thread reaches this breakpoint. The @var{thread-id} specifier
7369 is one of the thread identifiers assigned by @value{GDBN}, shown
7370 in the first column of the @samp{info threads} display.
7372 If you do not specify @samp{thread @var{thread-id}} when you set a
7373 breakpoint, the breakpoint applies to @emph{all} threads of your
7376 You can use the @code{thread} qualifier on conditional breakpoints as
7377 well; in this case, place @samp{thread @var{thread-id}} before or
7378 after the breakpoint condition, like this:
7381 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7386 Thread-specific breakpoints are automatically deleted when
7387 @value{GDBN} detects the corresponding thread is no longer in the
7388 thread list. For example:
7392 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7395 There are several ways for a thread to disappear, such as a regular
7396 thread exit, but also when you detach from the process with the
7397 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7398 Process}), or if @value{GDBN} loses the remote connection
7399 (@pxref{Remote Debugging}), etc. Note that with some targets,
7400 @value{GDBN} is only able to detect a thread has exited when the user
7401 explicitly asks for the thread list with the @code{info threads}
7404 A breakpoint can't be both thread-specific and inferior-specific
7405 (@pxref{Inferior-Specific Breakpoints}), or task-specific (@pxref{Ada
7406 Tasks}); using more than one of the @code{thread}, @code{inferior}, or
7407 @code{task} keywords when creating a breakpoint will give an error.
7409 @node Interrupted System Calls
7410 @subsection Interrupted System Calls
7412 @cindex thread breakpoints and system calls
7413 @cindex system calls and thread breakpoints
7414 @cindex premature return from system calls
7415 There is an unfortunate side effect when using @value{GDBN} to debug
7416 multi-threaded programs. If one thread stops for a
7417 breakpoint, or for some other reason, and another thread is blocked in a
7418 system call, then the system call may return prematurely. This is a
7419 consequence of the interaction between multiple threads and the signals
7420 that @value{GDBN} uses to implement breakpoints and other events that
7423 To handle this problem, your program should check the return value of
7424 each system call and react appropriately. This is good programming
7427 For example, do not write code like this:
7433 The call to @code{sleep} will return early if a different thread stops
7434 at a breakpoint or for some other reason.
7436 Instead, write this:
7441 unslept = sleep (unslept);
7444 A system call is allowed to return early, so the system is still
7445 conforming to its specification. But @value{GDBN} does cause your
7446 multi-threaded program to behave differently than it would without
7449 Also, @value{GDBN} uses internal breakpoints in the thread library to
7450 monitor certain events such as thread creation and thread destruction.
7451 When such an event happens, a system call in another thread may return
7452 prematurely, even though your program does not appear to stop.
7455 @subsection Observer Mode
7457 If you want to build on non-stop mode and observe program behavior
7458 without any chance of disruption by @value{GDBN}, you can set
7459 variables to disable all of the debugger's attempts to modify state,
7460 whether by writing memory, inserting breakpoints, etc. These operate
7461 at a low level, intercepting operations from all commands.
7463 When all of these are set to @code{off}, then @value{GDBN} is said to
7464 be @dfn{observer mode}. As a convenience, the variable
7465 @code{observer} can be set to disable these, plus enable non-stop
7468 Note that @value{GDBN} will not prevent you from making nonsensical
7469 combinations of these settings. For instance, if you have enabled
7470 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7471 then breakpoints that work by writing trap instructions into the code
7472 stream will still not be able to be placed.
7477 @item set observer on
7478 @itemx set observer off
7479 When set to @code{on}, this disables all the permission variables
7480 below (except for @code{insert-fast-tracepoints}), plus enables
7481 non-stop debugging. Setting this to @code{off} switches back to
7482 normal debugging, though remaining in non-stop mode.
7485 Show whether observer mode is on or off.
7487 @kindex may-write-registers
7488 @item set may-write-registers on
7489 @itemx set may-write-registers off
7490 This controls whether @value{GDBN} will attempt to alter the values of
7491 registers, such as with assignment expressions in @code{print}, or the
7492 @code{jump} command. It defaults to @code{on}.
7494 @item show may-write-registers
7495 Show the current permission to write registers.
7497 @kindex may-write-memory
7498 @item set may-write-memory on
7499 @itemx set may-write-memory off
7500 This controls whether @value{GDBN} will attempt to alter the contents
7501 of memory, such as with assignment expressions in @code{print}. It
7502 defaults to @code{on}.
7504 @item show may-write-memory
7505 Show the current permission to write memory.
7507 @kindex may-insert-breakpoints
7508 @item set may-insert-breakpoints on
7509 @itemx set may-insert-breakpoints off
7510 This controls whether @value{GDBN} will attempt to insert breakpoints.
7511 This affects all breakpoints, including internal breakpoints defined
7512 by @value{GDBN}. It defaults to @code{on}.
7514 @item show may-insert-breakpoints
7515 Show the current permission to insert breakpoints.
7517 @kindex may-insert-tracepoints
7518 @item set may-insert-tracepoints on
7519 @itemx set may-insert-tracepoints off
7520 This controls whether @value{GDBN} will attempt to insert (regular)
7521 tracepoints at the beginning of a tracing experiment. It affects only
7522 non-fast tracepoints, fast tracepoints being under the control of
7523 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7525 @item show may-insert-tracepoints
7526 Show the current permission to insert tracepoints.
7528 @kindex may-insert-fast-tracepoints
7529 @item set may-insert-fast-tracepoints on
7530 @itemx set may-insert-fast-tracepoints off
7531 This controls whether @value{GDBN} will attempt to insert fast
7532 tracepoints at the beginning of a tracing experiment. It affects only
7533 fast tracepoints, regular (non-fast) tracepoints being under the
7534 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7536 @item show may-insert-fast-tracepoints
7537 Show the current permission to insert fast tracepoints.
7539 @kindex may-interrupt
7540 @item set may-interrupt on
7541 @itemx set may-interrupt off
7542 This controls whether @value{GDBN} will attempt to interrupt or stop
7543 program execution. When this variable is @code{off}, the
7544 @code{interrupt} command will have no effect, nor will
7545 @kbd{Ctrl-c}. It defaults to @code{on}.
7547 @item show may-interrupt
7548 Show the current permission to interrupt or stop the program.
7552 @node Reverse Execution
7553 @chapter Running programs backward
7554 @cindex reverse execution
7555 @cindex running programs backward
7557 When you are debugging a program, it is not unusual to realize that
7558 you have gone too far, and some event of interest has already happened.
7559 If the target environment supports it, @value{GDBN} can allow you to
7560 ``rewind'' the program by running it backward.
7562 A target environment that supports reverse execution should be able
7563 to ``undo'' the changes in machine state that have taken place as the
7564 program was executing normally. Variables, registers etc.@: should
7565 revert to their previous values. Obviously this requires a great
7566 deal of sophistication on the part of the target environment; not
7567 all target environments can support reverse execution.
7569 When a program is executed in reverse, the instructions that
7570 have most recently been executed are ``un-executed'', in reverse
7571 order. The program counter runs backward, following the previous
7572 thread of execution in reverse. As each instruction is ``un-executed'',
7573 the values of memory and/or registers that were changed by that
7574 instruction are reverted to their previous states. After executing
7575 a piece of source code in reverse, all side effects of that code
7576 should be ``undone'', and all variables should be returned to their
7577 prior values@footnote{
7578 Note that some side effects are easier to undo than others. For instance,
7579 memory and registers are relatively easy, but device I/O is hard. Some
7580 targets may be able undo things like device I/O, and some may not.
7582 The contract between @value{GDBN} and the reverse executing target
7583 requires only that the target do something reasonable when
7584 @value{GDBN} tells it to execute backwards, and then report the
7585 results back to @value{GDBN}. Whatever the target reports back to
7586 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7587 assumes that the memory and registers that the target reports are in a
7588 consistent state, but @value{GDBN} accepts whatever it is given.
7591 On some platforms, @value{GDBN} has built-in support for reverse
7592 execution, activated with the @code{record} or @code{record btrace}
7593 commands. @xref{Process Record and Replay}. Some remote targets,
7594 typically full system emulators, support reverse execution directly
7595 without requiring any special command.
7597 If you are debugging in a target environment that supports
7598 reverse execution, @value{GDBN} provides the following commands.
7601 @kindex reverse-continue
7602 @kindex rc @r{(@code{reverse-continue})}
7603 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7604 @itemx rc @r{[}@var{ignore-count}@r{]}
7605 Beginning at the point where your program last stopped, start executing
7606 in reverse. Reverse execution will stop for breakpoints and synchronous
7607 exceptions (signals), just like normal execution. Behavior of
7608 asynchronous signals depends on the target environment.
7610 @kindex reverse-step
7611 @kindex rs @r{(@code{step})}
7612 @item reverse-step @r{[}@var{count}@r{]}
7613 Run the program backward until control reaches the start of a
7614 different source line; then stop it, and return control to @value{GDBN}.
7616 Like the @code{step} command, @code{reverse-step} will only stop
7617 at the beginning of a source line. It ``un-executes'' the previously
7618 executed source line. If the previous source line included calls to
7619 debuggable functions, @code{reverse-step} will step (backward) into
7620 the called function, stopping at the beginning of the @emph{last}
7621 statement in the called function (typically a return statement).
7623 Also, as with the @code{step} command, if non-debuggable functions are
7624 called, @code{reverse-step} will run thru them backward without stopping.
7626 @kindex reverse-stepi
7627 @kindex rsi @r{(@code{reverse-stepi})}
7628 @item reverse-stepi @r{[}@var{count}@r{]}
7629 Reverse-execute one machine instruction. Note that the instruction
7630 to be reverse-executed is @emph{not} the one pointed to by the program
7631 counter, but the instruction executed prior to that one. For instance,
7632 if the last instruction was a jump, @code{reverse-stepi} will take you
7633 back from the destination of the jump to the jump instruction itself.
7635 @kindex reverse-next
7636 @kindex rn @r{(@code{reverse-next})}
7637 @item reverse-next @r{[}@var{count}@r{]}
7638 Run backward to the beginning of the previous line executed in
7639 the current (innermost) stack frame. If the line contains function
7640 calls, they will be ``un-executed'' without stopping. Starting from
7641 the first line of a function, @code{reverse-next} will take you back
7642 to the caller of that function, @emph{before} the function was called,
7643 just as the normal @code{next} command would take you from the last
7644 line of a function back to its return to its caller
7645 @footnote{Unless the code is too heavily optimized.}.
7647 @kindex reverse-nexti
7648 @kindex rni @r{(@code{reverse-nexti})}
7649 @item reverse-nexti @r{[}@var{count}@r{]}
7650 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7651 in reverse, except that called functions are ``un-executed'' atomically.
7652 That is, if the previously executed instruction was a return from
7653 another function, @code{reverse-nexti} will continue to execute
7654 in reverse until the call to that function (from the current stack
7657 @kindex reverse-finish
7658 @item reverse-finish
7659 Just as the @code{finish} command takes you to the point where the
7660 current function returns, @code{reverse-finish} takes you to the point
7661 where it was called. Instead of ending up at the end of the current
7662 function invocation, you end up at the beginning.
7664 @kindex set exec-direction
7665 @item set exec-direction
7666 Set the direction of target execution.
7667 @item set exec-direction reverse
7668 @cindex execute forward or backward in time
7669 @value{GDBN} will perform all execution commands in reverse, until the
7670 exec-direction mode is changed to ``forward''. Affected commands include
7671 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7672 command cannot be used in reverse mode.
7673 @item set exec-direction forward
7674 @value{GDBN} will perform all execution commands in the normal fashion.
7675 This is the default.
7679 @node Process Record and Replay
7680 @chapter Recording Inferior's Execution and Replaying It
7681 @cindex process record and replay
7682 @cindex recording inferior's execution and replaying it
7684 On some platforms, @value{GDBN} provides a special @dfn{process record
7685 and replay} target that can record a log of the process execution, and
7686 replay it later with both forward and reverse execution commands.
7689 When this target is in use, if the execution log includes the record
7690 for the next instruction, @value{GDBN} will debug in @dfn{replay
7691 mode}. In the replay mode, the inferior does not really execute code
7692 instructions. Instead, all the events that normally happen during
7693 code execution are taken from the execution log. While code is not
7694 really executed in replay mode, the values of registers (including the
7695 program counter register) and the memory of the inferior are still
7696 changed as they normally would. Their contents are taken from the
7700 If the record for the next instruction is not in the execution log,
7701 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7702 inferior executes normally, and @value{GDBN} records the execution log
7705 The process record and replay target supports reverse execution
7706 (@pxref{Reverse Execution}), even if the platform on which the
7707 inferior runs does not. However, the reverse execution is limited in
7708 this case by the range of the instructions recorded in the execution
7709 log. In other words, reverse execution on platforms that don't
7710 support it directly can only be done in the replay mode.
7712 When debugging in the reverse direction, @value{GDBN} will work in
7713 replay mode as long as the execution log includes the record for the
7714 previous instruction; otherwise, it will work in record mode, if the
7715 platform supports reverse execution, or stop if not.
7717 Currently, process record and replay is supported on ARM, Aarch64,
7718 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7719 GNU/Linux. Process record and replay can be used both when native
7720 debugging, and when remote debugging via @code{gdbserver}.
7722 For architecture environments that support process record and replay,
7723 @value{GDBN} provides the following commands:
7726 @kindex target record
7727 @kindex target record-full
7728 @kindex target record-btrace
7731 @kindex record btrace
7732 @kindex record btrace bts
7733 @kindex record btrace pt
7739 @kindex rec btrace bts
7740 @kindex rec btrace pt
7743 @item record @var{method}
7744 This command starts the process record and replay target. The
7745 recording method can be specified as parameter. Without a parameter
7746 the command uses the @code{full} recording method. The following
7747 recording methods are available:
7751 Full record/replay recording using @value{GDBN}'s software record and
7752 replay implementation. This method allows replaying and reverse
7755 @item btrace @var{format}
7756 Hardware-supported instruction recording, supported on Intel
7757 processors. This method does not record data. Further, the data is
7758 collected in a ring buffer so old data will be overwritten when the
7759 buffer is full. It allows limited reverse execution. Variables and
7760 registers are not available during reverse execution. In remote
7761 debugging, recording continues on disconnect. Recorded data can be
7762 inspected after reconnecting. The recording may be stopped using
7765 The recording format can be specified as parameter. Without a parameter
7766 the command chooses the recording format. The following recording
7767 formats are available:
7771 @cindex branch trace store
7772 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7773 this format, the processor stores a from/to record for each executed
7774 branch in the btrace ring buffer.
7777 @cindex Intel Processor Trace
7778 Use the @dfn{Intel Processor Trace} recording format. In this
7779 format, the processor stores the execution trace in a compressed form
7780 that is afterwards decoded by @value{GDBN}.
7782 The trace can be recorded with very low overhead. The compressed
7783 trace format also allows small trace buffers to already contain a big
7784 number of instructions compared to @acronym{BTS}.
7786 Decoding the recorded execution trace, on the other hand, is more
7787 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7788 increased number of instructions to process. You should increase the
7789 buffer-size with care.
7792 Not all recording formats may be available on all processors.
7795 The process record and replay target can only debug a process that is
7796 already running. Therefore, you need first to start the process with
7797 the @kbd{run} or @kbd{start} commands, and then start the recording
7798 with the @kbd{record @var{method}} command.
7800 @cindex displaced stepping, and process record and replay
7801 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7802 will be automatically disabled when process record and replay target
7803 is started. That's because the process record and replay target
7804 doesn't support displaced stepping.
7806 @cindex non-stop mode, and process record and replay
7807 @cindex asynchronous execution, and process record and replay
7808 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7809 the asynchronous execution mode (@pxref{Background Execution}), not
7810 all recording methods are available. The @code{full} recording method
7811 does not support these two modes.
7816 Stop the process record and replay target. When process record and
7817 replay target stops, the entire execution log will be deleted and the
7818 inferior will either be terminated, or will remain in its final state.
7820 When you stop the process record and replay target in record mode (at
7821 the end of the execution log), the inferior will be stopped at the
7822 next instruction that would have been recorded. In other words, if
7823 you record for a while and then stop recording, the inferior process
7824 will be left in the same state as if the recording never happened.
7826 On the other hand, if the process record and replay target is stopped
7827 while in replay mode (that is, not at the end of the execution log,
7828 but at some earlier point), the inferior process will become ``live''
7829 at that earlier state, and it will then be possible to continue the
7830 usual ``live'' debugging of the process from that state.
7832 When the inferior process exits, or @value{GDBN} detaches from it,
7833 process record and replay target will automatically stop itself.
7837 Go to a specific location in the execution log. There are several
7838 ways to specify the location to go to:
7841 @item record goto begin
7842 @itemx record goto start
7843 Go to the beginning of the execution log.
7845 @item record goto end
7846 Go to the end of the execution log.
7848 @item record goto @var{n}
7849 Go to instruction number @var{n} in the execution log.
7853 @item record save @var{filename}
7854 Save the execution log to a file @file{@var{filename}}.
7855 Default filename is @file{gdb_record.@var{process_id}}, where
7856 @var{process_id} is the process ID of the inferior.
7858 This command may not be available for all recording methods.
7860 @kindex record restore
7861 @item record restore @var{filename}
7862 Restore the execution log from a file @file{@var{filename}}.
7863 File must have been created with @code{record save}.
7865 @kindex set record full
7866 @item set record full insn-number-max @var{limit}
7867 @itemx set record full insn-number-max unlimited
7868 Set the limit of instructions to be recorded for the @code{full}
7869 recording method. Default value is 200000.
7871 If @var{limit} is a positive number, then @value{GDBN} will start
7872 deleting instructions from the log once the number of the record
7873 instructions becomes greater than @var{limit}. For every new recorded
7874 instruction, @value{GDBN} will delete the earliest recorded
7875 instruction to keep the number of recorded instructions at the limit.
7876 (Since deleting recorded instructions loses information, @value{GDBN}
7877 lets you control what happens when the limit is reached, by means of
7878 the @code{stop-at-limit} option, described below.)
7880 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7881 delete recorded instructions from the execution log. The number of
7882 recorded instructions is limited only by the available memory.
7884 @kindex show record full
7885 @item show record full insn-number-max
7886 Show the limit of instructions to be recorded with the @code{full}
7889 @item set record full stop-at-limit
7890 Control the behavior of the @code{full} recording method when the
7891 number of recorded instructions reaches the limit. If ON (the
7892 default), @value{GDBN} will stop when the limit is reached for the
7893 first time and ask you whether you want to stop the inferior or
7894 continue running it and recording the execution log. If you decide
7895 to continue recording, each new recorded instruction will cause the
7896 oldest one to be deleted.
7898 If this option is OFF, @value{GDBN} will automatically delete the
7899 oldest record to make room for each new one, without asking.
7901 @item show record full stop-at-limit
7902 Show the current setting of @code{stop-at-limit}.
7904 @item set record full memory-query
7905 Control the behavior when @value{GDBN} is unable to record memory
7906 changes caused by an instruction for the @code{full} recording method.
7907 If ON, @value{GDBN} will query whether to stop the inferior in that
7910 If this option is OFF (the default), @value{GDBN} will automatically
7911 ignore the effect of such instructions on memory. Later, when
7912 @value{GDBN} replays this execution log, it will mark the log of this
7913 instruction as not accessible, and it will not affect the replay
7916 @item show record full memory-query
7917 Show the current setting of @code{memory-query}.
7919 @kindex set record btrace
7920 The @code{btrace} record target does not trace data. As a
7921 convenience, when replaying, @value{GDBN} reads read-only memory off
7922 the live program directly, assuming that the addresses of the
7923 read-only areas don't change. This for example makes it possible to
7924 disassemble code while replaying, but not to print variables.
7925 In some cases, being able to inspect variables might be useful.
7926 You can use the following command for that:
7928 @item set record btrace replay-memory-access
7929 Control the behavior of the @code{btrace} recording method when
7930 accessing memory during replay. If @code{read-only} (the default),
7931 @value{GDBN} will only allow accesses to read-only memory.
7932 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7933 and to read-write memory. Beware that the accessed memory corresponds
7934 to the live target and not necessarily to the current replay
7937 @item set record btrace cpu @var{identifier}
7938 Set the processor to be used for enabling workarounds for processor
7939 errata when decoding the trace.
7941 Processor errata are defects in processor operation, caused by its
7942 design or manufacture. They can cause a trace not to match the
7943 specification. This, in turn, may cause trace decode to fail.
7944 @value{GDBN} can detect erroneous trace packets and correct them, thus
7945 avoiding the decoding failures. These corrections are known as
7946 @dfn{errata workarounds}, and are enabled based on the processor on
7947 which the trace was recorded.
7949 By default, @value{GDBN} attempts to detect the processor
7950 automatically, and apply the necessary workarounds for it. However,
7951 you may need to specify the processor if @value{GDBN} does not yet
7952 support it. This command allows you to do that, and also allows to
7953 disable the workarounds.
7955 The argument @var{identifier} identifies the @sc{cpu} and is of the
7956 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7957 there are two special identifiers, @code{none} and @code{auto}
7960 The following vendor identifiers and corresponding processor
7961 identifiers are currently supported:
7963 @multitable @columnfractions .1 .9
7966 @tab @var{family}/@var{model}[/@var{stepping}]
7970 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7971 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7973 If @var{identifier} is @code{auto}, enable errata workarounds for the
7974 processor on which the trace was recorded. If @var{identifier} is
7975 @code{none}, errata workarounds are disabled.
7977 For example, when using an old @value{GDBN} on a new system, decode
7978 may fail because @value{GDBN} does not support the new processor. It
7979 often suffices to specify an older processor that @value{GDBN}
7983 (@value{GDBP}) info record
7984 Active record target: record-btrace
7985 Recording format: Intel Processor Trace.
7987 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7988 (@value{GDBP}) set record btrace cpu intel:6/158
7989 (@value{GDBP}) info record
7990 Active record target: record-btrace
7991 Recording format: Intel Processor Trace.
7993 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7996 @kindex show record btrace
7997 @item show record btrace replay-memory-access
7998 Show the current setting of @code{replay-memory-access}.
8000 @item show record btrace cpu
8001 Show the processor to be used for enabling trace decode errata
8004 @kindex set record btrace bts
8005 @item set record btrace bts buffer-size @var{size}
8006 @itemx set record btrace bts buffer-size unlimited
8007 Set the requested ring buffer size for branch tracing in @acronym{BTS}
8008 format. Default is 64KB.
8010 If @var{size} is a positive number, then @value{GDBN} will try to
8011 allocate a buffer of at least @var{size} bytes for each new thread
8012 that uses the btrace recording method and the @acronym{BTS} format.
8013 The actually obtained buffer size may differ from the requested
8014 @var{size}. Use the @code{info record} command to see the actual
8015 buffer size for each thread that uses the btrace recording method and
8016 the @acronym{BTS} format.
8018 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
8019 allocate a buffer of 4MB.
8021 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
8022 also need longer to process the branch trace data before it can be used.
8024 @item show record btrace bts buffer-size @var{size}
8025 Show the current setting of the requested ring buffer size for branch
8026 tracing in @acronym{BTS} format.
8028 @kindex set record btrace pt
8029 @item set record btrace pt buffer-size @var{size}
8030 @itemx set record btrace pt buffer-size unlimited
8031 Set the requested ring buffer size for branch tracing in Intel
8032 Processor Trace format. Default is 16KB.
8034 If @var{size} is a positive number, then @value{GDBN} will try to
8035 allocate a buffer of at least @var{size} bytes for each new thread
8036 that uses the btrace recording method and the Intel Processor Trace
8037 format. The actually obtained buffer size may differ from the
8038 requested @var{size}. Use the @code{info record} command to see the
8039 actual buffer size for each thread.
8041 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
8042 allocate a buffer of 4MB.
8044 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
8045 also need longer to process the branch trace data before it can be used.
8047 @item show record btrace pt buffer-size @var{size}
8048 Show the current setting of the requested ring buffer size for branch
8049 tracing in Intel Processor Trace format.
8053 Show various statistics about the recording depending on the recording
8058 For the @code{full} recording method, it shows the state of process
8059 record and its in-memory execution log buffer, including:
8063 Whether in record mode or replay mode.
8065 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
8067 Highest recorded instruction number.
8069 Current instruction about to be replayed (if in replay mode).
8071 Number of instructions contained in the execution log.
8073 Maximum number of instructions that may be contained in the execution log.
8077 For the @code{btrace} recording method, it shows:
8083 Number of instructions that have been recorded.
8085 Number of blocks of sequential control-flow formed by the recorded
8088 Whether in record mode or replay mode.
8091 For the @code{bts} recording format, it also shows:
8094 Size of the perf ring buffer.
8097 For the @code{pt} recording format, it also shows:
8100 Size of the perf ring buffer.
8104 @kindex record delete
8107 When record target runs in replay mode (``in the past''), delete the
8108 subsequent execution log and begin to record a new execution log starting
8109 from the current address. This means you will abandon the previously
8110 recorded ``future'' and begin recording a new ``future''.
8112 @kindex record instruction-history
8113 @kindex rec instruction-history
8114 @item record instruction-history
8115 Disassembles instructions from the recorded execution log. By
8116 default, ten instructions are disassembled. This can be changed using
8117 the @code{set record instruction-history-size} command. Instructions
8118 are printed in execution order.
8120 It can also print mixed source+disassembly if you specify the the
8121 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
8122 as well as in symbolic form by specifying the @code{/r} or @code{/b}
8123 modifier. The behaviour of the @code{/m}, @code{/s}, @code{/r}, and
8124 @code{/b} modifiers are the same as for the @kbd{disassemble} command
8125 (@pxref{disassemble,,@kbd{disassemble}}).
8127 The current position marker is printed for the instruction at the
8128 current program counter value. This instruction can appear multiple
8129 times in the trace and the current position marker will be printed
8130 every time. To omit the current position marker, specify the
8133 To better align the printed instructions when the trace contains
8134 instructions from more than one function, the function name may be
8135 omitted by specifying the @code{/f} modifier.
8137 Speculatively executed instructions are prefixed with @samp{?}. This
8138 feature is not available for all recording formats.
8140 There are several ways to specify what part of the execution log to
8144 @item record instruction-history @var{insn}
8145 Disassembles ten instructions starting from instruction number
8148 @item record instruction-history @var{insn}, +/-@var{n}
8149 Disassembles @var{n} instructions around instruction number
8150 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
8151 @var{n} instructions after instruction number @var{insn}. If
8152 @var{n} is preceded with @code{-}, disassembles @var{n}
8153 instructions before instruction number @var{insn}.
8155 @item record instruction-history
8156 Disassembles ten more instructions after the last disassembly.
8158 @item record instruction-history -
8159 Disassembles ten more instructions before the last disassembly.
8161 @item record instruction-history @var{begin}, @var{end}
8162 Disassembles instructions beginning with instruction number
8163 @var{begin} until instruction number @var{end}. The instruction
8164 number @var{end} is included.
8167 This command may not be available for all recording methods.
8170 @item set record instruction-history-size @var{size}
8171 @itemx set record instruction-history-size unlimited
8172 Define how many instructions to disassemble in the @code{record
8173 instruction-history} command. The default value is 10.
8174 A @var{size} of @code{unlimited} means unlimited instructions.
8177 @item show record instruction-history-size
8178 Show how many instructions to disassemble in the @code{record
8179 instruction-history} command.
8181 @kindex record function-call-history
8182 @kindex rec function-call-history
8183 @item record function-call-history
8184 Prints the execution history at function granularity. For each sequence
8185 of instructions that belong to the same function, it prints the name of
8186 that function, the source lines for this instruction sequence (if the
8187 @code{/l} modifier is specified), and the instructions numbers that form
8188 the sequence (if the @code{/i} modifier is specified). The function names
8189 are indented to reflect the call stack depth if the @code{/c} modifier is
8190 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
8194 (@value{GDBP}) @b{list 1, 10}
8205 (@value{GDBP}) @b{record function-call-history /ilc}
8206 1 bar inst 1,4 at foo.c:6,8
8207 2 foo inst 5,10 at foo.c:2,3
8208 3 bar inst 11,13 at foo.c:9,10
8211 By default, ten functions are printed. This can be changed using the
8212 @code{set record function-call-history-size} command. Functions are
8213 printed in execution order. There are several ways to specify what
8217 @item record function-call-history @var{func}
8218 Prints ten functions starting from function number @var{func}.
8220 @item record function-call-history @var{func}, +/-@var{n}
8221 Prints @var{n} functions around function number @var{func}. If
8222 @var{n} is preceded with @code{+}, prints @var{n} functions after
8223 function number @var{func}. If @var{n} is preceded with @code{-},
8224 prints @var{n} functions before function number @var{func}.
8226 @item record function-call-history
8227 Prints ten more functions after the last ten-function print.
8229 @item record function-call-history -
8230 Prints ten more functions before the last ten-function print.
8232 @item record function-call-history @var{begin}, @var{end}
8233 Prints functions beginning with function number @var{begin} until
8234 function number @var{end}. The function number @var{end} is included.
8237 This command may not be available for all recording methods.
8239 @item set record function-call-history-size @var{size}
8240 @itemx set record function-call-history-size unlimited
8241 Define how many functions to print in the
8242 @code{record function-call-history} command. The default value is 10.
8243 A size of @code{unlimited} means unlimited functions.
8245 @item show record function-call-history-size
8246 Show how many functions to print in the
8247 @code{record function-call-history} command.
8252 @chapter Examining the Stack
8254 When your program has stopped, the first thing you need to know is where it
8255 stopped and how it got there.
8258 Each time your program performs a function call, information about the call
8260 That information includes the location of the call in your program,
8261 the arguments of the call,
8262 and the local variables of the function being called.
8263 The information is saved in a block of data called a @dfn{stack frame}.
8264 The stack frames are allocated in a region of memory called the @dfn{call
8267 When your program stops, the @value{GDBN} commands for examining the
8268 stack allow you to see all of this information.
8270 @cindex selected frame
8271 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8272 @value{GDBN} commands refer implicitly to the selected frame. In
8273 particular, whenever you ask @value{GDBN} for the value of a variable in
8274 your program, the value is found in the selected frame. There are
8275 special @value{GDBN} commands to select whichever frame you are
8276 interested in. @xref{Selection, ,Selecting a Frame}.
8278 When your program stops, @value{GDBN} automatically selects the
8279 currently executing frame and describes it briefly, similar to the
8280 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8283 * Frames:: Stack frames
8284 * Backtrace:: Backtraces
8285 * Selection:: Selecting a frame
8286 * Frame Info:: Information on a frame
8287 * Frame Apply:: Applying a command to several frames
8288 * Frame Filter Management:: Managing frame filters
8293 @section Stack Frames
8295 @cindex frame, definition
8297 The call stack is divided up into contiguous pieces called @dfn{stack
8298 frames}, or @dfn{frames} for short; each frame is the data associated
8299 with one call to one function. The frame contains the arguments given
8300 to the function, the function's local variables, and the address at
8301 which the function is executing.
8303 @cindex initial frame
8304 @cindex outermost frame
8305 @cindex innermost frame
8306 When your program is started, the stack has only one frame, that of the
8307 function @code{main}. This is called the @dfn{initial} frame or the
8308 @dfn{outermost} frame. Each time a function is called, a new frame is
8309 made. Each time a function returns, the frame for that function invocation
8310 is eliminated. If a function is recursive, there can be many frames for
8311 the same function. The frame for the function in which execution is
8312 actually occurring is called the @dfn{innermost} frame. This is the most
8313 recently created of all the stack frames that still exist.
8315 @cindex frame pointer
8316 Inside your program, stack frames are identified by their addresses. A
8317 stack frame consists of many bytes, each of which has its own address; each
8318 kind of computer has a convention for choosing one byte whose
8319 address serves as the address of the frame. Usually this address is kept
8320 in a register called the @dfn{frame pointer register}
8321 (@pxref{Registers, $fp}) while execution is going on in that frame.
8324 @cindex frame number
8325 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8326 number that is zero for the innermost frame, one for the frame that
8327 called it, and so on upward. These level numbers give you a way of
8328 designating stack frames in @value{GDBN} commands. The terms
8329 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8330 describe this number.
8332 @c The -fomit-frame-pointer below perennially causes hbox overflow
8333 @c underflow problems.
8334 @cindex frameless execution
8335 Some compilers provide a way to compile functions so that they operate
8336 without stack frames. (For example, the @value{NGCC} option
8338 @samp{-fomit-frame-pointer}
8340 generates functions without a frame.)
8341 This is occasionally done with heavily used library functions to save
8342 the frame setup time. @value{GDBN} has limited facilities for dealing
8343 with these function invocations. If the innermost function invocation
8344 has no stack frame, @value{GDBN} nevertheless regards it as though
8345 it had a separate frame, which is numbered zero as usual, allowing
8346 correct tracing of the function call chain. However, @value{GDBN} has
8347 no provision for frameless functions elsewhere in the stack.
8353 @cindex call stack traces
8354 A backtrace is a summary of how your program got where it is. It shows one
8355 line per frame, for many frames, starting with the currently executing
8356 frame (frame zero), followed by its caller (frame one), and on up the
8359 @anchor{backtrace-command}
8361 @kindex bt @r{(@code{backtrace})}
8362 To print a backtrace of the entire stack, use the @code{backtrace}
8363 command, or its alias @code{bt}. This command will print one line per
8364 frame for frames in the stack. By default, all stack frames are
8365 printed. You can stop the backtrace at any time by typing the system
8366 interrupt character, normally @kbd{Ctrl-c}.
8369 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8370 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8371 Print the backtrace of the entire stack.
8373 The optional @var{count} can be one of the following:
8378 Print only the innermost @var{n} frames, where @var{n} is a positive
8383 Print only the outermost @var{n} frames, where @var{n} is a positive
8391 Print the values of the local variables also. This can be combined
8392 with the optional @var{count} to limit the number of frames shown.
8395 Do not run Python frame filters on this backtrace. @xref{Frame
8396 Filter API}, for more information. Additionally use @ref{disable
8397 frame-filter all} to turn off all frame filters. This is only
8398 relevant when @value{GDBN} has been configured with @code{Python}
8402 A Python frame filter might decide to ``elide'' some frames. Normally
8403 such elided frames are still printed, but they are indented relative
8404 to the filtered frames that cause them to be elided. The @code{-hide}
8405 option causes elided frames to not be printed at all.
8408 The @code{backtrace} command also supports a number of options that
8409 allow overriding relevant global print settings as set by @code{set
8410 backtrace} and @code{set print} subcommands:
8413 @item -past-main [@code{on}|@code{off}]
8414 Set whether backtraces should continue past @code{main}. Related setting:
8415 @ref{set backtrace past-main}.
8417 @item -past-entry [@code{on}|@code{off}]
8418 Set whether backtraces should continue past the entry point of a program.
8419 Related setting: @ref{set backtrace past-entry}.
8421 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8422 Set printing of function arguments at function entry.
8423 Related setting: @ref{set print entry-values}.
8425 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8426 Set printing of non-scalar frame arguments.
8427 Related setting: @ref{set print frame-arguments}.
8429 @item -raw-frame-arguments [@code{on}|@code{off}]
8430 Set whether to print frame arguments in raw form.
8431 Related setting: @ref{set print raw-frame-arguments}.
8433 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8434 Set printing of frame information.
8435 Related setting: @ref{set print frame-info}.
8438 The optional @var{qualifier} is maintained for backward compatibility.
8439 It can be one of the following:
8443 Equivalent to the @code{-full} option.
8446 Equivalent to the @code{-no-filters} option.
8449 Equivalent to the @code{-hide} option.
8456 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8457 are additional aliases for @code{backtrace}.
8459 @cindex multiple threads, backtrace
8460 In a multi-threaded program, @value{GDBN} by default shows the
8461 backtrace only for the current thread. To display the backtrace for
8462 several or all of the threads, use the command @code{thread apply}
8463 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8464 apply all backtrace}, @value{GDBN} will display the backtrace for all
8465 the threads; this is handy when you debug a core dump of a
8466 multi-threaded program.
8468 Each line in the backtrace shows the frame number and the function name.
8469 The program counter value is also shown---unless you use @code{set
8470 print address off}. The backtrace also shows the source file name and
8471 line number, as well as the arguments to the function. The program
8472 counter value is omitted if it is at the beginning of the code for that
8475 Here is an example of a backtrace. It was made with the command
8476 @samp{bt 3}, so it shows the innermost three frames.
8480 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8482 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8483 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8485 (More stack frames follow...)
8490 The display for frame zero does not begin with a program counter
8491 value, indicating that your program has stopped at the beginning of the
8492 code for line @code{993} of @code{builtin.c}.
8495 The value of parameter @code{data} in frame 1 has been replaced by
8496 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8497 only if it is a scalar (integer, pointer, enumeration, etc). See command
8498 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8499 on how to configure the way function parameter values are printed.
8500 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8501 what frame information is printed.
8503 @cindex optimized out, in backtrace
8504 @cindex function call arguments, optimized out
8505 If your program was compiled with optimizations, some compilers will
8506 optimize away arguments passed to functions if those arguments are
8507 never used after the call. Such optimizations generate code that
8508 passes arguments through registers, but doesn't store those arguments
8509 in the stack frame. @value{GDBN} has no way of displaying such
8510 arguments in stack frames other than the innermost one. Here's what
8511 such a backtrace might look like:
8515 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8517 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8518 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8520 (More stack frames follow...)
8525 The values of arguments that were not saved in their stack frames are
8526 shown as @samp{<optimized out>}.
8528 If you need to display the values of such optimized-out arguments,
8529 either deduce that from other variables whose values depend on the one
8530 you are interested in, or recompile without optimizations.
8532 @cindex backtrace beyond @code{main} function
8533 @cindex program entry point
8534 @cindex startup code, and backtrace
8535 Most programs have a standard user entry point---a place where system
8536 libraries and startup code transition into user code. For C this is
8537 @code{main}@footnote{
8538 Note that embedded programs (the so-called ``free-standing''
8539 environment) are not required to have a @code{main} function as the
8540 entry point. They could even have multiple entry points.}.
8541 When @value{GDBN} finds the entry function in a backtrace
8542 it will terminate the backtrace, to avoid tracing into highly
8543 system-specific (and generally uninteresting) code.
8545 If you need to examine the startup code, or limit the number of levels
8546 in a backtrace, you can change this behavior:
8549 @item set backtrace past-main
8550 @itemx set backtrace past-main on
8551 @anchor{set backtrace past-main}
8552 @kindex set backtrace
8553 Backtraces will continue past the user entry point.
8555 @item set backtrace past-main off
8556 Backtraces will stop when they encounter the user entry point. This is the
8559 @item show backtrace past-main
8560 @kindex show backtrace
8561 Display the current user entry point backtrace policy.
8563 @item set backtrace past-entry
8564 @itemx set backtrace past-entry on
8565 @anchor{set backtrace past-entry}
8566 Backtraces will continue past the internal entry point of an application.
8567 This entry point is encoded by the linker when the application is built,
8568 and is likely before the user entry point @code{main} (or equivalent) is called.
8570 @item set backtrace past-entry off
8571 Backtraces will stop when they encounter the internal entry point of an
8572 application. This is the default.
8574 @item show backtrace past-entry
8575 Display the current internal entry point backtrace policy.
8577 @item set backtrace limit @var{n}
8578 @itemx set backtrace limit 0
8579 @itemx set backtrace limit unlimited
8580 @anchor{set backtrace limit}
8581 @cindex backtrace limit
8582 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8583 or zero means unlimited levels.
8585 @item show backtrace limit
8586 Display the current limit on backtrace levels.
8589 You can control how file names are displayed.
8592 @item set filename-display
8593 @itemx set filename-display relative
8594 @cindex filename-display
8595 Display file names relative to the compilation directory. This is the default.
8597 @item set filename-display basename
8598 Display only basename of a filename.
8600 @item set filename-display absolute
8601 Display an absolute filename.
8603 @item show filename-display
8604 Show the current way to display filenames.
8608 @section Selecting a Frame
8610 Most commands for examining the stack and other data in your program work on
8611 whichever stack frame is selected at the moment. Here are the commands for
8612 selecting a stack frame; all of them finish by printing a brief description
8613 of the stack frame just selected.
8616 @kindex frame@r{, selecting}
8617 @kindex f @r{(@code{frame})}
8618 @item frame @r{[} @var{frame-selection-spec} @r{]}
8619 @item f @r{[} @var{frame-selection-spec} @r{]}
8620 The @command{frame} command allows different stack frames to be
8621 selected. The @var{frame-selection-spec} can be any of the following:
8626 @item level @var{num}
8627 Select frame level @var{num}. Recall that frame zero is the innermost
8628 (currently executing) frame, frame one is the frame that called the
8629 innermost one, and so on. The highest level frame is usually the one
8632 As this is the most common method of navigating the frame stack, the
8633 string @command{level} can be omitted. For example, the following two
8634 commands are equivalent:
8637 (@value{GDBP}) frame 3
8638 (@value{GDBP}) frame level 3
8641 @kindex frame address
8642 @item address @var{stack-address}
8643 Select the frame with stack address @var{stack-address}. The
8644 @var{stack-address} for a frame can be seen in the output of
8645 @command{info frame}, for example:
8648 (@value{GDBP}) info frame
8649 Stack level 1, frame at 0x7fffffffda30:
8650 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8651 tail call frame, caller of frame at 0x7fffffffda30
8652 source language c++.
8653 Arglist at unknown address.
8654 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8657 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8658 indicated by the line:
8661 Stack level 1, frame at 0x7fffffffda30:
8664 @kindex frame function
8665 @item function @var{function-name}
8666 Select the stack frame for function @var{function-name}. If there are
8667 multiple stack frames for function @var{function-name} then the inner
8668 most stack frame is selected.
8671 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8672 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8673 viewed has stack address @var{stack-addr}, and optionally, a program
8674 counter address of @var{pc-addr}.
8676 This is useful mainly if the chaining of stack frames has been
8677 damaged by a bug, making it impossible for @value{GDBN} to assign
8678 numbers properly to all frames. In addition, this can be useful
8679 when your program has multiple stacks and switches between them.
8681 When viewing a frame outside the current backtrace using
8682 @command{frame view} then you can always return to the original
8683 stack using one of the previous stack frame selection instructions,
8684 for example @command{frame level 0}.
8690 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8691 numbers @var{n}, this advances toward the outermost frame, to higher
8692 frame numbers, to frames that have existed longer.
8695 @kindex do @r{(@code{down})}
8697 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8698 positive numbers @var{n}, this advances toward the innermost frame, to
8699 lower frame numbers, to frames that were created more recently.
8700 You may abbreviate @code{down} as @code{do}.
8703 All of these commands end by printing two lines of output describing the
8704 frame. The first line shows the frame number, the function name, the
8705 arguments, and the source file and line number of execution in that
8706 frame. The second line shows the text of that source line.
8714 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8716 10 read_input_file (argv[i]);
8720 After such a printout, the @code{list} command with no arguments
8721 prints ten lines centered on the point of execution in the frame.
8722 You can also edit the program at the point of execution with your favorite
8723 editing program by typing @code{edit}.
8724 @xref{List, ,Printing Source Lines},
8728 @kindex select-frame
8729 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8730 The @code{select-frame} command is a variant of @code{frame} that does
8731 not display the new frame after selecting it. This command is
8732 intended primarily for use in @value{GDBN} command scripts, where the
8733 output might be unnecessary and distracting. The
8734 @var{frame-selection-spec} is as for the @command{frame} command
8735 described in @ref{Selection, ,Selecting a Frame}.
8737 @kindex down-silently
8739 @item up-silently @var{n}
8740 @itemx down-silently @var{n}
8741 These two commands are variants of @code{up} and @code{down},
8742 respectively; they differ in that they do their work silently, without
8743 causing display of the new frame. They are intended primarily for use
8744 in @value{GDBN} command scripts, where the output might be unnecessary and
8749 @section Information About a Frame
8751 There are several other commands to print information about the selected
8757 When used without any argument, this command does not change which
8758 frame is selected, but prints a brief description of the currently
8759 selected stack frame. It can be abbreviated @code{f}. With an
8760 argument, this command is used to select a stack frame.
8761 @xref{Selection, ,Selecting a Frame}.
8764 @kindex info f @r{(@code{info frame})}
8767 This command prints a verbose description of the selected stack frame,
8772 the address of the frame
8774 the address of the next frame down (called by this frame)
8776 the address of the next frame up (caller of this frame)
8778 the language in which the source code corresponding to this frame is written
8780 the address of the frame's arguments
8782 the address of the frame's local variables
8784 the program counter saved in it (the address of execution in the caller frame)
8786 which registers were saved in the frame
8789 @noindent The verbose description is useful when
8790 something has gone wrong that has made the stack format fail to fit
8791 the usual conventions.
8793 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8794 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8795 Print a verbose description of the frame selected by
8796 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8797 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8798 a Frame}). The selected frame remains unchanged by this command.
8801 @item info args [-q]
8802 Print the arguments of the selected frame, each on a separate line.
8804 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8805 printing header information and messages explaining why no argument
8808 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8809 Like @kbd{info args}, but only print the arguments selected
8810 with the provided regexp(s).
8812 If @var{regexp} is provided, print only the arguments whose names
8813 match the regular expression @var{regexp}.
8815 If @var{type_regexp} is provided, print only the arguments whose
8816 types, as printed by the @code{whatis} command, match
8817 the regular expression @var{type_regexp}.
8818 If @var{type_regexp} contains space(s), it should be enclosed in
8819 quote characters. If needed, use backslash to escape the meaning
8820 of special characters or quotes.
8822 If both @var{regexp} and @var{type_regexp} are provided, an argument
8823 is printed only if its name matches @var{regexp} and its type matches
8826 @item info locals [-q]
8828 Print the local variables of the selected frame, each on a separate
8829 line. These are all variables (declared either static or automatic)
8830 accessible at the point of execution of the selected frame.
8832 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8833 printing header information and messages explaining why no local variables
8836 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8837 Like @kbd{info locals}, but only print the local variables selected
8838 with the provided regexp(s).
8840 If @var{regexp} is provided, print only the local variables whose names
8841 match the regular expression @var{regexp}.
8843 If @var{type_regexp} is provided, print only the local variables whose
8844 types, as printed by the @code{whatis} command, match
8845 the regular expression @var{type_regexp}.
8846 If @var{type_regexp} contains space(s), it should be enclosed in
8847 quote characters. If needed, use backslash to escape the meaning
8848 of special characters or quotes.
8850 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8851 is printed only if its name matches @var{regexp} and its type matches
8854 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8855 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8856 For example, your program might use Resource Acquisition Is
8857 Initialization types (RAII) such as @code{lock_something_t}: each
8858 local variable of type @code{lock_something_t} automatically places a
8859 lock that is destroyed when the variable goes out of scope. You can
8860 then list all acquired locks in your program by doing
8862 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8865 or the equivalent shorter form
8867 tfaas i lo -q -t lock_something_t
8873 @section Applying a Command to Several Frames.
8875 @cindex apply command to several frames
8877 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8878 The @code{frame apply} command allows you to apply the named
8879 @var{command} to one or more frames.
8883 Specify @code{all} to apply @var{command} to all frames.
8886 Use @var{count} to apply @var{command} to the innermost @var{count}
8887 frames, where @var{count} is a positive number.
8890 Use @var{-count} to apply @var{command} to the outermost @var{count}
8891 frames, where @var{count} is a positive number.
8894 Use @code{level} to apply @var{command} to the set of frames identified
8895 by the @var{level} list. @var{level} is a frame level or a range of frame
8896 levels as @var{level1}-@var{level2}. The frame level is the number shown
8897 in the first field of the @samp{backtrace} command output.
8898 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8899 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8903 Note that the frames on which @code{frame apply} applies a command are
8904 also influenced by the @code{set backtrace} settings such as @code{set
8905 backtrace past-main} and @code{set backtrace limit N}.
8906 @xref{Backtrace,,Backtraces}.
8908 The @code{frame apply} command also supports a number of options that
8909 allow overriding relevant @code{set backtrace} settings:
8912 @item -past-main [@code{on}|@code{off}]
8913 Whether backtraces should continue past @code{main}.
8914 Related setting: @ref{set backtrace past-main}.
8916 @item -past-entry [@code{on}|@code{off}]
8917 Whether backtraces should continue past the entry point of a program.
8918 Related setting: @ref{set backtrace past-entry}.
8921 By default, @value{GDBN} displays some frame information before the
8922 output produced by @var{command}, and an error raised during the
8923 execution of a @var{command} will abort @code{frame apply}. The
8924 following options can be used to fine-tune these behaviors:
8928 The flag @code{-c}, which stands for @samp{continue}, causes any
8929 errors in @var{command} to be displayed, and the execution of
8930 @code{frame apply} then continues.
8932 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8933 or empty output produced by a @var{command} to be silently ignored.
8934 That is, the execution continues, but the frame information and errors
8937 The flag @code{-q} (@samp{quiet}) disables printing the frame
8941 The following example shows how the flags @code{-c} and @code{-s} are
8942 working when applying the command @code{p j} to all frames, where
8943 variable @code{j} can only be successfully printed in the outermost
8944 @code{#1 main} frame.
8948 (@value{GDBP}) frame apply all p j
8949 #0 some_function (i=5) at fun.c:4
8950 No symbol "j" in current context.
8951 (@value{GDBP}) frame apply all -c p j
8952 #0 some_function (i=5) at fun.c:4
8953 No symbol "j" in current context.
8954 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8956 (@value{GDBP}) frame apply all -s p j
8957 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8963 By default, @samp{frame apply}, prints the frame location
8964 information before the command output:
8968 (@value{GDBP}) frame apply all p $sp
8969 #0 some_function (i=5) at fun.c:4
8970 $4 = (void *) 0xffffd1e0
8971 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8972 $5 = (void *) 0xffffd1f0
8977 If the flag @code{-q} is given, no frame information is printed:
8980 (@value{GDBP}) frame apply all -q p $sp
8981 $12 = (void *) 0xffffd1e0
8982 $13 = (void *) 0xffffd1f0
8992 @cindex apply a command to all frames (ignoring errors and empty output)
8993 @item faas @var{command}
8994 Shortcut for @code{frame apply all -s @var{command}}.
8995 Applies @var{command} on all frames, ignoring errors and empty output.
8997 It can for example be used to print a local variable or a function
8998 argument without knowing the frame where this variable or argument
9001 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
9004 The @code{faas} command accepts the same options as the @code{frame
9005 apply} command. @xref{Frame Apply,,frame apply}.
9007 Note that the command @code{tfaas @var{command}} applies @var{command}
9008 on all frames of all threads. See @xref{Threads,,Threads}.
9012 @node Frame Filter Management
9013 @section Management of Frame Filters.
9014 @cindex managing frame filters
9016 Frame filters are Python based utilities to manage and decorate the
9017 output of frames. @xref{Frame Filter API}, for further information.
9019 Managing frame filters is performed by several commands available
9020 within @value{GDBN}, detailed here.
9023 @kindex info frame-filter
9024 @item info frame-filter
9025 Print a list of installed frame filters from all dictionaries, showing
9026 their name, priority and enabled status.
9028 @kindex disable frame-filter
9029 @anchor{disable frame-filter all}
9030 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
9031 Disable a frame filter in the dictionary matching
9032 @var{filter-dictionary} and @var{filter-name}. The
9033 @var{filter-dictionary} may be @code{all}, @code{global},
9034 @code{progspace}, or the name of the object file where the frame filter
9035 dictionary resides. When @code{all} is specified, all frame filters
9036 across all dictionaries are disabled. The @var{filter-name} is the name
9037 of the frame filter and is used when @code{all} is not the option for
9038 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
9039 may be enabled again later.
9041 @kindex enable frame-filter
9042 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
9043 Enable a frame filter in the dictionary matching
9044 @var{filter-dictionary} and @var{filter-name}. The
9045 @var{filter-dictionary} may be @code{all}, @code{global},
9046 @code{progspace} or the name of the object file where the frame filter
9047 dictionary resides. When @code{all} is specified, all frame filters across
9048 all dictionaries are enabled. The @var{filter-name} is the name of the frame
9049 filter and is used when @code{all} is not the option for
9050 @var{filter-dictionary}.
9055 (@value{GDBP}) info frame-filter
9057 global frame-filters:
9058 Priority Enabled Name
9059 1000 No PrimaryFunctionFilter
9062 progspace /build/test frame-filters:
9063 Priority Enabled Name
9064 100 Yes ProgspaceFilter
9066 objfile /build/test frame-filters:
9067 Priority Enabled Name
9068 999 Yes BuildProgramFilter
9070 (@value{GDBP}) disable frame-filter /build/test BuildProgramFilter
9071 (@value{GDBP}) info frame-filter
9073 global frame-filters:
9074 Priority Enabled Name
9075 1000 No PrimaryFunctionFilter
9078 progspace /build/test frame-filters:
9079 Priority Enabled Name
9080 100 Yes ProgspaceFilter
9082 objfile /build/test frame-filters:
9083 Priority Enabled Name
9084 999 No BuildProgramFilter
9086 (@value{GDBP}) enable frame-filter global PrimaryFunctionFilter
9087 (@value{GDBP}) info frame-filter
9089 global frame-filters:
9090 Priority Enabled Name
9091 1000 Yes PrimaryFunctionFilter
9094 progspace /build/test frame-filters:
9095 Priority Enabled Name
9096 100 Yes ProgspaceFilter
9098 objfile /build/test frame-filters:
9099 Priority Enabled Name
9100 999 No BuildProgramFilter
9103 @kindex set frame-filter priority
9104 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
9105 Set the @var{priority} of a frame filter in the dictionary matching
9106 @var{filter-dictionary}, and the frame filter name matching
9107 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9108 @code{progspace} or the name of the object file where the frame filter
9109 dictionary resides. The @var{priority} is an integer.
9111 @kindex show frame-filter priority
9112 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
9113 Show the @var{priority} of a frame filter in the dictionary matching
9114 @var{filter-dictionary}, and the frame filter name matching
9115 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9116 @code{progspace} or the name of the object file where the frame filter
9122 (@value{GDBP}) info frame-filter
9124 global frame-filters:
9125 Priority Enabled Name
9126 1000 Yes PrimaryFunctionFilter
9129 progspace /build/test frame-filters:
9130 Priority Enabled Name
9131 100 Yes ProgspaceFilter
9133 objfile /build/test frame-filters:
9134 Priority Enabled Name
9135 999 No BuildProgramFilter
9137 (@value{GDBP}) set frame-filter priority global Reverse 50
9138 (@value{GDBP}) info frame-filter
9140 global frame-filters:
9141 Priority Enabled Name
9142 1000 Yes PrimaryFunctionFilter
9145 progspace /build/test frame-filters:
9146 Priority Enabled Name
9147 100 Yes ProgspaceFilter
9149 objfile /build/test frame-filters:
9150 Priority Enabled Name
9151 999 No BuildProgramFilter
9156 @chapter Examining Source Files
9158 @value{GDBN} can print parts of your program's source, since the debugging
9159 information recorded in the program tells @value{GDBN} what source files were
9160 used to build it. When your program stops, @value{GDBN} spontaneously prints
9161 the line where it stopped. Likewise, when you select a stack frame
9162 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
9163 execution in that frame has stopped. You can print other portions of
9164 source files by explicit command.
9166 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
9167 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
9168 @value{GDBN} under @sc{gnu} Emacs}.
9171 * List:: Printing source lines
9172 * Location Specifications:: How to specify code locations
9173 * Edit:: Editing source files
9174 * Search:: Searching source files
9175 * Source Path:: Specifying source directories
9176 * Machine Code:: Source and machine code
9177 * Disable Reading Source:: Disable Reading Source Code
9181 @section Printing Source Lines
9184 @kindex l @r{(@code{list})}
9185 To print lines from a source file, use the @code{list} command
9186 (abbreviated @code{l}). By default, ten lines are printed.
9187 There are several ways to specify what part of the file you want to
9188 print; see @ref{Location Specifications}, for the full list.
9190 Here are the forms of the @code{list} command most commonly used:
9193 @item list @var{linenum}
9194 Print lines centered around line number @var{linenum} in the
9195 current source file.
9197 @item list @var{function}
9198 Print lines centered around the beginning of function
9202 Print more lines. If the last lines printed were printed with a
9203 @code{list} command, this prints lines following the last lines
9204 printed; however, if the last line printed was a solitary line printed
9205 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9206 Stack}), this prints lines centered around that line. If no
9207 @code{list} command has been used and no solitary line was printed,
9208 it prints the lines around the function @code{main}.
9211 Same as using with no arguments.
9214 Print lines just before the lines last printed.
9217 Print the lines surrounding the point of execution within the
9218 currently selected frame. If the inferior is not running, print lines
9219 around the start of the main function instead.
9222 @cindex @code{list}, how many lines to display
9223 By default, @value{GDBN} prints ten source lines with any of these forms of
9224 the @code{list} command. You can change this using @code{set listsize}:
9227 @kindex set listsize
9228 @item set listsize @var{count}
9229 @itemx set listsize unlimited
9230 Make the @code{list} command display @var{count} source lines (unless
9231 the @code{list} argument explicitly specifies some other number).
9232 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9234 @kindex show listsize
9236 Display the number of lines that @code{list} prints.
9239 Repeating a @code{list} command with @key{RET} discards the argument,
9240 so it is equivalent to typing just @code{list}. This is more useful
9241 than listing the same lines again. An exception is made for an
9242 argument of @samp{-}; that argument is preserved in repetition so that
9243 each repetition moves up in the source file.
9245 In general, the @code{list} command expects you to supply zero, one or
9246 two location specs. These location specs are interpreted to resolve
9247 to source code lines; there are several ways of writing them
9248 (@pxref{Location Specifications}), but the effect is always to resolve
9249 to some source lines to display.
9251 Here is a complete description of the possible arguments for @code{list}:
9254 @item list @var{locspec}
9255 Print lines centered around the line or lines of all the code
9256 locations that result from resolving @var{locspec}.
9258 @item list @var{first},@var{last}
9259 Print lines from @var{first} to @var{last}. Both arguments are
9260 location specs. When a @code{list} command has two location specs,
9261 and the source file of the second location spec is omitted, this
9262 refers to the same source file as the first location spec. If either
9263 @var{first} or @var{last} resolve to more than one source line in the
9264 program, then the list command shows the list of resolved source
9265 lines and does not proceed with the source code listing.
9267 @item list ,@var{last}
9268 Print lines ending with @var{last}.
9270 Likewise, if @var{last} resolves to more than one source line in the
9271 program, then the list command prints the list of resolved source
9272 lines and does not proceed with the source code listing.
9274 @item list @var{first},
9275 Print lines starting with @var{first}.
9278 Print lines just after the lines last printed.
9281 Print lines just before the lines last printed.
9284 As described in the preceding table.
9287 @node Location Specifications
9288 @section Location Specifications
9289 @cindex specifying location
9291 @cindex source location
9292 @cindex code location
9294 @cindex location spec
9295 Several @value{GDBN} commands accept arguments that specify a location
9296 or locations of your program's code. Many times locations are
9297 specified using a source line number, but they can also be specified
9298 by a function name, an address, a label, etc. The different
9299 forms of specifying a location that @value{GDBN} recognizes are
9300 collectively known as forms of @dfn{location specification}, or
9301 @dfn{location spec}. This section documents the forms of specifying
9302 locations that @value{GDBN} recognizes.
9304 @cindex location resolution
9305 @cindex resolution of location spec
9306 When you specify a location, @value{GDBN} needs to find the place in
9307 your program, known as @dfn{code location}, that corresponds to the
9308 given location spec. We call this process of finding actual code
9309 locations corresponding to a location spec @dfn{location resolution}.
9311 A concrete code location in your program is uniquely identifiable by a
9312 set of several attributes: its source line number, the name of its
9313 source file, the fully-qualified and prototyped function in which it
9314 is defined, and an instruction address. Because each inferior has its
9315 own address space, the inferior number is also a necessary part of
9318 By contrast, location specs you type will many times omit some of
9319 these attributes. For example, it is customary to specify just the
9320 source line number to mean a line in the current source file, or
9321 specify just the basename of the file, omitting its directories. In
9322 other words, a location spec is usually incomplete, a kind of
9323 blueprint, and @value{GDBN} needs to complete the missing attributes
9324 by using the implied defaults, and by considering the source code and
9325 the debug information available to it. This is what location
9326 resolution is about.
9328 The resolution of an incomplete location spec can produce more than a
9329 single code location, if the spec doesn't allow distinguishing between
9330 them. Here are some examples of situations that result in a location
9331 spec matching multiple code locations in your program:
9335 The location spec specifies a function name, and there are several
9336 functions in the program which have that name. (To distinguish
9337 between them, you can specify a fully-qualified and prototyped
9338 function name, such as @code{A::func(int)} instead of just
9342 The location spec specifies a source file name, and there are several
9343 source files in the program that share the same name, for example
9344 several files with the same basename in different subdirectories. (To
9345 distinguish between them, specify enough leading directories with the
9349 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9350 instances of the function body, used in different cases, but their
9351 source-level names are identical.
9354 For a C@t{++} template function, a given line in the function can
9355 correspond to any number of instantiations.
9358 For an inlined function, a given source line can correspond to several
9359 actual code locations with that function's inlined code.
9362 Resolution of a location spec can also fail to produce a complete code
9363 location, or even fail to produce any code location. Here are some
9364 examples of such situations:
9368 Some parts of the program lack detailed enough debug info, so the
9369 resolved code location lacks some attributes, like source file name
9370 and line number, leaving just the instruction address and perhaps also
9371 a function name. Such an incomplete code location is only usable in
9372 contexts that work with addresses and/or function names. Some
9373 commands can only work with complete code locations.
9376 The location spec specifies a function name, and there are no
9377 functions in the program by that name, or they only exist in a
9378 yet-unloaded shared library.
9381 The location spec specifies a source file name, and there are no
9382 source files in the program by that name, or they only exist in a
9383 yet-unloaded shared library.
9386 The location spec specifies both a source file name and a source line
9387 number, and even though there are source files in the program that
9388 match the file name, none of those files has the specified line
9392 Locations may be specified using three different formats: linespec
9393 locations, explicit locations, or address locations. The following
9394 subsections describe these formats.
9397 * Linespec Locations:: Linespec locations
9398 * Explicit Locations:: Explicit locations
9399 * Address Locations:: Address locations
9402 @node Linespec Locations
9403 @subsection Linespec Locations
9404 @cindex linespec locations
9406 A @dfn{linespec} is a colon-separated list of source location parameters such
9407 as file name, function name, etc. Here are all the different ways of
9408 specifying a linespec:
9412 Specifies the line number @var{linenum} of the current source file.
9415 @itemx +@var{offset}
9416 Specifies the line @var{offset} lines before or after the @dfn{current
9417 line}. For the @code{list} command, the current line is the last one
9418 printed; for the breakpoint commands, this is the line at which
9419 execution stopped in the currently selected @dfn{stack frame}
9420 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9421 used as the second of the two linespecs in a @code{list} command,
9422 this specifies the line @var{offset} lines up or down from the first
9425 @item @var{filename}:@var{linenum}
9426 Specifies the line @var{linenum} in the source file @var{filename}.
9427 If @var{filename} is a relative file name, then it will match any
9428 source file name with the same trailing components. For example, if
9429 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9430 name of @file{/build/trunk/gcc/expr.c}, but not
9431 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9433 @item @var{function}
9434 Specifies the line that begins the body of the function @var{function}.
9435 For example, in C, this is the line with the open brace.
9437 By default, in C@t{++} and Ada, @var{function} is interpreted as
9438 specifying all functions named @var{function} in all scopes. For
9439 C@t{++}, this means in all namespaces and classes. For Ada, this
9440 means in all packages.
9442 For example, assuming a program with C@t{++} symbols named
9443 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9444 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9446 Commands that accept a linespec let you override this with the
9447 @code{-qualified} option. For example, @w{@kbd{break -qualified
9448 func}} sets a breakpoint on a free-function named @code{func} ignoring
9449 any C@t{++} class methods and namespace functions called @code{func}.
9451 @xref{Explicit Locations}.
9453 @item @var{function}:@var{label}
9454 Specifies the line where @var{label} appears in @var{function}.
9456 @item @var{filename}:@var{function}
9457 Specifies the line that begins the body of the function @var{function}
9458 in the file @var{filename}. You only need the file name with a
9459 function name to avoid ambiguity when there are identically named
9460 functions in different source files.
9463 Specifies the line at which the label named @var{label} appears
9464 in the function corresponding to the currently selected stack frame.
9465 If there is no current selected stack frame (for instance, if the inferior
9466 is not running), then @value{GDBN} will not search for a label.
9468 @cindex breakpoint at static probe point
9469 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9470 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9471 applications to embed static probes. @xref{Static Probe Points}, for more
9472 information on finding and using static probes. This form of linespec
9473 specifies the location of such a static probe.
9475 If @var{objfile} is given, only probes coming from that shared library
9476 or executable matching @var{objfile} as a regular expression are considered.
9477 If @var{provider} is given, then only probes from that provider are considered.
9478 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9479 each one of those probes.
9482 @node Explicit Locations
9483 @subsection Explicit Locations
9484 @cindex explicit locations
9486 @dfn{Explicit locations} allow the user to directly specify the source
9487 location's parameters using option-value pairs.
9489 Explicit locations are useful when several functions, labels, or
9490 file names have the same name (base name for files) in the program's
9491 sources. In these cases, explicit locations point to the source
9492 line you meant more accurately and unambiguously. Also, using
9493 explicit locations might be faster in large programs.
9495 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9496 defined in the file named @file{foo} or the label @code{bar} in a function
9497 named @code{foo}. @value{GDBN} must search either the file system or
9498 the symbol table to know.
9500 The list of valid explicit location options is summarized in the
9504 @item -source @var{filename}
9505 The value specifies the source file name. To differentiate between
9506 files with the same base name, prepend as many directories as is necessary
9507 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9508 @value{GDBN} will use the first file it finds with the given base
9509 name. This option requires the use of either @code{-function} or @code{-line}.
9511 @item -function @var{function}
9512 The value specifies the name of a function. Operations
9513 on function locations unmodified by other options (such as @code{-label}
9514 or @code{-line}) refer to the line that begins the body of the function.
9515 In C, for example, this is the line with the open brace.
9517 By default, in C@t{++} and Ada, @var{function} is interpreted as
9518 specifying all functions named @var{function} in all scopes. For
9519 C@t{++}, this means in all namespaces and classes. For Ada, this
9520 means in all packages.
9522 For example, assuming a program with C@t{++} symbols named
9523 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9524 -function func}} and @w{@kbd{break -function B::func}} set a
9525 breakpoint on both symbols.
9527 You can use the @kbd{-qualified} flag to override this (see below).
9531 This flag makes @value{GDBN} interpret a function name specified with
9532 @kbd{-function} as a complete fully-qualified name.
9534 For example, assuming a C@t{++} program with symbols named
9535 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9536 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9538 (Note: the @kbd{-qualified} option can precede a linespec as well
9539 (@pxref{Linespec Locations}), so the particular example above could be
9540 simplified as @w{@kbd{break -qualified B::func}}.)
9542 @item -label @var{label}
9543 The value specifies the name of a label. When the function
9544 name is not specified, the label is searched in the function of the currently
9545 selected stack frame.
9547 @item -line @var{number}
9548 The value specifies a line offset for the location. The offset may either
9549 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9550 the command. When specified without any other options, the line offset is
9551 relative to the current line.
9554 Explicit location options may be abbreviated by omitting any non-unique
9555 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9557 @node Address Locations
9558 @subsection Address Locations
9559 @cindex address locations
9561 @dfn{Address locations} indicate a specific program address. They have
9562 the generalized form *@var{address}.
9564 For line-oriented commands, such as @code{list} and @code{edit}, this
9565 specifies a source line that contains @var{address}. For @code{break} and
9566 other breakpoint-oriented commands, this can be used to set breakpoints in
9567 parts of your program which do not have debugging information or
9570 Here @var{address} may be any expression valid in the current working
9571 language (@pxref{Languages, working language}) that specifies a code
9572 address. In addition, as a convenience, @value{GDBN} extends the
9573 semantics of expressions used in locations to cover several situations
9574 that frequently occur during debugging. Here are the various forms
9578 @item @var{expression}
9579 Any expression valid in the current working language.
9581 @item @var{funcaddr}
9582 An address of a function or procedure derived from its name. In C,
9583 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9584 simply the function's name @var{function} (and actually a special case
9585 of a valid expression). In Pascal and Modula-2, this is
9586 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9587 (although the Pascal form also works).
9589 This form specifies the address of the function's first instruction,
9590 before the stack frame and arguments have been set up.
9592 @item '@var{filename}':@var{funcaddr}
9593 Like @var{funcaddr} above, but also specifies the name of the source
9594 file explicitly. This is useful if the name of the function does not
9595 specify the function unambiguously, e.g., if there are several
9596 functions with identical names in different source files.
9600 @section Editing Source Files
9601 @cindex editing source files
9604 @kindex e @r{(@code{edit})}
9605 To edit the lines in a source file, use the @code{edit} command.
9606 The editing program of your choice
9607 is invoked with the current line set to
9608 the active line in the program.
9609 Alternatively, there are several ways to specify what part of the file you
9610 want to print if you want to see other parts of the program:
9613 @item edit @var{locspec}
9614 Edit the source file of the code location that results from resolving
9615 @code{locspec}. Editing starts at the source file and source line
9616 @code{locspec} resolves to.
9617 @xref{Location Specifications}, for all the possible forms of the
9618 @var{locspec} argument.
9620 If @code{locspec} resolves to more than one source line in your
9621 program, then the command prints the list of resolved source lines and
9622 does not proceed with the editing.
9624 Here are the forms of the @code{edit} command most commonly used:
9627 @item edit @var{number}
9628 Edit the current source file with @var{number} as the active line number.
9630 @item edit @var{function}
9631 Edit the file containing @var{function} at the beginning of its definition.
9636 @subsection Choosing your Editor
9637 You can customize @value{GDBN} to use any editor you want
9639 The only restriction is that your editor (say @code{ex}), recognizes the
9640 following command-line syntax:
9642 ex +@var{number} file
9644 The optional numeric value +@var{number} specifies the number of the line in
9645 the file where to start editing.}.
9646 By default, it is @file{@value{EDITOR}}, but you can change this
9647 by setting the environment variable @env{EDITOR} before using
9648 @value{GDBN}. For example, to configure @value{GDBN} to use the
9649 @code{vi} editor, you could use these commands with the @code{sh} shell:
9655 or in the @code{csh} shell,
9657 setenv EDITOR /usr/bin/vi
9662 @section Searching Source Files
9663 @cindex searching source files
9665 There are two commands for searching through the current source file for a
9670 @kindex forward-search
9671 @kindex fo @r{(@code{forward-search})}
9672 @item forward-search @var{regexp}
9673 @itemx search @var{regexp}
9674 The command @samp{forward-search @var{regexp}} checks each line,
9675 starting with the one following the last line listed, for a match for
9676 @var{regexp}. It lists the line that is found. You can use the
9677 synonym @samp{search @var{regexp}} or abbreviate the command name as
9680 @kindex reverse-search
9681 @item reverse-search @var{regexp}
9682 The command @samp{reverse-search @var{regexp}} checks each line, starting
9683 with the one before the last line listed and going backward, for a match
9684 for @var{regexp}. It lists the line that is found. You can abbreviate
9685 this command as @code{rev}.
9689 @section Specifying Source Directories
9692 @cindex directories for source files
9693 Executable programs sometimes do not record the directories of the source
9694 files from which they were compiled, just the names. Even when they do,
9695 the directories could be moved between the compilation and your debugging
9696 session. @value{GDBN} has a list of directories to search for source files;
9697 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9698 it tries all the directories in the list, in the order they are present
9699 in the list, until it finds a file with the desired name.
9701 For example, suppose an executable references the file
9702 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9703 directory, and the @dfn{source path} is @file{/mnt/cross}.
9704 @value{GDBN} would look for the source file in the following
9709 @item @file{/usr/src/foo-1.0/lib/foo.c}
9710 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9711 @item @file{/mnt/cross/foo.c}
9715 If the source file is not present at any of the above locations then
9716 an error is printed. @value{GDBN} does not look up the parts of the
9717 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9718 Likewise, the subdirectories of the source path are not searched: if
9719 the source path is @file{/mnt/cross}, and the binary refers to
9720 @file{foo.c}, @value{GDBN} would not find it under
9721 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9723 Plain file names, relative file names with leading directories, file
9724 names containing dots, etc.@: are all treated as described above,
9725 except that non-absolute file names are not looked up literally. If
9726 the @dfn{source path} is @file{/mnt/cross}, the source file is
9727 recorded as @file{../lib/foo.c}, and no compilation directory is
9728 recorded, then @value{GDBN} will search in the following locations:
9732 @item @file{/mnt/cross/../lib/foo.c}
9733 @item @file{/mnt/cross/foo.c}
9739 @vindex $cdir@r{, convenience variable}
9740 @vindex $cwd@r{, convenience variable}
9741 @cindex compilation directory
9742 @cindex current directory
9743 @cindex working directory
9744 @cindex directory, current
9745 @cindex directory, compilation
9746 The @dfn{source path} will always include two special entries
9747 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9748 (if one is recorded) and the current working directory respectively.
9750 @samp{$cdir} causes @value{GDBN} to search within the compilation
9751 directory, if one is recorded in the debug information. If no
9752 compilation directory is recorded in the debug information then
9753 @samp{$cdir} is ignored.
9755 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9756 current working directory as it changes during your @value{GDBN}
9757 session, while the latter is immediately expanded to the current
9758 directory at the time you add an entry to the source path.
9760 If a compilation directory is recorded in the debug information, and
9761 @value{GDBN} has not found the source file after the first search
9762 using @dfn{source path}, then @value{GDBN} will combine the
9763 compilation directory and the filename, and then search for the source
9764 file again using the @dfn{source path}.
9766 For example, if the executable records the source file as
9767 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9768 recorded as @file{/project/build}, and the @dfn{source path} is
9769 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9770 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9771 search for the source file in the following locations:
9775 @item @file{/usr/src/foo-1.0/lib/foo.c}
9776 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9777 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9778 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9779 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9780 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9781 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9782 @item @file{/mnt/cross/foo.c}
9783 @item @file{/project/build/foo.c}
9784 @item @file{/home/user/foo.c}
9788 If the file name in the previous example had been recorded in the
9789 executable as a relative path rather than an absolute path, then the
9790 first look up would not have occurred, but all of the remaining steps
9793 When searching for source files on MS-DOS and MS-Windows, where
9794 absolute paths start with a drive letter (e.g.@:
9795 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9796 from the file name before appending it to a search directory from
9797 @dfn{source path}; for instance if the executable references the
9798 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9799 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9800 locations for the source file:
9804 @item @file{C:/project/foo.c}
9805 @item @file{D:/mnt/cross/project/foo.c}
9806 @item @file{D:/mnt/cross/foo.c}
9810 Note that the executable search path is @emph{not} used to locate the
9813 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9814 any information it has cached about where source files are found and where
9815 each line is in the file.
9819 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9820 and @samp{$cwd}, in that order.
9821 To add other directories, use the @code{directory} command.
9823 The search path is used to find both program source files and @value{GDBN}
9824 script files (read using the @samp{-command} option and @samp{source} command).
9826 In addition to the source path, @value{GDBN} provides a set of commands
9827 that manage a list of source path substitution rules. A @dfn{substitution
9828 rule} specifies how to rewrite source directories stored in the program's
9829 debug information in case the sources were moved to a different
9830 directory between compilation and debugging. A rule is made of
9831 two strings, the first specifying what needs to be rewritten in
9832 the path, and the second specifying how it should be rewritten.
9833 In @ref{set substitute-path}, we name these two parts @var{from} and
9834 @var{to} respectively. @value{GDBN} does a simple string replacement
9835 of @var{from} with @var{to} at the start of the directory part of the
9836 source file name, and uses that result instead of the original file
9837 name to look up the sources.
9839 Using the previous example, suppose the @file{foo-1.0} tree has been
9840 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9841 @value{GDBN} to replace @file{/usr/src} in all source path names with
9842 @file{/mnt/cross}. The first lookup will then be
9843 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9844 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9845 substitution rule, use the @code{set substitute-path} command
9846 (@pxref{set substitute-path}).
9848 To avoid unexpected substitution results, a rule is applied only if the
9849 @var{from} part of the directory name ends at a directory separator.
9850 For instance, a rule substituting @file{/usr/source} into
9851 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9852 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9853 is applied only at the beginning of the directory name, this rule will
9854 not be applied to @file{/root/usr/source/baz.c} either.
9856 In many cases, you can achieve the same result using the @code{directory}
9857 command. However, @code{set substitute-path} can be more efficient in
9858 the case where the sources are organized in a complex tree with multiple
9859 subdirectories. With the @code{directory} command, you need to add each
9860 subdirectory of your project. If you moved the entire tree while
9861 preserving its internal organization, then @code{set substitute-path}
9862 allows you to direct the debugger to all the sources with one single
9865 @code{set substitute-path} is also more than just a shortcut command.
9866 The source path is only used if the file at the original location no
9867 longer exists. On the other hand, @code{set substitute-path} modifies
9868 the debugger behavior to look at the rewritten location instead. So, if
9869 for any reason a source file that is not relevant to your executable is
9870 located at the original location, a substitution rule is the only
9871 method available to point @value{GDBN} at the new location.
9873 @cindex @samp{--with-relocated-sources}
9874 @cindex default source path substitution
9875 You can configure a default source path substitution rule by
9876 configuring @value{GDBN} with the
9877 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9878 should be the name of a directory under @value{GDBN}'s configured
9879 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9880 directory names in debug information under @var{dir} will be adjusted
9881 automatically if the installed @value{GDBN} is moved to a new
9882 location. This is useful if @value{GDBN}, libraries or executables
9883 with debug information and corresponding source code are being moved
9887 @item directory @var{dirname} @dots{}
9888 @item dir @var{dirname} @dots{}
9889 Add directory @var{dirname} to the front of the source path. Several
9890 directory names may be given to this command, separated by @samp{:}
9891 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9892 part of absolute file names) or
9893 whitespace. You may specify a directory that is already in the source
9894 path; this moves it forward, so @value{GDBN} searches it sooner.
9896 The special strings @samp{$cdir} (to refer to the compilation
9897 directory, if one is recorded), and @samp{$cwd} (to refer to the
9898 current working directory) can also be included in the list of
9899 directories @var{dirname}. Though these will already be in the source
9900 path they will be moved forward in the list so @value{GDBN} searches
9904 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9906 @c RET-repeat for @code{directory} is explicitly disabled, but since
9907 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9909 @item set directories @var{path-list}
9910 @kindex set directories
9911 Set the source path to @var{path-list}.
9912 @samp{$cdir:$cwd} are added if missing.
9914 @item show directories
9915 @kindex show directories
9916 Print the source path: show which directories it contains.
9918 @anchor{set substitute-path}
9919 @item set substitute-path @var{from} @var{to}
9920 @kindex set substitute-path
9921 Define a source path substitution rule, and add it at the end of the
9922 current list of existing substitution rules. If a rule with the same
9923 @var{from} was already defined, then the old rule is also deleted.
9925 For example, if the file @file{/foo/bar/baz.c} was moved to
9926 @file{/mnt/cross/baz.c}, then the command
9929 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9933 will tell @value{GDBN} to replace @samp{/foo/bar} with
9934 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9935 @file{baz.c} even though it was moved.
9937 In the case when more than one substitution rule have been defined,
9938 the rules are evaluated one by one in the order where they have been
9939 defined. The first one matching, if any, is selected to perform
9942 For instance, if we had entered the following commands:
9945 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9946 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9950 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9951 @file{/mnt/include/defs.h} by using the first rule. However, it would
9952 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9953 @file{/mnt/src/lib/foo.c}.
9956 @item unset substitute-path [path]
9957 @kindex unset substitute-path
9958 If a path is specified, search the current list of substitution rules
9959 for a rule that would rewrite that path. Delete that rule if found.
9960 A warning is emitted by the debugger if no rule could be found.
9962 If no path is specified, then all substitution rules are deleted.
9964 @item show substitute-path [path]
9965 @kindex show substitute-path
9966 If a path is specified, then print the source path substitution rule
9967 which would rewrite that path, if any.
9969 If no path is specified, then print all existing source path substitution
9974 If your source path is cluttered with directories that are no longer of
9975 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9976 versions of source. You can correct the situation as follows:
9980 Use @code{directory} with no argument to reset the source path to its default value.
9983 Use @code{directory} with suitable arguments to reinstall the
9984 directories you want in the source path. You can add all the
9985 directories in one command.
9989 @section Source and Machine Code
9990 @cindex source line and its code address
9992 You can use the command @code{info line} to map source lines to program
9993 addresses (and vice versa), and the command @code{disassemble} to display
9994 a range of addresses as machine instructions. You can use the command
9995 @code{set disassemble-next-line} to set whether to disassemble next
9996 source line when execution stops. When run under @sc{gnu} Emacs
9997 mode, the @code{info line} command causes the arrow to point to the
9998 line specified. Also, @code{info line} prints addresses in symbolic form as
10004 @itemx info line @var{locspec}
10005 Print the starting and ending addresses of the compiled code for the
10006 source lines of the code locations that result from resolving
10007 @var{locspec}. @xref{Location Specifications}, for the various forms
10009 With no @var{locspec}, information about the current source line is
10013 For example, we can use @code{info line} to discover the location of
10014 the object code for the first line of function
10015 @code{m4_changequote}:
10018 (@value{GDBP}) info line m4_changequote
10019 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
10020 ends at 0x6350 <m4_changequote+4>.
10024 @cindex code address and its source line
10025 We can also inquire, using @code{*@var{addr}} as the form for
10026 @var{locspec}, what source line covers a particular address
10029 (@value{GDBP}) info line *0x63ff
10030 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
10031 ends at 0x6404 <m4_changequote+184>.
10034 @cindex @code{$_} and @code{info line}
10035 @cindex @code{x} command, default address
10036 @kindex x@r{(examine), and} info line
10037 After @code{info line}, the default address for the @code{x} command
10038 is changed to the starting address of the line, so that @samp{x/i} is
10039 sufficient to begin examining the machine code (@pxref{Memory,
10040 ,Examining Memory}). Also, this address is saved as the value of the
10041 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
10044 @cindex info line, repeated calls
10045 After @code{info line}, using @code{info line} again without
10046 specifying a location will display information about the next source
10049 @anchor{disassemble}
10051 @kindex disassemble
10052 @cindex assembly instructions
10053 @cindex instructions, assembly
10054 @cindex machine instructions
10055 @cindex listing machine instructions
10057 @itemx disassemble /m
10058 @itemx disassemble /s
10059 @itemx disassemble /r
10060 @itemx disassemble /b
10061 This specialized command dumps a range of memory as machine
10062 instructions. It can also print mixed source+disassembly by specifying
10063 the @code{/m} or @code{/s} modifier and print the raw instructions in
10064 hex as well as in symbolic form by specifying the @code{/r} or @code{/b}
10067 Only one of @code{/m} and @code{/s} can be used, attempting to use
10068 both flag will give an error.
10070 Only one of @code{/r} and @code{/b} can be used, attempting to use
10071 both flag will give an error.
10073 The default memory range is the function surrounding the program
10074 counter of the selected frame. A single argument to this command is a
10075 program counter value; @value{GDBN} dumps the function surrounding
10076 this value. When two arguments are given, they should be separated by
10077 a comma, possibly surrounded by whitespace. The arguments specify a
10078 range of addresses to dump, in one of two forms:
10081 @item @var{start},@var{end}
10082 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
10083 @item @var{start},+@var{length}
10084 the addresses from @var{start} (inclusive) to
10085 @code{@var{start}+@var{length}} (exclusive).
10089 When 2 arguments are specified, the name of the function is also
10090 printed (since there could be several functions in the given range).
10092 The argument(s) can be any expression yielding a numeric value, such as
10093 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
10095 If the range of memory being disassembled contains current program counter,
10096 the instruction at that location is shown with a @code{=>} marker.
10099 The following example shows the disassembly of a range of addresses of
10100 HP PA-RISC 2.0 code:
10103 (@value{GDBP}) disas 0x32c4, 0x32e4
10104 Dump of assembler code from 0x32c4 to 0x32e4:
10105 0x32c4 <main+204>: addil 0,dp
10106 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
10107 0x32cc <main+212>: ldil 0x3000,r31
10108 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
10109 0x32d4 <main+220>: ldo 0(r31),rp
10110 0x32d8 <main+224>: addil -0x800,dp
10111 0x32dc <main+228>: ldo 0x588(r1),r26
10112 0x32e0 <main+232>: ldil 0x3000,r31
10113 End of assembler dump.
10116 The following two examples are for RISC-V, and demonstrates the
10117 difference between the @code{/r} and @code{/b} modifiers. First with
10118 @code{/b}, the bytes of the instruction are printed, in hex, in memory
10122 (@value{GDBP}) disassemble /b 0x00010150,0x0001015c
10123 Dump of assembler code from 0x10150 to 0x1015c:
10124 0x00010150 <call_me+4>: 22 dc sw s0,56(sp)
10125 0x00010152 <call_me+6>: 80 00 addi s0,sp,64
10126 0x00010154 <call_me+8>: 23 26 a4 fe sw a0,-20(s0)
10127 0x00010158 <call_me+12>: 23 24 b4 fe sw a1,-24(s0)
10128 End of assembler dump.
10131 In contrast, with @code{/r} the bytes of the instruction are displayed
10132 in the instruction order, for RISC-V this means that the bytes have been
10133 swapped to little-endian order:
10136 (@value{GDBP}) disassemble /r 0x00010150,0x0001015c
10137 Dump of assembler code from 0x10150 to 0x1015c:
10138 0x00010150 <call_me+4>: dc22 sw s0,56(sp)
10139 0x00010152 <call_me+6>: 0080 addi s0,sp,64
10140 0x00010154 <call_me+8>: fea42623 sw a0,-20(s0)
10141 0x00010158 <call_me+12>: feb42423 sw a1,-24(s0)
10142 End of assembler dump.
10145 Here is an example showing mixed source+assembly for Intel x86
10146 with @code{/m} or @code{/s}, when the program is stopped just after
10147 function prologue in a non-optimized function with no inline code.
10150 (@value{GDBP}) disas /m main
10151 Dump of assembler code for function main:
10153 0x08048330 <+0>: push %ebp
10154 0x08048331 <+1>: mov %esp,%ebp
10155 0x08048333 <+3>: sub $0x8,%esp
10156 0x08048336 <+6>: and $0xfffffff0,%esp
10157 0x08048339 <+9>: sub $0x10,%esp
10159 6 printf ("Hello.\n");
10160 => 0x0804833c <+12>: movl $0x8048440,(%esp)
10161 0x08048343 <+19>: call 0x8048284 <puts@@plt>
10165 0x08048348 <+24>: mov $0x0,%eax
10166 0x0804834d <+29>: leave
10167 0x0804834e <+30>: ret
10169 End of assembler dump.
10172 The @code{/m} option is deprecated as its output is not useful when
10173 there is either inlined code or re-ordered code.
10174 The @code{/s} option is the preferred choice.
10175 Here is an example for AMD x86-64 showing the difference between
10176 @code{/m} output and @code{/s} output.
10177 This example has one inline function defined in a header file,
10178 and the code is compiled with @samp{-O2} optimization.
10179 Note how the @code{/m} output is missing the disassembly of
10180 several instructions that are present in the @code{/s} output.
10210 (@value{GDBP}) disas /m main
10211 Dump of assembler code for function main:
10215 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10216 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10220 0x000000000040041d <+29>: xor %eax,%eax
10221 0x000000000040041f <+31>: retq
10222 0x0000000000400420 <+32>: add %eax,%eax
10223 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10225 End of assembler dump.
10226 (@value{GDBP}) disas /s main
10227 Dump of assembler code for function main:
10231 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10235 0x0000000000400406 <+6>: test %eax,%eax
10236 0x0000000000400408 <+8>: js 0x400420 <main+32>
10241 0x000000000040040a <+10>: lea 0xa(%rax),%edx
10242 0x000000000040040d <+13>: test %eax,%eax
10243 0x000000000040040f <+15>: mov $0x1,%eax
10244 0x0000000000400414 <+20>: cmovne %edx,%eax
10248 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10252 0x000000000040041d <+29>: xor %eax,%eax
10253 0x000000000040041f <+31>: retq
10257 0x0000000000400420 <+32>: add %eax,%eax
10258 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10259 End of assembler dump.
10262 Here is another example showing raw instructions in hex for AMD x86-64,
10265 (@value{GDBP}) disas /r 0x400281,+10
10266 Dump of assembler code from 0x400281 to 0x40028b:
10267 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10268 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10269 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10270 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10271 End of assembler dump.
10274 Note that the @samp{disassemble} command's address arguments are
10275 specified using expressions in your programming language
10276 (@pxref{Expressions, ,Expressions}), not location specs
10277 (@pxref{Location Specifications}). So, for example, if you want to
10278 disassemble function @code{bar} in file @file{foo.c}, you must type
10279 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10281 Some architectures have more than one commonly-used set of instruction
10282 mnemonics or other syntax.
10284 For programs that were dynamically linked and use shared libraries,
10285 instructions that call functions or branch to locations in the shared
10286 libraries might show a seemingly bogus location---it's actually a
10287 location of the relocation table. On some architectures, @value{GDBN}
10288 might be able to resolve these to actual function names.
10291 @kindex set disassembler-options
10292 @cindex disassembler options
10293 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10294 This command controls the passing of target specific information to
10295 the disassembler. For a list of valid options, please refer to the
10296 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10297 manual and/or the output of @kbd{objdump --help}
10298 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10299 The default value is the empty string.
10301 If it is necessary to specify more than one disassembler option, then
10302 multiple options can be placed together into a comma separated list.
10303 Currently this command is only supported on targets ARC, ARM, MIPS,
10306 @kindex show disassembler-options
10307 @item show disassembler-options
10308 Show the current setting of the disassembler options.
10312 @kindex set disassembly-flavor
10313 @cindex Intel disassembly flavor
10314 @cindex AT&T disassembly flavor
10315 @item set disassembly-flavor @var{instruction-set}
10316 Select the instruction set to use when disassembling the
10317 program via the @code{disassemble} or @code{x/i} commands.
10319 Currently this command is only defined for the Intel x86 family. You
10320 can set @var{instruction-set} to either @code{intel} or @code{att}.
10321 The default is @code{att}, the AT&T flavor used by default by Unix
10322 assemblers for x86-based targets.
10324 @kindex show disassembly-flavor
10325 @item show disassembly-flavor
10326 Show the current setting of the disassembly flavor.
10330 @kindex set disassemble-next-line
10331 @kindex show disassemble-next-line
10332 @item set disassemble-next-line
10333 @itemx show disassemble-next-line
10334 Control whether or not @value{GDBN} will disassemble the next source
10335 line or instruction when execution stops. If ON, @value{GDBN} will
10336 display disassembly of the next source line when execution of the
10337 program being debugged stops. This is @emph{in addition} to
10338 displaying the source line itself, which @value{GDBN} always does if
10339 possible. If the next source line cannot be displayed for some reason
10340 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10341 info in the debug info), @value{GDBN} will display disassembly of the
10342 next @emph{instruction} instead of showing the next source line. If
10343 AUTO, @value{GDBN} will display disassembly of next instruction only
10344 if the source line cannot be displayed. This setting causes
10345 @value{GDBN} to display some feedback when you step through a function
10346 with no line info or whose source file is unavailable. The default is
10347 OFF, which means never display the disassembly of the next line or
10351 @node Disable Reading Source
10352 @section Disable Reading Source Code
10353 @cindex source code, disable access
10355 In some cases it can be desirable to prevent @value{GDBN} from
10356 accessing source code files. One case where this might be desirable
10357 is if the source code files are located over a slow network
10360 The following command can be used to control whether @value{GDBN}
10361 should access source code files or not:
10364 @kindex set source open
10365 @kindex show source open
10366 @item set source open @r{[}on@r{|}off@r{]}
10367 @itemx show source open
10368 When this option is @code{on}, which is the default, @value{GDBN} will
10369 access source code files when needed, for example to print source
10370 lines when @value{GDBN} stops, or in response to the @code{list}
10373 When this option is @code{off}, @value{GDBN} will not access source
10378 @chapter Examining Data
10380 @cindex printing data
10381 @cindex examining data
10384 The usual way to examine data in your program is with the @code{print}
10385 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10386 evaluates and prints the value of an expression of the language your
10387 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10388 Different Languages}). It may also print the expression using a
10389 Python-based pretty-printer (@pxref{Pretty Printing}).
10392 @item print [[@var{options}] --] @var{expr}
10393 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10394 @var{expr} is an expression (in the source language). By default the
10395 value of @var{expr} is printed in a format appropriate to its data type;
10396 you can choose a different format by specifying @samp{/@var{f}}, where
10397 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10400 @anchor{print options}
10401 The @code{print} command supports a number of options that allow
10402 overriding relevant global print settings as set by @code{set print}
10406 @item -address [@code{on}|@code{off}]
10407 Set printing of addresses.
10408 Related setting: @ref{set print address}.
10410 @item -array [@code{on}|@code{off}]
10411 Pretty formatting of arrays.
10412 Related setting: @ref{set print array}.
10414 @item -array-indexes [@code{on}|@code{off}]
10415 Set printing of array indexes.
10416 Related setting: @ref{set print array-indexes}.
10418 @item -characters @var{number-of-characters}|@code{elements}|@code{unlimited}
10419 Set limit on string characters to print. The value @code{elements}
10420 causes the limit on array elements to print to be used. The value
10421 @code{unlimited} causes there to be no limit. Related setting:
10422 @ref{set print characters}.
10424 @item -elements @var{number-of-elements}|@code{unlimited}
10425 Set limit on array elements and optionally string characters to print.
10426 See @ref{set print characters}, and the @code{-characters} option above
10427 for when this option applies to strings. The value @code{unlimited}
10428 causes there to be no limit. @xref{set print elements}, for a related
10431 @item -max-depth @var{depth}|@code{unlimited}
10432 Set the threshold after which nested structures are replaced with
10433 ellipsis. Related setting: @ref{set print max-depth}.
10435 @item -nibbles [@code{on}|@code{off}]
10436 Set whether to print binary values in groups of four bits, known
10437 as ``nibbles''. @xref{set print nibbles}.
10439 @item -memory-tag-violations [@code{on}|@code{off}]
10440 Set printing of additional information about memory tag violations.
10441 @xref{set print memory-tag-violations}.
10443 @item -null-stop [@code{on}|@code{off}]
10444 Set printing of char arrays to stop at first null char. Related
10445 setting: @ref{set print null-stop}.
10447 @item -object [@code{on}|@code{off}]
10448 Set printing C@t{++} virtual function tables. Related setting:
10449 @ref{set print object}.
10451 @item -pretty [@code{on}|@code{off}]
10452 Set pretty formatting of structures. Related setting: @ref{set print
10455 @item -raw-values [@code{on}|@code{off}]
10456 Set whether to print values in raw form, bypassing any
10457 pretty-printers for that value. Related setting: @ref{set print
10460 @item -repeats @var{number-of-repeats}|@code{unlimited}
10461 Set threshold for repeated print elements. @code{unlimited} causes
10462 all elements to be individually printed. Related setting: @ref{set
10465 @item -static-members [@code{on}|@code{off}]
10466 Set printing C@t{++} static members. Related setting: @ref{set print
10469 @item -symbol [@code{on}|@code{off}]
10470 Set printing of symbol names when printing pointers. Related setting:
10471 @ref{set print symbol}.
10473 @item -union [@code{on}|@code{off}]
10474 Set printing of unions interior to structures. Related setting:
10475 @ref{set print union}.
10477 @item -vtbl [@code{on}|@code{off}]
10478 Set printing of C++ virtual function tables. Related setting:
10479 @ref{set print vtbl}.
10482 Because the @code{print} command accepts arbitrary expressions which
10483 may look like options (including abbreviations), if you specify any
10484 command option, then you must use a double dash (@code{--}) to mark
10485 the end of option processing.
10487 For example, this prints the value of the @code{-p} expression:
10490 (@value{GDBP}) print -p
10493 While this repeats the last value in the value history (see below)
10494 with the @code{-pretty} option in effect:
10497 (@value{GDBP}) print -p --
10500 Here is an example including both on option and an expression:
10504 (@value{GDBP}) print -pretty -- *myptr
10516 @item print [@var{options}]
10517 @itemx print [@var{options}] /@var{f}
10518 @cindex reprint the last value
10519 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10520 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10521 conveniently inspect the same value in an alternative format.
10524 If the architecture supports memory tagging, the @code{print} command will
10525 display pointer/memory tag mismatches if what is being printed is a pointer
10526 or reference type. @xref{Memory Tagging}.
10528 A more low-level way of examining data is with the @code{x} command.
10529 It examines data in memory at a specified address and prints it in a
10530 specified format. @xref{Memory, ,Examining Memory}.
10532 If you are interested in information about types, or about how the
10533 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10534 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10537 @cindex exploring hierarchical data structures
10539 Another way of examining values of expressions and type information is
10540 through the Python extension command @code{explore} (available only if
10541 the @value{GDBN} build is configured with @code{--with-python}). It
10542 offers an interactive way to start at the highest level (or, the most
10543 abstract level) of the data type of an expression (or, the data type
10544 itself) and explore all the way down to leaf scalar values/fields
10545 embedded in the higher level data types.
10548 @item explore @var{arg}
10549 @var{arg} is either an expression (in the source language), or a type
10550 visible in the current context of the program being debugged.
10553 The working of the @code{explore} command can be illustrated with an
10554 example. If a data type @code{struct ComplexStruct} is defined in your
10558 struct SimpleStruct
10564 struct ComplexStruct
10566 struct SimpleStruct *ss_p;
10572 followed by variable declarations as
10575 struct SimpleStruct ss = @{ 10, 1.11 @};
10576 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10580 then, the value of the variable @code{cs} can be explored using the
10581 @code{explore} command as follows.
10584 (@value{GDBP}) explore cs
10585 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10586 the following fields:
10588 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10589 arr = <Enter 1 to explore this field of type `int [10]'>
10591 Enter the field number of choice:
10595 Since the fields of @code{cs} are not scalar values, you are being
10596 prompted to chose the field you want to explore. Let's say you choose
10597 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10598 pointer, you will be asked if it is pointing to a single value. From
10599 the declaration of @code{cs} above, it is indeed pointing to a single
10600 value, hence you enter @code{y}. If you enter @code{n}, then you will
10601 be asked if it were pointing to an array of values, in which case this
10602 field will be explored as if it were an array.
10605 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10606 Continue exploring it as a pointer to a single value [y/n]: y
10607 The value of `*(cs.ss_p)' is a struct/class of type `struct
10608 SimpleStruct' with the following fields:
10610 i = 10 .. (Value of type `int')
10611 d = 1.1100000000000001 .. (Value of type `double')
10613 Press enter to return to parent value:
10617 If the field @code{arr} of @code{cs} was chosen for exploration by
10618 entering @code{1} earlier, then since it is as array, you will be
10619 prompted to enter the index of the element in the array that you want
10623 `cs.arr' is an array of `int'.
10624 Enter the index of the element you want to explore in `cs.arr': 5
10626 `(cs.arr)[5]' is a scalar value of type `int'.
10630 Press enter to return to parent value:
10633 In general, at any stage of exploration, you can go deeper towards the
10634 leaf values by responding to the prompts appropriately, or hit the
10635 return key to return to the enclosing data structure (the @i{higher}
10636 level data structure).
10638 Similar to exploring values, you can use the @code{explore} command to
10639 explore types. Instead of specifying a value (which is typically a
10640 variable name or an expression valid in the current context of the
10641 program being debugged), you specify a type name. If you consider the
10642 same example as above, your can explore the type
10643 @code{struct ComplexStruct} by passing the argument
10644 @code{struct ComplexStruct} to the @code{explore} command.
10647 (@value{GDBP}) explore struct ComplexStruct
10651 By responding to the prompts appropriately in the subsequent interactive
10652 session, you can explore the type @code{struct ComplexStruct} in a
10653 manner similar to how the value @code{cs} was explored in the above
10656 The @code{explore} command also has two sub-commands,
10657 @code{explore value} and @code{explore type}. The former sub-command is
10658 a way to explicitly specify that value exploration of the argument is
10659 being invoked, while the latter is a way to explicitly specify that type
10660 exploration of the argument is being invoked.
10663 @item explore value @var{expr}
10664 @cindex explore value
10665 This sub-command of @code{explore} explores the value of the
10666 expression @var{expr} (if @var{expr} is an expression valid in the
10667 current context of the program being debugged). The behavior of this
10668 command is identical to that of the behavior of the @code{explore}
10669 command being passed the argument @var{expr}.
10671 @item explore type @var{arg}
10672 @cindex explore type
10673 This sub-command of @code{explore} explores the type of @var{arg} (if
10674 @var{arg} is a type visible in the current context of program being
10675 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10676 is an expression valid in the current context of the program being
10677 debugged). If @var{arg} is a type, then the behavior of this command is
10678 identical to that of the @code{explore} command being passed the
10679 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10680 this command will be identical to that of the @code{explore} command
10681 being passed the type of @var{arg} as the argument.
10685 * Expressions:: Expressions
10686 * Ambiguous Expressions:: Ambiguous Expressions
10687 * Variables:: Program variables
10688 * Arrays:: Artificial arrays
10689 * Output Formats:: Output formats
10690 * Memory:: Examining memory
10691 * Memory Tagging:: Memory Tagging
10692 * Auto Display:: Automatic display
10693 * Print Settings:: Print settings
10694 * Pretty Printing:: Python pretty printing
10695 * Value History:: Value history
10696 * Convenience Vars:: Convenience variables
10697 * Convenience Funs:: Convenience functions
10698 * Registers:: Registers
10699 * Floating Point Hardware:: Floating point hardware
10700 * Vector Unit:: Vector Unit
10701 * OS Information:: Auxiliary data provided by operating system
10702 * Memory Region Attributes:: Memory region attributes
10703 * Dump/Restore Files:: Copy between memory and a file
10704 * Core File Generation:: Cause a program dump its core
10705 * Character Sets:: Debugging programs that use a different
10706 character set than GDB does
10707 * Caching Target Data:: Data caching for targets
10708 * Searching Memory:: Searching memory for a sequence of bytes
10709 * Value Sizes:: Managing memory allocated for values
10713 @section Expressions
10715 @cindex expressions
10716 @code{print} and many other @value{GDBN} commands accept an expression and
10717 compute its value. Any kind of constant, variable or operator defined
10718 by the programming language you are using is valid in an expression in
10719 @value{GDBN}. This includes conditional expressions, function calls,
10720 casts, and string constants. It also includes preprocessor macros, if
10721 you compiled your program to include this information; see
10724 @cindex arrays in expressions
10725 @value{GDBN} supports array constants in expressions input by
10726 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10727 you can use the command @code{print @{1, 2, 3@}} to create an array
10728 of three integers. If you pass an array to a function or assign it
10729 to a program variable, @value{GDBN} copies the array to memory that
10730 is @code{malloc}ed in the target program.
10732 Because C is so widespread, most of the expressions shown in examples in
10733 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10734 Languages}, for information on how to use expressions in other
10737 In this section, we discuss operators that you can use in @value{GDBN}
10738 expressions regardless of your programming language.
10740 @cindex casts, in expressions
10741 Casts are supported in all languages, not just in C, because it is so
10742 useful to cast a number into a pointer in order to examine a structure
10743 at that address in memory.
10744 @c FIXME: casts supported---Mod2 true?
10746 @value{GDBN} supports these operators, in addition to those common
10747 to programming languages:
10751 @samp{@@} is a binary operator for treating parts of memory as arrays.
10752 @xref{Arrays, ,Artificial Arrays}, for more information.
10755 @samp{::} allows you to specify a variable in terms of the file or
10756 function where it is defined. @xref{Variables, ,Program Variables}.
10758 @cindex @{@var{type}@}
10759 @cindex type casting memory
10760 @cindex memory, viewing as typed object
10761 @cindex casts, to view memory
10762 @item @{@var{type}@} @var{addr}
10763 Refers to an object of type @var{type} stored at address @var{addr} in
10764 memory. The address @var{addr} may be any expression whose value is
10765 an integer or pointer (but parentheses are required around binary
10766 operators, just as in a cast). This construct is allowed regardless
10767 of what kind of data is normally supposed to reside at @var{addr}.
10770 @node Ambiguous Expressions
10771 @section Ambiguous Expressions
10772 @cindex ambiguous expressions
10774 Expressions can sometimes contain some ambiguous elements. For instance,
10775 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10776 a single function name to be defined several times, for application in
10777 different contexts. This is called @dfn{overloading}. Another example
10778 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10779 templates and is typically instantiated several times, resulting in
10780 the same function name being defined in different contexts.
10782 In some cases and depending on the language, it is possible to adjust
10783 the expression to remove the ambiguity. For instance in C@t{++}, you
10784 can specify the signature of the function you want to break on, as in
10785 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10786 qualified name of your function often makes the expression unambiguous
10789 When an ambiguity that needs to be resolved is detected, the debugger
10790 has the capability to display a menu of numbered choices for each
10791 possibility, and then waits for the selection with the prompt @samp{>}.
10792 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10793 aborts the current command. If the command in which the expression was
10794 used allows more than one choice to be selected, the next option in the
10795 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10798 For example, the following session excerpt shows an attempt to set a
10799 breakpoint at the overloaded symbol @code{String::after}.
10800 We choose three particular definitions of that function name:
10802 @c FIXME! This is likely to change to show arg type lists, at least
10805 (@value{GDBP}) b String::after
10808 [2] file:String.cc; line number:867
10809 [3] file:String.cc; line number:860
10810 [4] file:String.cc; line number:875
10811 [5] file:String.cc; line number:853
10812 [6] file:String.cc; line number:846
10813 [7] file:String.cc; line number:735
10815 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10816 Breakpoint 2 at 0xb344: file String.cc, line 875.
10817 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10818 Multiple breakpoints were set.
10819 Use the "delete" command to delete unwanted
10826 @kindex set multiple-symbols
10827 @item set multiple-symbols @var{mode}
10828 @cindex multiple-symbols menu
10830 This option allows you to adjust the debugger behavior when an expression
10833 By default, @var{mode} is set to @code{all}. If the command with which
10834 the expression is used allows more than one choice, then @value{GDBN}
10835 automatically selects all possible choices. For instance, inserting
10836 a breakpoint on a function using an ambiguous name results in a breakpoint
10837 inserted on each possible match. However, if a unique choice must be made,
10838 then @value{GDBN} uses the menu to help you disambiguate the expression.
10839 For instance, printing the address of an overloaded function will result
10840 in the use of the menu.
10842 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10843 when an ambiguity is detected.
10845 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10846 an error due to the ambiguity and the command is aborted.
10848 @kindex show multiple-symbols
10849 @item show multiple-symbols
10850 Show the current value of the @code{multiple-symbols} setting.
10854 @section Program Variables
10856 The most common kind of expression to use is the name of a variable
10859 Variables in expressions are understood in the selected stack frame
10860 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10864 global (or file-static)
10871 visible according to the scope rules of the
10872 programming language from the point of execution in that frame
10875 @noindent This means that in the function
10890 you can examine and use the variable @code{a} whenever your program is
10891 executing within the function @code{foo}, but you can only use or
10892 examine the variable @code{b} while your program is executing inside
10893 the block where @code{b} is declared.
10895 @cindex variable name conflict
10896 There is an exception: you can refer to a variable or function whose
10897 scope is a single source file even if the current execution point is not
10898 in this file. But it is possible to have more than one such variable or
10899 function with the same name (in different source files). If that
10900 happens, referring to that name has unpredictable effects. If you wish,
10901 you can specify a static variable in a particular function or file by
10902 using the colon-colon (@code{::}) notation:
10904 @cindex colon-colon, context for variables/functions
10906 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10907 @cindex @code{::}, context for variables/functions
10910 @var{file}::@var{variable}
10911 @var{function}::@var{variable}
10915 Here @var{file} or @var{function} is the name of the context for the
10916 static @var{variable}. In the case of file names, you can use quotes to
10917 make sure @value{GDBN} parses the file name as a single word---for example,
10918 to print a global value of @code{x} defined in @file{f2.c}:
10921 (@value{GDBP}) p 'f2.c'::x
10924 The @code{::} notation is normally used for referring to
10925 static variables, since you typically disambiguate uses of local variables
10926 in functions by selecting the appropriate frame and using the
10927 simple name of the variable. However, you may also use this notation
10928 to refer to local variables in frames enclosing the selected frame:
10937 process (a); /* Stop here */
10948 For example, if there is a breakpoint at the commented line,
10949 here is what you might see
10950 when the program stops after executing the call @code{bar(0)}:
10955 (@value{GDBP}) p bar::a
10957 (@value{GDBP}) up 2
10958 #2 0x080483d0 in foo (a=5) at foobar.c:12
10961 (@value{GDBP}) p bar::a
10965 @cindex C@t{++} scope resolution
10966 These uses of @samp{::} are very rarely in conflict with the very
10967 similar use of the same notation in C@t{++}. When they are in
10968 conflict, the C@t{++} meaning takes precedence; however, this can be
10969 overridden by quoting the file or function name with single quotes.
10971 For example, suppose the program is stopped in a method of a class
10972 that has a field named @code{includefile}, and there is also an
10973 include file named @file{includefile} that defines a variable,
10974 @code{some_global}.
10977 (@value{GDBP}) p includefile
10979 (@value{GDBP}) p includefile::some_global
10980 A syntax error in expression, near `'.
10981 (@value{GDBP}) p 'includefile'::some_global
10985 @cindex wrong values
10986 @cindex variable values, wrong
10987 @cindex function entry/exit, wrong values of variables
10988 @cindex optimized code, wrong values of variables
10990 @emph{Warning:} Occasionally, a local variable may appear to have the
10991 wrong value at certain points in a function---just after entry to a new
10992 scope, and just before exit.
10994 You may see this problem when you are stepping by machine instructions.
10995 This is because, on most machines, it takes more than one instruction to
10996 set up a stack frame (including local variable definitions); if you are
10997 stepping by machine instructions, variables may appear to have the wrong
10998 values until the stack frame is completely built. On exit, it usually
10999 also takes more than one machine instruction to destroy a stack frame;
11000 after you begin stepping through that group of instructions, local
11001 variable definitions may be gone.
11003 This may also happen when the compiler does significant optimizations.
11004 To be sure of always seeing accurate values, turn off all optimization
11007 @cindex ``No symbol "foo" in current context''
11008 Another possible effect of compiler optimizations is to optimize
11009 unused variables out of existence, or assign variables to registers (as
11010 opposed to memory addresses). Depending on the support for such cases
11011 offered by the debug info format used by the compiler, @value{GDBN}
11012 might not be able to display values for such local variables. If that
11013 happens, @value{GDBN} will print a message like this:
11016 No symbol "foo" in current context.
11019 To solve such problems, either recompile without optimizations, or use a
11020 different debug info format, if the compiler supports several such
11021 formats. @xref{Compilation}, for more information on choosing compiler
11022 options. @xref{C, ,C and C@t{++}}, for more information about debug
11023 info formats that are best suited to C@t{++} programs.
11025 If you ask to print an object whose contents are unknown to
11026 @value{GDBN}, e.g., because its data type is not completely specified
11027 by the debug information, @value{GDBN} will say @samp{<incomplete
11028 type>}. @xref{Symbols, incomplete type}, for more about this.
11030 @cindex no debug info variables
11031 If you try to examine or use the value of a (global) variable for
11032 which @value{GDBN} has no type information, e.g., because the program
11033 includes no debug information, @value{GDBN} displays an error message.
11034 @xref{Symbols, unknown type}, for more about unknown types. If you
11035 cast the variable to its declared type, @value{GDBN} gets the
11036 variable's value using the cast-to type as the variable's type. For
11037 example, in a C program:
11040 (@value{GDBP}) p var
11041 'var' has unknown type; cast it to its declared type
11042 (@value{GDBP}) p (float) var
11046 If you append @kbd{@@entry} string to a function parameter name you get its
11047 value at the time the function got called. If the value is not available an
11048 error message is printed. Entry values are available only with some compilers.
11049 Entry values are normally also printed at the function parameter list according
11050 to @ref{set print entry-values}.
11053 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
11055 (@value{GDBP}) next
11057 (@value{GDBP}) print i
11059 (@value{GDBP}) print i@@entry
11063 Strings are identified as arrays of @code{char} values without specified
11064 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
11065 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
11066 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
11067 defines literal string type @code{"char"} as @code{char} without a sign.
11072 signed char var1[] = "A";
11075 You get during debugging
11077 (@value{GDBP}) print var0
11079 (@value{GDBP}) print var1
11080 $2 = @{65 'A', 0 '\0'@}
11084 @section Artificial Arrays
11086 @cindex artificial array
11088 @kindex @@@r{, referencing memory as an array}
11089 It is often useful to print out several successive objects of the
11090 same type in memory; a section of an array, or an array of
11091 dynamically determined size for which only a pointer exists in the
11094 You can do this by referring to a contiguous span of memory as an
11095 @dfn{artificial array}, using the binary operator @samp{@@}. The left
11096 operand of @samp{@@} should be the first element of the desired array
11097 and be an individual object. The right operand should be the desired length
11098 of the array. The result is an array value whose elements are all of
11099 the type of the left argument. The first element is actually the left
11100 argument; the second element comes from bytes of memory immediately
11101 following those that hold the first element, and so on. Here is an
11102 example. If a program says
11105 int *array = (int *) malloc (len * sizeof (int));
11109 you can print the contents of @code{array} with
11115 The left operand of @samp{@@} must reside in memory. Array values made
11116 with @samp{@@} in this way behave just like other arrays in terms of
11117 subscripting, and are coerced to pointers when used in expressions.
11118 Artificial arrays most often appear in expressions via the value history
11119 (@pxref{Value History, ,Value History}), after printing one out.
11121 Another way to create an artificial array is to use a cast.
11122 This re-interprets a value as if it were an array.
11123 The value need not be in memory:
11125 (@value{GDBP}) p/x (short[2])0x12345678
11126 $1 = @{0x1234, 0x5678@}
11129 As a convenience, if you leave the array length out (as in
11130 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
11131 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
11133 (@value{GDBP}) p/x (short[])0x12345678
11134 $2 = @{0x1234, 0x5678@}
11137 Sometimes the artificial array mechanism is not quite enough; in
11138 moderately complex data structures, the elements of interest may not
11139 actually be adjacent---for example, if you are interested in the values
11140 of pointers in an array. One useful work-around in this situation is
11141 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
11142 Variables}) as a counter in an expression that prints the first
11143 interesting value, and then repeat that expression via @key{RET}. For
11144 instance, suppose you have an array @code{dtab} of pointers to
11145 structures, and you are interested in the values of a field @code{fv}
11146 in each structure. Here is an example of what you might type:
11156 @node Output Formats
11157 @section Output Formats
11159 @cindex formatted output
11160 @cindex output formats
11161 By default, @value{GDBN} prints a value according to its data type. Sometimes
11162 this is not what you want. For example, you might want to print a number
11163 in hex, or a pointer in decimal. Or you might want to view data in memory
11164 at a certain address as a character string or as an instruction. To do
11165 these things, specify an @dfn{output format} when you print a value.
11167 The simplest use of output formats is to say how to print a value
11168 already computed. This is done by starting the arguments of the
11169 @code{print} command with a slash and a format letter. The format
11170 letters supported are:
11174 Print the binary representation of the value in hexadecimal.
11177 Print the binary representation of the value in decimal.
11180 Print the binary representation of the value as an decimal, as if it
11184 Print the binary representation of the value in octal.
11187 Print the binary representation of the value in binary. The letter
11188 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
11189 because these format letters are also used with the @code{x} command,
11190 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
11194 @cindex unknown address, locating
11195 @cindex locate address
11196 Print as an address, both absolute in hexadecimal and as an offset from
11197 the nearest preceding symbol. You can use this format used to discover
11198 where (in what function) an unknown address is located:
11201 (@value{GDBP}) p/a 0x54320
11202 $3 = 0x54320 <_initialize_vx+396>
11206 The command @code{info symbol 0x54320} yields similar results.
11207 @xref{Symbols, info symbol}.
11210 Cast the value to an integer (unlike other formats, this does not just
11211 reinterpret the underlying bits) and print it as a character constant.
11212 This prints both the numerical value and its character representation.
11213 The character representation is replaced with the octal escape
11214 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
11216 Without this format, @value{GDBN} displays @code{char},
11217 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
11218 constants. Single-byte members of vectors are displayed as integer
11222 Regard the bits of the value as a floating point number and print
11223 using typical floating point syntax.
11226 @cindex printing strings
11227 @cindex printing byte arrays
11228 Regard as a string, if possible. With this format, pointers to single-byte
11229 data are displayed as null-terminated strings and arrays of single-byte data
11230 are displayed as fixed-length strings. Other values are displayed in their
11233 Without this format, @value{GDBN} displays pointers to and arrays of
11234 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
11235 strings. Single-byte members of a vector are displayed as an integer
11239 Like @samp{x} formatting, the value is treated as an integer and
11240 printed as hexadecimal, but leading zeros are printed to pad the value
11241 to the size of the integer type.
11244 @cindex raw printing
11245 Print using the @samp{raw} formatting. By default, @value{GDBN} will
11246 use a Python-based pretty-printer, if one is available (@pxref{Pretty
11247 Printing}). This typically results in a higher-level display of the
11248 value's contents. The @samp{r} format bypasses any Python
11249 pretty-printer which might exist.
11252 For example, to print the program counter in hex (@pxref{Registers}), type
11259 Note that no space is required before the slash; this is because command
11260 names in @value{GDBN} cannot contain a slash.
11262 To reprint the last value in the value history with a different format,
11263 you can use the @code{print} command with just a format and no
11264 expression. For example, @samp{p/x} reprints the last value in hex.
11267 @section Examining Memory
11269 You can use the command @code{x} (for ``examine'') to examine memory in
11270 any of several formats, independently of your program's data types.
11272 @cindex examining memory
11274 @kindex x @r{(examine memory)}
11275 @item x/@var{nfu} @var{addr}
11276 @itemx x @var{addr}
11278 Use the @code{x} command to examine memory.
11281 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11282 much memory to display and how to format it; @var{addr} is an
11283 expression giving the address where you want to start displaying memory.
11284 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11285 Several commands set convenient defaults for @var{addr}.
11288 @item @var{n}, the repeat count
11289 The repeat count is a decimal integer; the default is 1. It specifies
11290 how much memory (counting by units @var{u}) to display. If a negative
11291 number is specified, memory is examined backward from @var{addr}.
11292 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11295 @item @var{f}, the display format
11296 The display format is one of the formats used by @code{print}
11297 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11298 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11299 @samp{m} (for displaying memory tags).
11300 The default is @samp{x} (hexadecimal) initially. The default changes
11301 each time you use either @code{x} or @code{print}.
11303 @item @var{u}, the unit size
11304 The unit size is any of
11310 Halfwords (two bytes).
11312 Words (four bytes). This is the initial default.
11314 Giant words (eight bytes).
11317 Each time you specify a unit size with @code{x}, that size becomes the
11318 default unit the next time you use @code{x}. For the @samp{i} format,
11319 the unit size is ignored and is normally not written. For the @samp{s} format,
11320 the unit size defaults to @samp{b}, unless it is explicitly given.
11321 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11322 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11323 Note that the results depend on the programming language of the
11324 current compilation unit. If the language is C, the @samp{s}
11325 modifier will use the UTF-16 encoding while @samp{w} will use
11326 UTF-32. The encoding is set by the programming language and cannot
11329 @item @var{addr}, starting display address
11330 @var{addr} is the address where you want @value{GDBN} to begin displaying
11331 memory. The expression need not have a pointer value (though it may);
11332 it is always interpreted as an integer address of a byte of memory.
11333 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11334 @var{addr} is usually just after the last address examined---but several
11335 other commands also set the default address: @code{info breakpoints} (to
11336 the address of the last breakpoint listed), @code{info line} (to the
11337 starting address of a line), and @code{print} (if you use it to display
11338 a value from memory).
11341 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11342 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11343 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11344 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11345 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11347 You can also specify a negative repeat count to examine memory backward
11348 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11349 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11351 Since the letters indicating unit sizes are all distinct from the
11352 letters specifying output formats, you do not have to remember whether
11353 unit size or format comes first; either order works. The output
11354 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11355 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11357 Even though the unit size @var{u} is ignored for the formats @samp{s}
11358 and @samp{i}, you might still want to use a count @var{n}; for example,
11359 @samp{3i} specifies that you want to see three machine instructions,
11360 including any operands. For convenience, especially when used with
11361 the @code{display} command, the @samp{i} format also prints branch delay
11362 slot instructions, if any, beyond the count specified, which immediately
11363 follow the last instruction that is within the count. The command
11364 @code{disassemble} gives an alternative way of inspecting machine
11365 instructions; see @ref{Machine Code,,Source and Machine Code}.
11367 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11368 the command displays null-terminated strings or instructions before the given
11369 address as many as the absolute value of the given number. For the @samp{i}
11370 format, we use line number information in the debug info to accurately locate
11371 instruction boundaries while disassembling backward. If line info is not
11372 available, the command stops examining memory with an error message.
11374 All the defaults for the arguments to @code{x} are designed to make it
11375 easy to continue scanning memory with minimal specifications each time
11376 you use @code{x}. For example, after you have inspected three machine
11377 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11378 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11379 the repeat count @var{n} is used again; the other arguments default as
11380 for successive uses of @code{x}.
11382 When examining machine instructions, the instruction at current program
11383 counter is shown with a @code{=>} marker. For example:
11386 (@value{GDBP}) x/5i $pc-6
11387 0x804837f <main+11>: mov %esp,%ebp
11388 0x8048381 <main+13>: push %ecx
11389 0x8048382 <main+14>: sub $0x4,%esp
11390 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11391 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11394 If the architecture supports memory tagging, the tags can be displayed by
11395 using @samp{m}. @xref{Memory Tagging}.
11397 The information will be displayed once per granule size
11398 (the amount of bytes a particular memory tag covers). For example, AArch64
11399 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11401 Due to the way @value{GDBN} prints information with the @code{x} command (not
11402 aligned to a particular boundary), the tag information will refer to the
11403 initial address displayed on a particular line. If a memory tag boundary
11404 is crossed in the middle of a line displayed by the @code{x} command, it
11405 will be displayed on the next line.
11407 The @samp{m} format doesn't affect any other specified formats that were
11408 passed to the @code{x} command.
11410 @cindex @code{$_}, @code{$__}, and value history
11411 The addresses and contents printed by the @code{x} command are not saved
11412 in the value history because there is often too much of them and they
11413 would get in the way. Instead, @value{GDBN} makes these values available for
11414 subsequent use in expressions as values of the convenience variables
11415 @code{$_} and @code{$__}. After an @code{x} command, the last address
11416 examined is available for use in expressions in the convenience variable
11417 @code{$_}. The contents of that address, as examined, are available in
11418 the convenience variable @code{$__}.
11420 If the @code{x} command has a repeat count, the address and contents saved
11421 are from the last memory unit printed; this is not the same as the last
11422 address printed if several units were printed on the last line of output.
11424 @anchor{addressable memory unit}
11425 @cindex addressable memory unit
11426 Most targets have an addressable memory unit size of 8 bits. This means
11427 that to each memory address are associated 8 bits of data. Some
11428 targets, however, have other addressable memory unit sizes.
11429 Within @value{GDBN} and this document, the term
11430 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11431 when explicitly referring to a chunk of data of that size. The word
11432 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11433 the addressable memory unit size of the target. For most systems,
11434 addressable memory unit is a synonym of byte.
11436 @cindex remote memory comparison
11437 @cindex target memory comparison
11438 @cindex verify remote memory image
11439 @cindex verify target memory image
11440 When you are debugging a program running on a remote target machine
11441 (@pxref{Remote Debugging}), you may wish to verify the program's image
11442 in the remote machine's memory against the executable file you
11443 downloaded to the target. Or, on any target, you may want to check
11444 whether the program has corrupted its own read-only sections. The
11445 @code{compare-sections} command is provided for such situations.
11448 @kindex compare-sections
11449 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11450 Compare the data of a loadable section @var{section-name} in the
11451 executable file of the program being debugged with the same section in
11452 the target machine's memory, and report any mismatches. With no
11453 arguments, compares all loadable sections. With an argument of
11454 @code{-r}, compares all loadable read-only sections.
11456 Note: for remote targets, this command can be accelerated if the
11457 target supports computing the CRC checksum of a block of memory
11458 (@pxref{qCRC packet}).
11461 @node Memory Tagging
11462 @section Memory Tagging
11464 Memory tagging is a memory protection technology that uses a pair of tags to
11465 validate memory accesses through pointers. The tags are integer values
11466 usually comprised of a few bits, depending on the architecture.
11468 There are two types of tags that are used in this setup: logical and
11469 allocation. A logical tag is stored in the pointers themselves, usually at the
11470 higher bits of the pointers. An allocation tag is the tag associated
11471 with particular ranges of memory in the physical address space, against which
11472 the logical tags from pointers are compared.
11474 The pointer tag (logical tag) must match the memory tag (allocation tag)
11475 for the memory access to be valid. If the logical tag does not match the
11476 allocation tag, that will raise a memory violation.
11478 Allocation tags cover multiple contiguous bytes of physical memory. This
11479 range of bytes is called a memory tag granule and is architecture-specific.
11480 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11481 tag spans 16 bytes of memory.
11483 If the underlying architecture supports memory tagging, like AArch64 MTE
11484 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11485 against memory allocation tags.
11487 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11488 display tag information when appropriate, and a command prefix of
11489 @code{memory-tag} gives access to the various memory tagging commands.
11491 The @code{memory-tag} commands are the following:
11494 @kindex memory-tag print-logical-tag
11495 @item memory-tag print-logical-tag @var{pointer_expression}
11496 Print the logical tag stored in @var{pointer_expression}.
11497 @kindex memory-tag with-logical-tag
11498 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11499 Print the pointer given by @var{pointer_expression}, augmented with a logical
11500 tag of @var{tag_bytes}.
11501 @kindex memory-tag print-allocation-tag
11502 @item memory-tag print-allocation-tag @var{address_expression}
11503 Print the allocation tag associated with the memory address given by
11504 @var{address_expression}.
11505 @kindex memory-tag setatag
11506 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11507 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11508 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11509 @kindex memory-tag check
11510 @item memory-tag check @var{pointer_expression}
11511 Check if the logical tag in the pointer given by @var{pointer_expression}
11512 matches the allocation tag for the memory referenced by the pointer.
11514 This essentially emulates the hardware validation that is done when tagged
11515 memory is accessed through a pointer, but does not cause a memory fault as
11516 it would during hardware validation.
11518 It can be used to inspect potential memory tagging violations in the running
11519 process, before any faults get triggered.
11523 @section Automatic Display
11524 @cindex automatic display
11525 @cindex display of expressions
11527 If you find that you want to print the value of an expression frequently
11528 (to see how it changes), you might want to add it to the @dfn{automatic
11529 display list} so that @value{GDBN} prints its value each time your program stops.
11530 Each expression added to the list is given a number to identify it;
11531 to remove an expression from the list, you specify that number.
11532 The automatic display looks like this:
11536 3: bar[5] = (struct hack *) 0x3804
11540 This display shows item numbers, expressions and their current values. As with
11541 displays you request manually using @code{x} or @code{print}, you can
11542 specify the output format you prefer; in fact, @code{display} decides
11543 whether to use @code{print} or @code{x} depending your format
11544 specification---it uses @code{x} if you specify either the @samp{i}
11545 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11549 @item display @var{expr}
11550 Add the expression @var{expr} to the list of expressions to display
11551 each time your program stops. @xref{Expressions, ,Expressions}.
11553 @code{display} does not repeat if you press @key{RET} again after using it.
11555 @item display/@var{fmt} @var{expr}
11556 For @var{fmt} specifying only a display format and not a size or
11557 count, add the expression @var{expr} to the auto-display list but
11558 arrange to display it each time in the specified format @var{fmt}.
11559 @xref{Output Formats,,Output Formats}.
11561 @item display/@var{fmt} @var{addr}
11562 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11563 number of units, add the expression @var{addr} as a memory address to
11564 be examined each time your program stops. Examining means in effect
11565 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11568 For example, @samp{display/i $pc} can be helpful, to see the machine
11569 instruction about to be executed each time execution stops (@samp{$pc}
11570 is a common name for the program counter; @pxref{Registers, ,Registers}).
11573 @kindex delete display
11575 @item undisplay @var{dnums}@dots{}
11576 @itemx delete display @var{dnums}@dots{}
11577 Remove items from the list of expressions to display. Specify the
11578 numbers of the displays that you want affected with the command
11579 argument @var{dnums}. It can be a single display number, one of the
11580 numbers shown in the first field of the @samp{info display} display;
11581 or it could be a range of display numbers, as in @code{2-4}.
11583 @code{undisplay} does not repeat if you press @key{RET} after using it.
11584 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11586 @kindex disable display
11587 @item disable display @var{dnums}@dots{}
11588 Disable the display of item numbers @var{dnums}. A disabled display
11589 item is not printed automatically, but is not forgotten. It may be
11590 enabled again later. Specify the numbers of the displays that you
11591 want affected with the command argument @var{dnums}. It can be a
11592 single display number, one of the numbers shown in the first field of
11593 the @samp{info display} display; or it could be a range of display
11594 numbers, as in @code{2-4}.
11596 @kindex enable display
11597 @item enable display @var{dnums}@dots{}
11598 Enable display of item numbers @var{dnums}. It becomes effective once
11599 again in auto display of its expression, until you specify otherwise.
11600 Specify the numbers of the displays that you want affected with the
11601 command argument @var{dnums}. It can be a single display number, one
11602 of the numbers shown in the first field of the @samp{info display}
11603 display; or it could be a range of display numbers, as in @code{2-4}.
11606 Display the current values of the expressions on the list, just as is
11607 done when your program stops.
11609 @kindex info display
11611 Print the list of expressions previously set up to display
11612 automatically, each one with its item number, but without showing the
11613 values. This includes disabled expressions, which are marked as such.
11614 It also includes expressions which would not be displayed right now
11615 because they refer to automatic variables not currently available.
11618 @cindex display disabled out of scope
11619 If a display expression refers to local variables, then it does not make
11620 sense outside the lexical context for which it was set up. Such an
11621 expression is disabled when execution enters a context where one of its
11622 variables is not defined. For example, if you give the command
11623 @code{display last_char} while inside a function with an argument
11624 @code{last_char}, @value{GDBN} displays this argument while your program
11625 continues to stop inside that function. When it stops elsewhere---where
11626 there is no variable @code{last_char}---the display is disabled
11627 automatically. The next time your program stops where @code{last_char}
11628 is meaningful, you can enable the display expression once again.
11630 @node Print Settings
11631 @section Print Settings
11633 @cindex format options
11634 @cindex print settings
11635 @value{GDBN} provides the following ways to control how arrays, structures,
11636 and symbols are printed.
11639 These settings are useful for debugging programs in any language:
11643 @anchor{set print address}
11644 @item set print address
11645 @itemx set print address on
11646 @cindex print/don't print memory addresses
11647 @value{GDBN} prints memory addresses showing the location of stack
11648 traces, structure values, pointer values, breakpoints, and so forth,
11649 even when it also displays the contents of those addresses. The default
11650 is @code{on}. For example, this is what a stack frame display looks like with
11651 @code{set print address on}:
11656 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11658 530 if (lquote != def_lquote)
11662 @item set print address off
11663 Do not print addresses when displaying their contents. For example,
11664 this is the same stack frame displayed with @code{set print address off}:
11668 (@value{GDBP}) set print addr off
11670 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11671 530 if (lquote != def_lquote)
11675 You can use @samp{set print address off} to eliminate all machine
11676 dependent displays from the @value{GDBN} interface. For example, with
11677 @code{print address off}, you should get the same text for backtraces on
11678 all machines---whether or not they involve pointer arguments.
11681 @item show print address
11682 Show whether or not addresses are to be printed.
11685 When @value{GDBN} prints a symbolic address, it normally prints the
11686 closest earlier symbol plus an offset. If that symbol does not uniquely
11687 identify the address (for example, it is a name whose scope is a single
11688 source file), you may need to clarify. One way to do this is with
11689 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11690 you can set @value{GDBN} to print the source file and line number when
11691 it prints a symbolic address:
11694 @item set print symbol-filename on
11695 @cindex source file and line of a symbol
11696 @cindex symbol, source file and line
11697 Tell @value{GDBN} to print the source file name and line number of a
11698 symbol in the symbolic form of an address.
11700 @item set print symbol-filename off
11701 Do not print source file name and line number of a symbol. This is the
11704 @item show print symbol-filename
11705 Show whether or not @value{GDBN} will print the source file name and
11706 line number of a symbol in the symbolic form of an address.
11709 Another situation where it is helpful to show symbol filenames and line
11710 numbers is when disassembling code; @value{GDBN} shows you the line
11711 number and source file that corresponds to each instruction.
11713 Also, you may wish to see the symbolic form only if the address being
11714 printed is reasonably close to the closest earlier symbol:
11717 @item set print max-symbolic-offset @var{max-offset}
11718 @itemx set print max-symbolic-offset unlimited
11719 @cindex maximum value for offset of closest symbol
11720 Tell @value{GDBN} to only display the symbolic form of an address if the
11721 offset between the closest earlier symbol and the address is less than
11722 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11723 to always print the symbolic form of an address if any symbol precedes
11724 it. Zero is equivalent to @code{unlimited}.
11726 @item show print max-symbolic-offset
11727 Ask how large the maximum offset is that @value{GDBN} prints in a
11731 @cindex wild pointer, interpreting
11732 @cindex pointer, finding referent
11733 If you have a pointer and you are not sure where it points, try
11734 @samp{set print symbol-filename on}. Then you can determine the name
11735 and source file location of the variable where it points, using
11736 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11737 For example, here @value{GDBN} shows that a variable @code{ptt} points
11738 at another variable @code{t}, defined in @file{hi2.c}:
11741 (@value{GDBP}) set print symbol-filename on
11742 (@value{GDBP}) p/a ptt
11743 $4 = 0xe008 <t in hi2.c>
11747 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11748 does not show the symbol name and filename of the referent, even with
11749 the appropriate @code{set print} options turned on.
11752 You can also enable @samp{/a}-like formatting all the time using
11753 @samp{set print symbol on}:
11755 @anchor{set print symbol}
11757 @item set print symbol on
11758 Tell @value{GDBN} to print the symbol corresponding to an address, if
11761 @item set print symbol off
11762 Tell @value{GDBN} not to print the symbol corresponding to an
11763 address. In this mode, @value{GDBN} will still print the symbol
11764 corresponding to pointers to functions. This is the default.
11766 @item show print symbol
11767 Show whether @value{GDBN} will display the symbol corresponding to an
11771 Other settings control how different kinds of objects are printed:
11774 @anchor{set print array}
11775 @item set print array
11776 @itemx set print array on
11777 @cindex pretty print arrays
11778 Pretty print arrays. This format is more convenient to read,
11779 but uses more space. The default is off.
11781 @item set print array off
11782 Return to compressed format for arrays.
11784 @item show print array
11785 Show whether compressed or pretty format is selected for displaying
11788 @cindex print array indexes
11789 @anchor{set print array-indexes}
11790 @item set print array-indexes
11791 @itemx set print array-indexes on
11792 Print the index of each element when displaying arrays. May be more
11793 convenient to locate a given element in the array or quickly find the
11794 index of a given element in that printed array. The default is off.
11796 @item set print array-indexes off
11797 Stop printing element indexes when displaying arrays.
11799 @item show print array-indexes
11800 Show whether the index of each element is printed when displaying
11803 @anchor{set print nibbles}
11804 @item set print nibbles
11805 @itemx set print nibbles on
11806 @cindex print binary values in groups of four bits
11807 Print binary values in groups of four bits, known as @dfn{nibbles},
11808 when using the print command of @value{GDBN} with the option @samp{/t}.
11809 For example, this is what it looks like with @code{set print nibbles on}:
11813 (@value{GDBP}) print val_flags
11815 (@value{GDBP}) print/t val_flags
11816 $2 = 0100 1100 1110
11820 @item set print nibbles off
11821 Don't printing binary values in groups. This is the default.
11823 @item show print nibbles
11824 Show whether to print binary values in groups of four bits.
11826 @anchor{set print characters}
11827 @item set print characters @var{number-of-characters}
11828 @itemx set print characters elements
11829 @itemx set print characters unlimited
11830 @cindex number of string characters to print
11831 @cindex limit on number of printed string characters
11832 Set a limit on how many characters of a string @value{GDBN} will print.
11833 If @value{GDBN} is printing a large string, it stops printing after it
11834 has printed the number of characters set by the @code{set print
11835 characters} command. This equally applies to multi-byte and wide
11836 character strings, that is for strings whose character type is
11837 @code{wchar_t}, @code{char16_t}, or @code{char32_t} it is the number of
11838 actual characters rather than underlying bytes the encoding uses that
11839 this setting controls.
11840 Setting @var{number-of-characters} to @code{elements} means that the
11841 limit on the number of characters to print follows one for array
11842 elements; see @ref{set print elements}.
11843 Setting @var{number-of-characters} to @code{unlimited} means that the
11844 number of characters to print is unlimited.
11845 When @value{GDBN} starts, this limit is set to @code{elements}.
11847 @item show print characters
11848 Display the number of characters of a large string that @value{GDBN}
11851 @anchor{set print elements}
11852 @item set print elements @var{number-of-elements}
11853 @itemx set print elements unlimited
11854 @cindex number of array elements to print
11855 @cindex limit on number of printed array elements
11856 Set a limit on how many elements of an array @value{GDBN} will print.
11857 If @value{GDBN} is printing a large array, it stops printing after it has
11858 printed the number of elements set by the @code{set print elements} command.
11859 By default this limit also applies to the display of strings; see
11860 @ref{set print characters}.
11861 When @value{GDBN} starts, this limit is set to 200.
11862 Setting @var{number-of-elements} to @code{unlimited} or zero means
11863 that the number of elements to print is unlimited.
11865 When printing very large arrays, whose size is greater than
11866 @code{max-value-size} (@pxref{set max-value-size,,max-value-size}),
11867 if the @code{print elements} is set such that the size of the elements
11868 being printed is less than or equal to @code{max-value-size}, then
11869 @value{GDBN} will print the array (up to the @code{print elements} limit),
11870 and only @code{max-value-size} worth of data will be added into the value
11871 history (@pxref{Value History, ,Value History}).
11873 @item show print elements
11874 Display the number of elements of a large array that @value{GDBN} will print.
11876 @anchor{set print frame-arguments}
11877 @item set print frame-arguments @var{value}
11878 @kindex set print frame-arguments
11879 @cindex printing frame argument values
11880 @cindex print all frame argument values
11881 @cindex print frame argument values for scalars only
11882 @cindex do not print frame arguments
11883 This command allows to control how the values of arguments are printed
11884 when the debugger prints a frame (@pxref{Frames}). The possible
11889 The values of all arguments are printed.
11892 Print the value of an argument only if it is a scalar. The value of more
11893 complex arguments such as arrays, structures, unions, etc, is replaced
11894 by @code{@dots{}}. This is the default. Here is an example where
11895 only scalar arguments are shown:
11898 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11903 None of the argument values are printed. Instead, the value of each argument
11904 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11907 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11912 Only the presence of arguments is indicated by @code{@dots{}}.
11913 The @code{@dots{}} are not printed for function without any arguments.
11914 None of the argument names and values are printed.
11915 In this case, the example above now becomes:
11918 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11923 By default, only scalar arguments are printed. This command can be used
11924 to configure the debugger to print the value of all arguments, regardless
11925 of their type. However, it is often advantageous to not print the value
11926 of more complex parameters. For instance, it reduces the amount of
11927 information printed in each frame, making the backtrace more readable.
11928 Also, it improves performance when displaying Ada frames, because
11929 the computation of large arguments can sometimes be CPU-intensive,
11930 especially in large applications. Setting @code{print frame-arguments}
11931 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11932 this computation, thus speeding up the display of each Ada frame.
11934 @item show print frame-arguments
11935 Show how the value of arguments should be displayed when printing a frame.
11937 @anchor{set print raw-frame-arguments}
11938 @item set print raw-frame-arguments on
11939 Print frame arguments in raw, non pretty-printed, form.
11941 @item set print raw-frame-arguments off
11942 Print frame arguments in pretty-printed form, if there is a pretty-printer
11943 for the value (@pxref{Pretty Printing}),
11944 otherwise print the value in raw form.
11945 This is the default.
11947 @item show print raw-frame-arguments
11948 Show whether to print frame arguments in raw form.
11950 @anchor{set print entry-values}
11951 @item set print entry-values @var{value}
11952 @kindex set print entry-values
11953 Set printing of frame argument values at function entry. In some cases
11954 @value{GDBN} can determine the value of function argument which was passed by
11955 the function caller, even if the value was modified inside the called function
11956 and therefore is different. With optimized code, the current value could be
11957 unavailable, but the entry value may still be known.
11959 The default value is @code{default} (see below for its description). Older
11960 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11961 this feature will behave in the @code{default} setting the same way as with the
11964 This functionality is currently supported only by DWARF 2 debugging format and
11965 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11966 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11969 The @var{value} parameter can be one of the following:
11973 Print only actual parameter values, never print values from function entry
11977 #0 different (val=6)
11978 #0 lost (val=<optimized out>)
11980 #0 invalid (val=<optimized out>)
11984 Print only parameter values from function entry point. The actual parameter
11985 values are never printed.
11987 #0 equal (val@@entry=5)
11988 #0 different (val@@entry=5)
11989 #0 lost (val@@entry=5)
11990 #0 born (val@@entry=<optimized out>)
11991 #0 invalid (val@@entry=<optimized out>)
11995 Print only parameter values from function entry point. If value from function
11996 entry point is not known while the actual value is known, print the actual
11997 value for such parameter.
11999 #0 equal (val@@entry=5)
12000 #0 different (val@@entry=5)
12001 #0 lost (val@@entry=5)
12003 #0 invalid (val@@entry=<optimized out>)
12007 Print actual parameter values. If actual parameter value is not known while
12008 value from function entry point is known, print the entry point value for such
12012 #0 different (val=6)
12013 #0 lost (val@@entry=5)
12015 #0 invalid (val=<optimized out>)
12019 Always print both the actual parameter value and its value from function entry
12020 point, even if values of one or both are not available due to compiler
12023 #0 equal (val=5, val@@entry=5)
12024 #0 different (val=6, val@@entry=5)
12025 #0 lost (val=<optimized out>, val@@entry=5)
12026 #0 born (val=10, val@@entry=<optimized out>)
12027 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
12031 Print the actual parameter value if it is known and also its value from
12032 function entry point if it is known. If neither is known, print for the actual
12033 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
12034 values are known and identical, print the shortened
12035 @code{param=param@@entry=VALUE} notation.
12037 #0 equal (val=val@@entry=5)
12038 #0 different (val=6, val@@entry=5)
12039 #0 lost (val@@entry=5)
12041 #0 invalid (val=<optimized out>)
12045 Always print the actual parameter value. Print also its value from function
12046 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
12047 if both values are known and identical, print the shortened
12048 @code{param=param@@entry=VALUE} notation.
12050 #0 equal (val=val@@entry=5)
12051 #0 different (val=6, val@@entry=5)
12052 #0 lost (val=<optimized out>, val@@entry=5)
12054 #0 invalid (val=<optimized out>)
12058 For analysis messages on possible failures of frame argument values at function
12059 entry resolution see @ref{set debug entry-values}.
12061 @item show print entry-values
12062 Show the method being used for printing of frame argument values at function
12065 @anchor{set print frame-info}
12066 @item set print frame-info @var{value}
12067 @kindex set print frame-info
12068 @cindex printing frame information
12069 @cindex frame information, printing
12070 This command allows to control the information printed when
12071 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
12072 for a general explanation about frames and frame information.
12073 Note that some other settings (such as @code{set print frame-arguments}
12074 and @code{set print address}) are also influencing if and how some frame
12075 information is displayed. In particular, the frame program counter is never
12076 printed if @code{set print address} is off.
12078 The possible values for @code{set print frame-info} are:
12080 @item short-location
12081 Print the frame level, the program counter (if not at the
12082 beginning of the location source line), the function, the function
12085 Same as @code{short-location} but also print the source file and source line
12087 @item location-and-address
12088 Same as @code{location} but print the program counter even if located at the
12089 beginning of the location source line.
12091 Print the program counter (if not at the beginning of the location
12092 source line), the line number and the source line.
12093 @item source-and-location
12094 Print what @code{location} and @code{source-line} are printing.
12096 The information printed for a frame is decided automatically
12097 by the @value{GDBN} command that prints a frame.
12098 For example, @code{frame} prints the information printed by
12099 @code{source-and-location} while @code{stepi} will switch between
12100 @code{source-line} and @code{source-and-location} depending on the program
12102 The default value is @code{auto}.
12105 @anchor{set print repeats}
12106 @item set print repeats @var{number-of-repeats}
12107 @itemx set print repeats unlimited
12108 @cindex repeated array elements
12109 Set the threshold for suppressing display of repeated array
12110 elements. When the number of consecutive identical elements of an
12111 array exceeds the threshold, @value{GDBN} prints the string
12112 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
12113 identical repetitions, instead of displaying the identical elements
12114 themselves. Setting the threshold to @code{unlimited} or zero will
12115 cause all elements to be individually printed. The default threshold
12118 @item show print repeats
12119 Display the current threshold for printing repeated identical
12122 @anchor{set print max-depth}
12123 @item set print max-depth @var{depth}
12124 @item set print max-depth unlimited
12125 @cindex printing nested structures
12126 Set the threshold after which nested structures are replaced with
12127 ellipsis, this can make visualising deeply nested structures easier.
12129 For example, given this C code
12132 typedef struct s1 @{ int a; @} s1;
12133 typedef struct s2 @{ s1 b; @} s2;
12134 typedef struct s3 @{ s2 c; @} s3;
12135 typedef struct s4 @{ s3 d; @} s4;
12137 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
12140 The following table shows how different values of @var{depth} will
12141 effect how @code{var} is printed by @value{GDBN}:
12143 @multitable @columnfractions .3 .7
12144 @headitem @var{depth} setting @tab Result of @samp{p var}
12146 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12148 @tab @code{$1 = @{...@}}
12150 @tab @code{$1 = @{d = @{...@}@}}
12152 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
12154 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
12156 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12159 To see the contents of structures that have been hidden the user can
12160 either increase the print max-depth, or they can print the elements of
12161 the structure that are visible, for example
12164 (@value{GDBP}) set print max-depth 2
12165 (@value{GDBP}) p var
12166 $1 = @{d = @{c = @{...@}@}@}
12167 (@value{GDBP}) p var.d
12168 $2 = @{c = @{b = @{...@}@}@}
12169 (@value{GDBP}) p var.d.c
12170 $3 = @{b = @{a = 3@}@}
12173 The pattern used to replace nested structures varies based on
12174 language, for most languages @code{@{...@}} is used, but Fortran uses
12177 @item show print max-depth
12178 Display the current threshold after which nested structures are
12179 replaces with ellipsis.
12181 @anchor{set print memory-tag-violations}
12182 @cindex printing memory tag violation information
12183 @item set print memory-tag-violations
12184 @itemx set print memory-tag-violations on
12185 Cause @value{GDBN} to display additional information about memory tag violations
12186 when printing pointers and addresses.
12188 @item set print memory-tag-violations off
12189 Stop printing memory tag violation information.
12191 @item show print memory-tag-violations
12192 Show whether memory tag violation information is displayed when printing
12193 pointers and addresses.
12195 @anchor{set print null-stop}
12196 @item set print null-stop
12197 @cindex @sc{null} elements in arrays
12198 Cause @value{GDBN} to stop printing the characters of an array when the first
12199 @sc{null} is encountered. This is useful when large arrays actually
12200 contain only short strings.
12201 The default is off.
12203 @item show print null-stop
12204 Show whether @value{GDBN} stops printing an array on the first
12205 @sc{null} character.
12207 @anchor{set print pretty}
12208 @item set print pretty on
12209 @cindex print structures in indented form
12210 @cindex indentation in structure display
12211 Cause @value{GDBN} to print structures in an indented format with one member
12212 per line, like this:
12227 @item set print pretty off
12228 Cause @value{GDBN} to print structures in a compact format, like this:
12232 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
12233 meat = 0x54 "Pork"@}
12238 This is the default format.
12240 @item show print pretty
12241 Show which format @value{GDBN} is using to print structures.
12243 @anchor{set print raw-values}
12244 @item set print raw-values on
12245 Print values in raw form, without applying the pretty
12246 printers for the value.
12248 @item set print raw-values off
12249 Print values in pretty-printed form, if there is a pretty-printer
12250 for the value (@pxref{Pretty Printing}),
12251 otherwise print the value in raw form.
12253 The default setting is ``off''.
12255 @item show print raw-values
12256 Show whether to print values in raw form.
12258 @item set print sevenbit-strings on
12259 @cindex eight-bit characters in strings
12260 @cindex octal escapes in strings
12261 Print using only seven-bit characters; if this option is set,
12262 @value{GDBN} displays any eight-bit characters (in strings or
12263 character values) using the notation @code{\}@var{nnn}. This setting is
12264 best if you are working in English (@sc{ascii}) and you use the
12265 high-order bit of characters as a marker or ``meta'' bit.
12267 @item set print sevenbit-strings off
12268 Print full eight-bit characters. This allows the use of more
12269 international character sets, and is the default.
12271 @item show print sevenbit-strings
12272 Show whether or not @value{GDBN} is printing only seven-bit characters.
12274 @anchor{set print union}
12275 @item set print union on
12276 @cindex unions in structures, printing
12277 Tell @value{GDBN} to print unions which are contained in structures
12278 and other unions. This is the default setting.
12280 @item set print union off
12281 Tell @value{GDBN} not to print unions which are contained in
12282 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
12285 @item show print union
12286 Ask @value{GDBN} whether or not it will print unions which are contained in
12287 structures and other unions.
12289 For example, given the declarations
12292 typedef enum @{Tree, Bug@} Species;
12293 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12294 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12305 struct thing foo = @{Tree, @{Acorn@}@};
12309 with @code{set print union on} in effect @samp{p foo} would print
12312 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12316 and with @code{set print union off} in effect it would print
12319 $1 = @{it = Tree, form = @{...@}@}
12323 @code{set print union} affects programs written in C-like languages
12329 These settings are of interest when debugging C@t{++} programs:
12332 @cindex demangling C@t{++} names
12333 @item set print demangle
12334 @itemx set print demangle on
12335 Print C@t{++} names in their source form rather than in the encoded
12336 (``mangled'') form passed to the assembler and linker for type-safe
12337 linkage. The default is on.
12339 @item show print demangle
12340 Show whether C@t{++} names are printed in mangled or demangled form.
12342 @item set print asm-demangle
12343 @itemx set print asm-demangle on
12344 Print C@t{++} names in their source form rather than their mangled form, even
12345 in assembler code printouts such as instruction disassemblies.
12346 The default is off.
12348 @item show print asm-demangle
12349 Show whether C@t{++} names in assembly listings are printed in mangled
12352 @cindex C@t{++} symbol decoding style
12353 @cindex symbol decoding style, C@t{++}
12354 @kindex set demangle-style
12355 @item set demangle-style @var{style}
12356 Choose among several encoding schemes used by different compilers to represent
12357 C@t{++} names. If you omit @var{style}, you will see a list of possible
12358 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12359 decoding style by inspecting your program.
12361 @item show demangle-style
12362 Display the encoding style currently in use for decoding C@t{++} symbols.
12364 @anchor{set print object}
12365 @item set print object
12366 @itemx set print object on
12367 @cindex derived type of an object, printing
12368 @cindex display derived types
12369 When displaying a pointer to an object, identify the @emph{actual}
12370 (derived) type of the object rather than the @emph{declared} type, using
12371 the virtual function table. Note that the virtual function table is
12372 required---this feature can only work for objects that have run-time
12373 type identification; a single virtual method in the object's declared
12374 type is sufficient. Note that this setting is also taken into account when
12375 working with variable objects via MI (@pxref{GDB/MI}).
12377 @item set print object off
12378 Display only the declared type of objects, without reference to the
12379 virtual function table. This is the default setting.
12381 @item show print object
12382 Show whether actual, or declared, object types are displayed.
12384 @anchor{set print static-members}
12385 @item set print static-members
12386 @itemx set print static-members on
12387 @cindex static members of C@t{++} objects
12388 Print static members when displaying a C@t{++} object. The default is on.
12390 @item set print static-members off
12391 Do not print static members when displaying a C@t{++} object.
12393 @item show print static-members
12394 Show whether C@t{++} static members are printed or not.
12396 @item set print pascal_static-members
12397 @itemx set print pascal_static-members on
12398 @cindex static members of Pascal objects
12399 @cindex Pascal objects, static members display
12400 Print static members when displaying a Pascal object. The default is on.
12402 @item set print pascal_static-members off
12403 Do not print static members when displaying a Pascal object.
12405 @item show print pascal_static-members
12406 Show whether Pascal static members are printed or not.
12408 @c These don't work with HP ANSI C++ yet.
12409 @anchor{set print vtbl}
12410 @item set print vtbl
12411 @itemx set print vtbl on
12412 @cindex pretty print C@t{++} virtual function tables
12413 @cindex virtual functions (C@t{++}) display
12414 @cindex VTBL display
12415 Pretty print C@t{++} virtual function tables. The default is off.
12416 (The @code{vtbl} commands do not work on programs compiled with the HP
12417 ANSI C@t{++} compiler (@code{aCC}).)
12419 @item set print vtbl off
12420 Do not pretty print C@t{++} virtual function tables.
12422 @item show print vtbl
12423 Show whether C@t{++} virtual function tables are pretty printed, or not.
12426 @node Pretty Printing
12427 @section Pretty Printing
12429 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12430 Python code. It greatly simplifies the display of complex objects. This
12431 mechanism works for both MI and the CLI.
12434 * Pretty-Printer Introduction:: Introduction to pretty-printers
12435 * Pretty-Printer Example:: An example pretty-printer
12436 * Pretty-Printer Commands:: Pretty-printer commands
12439 @node Pretty-Printer Introduction
12440 @subsection Pretty-Printer Introduction
12442 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12443 registered for the value. If there is then @value{GDBN} invokes the
12444 pretty-printer to print the value. Otherwise the value is printed normally.
12446 Pretty-printers are normally named. This makes them easy to manage.
12447 The @samp{info pretty-printer} command will list all the installed
12448 pretty-printers with their names.
12449 If a pretty-printer can handle multiple data types, then its
12450 @dfn{subprinters} are the printers for the individual data types.
12451 Each such subprinter has its own name.
12452 The format of the name is @var{printer-name};@var{subprinter-name}.
12454 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12455 Typically they are automatically loaded and registered when the corresponding
12456 debug information is loaded, thus making them available without having to
12457 do anything special.
12459 There are three places where a pretty-printer can be registered.
12463 Pretty-printers registered globally are available when debugging
12467 Pretty-printers registered with a program space are available only
12468 when debugging that program.
12469 @xref{Progspaces In Python}, for more details on program spaces in Python.
12472 Pretty-printers registered with an objfile are loaded and unloaded
12473 with the corresponding objfile (e.g., shared library).
12474 @xref{Objfiles In Python}, for more details on objfiles in Python.
12477 @xref{Selecting Pretty-Printers}, for further information on how
12478 pretty-printers are selected,
12480 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12483 @node Pretty-Printer Example
12484 @subsection Pretty-Printer Example
12486 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12489 (@value{GDBP}) print s
12491 static npos = 4294967295,
12493 <std::allocator<char>> = @{
12494 <__gnu_cxx::new_allocator<char>> = @{
12495 <No data fields>@}, <No data fields>
12497 members of std::basic_string<char, std::char_traits<char>,
12498 std::allocator<char> >::_Alloc_hider:
12499 _M_p = 0x804a014 "abcd"
12504 With a pretty-printer for @code{std::string} only the contents are printed:
12507 (@value{GDBP}) print s
12511 @node Pretty-Printer Commands
12512 @subsection Pretty-Printer Commands
12513 @cindex pretty-printer commands
12516 @kindex info pretty-printer
12517 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12518 Print the list of installed pretty-printers.
12519 This includes disabled pretty-printers, which are marked as such.
12521 @var{object-regexp} is a regular expression matching the objects
12522 whose pretty-printers to list.
12523 Objects can be @code{global}, the program space's file
12524 (@pxref{Progspaces In Python}),
12525 and the object files within that program space (@pxref{Objfiles In Python}).
12526 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12527 looks up a printer from these three objects.
12529 @var{name-regexp} is a regular expression matching the name of the printers
12532 @kindex disable pretty-printer
12533 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12534 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12535 A disabled pretty-printer is not forgotten, it may be enabled again later.
12537 @kindex enable pretty-printer
12538 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12539 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12544 Suppose we have three pretty-printers installed: one from library1.so
12545 named @code{foo} that prints objects of type @code{foo}, and
12546 another from library2.so named @code{bar} that prints two types of objects,
12547 @code{bar1} and @code{bar2}.
12551 (@value{GDBP}) info pretty-printer
12560 (@value{GDBP}) info pretty-printer library2
12567 (@value{GDBP}) disable pretty-printer library1
12569 2 of 3 printers enabled
12570 (@value{GDBP}) info pretty-printer
12579 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12581 1 of 3 printers enabled
12582 (@value{GDBP}) info pretty-printer library2
12589 (@value{GDBP}) disable pretty-printer library2 bar
12591 0 of 3 printers enabled
12592 (@value{GDBP}) info pretty-printer
12602 Note that for @code{bar} the entire printer can be disabled,
12603 as can each individual subprinter.
12605 Printing values and frame arguments is done by default using
12606 the enabled pretty printers.
12608 The print option @code{-raw-values} and @value{GDBN} setting
12609 @code{set print raw-values} (@pxref{set print raw-values}) can be
12610 used to print values without applying the enabled pretty printers.
12612 Similarly, the backtrace option @code{-raw-frame-arguments} and
12613 @value{GDBN} setting @code{set print raw-frame-arguments}
12614 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12615 enabled pretty printers when printing frame argument values.
12617 @node Value History
12618 @section Value History
12620 @cindex value history
12621 @cindex history of values printed by @value{GDBN}
12622 Values printed by the @code{print} command are saved in the @value{GDBN}
12623 @dfn{value history}. This allows you to refer to them in other expressions.
12624 Values are kept until the symbol table is re-read or discarded
12625 (for example with the @code{file} or @code{symbol-file} commands).
12626 When the symbol table changes, the value history is discarded,
12627 since the values may contain pointers back to the types defined in the
12632 @cindex history number
12633 The values printed are given @dfn{history numbers} by which you can
12634 refer to them. These are successive integers starting with one.
12635 @code{print} shows you the history number assigned to a value by
12636 printing @samp{$@var{num} = } before the value; here @var{num} is the
12639 To refer to any previous value, use @samp{$} followed by the value's
12640 history number. The way @code{print} labels its output is designed to
12641 remind you of this. Just @code{$} refers to the most recent value in
12642 the history, and @code{$$} refers to the value before that.
12643 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12644 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12645 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12647 For example, suppose you have just printed a pointer to a structure and
12648 want to see the contents of the structure. It suffices to type
12654 If you have a chain of structures where the component @code{next} points
12655 to the next one, you can print the contents of the next one with this:
12662 You can print successive links in the chain by repeating this
12663 command---which you can do by just typing @key{RET}.
12665 Note that the history records values, not expressions. If the value of
12666 @code{x} is 4 and you type these commands:
12674 then the value recorded in the value history by the @code{print} command
12675 remains 4 even though the value of @code{x} has changed.
12678 @kindex show values
12680 Print the last ten values in the value history, with their item numbers.
12681 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12682 values} does not change the history.
12684 @item show values @var{n}
12685 Print ten history values centered on history item number @var{n}.
12687 @item show values +
12688 Print ten history values just after the values last printed. If no more
12689 values are available, @code{show values +} produces no display.
12692 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12693 same effect as @samp{show values +}.
12695 @node Convenience Vars
12696 @section Convenience Variables
12698 @cindex convenience variables
12699 @cindex user-defined variables
12700 @value{GDBN} provides @dfn{convenience variables} that you can use within
12701 @value{GDBN} to hold on to a value and refer to it later. These variables
12702 exist entirely within @value{GDBN}; they are not part of your program, and
12703 setting a convenience variable has no direct effect on further execution
12704 of your program. That is why you can use them freely.
12706 Convenience variables are prefixed with @samp{$}. Any name preceded by
12707 @samp{$} can be used for a convenience variable, unless it is one of
12708 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12709 (Value history references, in contrast, are @emph{numbers} preceded
12710 by @samp{$}. @xref{Value History, ,Value History}.)
12712 You can save a value in a convenience variable with an assignment
12713 expression, just as you would set a variable in your program.
12717 set $foo = *object_ptr
12721 would save in @code{$foo} the value contained in the object pointed to by
12724 Using a convenience variable for the first time creates it, but its
12725 value is @code{void} until you assign a new value. You can alter the
12726 value with another assignment at any time.
12728 Convenience variables have no fixed types. You can assign a convenience
12729 variable any type of value, including structures and arrays, even if
12730 that variable already has a value of a different type. The convenience
12731 variable, when used as an expression, has the type of its current value.
12734 @kindex show convenience
12735 @cindex show all user variables and functions
12736 @item show convenience
12737 Print a list of convenience variables used so far, and their values,
12738 as well as a list of the convenience functions.
12739 Abbreviated @code{show conv}.
12741 @kindex init-if-undefined
12742 @cindex convenience variables, initializing
12743 @item init-if-undefined $@var{variable} = @var{expression}
12744 Set a convenience variable if it has not already been set. This is useful
12745 for user-defined commands that keep some state. It is similar, in concept,
12746 to using local static variables with initializers in C (except that
12747 convenience variables are global). It can also be used to allow users to
12748 override default values used in a command script.
12750 If the variable is already defined then the expression is not evaluated so
12751 any side-effects do not occur.
12754 One of the ways to use a convenience variable is as a counter to be
12755 incremented or a pointer to be advanced. For example, to print
12756 a field from successive elements of an array of structures:
12760 print bar[$i++]->contents
12764 Repeat that command by typing @key{RET}.
12766 Some convenience variables are created automatically by @value{GDBN} and given
12767 values likely to be useful.
12770 @vindex $_@r{, convenience variable}
12772 The variable @code{$_} is automatically set by the @code{x} command to
12773 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12774 commands which provide a default address for @code{x} to examine also
12775 set @code{$_} to that address; these commands include @code{info line}
12776 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12777 except when set by the @code{x} command, in which case it is a pointer
12778 to the type of @code{$__}.
12780 @vindex $__@r{, convenience variable}
12782 The variable @code{$__} is automatically set by the @code{x} command
12783 to the value found in the last address examined. Its type is chosen
12784 to match the format in which the data was printed.
12787 @vindex $_exitcode@r{, convenience variable}
12788 When the program being debugged terminates normally, @value{GDBN}
12789 automatically sets this variable to the exit code of the program, and
12790 resets @code{$_exitsignal} to @code{void}.
12793 @vindex $_exitsignal@r{, convenience variable}
12794 When the program being debugged dies due to an uncaught signal,
12795 @value{GDBN} automatically sets this variable to that signal's number,
12796 and resets @code{$_exitcode} to @code{void}.
12798 To distinguish between whether the program being debugged has exited
12799 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12800 @code{$_exitsignal} is not @code{void}), the convenience function
12801 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12802 Functions}). For example, considering the following source code:
12805 #include <signal.h>
12808 main (int argc, char *argv[])
12815 A valid way of telling whether the program being debugged has exited
12816 or signalled would be:
12819 (@value{GDBP}) define has_exited_or_signalled
12820 Type commands for definition of ``has_exited_or_signalled''.
12821 End with a line saying just ``end''.
12822 >if $_isvoid ($_exitsignal)
12823 >echo The program has exited\n
12825 >echo The program has signalled\n
12831 Program terminated with signal SIGALRM, Alarm clock.
12832 The program no longer exists.
12833 (@value{GDBP}) has_exited_or_signalled
12834 The program has signalled
12837 As can be seen, @value{GDBN} correctly informs that the program being
12838 debugged has signalled, since it calls @code{raise} and raises a
12839 @code{SIGALRM} signal. If the program being debugged had not called
12840 @code{raise}, then @value{GDBN} would report a normal exit:
12843 (@value{GDBP}) has_exited_or_signalled
12844 The program has exited
12848 The variable @code{$_exception} is set to the exception object being
12849 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12851 @item $_ada_exception
12852 The variable @code{$_ada_exception} is set to the address of the
12853 exception being caught or thrown at an Ada exception-related
12854 catchpoint. @xref{Set Catchpoints}.
12857 @itemx $_probe_arg0@dots{}$_probe_arg11
12858 Arguments to a static probe. @xref{Static Probe Points}.
12861 @vindex $_sdata@r{, inspect, convenience variable}
12862 The variable @code{$_sdata} contains extra collected static tracepoint
12863 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12864 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12865 if extra static tracepoint data has not been collected.
12868 @vindex $_siginfo@r{, convenience variable}
12869 The variable @code{$_siginfo} contains extra signal information
12870 (@pxref{extra signal information}). Note that @code{$_siginfo}
12871 could be empty, if the application has not yet received any signals.
12872 For example, it will be empty before you execute the @code{run} command.
12875 @vindex $_tlb@r{, convenience variable}
12876 The variable @code{$_tlb} is automatically set when debugging
12877 applications running on MS-Windows in native mode or connected to
12878 gdbserver that supports the @code{qGetTIBAddr} request.
12879 @xref{General Query Packets}.
12880 This variable contains the address of the thread information block.
12883 The number of the current inferior. @xref{Inferiors Connections and
12884 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12887 The thread number of the current thread. @xref{thread numbers}.
12890 The global number of the current thread. @xref{global thread numbers}.
12892 @item $_inferior_thread_count
12893 The number of live threads in the current inferior. @xref{Threads}.
12897 @vindex $_gdb_major@r{, convenience variable}
12898 @vindex $_gdb_minor@r{, convenience variable}
12899 The major and minor version numbers of the running @value{GDBN}.
12900 Development snapshots and pretest versions have their minor version
12901 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12902 the value 12 for @code{$_gdb_minor}. These variables allow you to
12903 write scripts that work with different versions of @value{GDBN}
12904 without errors caused by features unavailable in some of those
12907 @item $_shell_exitcode
12908 @itemx $_shell_exitsignal
12909 @vindex $_shell_exitcode@r{, convenience variable}
12910 @vindex $_shell_exitsignal@r{, convenience variable}
12911 @cindex shell command, exit code
12912 @cindex shell command, exit signal
12913 @cindex exit status of shell commands
12914 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12915 shell commands. When a launched command terminates, @value{GDBN}
12916 automatically maintains the variables @code{$_shell_exitcode}
12917 and @code{$_shell_exitsignal} according to the exit status of the last
12918 launched command. These variables are set and used similarly to
12919 the variables @code{$_exitcode} and @code{$_exitsignal}.
12923 @node Convenience Funs
12924 @section Convenience Functions
12926 @cindex convenience functions
12927 @value{GDBN} also supplies some @dfn{convenience functions}. These
12928 have a syntax similar to convenience variables. A convenience
12929 function can be used in an expression just like an ordinary function;
12930 however, a convenience function is implemented internally to
12933 These functions do not require @value{GDBN} to be configured with
12934 @code{Python} support, which means that they are always available.
12938 @findex $_isvoid@r{, convenience function}
12939 @item $_isvoid (@var{expr})
12940 Return one if the expression @var{expr} is @code{void}. Otherwise it
12943 A @code{void} expression is an expression where the type of the result
12944 is @code{void}. For example, you can examine a convenience variable
12945 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12949 (@value{GDBP}) print $_exitcode
12951 (@value{GDBP}) print $_isvoid ($_exitcode)
12954 Starting program: ./a.out
12955 [Inferior 1 (process 29572) exited normally]
12956 (@value{GDBP}) print $_exitcode
12958 (@value{GDBP}) print $_isvoid ($_exitcode)
12962 In the example above, we used @code{$_isvoid} to check whether
12963 @code{$_exitcode} is @code{void} before and after the execution of the
12964 program being debugged. Before the execution there is no exit code to
12965 be examined, therefore @code{$_exitcode} is @code{void}. After the
12966 execution the program being debugged returned zero, therefore
12967 @code{$_exitcode} is zero, which means that it is not @code{void}
12970 The @code{void} expression can also be a call of a function from the
12971 program being debugged. For example, given the following function:
12980 The result of calling it inside @value{GDBN} is @code{void}:
12983 (@value{GDBP}) print foo ()
12985 (@value{GDBP}) print $_isvoid (foo ())
12987 (@value{GDBP}) set $v = foo ()
12988 (@value{GDBP}) print $v
12990 (@value{GDBP}) print $_isvoid ($v)
12994 @findex $_gdb_setting_str@r{, convenience function}
12995 @item $_gdb_setting_str (@var{setting})
12996 Return the value of the @value{GDBN} @var{setting} as a string.
12997 @var{setting} is any setting that can be used in a @code{set} or
12998 @code{show} command (@pxref{Controlling GDB}).
13001 (@value{GDBP}) show print frame-arguments
13002 Printing of non-scalar frame arguments is "scalars".
13003 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
13005 (@value{GDBP}) p $_gdb_setting_str("height")
13010 @findex $_gdb_setting@r{, convenience function}
13011 @item $_gdb_setting (@var{setting})
13012 Return the value of the @value{GDBN} @var{setting}.
13013 The type of the returned value depends on the setting.
13015 The value type for boolean and auto boolean settings is @code{int}.
13016 The boolean values @code{off} and @code{on} are converted to
13017 the integer values @code{0} and @code{1}. The value @code{auto} is
13018 converted to the value @code{-1}.
13020 The value type for integer settings is either @code{unsigned int}
13021 or @code{int}, depending on the setting.
13023 Some integer settings accept an @code{unlimited} value.
13024 Depending on the setting, the @code{set} command also accepts
13025 the value @code{0} or the value @code{@minus{}1} as a synonym for
13027 For example, @code{set height unlimited} is equivalent to
13028 @code{set height 0}.
13030 Some other settings that accept the @code{unlimited} value
13031 use the value @code{0} to literally mean zero.
13032 For example, @code{set history size 0} indicates to not
13033 record any @value{GDBN} commands in the command history.
13034 For such settings, @code{@minus{}1} is the synonym
13035 for @code{unlimited}.
13037 See the documentation of the corresponding @code{set} command for
13038 the numerical value equivalent to @code{unlimited}.
13040 The @code{$_gdb_setting} function converts the unlimited value
13041 to a @code{0} or a @code{@minus{}1} value according to what the
13042 @code{set} command uses.
13046 (@value{GDBP}) p $_gdb_setting_str("height")
13048 (@value{GDBP}) p $_gdb_setting("height")
13050 (@value{GDBP}) set height unlimited
13051 (@value{GDBP}) p $_gdb_setting_str("height")
13053 (@value{GDBP}) p $_gdb_setting("height")
13057 (@value{GDBP}) p $_gdb_setting_str("history size")
13059 (@value{GDBP}) p $_gdb_setting("history size")
13061 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
13063 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
13069 Other setting types (enum, filename, optional filename, string, string noescape)
13070 are returned as string values.
13073 @findex $_gdb_maint_setting_str@r{, convenience function}
13074 @item $_gdb_maint_setting_str (@var{setting})
13075 Like the @code{$_gdb_setting_str} function, but works with
13076 @code{maintenance set} variables.
13078 @findex $_gdb_maint_setting@r{, convenience function}
13079 @item $_gdb_maint_setting (@var{setting})
13080 Like the @code{$_gdb_setting} function, but works with
13081 @code{maintenance set} variables.
13083 @anchor{$_shell convenience function}
13084 @findex $_shell@r{, convenience function}
13085 @item $_shell (@var{command-string})
13087 Invoke a shell to execute @var{command-string}. @var{command-string}
13088 must be a string. The shell runs on the host machine, the machine
13089 @value{GDBN} is running on. Returns the command's exit status. On
13090 Unix systems, a command which exits with a zero exit status has
13091 succeeded, and non-zero exit status indicates failure. When a command
13092 terminates on a fatal signal whose number is @var{N}, @value{GDBN}
13093 uses the value 128+@var{N} as the exit status, as is standard in Unix
13094 shells. Note that @var{N} is a host signal number, not a target
13095 signal number. If you're native debugging, they will be the same, but
13096 if cross debugging, the host vs target signal numbers may be
13097 completely unrelated. Please consult your host operating system's
13098 documentation for the mapping between host signal numbers and signal
13099 names. The shell to run is determined in the same way as for the
13100 @code{shell} command. @xref{Shell Commands, ,Shell Commands}.
13103 (@value{GDBP}) print $_shell("true")
13105 (@value{GDBP}) print $_shell("false")
13107 (@value{GDBP}) p $_shell("echo hello")
13110 (@value{GDBP}) p $_shell("foobar")
13111 bash: line 1: foobar: command not found
13115 This may also be useful in breakpoint conditions. For example:
13118 (@value{GDBP}) break function if $_shell("some command") == 0
13121 In this scenario, you'll want to make sure that the shell command you
13122 run in the breakpoint condition takes the least amount of time
13123 possible. For example, avoid running a command that may block
13124 indefinitely, or that sleeps for a while before exiting. Prefer a
13125 command or script which analyzes some state and exits immediately.
13126 This is important because the debugged program stops for the
13127 breakpoint every time, and then @value{GDBN} evaluates the breakpoint
13128 condition. If the condition is false, the program is re-resumed
13129 transparently, without informing you of the stop. A quick shell
13130 command thus avoids significantly slowing down the debugged program
13133 Note: unlike the @code{shell} command, the @code{$_shell} convenience
13134 function does not affect the @code{$_shell_exitcode} and
13135 @code{$_shell_exitsignal} convenience variables.
13139 The following functions require @value{GDBN} to be configured with
13140 @code{Python} support.
13144 @findex $_memeq@r{, convenience function}
13145 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
13146 Returns one if the @var{length} bytes at the addresses given by
13147 @var{buf1} and @var{buf2} are equal.
13148 Otherwise it returns zero.
13150 @findex $_regex@r{, convenience function}
13151 @item $_regex(@var{str}, @var{regex})
13152 Returns one if the string @var{str} matches the regular expression
13153 @var{regex}. Otherwise it returns zero.
13154 The syntax of the regular expression is that specified by @code{Python}'s
13155 regular expression support.
13157 @findex $_streq@r{, convenience function}
13158 @item $_streq(@var{str1}, @var{str2})
13159 Returns one if the strings @var{str1} and @var{str2} are equal.
13160 Otherwise it returns zero.
13162 @findex $_strlen@r{, convenience function}
13163 @item $_strlen(@var{str})
13164 Returns the length of string @var{str}.
13166 @findex $_caller_is@r{, convenience function}
13167 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
13168 Returns one if the calling function's name is equal to @var{name}.
13169 Otherwise it returns zero.
13171 If the optional argument @var{number_of_frames} is provided,
13172 it is the number of frames up in the stack to look.
13178 (@value{GDBP}) backtrace
13180 at testsuite/gdb.python/py-caller-is.c:21
13181 #1 0x00000000004005a0 in middle_func ()
13182 at testsuite/gdb.python/py-caller-is.c:27
13183 #2 0x00000000004005ab in top_func ()
13184 at testsuite/gdb.python/py-caller-is.c:33
13185 #3 0x00000000004005b6 in main ()
13186 at testsuite/gdb.python/py-caller-is.c:39
13187 (@value{GDBP}) print $_caller_is ("middle_func")
13189 (@value{GDBP}) print $_caller_is ("top_func", 2)
13193 @findex $_caller_matches@r{, convenience function}
13194 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
13195 Returns one if the calling function's name matches the regular expression
13196 @var{regexp}. Otherwise it returns zero.
13198 If the optional argument @var{number_of_frames} is provided,
13199 it is the number of frames up in the stack to look.
13202 @findex $_any_caller_is@r{, convenience function}
13203 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
13204 Returns one if any calling function's name is equal to @var{name}.
13205 Otherwise it returns zero.
13207 If the optional argument @var{number_of_frames} is provided,
13208 it is the number of frames up in the stack to look.
13211 This function differs from @code{$_caller_is} in that this function
13212 checks all stack frames from the immediate caller to the frame specified
13213 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
13214 frame specified by @var{number_of_frames}.
13216 @findex $_any_caller_matches@r{, convenience function}
13217 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
13218 Returns one if any calling function's name matches the regular expression
13219 @var{regexp}. Otherwise it returns zero.
13221 If the optional argument @var{number_of_frames} is provided,
13222 it is the number of frames up in the stack to look.
13225 This function differs from @code{$_caller_matches} in that this function
13226 checks all stack frames from the immediate caller to the frame specified
13227 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
13228 frame specified by @var{number_of_frames}.
13230 @findex $_as_string@r{, convenience function}
13231 @item $_as_string(@var{value})
13232 This convenience function is considered deprecated, and could be
13233 removed from future versions of @value{GDBN}. Use the @samp{%V} format
13234 specifier instead (@pxref{%V Format Specifier}).
13236 Return the string representation of @var{value}.
13238 This function is useful to obtain the textual label (enumerator) of an
13239 enumeration value. For example, assuming the variable @var{node} is of
13240 an enumerated type:
13243 (@value{GDBP}) printf "Visiting node of type %s\n", $_as_string(node)
13244 Visiting node of type NODE_INTEGER
13247 @findex $_cimag@r{, convenience function}
13248 @findex $_creal@r{, convenience function}
13249 @item $_cimag(@var{value})
13250 @itemx $_creal(@var{value})
13251 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
13252 the complex number @var{value}.
13254 The type of the imaginary or real part depends on the type of the
13255 complex number, e.g., using @code{$_cimag} on a @code{float complex}
13256 will return an imaginary part of type @code{float}.
13260 @value{GDBN} provides the ability to list and get help on
13261 convenience functions.
13264 @item help function
13265 @kindex help function
13266 @cindex show all convenience functions
13267 Print a list of all convenience functions.
13274 You can refer to machine register contents, in expressions, as variables
13275 with names starting with @samp{$}. The names of registers are different
13276 for each machine; use @code{info registers} to see the names used on
13280 @kindex info registers
13281 @item info registers
13282 Print the names and values of all registers except floating-point
13283 and vector registers (in the selected stack frame).
13285 @kindex info all-registers
13286 @cindex floating point registers
13287 @item info all-registers
13288 Print the names and values of all registers, including floating-point
13289 and vector registers (in the selected stack frame).
13291 @anchor{info_registers_reggroup}
13292 @item info registers @var{reggroup} @dots{}
13293 Print the name and value of the registers in each of the specified
13294 @var{reggroup}s. The @var{reggroup} can be any of those returned by
13295 @code{maint print reggroups} (@pxref{Maintenance Commands}).
13297 @item info registers @var{regname} @dots{}
13298 Print the @dfn{relativized} value of each specified register @var{regname}.
13299 As discussed in detail below, register values are normally relative to
13300 the selected stack frame. The @var{regname} may be any register name valid on
13301 the machine you are using, with or without the initial @samp{$}.
13304 @anchor{standard registers}
13305 @cindex stack pointer register
13306 @cindex program counter register
13307 @cindex process status register
13308 @cindex frame pointer register
13309 @cindex standard registers
13310 @value{GDBN} has four ``standard'' register names that are available (in
13311 expressions) on most machines---whenever they do not conflict with an
13312 architecture's canonical mnemonics for registers. The register names
13313 @code{$pc} and @code{$sp} are used for the program counter register and
13314 the stack pointer. @code{$fp} is used for a register that contains a
13315 pointer to the current stack frame, and @code{$ps} is used for a
13316 register that contains the processor status. For example,
13317 you could print the program counter in hex with
13324 or print the instruction to be executed next with
13331 or add four to the stack pointer@footnote{This is a way of removing
13332 one word from the stack, on machines where stacks grow downward in
13333 memory (most machines, nowadays). This assumes that the innermost
13334 stack frame is selected; setting @code{$sp} is not allowed when other
13335 stack frames are selected. To pop entire frames off the stack,
13336 regardless of machine architecture, use @code{return};
13337 see @ref{Returning, ,Returning from a Function}.} with
13343 Whenever possible, these four standard register names are available on
13344 your machine even though the machine has different canonical mnemonics,
13345 so long as there is no conflict. The @code{info registers} command
13346 shows the canonical names. For example, on the SPARC, @code{info
13347 registers} displays the processor status register as @code{$psr} but you
13348 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
13349 is an alias for the @sc{eflags} register.
13351 @value{GDBN} always considers the contents of an ordinary register as an
13352 integer when the register is examined in this way. Some machines have
13353 special registers which can hold nothing but floating point; these
13354 registers are considered to have floating point values. There is no way
13355 to refer to the contents of an ordinary register as floating point value
13356 (although you can @emph{print} it as a floating point value with
13357 @samp{print/f $@var{regname}}).
13359 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13360 means that the data format in which the register contents are saved by
13361 the operating system is not the same one that your program normally
13362 sees. For example, the registers of the 68881 floating point
13363 coprocessor are always saved in ``extended'' (raw) format, but all C
13364 programs expect to work with ``double'' (virtual) format. In such
13365 cases, @value{GDBN} normally works with the virtual format only (the format
13366 that makes sense for your program), but the @code{info registers} command
13367 prints the data in both formats.
13369 @cindex SSE registers (x86)
13370 @cindex MMX registers (x86)
13371 Some machines have special registers whose contents can be interpreted
13372 in several different ways. For example, modern x86-based machines
13373 have SSE and MMX registers that can hold several values packed
13374 together in several different formats. @value{GDBN} refers to such
13375 registers in @code{struct} notation:
13378 (@value{GDBP}) print $xmm1
13380 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13381 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13382 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13383 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13384 v4_int32 = @{0, 20657912, 11, 13@},
13385 v2_int64 = @{88725056443645952, 55834574859@},
13386 uint128 = 0x0000000d0000000b013b36f800000000
13391 To set values of such registers, you need to tell @value{GDBN} which
13392 view of the register you wish to change, as if you were assigning
13393 value to a @code{struct} member:
13396 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13399 Normally, register values are relative to the selected stack frame
13400 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13401 value that the register would contain if all stack frames farther in
13402 were exited and their saved registers restored. In order to see the
13403 true contents of hardware registers, you must select the innermost
13404 frame (with @samp{frame 0}).
13406 @cindex caller-saved registers
13407 @cindex call-clobbered registers
13408 @cindex volatile registers
13409 @cindex <not saved> values
13410 Usually ABIs reserve some registers as not needed to be saved by the
13411 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13412 registers). It may therefore not be possible for @value{GDBN} to know
13413 the value a register had before the call (in other words, in the outer
13414 frame), if the register value has since been changed by the callee.
13415 @value{GDBN} tries to deduce where the inner frame saved
13416 (``callee-saved'') registers, from the debug info, unwind info, or the
13417 machine code generated by your compiler. If some register is not
13418 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13419 its own knowledge of the ABI, or because the debug/unwind info
13420 explicitly says the register's value is undefined), @value{GDBN}
13421 displays @w{@samp{<not saved>}} as the register's value. With targets
13422 that @value{GDBN} has no knowledge of the register saving convention,
13423 if a register was not saved by the callee, then its value and location
13424 in the outer frame are assumed to be the same of the inner frame.
13425 This is usually harmless, because if the register is call-clobbered,
13426 the caller either does not care what is in the register after the
13427 call, or has code to restore the value that it does care about. Note,
13428 however, that if you change such a register in the outer frame, you
13429 may also be affecting the inner frame. Also, the more ``outer'' the
13430 frame is you're looking at, the more likely a call-clobbered
13431 register's value is to be wrong, in the sense that it doesn't actually
13432 represent the value the register had just before the call.
13434 @node Floating Point Hardware
13435 @section Floating Point Hardware
13436 @cindex floating point
13438 Depending on the configuration, @value{GDBN} may be able to give
13439 you more information about the status of the floating point hardware.
13444 Display hardware-dependent information about the floating
13445 point unit. The exact contents and layout vary depending on the
13446 floating point chip. Currently, @samp{info float} is supported on
13447 the ARM and x86 machines.
13451 @section Vector Unit
13452 @cindex vector unit
13454 Depending on the configuration, @value{GDBN} may be able to give you
13455 more information about the status of the vector unit.
13458 @kindex info vector
13460 Display information about the vector unit. The exact contents and
13461 layout vary depending on the hardware.
13464 @node OS Information
13465 @section Operating System Auxiliary Information
13466 @cindex OS information
13468 @value{GDBN} provides interfaces to useful OS facilities that can help
13469 you debug your program.
13471 @cindex auxiliary vector
13472 @cindex vector, auxiliary
13473 Some operating systems supply an @dfn{auxiliary vector} to programs at
13474 startup. This is akin to the arguments and environment that you
13475 specify for a program, but contains a system-dependent variety of
13476 binary values that tell system libraries important details about the
13477 hardware, operating system, and process. Each value's purpose is
13478 identified by an integer tag; the meanings are well-known but system-specific.
13479 Depending on the configuration and operating system facilities,
13480 @value{GDBN} may be able to show you this information. For remote
13481 targets, this functionality may further depend on the remote stub's
13482 support of the @samp{qXfer:auxv:read} packet, see
13483 @ref{qXfer auxiliary vector read}.
13488 Display the auxiliary vector of the inferior, which can be either a
13489 live process or a core dump file. @value{GDBN} prints each tag value
13490 numerically, and also shows names and text descriptions for recognized
13491 tags. Some values in the vector are numbers, some bit masks, and some
13492 pointers to strings or other data. @value{GDBN} displays each value in the
13493 most appropriate form for a recognized tag, and in hexadecimal for
13494 an unrecognized tag.
13497 On some targets, @value{GDBN} can access operating system-specific
13498 information and show it to you. The types of information available
13499 will differ depending on the type of operating system running on the
13500 target. The mechanism used to fetch the data is described in
13501 @ref{Operating System Information}. For remote targets, this
13502 functionality depends on the remote stub's support of the
13503 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13507 @item info os @var{infotype}
13509 Display OS information of the requested type.
13511 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13513 @anchor{linux info os infotypes}
13515 @kindex info os cpus
13517 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13518 the available fields from /proc/cpuinfo. For each supported architecture
13519 different fields are available. Two common entries are processor which gives
13520 CPU number and bogomips; a system constant that is calculated during
13521 kernel initialization.
13523 @kindex info os files
13525 Display the list of open file descriptors on the target. For each
13526 file descriptor, @value{GDBN} prints the identifier of the process
13527 owning the descriptor, the command of the owning process, the value
13528 of the descriptor, and the target of the descriptor.
13530 @kindex info os modules
13532 Display the list of all loaded kernel modules on the target. For each
13533 module, @value{GDBN} prints the module name, the size of the module in
13534 bytes, the number of times the module is used, the dependencies of the
13535 module, the status of the module, and the address of the loaded module
13538 @kindex info os msg
13540 Display the list of all System V message queues on the target. For each
13541 message queue, @value{GDBN} prints the message queue key, the message
13542 queue identifier, the access permissions, the current number of bytes
13543 on the queue, the current number of messages on the queue, the processes
13544 that last sent and received a message on the queue, the user and group
13545 of the owner and creator of the message queue, the times at which a
13546 message was last sent and received on the queue, and the time at which
13547 the message queue was last changed.
13549 @kindex info os processes
13551 Display the list of processes on the target. For each process,
13552 @value{GDBN} prints the process identifier, the name of the user, the
13553 command corresponding to the process, and the list of processor cores
13554 that the process is currently running on. (To understand what these
13555 properties mean, for this and the following info types, please consult
13556 the general @sc{gnu}/Linux documentation.)
13558 @kindex info os procgroups
13560 Display the list of process groups on the target. For each process,
13561 @value{GDBN} prints the identifier of the process group that it belongs
13562 to, the command corresponding to the process group leader, the process
13563 identifier, and the command line of the process. The list is sorted
13564 first by the process group identifier, then by the process identifier,
13565 so that processes belonging to the same process group are grouped together
13566 and the process group leader is listed first.
13568 @kindex info os semaphores
13570 Display the list of all System V semaphore sets on the target. For each
13571 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13572 set identifier, the access permissions, the number of semaphores in the
13573 set, the user and group of the owner and creator of the semaphore set,
13574 and the times at which the semaphore set was operated upon and changed.
13576 @kindex info os shm
13578 Display the list of all System V shared-memory regions on the target.
13579 For each shared-memory region, @value{GDBN} prints the region key,
13580 the shared-memory identifier, the access permissions, the size of the
13581 region, the process that created the region, the process that last
13582 attached to or detached from the region, the current number of live
13583 attaches to the region, and the times at which the region was last
13584 attached to, detach from, and changed.
13586 @kindex info os sockets
13588 Display the list of Internet-domain sockets on the target. For each
13589 socket, @value{GDBN} prints the address and port of the local and
13590 remote endpoints, the current state of the connection, the creator of
13591 the socket, the IP address family of the socket, and the type of the
13594 @kindex info os threads
13596 Display the list of threads running on the target. For each thread,
13597 @value{GDBN} prints the identifier of the process that the thread
13598 belongs to, the command of the process, the thread identifier, and the
13599 processor core that it is currently running on. The main thread of a
13600 process is not listed.
13604 If @var{infotype} is omitted, then list the possible values for
13605 @var{infotype} and the kind of OS information available for each
13606 @var{infotype}. If the target does not return a list of possible
13607 types, this command will report an error.
13610 @node Memory Region Attributes
13611 @section Memory Region Attributes
13612 @cindex memory region attributes
13614 @dfn{Memory region attributes} allow you to describe special handling
13615 required by regions of your target's memory. @value{GDBN} uses
13616 attributes to determine whether to allow certain types of memory
13617 accesses; whether to use specific width accesses; and whether to cache
13618 target memory. By default the description of memory regions is
13619 fetched from the target (if the current target supports this), but the
13620 user can override the fetched regions.
13622 Defined memory regions can be individually enabled and disabled. When a
13623 memory region is disabled, @value{GDBN} uses the default attributes when
13624 accessing memory in that region. Similarly, if no memory regions have
13625 been defined, @value{GDBN} uses the default attributes when accessing
13628 When a memory region is defined, it is given a number to identify it;
13629 to enable, disable, or remove a memory region, you specify that number.
13633 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13634 Define a memory region bounded by @var{lower} and @var{upper} with
13635 attributes @var{attributes}@dots{}, and add it to the list of regions
13636 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13637 case: it is treated as the target's maximum memory address.
13638 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13641 Discard any user changes to the memory regions and use target-supplied
13642 regions, if available, or no regions if the target does not support.
13645 @item delete mem @var{nums}@dots{}
13646 Remove memory regions @var{nums}@dots{} from the list of regions
13647 monitored by @value{GDBN}.
13649 @kindex disable mem
13650 @item disable mem @var{nums}@dots{}
13651 Disable monitoring of memory regions @var{nums}@dots{}.
13652 A disabled memory region is not forgotten.
13653 It may be enabled again later.
13656 @item enable mem @var{nums}@dots{}
13657 Enable monitoring of memory regions @var{nums}@dots{}.
13661 Print a table of all defined memory regions, with the following columns
13665 @item Memory Region Number
13666 @item Enabled or Disabled.
13667 Enabled memory regions are marked with @samp{y}.
13668 Disabled memory regions are marked with @samp{n}.
13671 The address defining the inclusive lower bound of the memory region.
13674 The address defining the exclusive upper bound of the memory region.
13677 The list of attributes set for this memory region.
13682 @subsection Attributes
13684 @subsubsection Memory Access Mode
13685 The access mode attributes set whether @value{GDBN} may make read or
13686 write accesses to a memory region.
13688 While these attributes prevent @value{GDBN} from performing invalid
13689 memory accesses, they do nothing to prevent the target system, I/O DMA,
13690 etc.@: from accessing memory.
13694 Memory is read only.
13696 Memory is write only.
13698 Memory is read/write. This is the default.
13701 @subsubsection Memory Access Size
13702 The access size attribute tells @value{GDBN} to use specific sized
13703 accesses in the memory region. Often memory mapped device registers
13704 require specific sized accesses. If no access size attribute is
13705 specified, @value{GDBN} may use accesses of any size.
13709 Use 8 bit memory accesses.
13711 Use 16 bit memory accesses.
13713 Use 32 bit memory accesses.
13715 Use 64 bit memory accesses.
13718 @c @subsubsection Hardware/Software Breakpoints
13719 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13720 @c will use hardware or software breakpoints for the internal breakpoints
13721 @c used by the step, next, finish, until, etc. commands.
13725 @c Always use hardware breakpoints
13726 @c @item swbreak (default)
13729 @subsubsection Data Cache
13730 The data cache attributes set whether @value{GDBN} will cache target
13731 memory. While this generally improves performance by reducing debug
13732 protocol overhead, it can lead to incorrect results because @value{GDBN}
13733 does not know about volatile variables or memory mapped device
13738 Enable @value{GDBN} to cache target memory.
13740 Disable @value{GDBN} from caching target memory. This is the default.
13743 @subsection Memory Access Checking
13744 @value{GDBN} can be instructed to refuse accesses to memory that is
13745 not explicitly described. This can be useful if accessing such
13746 regions has undesired effects for a specific target, or to provide
13747 better error checking. The following commands control this behaviour.
13750 @kindex set mem inaccessible-by-default
13751 @item set mem inaccessible-by-default [on|off]
13752 If @code{on} is specified, make @value{GDBN} treat memory not
13753 explicitly described by the memory ranges as non-existent and refuse accesses
13754 to such memory. The checks are only performed if there's at least one
13755 memory range defined. If @code{off} is specified, make @value{GDBN}
13756 treat the memory not explicitly described by the memory ranges as RAM.
13757 The default value is @code{on}.
13758 @kindex show mem inaccessible-by-default
13759 @item show mem inaccessible-by-default
13760 Show the current handling of accesses to unknown memory.
13764 @c @subsubsection Memory Write Verification
13765 @c The memory write verification attributes set whether @value{GDBN}
13766 @c will re-reads data after each write to verify the write was successful.
13770 @c @item noverify (default)
13773 @node Dump/Restore Files
13774 @section Copy Between Memory and a File
13775 @cindex dump/restore files
13776 @cindex append data to a file
13777 @cindex dump data to a file
13778 @cindex restore data from a file
13780 You can use the commands @code{dump}, @code{append}, and
13781 @code{restore} to copy data between target memory and a file. The
13782 @code{dump} and @code{append} commands write data to a file, and the
13783 @code{restore} command reads data from a file back into the inferior's
13784 memory. Files may be in binary, Motorola S-record, Intel hex,
13785 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13786 append to binary files, and cannot read from Verilog Hex files.
13791 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13792 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13793 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13794 or the value of @var{expr}, to @var{filename} in the given format.
13796 The @var{format} parameter may be any one of:
13803 Motorola S-record format.
13805 Tektronix Hex format.
13807 Verilog Hex format.
13810 @value{GDBN} uses the same definitions of these formats as the
13811 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13812 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13816 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13817 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13818 Append the contents of memory from @var{start_addr} to @var{end_addr},
13819 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13820 (@value{GDBN} can only append data to files in raw binary form.)
13823 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13824 Restore the contents of file @var{filename} into memory. The
13825 @code{restore} command can automatically recognize any known @sc{bfd}
13826 file format, except for raw binary. To restore a raw binary file you
13827 must specify the optional keyword @code{binary} after the filename.
13829 If @var{bias} is non-zero, its value will be added to the addresses
13830 contained in the file. Binary files always start at address zero, so
13831 they will be restored at address @var{bias}. Other bfd files have
13832 a built-in location; they will be restored at offset @var{bias}
13833 from that location.
13835 If @var{start} and/or @var{end} are non-zero, then only data between
13836 file offset @var{start} and file offset @var{end} will be restored.
13837 These offsets are relative to the addresses in the file, before
13838 the @var{bias} argument is applied.
13842 @node Core File Generation
13843 @section How to Produce a Core File from Your Program
13844 @cindex dump core from inferior
13846 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13847 image of a running process and its process status (register values
13848 etc.). Its primary use is post-mortem debugging of a program that
13849 crashed while it ran outside a debugger. A program that crashes
13850 automatically produces a core file, unless this feature is disabled by
13851 the user. @xref{Files}, for information on invoking @value{GDBN} in
13852 the post-mortem debugging mode.
13854 Occasionally, you may wish to produce a core file of the program you
13855 are debugging in order to preserve a snapshot of its state.
13856 @value{GDBN} has a special command for that.
13860 @kindex generate-core-file
13861 @item generate-core-file [@var{file}]
13862 @itemx gcore [@var{file}]
13863 Produce a core dump of the inferior process. The optional argument
13864 @var{file} specifies the file name where to put the core dump. If not
13865 specified, the file name defaults to @file{core.@var{pid}}, where
13866 @var{pid} is the inferior process ID.
13868 Note that this command is implemented only for some systems (as of
13869 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13871 On @sc{gnu}/Linux, this command can take into account the value of the
13872 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13873 dump (@pxref{set use-coredump-filter}), and by default honors the
13874 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13875 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13877 @kindex set use-coredump-filter
13878 @anchor{set use-coredump-filter}
13879 @item set use-coredump-filter on
13880 @itemx set use-coredump-filter off
13881 Enable or disable the use of the file
13882 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13883 files. This file is used by the Linux kernel to decide what types of
13884 memory mappings will be dumped or ignored when generating a core dump
13885 file. @var{pid} is the process ID of a currently running process.
13887 To make use of this feature, you have to write in the
13888 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13889 which is a bit mask representing the memory mapping types. If a bit
13890 is set in the bit mask, then the memory mappings of the corresponding
13891 types will be dumped; otherwise, they will be ignored. This
13892 configuration is inherited by child processes. For more information
13893 about the bits that can be set in the
13894 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13895 manpage of @code{core(5)}.
13897 By default, this option is @code{on}. If this option is turned
13898 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13899 and instead uses the same default value as the Linux kernel in order
13900 to decide which pages will be dumped in the core dump file. This
13901 value is currently @code{0x33}, which means that bits @code{0}
13902 (anonymous private mappings), @code{1} (anonymous shared mappings),
13903 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13904 This will cause these memory mappings to be dumped automatically.
13906 @kindex set dump-excluded-mappings
13907 @anchor{set dump-excluded-mappings}
13908 @item set dump-excluded-mappings on
13909 @itemx set dump-excluded-mappings off
13910 If @code{on} is specified, @value{GDBN} will dump memory mappings
13911 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13912 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13914 The default value is @code{off}.
13917 @node Character Sets
13918 @section Character Sets
13919 @cindex character sets
13921 @cindex translating between character sets
13922 @cindex host character set
13923 @cindex target character set
13925 If the program you are debugging uses a different character set to
13926 represent characters and strings than the one @value{GDBN} uses itself,
13927 @value{GDBN} can automatically translate between the character sets for
13928 you. The character set @value{GDBN} uses we call the @dfn{host
13929 character set}; the one the inferior program uses we call the
13930 @dfn{target character set}.
13932 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13933 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13934 remote protocol (@pxref{Remote Debugging}) to debug a program
13935 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13936 then the host character set is Latin-1, and the target character set is
13937 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13938 target-charset EBCDIC-US}, then @value{GDBN} translates between
13939 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13940 character and string literals in expressions.
13942 @value{GDBN} has no way to automatically recognize which character set
13943 the inferior program uses; you must tell it, using the @code{set
13944 target-charset} command, described below.
13946 Here are the commands for controlling @value{GDBN}'s character set
13950 @item set target-charset @var{charset}
13951 @kindex set target-charset
13952 Set the current target character set to @var{charset}. To display the
13953 list of supported target character sets, type
13954 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13956 @item set host-charset @var{charset}
13957 @kindex set host-charset
13958 Set the current host character set to @var{charset}.
13960 By default, @value{GDBN} uses a host character set appropriate to the
13961 system it is running on; you can override that default using the
13962 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13963 automatically determine the appropriate host character set. In this
13964 case, @value{GDBN} uses @samp{UTF-8}.
13966 @value{GDBN} can only use certain character sets as its host character
13967 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13968 @value{GDBN} will list the host character sets it supports.
13970 @item set charset @var{charset}
13971 @kindex set charset
13972 Set the current host and target character sets to @var{charset}. As
13973 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13974 @value{GDBN} will list the names of the character sets that can be used
13975 for both host and target.
13978 @kindex show charset
13979 Show the names of the current host and target character sets.
13981 @item show host-charset
13982 @kindex show host-charset
13983 Show the name of the current host character set.
13985 @item show target-charset
13986 @kindex show target-charset
13987 Show the name of the current target character set.
13989 @item set target-wide-charset @var{charset}
13990 @kindex set target-wide-charset
13991 Set the current target's wide character set to @var{charset}. This is
13992 the character set used by the target's @code{wchar_t} type. To
13993 display the list of supported wide character sets, type
13994 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13996 @item show target-wide-charset
13997 @kindex show target-wide-charset
13998 Show the name of the current target's wide character set.
14001 Here is an example of @value{GDBN}'s character set support in action.
14002 Assume that the following source code has been placed in the file
14003 @file{charset-test.c}:
14009 = @{72, 101, 108, 108, 111, 44, 32, 119,
14010 111, 114, 108, 100, 33, 10, 0@};
14011 char ibm1047_hello[]
14012 = @{200, 133, 147, 147, 150, 107, 64, 166,
14013 150, 153, 147, 132, 90, 37, 0@};
14017 printf ("Hello, world!\n");
14021 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
14022 containing the string @samp{Hello, world!} followed by a newline,
14023 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
14025 We compile the program, and invoke the debugger on it:
14028 $ gcc -g charset-test.c -o charset-test
14029 $ gdb -nw charset-test
14030 GNU gdb 2001-12-19-cvs
14031 Copyright 2001 Free Software Foundation, Inc.
14036 We can use the @code{show charset} command to see what character sets
14037 @value{GDBN} is currently using to interpret and display characters and
14041 (@value{GDBP}) show charset
14042 The current host and target character set is `ISO-8859-1'.
14046 For the sake of printing this manual, let's use @sc{ascii} as our
14047 initial character set:
14049 (@value{GDBP}) set charset ASCII
14050 (@value{GDBP}) show charset
14051 The current host and target character set is `ASCII'.
14055 Let's assume that @sc{ascii} is indeed the correct character set for our
14056 host system --- in other words, let's assume that if @value{GDBN} prints
14057 characters using the @sc{ascii} character set, our terminal will display
14058 them properly. Since our current target character set is also
14059 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
14062 (@value{GDBP}) print ascii_hello
14063 $1 = 0x401698 "Hello, world!\n"
14064 (@value{GDBP}) print ascii_hello[0]
14069 @value{GDBN} uses the target character set for character and string
14070 literals you use in expressions:
14073 (@value{GDBP}) print '+'
14078 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
14081 @value{GDBN} relies on the user to tell it which character set the
14082 target program uses. If we print @code{ibm1047_hello} while our target
14083 character set is still @sc{ascii}, we get jibberish:
14086 (@value{GDBP}) print ibm1047_hello
14087 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
14088 (@value{GDBP}) print ibm1047_hello[0]
14093 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
14094 @value{GDBN} tells us the character sets it supports:
14097 (@value{GDBP}) set target-charset
14098 ASCII EBCDIC-US IBM1047 ISO-8859-1
14099 (@value{GDBP}) set target-charset
14102 We can select @sc{ibm1047} as our target character set, and examine the
14103 program's strings again. Now the @sc{ascii} string is wrong, but
14104 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
14105 target character set, @sc{ibm1047}, to the host character set,
14106 @sc{ascii}, and they display correctly:
14109 (@value{GDBP}) set target-charset IBM1047
14110 (@value{GDBP}) show charset
14111 The current host character set is `ASCII'.
14112 The current target character set is `IBM1047'.
14113 (@value{GDBP}) print ascii_hello
14114 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
14115 (@value{GDBP}) print ascii_hello[0]
14117 (@value{GDBP}) print ibm1047_hello
14118 $8 = 0x4016a8 "Hello, world!\n"
14119 (@value{GDBP}) print ibm1047_hello[0]
14124 As above, @value{GDBN} uses the target character set for character and
14125 string literals you use in expressions:
14128 (@value{GDBP}) print '+'
14133 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
14136 @node Caching Target Data
14137 @section Caching Data of Targets
14138 @cindex caching data of targets
14140 @value{GDBN} caches data exchanged between the debugger and a target.
14141 Each cache is associated with the address space of the inferior.
14142 @xref{Inferiors Connections and Programs}, about inferior and address space.
14143 Such caching generally improves performance in remote debugging
14144 (@pxref{Remote Debugging}), because it reduces the overhead of the
14145 remote protocol by bundling memory reads and writes into large chunks.
14146 Unfortunately, simply caching everything would lead to incorrect results,
14147 since @value{GDBN} does not necessarily know anything about volatile
14148 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
14149 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
14151 Therefore, by default, @value{GDBN} only caches data
14152 known to be on the stack@footnote{In non-stop mode, it is moderately
14153 rare for a running thread to modify the stack of a stopped thread
14154 in a way that would interfere with a backtrace, and caching of
14155 stack reads provides a significant speed up of remote backtraces.} or
14156 in the code segment.
14157 Other regions of memory can be explicitly marked as
14158 cacheable; @pxref{Memory Region Attributes}.
14161 @kindex set remotecache
14162 @item set remotecache on
14163 @itemx set remotecache off
14164 This option no longer does anything; it exists for compatibility
14167 @kindex show remotecache
14168 @item show remotecache
14169 Show the current state of the obsolete remotecache flag.
14171 @kindex set stack-cache
14172 @item set stack-cache on
14173 @itemx set stack-cache off
14174 Enable or disable caching of stack accesses. When @code{on}, use
14175 caching. By default, this option is @code{on}.
14177 @kindex show stack-cache
14178 @item show stack-cache
14179 Show the current state of data caching for memory accesses.
14181 @kindex set code-cache
14182 @item set code-cache on
14183 @itemx set code-cache off
14184 Enable or disable caching of code segment accesses. When @code{on},
14185 use caching. By default, this option is @code{on}. This improves
14186 performance of disassembly in remote debugging.
14188 @kindex show code-cache
14189 @item show code-cache
14190 Show the current state of target memory cache for code segment
14193 @kindex info dcache
14194 @item info dcache @r{[}line@r{]}
14195 Print the information about the performance of data cache of the
14196 current inferior's address space. The information displayed
14197 includes the dcache width and depth, and for each cache line, its
14198 number, address, and how many times it was referenced. This
14199 command is useful for debugging the data cache operation.
14201 If a line number is specified, the contents of that line will be
14204 @item set dcache size @var{size}
14205 @cindex dcache size
14206 @kindex set dcache size
14207 Set maximum number of entries in dcache (dcache depth above).
14209 @item set dcache line-size @var{line-size}
14210 @cindex dcache line-size
14211 @kindex set dcache line-size
14212 Set number of bytes each dcache entry caches (dcache width above).
14213 Must be a power of 2.
14215 @item show dcache size
14216 @kindex show dcache size
14217 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
14219 @item show dcache line-size
14220 @kindex show dcache line-size
14221 Show default size of dcache lines.
14223 @item maint flush dcache
14224 @cindex dcache, flushing
14225 @kindex maint flush dcache
14226 Flush the contents (if any) of the dcache. This maintainer command is
14227 useful when debugging the dcache implementation.
14231 @node Searching Memory
14232 @section Search Memory
14233 @cindex searching memory
14235 Memory can be searched for a particular sequence of bytes with the
14236 @code{find} command.
14240 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14241 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14242 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
14243 etc. The search begins at address @var{start_addr} and continues for either
14244 @var{len} bytes or through to @var{end_addr} inclusive.
14247 @var{s} and @var{n} are optional parameters.
14248 They may be specified in either order, apart or together.
14251 @item @var{s}, search query size
14252 The size of each search query value.
14258 halfwords (two bytes)
14262 giant words (eight bytes)
14265 All values are interpreted in the current language.
14266 This means, for example, that if the current source language is C/C@t{++}
14267 then searching for the string ``hello'' includes the trailing '\0'.
14268 The null terminator can be removed from searching by using casts,
14269 e.g.: @samp{@{char[5]@}"hello"}.
14271 If the value size is not specified, it is taken from the
14272 value's type in the current language.
14273 This is useful when one wants to specify the search
14274 pattern as a mixture of types.
14275 Note that this means, for example, that in the case of C-like languages
14276 a search for an untyped 0x42 will search for @samp{(int) 0x42}
14277 which is typically four bytes.
14279 @item @var{n}, maximum number of finds
14280 The maximum number of matches to print. The default is to print all finds.
14283 You can use strings as search values. Quote them with double-quotes
14285 The string value is copied into the search pattern byte by byte,
14286 regardless of the endianness of the target and the size specification.
14288 The address of each match found is printed as well as a count of the
14289 number of matches found.
14291 The address of the last value found is stored in convenience variable
14293 A count of the number of matches is stored in @samp{$numfound}.
14295 For example, if stopped at the @code{printf} in this function:
14301 static char hello[] = "hello-hello";
14302 static struct @{ char c; short s; int i; @}
14303 __attribute__ ((packed)) mixed
14304 = @{ 'c', 0x1234, 0x87654321 @};
14305 printf ("%s\n", hello);
14310 you get during debugging:
14313 (@value{GDBP}) find &hello[0], +sizeof(hello), "hello"
14314 0x804956d <hello.1620+6>
14316 (@value{GDBP}) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
14317 0x8049567 <hello.1620>
14318 0x804956d <hello.1620+6>
14320 (@value{GDBP}) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
14321 0x8049567 <hello.1620>
14322 0x804956d <hello.1620+6>
14324 (@value{GDBP}) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
14325 0x8049567 <hello.1620>
14327 (@value{GDBP}) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
14328 0x8049560 <mixed.1625>
14330 (@value{GDBP}) print $numfound
14332 (@value{GDBP}) print $_
14333 $2 = (void *) 0x8049560
14337 @section Value Sizes
14339 Whenever @value{GDBN} prints a value memory will be allocated within
14340 @value{GDBN} to hold the contents of the value. It is possible in
14341 some languages with dynamic typing systems, that an invalid program
14342 may indicate a value that is incorrectly large, this in turn may cause
14343 @value{GDBN} to try and allocate an overly large amount of memory.
14346 @anchor{set max-value-size}
14347 @kindex set max-value-size
14348 @item set max-value-size @var{bytes}
14349 @itemx set max-value-size unlimited
14350 Set the maximum size of memory that @value{GDBN} will allocate for the
14351 contents of a value to @var{bytes}, trying to display a value that
14352 requires more memory than that will result in an error.
14354 Setting this variable does not effect values that have already been
14355 allocated within @value{GDBN}, only future allocations.
14357 There's a minimum size that @code{max-value-size} can be set to in
14358 order that @value{GDBN} can still operate correctly, this minimum is
14359 currently 16 bytes.
14361 The limit applies to the results of some subexpressions as well as to
14362 complete expressions. For example, an expression denoting a simple
14363 integer component, such as @code{x.y.z}, may fail if the size of
14364 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14365 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14366 @var{A} is an array variable with non-constant size, will generally
14367 succeed regardless of the bounds on @var{A}, as long as the component
14368 size is less than @var{bytes}.
14370 The default value of @code{max-value-size} is currently 64k.
14372 @kindex show max-value-size
14373 @item show max-value-size
14374 Show the maximum size of memory, in bytes, that @value{GDBN} will
14375 allocate for the contents of a value.
14378 @node Optimized Code
14379 @chapter Debugging Optimized Code
14380 @cindex optimized code, debugging
14381 @cindex debugging optimized code
14383 Almost all compilers support optimization. With optimization
14384 disabled, the compiler generates assembly code that corresponds
14385 directly to your source code, in a simplistic way. As the compiler
14386 applies more powerful optimizations, the generated assembly code
14387 diverges from your original source code. With help from debugging
14388 information generated by the compiler, @value{GDBN} can map from
14389 the running program back to constructs from your original source.
14391 @value{GDBN} is more accurate with optimization disabled. If you
14392 can recompile without optimization, it is easier to follow the
14393 progress of your program during debugging. But, there are many cases
14394 where you may need to debug an optimized version.
14396 When you debug a program compiled with @samp{-g -O}, remember that the
14397 optimizer has rearranged your code; the debugger shows you what is
14398 really there. Do not be too surprised when the execution path does not
14399 exactly match your source file! An extreme example: if you define a
14400 variable, but never use it, @value{GDBN} never sees that
14401 variable---because the compiler optimizes it out of existence.
14403 Some things do not work as well with @samp{-g -O} as with just
14404 @samp{-g}, particularly on machines with instruction scheduling. If in
14405 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14406 please report it to us as a bug (including a test case!).
14407 @xref{Variables}, for more information about debugging optimized code.
14410 * Inline Functions:: How @value{GDBN} presents inlining
14411 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14414 @node Inline Functions
14415 @section Inline Functions
14416 @cindex inline functions, debugging
14418 @dfn{Inlining} is an optimization that inserts a copy of the function
14419 body directly at each call site, instead of jumping to a shared
14420 routine. @value{GDBN} displays inlined functions just like
14421 non-inlined functions. They appear in backtraces. You can view their
14422 arguments and local variables, step into them with @code{step}, skip
14423 them with @code{next}, and escape from them with @code{finish}.
14424 You can check whether a function was inlined by using the
14425 @code{info frame} command.
14427 For @value{GDBN} to support inlined functions, the compiler must
14428 record information about inlining in the debug information ---
14429 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14430 other compilers do also. @value{GDBN} only supports inlined functions
14431 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14432 do not emit two required attributes (@samp{DW_AT_call_file} and
14433 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14434 function calls with earlier versions of @value{NGCC}. It instead
14435 displays the arguments and local variables of inlined functions as
14436 local variables in the caller.
14438 The body of an inlined function is directly included at its call site;
14439 unlike a non-inlined function, there are no instructions devoted to
14440 the call. @value{GDBN} still pretends that the call site and the
14441 start of the inlined function are different instructions. Stepping to
14442 the call site shows the call site, and then stepping again shows
14443 the first line of the inlined function, even though no additional
14444 instructions are executed.
14446 This makes source-level debugging much clearer; you can see both the
14447 context of the call and then the effect of the call. Only stepping by
14448 a single instruction using @code{stepi} or @code{nexti} does not do
14449 this; single instruction steps always show the inlined body.
14451 There are some ways that @value{GDBN} does not pretend that inlined
14452 function calls are the same as normal calls:
14456 Setting breakpoints at the call site of an inlined function may not
14457 work, because the call site does not contain any code. @value{GDBN}
14458 may incorrectly move the breakpoint to the next line of the enclosing
14459 function, after the call. This limitation will be removed in a future
14460 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14461 or inside the inlined function instead.
14464 @value{GDBN} cannot locate the return value of inlined calls after
14465 using the @code{finish} command. This is a limitation of compiler-generated
14466 debugging information; after @code{finish}, you can step to the next line
14467 and print a variable where your program stored the return value.
14471 @node Tail Call Frames
14472 @section Tail Call Frames
14473 @cindex tail call frames, debugging
14475 Function @code{B} can call function @code{C} in its very last statement. In
14476 unoptimized compilation the call of @code{C} is immediately followed by return
14477 instruction at the end of @code{B} code. Optimizing compiler may replace the
14478 call and return in function @code{B} into one jump to function @code{C}
14479 instead. Such use of a jump instruction is called @dfn{tail call}.
14481 During execution of function @code{C}, there will be no indication in the
14482 function call stack frames that it was tail-called from @code{B}. If function
14483 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14484 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14485 some cases @value{GDBN} can determine that @code{C} was tail-called from
14486 @code{B}, and it will then create fictitious call frame for that, with the
14487 return address set up as if @code{B} called @code{C} normally.
14489 This functionality is currently supported only by DWARF 2 debugging format and
14490 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14491 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14494 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14495 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14498 (@value{GDBP}) x/i $pc - 2
14499 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14500 (@value{GDBP}) info frame
14501 Stack level 1, frame at 0x7fffffffda30:
14502 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14503 tail call frame, caller of frame at 0x7fffffffda30
14504 source language c++.
14505 Arglist at unknown address.
14506 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14509 The detection of all the possible code path executions can find them ambiguous.
14510 There is no execution history stored (possible @ref{Reverse Execution} is never
14511 used for this purpose) and the last known caller could have reached the known
14512 callee by multiple different jump sequences. In such case @value{GDBN} still
14513 tries to show at least all the unambiguous top tail callers and all the
14514 unambiguous bottom tail calees, if any.
14517 @anchor{set debug entry-values}
14518 @item set debug entry-values
14519 @kindex set debug entry-values
14520 When set to on, enables printing of analysis messages for both frame argument
14521 values at function entry and tail calls. It will show all the possible valid
14522 tail calls code paths it has considered. It will also print the intersection
14523 of them with the final unambiguous (possibly partial or even empty) code path
14526 @item show debug entry-values
14527 @kindex show debug entry-values
14528 Show the current state of analysis messages printing for both frame argument
14529 values at function entry and tail calls.
14532 The analysis messages for tail calls can for example show why the virtual tail
14533 call frame for function @code{c} has not been recognized (due to the indirect
14534 reference by variable @code{x}):
14537 static void __attribute__((noinline, noclone)) c (void);
14538 void (*x) (void) = c;
14539 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14540 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14541 int main (void) @{ x (); return 0; @}
14543 Breakpoint 1, DW_OP_entry_value resolving cannot find
14544 DW_TAG_call_site 0x40039a in main
14546 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14549 #1 0x000000000040039a in main () at t.c:5
14552 Another possibility is an ambiguous virtual tail call frames resolution:
14556 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14557 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14558 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14559 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14560 static void __attribute__((noinline, noclone)) b (void)
14561 @{ if (i) c (); else e (); @}
14562 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14563 int main (void) @{ a (); return 0; @}
14565 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14566 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14567 tailcall: reduced: 0x4004d2(a) |
14570 #1 0x00000000004004d2 in a () at t.c:8
14571 #2 0x0000000000400395 in main () at t.c:9
14574 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14575 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14577 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14578 @ifset HAVE_MAKEINFO_CLICK
14579 @set ARROW @click{}
14580 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14581 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14583 @ifclear HAVE_MAKEINFO_CLICK
14585 @set CALLSEQ1B @value{CALLSEQ1A}
14586 @set CALLSEQ2B @value{CALLSEQ2A}
14589 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14590 The code can have possible execution paths @value{CALLSEQ1B} or
14591 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14593 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14594 has found. It then finds another possible calling sequence - that one is
14595 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14596 printed as the @code{reduced:} calling sequence. That one could have many
14597 further @code{compare:} and @code{reduced:} statements as long as there remain
14598 any non-ambiguous sequence entries.
14600 For the frame of function @code{b} in both cases there are different possible
14601 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14602 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14603 therefore this one is displayed to the user while the ambiguous frames are
14606 There can be also reasons why printing of frame argument values at function
14611 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14612 static void __attribute__((noinline, noclone)) a (int i);
14613 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14614 static void __attribute__((noinline, noclone)) a (int i)
14615 @{ if (i) b (i - 1); else c (0); @}
14616 int main (void) @{ a (5); return 0; @}
14619 #0 c (i=i@@entry=0) at t.c:2
14620 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14621 function "a" at 0x400420 can call itself via tail calls
14622 i=<optimized out>) at t.c:6
14623 #2 0x000000000040036e in main () at t.c:7
14626 @value{GDBN} cannot find out from the inferior state if and how many times did
14627 function @code{a} call itself (via function @code{b}) as these calls would be
14628 tail calls. Such tail calls would modify the @code{i} variable, therefore
14629 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14630 prints @code{<optimized out>} instead.
14633 @chapter C Preprocessor Macros
14635 Some languages, such as C and C@t{++}, provide a way to define and invoke
14636 ``preprocessor macros'' which expand into strings of tokens.
14637 @value{GDBN} can evaluate expressions containing macro invocations, show
14638 the result of macro expansion, and show a macro's definition, including
14639 where it was defined.
14641 You may need to compile your program specially to provide @value{GDBN}
14642 with information about preprocessor macros. Most compilers do not
14643 include macros in their debugging information, even when you compile
14644 with the @option{-g} flag. @xref{Compilation}.
14646 A program may define a macro at one point, remove that definition later,
14647 and then provide a different definition after that. Thus, at different
14648 points in the program, a macro may have different definitions, or have
14649 no definition at all. If there is a current stack frame, @value{GDBN}
14650 uses the macros in scope at that frame's source code line. Otherwise,
14651 @value{GDBN} uses the macros in scope at the current listing location;
14654 Whenever @value{GDBN} evaluates an expression, it always expands any
14655 macro invocations present in the expression. @value{GDBN} also provides
14656 the following commands for working with macros explicitly.
14660 @kindex macro expand
14661 @cindex macro expansion, showing the results of preprocessor
14662 @cindex preprocessor macro expansion, showing the results of
14663 @cindex expanding preprocessor macros
14664 @item macro expand @var{expression}
14665 @itemx macro exp @var{expression}
14666 Show the results of expanding all preprocessor macro invocations in
14667 @var{expression}. Since @value{GDBN} simply expands macros, but does
14668 not parse the result, @var{expression} need not be a valid expression;
14669 it can be any string of tokens.
14672 @item macro expand-once @var{expression}
14673 @itemx macro exp1 @var{expression}
14674 @cindex expand macro once
14675 @i{(This command is not yet implemented.)} Show the results of
14676 expanding those preprocessor macro invocations that appear explicitly in
14677 @var{expression}. Macro invocations appearing in that expansion are
14678 left unchanged. This command allows you to see the effect of a
14679 particular macro more clearly, without being confused by further
14680 expansions. Since @value{GDBN} simply expands macros, but does not
14681 parse the result, @var{expression} need not be a valid expression; it
14682 can be any string of tokens.
14685 @cindex macro definition, showing
14686 @cindex definition of a macro, showing
14687 @cindex macros, from debug info
14688 @item info macro [-a|-all] [--] @var{macro}
14689 Show the current definition or all definitions of the named @var{macro},
14690 and describe the source location or compiler command-line where that
14691 definition was established. The optional double dash is to signify the end of
14692 argument processing and the beginning of @var{macro} for non C-like macros where
14693 the macro may begin with a hyphen.
14695 @kindex info macros
14696 @item info macros @var{locspec}
14697 Show all macro definitions that are in effect at the source line of
14698 the code location that results from resolving @var{locspec}, and
14699 describe the source location or compiler command-line where those
14700 definitions were established.
14702 @kindex macro define
14703 @cindex user-defined macros
14704 @cindex defining macros interactively
14705 @cindex macros, user-defined
14706 @item macro define @var{macro} @var{replacement-list}
14707 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14708 Introduce a definition for a preprocessor macro named @var{macro},
14709 invocations of which are replaced by the tokens given in
14710 @var{replacement-list}. The first form of this command defines an
14711 ``object-like'' macro, which takes no arguments; the second form
14712 defines a ``function-like'' macro, which takes the arguments given in
14715 A definition introduced by this command is in scope in every
14716 expression evaluated in @value{GDBN}, until it is removed with the
14717 @code{macro undef} command, described below. The definition overrides
14718 all definitions for @var{macro} present in the program being debugged,
14719 as well as any previous user-supplied definition.
14721 @kindex macro undef
14722 @item macro undef @var{macro}
14723 Remove any user-supplied definition for the macro named @var{macro}.
14724 This command only affects definitions provided with the @code{macro
14725 define} command, described above; it cannot remove definitions present
14726 in the program being debugged.
14730 List all the macros defined using the @code{macro define} command.
14733 @cindex macros, example of debugging with
14734 Here is a transcript showing the above commands in action. First, we
14735 show our source files:
14740 #include "sample.h"
14743 #define ADD(x) (M + x)
14748 printf ("Hello, world!\n");
14750 printf ("We're so creative.\n");
14752 printf ("Goodbye, world!\n");
14759 Now, we compile the program using the @sc{gnu} C compiler,
14760 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14761 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14762 and @option{-gdwarf-4}; we recommend always choosing the most recent
14763 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14764 includes information about preprocessor macros in the debugging
14768 $ gcc -gdwarf-2 -g3 sample.c -o sample
14772 Now, we start @value{GDBN} on our sample program:
14776 GNU gdb 2002-05-06-cvs
14777 Copyright 2002 Free Software Foundation, Inc.
14778 GDB is free software, @dots{}
14782 We can expand macros and examine their definitions, even when the
14783 program is not running. @value{GDBN} uses the current listing position
14784 to decide which macro definitions are in scope:
14787 (@value{GDBP}) list main
14790 5 #define ADD(x) (M + x)
14795 10 printf ("Hello, world!\n");
14797 12 printf ("We're so creative.\n");
14798 (@value{GDBP}) info macro ADD
14799 Defined at /home/jimb/gdb/macros/play/sample.c:5
14800 #define ADD(x) (M + x)
14801 (@value{GDBP}) info macro Q
14802 Defined at /home/jimb/gdb/macros/play/sample.h:1
14803 included at /home/jimb/gdb/macros/play/sample.c:2
14805 (@value{GDBP}) macro expand ADD(1)
14806 expands to: (42 + 1)
14807 (@value{GDBP}) macro expand-once ADD(1)
14808 expands to: once (M + 1)
14812 In the example above, note that @code{macro expand-once} expands only
14813 the macro invocation explicit in the original text --- the invocation of
14814 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14815 which was introduced by @code{ADD}.
14817 Once the program is running, @value{GDBN} uses the macro definitions in
14818 force at the source line of the current stack frame:
14821 (@value{GDBP}) break main
14822 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14824 Starting program: /home/jimb/gdb/macros/play/sample
14826 Breakpoint 1, main () at sample.c:10
14827 10 printf ("Hello, world!\n");
14831 At line 10, the definition of the macro @code{N} at line 9 is in force:
14834 (@value{GDBP}) info macro N
14835 Defined at /home/jimb/gdb/macros/play/sample.c:9
14837 (@value{GDBP}) macro expand N Q M
14838 expands to: 28 < 42
14839 (@value{GDBP}) print N Q M
14844 As we step over directives that remove @code{N}'s definition, and then
14845 give it a new definition, @value{GDBN} finds the definition (or lack
14846 thereof) in force at each point:
14849 (@value{GDBP}) next
14851 12 printf ("We're so creative.\n");
14852 (@value{GDBP}) info macro N
14853 The symbol `N' has no definition as a C/C++ preprocessor macro
14854 at /home/jimb/gdb/macros/play/sample.c:12
14855 (@value{GDBP}) next
14857 14 printf ("Goodbye, world!\n");
14858 (@value{GDBP}) info macro N
14859 Defined at /home/jimb/gdb/macros/play/sample.c:13
14861 (@value{GDBP}) macro expand N Q M
14862 expands to: 1729 < 42
14863 (@value{GDBP}) print N Q M
14868 In addition to source files, macros can be defined on the compilation command
14869 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14870 such a way, @value{GDBN} displays the location of their definition as line zero
14871 of the source file submitted to the compiler.
14874 (@value{GDBP}) info macro __STDC__
14875 Defined at /home/jimb/gdb/macros/play/sample.c:0
14882 @chapter Tracepoints
14883 @c This chapter is based on the documentation written by Michael
14884 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14886 @cindex tracepoints
14887 In some applications, it is not feasible for the debugger to interrupt
14888 the program's execution long enough for the developer to learn
14889 anything helpful about its behavior. If the program's correctness
14890 depends on its real-time behavior, delays introduced by a debugger
14891 might cause the program to change its behavior drastically, or perhaps
14892 fail, even when the code itself is correct. It is useful to be able
14893 to observe the program's behavior without interrupting it.
14895 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14896 specify locations in the program, called @dfn{tracepoints}, and
14897 arbitrary expressions to evaluate when those tracepoints are reached.
14898 Later, using the @code{tfind} command, you can examine the values
14899 those expressions had when the program hit the tracepoints. The
14900 expressions may also denote objects in memory---structures or arrays,
14901 for example---whose values @value{GDBN} should record; while visiting
14902 a particular tracepoint, you may inspect those objects as if they were
14903 in memory at that moment. However, because @value{GDBN} records these
14904 values without interacting with you, it can do so quickly and
14905 unobtrusively, hopefully not disturbing the program's behavior.
14907 The tracepoint facility is currently available only for remote
14908 targets. @xref{Targets}. In addition, your remote target must know
14909 how to collect trace data. This functionality is implemented in the
14910 remote stub; however, none of the stubs distributed with @value{GDBN}
14911 support tracepoints as of this writing. The format of the remote
14912 packets used to implement tracepoints are described in @ref{Tracepoint
14915 It is also possible to get trace data from a file, in a manner reminiscent
14916 of corefiles; you specify the filename, and use @code{tfind} to search
14917 through the file. @xref{Trace Files}, for more details.
14919 This chapter describes the tracepoint commands and features.
14922 * Set Tracepoints::
14923 * Analyze Collected Data::
14924 * Tracepoint Variables::
14928 @node Set Tracepoints
14929 @section Commands to Set Tracepoints
14931 Before running such a @dfn{trace experiment}, an arbitrary number of
14932 tracepoints can be set. A tracepoint is actually a special type of
14933 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14934 standard breakpoint commands. For instance, as with breakpoints,
14935 tracepoint numbers are successive integers starting from one, and many
14936 of the commands associated with tracepoints take the tracepoint number
14937 as their argument, to identify which tracepoint to work on.
14939 For each tracepoint, you can specify, in advance, some arbitrary set
14940 of data that you want the target to collect in the trace buffer when
14941 it hits that tracepoint. The collected data can include registers,
14942 local variables, or global data. Later, you can use @value{GDBN}
14943 commands to examine the values these data had at the time the
14944 tracepoint was hit.
14946 Tracepoints do not support every breakpoint feature. Ignore counts on
14947 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14948 commands when they are hit. Tracepoints may not be thread-specific
14951 @cindex fast tracepoints
14952 Some targets may support @dfn{fast tracepoints}, which are inserted in
14953 a different way (such as with a jump instead of a trap), that is
14954 faster but possibly restricted in where they may be installed.
14956 @cindex static tracepoints
14957 @cindex markers, static tracepoints
14958 @cindex probing markers, static tracepoints
14959 Regular and fast tracepoints are dynamic tracing facilities, meaning
14960 that they can be used to insert tracepoints at (almost) any location
14961 in the target. Some targets may also support controlling @dfn{static
14962 tracepoints} from @value{GDBN}. With static tracing, a set of
14963 instrumentation points, also known as @dfn{markers}, are embedded in
14964 the target program, and can be activated or deactivated by name or
14965 address. These are usually placed at locations which facilitate
14966 investigating what the target is actually doing. @value{GDBN}'s
14967 support for static tracing includes being able to list instrumentation
14968 points, and attach them with @value{GDBN} defined high level
14969 tracepoints that expose the whole range of convenience of
14970 @value{GDBN}'s tracepoints support. Namely, support for collecting
14971 registers values and values of global or local (to the instrumentation
14972 point) variables; tracepoint conditions and trace state variables.
14973 The act of installing a @value{GDBN} static tracepoint on an
14974 instrumentation point, or marker, is referred to as @dfn{probing} a
14975 static tracepoint marker.
14977 @code{gdbserver} supports tracepoints on some target systems.
14978 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14980 This section describes commands to set tracepoints and associated
14981 conditions and actions.
14984 * Create and Delete Tracepoints::
14985 * Enable and Disable Tracepoints::
14986 * Tracepoint Passcounts::
14987 * Tracepoint Conditions::
14988 * Trace State Variables::
14989 * Tracepoint Actions::
14990 * Listing Tracepoints::
14991 * Listing Static Tracepoint Markers::
14992 * Starting and Stopping Trace Experiments::
14993 * Tracepoint Restrictions::
14996 @node Create and Delete Tracepoints
14997 @subsection Create and Delete Tracepoints
15000 @cindex set tracepoint
15002 @item trace @var{locspec}
15003 The @code{trace} command is very similar to the @code{break} command.
15004 Its argument @var{locspec} can be any valid location specification.
15005 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
15006 which is a point in the target program where the debugger will briefly stop,
15007 collect some data, and then allow the program to continue. Setting a tracepoint
15008 or changing its actions takes effect immediately if the remote stub
15009 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
15011 If remote stub doesn't support the @samp{InstallInTrace} feature, all
15012 these changes don't take effect until the next @code{tstart}
15013 command, and once a trace experiment is running, further changes will
15014 not have any effect until the next trace experiment starts. In addition,
15015 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
15016 address is not yet resolved. (This is similar to pending breakpoints.)
15017 Pending tracepoints are not downloaded to the target and not installed
15018 until they are resolved. The resolution of pending tracepoints requires
15019 @value{GDBN} support---when debugging with the remote target, and
15020 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
15021 tracing}), pending tracepoints can not be resolved (and downloaded to
15022 the remote stub) while @value{GDBN} is disconnected.
15024 Here are some examples of using the @code{trace} command:
15027 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
15029 (@value{GDBP}) @b{trace +2} // 2 lines forward
15031 (@value{GDBP}) @b{trace my_function} // first source line of function
15033 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
15035 (@value{GDBP}) @b{trace *0x2117c4} // an address
15039 You can abbreviate @code{trace} as @code{tr}.
15041 @item trace @var{locspec} if @var{cond}
15042 Set a tracepoint with condition @var{cond}; evaluate the expression
15043 @var{cond} each time the tracepoint is reached, and collect data only
15044 if the value is nonzero---that is, if @var{cond} evaluates as true.
15045 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
15046 information on tracepoint conditions.
15048 @item ftrace @var{locspec} [ if @var{cond} ]
15049 @cindex set fast tracepoint
15050 @cindex fast tracepoints, setting
15052 The @code{ftrace} command sets a fast tracepoint. For targets that
15053 support them, fast tracepoints will use a more efficient but possibly
15054 less general technique to trigger data collection, such as a jump
15055 instruction instead of a trap, or some sort of hardware support. It
15056 may not be possible to create a fast tracepoint at the desired
15057 location, in which case the command will exit with an explanatory
15060 @value{GDBN} handles arguments to @code{ftrace} exactly as for
15063 On 32-bit x86-architecture systems, fast tracepoints normally need to
15064 be placed at an instruction that is 5 bytes or longer, but can be
15065 placed at 4-byte instructions if the low 64K of memory of the target
15066 program is available to install trampolines. Some Unix-type systems,
15067 such as @sc{gnu}/Linux, exclude low addresses from the program's
15068 address space; but for instance with the Linux kernel it is possible
15069 to let @value{GDBN} use this area by doing a @command{sysctl} command
15070 to set the @code{mmap_min_addr} kernel parameter, as in
15073 sudo sysctl -w vm.mmap_min_addr=32768
15077 which sets the low address to 32K, which leaves plenty of room for
15078 trampolines. The minimum address should be set to a page boundary.
15080 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
15081 @cindex set static tracepoint
15082 @cindex static tracepoints, setting
15083 @cindex probe static tracepoint marker
15085 The @code{strace} command sets a static tracepoint. For targets that
15086 support it, setting a static tracepoint probes a static
15087 instrumentation point, or marker, found at the code locations that
15088 result from resolving @var{locspec}. It may not be possible to set a
15089 static tracepoint at the desired code location, in which case the
15090 command will exit with an explanatory message.
15092 @value{GDBN} handles arguments to @code{strace} exactly as for
15093 @code{trace}, with the addition that the user can also specify
15094 @code{-m @var{marker}} instead of a location spec. This probes the marker
15095 identified by the @var{marker} string identifier. This identifier
15096 depends on the static tracepoint backend library your program is
15097 using. You can find all the marker identifiers in the @samp{ID} field
15098 of the @code{info static-tracepoint-markers} command output.
15099 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
15100 Markers}. For example, in the following small program using the UST
15106 trace_mark(ust, bar33, "str %s", "FOOBAZ");
15111 the marker id is composed of joining the first two arguments to the
15112 @code{trace_mark} call with a slash, which translates to:
15115 (@value{GDBP}) info static-tracepoint-markers
15116 Cnt Enb ID Address What
15117 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
15123 so you may probe the marker above with:
15126 (@value{GDBP}) strace -m ust/bar33
15129 Static tracepoints accept an extra collect action --- @code{collect
15130 $_sdata}. This collects arbitrary user data passed in the probe point
15131 call to the tracing library. In the UST example above, you'll see
15132 that the third argument to @code{trace_mark} is a printf-like format
15133 string. The user data is then the result of running that formatting
15134 string against the following arguments. Note that @code{info
15135 static-tracepoint-markers} command output lists that format string in
15136 the @samp{Data:} field.
15138 You can inspect this data when analyzing the trace buffer, by printing
15139 the $_sdata variable like any other variable available to
15140 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
15143 @cindex last tracepoint number
15144 @cindex recent tracepoint number
15145 @cindex tracepoint number
15146 The convenience variable @code{$tpnum} records the tracepoint number
15147 of the most recently set tracepoint.
15149 @kindex delete tracepoint
15150 @cindex tracepoint deletion
15151 @item delete tracepoint @r{[}@var{num}@r{]}
15152 Permanently delete one or more tracepoints. With no argument, the
15153 default is to delete all tracepoints. Note that the regular
15154 @code{delete} command can remove tracepoints also.
15159 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
15161 (@value{GDBP}) @b{delete trace} // remove all tracepoints
15165 You can abbreviate this command as @code{del tr}.
15168 @node Enable and Disable Tracepoints
15169 @subsection Enable and Disable Tracepoints
15171 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
15174 @kindex disable tracepoint
15175 @item disable tracepoint @r{[}@var{num}@r{]}
15176 Disable tracepoint @var{num}, or all tracepoints if no argument
15177 @var{num} is given. A disabled tracepoint will have no effect during
15178 a trace experiment, but it is not forgotten. You can re-enable
15179 a disabled tracepoint using the @code{enable tracepoint} command.
15180 If the command is issued during a trace experiment and the debug target
15181 has support for disabling tracepoints during a trace experiment, then the
15182 change will be effective immediately. Otherwise, it will be applied to the
15183 next trace experiment.
15185 @kindex enable tracepoint
15186 @item enable tracepoint @r{[}@var{num}@r{]}
15187 Enable tracepoint @var{num}, or all tracepoints. If this command is
15188 issued during a trace experiment and the debug target supports enabling
15189 tracepoints during a trace experiment, then the enabled tracepoints will
15190 become effective immediately. Otherwise, they will become effective the
15191 next time a trace experiment is run.
15194 @node Tracepoint Passcounts
15195 @subsection Tracepoint Passcounts
15199 @cindex tracepoint pass count
15200 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
15201 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
15202 automatically stop a trace experiment. If a tracepoint's passcount is
15203 @var{n}, then the trace experiment will be automatically stopped on
15204 the @var{n}'th time that tracepoint is hit. If the tracepoint number
15205 @var{num} is not specified, the @code{passcount} command sets the
15206 passcount of the most recently defined tracepoint. If no passcount is
15207 given, the trace experiment will run until stopped explicitly by the
15213 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
15214 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
15216 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
15217 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
15218 (@value{GDBP}) @b{trace foo}
15219 (@value{GDBP}) @b{pass 3}
15220 (@value{GDBP}) @b{trace bar}
15221 (@value{GDBP}) @b{pass 2}
15222 (@value{GDBP}) @b{trace baz}
15223 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
15224 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
15225 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
15226 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
15230 @node Tracepoint Conditions
15231 @subsection Tracepoint Conditions
15232 @cindex conditional tracepoints
15233 @cindex tracepoint conditions
15235 The simplest sort of tracepoint collects data every time your program
15236 reaches a specified place. You can also specify a @dfn{condition} for
15237 a tracepoint. A condition is just a Boolean expression in your
15238 programming language (@pxref{Expressions, ,Expressions}). A
15239 tracepoint with a condition evaluates the expression each time your
15240 program reaches it, and data collection happens only if the condition
15243 Tracepoint conditions can be specified when a tracepoint is set, by
15244 using @samp{if} in the arguments to the @code{trace} command.
15245 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
15246 also be set or changed at any time with the @code{condition} command,
15247 just as with breakpoints.
15249 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
15250 the conditional expression itself. Instead, @value{GDBN} encodes the
15251 expression into an agent expression (@pxref{Agent Expressions})
15252 suitable for execution on the target, independently of @value{GDBN}.
15253 Global variables become raw memory locations, locals become stack
15254 accesses, and so forth.
15256 For instance, suppose you have a function that is usually called
15257 frequently, but should not be called after an error has occurred. You
15258 could use the following tracepoint command to collect data about calls
15259 of that function that happen while the error code is propagating
15260 through the program; an unconditional tracepoint could end up
15261 collecting thousands of useless trace frames that you would have to
15265 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
15268 @node Trace State Variables
15269 @subsection Trace State Variables
15270 @cindex trace state variables
15272 A @dfn{trace state variable} is a special type of variable that is
15273 created and managed by target-side code. The syntax is the same as
15274 that for GDB's convenience variables (a string prefixed with ``$''),
15275 but they are stored on the target. They must be created explicitly,
15276 using a @code{tvariable} command. They are always 64-bit signed
15279 Trace state variables are remembered by @value{GDBN}, and downloaded
15280 to the target along with tracepoint information when the trace
15281 experiment starts. There are no intrinsic limits on the number of
15282 trace state variables, beyond memory limitations of the target.
15284 @cindex convenience variables, and trace state variables
15285 Although trace state variables are managed by the target, you can use
15286 them in print commands and expressions as if they were convenience
15287 variables; @value{GDBN} will get the current value from the target
15288 while the trace experiment is running. Trace state variables share
15289 the same namespace as other ``$'' variables, which means that you
15290 cannot have trace state variables with names like @code{$23} or
15291 @code{$pc}, nor can you have a trace state variable and a convenience
15292 variable with the same name.
15296 @item tvariable $@var{name} [ = @var{expression} ]
15298 The @code{tvariable} command creates a new trace state variable named
15299 @code{$@var{name}}, and optionally gives it an initial value of
15300 @var{expression}. The @var{expression} is evaluated when this command is
15301 entered; the result will be converted to an integer if possible,
15302 otherwise @value{GDBN} will report an error. A subsequent
15303 @code{tvariable} command specifying the same name does not create a
15304 variable, but instead assigns the supplied initial value to the
15305 existing variable of that name, overwriting any previous initial
15306 value. The default initial value is 0.
15308 @item info tvariables
15309 @kindex info tvariables
15310 List all the trace state variables along with their initial values.
15311 Their current values may also be displayed, if the trace experiment is
15314 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
15315 @kindex delete tvariable
15316 Delete the given trace state variables, or all of them if no arguments
15321 @node Tracepoint Actions
15322 @subsection Tracepoint Action Lists
15326 @cindex tracepoint actions
15327 @item actions @r{[}@var{num}@r{]}
15328 This command will prompt for a list of actions to be taken when the
15329 tracepoint is hit. If the tracepoint number @var{num} is not
15330 specified, this command sets the actions for the one that was most
15331 recently defined (so that you can define a tracepoint and then say
15332 @code{actions} without bothering about its number). You specify the
15333 actions themselves on the following lines, one action at a time, and
15334 terminate the actions list with a line containing just @code{end}. So
15335 far, the only defined actions are @code{collect}, @code{teval}, and
15336 @code{while-stepping}.
15338 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
15339 Commands, ,Breakpoint Command Lists}), except that only the defined
15340 actions are allowed; any other @value{GDBN} command is rejected.
15342 @cindex remove actions from a tracepoint
15343 To remove all actions from a tracepoint, type @samp{actions @var{num}}
15344 and follow it immediately with @samp{end}.
15347 (@value{GDBP}) @b{collect @var{data}} // collect some data
15349 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
15351 (@value{GDBP}) @b{end} // signals the end of actions.
15354 In the following example, the action list begins with @code{collect}
15355 commands indicating the things to be collected when the tracepoint is
15356 hit. Then, in order to single-step and collect additional data
15357 following the tracepoint, a @code{while-stepping} command is used,
15358 followed by the list of things to be collected after each step in a
15359 sequence of single steps. The @code{while-stepping} command is
15360 terminated by its own separate @code{end} command. Lastly, the action
15361 list is terminated by an @code{end} command.
15364 (@value{GDBP}) @b{trace foo}
15365 (@value{GDBP}) @b{actions}
15366 Enter actions for tracepoint 1, one per line:
15369 > while-stepping 12
15370 > collect $pc, arr[i]
15375 @kindex collect @r{(tracepoints)}
15376 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15377 Collect values of the given expressions when the tracepoint is hit.
15378 This command accepts a comma-separated list of any valid expressions.
15379 In addition to global, static, or local variables, the following
15380 special arguments are supported:
15384 Collect all registers.
15387 Collect all function arguments.
15390 Collect all local variables.
15393 Collect the return address. This is helpful if you want to see more
15396 @emph{Note:} The return address location can not always be reliably
15397 determined up front, and the wrong address / registers may end up
15398 collected instead. On some architectures the reliability is higher
15399 for tracepoints at function entry, while on others it's the opposite.
15400 When this happens, backtracing will stop because the return address is
15401 found unavailable (unless another collect rule happened to match it).
15404 Collects the number of arguments from the static probe at which the
15405 tracepoint is located.
15406 @xref{Static Probe Points}.
15408 @item $_probe_arg@var{n}
15409 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15410 from the static probe at which the tracepoint is located.
15411 @xref{Static Probe Points}.
15414 @vindex $_sdata@r{, collect}
15415 Collect static tracepoint marker specific data. Only available for
15416 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15417 Lists}. On the UST static tracepoints library backend, an
15418 instrumentation point resembles a @code{printf} function call. The
15419 tracing library is able to collect user specified data formatted to a
15420 character string using the format provided by the programmer that
15421 instrumented the program. Other backends have similar mechanisms.
15422 Here's an example of a UST marker call:
15425 const char master_name[] = "$your_name";
15426 trace_mark(channel1, marker1, "hello %s", master_name)
15429 In this case, collecting @code{$_sdata} collects the string
15430 @samp{hello $yourname}. When analyzing the trace buffer, you can
15431 inspect @samp{$_sdata} like any other variable available to
15435 You can give several consecutive @code{collect} commands, each one
15436 with a single argument, or one @code{collect} command with several
15437 arguments separated by commas; the effect is the same.
15439 The optional @var{mods} changes the usual handling of the arguments.
15440 @code{s} requests that pointers to chars be handled as strings, in
15441 particular collecting the contents of the memory being pointed at, up
15442 to the first zero. The upper bound is by default the value of the
15443 @code{print characters} variable; if @code{s} is followed by a decimal
15444 number, that is the upper bound instead. So for instance
15445 @samp{collect/s25 mystr} collects as many as 25 characters at
15448 The command @code{info scope} (@pxref{Symbols, info scope}) is
15449 particularly useful for figuring out what data to collect.
15451 @kindex teval @r{(tracepoints)}
15452 @item teval @var{expr1}, @var{expr2}, @dots{}
15453 Evaluate the given expressions when the tracepoint is hit. This
15454 command accepts a comma-separated list of expressions. The results
15455 are discarded, so this is mainly useful for assigning values to trace
15456 state variables (@pxref{Trace State Variables}) without adding those
15457 values to the trace buffer, as would be the case if the @code{collect}
15460 @kindex while-stepping @r{(tracepoints)}
15461 @item while-stepping @var{n}
15462 Perform @var{n} single-step instruction traces after the tracepoint,
15463 collecting new data after each step. The @code{while-stepping}
15464 command is followed by the list of what to collect while stepping
15465 (followed by its own @code{end} command):
15468 > while-stepping 12
15469 > collect $regs, myglobal
15475 Note that @code{$pc} is not automatically collected by
15476 @code{while-stepping}; you need to explicitly collect that register if
15477 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15480 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15481 @kindex set default-collect
15482 @cindex default collection action
15483 This variable is a list of expressions to collect at each tracepoint
15484 hit. It is effectively an additional @code{collect} action prepended
15485 to every tracepoint action list. The expressions are parsed
15486 individually for each tracepoint, so for instance a variable named
15487 @code{xyz} may be interpreted as a global for one tracepoint, and a
15488 local for another, as appropriate to the tracepoint's location.
15490 @item show default-collect
15491 @kindex show default-collect
15492 Show the list of expressions that are collected by default at each
15497 @node Listing Tracepoints
15498 @subsection Listing Tracepoints
15501 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15502 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15503 @cindex information about tracepoints
15504 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15505 Display information about the tracepoint @var{num}. If you don't
15506 specify a tracepoint number, displays information about all the
15507 tracepoints defined so far. The format is similar to that used for
15508 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15509 command, simply restricting itself to tracepoints.
15511 A tracepoint's listing may include additional information specific to
15516 its passcount as given by the @code{passcount @var{n}} command
15519 the state about installed on target of each location
15523 (@value{GDBP}) @b{info trace}
15524 Num Type Disp Enb Address What
15525 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15527 collect globfoo, $regs
15532 2 tracepoint keep y <MULTIPLE>
15534 2.1 y 0x0804859c in func4 at change-loc.h:35
15535 installed on target
15536 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15537 installed on target
15538 2.3 y <PENDING> set_tracepoint
15539 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15540 not installed on target
15545 This command can be abbreviated @code{info tp}.
15548 @node Listing Static Tracepoint Markers
15549 @subsection Listing Static Tracepoint Markers
15552 @kindex info static-tracepoint-markers
15553 @cindex information about static tracepoint markers
15554 @item info static-tracepoint-markers
15555 Display information about all static tracepoint markers defined in the
15558 For each marker, the following columns are printed:
15562 An incrementing counter, output to help readability. This is not a
15565 The marker ID, as reported by the target.
15566 @item Enabled or Disabled
15567 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15568 that are not enabled.
15570 Where the marker is in your program, as a memory address.
15572 Where the marker is in the source for your program, as a file and line
15573 number. If the debug information included in the program does not
15574 allow @value{GDBN} to locate the source of the marker, this column
15575 will be left blank.
15579 In addition, the following information may be printed for each marker:
15583 User data passed to the tracing library by the marker call. In the
15584 UST backend, this is the format string passed as argument to the
15586 @item Static tracepoints probing the marker
15587 The list of static tracepoints attached to the marker.
15591 (@value{GDBP}) info static-tracepoint-markers
15592 Cnt ID Enb Address What
15593 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15594 Data: number1 %d number2 %d
15595 Probed by static tracepoints: #2
15596 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15602 @node Starting and Stopping Trace Experiments
15603 @subsection Starting and Stopping Trace Experiments
15606 @kindex tstart [ @var{notes} ]
15607 @cindex start a new trace experiment
15608 @cindex collected data discarded
15610 This command starts the trace experiment, and begins collecting data.
15611 It has the side effect of discarding all the data collected in the
15612 trace buffer during the previous trace experiment. If any arguments
15613 are supplied, they are taken as a note and stored with the trace
15614 experiment's state. The notes may be arbitrary text, and are
15615 especially useful with disconnected tracing in a multi-user context;
15616 the notes can explain what the trace is doing, supply user contact
15617 information, and so forth.
15619 @kindex tstop [ @var{notes} ]
15620 @cindex stop a running trace experiment
15622 This command stops the trace experiment. If any arguments are
15623 supplied, they are recorded with the experiment as a note. This is
15624 useful if you are stopping a trace started by someone else, for
15625 instance if the trace is interfering with the system's behavior and
15626 needs to be stopped quickly.
15628 @strong{Note}: a trace experiment and data collection may stop
15629 automatically if any tracepoint's passcount is reached
15630 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15633 @cindex status of trace data collection
15634 @cindex trace experiment, status of
15636 This command displays the status of the current trace data
15640 Here is an example of the commands we described so far:
15643 (@value{GDBP}) @b{trace gdb_c_test}
15644 (@value{GDBP}) @b{actions}
15645 Enter actions for tracepoint #1, one per line.
15646 > collect $regs,$locals,$args
15647 > while-stepping 11
15651 (@value{GDBP}) @b{tstart}
15652 [time passes @dots{}]
15653 (@value{GDBP}) @b{tstop}
15656 @anchor{disconnected tracing}
15657 @cindex disconnected tracing
15658 You can choose to continue running the trace experiment even if
15659 @value{GDBN} disconnects from the target, voluntarily or
15660 involuntarily. For commands such as @code{detach}, the debugger will
15661 ask what you want to do with the trace. But for unexpected
15662 terminations (@value{GDBN} crash, network outage), it would be
15663 unfortunate to lose hard-won trace data, so the variable
15664 @code{disconnected-tracing} lets you decide whether the trace should
15665 continue running without @value{GDBN}.
15668 @item set disconnected-tracing on
15669 @itemx set disconnected-tracing off
15670 @kindex set disconnected-tracing
15671 Choose whether a tracing run should continue to run if @value{GDBN}
15672 has disconnected from the target. Note that @code{detach} or
15673 @code{quit} will ask you directly what to do about a running trace no
15674 matter what this variable's setting, so the variable is mainly useful
15675 for handling unexpected situations, such as loss of the network.
15677 @item show disconnected-tracing
15678 @kindex show disconnected-tracing
15679 Show the current choice for disconnected tracing.
15683 When you reconnect to the target, the trace experiment may or may not
15684 still be running; it might have filled the trace buffer in the
15685 meantime, or stopped for one of the other reasons. If it is running,
15686 it will continue after reconnection.
15688 Upon reconnection, the target will upload information about the
15689 tracepoints in effect. @value{GDBN} will then compare that
15690 information to the set of tracepoints currently defined, and attempt
15691 to match them up, allowing for the possibility that the numbers may
15692 have changed due to creation and deletion in the meantime. If one of
15693 the target's tracepoints does not match any in @value{GDBN}, the
15694 debugger will create a new tracepoint, so that you have a number with
15695 which to specify that tracepoint. This matching-up process is
15696 necessarily heuristic, and it may result in useless tracepoints being
15697 created; you may simply delete them if they are of no use.
15699 @cindex circular trace buffer
15700 If your target agent supports a @dfn{circular trace buffer}, then you
15701 can run a trace experiment indefinitely without filling the trace
15702 buffer; when space runs out, the agent deletes already-collected trace
15703 frames, oldest first, until there is enough room to continue
15704 collecting. This is especially useful if your tracepoints are being
15705 hit too often, and your trace gets terminated prematurely because the
15706 buffer is full. To ask for a circular trace buffer, simply set
15707 @samp{circular-trace-buffer} to on. You can set this at any time,
15708 including during tracing; if the agent can do it, it will change
15709 buffer handling on the fly, otherwise it will not take effect until
15713 @item set circular-trace-buffer on
15714 @itemx set circular-trace-buffer off
15715 @kindex set circular-trace-buffer
15716 Choose whether a tracing run should use a linear or circular buffer
15717 for trace data. A linear buffer will not lose any trace data, but may
15718 fill up prematurely, while a circular buffer will discard old trace
15719 data, but it will have always room for the latest tracepoint hits.
15721 @item show circular-trace-buffer
15722 @kindex show circular-trace-buffer
15723 Show the current choice for the trace buffer. Note that this may not
15724 match the agent's current buffer handling, nor is it guaranteed to
15725 match the setting that might have been in effect during a past run,
15726 for instance if you are looking at frames from a trace file.
15731 @item set trace-buffer-size @var{n}
15732 @itemx set trace-buffer-size unlimited
15733 @kindex set trace-buffer-size
15734 Request that the target use a trace buffer of @var{n} bytes. Not all
15735 targets will honor the request; they may have a compiled-in size for
15736 the trace buffer, or some other limitation. Set to a value of
15737 @code{unlimited} or @code{-1} to let the target use whatever size it
15738 likes. This is also the default.
15740 @item show trace-buffer-size
15741 @kindex show trace-buffer-size
15742 Show the current requested size for the trace buffer. Note that this
15743 will only match the actual size if the target supports size-setting,
15744 and was able to handle the requested size. For instance, if the
15745 target can only change buffer size between runs, this variable will
15746 not reflect the change until the next run starts. Use @code{tstatus}
15747 to get a report of the actual buffer size.
15751 @item set trace-user @var{text}
15752 @kindex set trace-user
15754 @item show trace-user
15755 @kindex show trace-user
15757 @item set trace-notes @var{text}
15758 @kindex set trace-notes
15759 Set the trace run's notes.
15761 @item show trace-notes
15762 @kindex show trace-notes
15763 Show the trace run's notes.
15765 @item set trace-stop-notes @var{text}
15766 @kindex set trace-stop-notes
15767 Set the trace run's stop notes. The handling of the note is as for
15768 @code{tstop} arguments; the set command is convenient way to fix a
15769 stop note that is mistaken or incomplete.
15771 @item show trace-stop-notes
15772 @kindex show trace-stop-notes
15773 Show the trace run's stop notes.
15777 @node Tracepoint Restrictions
15778 @subsection Tracepoint Restrictions
15780 @cindex tracepoint restrictions
15781 There are a number of restrictions on the use of tracepoints. As
15782 described above, tracepoint data gathering occurs on the target
15783 without interaction from @value{GDBN}. Thus the full capabilities of
15784 the debugger are not available during data gathering, and then at data
15785 examination time, you will be limited by only having what was
15786 collected. The following items describe some common problems, but it
15787 is not exhaustive, and you may run into additional difficulties not
15793 Tracepoint expressions are intended to gather objects (lvalues). Thus
15794 the full flexibility of GDB's expression evaluator is not available.
15795 You cannot call functions, cast objects to aggregate types, access
15796 convenience variables or modify values (except by assignment to trace
15797 state variables). Some language features may implicitly call
15798 functions (for instance Objective-C fields with accessors), and therefore
15799 cannot be collected either.
15802 Collection of local variables, either individually or in bulk with
15803 @code{$locals} or @code{$args}, during @code{while-stepping} may
15804 behave erratically. The stepping action may enter a new scope (for
15805 instance by stepping into a function), or the location of the variable
15806 may change (for instance it is loaded into a register). The
15807 tracepoint data recorded uses the location information for the
15808 variables that is correct for the tracepoint location. When the
15809 tracepoint is created, it is not possible, in general, to determine
15810 where the steps of a @code{while-stepping} sequence will advance the
15811 program---particularly if a conditional branch is stepped.
15814 Collection of an incompletely-initialized or partially-destroyed object
15815 may result in something that @value{GDBN} cannot display, or displays
15816 in a misleading way.
15819 When @value{GDBN} displays a pointer to character it automatically
15820 dereferences the pointer to also display characters of the string
15821 being pointed to. However, collecting the pointer during tracing does
15822 not automatically collect the string. You need to explicitly
15823 dereference the pointer and provide size information if you want to
15824 collect not only the pointer, but the memory pointed to. For example,
15825 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15829 It is not possible to collect a complete stack backtrace at a
15830 tracepoint. Instead, you may collect the registers and a few hundred
15831 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15832 (adjust to use the name of the actual stack pointer register on your
15833 target architecture, and the amount of stack you wish to capture).
15834 Then the @code{backtrace} command will show a partial backtrace when
15835 using a trace frame. The number of stack frames that can be examined
15836 depends on the sizes of the frames in the collected stack. Note that
15837 if you ask for a block so large that it goes past the bottom of the
15838 stack, the target agent may report an error trying to read from an
15842 If you do not collect registers at a tracepoint, @value{GDBN} can
15843 infer that the value of @code{$pc} must be the same as the address of
15844 the tracepoint and use that when you are looking at a trace frame
15845 for that tracepoint. However, this cannot work if the tracepoint has
15846 multiple locations (for instance if it was set in a function that was
15847 inlined), or if it has a @code{while-stepping} loop. In those cases
15848 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15853 @node Analyze Collected Data
15854 @section Using the Collected Data
15856 After the tracepoint experiment ends, you use @value{GDBN} commands
15857 for examining the trace data. The basic idea is that each tracepoint
15858 collects a trace @dfn{snapshot} every time it is hit and another
15859 snapshot every time it single-steps. All these snapshots are
15860 consecutively numbered from zero and go into a buffer, and you can
15861 examine them later. The way you examine them is to @dfn{focus} on a
15862 specific trace snapshot. When the remote stub is focused on a trace
15863 snapshot, it will respond to all @value{GDBN} requests for memory and
15864 registers by reading from the buffer which belongs to that snapshot,
15865 rather than from @emph{real} memory or registers of the program being
15866 debugged. This means that @strong{all} @value{GDBN} commands
15867 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15868 behave as if we were currently debugging the program state as it was
15869 when the tracepoint occurred. Any requests for data that are not in
15870 the buffer will fail.
15873 * tfind:: How to select a trace snapshot
15874 * tdump:: How to display all data for a snapshot
15875 * save tracepoints:: How to save tracepoints for a future run
15879 @subsection @code{tfind @var{n}}
15882 @cindex select trace snapshot
15883 @cindex find trace snapshot
15884 The basic command for selecting a trace snapshot from the buffer is
15885 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15886 counting from zero. If no argument @var{n} is given, the next
15887 snapshot is selected.
15889 Here are the various forms of using the @code{tfind} command.
15893 Find the first snapshot in the buffer. This is a synonym for
15894 @code{tfind 0} (since 0 is the number of the first snapshot).
15897 Stop debugging trace snapshots, resume @emph{live} debugging.
15900 Same as @samp{tfind none}.
15903 No argument means find the next trace snapshot or find the first
15904 one if no trace snapshot is selected.
15907 Find the previous trace snapshot before the current one. This permits
15908 retracing earlier steps.
15910 @item tfind tracepoint @var{num}
15911 Find the next snapshot associated with tracepoint @var{num}. Search
15912 proceeds forward from the last examined trace snapshot. If no
15913 argument @var{num} is given, it means find the next snapshot collected
15914 for the same tracepoint as the current snapshot.
15916 @item tfind pc @var{addr}
15917 Find the next snapshot associated with the value @var{addr} of the
15918 program counter. Search proceeds forward from the last examined trace
15919 snapshot. If no argument @var{addr} is given, it means find the next
15920 snapshot with the same value of PC as the current snapshot.
15922 @item tfind outside @var{addr1}, @var{addr2}
15923 Find the next snapshot whose PC is outside the given range of
15924 addresses (exclusive).
15926 @item tfind range @var{addr1}, @var{addr2}
15927 Find the next snapshot whose PC is between @var{addr1} and
15928 @var{addr2} (inclusive).
15930 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15931 Find the next snapshot associated with the source line @var{n}. If
15932 the optional argument @var{file} is given, refer to line @var{n} in
15933 that source file. Search proceeds forward from the last examined
15934 trace snapshot. If no argument @var{n} is given, it means find the
15935 next line other than the one currently being examined; thus saying
15936 @code{tfind line} repeatedly can appear to have the same effect as
15937 stepping from line to line in a @emph{live} debugging session.
15940 The default arguments for the @code{tfind} commands are specifically
15941 designed to make it easy to scan through the trace buffer. For
15942 instance, @code{tfind} with no argument selects the next trace
15943 snapshot, and @code{tfind -} with no argument selects the previous
15944 trace snapshot. So, by giving one @code{tfind} command, and then
15945 simply hitting @key{RET} repeatedly you can examine all the trace
15946 snapshots in order. Or, by saying @code{tfind -} and then hitting
15947 @key{RET} repeatedly you can examine the snapshots in reverse order.
15948 The @code{tfind line} command with no argument selects the snapshot
15949 for the next source line executed. The @code{tfind pc} command with
15950 no argument selects the next snapshot with the same program counter
15951 (PC) as the current frame. The @code{tfind tracepoint} command with
15952 no argument selects the next trace snapshot collected by the same
15953 tracepoint as the current one.
15955 In addition to letting you scan through the trace buffer manually,
15956 these commands make it easy to construct @value{GDBN} scripts that
15957 scan through the trace buffer and print out whatever collected data
15958 you are interested in. Thus, if we want to examine the PC, FP, and SP
15959 registers from each trace frame in the buffer, we can say this:
15962 (@value{GDBP}) @b{tfind start}
15963 (@value{GDBP}) @b{while ($trace_frame != -1)}
15964 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15965 $trace_frame, $pc, $sp, $fp
15969 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15970 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15971 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15972 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15973 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15974 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15975 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15976 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15977 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15978 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15979 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15982 Or, if we want to examine the variable @code{X} at each source line in
15986 (@value{GDBP}) @b{tfind start}
15987 (@value{GDBP}) @b{while ($trace_frame != -1)}
15988 > printf "Frame %d, X == %d\n", $trace_frame, X
15998 @subsection @code{tdump}
16000 @cindex dump all data collected at tracepoint
16001 @cindex tracepoint data, display
16003 This command takes no arguments. It prints all the data collected at
16004 the current trace snapshot.
16007 (@value{GDBP}) @b{trace 444}
16008 (@value{GDBP}) @b{actions}
16009 Enter actions for tracepoint #2, one per line:
16010 > collect $regs, $locals, $args, gdb_long_test
16013 (@value{GDBP}) @b{tstart}
16015 (@value{GDBP}) @b{tfind line 444}
16016 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
16018 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
16020 (@value{GDBP}) @b{tdump}
16021 Data collected at tracepoint 2, trace frame 1:
16022 d0 0xc4aa0085 -995491707
16026 d4 0x71aea3d 119204413
16029 d7 0x380035 3670069
16030 a0 0x19e24a 1696330
16031 a1 0x3000668 50333288
16033 a3 0x322000 3284992
16034 a4 0x3000698 50333336
16035 a5 0x1ad3cc 1758156
16036 fp 0x30bf3c 0x30bf3c
16037 sp 0x30bf34 0x30bf34
16039 pc 0x20b2c8 0x20b2c8
16043 p = 0x20e5b4 "gdb-test"
16050 gdb_long_test = 17 '\021'
16055 @code{tdump} works by scanning the tracepoint's current collection
16056 actions and printing the value of each expression listed. So
16057 @code{tdump} can fail, if after a run, you change the tracepoint's
16058 actions to mention variables that were not collected during the run.
16060 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
16061 uses the collected value of @code{$pc} to distinguish between trace
16062 frames that were collected at the tracepoint hit, and frames that were
16063 collected while stepping. This allows it to correctly choose whether
16064 to display the basic list of collections, or the collections from the
16065 body of the while-stepping loop. However, if @code{$pc} was not collected,
16066 then @code{tdump} will always attempt to dump using the basic collection
16067 list, and may fail if a while-stepping frame does not include all the
16068 same data that is collected at the tracepoint hit.
16069 @c This is getting pretty arcane, example would be good.
16071 @node save tracepoints
16072 @subsection @code{save tracepoints @var{filename}}
16073 @kindex save tracepoints
16074 @kindex save-tracepoints
16075 @cindex save tracepoints for future sessions
16077 This command saves all current tracepoint definitions together with
16078 their actions and passcounts, into a file @file{@var{filename}}
16079 suitable for use in a later debugging session. To read the saved
16080 tracepoint definitions, use the @code{source} command (@pxref{Command
16081 Files}). The @w{@code{save-tracepoints}} command is a deprecated
16082 alias for @w{@code{save tracepoints}}
16084 @node Tracepoint Variables
16085 @section Convenience Variables for Tracepoints
16086 @cindex tracepoint variables
16087 @cindex convenience variables for tracepoints
16090 @vindex $trace_frame
16091 @item (int) $trace_frame
16092 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
16093 snapshot is selected.
16095 @vindex $tracepoint
16096 @item (int) $tracepoint
16097 The tracepoint for the current trace snapshot.
16099 @vindex $trace_line
16100 @item (int) $trace_line
16101 The line number for the current trace snapshot.
16103 @vindex $trace_file
16104 @item (char []) $trace_file
16105 The source file for the current trace snapshot.
16107 @vindex $trace_func
16108 @item (char []) $trace_func
16109 The name of the function containing @code{$tracepoint}.
16112 Note: @code{$trace_file} is not suitable for use in @code{printf},
16113 use @code{output} instead.
16115 Here's a simple example of using these convenience variables for
16116 stepping through all the trace snapshots and printing some of their
16117 data. Note that these are not the same as trace state variables,
16118 which are managed by the target.
16121 (@value{GDBP}) @b{tfind start}
16123 (@value{GDBP}) @b{while $trace_frame != -1}
16124 > output $trace_file
16125 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
16131 @section Using Trace Files
16132 @cindex trace files
16134 In some situations, the target running a trace experiment may no
16135 longer be available; perhaps it crashed, or the hardware was needed
16136 for a different activity. To handle these cases, you can arrange to
16137 dump the trace data into a file, and later use that file as a source
16138 of trace data, via the @code{target tfile} command.
16143 @item tsave [ -r ] @var{filename}
16144 @itemx tsave [-ctf] @var{dirname}
16145 Save the trace data to @var{filename}. By default, this command
16146 assumes that @var{filename} refers to the host filesystem, so if
16147 necessary @value{GDBN} will copy raw trace data up from the target and
16148 then save it. If the target supports it, you can also supply the
16149 optional argument @code{-r} (``remote'') to direct the target to save
16150 the data directly into @var{filename} in its own filesystem, which may be
16151 more efficient if the trace buffer is very large. (Note, however, that
16152 @code{target tfile} can only read from files accessible to the host.)
16153 By default, this command will save trace frame in tfile format.
16154 You can supply the optional argument @code{-ctf} to save data in CTF
16155 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
16156 that can be shared by multiple debugging and tracing tools. Please go to
16157 @indicateurl{http://www.efficios.com/ctf} to get more information.
16159 @kindex target tfile
16163 @item target tfile @var{filename}
16164 @itemx target ctf @var{dirname}
16165 Use the file named @var{filename} or directory named @var{dirname} as
16166 a source of trace data. Commands that examine data work as they do with
16167 a live target, but it is not possible to run any new trace experiments.
16168 @code{tstatus} will report the state of the trace run at the moment
16169 the data was saved, as well as the current trace frame you are examining.
16170 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
16174 (@value{GDBP}) target ctf ctf.ctf
16175 (@value{GDBP}) tfind
16176 Found trace frame 0, tracepoint 2
16177 39 ++a; /* set tracepoint 1 here */
16178 (@value{GDBP}) tdump
16179 Data collected at tracepoint 2, trace frame 0:
16183 c = @{"123", "456", "789", "123", "456", "789"@}
16184 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
16192 @chapter Debugging Programs That Use Overlays
16195 If your program is too large to fit completely in your target system's
16196 memory, you can sometimes use @dfn{overlays} to work around this
16197 problem. @value{GDBN} provides some support for debugging programs that
16201 * How Overlays Work:: A general explanation of overlays.
16202 * Overlay Commands:: Managing overlays in @value{GDBN}.
16203 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
16204 mapped by asking the inferior.
16205 * Overlay Sample Program:: A sample program using overlays.
16208 @node How Overlays Work
16209 @section How Overlays Work
16210 @cindex mapped overlays
16211 @cindex unmapped overlays
16212 @cindex load address, overlay's
16213 @cindex mapped address
16214 @cindex overlay area
16216 Suppose you have a computer whose instruction address space is only 64
16217 kilobytes long, but which has much more memory which can be accessed by
16218 other means: special instructions, segment registers, or memory
16219 management hardware, for example. Suppose further that you want to
16220 adapt a program which is larger than 64 kilobytes to run on this system.
16222 One solution is to identify modules of your program which are relatively
16223 independent, and need not call each other directly; call these modules
16224 @dfn{overlays}. Separate the overlays from the main program, and place
16225 their machine code in the larger memory. Place your main program in
16226 instruction memory, but leave at least enough space there to hold the
16227 largest overlay as well.
16229 Now, to call a function located in an overlay, you must first copy that
16230 overlay's machine code from the large memory into the space set aside
16231 for it in the instruction memory, and then jump to its entry point
16234 @c NB: In the below the mapped area's size is greater or equal to the
16235 @c size of all overlays. This is intentional to remind the developer
16236 @c that overlays don't necessarily need to be the same size.
16240 Data Instruction Larger
16241 Address Space Address Space Address Space
16242 +-----------+ +-----------+ +-----------+
16244 +-----------+ +-----------+ +-----------+<-- overlay 1
16245 | program | | main | .----| overlay 1 | load address
16246 | variables | | program | | +-----------+
16247 | and heap | | | | | |
16248 +-----------+ | | | +-----------+<-- overlay 2
16249 | | +-----------+ | | | load address
16250 +-----------+ | | | .-| overlay 2 |
16252 mapped --->+-----------+ | | +-----------+
16253 address | | | | | |
16254 | overlay | <-' | | |
16255 | area | <---' +-----------+<-- overlay 3
16256 | | <---. | | load address
16257 +-----------+ `--| overlay 3 |
16264 @anchor{A code overlay}A code overlay
16268 The diagram (@pxref{A code overlay}) shows a system with separate data
16269 and instruction address spaces. To map an overlay, the program copies
16270 its code from the larger address space to the instruction address space.
16271 Since the overlays shown here all use the same mapped address, only one
16272 may be mapped at a time. For a system with a single address space for
16273 data and instructions, the diagram would be similar, except that the
16274 program variables and heap would share an address space with the main
16275 program and the overlay area.
16277 An overlay loaded into instruction memory and ready for use is called a
16278 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
16279 instruction memory. An overlay not present (or only partially present)
16280 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
16281 is its address in the larger memory. The mapped address is also called
16282 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
16283 called the @dfn{load memory address}, or @dfn{LMA}.
16285 Unfortunately, overlays are not a completely transparent way to adapt a
16286 program to limited instruction memory. They introduce a new set of
16287 global constraints you must keep in mind as you design your program:
16292 Before calling or returning to a function in an overlay, your program
16293 must make sure that overlay is actually mapped. Otherwise, the call or
16294 return will transfer control to the right address, but in the wrong
16295 overlay, and your program will probably crash.
16298 If the process of mapping an overlay is expensive on your system, you
16299 will need to choose your overlays carefully to minimize their effect on
16300 your program's performance.
16303 The executable file you load onto your system must contain each
16304 overlay's instructions, appearing at the overlay's load address, not its
16305 mapped address. However, each overlay's instructions must be relocated
16306 and its symbols defined as if the overlay were at its mapped address.
16307 You can use GNU linker scripts to specify different load and relocation
16308 addresses for pieces of your program; see @ref{Overlay Description,,,
16309 ld.info, Using ld: the GNU linker}.
16312 The procedure for loading executable files onto your system must be able
16313 to load their contents into the larger address space as well as the
16314 instruction and data spaces.
16318 The overlay system described above is rather simple, and could be
16319 improved in many ways:
16324 If your system has suitable bank switch registers or memory management
16325 hardware, you could use those facilities to make an overlay's load area
16326 contents simply appear at their mapped address in instruction space.
16327 This would probably be faster than copying the overlay to its mapped
16328 area in the usual way.
16331 If your overlays are small enough, you could set aside more than one
16332 overlay area, and have more than one overlay mapped at a time.
16335 You can use overlays to manage data, as well as instructions. In
16336 general, data overlays are even less transparent to your design than
16337 code overlays: whereas code overlays only require care when you call or
16338 return to functions, data overlays require care every time you access
16339 the data. Also, if you change the contents of a data overlay, you
16340 must copy its contents back out to its load address before you can copy a
16341 different data overlay into the same mapped area.
16346 @node Overlay Commands
16347 @section Overlay Commands
16349 To use @value{GDBN}'s overlay support, each overlay in your program must
16350 correspond to a separate section of the executable file. The section's
16351 virtual memory address and load memory address must be the overlay's
16352 mapped and load addresses. Identifying overlays with sections allows
16353 @value{GDBN} to determine the appropriate address of a function or
16354 variable, depending on whether the overlay is mapped or not.
16356 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16357 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16362 Disable @value{GDBN}'s overlay support. When overlay support is
16363 disabled, @value{GDBN} assumes that all functions and variables are
16364 always present at their mapped addresses. By default, @value{GDBN}'s
16365 overlay support is disabled.
16367 @item overlay manual
16368 @cindex manual overlay debugging
16369 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16370 relies on you to tell it which overlays are mapped, and which are not,
16371 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16372 commands described below.
16374 @item overlay map-overlay @var{overlay}
16375 @itemx overlay map @var{overlay}
16376 @cindex map an overlay
16377 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16378 be the name of the object file section containing the overlay. When an
16379 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16380 functions and variables at their mapped addresses. @value{GDBN} assumes
16381 that any other overlays whose mapped ranges overlap that of
16382 @var{overlay} are now unmapped.
16384 @item overlay unmap-overlay @var{overlay}
16385 @itemx overlay unmap @var{overlay}
16386 @cindex unmap an overlay
16387 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16388 must be the name of the object file section containing the overlay.
16389 When an overlay is unmapped, @value{GDBN} assumes it can find the
16390 overlay's functions and variables at their load addresses.
16393 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16394 consults a data structure the overlay manager maintains in the inferior
16395 to see which overlays are mapped. For details, see @ref{Automatic
16396 Overlay Debugging}.
16398 @item overlay load-target
16399 @itemx overlay load
16400 @cindex reloading the overlay table
16401 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16402 re-reads the table @value{GDBN} automatically each time the inferior
16403 stops, so this command should only be necessary if you have changed the
16404 overlay mapping yourself using @value{GDBN}. This command is only
16405 useful when using automatic overlay debugging.
16407 @item overlay list-overlays
16408 @itemx overlay list
16409 @cindex listing mapped overlays
16410 Display a list of the overlays currently mapped, along with their mapped
16411 addresses, load addresses, and sizes.
16415 Normally, when @value{GDBN} prints a code address, it includes the name
16416 of the function the address falls in:
16419 (@value{GDBP}) print main
16420 $3 = @{int ()@} 0x11a0 <main>
16423 When overlay debugging is enabled, @value{GDBN} recognizes code in
16424 unmapped overlays, and prints the names of unmapped functions with
16425 asterisks around them. For example, if @code{foo} is a function in an
16426 unmapped overlay, @value{GDBN} prints it this way:
16429 (@value{GDBP}) overlay list
16430 No sections are mapped.
16431 (@value{GDBP}) print foo
16432 $5 = @{int (int)@} 0x100000 <*foo*>
16435 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16439 (@value{GDBP}) overlay list
16440 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16441 mapped at 0x1016 - 0x104a
16442 (@value{GDBP}) print foo
16443 $6 = @{int (int)@} 0x1016 <foo>
16446 When overlay debugging is enabled, @value{GDBN} can find the correct
16447 address for functions and variables in an overlay, whether or not the
16448 overlay is mapped. This allows most @value{GDBN} commands, like
16449 @code{break} and @code{disassemble}, to work normally, even on unmapped
16450 code. However, @value{GDBN}'s breakpoint support has some limitations:
16454 @cindex breakpoints in overlays
16455 @cindex overlays, setting breakpoints in
16456 You can set breakpoints in functions in unmapped overlays, as long as
16457 @value{GDBN} can write to the overlay at its load address.
16459 @value{GDBN} can not set hardware or simulator-based breakpoints in
16460 unmapped overlays. However, if you set a breakpoint at the end of your
16461 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16462 you are using manual overlay management), @value{GDBN} will re-set its
16463 breakpoints properly.
16467 @node Automatic Overlay Debugging
16468 @section Automatic Overlay Debugging
16469 @cindex automatic overlay debugging
16471 @value{GDBN} can automatically track which overlays are mapped and which
16472 are not, given some simple co-operation from the overlay manager in the
16473 inferior. If you enable automatic overlay debugging with the
16474 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16475 looks in the inferior's memory for certain variables describing the
16476 current state of the overlays.
16478 Here are the variables your overlay manager must define to support
16479 @value{GDBN}'s automatic overlay debugging:
16483 @item @code{_ovly_table}:
16484 This variable must be an array of the following structures:
16489 /* The overlay's mapped address. */
16492 /* The size of the overlay, in bytes. */
16493 unsigned long size;
16495 /* The overlay's load address. */
16498 /* Non-zero if the overlay is currently mapped;
16500 unsigned long mapped;
16504 @item @code{_novlys}:
16505 This variable must be a four-byte signed integer, holding the total
16506 number of elements in @code{_ovly_table}.
16510 To decide whether a particular overlay is mapped or not, @value{GDBN}
16511 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16512 @code{lma} members equal the VMA and LMA of the overlay's section in the
16513 executable file. When @value{GDBN} finds a matching entry, it consults
16514 the entry's @code{mapped} member to determine whether the overlay is
16517 In addition, your overlay manager may define a function called
16518 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16519 will silently set a breakpoint there. If the overlay manager then
16520 calls this function whenever it has changed the overlay table, this
16521 will enable @value{GDBN} to accurately keep track of which overlays
16522 are in program memory, and update any breakpoints that may be set
16523 in overlays. This will allow breakpoints to work even if the
16524 overlays are kept in ROM or other non-writable memory while they
16525 are not being executed.
16527 @node Overlay Sample Program
16528 @section Overlay Sample Program
16529 @cindex overlay example program
16531 When linking a program which uses overlays, you must place the overlays
16532 at their load addresses, while relocating them to run at their mapped
16533 addresses. To do this, you must write a linker script (@pxref{Overlay
16534 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16535 since linker scripts are specific to a particular host system, target
16536 architecture, and target memory layout, this manual cannot provide
16537 portable sample code demonstrating @value{GDBN}'s overlay support.
16539 However, the @value{GDBN} source distribution does contain an overlaid
16540 program, with linker scripts for a few systems, as part of its test
16541 suite. The program consists of the following files from
16542 @file{gdb/testsuite/gdb.base}:
16546 The main program file.
16548 A simple overlay manager, used by @file{overlays.c}.
16553 Overlay modules, loaded and used by @file{overlays.c}.
16556 Linker scripts for linking the test program on the @code{d10v-elf}
16557 and @code{m32r-elf} targets.
16560 You can build the test program using the @code{d10v-elf} GCC
16561 cross-compiler like this:
16564 $ d10v-elf-gcc -g -c overlays.c
16565 $ d10v-elf-gcc -g -c ovlymgr.c
16566 $ d10v-elf-gcc -g -c foo.c
16567 $ d10v-elf-gcc -g -c bar.c
16568 $ d10v-elf-gcc -g -c baz.c
16569 $ d10v-elf-gcc -g -c grbx.c
16570 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16571 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16574 The build process is identical for any other architecture, except that
16575 you must substitute the appropriate compiler and linker script for the
16576 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16580 @chapter Using @value{GDBN} with Different Languages
16583 Although programming languages generally have common aspects, they are
16584 rarely expressed in the same manner. For instance, in ANSI C,
16585 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16586 Modula-2, it is accomplished by @code{p^}. Values can also be
16587 represented (and displayed) differently. Hex numbers in C appear as
16588 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16590 @cindex working language
16591 Language-specific information is built into @value{GDBN} for some languages,
16592 allowing you to express operations like the above in your program's
16593 native language, and allowing @value{GDBN} to output values in a manner
16594 consistent with the syntax of your program's native language. The
16595 language you use to build expressions is called the @dfn{working
16599 * Setting:: Switching between source languages
16600 * Show:: Displaying the language
16601 * Checks:: Type and range checks
16602 * Supported Languages:: Supported languages
16603 * Unsupported Languages:: Unsupported languages
16607 @section Switching Between Source Languages
16609 There are two ways to control the working language---either have @value{GDBN}
16610 set it automatically, or select it manually yourself. You can use the
16611 @code{set language} command for either purpose. On startup, @value{GDBN}
16612 defaults to setting the language automatically. The working language is
16613 used to determine how expressions you type are interpreted, how values
16616 In addition to the working language, every source file that
16617 @value{GDBN} knows about has its own working language. For some object
16618 file formats, the compiler might indicate which language a particular
16619 source file is in. However, most of the time @value{GDBN} infers the
16620 language from the name of the file. The language of a source file
16621 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16622 show each frame appropriately for its own language. There is no way to
16623 set the language of a source file from within @value{GDBN}, but you can
16624 set the language associated with a filename extension. @xref{Show, ,
16625 Displaying the Language}.
16627 This is most commonly a problem when you use a program, such
16628 as @code{cfront} or @code{f2c}, that generates C but is written in
16629 another language. In that case, make the
16630 program use @code{#line} directives in its C output; that way
16631 @value{GDBN} will know the correct language of the source code of the original
16632 program, and will display that source code, not the generated C code.
16635 * Filenames:: Filename extensions and languages.
16636 * Manually:: Setting the working language manually
16637 * Automatically:: Having @value{GDBN} infer the source language
16641 @subsection List of Filename Extensions and Languages
16643 If a source file name ends in one of the following extensions, then
16644 @value{GDBN} infers that its language is the one indicated.
16662 C@t{++} source file
16668 Objective-C source file
16672 Fortran source file
16675 Modula-2 source file
16679 Assembler source file. This actually behaves almost like C, but
16680 @value{GDBN} does not skip over function prologues when stepping.
16683 In addition, you may set the language associated with a filename
16684 extension. @xref{Show, , Displaying the Language}.
16687 @subsection Setting the Working Language
16689 If you allow @value{GDBN} to set the language automatically,
16690 expressions are interpreted the same way in your debugging session and
16693 @kindex set language
16694 If you wish, you may set the language manually. To do this, issue the
16695 command @samp{set language @var{lang}}, where @var{lang} is the name of
16696 a language, such as
16697 @code{c} or @code{modula-2}.
16698 For a list of the supported languages, type @samp{set language}.
16700 Setting the language manually prevents @value{GDBN} from updating the working
16701 language automatically. This can lead to confusion if you try
16702 to debug a program when the working language is not the same as the
16703 source language, when an expression is acceptable to both
16704 languages---but means different things. For instance, if the current
16705 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16713 might not have the effect you intended. In C, this means to add
16714 @code{b} and @code{c} and place the result in @code{a}. The result
16715 printed would be the value of @code{a}. In Modula-2, this means to compare
16716 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16718 @node Automatically
16719 @subsection Having @value{GDBN} Infer the Source Language
16721 To have @value{GDBN} set the working language automatically, use
16722 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16723 then infers the working language. That is, when your program stops in a
16724 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16725 working language to the language recorded for the function in that
16726 frame. If the language for a frame is unknown (that is, if the function
16727 or block corresponding to the frame was defined in a source file that
16728 does not have a recognized extension), the current working language is
16729 not changed, and @value{GDBN} issues a warning.
16731 This may not seem necessary for most programs, which are written
16732 entirely in one source language. However, program modules and libraries
16733 written in one source language can be used by a main program written in
16734 a different source language. Using @samp{set language auto} in this
16735 case frees you from having to set the working language manually.
16738 @section Displaying the Language
16740 The following commands help you find out which language is the
16741 working language, and also what language source files were written in.
16744 @item show language
16745 @anchor{show language}
16746 @kindex show language
16747 Display the current working language. This is the
16748 language you can use with commands such as @code{print} to
16749 build and compute expressions that may involve variables in your program.
16752 @kindex info frame@r{, show the source language}
16753 Display the source language for this frame. This language becomes the
16754 working language if you use an identifier from this frame.
16755 @xref{Frame Info, ,Information about a Frame}, to identify the other
16756 information listed here.
16759 @kindex info source@r{, show the source language}
16760 Display the source language of this source file.
16761 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16762 information listed here.
16765 In unusual circumstances, you may have source files with extensions
16766 not in the standard list. You can then set the extension associated
16767 with a language explicitly:
16770 @item set extension-language @var{ext} @var{language}
16771 @kindex set extension-language
16772 Tell @value{GDBN} that source files with extension @var{ext} are to be
16773 assumed as written in the source language @var{language}.
16775 @item info extensions
16776 @kindex info extensions
16777 List all the filename extensions and the associated languages.
16781 @section Type and Range Checking
16783 Some languages are designed to guard you against making seemingly common
16784 errors through a series of compile- and run-time checks. These include
16785 checking the type of arguments to functions and operators and making
16786 sure mathematical overflows are caught at run time. Checks such as
16787 these help to ensure a program's correctness once it has been compiled
16788 by eliminating type mismatches and providing active checks for range
16789 errors when your program is running.
16791 By default @value{GDBN} checks for these errors according to the
16792 rules of the current source language. Although @value{GDBN} does not check
16793 the statements in your program, it can check expressions entered directly
16794 into @value{GDBN} for evaluation via the @code{print} command, for example.
16797 * Type Checking:: An overview of type checking
16798 * Range Checking:: An overview of range checking
16801 @cindex type checking
16802 @cindex checks, type
16803 @node Type Checking
16804 @subsection An Overview of Type Checking
16806 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16807 arguments to operators and functions have to be of the correct type,
16808 otherwise an error occurs. These checks prevent type mismatch
16809 errors from ever causing any run-time problems. For example,
16812 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16814 (@value{GDBP}) print obj.my_method (0)
16817 (@value{GDBP}) print obj.my_method (0x1234)
16818 Cannot resolve method klass::my_method to any overloaded instance
16821 The second example fails because in C@t{++} the integer constant
16822 @samp{0x1234} is not type-compatible with the pointer parameter type.
16824 For the expressions you use in @value{GDBN} commands, you can tell
16825 @value{GDBN} to not enforce strict type checking or
16826 to treat any mismatches as errors and abandon the expression;
16827 When type checking is disabled, @value{GDBN} successfully evaluates
16828 expressions like the second example above.
16830 Even if type checking is off, there may be other reasons
16831 related to type that prevent @value{GDBN} from evaluating an expression.
16832 For instance, @value{GDBN} does not know how to add an @code{int} and
16833 a @code{struct foo}. These particular type errors have nothing to do
16834 with the language in use and usually arise from expressions which make
16835 little sense to evaluate anyway.
16837 @value{GDBN} provides some additional commands for controlling type checking:
16839 @kindex set check type
16840 @kindex show check type
16842 @item set check type on
16843 @itemx set check type off
16844 Set strict type checking on or off. If any type mismatches occur in
16845 evaluating an expression while type checking is on, @value{GDBN} prints a
16846 message and aborts evaluation of the expression.
16848 @item show check type
16849 Show the current setting of type checking and whether @value{GDBN}
16850 is enforcing strict type checking rules.
16853 @cindex range checking
16854 @cindex checks, range
16855 @node Range Checking
16856 @subsection An Overview of Range Checking
16858 In some languages (such as Modula-2), it is an error to exceed the
16859 bounds of a type; this is enforced with run-time checks. Such range
16860 checking is meant to ensure program correctness by making sure
16861 computations do not overflow, or indices on an array element access do
16862 not exceed the bounds of the array.
16864 For expressions you use in @value{GDBN} commands, you can tell
16865 @value{GDBN} to treat range errors in one of three ways: ignore them,
16866 always treat them as errors and abandon the expression, or issue
16867 warnings but evaluate the expression anyway.
16869 A range error can result from numerical overflow, from exceeding an
16870 array index bound, or when you type a constant that is not a member
16871 of any type. Some languages, however, do not treat overflows as an
16872 error. In many implementations of C, mathematical overflow causes the
16873 result to ``wrap around'' to lower values---for example, if @var{m} is
16874 the largest integer value, and @var{s} is the smallest, then
16877 @var{m} + 1 @result{} @var{s}
16880 This, too, is specific to individual languages, and in some cases
16881 specific to individual compilers or machines. @xref{Supported Languages, ,
16882 Supported Languages}, for further details on specific languages.
16884 @value{GDBN} provides some additional commands for controlling the range checker:
16886 @kindex set check range
16887 @kindex show check range
16889 @item set check range auto
16890 Set range checking on or off based on the current working language.
16891 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16894 @item set check range on
16895 @itemx set check range off
16896 Set range checking on or off, overriding the default setting for the
16897 current working language. A warning is issued if the setting does not
16898 match the language default. If a range error occurs and range checking is on,
16899 then a message is printed and evaluation of the expression is aborted.
16901 @item set check range warn
16902 Output messages when the @value{GDBN} range checker detects a range error,
16903 but attempt to evaluate the expression anyway. Evaluating the
16904 expression may still be impossible for other reasons, such as accessing
16905 memory that the process does not own (a typical example from many Unix
16908 @item show check range
16909 Show the current setting of the range checker, and whether or not it is
16910 being set automatically by @value{GDBN}.
16913 @node Supported Languages
16914 @section Supported Languages
16916 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16917 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16918 @c This is false ...
16919 Some @value{GDBN} features may be used in expressions regardless of the
16920 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16921 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16922 ,Expressions}) can be used with the constructs of any supported
16925 The following sections detail to what degree each source language is
16926 supported by @value{GDBN}. These sections are not meant to be language
16927 tutorials or references, but serve only as a reference guide to what the
16928 @value{GDBN} expression parser accepts, and what input and output
16929 formats should look like for different languages. There are many good
16930 books written on each of these languages; please look to these for a
16931 language reference or tutorial.
16934 * C:: C and C@t{++}
16937 * Objective-C:: Objective-C
16938 * OpenCL C:: OpenCL C
16939 * Fortran:: Fortran
16942 * Modula-2:: Modula-2
16947 @subsection C and C@t{++}
16949 @cindex C and C@t{++}
16950 @cindex expressions in C or C@t{++}
16952 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16953 to both languages. Whenever this is the case, we discuss those languages
16957 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16958 @cindex @sc{gnu} C@t{++}
16959 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16960 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16961 effectively, you must compile your C@t{++} programs with a supported
16962 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16963 compiler (@code{aCC}).
16966 * C Operators:: C and C@t{++} operators
16967 * C Constants:: C and C@t{++} constants
16968 * C Plus Plus Expressions:: C@t{++} expressions
16969 * C Defaults:: Default settings for C and C@t{++}
16970 * C Checks:: C and C@t{++} type and range checks
16971 * Debugging C:: @value{GDBN} and C
16972 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16973 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16977 @subsubsection C and C@t{++} Operators
16979 @cindex C and C@t{++} operators
16981 Operators must be defined on values of specific types. For instance,
16982 @code{+} is defined on numbers, but not on structures. Operators are
16983 often defined on groups of types.
16985 For the purposes of C and C@t{++}, the following definitions hold:
16990 @emph{Integral types} include @code{int} with any of its storage-class
16991 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16994 @emph{Floating-point types} include @code{float}, @code{double}, and
16995 @code{long double} (if supported by the target platform).
16998 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
17001 @emph{Scalar types} include all of the above.
17006 The following operators are supported. They are listed here
17007 in order of increasing precedence:
17011 The comma or sequencing operator. Expressions in a comma-separated list
17012 are evaluated from left to right, with the result of the entire
17013 expression being the last expression evaluated.
17016 Assignment. The value of an assignment expression is the value
17017 assigned. Defined on scalar types.
17020 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
17021 and translated to @w{@code{@var{a} = @var{a op b}}}.
17022 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
17023 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
17024 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
17027 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
17028 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
17029 should be of an integral type.
17032 Logical @sc{or}. Defined on integral types.
17035 Logical @sc{and}. Defined on integral types.
17038 Bitwise @sc{or}. Defined on integral types.
17041 Bitwise exclusive-@sc{or}. Defined on integral types.
17044 Bitwise @sc{and}. Defined on integral types.
17047 Equality and inequality. Defined on scalar types. The value of these
17048 expressions is 0 for false and non-zero for true.
17050 @item <@r{, }>@r{, }<=@r{, }>=
17051 Less than, greater than, less than or equal, greater than or equal.
17052 Defined on scalar types. The value of these expressions is 0 for false
17053 and non-zero for true.
17056 left shift, and right shift. Defined on integral types.
17059 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17062 Addition and subtraction. Defined on integral types, floating-point types and
17065 @item *@r{, }/@r{, }%
17066 Multiplication, division, and modulus. Multiplication and division are
17067 defined on integral and floating-point types. Modulus is defined on
17071 Increment and decrement. When appearing before a variable, the
17072 operation is performed before the variable is used in an expression;
17073 when appearing after it, the variable's value is used before the
17074 operation takes place.
17077 Pointer dereferencing. Defined on pointer types. Same precedence as
17081 Address operator. Defined on variables. Same precedence as @code{++}.
17083 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
17084 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
17085 to examine the address
17086 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
17090 Negative. Defined on integral and floating-point types. Same
17091 precedence as @code{++}.
17094 Logical negation. Defined on integral types. Same precedence as
17098 Bitwise complement operator. Defined on integral types. Same precedence as
17103 Structure member, and pointer-to-structure member. For convenience,
17104 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
17105 pointer based on the stored type information.
17106 Defined on @code{struct} and @code{union} data.
17109 Dereferences of pointers to members.
17112 Array indexing. @code{@var{a}[@var{i}]} is defined as
17113 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
17116 Function parameter list. Same precedence as @code{->}.
17119 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
17120 and @code{class} types.
17123 Doubled colons also represent the @value{GDBN} scope operator
17124 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
17128 If an operator is redefined in the user code, @value{GDBN} usually
17129 attempts to invoke the redefined version instead of using the operator's
17130 predefined meaning.
17133 @subsubsection C and C@t{++} Constants
17135 @cindex C and C@t{++} constants
17137 @value{GDBN} allows you to express the constants of C and C@t{++} in the
17142 Integer constants are a sequence of digits. Octal constants are
17143 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
17144 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
17145 @samp{l}, specifying that the constant should be treated as a
17149 Floating point constants are a sequence of digits, followed by a decimal
17150 point, followed by a sequence of digits, and optionally followed by an
17151 exponent. An exponent is of the form:
17152 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
17153 sequence of digits. The @samp{+} is optional for positive exponents.
17154 A floating-point constant may also end with a letter @samp{f} or
17155 @samp{F}, specifying that the constant should be treated as being of
17156 the @code{float} (as opposed to the default @code{double}) type; or with
17157 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
17161 Enumerated constants consist of enumerated identifiers, or their
17162 integral equivalents.
17165 Character constants are a single character surrounded by single quotes
17166 (@code{'}), or a number---the ordinal value of the corresponding character
17167 (usually its @sc{ascii} value). Within quotes, the single character may
17168 be represented by a letter or by @dfn{escape sequences}, which are of
17169 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
17170 of the character's ordinal value; or of the form @samp{\@var{x}}, where
17171 @samp{@var{x}} is a predefined special character---for example,
17172 @samp{\n} for newline.
17174 Wide character constants can be written by prefixing a character
17175 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
17176 form of @samp{x}. The target wide character set is used when
17177 computing the value of this constant (@pxref{Character Sets}).
17180 String constants are a sequence of character constants surrounded by
17181 double quotes (@code{"}). Any valid character constant (as described
17182 above) may appear. Double quotes within the string must be preceded by
17183 a backslash, so for instance @samp{"a\"b'c"} is a string of five
17186 Wide string constants can be written by prefixing a string constant
17187 with @samp{L}, as in C. The target wide character set is used when
17188 computing the value of this constant (@pxref{Character Sets}).
17191 Pointer constants are an integral value. You can also write pointers
17192 to constants using the C operator @samp{&}.
17195 Array constants are comma-separated lists surrounded by braces @samp{@{}
17196 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
17197 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
17198 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
17201 @node C Plus Plus Expressions
17202 @subsubsection C@t{++} Expressions
17204 @cindex expressions in C@t{++}
17205 @value{GDBN} expression handling can interpret most C@t{++} expressions.
17207 @cindex debugging C@t{++} programs
17208 @cindex C@t{++} compilers
17209 @cindex debug formats and C@t{++}
17210 @cindex @value{NGCC} and C@t{++}
17212 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
17213 the proper compiler and the proper debug format. Currently,
17214 @value{GDBN} works best when debugging C@t{++} code that is compiled
17215 with the most recent version of @value{NGCC} possible. The DWARF
17216 debugging format is preferred; @value{NGCC} defaults to this on most
17217 popular platforms. Other compilers and/or debug formats are likely to
17218 work badly or not at all when using @value{GDBN} to debug C@t{++}
17219 code. @xref{Compilation}.
17224 @cindex member functions
17226 Member function calls are allowed; you can use expressions like
17229 count = aml->GetOriginal(x, y)
17232 @vindex this@r{, inside C@t{++} member functions}
17233 @cindex namespace in C@t{++}
17235 While a member function is active (in the selected stack frame), your
17236 expressions have the same namespace available as the member function;
17237 that is, @value{GDBN} allows implicit references to the class instance
17238 pointer @code{this} following the same rules as C@t{++}. @code{using}
17239 declarations in the current scope are also respected by @value{GDBN}.
17241 @cindex call overloaded functions
17242 @cindex overloaded functions, calling
17243 @cindex type conversions in C@t{++}
17245 You can call overloaded functions; @value{GDBN} resolves the function
17246 call to the right definition, with some restrictions. @value{GDBN} does not
17247 perform overload resolution involving user-defined type conversions,
17248 calls to constructors, or instantiations of templates that do not exist
17249 in the program. It also cannot handle ellipsis argument lists or
17252 It does perform integral conversions and promotions, floating-point
17253 promotions, arithmetic conversions, pointer conversions, conversions of
17254 class objects to base classes, and standard conversions such as those of
17255 functions or arrays to pointers; it requires an exact match on the
17256 number of function arguments.
17258 Overload resolution is always performed, unless you have specified
17259 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
17260 ,@value{GDBN} Features for C@t{++}}.
17262 You must specify @code{set overload-resolution off} in order to use an
17263 explicit function signature to call an overloaded function, as in
17265 p 'foo(char,int)'('x', 13)
17268 The @value{GDBN} command-completion facility can simplify this;
17269 see @ref{Completion, ,Command Completion}.
17271 @cindex reference declarations
17273 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
17274 references; you can use them in expressions just as you do in C@t{++}
17275 source---they are automatically dereferenced.
17277 In the parameter list shown when @value{GDBN} displays a frame, the values of
17278 reference variables are not displayed (unlike other variables); this
17279 avoids clutter, since references are often used for large structures.
17280 The @emph{address} of a reference variable is always shown, unless
17281 you have specified @samp{set print address off}.
17284 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
17285 expressions can use it just as expressions in your program do. Since
17286 one scope may be defined in another, you can use @code{::} repeatedly if
17287 necessary, for example in an expression like
17288 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
17289 resolving name scope by reference to source files, in both C and C@t{++}
17290 debugging (@pxref{Variables, ,Program Variables}).
17293 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
17298 @subsubsection C and C@t{++} Defaults
17300 @cindex C and C@t{++} defaults
17302 If you allow @value{GDBN} to set range checking automatically, it
17303 defaults to @code{off} whenever the working language changes to
17304 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
17305 selects the working language.
17307 If you allow @value{GDBN} to set the language automatically, it
17308 recognizes source files whose names end with @file{.c}, @file{.C}, or
17309 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
17310 these files, it sets the working language to C or C@t{++}.
17311 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
17312 for further details.
17315 @subsubsection C and C@t{++} Type and Range Checks
17317 @cindex C and C@t{++} checks
17319 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
17320 checking is used. However, if you turn type checking off, @value{GDBN}
17321 will allow certain non-standard conversions, such as promoting integer
17322 constants to pointers.
17324 Range checking, if turned on, is done on mathematical operations. Array
17325 indices are not checked, since they are often used to index a pointer
17326 that is not itself an array.
17329 @subsubsection @value{GDBN} and C
17331 The @code{set print union} and @code{show print union} commands apply to
17332 the @code{union} type. When set to @samp{on}, any @code{union} that is
17333 inside a @code{struct} or @code{class} is also printed. Otherwise, it
17334 appears as @samp{@{...@}}.
17336 The @code{@@} operator aids in the debugging of dynamic arrays, formed
17337 with pointers and a memory allocation function. @xref{Expressions,
17340 @node Debugging C Plus Plus
17341 @subsubsection @value{GDBN} Features for C@t{++}
17343 @cindex commands for C@t{++}
17345 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
17346 designed specifically for use with C@t{++}. Here is a summary:
17349 @cindex break in overloaded functions
17350 @item @r{breakpoint menus}
17351 When you want a breakpoint in a function whose name is overloaded,
17352 @value{GDBN} has the capability to display a menu of possible breakpoint
17353 locations to help you specify which function definition you want.
17354 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17356 @cindex overloading in C@t{++}
17357 @item rbreak @var{regex}
17358 Setting breakpoints using regular expressions is helpful for setting
17359 breakpoints on overloaded functions that are not members of any special
17361 @xref{Set Breaks, ,Setting Breakpoints}.
17363 @cindex C@t{++} exception handling
17365 @itemx catch rethrow
17367 Debug C@t{++} exception handling using these commands. @xref{Set
17368 Catchpoints, , Setting Catchpoints}.
17370 @cindex inheritance
17371 @item ptype @var{typename}
17372 Print inheritance relationships as well as other information for type
17374 @xref{Symbols, ,Examining the Symbol Table}.
17376 @item info vtbl @var{expression}.
17377 The @code{info vtbl} command can be used to display the virtual
17378 method tables of the object computed by @var{expression}. This shows
17379 one entry per virtual table; there may be multiple virtual tables when
17380 multiple inheritance is in use.
17382 @cindex C@t{++} demangling
17383 @item demangle @var{name}
17384 Demangle @var{name}.
17385 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17387 @cindex C@t{++} symbol display
17388 @item set print demangle
17389 @itemx show print demangle
17390 @itemx set print asm-demangle
17391 @itemx show print asm-demangle
17392 Control whether C@t{++} symbols display in their source form, both when
17393 displaying code as C@t{++} source and when displaying disassemblies.
17394 @xref{Print Settings, ,Print Settings}.
17396 @item set print object
17397 @itemx show print object
17398 Choose whether to print derived (actual) or declared types of objects.
17399 @xref{Print Settings, ,Print Settings}.
17401 @item set print vtbl
17402 @itemx show print vtbl
17403 Control the format for printing virtual function tables.
17404 @xref{Print Settings, ,Print Settings}.
17405 (The @code{vtbl} commands do not work on programs compiled with the HP
17406 ANSI C@t{++} compiler (@code{aCC}).)
17408 @kindex set overload-resolution
17409 @cindex overloaded functions, overload resolution
17410 @item set overload-resolution on
17411 Enable overload resolution for C@t{++} expression evaluation. The default
17412 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17413 and searches for a function whose signature matches the argument types,
17414 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17415 Expressions, ,C@t{++} Expressions}, for details).
17416 If it cannot find a match, it emits a message.
17418 @item set overload-resolution off
17419 Disable overload resolution for C@t{++} expression evaluation. For
17420 overloaded functions that are not class member functions, @value{GDBN}
17421 chooses the first function of the specified name that it finds in the
17422 symbol table, whether or not its arguments are of the correct type. For
17423 overloaded functions that are class member functions, @value{GDBN}
17424 searches for a function whose signature @emph{exactly} matches the
17427 @kindex show overload-resolution
17428 @item show overload-resolution
17429 Show the current setting of overload resolution.
17431 @item @r{Overloaded symbol names}
17432 You can specify a particular definition of an overloaded symbol, using
17433 the same notation that is used to declare such symbols in C@t{++}: type
17434 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17435 also use the @value{GDBN} command-line word completion facilities to list the
17436 available choices, or to finish the type list for you.
17437 @xref{Completion,, Command Completion}, for details on how to do this.
17439 @item @r{Breakpoints in template functions}
17441 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17442 template parameter lists when it encounters a symbol which includes a
17443 C@t{++} template. This permits setting breakpoints on families of template functions
17444 or functions whose parameters include template types.
17446 The @kbd{-qualified} flag may be used to override this behavior, causing
17447 @value{GDBN} to search for a specific function or type.
17449 The @value{GDBN} command-line word completion facility also understands
17450 template parameters and may be used to list available choices or finish
17451 template parameter lists for you. @xref{Completion,, Command Completion}, for
17452 details on how to do this.
17454 @item @r{Breakpoints in functions with ABI tags}
17456 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17457 correspond to changes in the ABI of a type, function, or variable that
17458 would not otherwise be reflected in a mangled name. See
17459 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17462 The ABI tags are visible in C@t{++} demangled names. For example, a
17463 function that returns a std::string:
17466 std::string function(int);
17470 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17471 tag, and @value{GDBN} displays the symbol like this:
17474 function[abi:cxx11](int)
17477 You can set a breakpoint on such functions simply as if they had no
17481 (@value{GDBP}) b function(int)
17482 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17483 (@value{GDBP}) info breakpoints
17484 Num Type Disp Enb Address What
17485 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17489 On the rare occasion you need to disambiguate between different ABI
17490 tags, you can do so by simply including the ABI tag in the function
17494 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17498 @node Decimal Floating Point
17499 @subsubsection Decimal Floating Point format
17500 @cindex decimal floating point format
17502 @value{GDBN} can examine, set and perform computations with numbers in
17503 decimal floating point format, which in the C language correspond to the
17504 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17505 specified by the extension to support decimal floating-point arithmetic.
17507 There are two encodings in use, depending on the architecture: BID (Binary
17508 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17509 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17512 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17513 to manipulate decimal floating point numbers, it is not possible to convert
17514 (using a cast, for example) integers wider than 32-bit to decimal float.
17516 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17517 point computations, error checking in decimal float operations ignores
17518 underflow, overflow and divide by zero exceptions.
17520 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17521 to inspect @code{_Decimal128} values stored in floating point registers.
17522 See @ref{PowerPC,,PowerPC} for more details.
17528 @value{GDBN} can be used to debug programs written in D and compiled with
17529 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17530 specific feature --- dynamic arrays.
17535 @cindex Go (programming language)
17536 @value{GDBN} can be used to debug programs written in Go and compiled with
17537 @file{gccgo} or @file{6g} compilers.
17539 Here is a summary of the Go-specific features and restrictions:
17542 @cindex current Go package
17543 @item The current Go package
17544 The name of the current package does not need to be specified when
17545 specifying global variables and functions.
17547 For example, given the program:
17551 var myglob = "Shall we?"
17557 When stopped inside @code{main} either of these work:
17560 (@value{GDBP}) p myglob
17561 (@value{GDBP}) p main.myglob
17564 @cindex builtin Go types
17565 @item Builtin Go types
17566 The @code{string} type is recognized by @value{GDBN} and is printed
17569 @cindex builtin Go functions
17570 @item Builtin Go functions
17571 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17572 function and handles it internally.
17574 @cindex restrictions on Go expressions
17575 @item Restrictions on Go expressions
17576 All Go operators are supported except @code{&^}.
17577 The Go @code{_} ``blank identifier'' is not supported.
17578 Automatic dereferencing of pointers is not supported.
17582 @subsection Objective-C
17584 @cindex Objective-C
17585 This section provides information about some commands and command
17586 options that are useful for debugging Objective-C code. See also
17587 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17588 few more commands specific to Objective-C support.
17591 * Method Names in Commands::
17592 * The Print Command with Objective-C::
17595 @node Method Names in Commands
17596 @subsubsection Method Names in Commands
17598 The following commands have been extended to accept Objective-C method
17599 names as line specifications:
17601 @kindex clear@r{, and Objective-C}
17602 @kindex break@r{, and Objective-C}
17603 @kindex info line@r{, and Objective-C}
17604 @kindex jump@r{, and Objective-C}
17605 @kindex list@r{, and Objective-C}
17609 @item @code{info line}
17614 A fully qualified Objective-C method name is specified as
17617 -[@var{Class} @var{methodName}]
17620 where the minus sign is used to indicate an instance method and a
17621 plus sign (not shown) is used to indicate a class method. The class
17622 name @var{Class} and method name @var{methodName} are enclosed in
17623 brackets, similar to the way messages are specified in Objective-C
17624 source code. For example, to set a breakpoint at the @code{create}
17625 instance method of class @code{Fruit} in the program currently being
17629 break -[Fruit create]
17632 To list ten program lines around the @code{initialize} class method,
17636 list +[NSText initialize]
17639 In the current version of @value{GDBN}, the plus or minus sign is
17640 required. In future versions of @value{GDBN}, the plus or minus
17641 sign will be optional, but you can use it to narrow the search. It
17642 is also possible to specify just a method name:
17648 You must specify the complete method name, including any colons. If
17649 your program's source files contain more than one @code{create} method,
17650 you'll be presented with a numbered list of classes that implement that
17651 method. Indicate your choice by number, or type @samp{0} to exit if
17654 As another example, to clear a breakpoint established at the
17655 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17658 clear -[NSWindow makeKeyAndOrderFront:]
17661 @node The Print Command with Objective-C
17662 @subsubsection The Print Command With Objective-C
17663 @cindex Objective-C, print objects
17664 @kindex print-object
17665 @kindex po @r{(@code{print-object})}
17667 The print command has also been extended to accept methods. For example:
17670 print -[@var{object} hash]
17673 @cindex print an Objective-C object description
17674 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17676 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17677 and print the result. Also, an additional command has been added,
17678 @code{print-object} or @code{po} for short, which is meant to print
17679 the description of an object. However, this command may only work
17680 with certain Objective-C libraries that have a particular hook
17681 function, @code{_NSPrintForDebugger}, defined.
17684 @subsection OpenCL C
17687 This section provides information about @value{GDBN}s OpenCL C support.
17690 * OpenCL C Datatypes::
17691 * OpenCL C Expressions::
17692 * OpenCL C Operators::
17695 @node OpenCL C Datatypes
17696 @subsubsection OpenCL C Datatypes
17698 @cindex OpenCL C Datatypes
17699 @value{GDBN} supports the builtin scalar and vector datatypes specified
17700 by OpenCL 1.1. In addition the half- and double-precision floating point
17701 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17702 extensions are also known to @value{GDBN}.
17704 @node OpenCL C Expressions
17705 @subsubsection OpenCL C Expressions
17707 @cindex OpenCL C Expressions
17708 @value{GDBN} supports accesses to vector components including the access as
17709 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17710 supported by @value{GDBN} can be used as well.
17712 @node OpenCL C Operators
17713 @subsubsection OpenCL C Operators
17715 @cindex OpenCL C Operators
17716 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17720 @subsection Fortran
17721 @cindex Fortran-specific support in @value{GDBN}
17723 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17724 all Fortran language features are available yet.
17726 @cindex trailing underscore, in Fortran symbols
17727 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17728 among them) append an underscore to the names of variables and
17729 functions. When you debug programs compiled by those compilers, you
17730 will need to refer to variables and functions with a trailing
17733 @cindex Fortran Defaults
17734 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17735 default uses case-insensitive matching for Fortran symbols. You can
17736 change that with the @samp{set case-insensitive} command, see
17737 @ref{Symbols}, for the details.
17740 * Fortran Types:: Fortran builtin types
17741 * Fortran Operators:: Fortran operators and expressions
17742 * Fortran Intrinsics:: Fortran intrinsic functions
17743 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17746 @node Fortran Types
17747 @subsubsection Fortran Types
17749 @cindex Fortran Types
17751 In Fortran the primitive data-types have an associated @code{KIND} type
17752 parameter, written as @samp{@var{type}*@var{kindparam}},
17753 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17754 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17755 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17756 The kind of a type can be retrieved by using the intrinsic function
17757 @code{KIND}, see @ref{Fortran Intrinsics}.
17759 Generally, the actual implementation of the @code{KIND} type parameter is
17760 compiler specific. In @value{GDBN} the kind parameter is implemented in
17761 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17762 kind parameter for a given @var{type} specifies its size in memory --- a
17763 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17764 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17765 type for which the kind of the type does not specify its entire size, but
17766 the size of each of the two @code{Real}'s it is composed of. A
17767 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17770 For every type there is also a default kind associated with it, e.g.@
17771 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17772 table below for default types). The default types are the same as in @sc{gnu}
17773 compilers but note, that the @sc{gnu} default types can actually be changed by
17774 compiler flags such as @option{-fdefault-integer-8} and
17775 @option{-fdefault-real-8}.
17777 Not every kind parameter is valid for every type and in @value{GDBN} the
17778 following type kinds are available.
17782 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17783 @code{Integer} = @code{Integer*4}.
17786 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17787 @code{Logical} = @code{Logical*4}.
17790 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17793 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17798 @node Fortran Operators
17799 @subsubsection Fortran Operators and Expressions
17801 @cindex Fortran operators and expressions
17803 Operators must be defined on values of specific types. For instance,
17804 @code{+} is defined on numbers, but not on characters or other non-
17805 arithmetic types. Operators are often defined on groups of types.
17809 The exponentiation operator. It raises the first operand to the power
17813 The range operator. Normally used in the form of array(low:high) to
17814 represent a section of array.
17817 The access component operator. Normally used to access elements in derived
17818 types. Also suitable for unions. As unions aren't part of regular Fortran,
17819 this can only happen when accessing a register that uses a gdbarch-defined
17822 The scope operator. Normally used to access variables in modules or
17823 to set breakpoints on subroutines nested in modules or in other
17824 subroutines (internal subroutines).
17827 @node Fortran Intrinsics
17828 @subsubsection Fortran Intrinsics
17830 @cindex Fortran Intrinsics
17832 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17833 an incomplete subset of those procedures and their overloads. Some of these
17834 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17838 Computes the absolute value of its argument @var{a}. Currently not supported
17839 for @code{Complex} arguments.
17841 @item ALLOCATE(@var{array})
17842 Returns whether @var{array} is allocated or not.
17844 @item ASSOCIATED(@var{pointer} [, @var{target}])
17845 Returns the association status of the pointer @var{pointer} or, if @var{target}
17846 is present, whether @var{pointer} is associated with the target @var{target}.
17848 @item CEILING(@var{a} [, @var{kind}])
17849 Computes the least integer greater than or equal to @var{a}. The optional
17850 parameter @var{kind} specifies the kind of the return type
17851 @code{Integer(@var{kind})}.
17853 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17854 Returns a complex number where @var{x} is converted to the real component. If
17855 @var{y} is present it is converted to the imaginary component. If @var{y} is
17856 not present then the imaginary component is set to @code{0.0} except if @var{x}
17857 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17858 the kind of the return type @code{Complex(@var{kind})}.
17860 @item FLOOR(@var{a} [, @var{kind}])
17861 Computes the greatest integer less than or equal to @var{a}. The optional
17862 parameter @var{kind} specifies the kind of the return type
17863 @code{Integer(@var{kind})}.
17865 @item KIND(@var{a})
17866 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17868 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17869 Returns the lower bounds of an @var{array}, or a single lower bound along the
17870 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17871 the kind of the return type @code{Integer(@var{kind})}.
17874 Returns the address of @var{x} as an @code{Integer}.
17876 @item MOD(@var{a}, @var{p})
17877 Computes the remainder of the division of @var{a} by @var{p}.
17879 @item MODULO(@var{a}, @var{p})
17880 Computes the @var{a} modulo @var{p}.
17882 @item RANK(@var{a})
17883 Returns the rank of a scalar or array (scalars have rank @code{0}).
17885 @item SHAPE(@var{a})
17886 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17888 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17889 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17890 total number of elements in @var{array} if @var{dim} is absent. The optional
17891 parameter @var{kind} specifies the kind of the return type
17892 @code{Integer(@var{kind})}.
17894 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17895 Returns the upper bounds of an @var{array}, or a single upper bound along the
17896 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17897 the kind of the return type @code{Integer(@var{kind})}.
17901 @node Special Fortran Commands
17902 @subsubsection Special Fortran Commands
17904 @cindex Special Fortran commands
17906 @value{GDBN} has some commands to support Fortran-specific features,
17907 such as displaying common blocks.
17910 @cindex @code{COMMON} blocks, Fortran
17911 @kindex info common
17912 @item info common @r{[}@var{common-name}@r{]}
17913 This command prints the values contained in the Fortran @code{COMMON}
17914 block whose name is @var{common-name}. With no argument, the names of
17915 all @code{COMMON} blocks visible at the current program location are
17917 @cindex arrays slices (Fortran)
17918 @kindex set fortran repack-array-slices
17919 @kindex show fortran repack-array-slices
17920 @item set fortran repack-array-slices [on|off]
17921 @item show fortran repack-array-slices
17922 When taking a slice from an array, a Fortran compiler can choose to
17923 either produce an array descriptor that describes the slice in place,
17924 or it may repack the slice, copying the elements of the slice into a
17925 new region of memory.
17927 When this setting is on, then @value{GDBN} will also repack array
17928 slices in some situations. When this setting is off, then
17929 @value{GDBN} will create array descriptors for slices that reference
17930 the original data in place.
17932 @value{GDBN} will never repack an array slice if the data for the
17933 slice is contiguous within the original array.
17935 @value{GDBN} will always repack string slices if the data for the
17936 slice is non-contiguous within the original string as @value{GDBN}
17937 does not support printing non-contiguous strings.
17939 The default for this setting is @code{off}.
17945 @cindex Pascal support in @value{GDBN}, limitations
17946 Debugging Pascal programs which use sets, subranges, file variables, or
17947 nested functions does not currently work. @value{GDBN} does not support
17948 entering expressions, printing values, or similar features using Pascal
17951 The Pascal-specific command @code{set print pascal_static-members}
17952 controls whether static members of Pascal objects are displayed.
17953 @xref{Print Settings, pascal_static-members}.
17958 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17959 Programming Language}. Type- and value-printing, and expression
17960 parsing, are reasonably complete. However, there are a few
17961 peculiarities and holes to be aware of.
17965 Linespecs (@pxref{Location Specifications}) are never relative to the
17966 current crate. Instead, they act as if there were a global namespace
17967 of crates, somewhat similar to the way @code{extern crate} behaves.
17969 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17970 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17971 to set a breakpoint in a function named @samp{f} in a crate named
17974 As a consequence of this approach, linespecs also cannot refer to
17975 items using @samp{self::} or @samp{super::}.
17978 Because @value{GDBN} implements Rust name-lookup semantics in
17979 expressions, it will sometimes prepend the current crate to a name.
17980 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17981 @samp{K}, then @code{print ::x::y} will try to find the symbol
17984 However, since it is useful to be able to refer to other crates when
17985 debugging, @value{GDBN} provides the @code{extern} extension to
17986 circumvent this. To use the extension, just put @code{extern} before
17987 a path expression to refer to the otherwise unavailable ``global''
17990 In the above example, if you wanted to refer to the symbol @samp{y} in
17991 the crate @samp{x}, you would use @code{print extern x::y}.
17994 The Rust expression evaluator does not support ``statement-like''
17995 expressions such as @code{if} or @code{match}, or lambda expressions.
17998 Tuple expressions are not implemented.
18001 The Rust expression evaluator does not currently implement the
18002 @code{Drop} trait. Objects that may be created by the evaluator will
18003 never be destroyed.
18006 @value{GDBN} does not implement type inference for generics. In order
18007 to call generic functions or otherwise refer to generic items, you
18008 will have to specify the type parameters manually.
18011 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
18012 cases this does not cause any problems. However, in an expression
18013 context, completing a generic function name will give syntactically
18014 invalid results. This happens because Rust requires the @samp{::}
18015 operator between the function name and its generic arguments. For
18016 example, @value{GDBN} might provide a completion like
18017 @code{crate::f<u32>}, where the parser would require
18018 @code{crate::f::<u32>}.
18021 As of this writing, the Rust compiler (version 1.8) has a few holes in
18022 the debugging information it generates. These holes prevent certain
18023 features from being implemented by @value{GDBN}:
18027 Method calls cannot be made via traits.
18030 Operator overloading is not implemented.
18033 When debugging in a monomorphized function, you cannot use the generic
18037 The type @code{Self} is not available.
18040 @code{use} statements are not available, so some names may not be
18041 available in the crate.
18046 @subsection Modula-2
18048 @cindex Modula-2, @value{GDBN} support
18050 The extensions made to @value{GDBN} to support Modula-2 only support
18051 output from the @sc{gnu} Modula-2 compiler (which is currently being
18052 developed). Other Modula-2 compilers are not currently supported, and
18053 attempting to debug executables produced by them is most likely
18054 to give an error as @value{GDBN} reads in the executable's symbol
18057 @cindex expressions in Modula-2
18059 * M2 Operators:: Built-in operators
18060 * Built-In Func/Proc:: Built-in functions and procedures
18061 * M2 Constants:: Modula-2 constants
18062 * M2 Types:: Modula-2 types
18063 * M2 Defaults:: Default settings for Modula-2
18064 * Deviations:: Deviations from standard Modula-2
18065 * M2 Checks:: Modula-2 type and range checks
18066 * M2 Scope:: The scope operators @code{::} and @code{.}
18067 * GDB/M2:: @value{GDBN} and Modula-2
18071 @subsubsection Operators
18072 @cindex Modula-2 operators
18074 Operators must be defined on values of specific types. For instance,
18075 @code{+} is defined on numbers, but not on structures. Operators are
18076 often defined on groups of types. For the purposes of Modula-2, the
18077 following definitions hold:
18082 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
18086 @emph{Character types} consist of @code{CHAR} and its subranges.
18089 @emph{Floating-point types} consist of @code{REAL}.
18092 @emph{Pointer types} consist of anything declared as @code{POINTER TO
18096 @emph{Scalar types} consist of all of the above.
18099 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
18102 @emph{Boolean types} consist of @code{BOOLEAN}.
18106 The following operators are supported, and appear in order of
18107 increasing precedence:
18111 Function argument or array index separator.
18114 Assignment. The value of @var{var} @code{:=} @var{value} is
18118 Less than, greater than on integral, floating-point, or enumerated
18122 Less than or equal to, greater than or equal to
18123 on integral, floating-point and enumerated types, or set inclusion on
18124 set types. Same precedence as @code{<}.
18126 @item =@r{, }<>@r{, }#
18127 Equality and two ways of expressing inequality, valid on scalar types.
18128 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
18129 available for inequality, since @code{#} conflicts with the script
18133 Set membership. Defined on set types and the types of their members.
18134 Same precedence as @code{<}.
18137 Boolean disjunction. Defined on boolean types.
18140 Boolean conjunction. Defined on boolean types.
18143 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
18146 Addition and subtraction on integral and floating-point types, or union
18147 and difference on set types.
18150 Multiplication on integral and floating-point types, or set intersection
18154 Division on floating-point types, or symmetric set difference on set
18155 types. Same precedence as @code{*}.
18158 Integer division and remainder. Defined on integral types. Same
18159 precedence as @code{*}.
18162 Negative. Defined on @code{INTEGER} and @code{REAL} data.
18165 Pointer dereferencing. Defined on pointer types.
18168 Boolean negation. Defined on boolean types. Same precedence as
18172 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
18173 precedence as @code{^}.
18176 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
18179 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
18183 @value{GDBN} and Modula-2 scope operators.
18187 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
18188 treats the use of the operator @code{IN}, or the use of operators
18189 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
18190 @code{<=}, and @code{>=} on sets as an error.
18194 @node Built-In Func/Proc
18195 @subsubsection Built-in Functions and Procedures
18196 @cindex Modula-2 built-ins
18198 Modula-2 also makes available several built-in procedures and functions.
18199 In describing these, the following metavariables are used:
18204 represents an @code{ARRAY} variable.
18207 represents a @code{CHAR} constant or variable.
18210 represents a variable or constant of integral type.
18213 represents an identifier that belongs to a set. Generally used in the
18214 same function with the metavariable @var{s}. The type of @var{s} should
18215 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
18218 represents a variable or constant of integral or floating-point type.
18221 represents a variable or constant of floating-point type.
18227 represents a variable.
18230 represents a variable or constant of one of many types. See the
18231 explanation of the function for details.
18234 All Modula-2 built-in procedures also return a result, described below.
18238 Returns the absolute value of @var{n}.
18241 If @var{c} is a lower case letter, it returns its upper case
18242 equivalent, otherwise it returns its argument.
18245 Returns the character whose ordinal value is @var{i}.
18248 Decrements the value in the variable @var{v} by one. Returns the new value.
18250 @item DEC(@var{v},@var{i})
18251 Decrements the value in the variable @var{v} by @var{i}. Returns the
18254 @item EXCL(@var{m},@var{s})
18255 Removes the element @var{m} from the set @var{s}. Returns the new
18258 @item FLOAT(@var{i})
18259 Returns the floating point equivalent of the integer @var{i}.
18261 @item HIGH(@var{a})
18262 Returns the index of the last member of @var{a}.
18265 Increments the value in the variable @var{v} by one. Returns the new value.
18267 @item INC(@var{v},@var{i})
18268 Increments the value in the variable @var{v} by @var{i}. Returns the
18271 @item INCL(@var{m},@var{s})
18272 Adds the element @var{m} to the set @var{s} if it is not already
18273 there. Returns the new set.
18276 Returns the maximum value of the type @var{t}.
18279 Returns the minimum value of the type @var{t}.
18282 Returns boolean TRUE if @var{i} is an odd number.
18285 Returns the ordinal value of its argument. For example, the ordinal
18286 value of a character is its @sc{ascii} value (on machines supporting
18287 the @sc{ascii} character set). The argument @var{x} must be of an
18288 ordered type, which include integral, character and enumerated types.
18290 @item SIZE(@var{x})
18291 Returns the size of its argument. The argument @var{x} can be a
18292 variable or a type.
18294 @item TRUNC(@var{r})
18295 Returns the integral part of @var{r}.
18297 @item TSIZE(@var{x})
18298 Returns the size of its argument. The argument @var{x} can be a
18299 variable or a type.
18301 @item VAL(@var{t},@var{i})
18302 Returns the member of the type @var{t} whose ordinal value is @var{i}.
18306 @emph{Warning:} Sets and their operations are not yet supported, so
18307 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
18311 @cindex Modula-2 constants
18313 @subsubsection Constants
18315 @value{GDBN} allows you to express the constants of Modula-2 in the following
18321 Integer constants are simply a sequence of digits. When used in an
18322 expression, a constant is interpreted to be type-compatible with the
18323 rest of the expression. Hexadecimal integers are specified by a
18324 trailing @samp{H}, and octal integers by a trailing @samp{B}.
18327 Floating point constants appear as a sequence of digits, followed by a
18328 decimal point and another sequence of digits. An optional exponent can
18329 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
18330 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
18331 digits of the floating point constant must be valid decimal (base 10)
18335 Character constants consist of a single character enclosed by a pair of
18336 like quotes, either single (@code{'}) or double (@code{"}). They may
18337 also be expressed by their ordinal value (their @sc{ascii} value, usually)
18338 followed by a @samp{C}.
18341 String constants consist of a sequence of characters enclosed by a
18342 pair of like quotes, either single (@code{'}) or double (@code{"}).
18343 Escape sequences in the style of C are also allowed. @xref{C
18344 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
18348 Enumerated constants consist of an enumerated identifier.
18351 Boolean constants consist of the identifiers @code{TRUE} and
18355 Pointer constants consist of integral values only.
18358 Set constants are not yet supported.
18362 @subsubsection Modula-2 Types
18363 @cindex Modula-2 types
18365 Currently @value{GDBN} can print the following data types in Modula-2
18366 syntax: array types, record types, set types, pointer types, procedure
18367 types, enumerated types, subrange types and base types. You can also
18368 print the contents of variables declared using these type.
18369 This section gives a number of simple source code examples together with
18370 sample @value{GDBN} sessions.
18372 The first example contains the following section of code:
18381 and you can request @value{GDBN} to interrogate the type and value of
18382 @code{r} and @code{s}.
18385 (@value{GDBP}) print s
18387 (@value{GDBP}) ptype s
18389 (@value{GDBP}) print r
18391 (@value{GDBP}) ptype r
18396 Likewise if your source code declares @code{s} as:
18400 s: SET ['A'..'Z'] ;
18404 then you may query the type of @code{s} by:
18407 (@value{GDBP}) ptype s
18408 type = SET ['A'..'Z']
18412 Note that at present you cannot interactively manipulate set
18413 expressions using the debugger.
18415 The following example shows how you might declare an array in Modula-2
18416 and how you can interact with @value{GDBN} to print its type and contents:
18420 s: ARRAY [-10..10] OF CHAR ;
18424 (@value{GDBP}) ptype s
18425 ARRAY [-10..10] OF CHAR
18428 Note that the array handling is not yet complete and although the type
18429 is printed correctly, expression handling still assumes that all
18430 arrays have a lower bound of zero and not @code{-10} as in the example
18433 Here are some more type related Modula-2 examples:
18437 colour = (blue, red, yellow, green) ;
18438 t = [blue..yellow] ;
18446 The @value{GDBN} interaction shows how you can query the data type
18447 and value of a variable.
18450 (@value{GDBP}) print s
18452 (@value{GDBP}) ptype t
18453 type = [blue..yellow]
18457 In this example a Modula-2 array is declared and its contents
18458 displayed. Observe that the contents are written in the same way as
18459 their @code{C} counterparts.
18463 s: ARRAY [1..5] OF CARDINAL ;
18469 (@value{GDBP}) print s
18470 $1 = @{1, 0, 0, 0, 0@}
18471 (@value{GDBP}) ptype s
18472 type = ARRAY [1..5] OF CARDINAL
18475 The Modula-2 language interface to @value{GDBN} also understands
18476 pointer types as shown in this example:
18480 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18487 and you can request that @value{GDBN} describes the type of @code{s}.
18490 (@value{GDBP}) ptype s
18491 type = POINTER TO ARRAY [1..5] OF CARDINAL
18494 @value{GDBN} handles compound types as we can see in this example.
18495 Here we combine array types, record types, pointer types and subrange
18506 myarray = ARRAY myrange OF CARDINAL ;
18507 myrange = [-2..2] ;
18509 s: POINTER TO ARRAY myrange OF foo ;
18513 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18517 (@value{GDBP}) ptype s
18518 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18521 f3 : ARRAY [-2..2] OF CARDINAL;
18526 @subsubsection Modula-2 Defaults
18527 @cindex Modula-2 defaults
18529 If type and range checking are set automatically by @value{GDBN}, they
18530 both default to @code{on} whenever the working language changes to
18531 Modula-2. This happens regardless of whether you or @value{GDBN}
18532 selected the working language.
18534 If you allow @value{GDBN} to set the language automatically, then entering
18535 code compiled from a file whose name ends with @file{.mod} sets the
18536 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18537 Infer the Source Language}, for further details.
18540 @subsubsection Deviations from Standard Modula-2
18541 @cindex Modula-2, deviations from
18543 A few changes have been made to make Modula-2 programs easier to debug.
18544 This is done primarily via loosening its type strictness:
18548 Unlike in standard Modula-2, pointer constants can be formed by
18549 integers. This allows you to modify pointer variables during
18550 debugging. (In standard Modula-2, the actual address contained in a
18551 pointer variable is hidden from you; it can only be modified
18552 through direct assignment to another pointer variable or expression that
18553 returned a pointer.)
18556 C escape sequences can be used in strings and characters to represent
18557 non-printable characters. @value{GDBN} prints out strings with these
18558 escape sequences embedded. Single non-printable characters are
18559 printed using the @samp{CHR(@var{nnn})} format.
18562 The assignment operator (@code{:=}) returns the value of its right-hand
18566 All built-in procedures both modify @emph{and} return their argument.
18570 @subsubsection Modula-2 Type and Range Checks
18571 @cindex Modula-2 checks
18574 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18577 @c FIXME remove warning when type/range checks added
18579 @value{GDBN} considers two Modula-2 variables type equivalent if:
18583 They are of types that have been declared equivalent via a @code{TYPE
18584 @var{t1} = @var{t2}} statement
18587 They have been declared on the same line. (Note: This is true of the
18588 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18591 As long as type checking is enabled, any attempt to combine variables
18592 whose types are not equivalent is an error.
18594 Range checking is done on all mathematical operations, assignment, array
18595 index bounds, and all built-in functions and procedures.
18598 @subsubsection The Scope Operators @code{::} and @code{.}
18600 @cindex @code{.}, Modula-2 scope operator
18601 @cindex colon, doubled as scope operator
18603 @vindex colon-colon@r{, in Modula-2}
18604 @c Info cannot handle :: but TeX can.
18607 @vindex ::@r{, in Modula-2}
18610 There are a few subtle differences between the Modula-2 scope operator
18611 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18616 @var{module} . @var{id}
18617 @var{scope} :: @var{id}
18621 where @var{scope} is the name of a module or a procedure,
18622 @var{module} the name of a module, and @var{id} is any declared
18623 identifier within your program, except another module.
18625 Using the @code{::} operator makes @value{GDBN} search the scope
18626 specified by @var{scope} for the identifier @var{id}. If it is not
18627 found in the specified scope, then @value{GDBN} searches all scopes
18628 enclosing the one specified by @var{scope}.
18630 Using the @code{.} operator makes @value{GDBN} search the current scope for
18631 the identifier specified by @var{id} that was imported from the
18632 definition module specified by @var{module}. With this operator, it is
18633 an error if the identifier @var{id} was not imported from definition
18634 module @var{module}, or if @var{id} is not an identifier in
18638 @subsubsection @value{GDBN} and Modula-2
18640 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18641 Five subcommands of @code{set print} and @code{show print} apply
18642 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18643 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18644 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18645 analogue in Modula-2.
18647 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18648 with any language, is not useful with Modula-2. Its
18649 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18650 created in Modula-2 as they can in C or C@t{++}. However, because an
18651 address can be specified by an integral constant, the construct
18652 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18654 @cindex @code{#} in Modula-2
18655 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18656 interpreted as the beginning of a comment. Use @code{<>} instead.
18662 The extensions made to @value{GDBN} for Ada only support
18663 output from the @sc{gnu} Ada (GNAT) compiler.
18664 Other Ada compilers are not currently supported, and
18665 attempting to debug executables produced by them is most likely
18669 @cindex expressions in Ada
18671 * Ada Mode Intro:: General remarks on the Ada syntax
18672 and semantics supported by Ada mode
18674 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18675 * Additions to Ada:: Extensions of the Ada expression syntax.
18676 * Overloading support for Ada:: Support for expressions involving overloaded
18678 * Stopping Before Main Program:: Debugging the program during elaboration.
18679 * Ada Exceptions:: Ada Exceptions
18680 * Ada Tasks:: Listing and setting breakpoints in tasks.
18681 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18682 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18684 * Ada Source Character Set:: Character set of Ada source files.
18685 * Ada Glitches:: Known peculiarities of Ada mode.
18688 @node Ada Mode Intro
18689 @subsubsection Introduction
18690 @cindex Ada mode, general
18692 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18693 syntax, with some extensions.
18694 The philosophy behind the design of this subset is
18698 That @value{GDBN} should provide basic literals and access to operations for
18699 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18700 leaving more sophisticated computations to subprograms written into the
18701 program (which therefore may be called from @value{GDBN}).
18704 That type safety and strict adherence to Ada language restrictions
18705 are not particularly important to the @value{GDBN} user.
18708 That brevity is important to the @value{GDBN} user.
18711 Thus, for brevity, the debugger acts as if all names declared in
18712 user-written packages are directly visible, even if they are not visible
18713 according to Ada rules, thus making it unnecessary to fully qualify most
18714 names with their packages, regardless of context. Where this causes
18715 ambiguity, @value{GDBN} asks the user's intent.
18717 The debugger will start in Ada mode if it detects an Ada main program.
18718 As for other languages, it will enter Ada mode when stopped in a program that
18719 was translated from an Ada source file.
18721 While in Ada mode, you may use `@t{--}' for comments. This is useful
18722 mostly for documenting command files. The standard @value{GDBN} comment
18723 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18724 middle (to allow based literals).
18726 @node Omissions from Ada
18727 @subsubsection Omissions from Ada
18728 @cindex Ada, omissions from
18730 Here are the notable omissions from the subset:
18734 Only a subset of the attributes are supported:
18738 @t{'First}, @t{'Last}, and @t{'Length}
18739 on array objects (not on types and subtypes).
18742 @t{'Min} and @t{'Max}.
18745 @t{'Pos} and @t{'Val}.
18751 @t{'Range} on array objects (not subtypes), but only as the right
18752 operand of the membership (@code{in}) operator.
18755 @t{'Access}, @t{'Unchecked_Access}, and
18756 @t{'Unrestricted_Access} (a GNAT extension).
18763 The names in @code{Characters.Latin_1} are not available.
18766 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18767 equality of representations. They will generally work correctly
18768 for strings and arrays whose elements have integer or enumeration types.
18769 They may not work correctly for arrays whose element
18770 types have user-defined equality, for arrays of real values
18771 (in particular, IEEE-conformant floating point, because of negative
18772 zeroes and NaNs), and for arrays whose elements contain unused bits with
18773 indeterminate values.
18776 The other component-by-component array operations (@code{and}, @code{or},
18777 @code{xor}, @code{not}, and relational tests other than equality)
18778 are not implemented.
18781 @cindex array aggregates (Ada)
18782 @cindex record aggregates (Ada)
18783 @cindex aggregates (Ada)
18784 There is limited support for array and record aggregates. They are
18785 permitted only on the right sides of assignments, as in these examples:
18788 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18789 (@value{GDBP}) set An_Array := (1, others => 0)
18790 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18791 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18792 (@value{GDBP}) set A_Record := (1, "Peter", True);
18793 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18797 discriminant's value by assigning an aggregate has an
18798 undefined effect if that discriminant is used within the record.
18799 However, you can first modify discriminants by directly assigning to
18800 them (which normally would not be allowed in Ada), and then performing an
18801 aggregate assignment. For example, given a variable @code{A_Rec}
18802 declared to have a type such as:
18805 type Rec (Len : Small_Integer := 0) is record
18807 Vals : IntArray (1 .. Len);
18811 you can assign a value with a different size of @code{Vals} with two
18815 (@value{GDBP}) set A_Rec.Len := 4
18816 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18819 As this example also illustrates, @value{GDBN} is very loose about the usual
18820 rules concerning aggregates. You may leave out some of the
18821 components of an array or record aggregate (such as the @code{Len}
18822 component in the assignment to @code{A_Rec} above); they will retain their
18823 original values upon assignment. You may freely use dynamic values as
18824 indices in component associations. You may even use overlapping or
18825 redundant component associations, although which component values are
18826 assigned in such cases is not defined.
18829 Calls to dispatching subprograms are not implemented.
18832 The overloading algorithm is much more limited (i.e., less selective)
18833 than that of real Ada. It makes only limited use of the context in
18834 which a subexpression appears to resolve its meaning, and it is much
18835 looser in its rules for allowing type matches. As a result, some
18836 function calls will be ambiguous, and the user will be asked to choose
18837 the proper resolution.
18840 The @code{new} operator is not implemented.
18843 Entry calls are not implemented.
18846 Aside from printing, arithmetic operations on the native VAX floating-point
18847 formats are not supported.
18850 It is not possible to slice a packed array.
18853 The names @code{True} and @code{False}, when not part of a qualified name,
18854 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18856 Should your program
18857 redefine these names in a package or procedure (at best a dubious practice),
18858 you will have to use fully qualified names to access their new definitions.
18861 Based real literals are not implemented.
18864 @node Additions to Ada
18865 @subsubsection Additions to Ada
18866 @cindex Ada, deviations from
18868 As it does for other languages, @value{GDBN} makes certain generic
18869 extensions to Ada (@pxref{Expressions}):
18873 If the expression @var{E} is a variable residing in memory (typically
18874 a local variable or array element) and @var{N} is a positive integer,
18875 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18876 @var{N}-1 adjacent variables following it in memory as an array. In
18877 Ada, this operator is generally not necessary, since its prime use is
18878 in displaying parts of an array, and slicing will usually do this in
18879 Ada. However, there are occasional uses when debugging programs in
18880 which certain debugging information has been optimized away.
18883 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18884 appears in function or file @var{B}.'' When @var{B} is a file name,
18885 you must typically surround it in single quotes.
18888 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18889 @var{type} that appears at address @var{addr}.''
18892 A name starting with @samp{$} is a convenience variable
18893 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18896 In addition, @value{GDBN} provides a few other shortcuts and outright
18897 additions specific to Ada:
18901 The assignment statement is allowed as an expression, returning
18902 its right-hand operand as its value. Thus, you may enter
18905 (@value{GDBP}) set x := y + 3
18906 (@value{GDBP}) print A(tmp := y + 1)
18910 The semicolon is allowed as an ``operator,'' returning as its value
18911 the value of its right-hand operand.
18912 This allows, for example,
18913 complex conditional breaks:
18916 (@value{GDBP}) break f
18917 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18921 An extension to based literals can be used to specify the exact byte
18922 contents of a floating-point literal. After the base, you can use
18923 from zero to two @samp{l} characters, followed by an @samp{f}. The
18924 number of @samp{l} characters controls the width of the resulting real
18925 constant: zero means @code{Float} is used, one means
18926 @code{Long_Float}, and two means @code{Long_Long_Float}.
18929 (@value{GDBP}) print 16f#41b80000#
18934 Rather than use catenation and symbolic character names to introduce special
18935 characters into strings, one may instead use a special bracket notation,
18936 which is also used to print strings. A sequence of characters of the form
18937 @samp{["@var{XX}"]} within a string or character literal denotes the
18938 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18939 sequence of characters @samp{["""]} also denotes a single quotation mark
18940 in strings. For example,
18942 "One line.["0a"]Next line.["0a"]"
18945 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18949 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18950 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18954 (@value{GDBP}) print 'max(x, y)
18958 When printing arrays, @value{GDBN} uses positional notation when the
18959 array has a lower bound of 1, and uses a modified named notation otherwise.
18960 For example, a one-dimensional array of three integers with a lower bound
18961 of 3 might print as
18968 That is, in contrast to valid Ada, only the first component has a @code{=>}
18972 You may abbreviate attributes in expressions with any unique,
18973 multi-character subsequence of
18974 their names (an exact match gets preference).
18975 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18976 in place of @t{a'length}.
18979 @cindex quoting Ada internal identifiers
18980 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18981 to lower case. The GNAT compiler uses upper-case characters for
18982 some of its internal identifiers, which are normally of no interest to users.
18983 For the rare occasions when you actually have to look at them,
18984 enclose them in angle brackets to avoid the lower-case mapping.
18987 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18991 Printing an object of class-wide type or dereferencing an
18992 access-to-class-wide value will display all the components of the object's
18993 specific type (as indicated by its run-time tag). Likewise, component
18994 selection on such a value will operate on the specific type of the
18999 @node Overloading support for Ada
19000 @subsubsection Overloading support for Ada
19001 @cindex overloading, Ada
19003 The debugger supports limited overloading. Given a subprogram call in which
19004 the function symbol has multiple definitions, it will use the number of
19005 actual parameters and some information about their types to attempt to narrow
19006 the set of definitions. It also makes very limited use of context, preferring
19007 procedures to functions in the context of the @code{call} command, and
19008 functions to procedures elsewhere.
19010 If, after narrowing, the set of matching definitions still contains more than
19011 one definition, @value{GDBN} will display a menu to query which one it should
19015 (@value{GDBP}) print f(1)
19016 Multiple matches for f
19018 [1] foo.f (integer) return boolean at foo.adb:23
19019 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
19023 In this case, just select one menu entry either to cancel expression evaluation
19024 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
19025 instance (type the corresponding number and press @key{RET}).
19027 Here are a couple of commands to customize @value{GDBN}'s behavior in this
19032 @kindex set ada print-signatures
19033 @item set ada print-signatures
19034 Control whether parameter types and return types are displayed in overloads
19035 selection menus. It is @code{on} by default.
19036 @xref{Overloading support for Ada}.
19038 @kindex show ada print-signatures
19039 @item show ada print-signatures
19040 Show the current setting for displaying parameter types and return types in
19041 overloads selection menu.
19042 @xref{Overloading support for Ada}.
19046 @node Stopping Before Main Program
19047 @subsubsection Stopping at the Very Beginning
19049 @cindex breakpointing Ada elaboration code
19050 It is sometimes necessary to debug the program during elaboration, and
19051 before reaching the main procedure.
19052 As defined in the Ada Reference
19053 Manual, the elaboration code is invoked from a procedure called
19054 @code{adainit}. To run your program up to the beginning of
19055 elaboration, simply use the following two commands:
19056 @code{tbreak adainit} and @code{run}.
19058 @node Ada Exceptions
19059 @subsubsection Ada Exceptions
19061 A command is provided to list all Ada exceptions:
19064 @kindex info exceptions
19065 @item info exceptions
19066 @itemx info exceptions @var{regexp}
19067 The @code{info exceptions} command allows you to list all Ada exceptions
19068 defined within the program being debugged, as well as their addresses.
19069 With a regular expression, @var{regexp}, as argument, only those exceptions
19070 whose names match @var{regexp} are listed.
19073 Below is a small example, showing how the command can be used, first
19074 without argument, and next with a regular expression passed as an
19078 (@value{GDBP}) info exceptions
19079 All defined Ada exceptions:
19080 constraint_error: 0x613da0
19081 program_error: 0x613d20
19082 storage_error: 0x613ce0
19083 tasking_error: 0x613ca0
19084 const.aint_global_e: 0x613b00
19085 (@value{GDBP}) info exceptions const.aint
19086 All Ada exceptions matching regular expression "const.aint":
19087 constraint_error: 0x613da0
19088 const.aint_global_e: 0x613b00
19091 It is also possible to ask @value{GDBN} to stop your program's execution
19092 when an exception is raised. For more details, see @ref{Set Catchpoints}.
19095 @subsubsection Extensions for Ada Tasks
19096 @cindex Ada, tasking
19098 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
19099 @value{GDBN} provides the following task-related commands:
19104 This command shows a list of current Ada tasks, as in the following example:
19111 (@value{GDBP}) info tasks
19112 ID TID P-ID Pri State Name
19113 1 8088000 0 15 Child Activation Wait main_task
19114 2 80a4000 1 15 Accept Statement b
19115 3 809a800 1 15 Child Activation Wait a
19116 * 4 80ae800 3 15 Runnable c
19121 In this listing, the asterisk before the last task indicates it to be the
19122 task currently being inspected.
19126 Represents @value{GDBN}'s internal task number.
19132 The parent's task ID (@value{GDBN}'s internal task number).
19135 The base priority of the task.
19138 Current state of the task.
19142 The task has been created but has not been activated. It cannot be
19146 The task is not blocked for any reason known to Ada. (It may be waiting
19147 for a mutex, though.) It is conceptually "executing" in normal mode.
19150 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
19151 that were waiting on terminate alternatives have been awakened and have
19152 terminated themselves.
19154 @item Child Activation Wait
19155 The task is waiting for created tasks to complete activation.
19157 @item Accept or Select Term
19158 The task is waiting on an accept or selective wait statement.
19160 @item Waiting on entry call
19161 The task is waiting on an entry call.
19163 @item Async Select Wait
19164 The task is waiting to start the abortable part of an asynchronous
19168 The task is waiting on a select statement with only a delay
19171 @item Child Termination Wait
19172 The task is sleeping having completed a master within itself, and is
19173 waiting for the tasks dependent on that master to become terminated or
19174 waiting on a terminate Phase.
19176 @item Wait Child in Term Alt
19177 The task is sleeping waiting for tasks on terminate alternatives to
19178 finish terminating.
19180 @item Asynchronous Hold
19181 The task has been held by @code{Ada.Asynchronous_Task_Control.Hold_Task}.
19184 The task has been created and is being made runnable.
19186 @item Selective Wait
19187 The task is waiting in a selective wait statement.
19189 @item Accepting RV with @var{taskno}
19190 The task is accepting a rendez-vous with the task @var{taskno}.
19192 @item Waiting on RV with @var{taskno}
19193 The task is waiting for a rendez-vous with the task @var{taskno}.
19197 Name of the task in the program.
19201 @kindex info task @var{taskno}
19202 @item info task @var{taskno}
19203 This command shows detailed information on the specified task, as in
19204 the following example:
19209 (@value{GDBP}) info tasks
19210 ID TID P-ID Pri State Name
19211 1 8077880 0 15 Child Activation Wait main_task
19212 * 2 807c468 1 15 Runnable task_1
19213 (@value{GDBP}) info task 2
19214 Ada Task: 0x807c468
19218 Parent: 1 ("main_task")
19224 @kindex task@r{ (Ada)}
19225 @cindex current Ada task ID
19226 This command prints the ID and name of the current task.
19232 (@value{GDBP}) info tasks
19233 ID TID P-ID Pri State Name
19234 1 8077870 0 15 Child Activation Wait main_task
19235 * 2 807c458 1 15 Runnable some_task
19236 (@value{GDBP}) task
19237 [Current task is 2 "some_task"]
19240 @item task @var{taskno}
19241 @cindex Ada task switching
19242 This command is like the @code{thread @var{thread-id}}
19243 command (@pxref{Threads}). It switches the context of debugging
19244 from the current task to the given task.
19250 (@value{GDBP}) info tasks
19251 ID TID P-ID Pri State Name
19252 1 8077870 0 15 Child Activation Wait main_task
19253 * 2 807c458 1 15 Runnable some_task
19254 (@value{GDBP}) task 1
19255 [Switching to task 1 "main_task"]
19256 #0 0x8067726 in pthread_cond_wait ()
19258 #0 0x8067726 in pthread_cond_wait ()
19259 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
19260 #2 0x805cb63 in system.task_primitives.operations.sleep ()
19261 #3 0x806153e in system.tasking.stages.activate_tasks ()
19262 #4 0x804aacc in un () at un.adb:5
19265 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
19266 The @code{task apply} command is the Ada tasking analogue of
19267 @code{thread apply} (@pxref{Threads}). It allows you to apply the
19268 named @var{command} to one or more tasks. Specify the tasks that you
19269 want affected using a list of task IDs, or specify @code{all} to apply
19272 The @var{flag} arguments control what output to produce and how to
19273 handle errors raised when applying @var{command} to a task.
19274 @var{flag} must start with a @code{-} directly followed by one letter
19275 in @code{qcs}. If several flags are provided, they must be given
19276 individually, such as @code{-c -q}.
19278 By default, @value{GDBN} displays some task information before the
19279 output produced by @var{command}, and an error raised during the
19280 execution of a @var{command} will abort @code{task apply}. The
19281 following flags can be used to fine-tune this behavior:
19285 The flag @code{-c}, which stands for @samp{continue}, causes any
19286 errors in @var{command} to be displayed, and the execution of
19287 @code{task apply} then continues.
19289 The flag @code{-s}, which stands for @samp{silent}, causes any errors
19290 or empty output produced by a @var{command} to be silently ignored.
19291 That is, the execution continues, but the task information and errors
19294 The flag @code{-q} (@samp{quiet}) disables printing the task
19298 Flags @code{-c} and @code{-s} cannot be used together.
19300 @item break @var{locspec} task @var{taskno}
19301 @itemx break @var{locspec} task @var{taskno} if @dots{}
19302 @cindex breakpoints and tasks, in Ada
19303 @cindex task breakpoints, in Ada
19304 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
19305 These commands are like the @code{break @dots{} thread @dots{}}
19306 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
19307 the various forms of @var{locspec}.
19309 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
19310 to specify that you only want @value{GDBN} to stop the program when a
19311 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
19312 numeric task identifiers assigned by @value{GDBN}, shown in the first
19313 column of the @samp{info tasks} display.
19315 If you do not specify @samp{task @var{taskno}} when you set a
19316 breakpoint, the breakpoint applies to @emph{all} tasks of your
19319 You can use the @code{task} qualifier on conditional breakpoints as
19320 well; in this case, place @samp{task @var{taskno}} before the
19321 breakpoint condition (before the @code{if}).
19329 (@value{GDBP}) info tasks
19330 ID TID P-ID Pri State Name
19331 1 140022020 0 15 Child Activation Wait main_task
19332 2 140045060 1 15 Accept/Select Wait t2
19333 3 140044840 1 15 Runnable t1
19334 * 4 140056040 1 15 Runnable t3
19335 (@value{GDBP}) b 15 task 2
19336 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
19337 (@value{GDBP}) cont
19342 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
19344 (@value{GDBP}) info tasks
19345 ID TID P-ID Pri State Name
19346 1 140022020 0 15 Child Activation Wait main_task
19347 * 2 140045060 1 15 Runnable t2
19348 3 140044840 1 15 Runnable t1
19349 4 140056040 1 15 Delay Sleep t3
19353 @node Ada Tasks and Core Files
19354 @subsubsection Tasking Support when Debugging Core Files
19355 @cindex Ada tasking and core file debugging
19357 When inspecting a core file, as opposed to debugging a live program,
19358 tasking support may be limited or even unavailable, depending on
19359 the platform being used.
19360 For instance, on x86-linux, the list of tasks is available, but task
19361 switching is not supported.
19363 On certain platforms, the debugger needs to perform some
19364 memory writes in order to provide Ada tasking support. When inspecting
19365 a core file, this means that the core file must be opened with read-write
19366 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19367 Under these circumstances, you should make a backup copy of the core
19368 file before inspecting it with @value{GDBN}.
19370 @node Ravenscar Profile
19371 @subsubsection Tasking Support when using the Ravenscar Profile
19372 @cindex Ravenscar Profile
19374 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19375 specifically designed for systems with safety-critical real-time
19379 @kindex set ravenscar task-switching on
19380 @cindex task switching with program using Ravenscar Profile
19381 @item set ravenscar task-switching on
19382 Allows task switching when debugging a program that uses the Ravenscar
19383 Profile. This is the default.
19385 @kindex set ravenscar task-switching off
19386 @item set ravenscar task-switching off
19387 Turn off task switching when debugging a program that uses the Ravenscar
19388 Profile. This is mostly intended to disable the code that adds support
19389 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19390 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19391 To be effective, this command should be run before the program is started.
19393 @kindex show ravenscar task-switching
19394 @item show ravenscar task-switching
19395 Show whether it is possible to switch from task to task in a program
19396 using the Ravenscar Profile.
19400 @cindex Ravenscar thread
19401 When Ravenscar task-switching is enabled, Ravenscar tasks are
19402 announced by @value{GDBN} as if they were threads:
19406 [New Ravenscar Thread 0x2b8f0]
19409 Both Ravenscar tasks and the underlying CPU threads will show up in
19410 the output of @code{info threads}:
19415 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19416 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19417 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19418 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19419 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19420 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19423 One known limitation of the Ravenscar support in @value{GDBN} is that
19424 it isn't currently possible to single-step through the runtime
19425 initialization sequence. If you need to debug this code, you should
19426 use @code{set ravenscar task-switching off}.
19428 @node Ada Source Character Set
19429 @subsubsection Ada Source Character Set
19430 @cindex Ada, source character set
19432 The GNAT compiler supports a number of character sets for source
19433 files. @xref{Character Set Control, , Character Set Control,
19434 gnat_ugn}. @value{GDBN} includes support for this as well.
19437 @item set ada source-charset @var{charset}
19438 @kindex set ada source-charset
19439 Set the source character set for Ada. The character set must be
19440 supported by GNAT. Because this setting affects the decoding of
19441 symbols coming from the debug information in your program, the setting
19442 should be set as early as possible. The default is @code{ISO-8859-1},
19443 because that is also GNAT's default.
19445 @item show ada source-charset
19446 @kindex show ada source-charset
19447 Show the current source character set for Ada.
19451 @subsubsection Known Peculiarities of Ada Mode
19452 @cindex Ada, problems
19454 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19455 we know of several problems with and limitations of Ada mode in
19457 some of which will be fixed with planned future releases of the debugger
19458 and the GNU Ada compiler.
19462 Static constants that the compiler chooses not to materialize as objects in
19463 storage are invisible to the debugger.
19466 Named parameter associations in function argument lists are ignored (the
19467 argument lists are treated as positional).
19470 Many useful library packages are currently invisible to the debugger.
19473 Fixed-point arithmetic, conversions, input, and output is carried out using
19474 floating-point arithmetic, and may give results that only approximate those on
19478 The GNAT compiler never generates the prefix @code{Standard} for any of
19479 the standard symbols defined by the Ada language. @value{GDBN} knows about
19480 this: it will strip the prefix from names when you use it, and will never
19481 look for a name you have so qualified among local symbols, nor match against
19482 symbols in other packages or subprograms. If you have
19483 defined entities anywhere in your program other than parameters and
19484 local variables whose simple names match names in @code{Standard},
19485 GNAT's lack of qualification here can cause confusion. When this happens,
19486 you can usually resolve the confusion
19487 by qualifying the problematic names with package
19488 @code{Standard} explicitly.
19491 Older versions of the compiler sometimes generate erroneous debugging
19492 information, resulting in the debugger incorrectly printing the value
19493 of affected entities. In some cases, the debugger is able to work
19494 around an issue automatically. In other cases, the debugger is able
19495 to work around the issue, but the work-around has to be specifically
19498 @kindex set ada trust-PAD-over-XVS
19499 @kindex show ada trust-PAD-over-XVS
19502 @item set ada trust-PAD-over-XVS on
19503 Configure GDB to strictly follow the GNAT encoding when computing the
19504 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19505 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19506 a complete description of the encoding used by the GNAT compiler).
19507 This is the default.
19509 @item set ada trust-PAD-over-XVS off
19510 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19511 sometimes prints the wrong value for certain entities, changing @code{ada
19512 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19513 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19514 @code{off}, but this incurs a slight performance penalty, so it is
19515 recommended to leave this setting to @code{on} unless necessary.
19519 @cindex GNAT descriptive types
19520 @cindex GNAT encoding
19521 Internally, the debugger also relies on the compiler following a number
19522 of conventions known as the @samp{GNAT Encoding}, all documented in
19523 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19524 how the debugging information should be generated for certain types.
19525 In particular, this convention makes use of @dfn{descriptive types},
19526 which are artificial types generated purely to help the debugger.
19528 These encodings were defined at a time when the debugging information
19529 format used was not powerful enough to describe some of the more complex
19530 types available in Ada. Since DWARF allows us to express nearly all
19531 Ada features, the long-term goal is to slowly replace these descriptive
19532 types by their pure DWARF equivalent. To facilitate that transition,
19533 a new maintenance option is available to force the debugger to ignore
19534 those descriptive types. It allows the user to quickly evaluate how
19535 well @value{GDBN} works without them.
19539 @kindex maint ada set ignore-descriptive-types
19540 @item maintenance ada set ignore-descriptive-types [on|off]
19541 Control whether the debugger should ignore descriptive types.
19542 The default is not to ignore descriptives types (@code{off}).
19544 @kindex maint ada show ignore-descriptive-types
19545 @item maintenance ada show ignore-descriptive-types
19546 Show if descriptive types are ignored by @value{GDBN}.
19550 @node Unsupported Languages
19551 @section Unsupported Languages
19553 @cindex unsupported languages
19554 @cindex minimal language
19555 In addition to the other fully-supported programming languages,
19556 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19557 It does not represent a real programming language, but provides a set
19558 of capabilities close to what the C or assembly languages provide.
19559 This should allow most simple operations to be performed while debugging
19560 an application that uses a language currently not supported by @value{GDBN}.
19562 If the language is set to @code{auto}, @value{GDBN} will automatically
19563 select this language if the current frame corresponds to an unsupported
19567 @chapter Examining the Symbol Table
19569 The commands described in this chapter allow you to inquire about the
19570 symbols (names of variables, functions and types) defined in your
19571 program. This information is inherent in the text of your program and
19572 does not change as your program executes. @value{GDBN} finds it in your
19573 program's symbol table, in the file indicated when you started @value{GDBN}
19574 (@pxref{File Options, ,Choosing Files}), or by one of the
19575 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19577 @cindex symbol names
19578 @cindex names of symbols
19579 @cindex quoting names
19580 @anchor{quoting names}
19581 Occasionally, you may need to refer to symbols that contain unusual
19582 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19583 most frequent case is in referring to static variables in other
19584 source files (@pxref{Variables,,Program Variables}). File names
19585 are recorded in object files as debugging symbols, but @value{GDBN} would
19586 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19587 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19588 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19595 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19598 @cindex case-insensitive symbol names
19599 @cindex case sensitivity in symbol names
19600 @kindex set case-sensitive
19601 @item set case-sensitive on
19602 @itemx set case-sensitive off
19603 @itemx set case-sensitive auto
19604 Normally, when @value{GDBN} looks up symbols, it matches their names
19605 with case sensitivity determined by the current source language.
19606 Occasionally, you may wish to control that. The command @code{set
19607 case-sensitive} lets you do that by specifying @code{on} for
19608 case-sensitive matches or @code{off} for case-insensitive ones. If
19609 you specify @code{auto}, case sensitivity is reset to the default
19610 suitable for the source language. The default is case-sensitive
19611 matches for all languages except for Fortran, for which the default is
19612 case-insensitive matches.
19614 @kindex show case-sensitive
19615 @item show case-sensitive
19616 This command shows the current setting of case sensitivity for symbols
19619 @kindex set print type methods
19620 @item set print type methods
19621 @itemx set print type methods on
19622 @itemx set print type methods off
19623 Normally, when @value{GDBN} prints a class, it displays any methods
19624 declared in that class. You can control this behavior either by
19625 passing the appropriate flag to @code{ptype}, or using @command{set
19626 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19627 display the methods; this is the default. Specifying @code{off} will
19628 cause @value{GDBN} to omit the methods.
19630 @kindex show print type methods
19631 @item show print type methods
19632 This command shows the current setting of method display when printing
19635 @kindex set print type nested-type-limit
19636 @item set print type nested-type-limit @var{limit}
19637 @itemx set print type nested-type-limit unlimited
19638 Set the limit of displayed nested types that the type printer will
19639 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19640 nested definitions. By default, the type printer will not show any nested
19641 types defined in classes.
19643 @kindex show print type nested-type-limit
19644 @item show print type nested-type-limit
19645 This command shows the current display limit of nested types when
19648 @kindex set print type typedefs
19649 @item set print type typedefs
19650 @itemx set print type typedefs on
19651 @itemx set print type typedefs off
19653 Normally, when @value{GDBN} prints a class, it displays any typedefs
19654 defined in that class. You can control this behavior either by
19655 passing the appropriate flag to @code{ptype}, or using @command{set
19656 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19657 display the typedef definitions; this is the default. Specifying
19658 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19659 Note that this controls whether the typedef definition itself is
19660 printed, not whether typedef names are substituted when printing other
19663 @kindex show print type typedefs
19664 @item show print type typedefs
19665 This command shows the current setting of typedef display when
19668 @kindex set print type hex
19669 @item set print type hex
19670 @itemx set print type hex on
19671 @itemx set print type hex off
19673 When @value{GDBN} prints sizes and offsets of struct members, it can use
19674 either the decimal or hexadecimal notation. You can select one or the
19675 other either by passing the appropriate flag to @code{ptype}, or by using
19676 the @command{set print type hex} command.
19678 @kindex show print type hex
19679 @item show print type hex
19680 This command shows whether the sizes and offsets of struct members are
19681 printed in decimal or hexadecimal notation.
19683 @kindex info address
19684 @cindex address of a symbol
19685 @item info address @var{symbol}
19686 Describe where the data for @var{symbol} is stored. For a register
19687 variable, this says which register it is kept in. For a non-register
19688 local variable, this prints the stack-frame offset at which the variable
19691 Note the contrast with @samp{print &@var{symbol}}, which does not work
19692 at all for a register variable, and for a stack local variable prints
19693 the exact address of the current instantiation of the variable.
19695 @kindex info symbol
19696 @cindex symbol from address
19697 @cindex closest symbol and offset for an address
19698 @item info symbol @var{addr}
19699 Print the name of a symbol which is stored at the address @var{addr}.
19700 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19701 nearest symbol and an offset from it:
19704 (@value{GDBP}) info symbol 0x54320
19705 _initialize_vx + 396 in section .text
19709 This is the opposite of the @code{info address} command. You can use
19710 it to find out the name of a variable or a function given its address.
19712 For dynamically linked executables, the name of executable or shared
19713 library containing the symbol is also printed:
19716 (@value{GDBP}) info symbol 0x400225
19717 _start + 5 in section .text of /tmp/a.out
19718 (@value{GDBP}) info symbol 0x2aaaac2811cf
19719 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19724 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19725 Demangle @var{name}.
19726 If @var{language} is provided it is the name of the language to demangle
19727 @var{name} in. Otherwise @var{name} is demangled in the current language.
19729 The @samp{--} option specifies the end of options,
19730 and is useful when @var{name} begins with a dash.
19732 The parameter @code{demangle-style} specifies how to interpret the kind
19733 of mangling used. @xref{Print Settings}.
19736 @item whatis[/@var{flags}] [@var{arg}]
19737 Print the data type of @var{arg}, which can be either an expression
19738 or a name of a data type. With no argument, print the data type of
19739 @code{$}, the last value in the value history.
19741 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19742 is not actually evaluated, and any side-effecting operations (such as
19743 assignments or function calls) inside it do not take place.
19745 If @var{arg} is a variable or an expression, @code{whatis} prints its
19746 literal type as it is used in the source code. If the type was
19747 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19748 the data type underlying the @code{typedef}. If the type of the
19749 variable or the expression is a compound data type, such as
19750 @code{struct} or @code{class}, @code{whatis} never prints their
19751 fields or methods. It just prints the @code{struct}/@code{class}
19752 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19753 such a compound data type, use @code{ptype}.
19755 If @var{arg} is a type name that was defined using @code{typedef},
19756 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19757 Unrolling means that @code{whatis} will show the underlying type used
19758 in the @code{typedef} declaration of @var{arg}. However, if that
19759 underlying type is also a @code{typedef}, @code{whatis} will not
19762 For C code, the type names may also have the form @samp{class
19763 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19764 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19766 @var{flags} can be used to modify how the type is displayed.
19767 Available flags are:
19771 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19772 parameters and typedefs defined in a class when printing the class'
19773 members. The @code{/r} flag disables this.
19776 Do not print methods defined in the class.
19779 Print methods defined in the class. This is the default, but the flag
19780 exists in case you change the default with @command{set print type methods}.
19783 Do not print typedefs defined in the class. Note that this controls
19784 whether the typedef definition itself is printed, not whether typedef
19785 names are substituted when printing other types.
19788 Print typedefs defined in the class. This is the default, but the flag
19789 exists in case you change the default with @command{set print type typedefs}.
19792 Print the offsets and sizes of fields in a struct, similar to what the
19793 @command{pahole} tool does. This option implies the @code{/tm} flags.
19796 Use hexadecimal notation when printing offsets and sizes of fields in a
19800 Use decimal notation when printing offsets and sizes of fields in a
19803 For example, given the following declarations:
19839 Issuing a @kbd{ptype /o struct tuv} command would print:
19842 (@value{GDBP}) ptype /o struct tuv
19843 /* offset | size */ type = struct tuv @{
19844 /* 0 | 4 */ int a1;
19845 /* XXX 4-byte hole */
19846 /* 8 | 8 */ char *a2;
19847 /* 16 | 4 */ int a3;
19849 /* total size (bytes): 24 */
19853 Notice the format of the first column of comments. There, you can
19854 find two parts separated by the @samp{|} character: the @emph{offset},
19855 which indicates where the field is located inside the struct, in
19856 bytes, and the @emph{size} of the field. Another interesting line is
19857 the marker of a @emph{hole} in the struct, indicating that it may be
19858 possible to pack the struct and make it use less space by reorganizing
19861 It is also possible to print offsets inside an union:
19864 (@value{GDBP}) ptype /o union qwe
19865 /* offset | size */ type = union qwe @{
19866 /* 24 */ struct tuv @{
19867 /* 0 | 4 */ int a1;
19868 /* XXX 4-byte hole */
19869 /* 8 | 8 */ char *a2;
19870 /* 16 | 4 */ int a3;
19872 /* total size (bytes): 24 */
19874 /* 40 */ struct xyz @{
19875 /* 0 | 4 */ int f1;
19876 /* 4 | 1 */ char f2;
19877 /* XXX 3-byte hole */
19878 /* 8 | 8 */ void *f3;
19879 /* 16 | 24 */ struct tuv @{
19880 /* 16 | 4 */ int a1;
19881 /* XXX 4-byte hole */
19882 /* 24 | 8 */ char *a2;
19883 /* 32 | 4 */ int a3;
19885 /* total size (bytes): 24 */
19888 /* total size (bytes): 40 */
19891 /* total size (bytes): 40 */
19895 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19896 same space (because we are dealing with an union), the offset is not
19897 printed for them. However, you can still examine the offset of each
19898 of these structures' fields.
19900 Another useful scenario is printing the offsets of a struct containing
19904 (@value{GDBP}) ptype /o struct tyu
19905 /* offset | size */ type = struct tyu @{
19906 /* 0:31 | 4 */ int a1 : 1;
19907 /* 0:28 | 4 */ int a2 : 3;
19908 /* 0: 5 | 4 */ int a3 : 23;
19909 /* 3: 3 | 1 */ signed char a4 : 2;
19910 /* XXX 3-bit hole */
19911 /* XXX 4-byte hole */
19912 /* 8 | 8 */ int64_t a5;
19913 /* 16: 0 | 4 */ int a6 : 5;
19914 /* 16: 5 | 8 */ int64_t a7 : 3;
19915 /* XXX 7-byte padding */
19917 /* total size (bytes): 24 */
19921 Note how the offset information is now extended to also include the
19922 first bit of the bitfield.
19926 @item ptype[/@var{flags}] [@var{arg}]
19927 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19928 detailed description of the type, instead of just the name of the type.
19929 @xref{Expressions, ,Expressions}.
19931 Contrary to @code{whatis}, @code{ptype} always unrolls any
19932 @code{typedef}s in its argument declaration, whether the argument is
19933 a variable, expression, or a data type. This means that @code{ptype}
19934 of a variable or an expression will not print literally its type as
19935 present in the source code---use @code{whatis} for that. @code{typedef}s at
19936 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19937 fields, methods and inner @code{class typedef}s of @code{struct}s,
19938 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19940 For example, for this variable declaration:
19943 typedef double real_t;
19944 struct complex @{ real_t real; double imag; @};
19945 typedef struct complex complex_t;
19947 real_t *real_pointer_var;
19951 the two commands give this output:
19955 (@value{GDBP}) whatis var
19957 (@value{GDBP}) ptype var
19958 type = struct complex @{
19962 (@value{GDBP}) whatis complex_t
19963 type = struct complex
19964 (@value{GDBP}) whatis struct complex
19965 type = struct complex
19966 (@value{GDBP}) ptype struct complex
19967 type = struct complex @{
19971 (@value{GDBP}) whatis real_pointer_var
19973 (@value{GDBP}) ptype real_pointer_var
19979 As with @code{whatis}, using @code{ptype} without an argument refers to
19980 the type of @code{$}, the last value in the value history.
19982 @cindex incomplete type
19983 Sometimes, programs use opaque data types or incomplete specifications
19984 of complex data structure. If the debug information included in the
19985 program does not allow @value{GDBN} to display a full declaration of
19986 the data type, it will say @samp{<incomplete type>}. For example,
19987 given these declarations:
19991 struct foo *fooptr;
19995 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19998 (@value{GDBP}) ptype foo
19999 $1 = <incomplete type>
20003 ``Incomplete type'' is C terminology for data types that are not
20004 completely specified.
20006 @cindex unknown type
20007 Othertimes, information about a variable's type is completely absent
20008 from the debug information included in the program. This most often
20009 happens when the program or library where the variable is defined
20010 includes no debug information at all. @value{GDBN} knows the variable
20011 exists from inspecting the linker/loader symbol table (e.g., the ELF
20012 dynamic symbol table), but such symbols do not contain type
20013 information. Inspecting the type of a (global) variable for which
20014 @value{GDBN} has no type information shows:
20017 (@value{GDBP}) ptype var
20018 type = <data variable, no debug info>
20021 @xref{Variables, no debug info variables}, for how to print the values
20025 @item info types [-q] [@var{regexp}]
20026 Print a brief description of all types whose names match the regular
20027 expression @var{regexp} (or all types in your program, if you supply
20028 no argument). Each complete typename is matched as though it were a
20029 complete line; thus, @samp{i type value} gives information on all
20030 types in your program whose names include the string @code{value}, but
20031 @samp{i type ^value$} gives information only on types whose complete
20032 name is @code{value}.
20034 In programs using different languages, @value{GDBN} chooses the syntax
20035 to print the type description according to the
20036 @samp{set language} value: using @samp{set language auto}
20037 (see @ref{Automatically, ,Set Language Automatically}) means to use the
20038 language of the type, other values mean to use
20039 the manually specified language (see @ref{Manually, ,Set Language Manually}).
20041 This command differs from @code{ptype} in two ways: first, like
20042 @code{whatis}, it does not print a detailed description; second, it
20043 lists all source files and line numbers where a type is defined.
20045 The output from @samp{into types} is proceeded with a header line
20046 describing what types are being listed. The optional flag @samp{-q},
20047 which stands for @samp{quiet}, disables printing this header
20050 @kindex info type-printers
20051 @item info type-printers
20052 Versions of @value{GDBN} that ship with Python scripting enabled may
20053 have ``type printers'' available. When using @command{ptype} or
20054 @command{whatis}, these printers are consulted when the name of a type
20055 is needed. @xref{Type Printing API}, for more information on writing
20058 @code{info type-printers} displays all the available type printers.
20060 @kindex enable type-printer
20061 @kindex disable type-printer
20062 @item enable type-printer @var{name}@dots{}
20063 @item disable type-printer @var{name}@dots{}
20064 These commands can be used to enable or disable type printers.
20067 @cindex local variables
20068 @item info scope @var{locspec}
20069 List all the variables local to the lexical scope of the code location
20070 that results from resolving @var{locspec}. @xref{Location
20071 Specifications}, for details about supported forms of @var{locspec}.
20075 (@value{GDBP}) @b{info scope command_line_handler}
20076 Scope for command_line_handler:
20077 Symbol rl is an argument at stack/frame offset 8, length 4.
20078 Symbol linebuffer is in static storage at address 0x150a18, length 4.
20079 Symbol linelength is in static storage at address 0x150a1c, length 4.
20080 Symbol p is a local variable in register $esi, length 4.
20081 Symbol p1 is a local variable in register $ebx, length 4.
20082 Symbol nline is a local variable in register $edx, length 4.
20083 Symbol repeat is a local variable at frame offset -8, length 4.
20087 This command is especially useful for determining what data to collect
20088 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
20091 @kindex info source
20093 Show information about the current source file---that is, the source file for
20094 the function containing the current point of execution:
20097 the name of the source file, and the directory containing it,
20099 the directory it was compiled in,
20101 its length, in lines,
20103 which programming language it is written in,
20105 if the debug information provides it, the program that compiled the file
20106 (which may include, e.g., the compiler version and command line arguments),
20108 whether the executable includes debugging information for that file, and
20109 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
20111 whether the debugging information includes information about
20112 preprocessor macros.
20116 @kindex info sources
20117 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
20120 With no options @samp{info sources} prints the names of all source
20121 files in your program for which there is debugging information. The
20122 source files are presented based on a list of object files
20123 (executables and libraries) currently loaded into @value{GDBN}. For
20124 each object file all of the associated source files are listed.
20126 Each source file will only be printed once for each object file, but a
20127 single source file can be repeated in the output if it is part of
20128 multiple object files.
20130 If the optional @var{regexp} is provided, then only source files that
20131 match the regular expression will be printed. The matching is
20132 case-sensitive, except on operating systems that have case-insensitive
20133 filesystem (e.g., MS-Windows). @samp{--} can be used before
20134 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
20135 command option (e.g. if @var{regexp} starts with @samp{-}).
20137 By default, the @var{regexp} is used to match anywhere in the
20138 filename. If @code{-dirname}, only files having a dirname matching
20139 @var{regexp} are shown. If @code{-basename}, only files having a
20140 basename matching @var{regexp} are shown.
20142 It is possible that an object file may be printed in the list with no
20143 associated source files. This can happen when either no source files
20144 match @var{regexp}, or, the object file was compiled without debug
20145 information and so @value{GDBN} is unable to find any source file
20148 @kindex info functions
20149 @item info functions [-q] [-n]
20150 Print the names and data types of all defined functions.
20151 Similarly to @samp{info types}, this command groups its output by source
20152 files and annotates each function definition with its source line
20155 In programs using different languages, @value{GDBN} chooses the syntax
20156 to print the function name and type according to the
20157 @samp{set language} value: using @samp{set language auto}
20158 (see @ref{Automatically, ,Set Language Automatically}) means to use the
20159 language of the function, other values mean to use
20160 the manually specified language (see @ref{Manually, ,Set Language Manually}).
20162 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
20163 results. A non-debugging symbol is a symbol that comes from the
20164 executable's symbol table, not from the debug information (for
20165 example, DWARF) associated with the executable.
20167 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20168 printing header information and messages explaining why no functions
20171 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
20172 Like @samp{info functions}, but only print the names and data types
20173 of the functions selected with the provided regexp(s).
20175 If @var{regexp} is provided, print only the functions whose names
20176 match the regular expression @var{regexp}.
20177 Thus, @samp{info fun step} finds all functions whose
20178 names include @code{step}; @samp{info fun ^step} finds those whose names
20179 start with @code{step}. If a function name contains characters that
20180 conflict with the regular expression language (e.g.@:
20181 @samp{operator*()}), they may be quoted with a backslash.
20183 If @var{type_regexp} is provided, print only the functions whose
20184 types, as printed by the @code{whatis} command, match
20185 the regular expression @var{type_regexp}.
20186 If @var{type_regexp} contains space(s), it should be enclosed in
20187 quote characters. If needed, use backslash to escape the meaning
20188 of special characters or quotes.
20189 Thus, @samp{info fun -t '^int ('} finds the functions that return
20190 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
20191 have an argument type containing int; @samp{info fun -t '^int (' ^step}
20192 finds the functions whose names start with @code{step} and that return
20195 If both @var{regexp} and @var{type_regexp} are provided, a function
20196 is printed only if its name matches @var{regexp} and its type matches
20200 @kindex info variables
20201 @item info variables [-q] [-n]
20202 Print the names and data types of all variables that are defined
20203 outside of functions (i.e.@: excluding local variables).
20204 The printed variables are grouped by source files and annotated with
20205 their respective source line numbers.
20207 In programs using different languages, @value{GDBN} chooses the syntax
20208 to print the variable name and type according to the
20209 @samp{set language} value: using @samp{set language auto}
20210 (see @ref{Automatically, ,Set Language Automatically}) means to use the
20211 language of the variable, other values mean to use
20212 the manually specified language (see @ref{Manually, ,Set Language Manually}).
20214 The @samp{-n} flag excludes non-debugging symbols from the results.
20216 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20217 printing header information and messages explaining why no variables
20220 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
20221 Like @kbd{info variables}, but only print the variables selected
20222 with the provided regexp(s).
20224 If @var{regexp} is provided, print only the variables whose names
20225 match the regular expression @var{regexp}.
20227 If @var{type_regexp} is provided, print only the variables whose
20228 types, as printed by the @code{whatis} command, match
20229 the regular expression @var{type_regexp}.
20230 If @var{type_regexp} contains space(s), it should be enclosed in
20231 quote characters. If needed, use backslash to escape the meaning
20232 of special characters or quotes.
20234 If both @var{regexp} and @var{type_regexp} are provided, an argument
20235 is printed only if its name matches @var{regexp} and its type matches
20238 @kindex info modules
20240 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
20241 List all Fortran modules in the program, or all modules matching the
20242 optional regular expression @var{regexp}.
20244 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20245 printing header information and messages explaining why no modules
20248 @kindex info module
20249 @cindex Fortran modules, information about
20250 @cindex functions and variables by Fortran module
20251 @cindex module functions and variables
20252 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20253 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20254 List all functions or variables within all Fortran modules. The set
20255 of functions or variables listed can be limited by providing some or
20256 all of the optional regular expressions. If @var{module-regexp} is
20257 provided, then only Fortran modules matching @var{module-regexp} will
20258 be searched. Only functions or variables whose type matches the
20259 optional regular expression @var{type-regexp} will be listed. And
20260 only functions or variables whose name matches the optional regular
20261 expression @var{regexp} will be listed.
20263 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20264 printing header information and messages explaining why no functions
20265 or variables have been printed.
20269 Print the name of the starting function of the program. This serves
20270 primarily Fortran programs, which have a user-supplied name for the
20273 @kindex info classes
20274 @cindex Objective-C, classes and selectors
20276 @itemx info classes @var{regexp}
20277 Display all Objective-C classes in your program, or
20278 (with the @var{regexp} argument) all those matching a particular regular
20281 @kindex info selectors
20282 @item info selectors
20283 @itemx info selectors @var{regexp}
20284 Display all Objective-C selectors in your program, or
20285 (with the @var{regexp} argument) all those matching a particular regular
20289 This was never implemented.
20290 @kindex info methods
20292 @itemx info methods @var{regexp}
20293 The @code{info methods} command permits the user to examine all defined
20294 methods within C@t{++} program, or (with the @var{regexp} argument) a
20295 specific set of methods found in the various C@t{++} classes. Many
20296 C@t{++} classes provide a large number of methods. Thus, the output
20297 from the @code{ptype} command can be overwhelming and hard to use. The
20298 @code{info-methods} command filters the methods, printing only those
20299 which match the regular-expression @var{regexp}.
20302 @cindex opaque data types
20303 @kindex set opaque-type-resolution
20304 @item set opaque-type-resolution on
20305 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
20306 declared as a pointer to a @code{struct}, @code{class}, or
20307 @code{union}---for example, @code{struct MyType *}---that is used in one
20308 source file although the full declaration of @code{struct MyType} is in
20309 another source file. The default is on.
20311 A change in the setting of this subcommand will not take effect until
20312 the next time symbols for a file are loaded.
20314 @item set opaque-type-resolution off
20315 Tell @value{GDBN} not to resolve opaque types. In this case, the type
20316 is printed as follows:
20318 @{<no data fields>@}
20321 @kindex show opaque-type-resolution
20322 @item show opaque-type-resolution
20323 Show whether opaque types are resolved or not.
20325 @kindex set print symbol-loading
20326 @cindex print messages when symbols are loaded
20327 @item set print symbol-loading
20328 @itemx set print symbol-loading full
20329 @itemx set print symbol-loading brief
20330 @itemx set print symbol-loading off
20331 The @code{set print symbol-loading} command allows you to control the
20332 printing of messages when @value{GDBN} loads symbol information.
20333 By default a message is printed for the executable and one for each
20334 shared library, and normally this is what you want. However, when
20335 debugging apps with large numbers of shared libraries these messages
20337 When set to @code{brief} a message is printed for each executable,
20338 and when @value{GDBN} loads a collection of shared libraries at once
20339 it will only print one message regardless of the number of shared
20340 libraries. When set to @code{off} no messages are printed.
20342 @kindex show print symbol-loading
20343 @item show print symbol-loading
20344 Show whether messages will be printed when a @value{GDBN} command
20345 entered from the keyboard causes symbol information to be loaded.
20347 @kindex maint print symbols
20348 @cindex symbol dump
20349 @kindex maint print psymbols
20350 @cindex partial symbol dump
20351 @kindex maint print msymbols
20352 @cindex minimal symbol dump
20353 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
20354 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20355 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20356 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20357 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20358 Write a dump of debugging symbol data into the file @var{filename} or
20359 the terminal if @var{filename} is unspecified.
20360 If @code{-objfile @var{objfile}} is specified, only dump symbols for
20362 If @code{-pc @var{address}} is specified, only dump symbols for the file
20363 with code at that address. Note that @var{address} may be a symbol like
20365 If @code{-source @var{source}} is specified, only dump symbols for that
20368 These commands are used to debug the @value{GDBN} symbol-reading code.
20369 These commands do not modify internal @value{GDBN} state, therefore
20370 @samp{maint print symbols} will only print symbols for already expanded symbol
20372 You can use the command @code{info sources} to find out which files these are.
20373 If you use @samp{maint print psymbols} instead, the dump shows information
20374 about symbols that @value{GDBN} only knows partially---that is, symbols
20375 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20376 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20379 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20380 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20382 @kindex maint info symtabs
20383 @kindex maint info psymtabs
20384 @cindex listing @value{GDBN}'s internal symbol tables
20385 @cindex symbol tables, listing @value{GDBN}'s internal
20386 @cindex full symbol tables, listing @value{GDBN}'s internal
20387 @cindex partial symbol tables, listing @value{GDBN}'s internal
20388 @item maint info symtabs @r{[} @var{regexp} @r{]}
20389 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20391 List the @code{struct symtab} or @code{struct partial_symtab}
20392 structures whose names match @var{regexp}. If @var{regexp} is not
20393 given, list them all. The output includes expressions which you can
20394 copy into a @value{GDBN} debugging this one to examine a particular
20395 structure in more detail. For example:
20398 (@value{GDBP}) maint info psymtabs dwarf2read
20399 @{ objfile /home/gnu/build/gdb/gdb
20400 ((struct objfile *) 0x82e69d0)
20401 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20402 ((struct partial_symtab *) 0x8474b10)
20405 text addresses 0x814d3c8 -- 0x8158074
20406 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20407 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20408 dependencies (none)
20411 (@value{GDBP}) maint info symtabs
20415 We see that there is one partial symbol table whose filename contains
20416 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20417 and we see that @value{GDBN} has not read in any symtabs yet at all.
20418 If we set a breakpoint on a function, that will cause @value{GDBN} to
20419 read the symtab for the compilation unit containing that function:
20422 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20423 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20425 (@value{GDBP}) maint info symtabs
20426 @{ objfile /home/gnu/build/gdb/gdb
20427 ((struct objfile *) 0x82e69d0)
20428 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20429 ((struct symtab *) 0x86c1f38)
20432 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20433 linetable ((struct linetable *) 0x8370fa0)
20434 debugformat DWARF 2
20440 @kindex maint info line-table
20441 @cindex listing @value{GDBN}'s internal line tables
20442 @cindex line tables, listing @value{GDBN}'s internal
20443 @item maint info line-table @r{[} @var{regexp} @r{]}
20445 List the @code{struct linetable} from all @code{struct symtab}
20446 instances whose name matches @var{regexp}. If @var{regexp} is not
20447 given, list the @code{struct linetable} from all @code{struct symtab}.
20451 (@value{GDBP}) maint info line-table
20452 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20453 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20454 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20455 linetable: ((struct linetable *) 0x62100012b760):
20456 INDEX LINE ADDRESS IS-STMT PROLOGUE-END EPILOGUE-BEGIN
20457 0 3 0x0000000000401110 Y
20458 1 4 0x0000000000401114 Y Y Y
20459 2 9 0x0000000000401120 Y
20460 3 10 0x0000000000401124 Y Y
20461 4 10 0x0000000000401129 Y Y
20462 5 15 0x0000000000401130 Y
20463 6 16 0x0000000000401134 Y Y
20464 7 16 0x0000000000401139
20465 8 21 0x0000000000401140 Y Y
20466 9 22 0x000000000040114f Y Y
20467 10 22 0x0000000000401154 Y
20468 11 END 0x000000000040115a Y
20471 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20472 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20473 indicates that a given address is an adequate place to set a breakpoint at the
20474 first instruction following a function prologue. The @samp{EPILOGUE-BEGIN}
20475 column indicates that a given address marks the point where a block's frame is
20476 destroyed, making local variables hard or impossible to find.
20478 @kindex set always-read-ctf [on|off]
20479 @kindex show always-read-ctf
20480 @cindex always-read-ctf
20481 @cindex CTF info, when to read
20482 @item set always-read-ctf [on|off]
20483 @itemx show always-read-ctf
20485 When off, CTF debug info is only read if DWARF debug info is not
20486 present. When on, CTF debug info is read regardless of whether DWARF
20487 debug info is present. The default value is off.
20489 @kindex maint set symbol-cache-size
20490 @cindex symbol cache size
20491 @item maint set symbol-cache-size @var{size}
20492 Set the size of the symbol cache to @var{size}.
20493 The default size is intended to be good enough for debugging
20494 most applications. This option exists to allow for experimenting
20495 with different sizes.
20497 @kindex maint show symbol-cache-size
20498 @item maint show symbol-cache-size
20499 Show the size of the symbol cache.
20501 @kindex maint print symbol-cache
20502 @cindex symbol cache, printing its contents
20503 @item maint print symbol-cache
20504 Print the contents of the symbol cache.
20505 This is useful when debugging symbol cache issues.
20507 @kindex maint print symbol-cache-statistics
20508 @cindex symbol cache, printing usage statistics
20509 @item maint print symbol-cache-statistics
20510 Print symbol cache usage statistics.
20511 This helps determine how well the cache is being utilized.
20513 @kindex maint flush symbol-cache
20514 @kindex maint flush-symbol-cache
20515 @cindex symbol cache, flushing
20516 @item maint flush symbol-cache
20517 @itemx maint flush-symbol-cache
20518 Flush the contents of the symbol cache, all entries are removed. This
20519 command is useful when debugging the symbol cache. It is also useful
20520 when collecting performance data. The command @code{maint
20521 flush-symbol-cache} is deprecated in favor of @code{maint flush
20524 @kindex maint set ignore-prologue-end-flag
20525 @cindex prologue-end
20526 @item maint set ignore-prologue-end-flag [on|off]
20527 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20528 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20529 to place breakpoints past the end of a function prologue. When @samp{on},
20530 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20533 @kindex maint show ignore-prologue-end-flag
20534 @item maint show ignore-prologue-end-flag
20535 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20540 @chapter Altering Execution
20542 Once you think you have found an error in your program, you might want to
20543 find out for certain whether correcting the apparent error would lead to
20544 correct results in the rest of the run. You can find the answer by
20545 experiment, using the @value{GDBN} features for altering execution of the
20548 For example, you can store new values into variables or memory
20549 locations, give your program a signal, restart it at a different
20550 address, or even return prematurely from a function.
20553 * Assignment:: Assignment to variables
20554 * Jumping:: Continuing at a different address
20555 * Signaling:: Giving your program a signal
20556 * Returning:: Returning from a function
20557 * Calling:: Calling your program's functions
20558 * Patching:: Patching your program
20559 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20563 @section Assignment to Variables
20566 @cindex setting variables
20567 To alter the value of a variable, evaluate an assignment expression.
20568 @xref{Expressions, ,Expressions}. For example,
20575 stores the value 4 into the variable @code{x}, and then prints the
20576 value of the assignment expression (which is 4).
20577 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20578 information on operators in supported languages.
20580 @kindex set variable
20581 @cindex variables, setting
20582 If you are not interested in seeing the value of the assignment, use the
20583 @code{set} command instead of the @code{print} command. @code{set} is
20584 really the same as @code{print} except that the expression's value is
20585 not printed and is not put in the value history (@pxref{Value History,
20586 ,Value History}). The expression is evaluated only for its effects.
20588 If the beginning of the argument string of the @code{set} command
20589 appears identical to a @code{set} subcommand, use the @code{set
20590 variable} command instead of just @code{set}. This command is identical
20591 to @code{set} except for its lack of subcommands. For example, if your
20592 program has a variable @code{width}, you get an error if you try to set
20593 a new value with just @samp{set width=13}, because @value{GDBN} has the
20594 command @code{set width}:
20597 (@value{GDBP}) whatis width
20599 (@value{GDBP}) p width
20601 (@value{GDBP}) set width=47
20602 Invalid syntax in expression.
20606 The invalid expression, of course, is @samp{=47}. In
20607 order to actually set the program's variable @code{width}, use
20610 (@value{GDBP}) set var width=47
20613 Because the @code{set} command has many subcommands that can conflict
20614 with the names of program variables, it is a good idea to use the
20615 @code{set variable} command instead of just @code{set}. For example, if
20616 your program has a variable @code{g}, you run into problems if you try
20617 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20618 the command @code{set gnutarget}, abbreviated @code{set g}:
20622 (@value{GDBP}) whatis g
20626 (@value{GDBP}) set g=4
20630 The program being debugged has been started already.
20631 Start it from the beginning? (y or n) y
20632 Starting program: /home/smith/cc_progs/a.out
20633 "/home/smith/cc_progs/a.out": can't open to read symbols:
20634 Invalid bfd target.
20635 (@value{GDBP}) show g
20636 The current BFD target is "=4".
20641 The program variable @code{g} did not change, and you silently set the
20642 @code{gnutarget} to an invalid value. In order to set the variable
20646 (@value{GDBP}) set var g=4
20649 @value{GDBN} allows more implicit conversions in assignments than C; you can
20650 freely store an integer value into a pointer variable or vice versa,
20651 and you can convert any structure to any other structure that is the
20652 same length or shorter.
20653 @comment FIXME: how do structs align/pad in these conversions?
20654 @comment /doc@cygnus.com 18dec1990
20656 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20657 construct to generate a value of specified type at a specified address
20658 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20659 to memory location @code{0x83040} as an integer (which implies a certain size
20660 and representation in memory), and
20663 set @{int@}0x83040 = 4
20667 stores the value 4 into that memory location.
20670 @section Continuing at a Different Address
20672 Ordinarily, when you continue your program, you do so at the place where
20673 it stopped, with the @code{continue} command. You can instead continue at
20674 an address of your own choosing, with the following commands:
20678 @kindex j @r{(@code{jump})}
20679 @item jump @var{locspec}
20680 @itemx j @var{locspec}
20681 Resume execution at the address of the code location that results from
20682 resolving @var{locspec}.
20683 @xref{Location Specifications}, for a description of the different
20684 forms of @var{locspec}. If @var{locspec} resolves to more than one address,
20685 those outside the current compilation unit are ignored. If considering just
20686 the addresses in the current compilation unit still doesn't yield a unique
20687 address, the command aborts before jumping.
20688 Execution stops again immediately if there is a breakpoint there. It
20689 is common practice to use the @code{tbreak} command in conjunction
20690 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20692 The @code{jump} command does not change the current stack frame, or
20693 the stack pointer, or the contents of any memory location or any
20694 register other than the program counter. If @var{locspec} resolves to
20695 an address in a different function from the one currently executing, the
20696 results may be bizarre if the two functions expect different patterns
20697 of arguments or of local variables. For this reason, the @code{jump}
20698 command requests confirmation if the jump address is not in the
20699 function currently executing. However, even bizarre results are
20700 predictable if you are well acquainted with the machine-language code
20704 On many systems, you can get much the same effect as the @code{jump}
20705 command by storing a new value into the register @code{$pc}. The
20706 difference is that this does not start your program running; it only
20707 changes the address of where it @emph{will} run when you continue. For
20715 makes the next @code{continue} command or stepping command execute at
20716 address @code{0x485}, rather than at the address where your program stopped.
20717 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20719 However, writing directly to @code{$pc} will only change the value of
20720 the program-counter register, while using @code{jump} will ensure that
20721 any additional auxiliary state is also updated. For example, on
20722 SPARC, @code{jump} will update both @code{$pc} and @code{$npc}
20723 registers prior to resuming execution. When using the approach of
20724 writing directly to @code{$pc} it is your job to also update the
20725 @code{$npc} register.
20727 The most common occasion to use the @code{jump} command is to back
20728 up---perhaps with more breakpoints set---over a portion of a program
20729 that has already executed, in order to examine its execution in more
20734 @section Giving your Program a Signal
20735 @cindex deliver a signal to a program
20739 @item signal @var{signal}
20740 Resume execution where your program is stopped, but immediately give it the
20741 signal @var{signal}. The @var{signal} can be the name or the number of a
20742 signal. For example, on many systems @code{signal 2} and @code{signal
20743 SIGINT} are both ways of sending an interrupt signal.
20745 Alternatively, if @var{signal} is zero, continue execution without
20746 giving a signal. This is useful when your program stopped on account of
20747 a signal and would ordinarily see the signal when resumed with the
20748 @code{continue} command; @samp{signal 0} causes it to resume without a
20751 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20752 delivered to the currently selected thread, not the thread that last
20753 reported a stop. This includes the situation where a thread was
20754 stopped due to a signal. So if you want to continue execution
20755 suppressing the signal that stopped a thread, you should select that
20756 same thread before issuing the @samp{signal 0} command. If you issue
20757 the @samp{signal 0} command with another thread as the selected one,
20758 @value{GDBN} detects that and asks for confirmation.
20760 Invoking the @code{signal} command is not the same as invoking the
20761 @code{kill} utility from the shell. Sending a signal with @code{kill}
20762 causes @value{GDBN} to decide what to do with the signal depending on
20763 the signal handling tables (@pxref{Signals}). The @code{signal} command
20764 passes the signal directly to your program.
20766 @code{signal} does not repeat when you press @key{RET} a second time
20767 after executing the command.
20769 @kindex queue-signal
20770 @item queue-signal @var{signal}
20771 Queue @var{signal} to be delivered immediately to the current thread
20772 when execution of the thread resumes. The @var{signal} can be the name or
20773 the number of a signal. For example, on many systems @code{signal 2} and
20774 @code{signal SIGINT} are both ways of sending an interrupt signal.
20775 The handling of the signal must be set to pass the signal to the program,
20776 otherwise @value{GDBN} will report an error.
20777 You can control the handling of signals from @value{GDBN} with the
20778 @code{handle} command (@pxref{Signals}).
20780 Alternatively, if @var{signal} is zero, any currently queued signal
20781 for the current thread is discarded and when execution resumes no signal
20782 will be delivered. This is useful when your program stopped on account
20783 of a signal and would ordinarily see the signal when resumed with the
20784 @code{continue} command.
20786 This command differs from the @code{signal} command in that the signal
20787 is just queued, execution is not resumed. And @code{queue-signal} cannot
20788 be used to pass a signal whose handling state has been set to @code{nopass}
20793 @xref{stepping into signal handlers}, for information on how stepping
20794 commands behave when the thread has a signal queued.
20797 @section Returning from a Function
20800 @cindex returning from a function
20803 @itemx return @var{expression}
20804 You can cancel execution of a function call with the @code{return}
20805 command. If you give an
20806 @var{expression} argument, its value is used as the function's return
20810 When you use @code{return}, @value{GDBN} discards the selected stack frame
20811 (and all frames within it). You can think of this as making the
20812 discarded frame return prematurely. If you wish to specify a value to
20813 be returned, give that value as the argument to @code{return}.
20815 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20816 Frame}), and any other frames inside of it, leaving its caller as the
20817 innermost remaining frame. That frame becomes selected. The
20818 specified value is stored in the registers used for returning values
20821 The @code{return} command does not resume execution; it leaves the
20822 program stopped in the state that would exist if the function had just
20823 returned. In contrast, the @code{finish} command (@pxref{Continuing
20824 and Stepping, ,Continuing and Stepping}) resumes execution until the
20825 selected stack frame returns naturally.
20827 @value{GDBN} needs to know how the @var{expression} argument should be set for
20828 the inferior. The concrete registers assignment depends on the OS ABI and the
20829 type being returned by the selected stack frame. For example it is common for
20830 OS ABI to return floating point values in FPU registers while integer values in
20831 CPU registers. Still some ABIs return even floating point values in CPU
20832 registers. Larger integer widths (such as @code{long long int}) also have
20833 specific placement rules. @value{GDBN} already knows the OS ABI from its
20834 current target so it needs to find out also the type being returned to make the
20835 assignment into the right register(s).
20837 Normally, the selected stack frame has debug info. @value{GDBN} will always
20838 use the debug info instead of the implicit type of @var{expression} when the
20839 debug info is available. For example, if you type @kbd{return -1}, and the
20840 function in the current stack frame is declared to return a @code{long long
20841 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20842 into a @code{long long int}:
20845 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20847 (@value{GDBP}) return -1
20848 Make func return now? (y or n) y
20849 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20850 43 printf ("result=%lld\n", func ());
20854 However, if the selected stack frame does not have a debug info, e.g., if the
20855 function was compiled without debug info, @value{GDBN} has to find out the type
20856 to return from user. Specifying a different type by mistake may set the value
20857 in different inferior registers than the caller code expects. For example,
20858 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20859 of a @code{long long int} result for a debug info less function (on 32-bit
20860 architectures). Therefore the user is required to specify the return type by
20861 an appropriate cast explicitly:
20864 Breakpoint 2, 0x0040050b in func ()
20865 (@value{GDBP}) return -1
20866 Return value type not available for selected stack frame.
20867 Please use an explicit cast of the value to return.
20868 (@value{GDBP}) return (long long int) -1
20869 Make selected stack frame return now? (y or n) y
20870 #0 0x00400526 in main ()
20875 @section Calling Program Functions
20878 @cindex calling functions
20879 @cindex inferior functions, calling
20880 @item print @var{expr}
20881 Evaluate the expression @var{expr} and display the resulting value.
20882 The expression may include calls to functions in the program being
20886 @item call @var{expr}
20887 Evaluate the expression @var{expr} without displaying @code{void}
20890 You can use this variant of the @code{print} command if you want to
20891 execute a function from your program that does not return anything
20892 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20893 with @code{void} returned values that @value{GDBN} will otherwise
20894 print. If the result is not void, it is printed and saved in the
20898 It is possible for the function you call via the @code{print} or
20899 @code{call} command to generate a signal (e.g., if there's a bug in
20900 the function, or if you passed it incorrect arguments). What happens
20901 in that case is controlled by the @code{set unwindonsignal} command.
20903 Similarly, with a C@t{++} program it is possible for the function you
20904 call via the @code{print} or @code{call} command to generate an
20905 exception that is not handled due to the constraints of the dummy
20906 frame. In this case, any exception that is raised in the frame, but has
20907 an out-of-frame exception handler will not be found. GDB builds a
20908 dummy-frame for the inferior function call, and the unwinder cannot
20909 seek for exception handlers outside of this dummy-frame. What happens
20910 in that case is controlled by the
20911 @code{set unwind-on-terminating-exception} command.
20913 @anchor{stack unwind settings}
20915 @item set unwindonsignal
20916 @kindex set unwindonsignal
20917 @cindex unwind stack in called functions
20918 @cindex call dummy stack unwinding
20919 Set unwinding of the stack if a signal is received while in a function
20920 that @value{GDBN} called in the program being debugged. If set to on,
20921 @value{GDBN} unwinds the stack it created for the call and restores
20922 the context to what it was before the call. If set to off (the
20923 default), @value{GDBN} stops in the frame where the signal was
20926 @item show unwindonsignal
20927 @kindex show unwindonsignal
20928 Show the current setting of stack unwinding in the functions called by
20931 @item set unwind-on-terminating-exception
20932 @kindex set unwind-on-terminating-exception
20933 @cindex unwind stack in called functions with unhandled exceptions
20934 @cindex call dummy stack unwinding on unhandled exception.
20935 Set unwinding of the stack if a C@t{++} exception is raised, but left
20936 unhandled while in a function that @value{GDBN} called in the program being
20937 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20938 it created for the call and restores the context to what it was before
20939 the call. If set to off, @value{GDBN} the exception is delivered to
20940 the default C@t{++} exception handler and the inferior terminated.
20942 @item show unwind-on-terminating-exception
20943 @kindex show unwind-on-terminating-exception
20944 Show the current setting of stack unwinding in the functions called by
20947 @item set may-call-functions
20948 @kindex set may-call-functions
20949 @cindex disabling calling functions in the program
20950 @cindex calling functions in the program, disabling
20951 Set permission to call functions in the program.
20952 This controls whether @value{GDBN} will attempt to call functions in
20953 the program, such as with expressions in the @code{print} command. It
20954 defaults to @code{on}.
20956 To call a function in the program, @value{GDBN} has to temporarily
20957 modify the state of the inferior. This has potentially undesired side
20958 effects. Also, having @value{GDBN} call nested functions is likely to
20959 be erroneous and may even crash the program being debugged. You can
20960 avoid such hazards by forbidding @value{GDBN} from calling functions
20961 in the program being debugged. If calling functions in the program
20962 is forbidden, GDB will throw an error when a command (such as printing
20963 an expression) starts a function call in the program.
20965 @item show may-call-functions
20966 @kindex show may-call-functions
20967 Show permission to call functions in the program.
20971 When calling a function within a program, it is possible that the
20972 program could enter a state from which the called function may never
20973 return. If this happens then it is possible to interrupt the function
20974 call by typing the interrupt character (often @kbd{Ctrl-c}).
20976 If a called function is interrupted for any reason, including hitting
20977 a breakpoint, or triggering a watchpoint, and the stack is not unwound
20978 due to @code{set unwind-on-terminating-exception on} or @code{set
20979 unwindonsignal on} (@pxref{stack unwind settings}),
20980 then the dummy-frame, created by @value{GDBN} to facilitate the call
20981 to the program function, will be visible in the backtrace, for example
20982 frame @code{#3} in the following backtrace:
20985 (@value{GDBP}) backtrace
20986 #0 0x00007ffff7b3d1e7 in nanosleep () from /lib64/libc.so.6
20987 #1 0x00007ffff7b3d11e in sleep () from /lib64/libc.so.6
20988 #2 0x000000000040113f in deadlock () at test.cc:13
20989 #3 <function called from gdb>
20990 #4 breakpt () at test.cc:20
20991 #5 0x0000000000401151 in main () at test.cc:25
20994 At this point it is possible to examine the state of the inferior just
20995 like any other stop.
20997 Depending on why the function was interrupted then it may be possible
20998 to resume the inferior (using commands like @code{continue},
20999 @code{step}, etc). In this case, when the inferior finally returns to
21000 the dummy-frame, @value{GDBN} will once again halt the inferior.
21002 @subsection Calling functions with no debug info
21004 @cindex no debug info functions
21005 Sometimes, a function you wish to call is missing debug information.
21006 In such case, @value{GDBN} does not know the type of the function,
21007 including the types of the function's parameters. To avoid calling
21008 the inferior function incorrectly, which could result in the called
21009 function functioning erroneously and even crash, @value{GDBN} refuses
21010 to call the function unless you tell it the type of the function.
21012 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
21013 to do that. The simplest is to cast the call to the function's
21014 declared return type. For example:
21017 (@value{GDBP}) p getenv ("PATH")
21018 'getenv' has unknown return type; cast the call to its declared return type
21019 (@value{GDBP}) p (char *) getenv ("PATH")
21020 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
21023 Casting the return type of a no-debug function is equivalent to
21024 casting the function to a pointer to a prototyped function that has a
21025 prototype that matches the types of the passed-in arguments, and
21026 calling that. I.e., the call above is equivalent to:
21029 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
21033 and given this prototyped C or C++ function with float parameters:
21036 float multiply (float v1, float v2) @{ return v1 * v2; @}
21040 these calls are equivalent:
21043 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
21044 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
21047 If the function you wish to call is declared as unprototyped (i.e.@:
21048 old K&R style), you must use the cast-to-function-pointer syntax, so
21049 that @value{GDBN} knows that it needs to apply default argument
21050 promotions (promote float arguments to double). @xref{ABI, float
21051 promotion}. For example, given this unprototyped C function with
21052 float parameters, and no debug info:
21056 multiply_noproto (v1, v2)
21064 you call it like this:
21067 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
21071 @section Patching Programs
21073 @cindex patching binaries
21074 @cindex writing into executables
21075 @cindex writing into corefiles
21077 By default, @value{GDBN} opens the file containing your program's
21078 executable code (or the corefile) read-only. This prevents accidental
21079 alterations to machine code; but it also prevents you from intentionally
21080 patching your program's binary.
21082 If you'd like to be able to patch the binary, you can specify that
21083 explicitly with the @code{set write} command. For example, you might
21084 want to turn on internal debugging flags, or even to make emergency
21090 @itemx set write off
21091 If you specify @samp{set write on}, @value{GDBN} opens executable and
21092 core files for both reading and writing; if you specify @kbd{set write
21093 off} (the default), @value{GDBN} opens them read-only.
21095 If you have already loaded a file, you must load it again (using the
21096 @code{exec-file} or @code{core-file} command) after changing @code{set
21097 write}, for your new setting to take effect.
21101 Display whether executable files and core files are opened for writing
21102 as well as reading.
21105 @node Compiling and Injecting Code
21106 @section Compiling and injecting code in @value{GDBN}
21107 @cindex injecting code
21108 @cindex writing into executables
21109 @cindex compiling code
21111 @value{GDBN} supports on-demand compilation and code injection into
21112 programs running under @value{GDBN}. GCC 5.0 or higher built with
21113 @file{libcc1.so} must be installed for this functionality to be enabled.
21114 This functionality is implemented with the following commands.
21117 @kindex compile code
21118 @item compile code @var{source-code}
21119 @itemx compile code -raw @var{--} @var{source-code}
21120 Compile @var{source-code} with the compiler language found as the current
21121 language in @value{GDBN} (@pxref{Languages}). If compilation and
21122 injection is not supported with the current language specified in
21123 @value{GDBN}, or the compiler does not support this feature, an error
21124 message will be printed. If @var{source-code} compiles and links
21125 successfully, @value{GDBN} will load the object-code emitted,
21126 and execute it within the context of the currently selected inferior.
21127 It is important to note that the compiled code is executed immediately.
21128 After execution, the compiled code is removed from @value{GDBN} and any
21129 new types or variables you have defined will be deleted.
21131 The command allows you to specify @var{source-code} in two ways.
21132 The simplest method is to provide a single line of code to the command.
21136 compile code printf ("hello world\n");
21139 If you specify options on the command line as well as source code, they
21140 may conflict. The @samp{--} delimiter can be used to separate options
21141 from actual source code. E.g.:
21144 compile code -r -- printf ("hello world\n");
21147 Alternatively you can enter source code as multiple lines of text. To
21148 enter this mode, invoke the @samp{compile code} command without any text
21149 following the command. This will start the multiple-line editor and
21150 allow you to type as many lines of source code as required. When you
21151 have completed typing, enter @samp{end} on its own line to exit the
21156 >printf ("hello\n");
21157 >printf ("world\n");
21161 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
21162 provided @var{source-code} in a callable scope. In this case, you must
21163 specify the entry point of the code by defining a function named
21164 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
21165 inferior. Using @samp{-raw} option may be needed for example when
21166 @var{source-code} requires @samp{#include} lines which may conflict with
21167 inferior symbols otherwise.
21169 @kindex compile file
21170 @item compile file @var{filename}
21171 @itemx compile file -raw @var{filename}
21172 Like @code{compile code}, but take the source code from @var{filename}.
21175 compile file /home/user/example.c
21180 @item compile print [[@var{options}] --] @var{expr}
21181 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
21182 Compile and execute @var{expr} with the compiler language found as the
21183 current language in @value{GDBN} (@pxref{Languages}). By default the
21184 value of @var{expr} is printed in a format appropriate to its data type;
21185 you can choose a different format by specifying @samp{/@var{f}}, where
21186 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
21187 Formats}. The @code{compile print} command accepts the same options
21188 as the @code{print} command; see @ref{print options}.
21190 @item compile print [[@var{options}] --]
21191 @itemx compile print [[@var{options}] --] /@var{f}
21192 @cindex reprint the last value
21193 Alternatively you can enter the expression (source code producing it) as
21194 multiple lines of text. To enter this mode, invoke the @samp{compile print}
21195 command without any text following the command. This will start the
21196 multiple-line editor.
21200 The process of compiling and injecting the code can be inspected using:
21203 @anchor{set debug compile}
21204 @item set debug compile
21205 @cindex compile command debugging info
21206 Turns on or off display of @value{GDBN} process of compiling and
21207 injecting the code. The default is off.
21209 @item show debug compile
21210 Displays the current state of displaying @value{GDBN} process of
21211 compiling and injecting the code.
21213 @anchor{set debug compile-cplus-types}
21214 @item set debug compile-cplus-types
21215 @cindex compile C@t{++} type conversion
21216 Turns on or off the display of C@t{++} type conversion debugging information.
21217 The default is off.
21219 @item show debug compile-cplus-types
21220 Displays the current state of displaying debugging information for
21221 C@t{++} type conversion.
21224 @subsection Compilation options for the @code{compile} command
21226 @value{GDBN} needs to specify the right compilation options for the code
21227 to be injected, in part to make its ABI compatible with the inferior
21228 and in part to make the injected code compatible with @value{GDBN}'s
21232 The options used, in increasing precedence:
21235 @item target architecture and OS options (@code{gdbarch})
21236 These options depend on target processor type and target operating
21237 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
21238 (@code{-m64}) compilation option.
21240 @item compilation options recorded in the target
21241 @value{NGCC} (since version 4.7) stores the options used for compilation
21242 into @code{DW_AT_producer} part of DWARF debugging information according
21243 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
21244 explicitly specify @code{-g} during inferior compilation otherwise
21245 @value{NGCC} produces no DWARF. This feature is only relevant for
21246 platforms where @code{-g} produces DWARF by default, otherwise one may
21247 try to enforce DWARF by using @code{-gdwarf-4}.
21249 @item compilation options set by @code{set compile-args}
21253 You can override compilation options using the following command:
21256 @item set compile-args
21257 @cindex compile command options override
21258 Set compilation options used for compiling and injecting code with the
21259 @code{compile} commands. These options override any conflicting ones
21260 from the target architecture and/or options stored during inferior
21263 @item show compile-args
21264 Displays the current state of compilation options override.
21265 This does not show all the options actually used during compilation,
21266 use @ref{set debug compile} for that.
21269 @subsection Caveats when using the @code{compile} command
21271 There are a few caveats to keep in mind when using the @code{compile}
21272 command. As the caveats are different per language, the table below
21273 highlights specific issues on a per language basis.
21276 @item C code examples and caveats
21277 When the language in @value{GDBN} is set to @samp{C}, the compiler will
21278 attempt to compile the source code with a @samp{C} compiler. The source
21279 code provided to the @code{compile} command will have much the same
21280 access to variables and types as it normally would if it were part of
21281 the program currently being debugged in @value{GDBN}.
21283 Below is a sample program that forms the basis of the examples that
21284 follow. This program has been compiled and loaded into @value{GDBN},
21285 much like any other normal debugging session.
21288 void function1 (void)
21291 printf ("function 1\n");
21294 void function2 (void)
21309 For the purposes of the examples in this section, the program above has
21310 been compiled, loaded into @value{GDBN}, stopped at the function
21311 @code{main}, and @value{GDBN} is awaiting input from the user.
21313 To access variables and types for any program in @value{GDBN}, the
21314 program must be compiled and packaged with debug information. The
21315 @code{compile} command is not an exception to this rule. Without debug
21316 information, you can still use the @code{compile} command, but you will
21317 be very limited in what variables and types you can access.
21319 So with that in mind, the example above has been compiled with debug
21320 information enabled. The @code{compile} command will have access to
21321 all variables and types (except those that may have been optimized
21322 out). Currently, as @value{GDBN} has stopped the program in the
21323 @code{main} function, the @code{compile} command would have access to
21324 the variable @code{k}. You could invoke the @code{compile} command
21325 and type some source code to set the value of @code{k}. You can also
21326 read it, or do anything with that variable you would normally do in
21327 @code{C}. Be aware that changes to inferior variables in the
21328 @code{compile} command are persistent. In the following example:
21331 compile code k = 3;
21335 the variable @code{k} is now 3. It will retain that value until
21336 something else in the example program changes it, or another
21337 @code{compile} command changes it.
21339 Normal scope and access rules apply to source code compiled and
21340 injected by the @code{compile} command. In the example, the variables
21341 @code{j} and @code{k} are not accessible yet, because the program is
21342 currently stopped in the @code{main} function, where these variables
21343 are not in scope. Therefore, the following command
21346 compile code j = 3;
21350 will result in a compilation error message.
21352 Once the program is continued, execution will bring these variables in
21353 scope, and they will become accessible; then the code you specify via
21354 the @code{compile} command will be able to access them.
21356 You can create variables and types with the @code{compile} command as
21357 part of your source code. Variables and types that are created as part
21358 of the @code{compile} command are not visible to the rest of the program for
21359 the duration of its run. This example is valid:
21362 compile code int ff = 5; printf ("ff is %d\n", ff);
21365 However, if you were to type the following into @value{GDBN} after that
21366 command has completed:
21369 compile code printf ("ff is %d\n'', ff);
21373 a compiler error would be raised as the variable @code{ff} no longer
21374 exists. Object code generated and injected by the @code{compile}
21375 command is removed when its execution ends. Caution is advised
21376 when assigning to program variables values of variables created by the
21377 code submitted to the @code{compile} command. This example is valid:
21380 compile code int ff = 5; k = ff;
21383 The value of the variable @code{ff} is assigned to @code{k}. The variable
21384 @code{k} does not require the existence of @code{ff} to maintain the value
21385 it has been assigned. However, pointers require particular care in
21386 assignment. If the source code compiled with the @code{compile} command
21387 changed the address of a pointer in the example program, perhaps to a
21388 variable created in the @code{compile} command, that pointer would point
21389 to an invalid location when the command exits. The following example
21390 would likely cause issues with your debugged program:
21393 compile code int ff = 5; p = &ff;
21396 In this example, @code{p} would point to @code{ff} when the
21397 @code{compile} command is executing the source code provided to it.
21398 However, as variables in the (example) program persist with their
21399 assigned values, the variable @code{p} would point to an invalid
21400 location when the command exists. A general rule should be followed
21401 in that you should either assign @code{NULL} to any assigned pointers,
21402 or restore a valid location to the pointer before the command exits.
21404 Similar caution must be exercised with any structs, unions, and typedefs
21405 defined in @code{compile} command. Types defined in the @code{compile}
21406 command will no longer be available in the next @code{compile} command.
21407 Therefore, if you cast a variable to a type defined in the
21408 @code{compile} command, care must be taken to ensure that any future
21409 need to resolve the type can be achieved.
21412 (@value{GDBP}) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
21413 (@value{GDBP}) compile code printf ("%d\n", ((struct a *) argv)->a);
21414 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
21415 Compilation failed.
21416 (@value{GDBP}) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
21420 Variables that have been optimized away by the compiler are not
21421 accessible to the code submitted to the @code{compile} command.
21422 Access to those variables will generate a compiler error which @value{GDBN}
21423 will print to the console.
21426 @subsection Compiler search for the @code{compile} command
21428 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21429 which may not be obvious for remote targets of different architecture
21430 than where @value{GDBN} is running. Environment variable @env{PATH} on
21431 @value{GDBN} host is searched for @value{NGCC} binary matching the
21432 target architecture and operating system. This search can be overriden
21433 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21434 taken from shell that executed @value{GDBN}, it is not the value set by
21435 @value{GDBN} command @code{set environment}). @xref{Environment}.
21438 Specifically @env{PATH} is searched for binaries matching regular expression
21439 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21440 debugged. @var{arch} is processor name --- multiarch is supported, so for
21441 example both @code{i386} and @code{x86_64} targets look for pattern
21442 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21443 for pattern @code{s390x?}. @var{os} is currently supported only for
21444 pattern @code{linux(-gnu)?}.
21446 On Posix hosts the compiler driver @value{GDBN} needs to find also
21447 shared library @file{libcc1.so} from the compiler. It is searched in
21448 default shared library search path (overridable with usual environment
21449 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21450 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21451 according to the installation of the found compiler --- as possibly
21452 specified by the @code{set compile-gcc} command.
21455 @item set compile-gcc
21456 @cindex compile command driver filename override
21457 Set compilation command used for compiling and injecting code with the
21458 @code{compile} commands. If this option is not set (it is set to
21459 an empty string), the search described above will occur --- that is the
21462 @item show compile-gcc
21463 Displays the current compile command @value{NGCC} driver filename.
21464 If set, it is the main command @command{gcc}, found usually for example
21465 under name @file{x86_64-linux-gnu-gcc}.
21469 @chapter @value{GDBN} Files
21471 @value{GDBN} needs to know the file name of the program to be debugged,
21472 both in order to read its symbol table and in order to start your
21473 program. To debug a core dump of a previous run, you must also tell
21474 @value{GDBN} the name of the core dump file.
21477 * Files:: Commands to specify files
21478 * File Caching:: Information about @value{GDBN}'s file caching
21479 * Separate Debug Files:: Debugging information in separate files
21480 * MiniDebugInfo:: Debugging information in a special section
21481 * Index Files:: Index files speed up GDB
21482 * Symbol Errors:: Errors reading symbol files
21483 * Data Files:: GDB data files
21487 @section Commands to Specify Files
21489 @cindex symbol table
21490 @cindex core dump file
21492 You may want to specify executable and core dump file names. The usual
21493 way to do this is at start-up time, using the arguments to
21494 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21495 Out of @value{GDBN}}).
21497 Occasionally it is necessary to change to a different file during a
21498 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21499 specify a file you want to use. Or you are debugging a remote target
21500 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21501 Program}). In these situations the @value{GDBN} commands to specify
21502 new files are useful.
21505 @cindex executable file
21507 @item file @var{filename}
21508 Use @var{filename} as the program to be debugged. It is read for its
21509 symbols and for the contents of pure memory. It is also the program
21510 executed when you use the @code{run} command. If you do not specify a
21511 directory and the file is not found in the @value{GDBN} working directory,
21512 @value{GDBN} uses the environment variable @env{PATH} as a list of
21513 directories to search, just as the shell does when looking for a program
21514 to run. You can change the value of this variable, for both @value{GDBN}
21515 and your program, using the @code{path} command.
21517 @cindex unlinked object files
21518 @cindex patching object files
21519 You can load unlinked object @file{.o} files into @value{GDBN} using
21520 the @code{file} command. You will not be able to ``run'' an object
21521 file, but you can disassemble functions and inspect variables. Also,
21522 if the underlying BFD functionality supports it, you could use
21523 @kbd{gdb -write} to patch object files using this technique. Note
21524 that @value{GDBN} can neither interpret nor modify relocations in this
21525 case, so branches and some initialized variables will appear to go to
21526 the wrong place. But this feature is still handy from time to time.
21529 @code{file} with no argument makes @value{GDBN} discard any information it
21530 has on both executable file and the symbol table.
21533 @item exec-file @r{[} @var{filename} @r{]}
21534 Specify that the program to be run (but not the symbol table) is found
21535 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21536 if necessary to locate your program. Omitting @var{filename} means to
21537 discard information on the executable file.
21539 @kindex symbol-file
21540 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21541 Read symbol table information from file @var{filename}. @env{PATH} is
21542 searched when necessary. Use the @code{file} command to get both symbol
21543 table and program to run from the same file.
21545 If an optional @var{offset} is specified, it is added to the start
21546 address of each section in the symbol file. This is useful if the
21547 program is relocated at runtime, such as the Linux kernel with kASLR
21550 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21551 program's symbol table.
21553 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21554 some breakpoints and auto-display expressions. This is because they may
21555 contain pointers to the internal data recording symbols and data types,
21556 which are part of the old symbol table data being discarded inside
21559 @code{symbol-file} does not repeat if you press @key{RET} again after
21562 When @value{GDBN} is configured for a particular environment, it
21563 understands debugging information in whatever format is the standard
21564 generated for that environment; you may use either a @sc{gnu} compiler, or
21565 other compilers that adhere to the local conventions.
21566 Best results are usually obtained from @sc{gnu} compilers; for example,
21567 using @code{@value{NGCC}} you can generate debugging information for
21570 For most kinds of object files, with the exception of old SVR3 systems
21571 using COFF, the @code{symbol-file} command does not normally read the
21572 symbol table in full right away. Instead, it scans the symbol table
21573 quickly to find which source files and which symbols are present. The
21574 details are read later, one source file at a time, as they are needed.
21576 The purpose of this two-stage reading strategy is to make @value{GDBN}
21577 start up faster. For the most part, it is invisible except for
21578 occasional pauses while the symbol table details for a particular source
21579 file are being read. (The @code{set verbose} command can turn these
21580 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21581 Warnings and Messages}.)
21583 We have not implemented the two-stage strategy for COFF yet. When the
21584 symbol table is stored in COFF format, @code{symbol-file} reads the
21585 symbol table data in full right away. Note that ``stabs-in-COFF''
21586 still does the two-stage strategy, since the debug info is actually
21590 @cindex reading symbols immediately
21591 @cindex symbols, reading immediately
21592 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21593 @itemx file @r{[} -readnow @r{]} @var{filename}
21594 You can override the @value{GDBN} two-stage strategy for reading symbol
21595 tables by using the @samp{-readnow} option with any of the commands that
21596 load symbol table information, if you want to be sure @value{GDBN} has the
21597 entire symbol table available.
21599 @cindex @code{-readnever}, option for symbol-file command
21600 @cindex never read symbols
21601 @cindex symbols, never read
21602 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21603 @itemx file @r{[} -readnever @r{]} @var{filename}
21604 You can instruct @value{GDBN} to never read the symbolic information
21605 contained in @var{filename} by using the @samp{-readnever} option.
21606 @xref{--readnever}.
21608 @c FIXME: for now no mention of directories, since this seems to be in
21609 @c flux. 13mar1992 status is that in theory GDB would look either in
21610 @c current dir or in same dir as myprog; but issues like competing
21611 @c GDB's, or clutter in system dirs, mean that in practice right now
21612 @c only current dir is used. FFish says maybe a special GDB hierarchy
21613 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21617 @item core-file @r{[}@var{filename}@r{]}
21619 Specify the whereabouts of a core dump file to be used as the ``contents
21620 of memory''. Traditionally, core files contain only some parts of the
21621 address space of the process that generated them; @value{GDBN} can access the
21622 executable file itself for other parts.
21624 @code{core-file} with no argument specifies that no core file is
21627 Note that the core file is ignored when your program is actually running
21628 under @value{GDBN}. So, if you have been running your program and you
21629 wish to debug a core file instead, you must kill the subprocess in which
21630 the program is running. To do this, use the @code{kill} command
21631 (@pxref{Kill Process, ,Killing the Child Process}).
21633 @kindex add-symbol-file
21634 @cindex dynamic linking
21635 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
21636 The @code{add-symbol-file} command reads additional symbol table
21637 information from the file @var{filename}. You would use this command
21638 when @var{filename} has been dynamically loaded (by some other means)
21639 into the program that is running. The @var{textaddress} parameter gives
21640 the memory address at which the file's text section has been loaded.
21641 You can additionally specify the base address of other sections using
21642 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21643 If a section is omitted, @value{GDBN} will use its default addresses
21644 as found in @var{filename}. Any @var{address} or @var{textaddress}
21645 can be given as an expression.
21647 If an optional @var{offset} is specified, it is added to the start
21648 address of each section, except those for which the address was
21649 specified explicitly.
21651 The symbol table of the file @var{filename} is added to the symbol table
21652 originally read with the @code{symbol-file} command. You can use the
21653 @code{add-symbol-file} command any number of times; the new symbol data
21654 thus read is kept in addition to the old.
21656 Changes can be reverted using the command @code{remove-symbol-file}.
21658 @cindex relocatable object files, reading symbols from
21659 @cindex object files, relocatable, reading symbols from
21660 @cindex reading symbols from relocatable object files
21661 @cindex symbols, reading from relocatable object files
21662 @cindex @file{.o} files, reading symbols from
21663 Although @var{filename} is typically a shared library file, an
21664 executable file, or some other object file which has been fully
21665 relocated for loading into a process, you can also load symbolic
21666 information from relocatable @file{.o} files, as long as:
21670 the file's symbolic information refers only to linker symbols defined in
21671 that file, not to symbols defined by other object files,
21673 every section the file's symbolic information refers to has actually
21674 been loaded into the inferior, as it appears in the file, and
21676 you can determine the address at which every section was loaded, and
21677 provide these to the @code{add-symbol-file} command.
21681 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21682 relocatable files into an already running program; such systems
21683 typically make the requirements above easy to meet. However, it's
21684 important to recognize that many native systems use complex link
21685 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21686 assembly, for example) that make the requirements difficult to meet. In
21687 general, one cannot assume that using @code{add-symbol-file} to read a
21688 relocatable object file's symbolic information will have the same effect
21689 as linking the relocatable object file into the program in the normal
21692 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21694 @kindex remove-symbol-file
21695 @item remove-symbol-file @var{filename}
21696 @item remove-symbol-file -a @var{address}
21697 Remove a symbol file added via the @code{add-symbol-file} command. The
21698 file to remove can be identified by its @var{filename} or by an @var{address}
21699 that lies within the boundaries of this symbol file in memory. Example:
21702 (@value{GDBP}) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21703 add symbol table from file "/home/user/gdb/mylib.so" at
21704 .text_addr = 0x7ffff7ff9480
21706 Reading symbols from /home/user/gdb/mylib.so...
21707 (@value{GDBP}) remove-symbol-file -a 0x7ffff7ff9480
21708 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21713 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21715 @kindex add-symbol-file-from-memory
21716 @cindex @code{syscall DSO}
21717 @cindex load symbols from memory
21718 @item add-symbol-file-from-memory @var{address}
21719 Load symbols from the given @var{address} in a dynamically loaded
21720 object file whose image is mapped directly into the inferior's memory.
21721 For example, the Linux kernel maps a @code{syscall DSO} into each
21722 process's address space; this DSO provides kernel-specific code for
21723 some system calls. The argument can be any expression whose
21724 evaluation yields the address of the file's shared object file header.
21725 For this command to work, you must have used @code{symbol-file} or
21726 @code{exec-file} commands in advance.
21729 @item section @var{section} @var{addr}
21730 The @code{section} command changes the base address of the named
21731 @var{section} of the exec file to @var{addr}. This can be used if the
21732 exec file does not contain section addresses, (such as in the
21733 @code{a.out} format), or when the addresses specified in the file
21734 itself are wrong. Each section must be changed separately. The
21735 @code{info files} command, described below, lists all the sections and
21739 @kindex info target
21742 @code{info files} and @code{info target} are synonymous; both print the
21743 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21744 including the names of the executable and core dump files currently in
21745 use by @value{GDBN}, and the files from which symbols were loaded. The
21746 command @code{help target} lists all possible targets rather than
21749 @kindex maint info sections
21750 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21751 Another command that can give you extra information about program sections
21752 is @code{maint info sections}. In addition to the section information
21753 displayed by @code{info files}, this command displays the flags and file
21754 offset of each section in the executable and core dump files.
21756 When @samp{-all-objects} is passed then sections from all loaded object
21757 files, including shared libraries, are printed.
21759 The optional @var{filter-list} is a space separated list of filter
21760 keywords. Sections that match any one of the filter criteria will be
21761 printed. There are two types of filter:
21764 @item @var{section-name}
21765 Display information about any section named @var{section-name}.
21766 @item @var{section-flag}
21767 Display information for any section with @var{section-flag}. The
21768 section flags that @value{GDBN} currently knows about are:
21771 Section will have space allocated in the process when loaded.
21772 Set for all sections except those containing debug information.
21774 Section will be loaded from the file into the child process memory.
21775 Set for pre-initialized code and data, clear for @code{.bss} sections.
21777 Section needs to be relocated before loading.
21779 Section cannot be modified by the child process.
21781 Section contains executable code only.
21783 Section contains data only (no executable code).
21785 Section will reside in ROM.
21787 Section contains data for constructor/destructor lists.
21789 Section is not empty.
21791 An instruction to the linker to not output the section.
21792 @item COFF_SHARED_LIBRARY
21793 A notification to the linker that the section contains
21794 COFF shared library information.
21796 Section contains common symbols.
21800 @kindex maint info target-sections
21801 @item maint info target-sections
21802 This command prints @value{GDBN}'s internal section table. For each
21803 target @value{GDBN} maintains a table containing the allocatable
21804 sections from all currently mapped objects, along with information
21805 about where the section is mapped.
21807 @kindex set trust-readonly-sections
21808 @cindex read-only sections
21809 @item set trust-readonly-sections on
21810 Tell @value{GDBN} that readonly sections in your object file
21811 really are read-only (i.e.@: that their contents will not change).
21812 In that case, @value{GDBN} can fetch values from these sections
21813 out of the object file, rather than from the target program.
21814 For some targets (notably embedded ones), this can be a significant
21815 enhancement to debugging performance.
21817 The default is off.
21819 @item set trust-readonly-sections off
21820 Tell @value{GDBN} not to trust readonly sections. This means that
21821 the contents of the section might change while the program is running,
21822 and must therefore be fetched from the target when needed.
21824 @item show trust-readonly-sections
21825 Show the current setting of trusting readonly sections.
21828 All file-specifying commands allow both absolute and relative file names
21829 as arguments. @value{GDBN} always converts the file name to an absolute file
21830 name and remembers it that way.
21832 @cindex shared libraries
21833 @anchor{Shared Libraries}
21834 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21835 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21836 DSBT (TIC6X) shared libraries.
21838 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21839 shared libraries. @xref{Expat}.
21841 @value{GDBN} automatically loads symbol definitions from shared libraries
21842 when you use the @code{run} command, or when you examine a core file.
21843 (Before you issue the @code{run} command, @value{GDBN} does not understand
21844 references to a function in a shared library, however---unless you are
21845 debugging a core file).
21847 @c FIXME: some @value{GDBN} release may permit some refs to undef
21848 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21849 @c FIXME...lib; check this from time to time when updating manual
21851 There are times, however, when you may wish to not automatically load
21852 symbol definitions from shared libraries, such as when they are
21853 particularly large or there are many of them.
21855 To control the automatic loading of shared library symbols, use the
21859 @kindex set auto-solib-add
21860 @item set auto-solib-add @var{mode}
21861 If @var{mode} is @code{on}, symbols from all shared object libraries
21862 will be loaded automatically when the inferior begins execution, you
21863 attach to an independently started inferior, or when the dynamic linker
21864 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21865 is @code{off}, symbols must be loaded manually, using the
21866 @code{sharedlibrary} command. The default value is @code{on}.
21868 @cindex memory used for symbol tables
21869 If your program uses lots of shared libraries with debug info that
21870 takes large amounts of memory, you can decrease the @value{GDBN}
21871 memory footprint by preventing it from automatically loading the
21872 symbols from shared libraries. To that end, type @kbd{set
21873 auto-solib-add off} before running the inferior, then load each
21874 library whose debug symbols you do need with @kbd{sharedlibrary
21875 @var{regexp}}, where @var{regexp} is a regular expression that matches
21876 the libraries whose symbols you want to be loaded.
21878 @kindex show auto-solib-add
21879 @item show auto-solib-add
21880 Display the current autoloading mode.
21883 @cindex load shared library
21884 To explicitly load shared library symbols, use the @code{sharedlibrary}
21888 @kindex info sharedlibrary
21890 @item info share @var{regex}
21891 @itemx info sharedlibrary @var{regex}
21892 Print the names of the shared libraries which are currently loaded
21893 that match @var{regex}. If @var{regex} is omitted then print
21894 all shared libraries that are loaded.
21897 @item info dll @var{regex}
21898 This is an alias of @code{info sharedlibrary}.
21900 @kindex sharedlibrary
21902 @item sharedlibrary @var{regex}
21903 @itemx share @var{regex}
21904 Load shared object library symbols for files matching a
21905 Unix regular expression.
21906 As with files loaded automatically, it only loads shared libraries
21907 required by your program for a core file or after typing @code{run}. If
21908 @var{regex} is omitted all shared libraries required by your program are
21911 @item nosharedlibrary
21912 @kindex nosharedlibrary
21913 @cindex unload symbols from shared libraries
21914 Unload all shared object library symbols. This discards all symbols
21915 that have been loaded from all shared libraries. Symbols from shared
21916 libraries that were loaded by explicit user requests are not
21920 Sometimes you may wish that @value{GDBN} stops and gives you control
21921 when any of shared library events happen. The best way to do this is
21922 to use @code{catch load} and @code{catch unload} (@pxref{Set
21925 @value{GDBN} also supports the @code{set stop-on-solib-events}
21926 command for this. This command exists for historical reasons. It is
21927 less useful than setting a catchpoint, because it does not allow for
21928 conditions or commands as a catchpoint does.
21931 @item set stop-on-solib-events
21932 @kindex set stop-on-solib-events
21933 This command controls whether @value{GDBN} should give you control
21934 when the dynamic linker notifies it about some shared library event.
21935 The most common event of interest is loading or unloading of a new
21938 @item show stop-on-solib-events
21939 @kindex show stop-on-solib-events
21940 Show whether @value{GDBN} stops and gives you control when shared
21941 library events happen.
21944 Shared libraries are also supported in many cross or remote debugging
21945 configurations. @value{GDBN} needs to have access to the target's libraries;
21946 this can be accomplished either by providing copies of the libraries
21947 on the host system, or by asking @value{GDBN} to automatically retrieve the
21948 libraries from the target. If copies of the target libraries are
21949 provided, they need to be the same as the target libraries, although the
21950 copies on the target can be stripped as long as the copies on the host are
21953 @cindex where to look for shared libraries
21954 For remote debugging, you need to tell @value{GDBN} where the target
21955 libraries are, so that it can load the correct copies---otherwise, it
21956 may try to load the host's libraries. @value{GDBN} has two variables
21957 to specify the search directories for target libraries.
21960 @cindex prefix for executable and shared library file names
21961 @cindex system root, alternate
21962 @kindex set solib-absolute-prefix
21963 @kindex set sysroot
21964 @item set sysroot @var{path}
21965 Use @var{path} as the system root for the program being debugged. Any
21966 absolute shared library paths will be prefixed with @var{path}; many
21967 runtime loaders store the absolute paths to the shared library in the
21968 target program's memory. When starting processes remotely, and when
21969 attaching to already-running processes (local or remote), their
21970 executable filenames will be prefixed with @var{path} if reported to
21971 @value{GDBN} as absolute by the operating system. If you use
21972 @code{set sysroot} to find executables and shared libraries, they need
21973 to be laid out in the same way that they are on the target, with
21974 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21977 If @var{path} starts with the sequence @file{target:} and the target
21978 system is remote then @value{GDBN} will retrieve the target binaries
21979 from the remote system. This is only supported when using a remote
21980 target that supports the @code{remote get} command (@pxref{File
21981 Transfer,,Sending files to a remote system}). The part of @var{path}
21982 following the initial @file{target:} (if present) is used as system
21983 root prefix on the remote file system. If @var{path} starts with the
21984 sequence @file{remote:} this is converted to the sequence
21985 @file{target:} by @code{set sysroot}@footnote{Historically the
21986 functionality to retrieve binaries from the remote system was
21987 provided by prefixing @var{path} with @file{remote:}}. If you want
21988 to specify a local system root using a directory that happens to be
21989 named @file{target:} or @file{remote:}, you need to use some
21990 equivalent variant of the name like @file{./target:}.
21992 For targets with an MS-DOS based filesystem, such as MS-Windows,
21993 @value{GDBN} tries prefixing a few variants of the target
21994 absolute file name with @var{path}. But first, on Unix hosts,
21995 @value{GDBN} converts all backslash directory separators into forward
21996 slashes, because the backslash is not a directory separator on Unix:
21999 c:\foo\bar.dll @result{} c:/foo/bar.dll
22002 Then, @value{GDBN} attempts prefixing the target file name with
22003 @var{path}, and looks for the resulting file name in the host file
22007 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
22010 If that does not find the binary, @value{GDBN} tries removing
22011 the @samp{:} character from the drive spec, both for convenience, and,
22012 for the case of the host file system not supporting file names with
22016 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
22019 This makes it possible to have a system root that mirrors a target
22020 with more than one drive. E.g., you may want to setup your local
22021 copies of the target system shared libraries like so (note @samp{c} vs
22025 @file{/path/to/sysroot/c/sys/bin/foo.dll}
22026 @file{/path/to/sysroot/c/sys/bin/bar.dll}
22027 @file{/path/to/sysroot/z/sys/bin/bar.dll}
22031 and point the system root at @file{/path/to/sysroot}, so that
22032 @value{GDBN} can find the correct copies of both
22033 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
22035 If that still does not find the binary, @value{GDBN} tries
22036 removing the whole drive spec from the target file name:
22039 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
22042 This last lookup makes it possible to not care about the drive name,
22043 if you don't want or need to.
22045 The @code{set solib-absolute-prefix} command is an alias for @code{set
22048 @cindex default system root
22049 @cindex @samp{--with-sysroot}
22050 You can set the default system root by using the configure-time
22051 @samp{--with-sysroot} option. If the system root is inside
22052 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22053 @samp{--exec-prefix}), then the default system root will be updated
22054 automatically if the installed @value{GDBN} is moved to a new
22057 @kindex show sysroot
22059 Display the current executable and shared library prefix.
22061 @kindex set solib-search-path
22062 @item set solib-search-path @var{path}
22063 If this variable is set, @var{path} is a colon-separated list of
22064 directories to search for shared libraries. @samp{solib-search-path}
22065 is used after @samp{sysroot} fails to locate the library, or if the
22066 path to the library is relative instead of absolute. If you want to
22067 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
22068 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
22069 finding your host's libraries. @samp{sysroot} is preferred; setting
22070 it to a nonexistent directory may interfere with automatic loading
22071 of shared library symbols.
22073 @kindex show solib-search-path
22074 @item show solib-search-path
22075 Display the current shared library search path.
22077 @cindex DOS file-name semantics of file names.
22078 @kindex set target-file-system-kind (unix|dos-based|auto)
22079 @kindex show target-file-system-kind
22080 @item set target-file-system-kind @var{kind}
22081 Set assumed file system kind for target reported file names.
22083 Shared library file names as reported by the target system may not
22084 make sense as is on the system @value{GDBN} is running on. For
22085 example, when remote debugging a target that has MS-DOS based file
22086 system semantics, from a Unix host, the target may be reporting to
22087 @value{GDBN} a list of loaded shared libraries with file names such as
22088 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
22089 drive letters, so the @samp{c:\} prefix is not normally understood as
22090 indicating an absolute file name, and neither is the backslash
22091 normally considered a directory separator character. In that case,
22092 the native file system would interpret this whole absolute file name
22093 as a relative file name with no directory components. This would make
22094 it impossible to point @value{GDBN} at a copy of the remote target's
22095 shared libraries on the host using @code{set sysroot}, and impractical
22096 with @code{set solib-search-path}. Setting
22097 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
22098 to interpret such file names similarly to how the target would, and to
22099 map them to file names valid on @value{GDBN}'s native file system
22100 semantics. The value of @var{kind} can be @code{"auto"}, in addition
22101 to one of the supported file system kinds. In that case, @value{GDBN}
22102 tries to determine the appropriate file system variant based on the
22103 current target's operating system (@pxref{ABI, ,Configuring the
22104 Current ABI}). The supported file system settings are:
22108 Instruct @value{GDBN} to assume the target file system is of Unix
22109 kind. Only file names starting the forward slash (@samp{/}) character
22110 are considered absolute, and the directory separator character is also
22114 Instruct @value{GDBN} to assume the target file system is DOS based.
22115 File names starting with either a forward slash, or a drive letter
22116 followed by a colon (e.g., @samp{c:}), are considered absolute, and
22117 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
22118 considered directory separators.
22121 Instruct @value{GDBN} to use the file system kind associated with the
22122 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
22123 This is the default.
22127 @cindex file name canonicalization
22128 @cindex base name differences
22129 When processing file names provided by the user, @value{GDBN}
22130 frequently needs to compare them to the file names recorded in the
22131 program's debug info. Normally, @value{GDBN} compares just the
22132 @dfn{base names} of the files as strings, which is reasonably fast
22133 even for very large programs. (The base name of a file is the last
22134 portion of its name, after stripping all the leading directories.)
22135 This shortcut in comparison is based upon the assumption that files
22136 cannot have more than one base name. This is usually true, but
22137 references to files that use symlinks or similar filesystem
22138 facilities violate that assumption. If your program records files
22139 using such facilities, or if you provide file names to @value{GDBN}
22140 using symlinks etc., you can set @code{basenames-may-differ} to
22141 @code{true} to instruct @value{GDBN} to completely canonicalize each
22142 pair of file names it needs to compare. This will make file-name
22143 comparisons accurate, but at a price of a significant slowdown.
22146 @item set basenames-may-differ
22147 @kindex set basenames-may-differ
22148 Set whether a source file may have multiple base names.
22150 @item show basenames-may-differ
22151 @kindex show basenames-may-differ
22152 Show whether a source file may have multiple base names.
22156 @section File Caching
22157 @cindex caching of opened files
22158 @cindex caching of bfd objects
22160 To speed up file loading, and reduce memory usage, @value{GDBN} will
22161 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
22162 BFD, bfd, The Binary File Descriptor Library}. The following commands
22163 allow visibility and control of the caching behavior.
22166 @kindex maint info bfds
22167 @item maint info bfds
22168 This prints information about each @code{bfd} object that is known to
22171 @kindex maint set bfd-sharing
22172 @kindex maint show bfd-sharing
22173 @kindex bfd caching
22174 @item maint set bfd-sharing
22175 @item maint show bfd-sharing
22176 Control whether @code{bfd} objects can be shared. When sharing is
22177 enabled @value{GDBN} reuses already open @code{bfd} objects rather
22178 than reopening the same file. Turning sharing off does not cause
22179 already shared @code{bfd} objects to be unshared, but all future files
22180 that are opened will create a new @code{bfd} object. Similarly,
22181 re-enabling sharing does not cause multiple existing @code{bfd}
22182 objects to be collapsed into a single shared @code{bfd} object.
22184 @kindex set debug bfd-cache @var{level}
22185 @kindex bfd caching
22186 @item set debug bfd-cache @var{level}
22187 Turns on debugging of the bfd cache, setting the level to @var{level}.
22189 @kindex show debug bfd-cache
22190 @kindex bfd caching
22191 @item show debug bfd-cache
22192 Show the current debugging level of the bfd cache.
22195 @node Separate Debug Files
22196 @section Debugging Information in Separate Files
22197 @cindex separate debugging information files
22198 @cindex debugging information in separate files
22199 @cindex @file{.debug} subdirectories
22200 @cindex debugging information directory, global
22201 @cindex global debugging information directories
22202 @cindex build ID, and separate debugging files
22203 @cindex @file{.build-id} directory
22205 @value{GDBN} allows you to put a program's debugging information in a
22206 file separate from the executable itself, in a way that allows
22207 @value{GDBN} to find and load the debugging information automatically.
22208 Since debugging information can be very large---sometimes larger
22209 than the executable code itself---some systems distribute debugging
22210 information for their executables in separate files, which users can
22211 install only when they need to debug a problem.
22213 @value{GDBN} supports two ways of specifying the separate debug info
22218 The executable contains a @dfn{debug link} that specifies the name of
22219 the separate debug info file. The separate debug file's name is
22220 usually @file{@var{executable}.debug}, where @var{executable} is the
22221 name of the corresponding executable file without leading directories
22222 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
22223 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
22224 checksum for the debug file, which @value{GDBN} uses to validate that
22225 the executable and the debug file came from the same build.
22229 The executable contains a @dfn{build ID}, a unique bit string that is
22230 also present in the corresponding debug info file. (This is supported
22231 only on some operating systems, when using the ELF or PE file formats
22232 for binary files and the @sc{gnu} Binutils.) For more details about
22233 this feature, see the description of the @option{--build-id}
22234 command-line option in @ref{Options, , Command Line Options, ld,
22235 The GNU Linker}. The debug info file's name is not specified
22236 explicitly by the build ID, but can be computed from the build ID, see
22240 Depending on the way the debug info file is specified, @value{GDBN}
22241 uses two different methods of looking for the debug file:
22245 For the ``debug link'' method, @value{GDBN} looks up the named file in
22246 the directory of the executable file, then in a subdirectory of that
22247 directory named @file{.debug}, and finally under each one of the
22248 global debug directories, in a subdirectory whose name is identical to
22249 the leading directories of the executable's absolute file name. (On
22250 MS-Windows/MS-DOS, the drive letter of the executable's leading
22251 directories is converted to a one-letter subdirectory, i.e.@:
22252 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
22253 filesystems disallow colons in file names.)
22256 For the ``build ID'' method, @value{GDBN} looks in the
22257 @file{.build-id} subdirectory of each one of the global debug directories for
22258 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
22259 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
22260 are the rest of the bit string. (Real build ID strings are 32 or more
22261 hex characters, not 10.) @value{GDBN} can automatically query
22262 @code{debuginfod} servers using build IDs in order to download separate debug
22263 files that cannot be found locally. For more information see @ref{Debuginfod}.
22266 So, for example, suppose you ask @value{GDBN} to debug
22267 @file{/usr/bin/ls}, which has a debug link that specifies the
22268 file @file{ls.debug}, and a build ID whose value in hex is
22269 @code{abcdef1234}. If the list of the global debug directories includes
22270 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
22271 debug information files, in the indicated order:
22275 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
22277 @file{/usr/bin/ls.debug}
22279 @file{/usr/bin/.debug/ls.debug}
22281 @file{/usr/lib/debug/usr/bin/ls.debug}.
22284 If the debug file still has not been found and @code{debuginfod}
22285 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
22286 file from @code{debuginfod} servers.
22288 @anchor{debug-file-directory}
22289 Global debugging info directories default to what is set by @value{GDBN}
22290 configure option @option{--with-separate-debug-dir} and augmented by the
22291 colon-separated list of directories provided via @value{GDBN} configure
22292 option @option{--additional-debug-dirs}. During @value{GDBN} run you can
22293 also set the global debugging info directories, and view the list
22294 @value{GDBN} is currently using.
22298 @kindex set debug-file-directory
22299 @item set debug-file-directory @var{directories}
22300 Set the directories which @value{GDBN} searches for separate debugging
22301 information files to @var{directory}. Multiple path components can be set
22302 concatenating them by a path separator.
22304 @kindex show debug-file-directory
22305 @item show debug-file-directory
22306 Show the directories @value{GDBN} searches for separate debugging
22311 @cindex @code{.gnu_debuglink} sections
22312 @cindex debug link sections
22313 A debug link is a special section of the executable file named
22314 @code{.gnu_debuglink}. The section must contain:
22318 A filename, with any leading directory components removed, followed by
22321 zero to three bytes of padding, as needed to reach the next four-byte
22322 boundary within the section, and
22324 a four-byte CRC checksum, stored in the same endianness used for the
22325 executable file itself. The checksum is computed on the debugging
22326 information file's full contents by the function given below, passing
22327 zero as the @var{crc} argument.
22330 Any executable file format can carry a debug link, as long as it can
22331 contain a section named @code{.gnu_debuglink} with the contents
22334 @cindex @code{.note.gnu.build-id} sections
22335 @cindex build ID sections
22336 The build ID is a special section in the executable file (and in other
22337 ELF binary files that @value{GDBN} may consider). This section is
22338 often named @code{.note.gnu.build-id}, but that name is not mandatory.
22339 It contains unique identification for the built files---the ID remains
22340 the same across multiple builds of the same build tree. The default
22341 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
22342 content for the build ID string. The same section with an identical
22343 value is present in the original built binary with symbols, in its
22344 stripped variant, and in the separate debugging information file.
22346 The debugging information file itself should be an ordinary
22347 executable, containing a full set of linker symbols, sections, and
22348 debugging information. The sections of the debugging information file
22349 should have the same names, addresses, and sizes as the original file,
22350 but they need not contain any data---much like a @code{.bss} section
22351 in an ordinary executable.
22353 The @sc{gnu} binary utilities (Binutils) package includes the
22354 @samp{objcopy} utility that can produce
22355 the separated executable / debugging information file pairs using the
22356 following commands:
22359 @kbd{objcopy --only-keep-debug foo foo.debug}
22364 These commands remove the debugging
22365 information from the executable file @file{foo} and place it in the file
22366 @file{foo.debug}. You can use the first, second or both methods to link the
22371 The debug link method needs the following additional command to also leave
22372 behind a debug link in @file{foo}:
22375 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
22378 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
22379 a version of the @code{strip} command such that the command @kbd{strip foo -f
22380 foo.debug} has the same functionality as the two @code{objcopy} commands and
22381 the @code{ln -s} command above, together.
22384 Build ID gets embedded into the main executable using @code{ld --build-id} or
22385 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
22386 compatibility fixes for debug files separation are present in @sc{gnu} binary
22387 utilities (Binutils) package since version 2.18.
22392 @cindex CRC algorithm definition
22393 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
22394 IEEE 802.3 using the polynomial:
22396 @c TexInfo requires naked braces for multi-digit exponents for Tex
22397 @c output, but this causes HTML output to barf. HTML has to be set using
22398 @c raw commands. So we end up having to specify this equation in 2
22403 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
22404 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
22410 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
22411 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
22415 The function is computed byte at a time, taking the least
22416 significant bit of each byte first. The initial pattern
22417 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
22418 the final result is inverted to ensure trailing zeros also affect the
22421 @emph{Note:} This is the same CRC polynomial as used in handling the
22422 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
22423 However in the case of the Remote Serial Protocol, the CRC is computed
22424 @emph{most} significant bit first, and the result is not inverted, so
22425 trailing zeros have no effect on the CRC value.
22427 To complete the description, we show below the code of the function
22428 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22429 initially supplied @code{crc} argument means that an initial call to
22430 this function passing in zero will start computing the CRC using
22433 @kindex gnu_debuglink_crc32
22436 gnu_debuglink_crc32 (unsigned long crc,
22437 unsigned char *buf, size_t len)
22439 static const unsigned long crc32_table[256] =
22441 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22442 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22443 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22444 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22445 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22446 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22447 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22448 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22449 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22450 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22451 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22452 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22453 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22454 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22455 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22456 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22457 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22458 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22459 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22460 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22461 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22462 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22463 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22464 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22465 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22466 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22467 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22468 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22469 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22470 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22471 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22472 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22473 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22474 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22475 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22476 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22477 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22478 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22479 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22480 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22481 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22482 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22483 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22484 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22485 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22486 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22487 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22488 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22489 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22490 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22491 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22494 unsigned char *end;
22496 crc = ~crc & 0xffffffff;
22497 for (end = buf + len; buf < end; ++buf)
22498 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22499 return ~crc & 0xffffffff;
22504 This computation does not apply to the ``build ID'' method.
22506 @node MiniDebugInfo
22507 @section Debugging information in a special section
22508 @cindex separate debug sections
22509 @cindex @samp{.gnu_debugdata} section
22511 Some systems ship pre-built executables and libraries that have a
22512 special @samp{.gnu_debugdata} section. This feature is called
22513 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22514 is used to supply extra symbols for backtraces.
22516 The intent of this section is to provide extra minimal debugging
22517 information for use in simple backtraces. It is not intended to be a
22518 replacement for full separate debugging information (@pxref{Separate
22519 Debug Files}). The example below shows the intended use; however,
22520 @value{GDBN} does not currently put restrictions on what sort of
22521 debugging information might be included in the section.
22523 @value{GDBN} has support for this extension. If the section exists,
22524 then it is used provided that no other source of debugging information
22525 can be found, and that @value{GDBN} was configured with LZMA support.
22527 This section can be easily created using @command{objcopy} and other
22528 standard utilities:
22531 # Extract the dynamic symbols from the main binary, there is no need
22532 # to also have these in the normal symbol table.
22533 nm -D @var{binary} --format=posix --defined-only \
22534 | awk '@{ print $1 @}' | sort > dynsyms
22536 # Extract all the text (i.e. function) symbols from the debuginfo.
22537 # (Note that we actually also accept "D" symbols, for the benefit
22538 # of platforms like PowerPC64 that use function descriptors.)
22539 nm @var{binary} --format=posix --defined-only \
22540 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22543 # Keep all the function symbols not already in the dynamic symbol
22545 comm -13 dynsyms funcsyms > keep_symbols
22547 # Separate full debug info into debug binary.
22548 objcopy --only-keep-debug @var{binary} debug
22550 # Copy the full debuginfo, keeping only a minimal set of symbols and
22551 # removing some unnecessary sections.
22552 objcopy -S --remove-section .gdb_index --remove-section .comment \
22553 --keep-symbols=keep_symbols debug mini_debuginfo
22555 # Drop the full debug info from the original binary.
22556 strip --strip-all -R .comment @var{binary}
22558 # Inject the compressed data into the .gnu_debugdata section of the
22561 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22565 @section Index Files Speed Up @value{GDBN}
22566 @cindex index files
22567 @cindex @samp{.gdb_index} section
22569 When @value{GDBN} finds a symbol file, it scans the symbols in the
22570 file in order to construct an internal symbol table. This lets most
22571 @value{GDBN} operations work quickly---at the cost of a delay early
22572 on. For large programs, this delay can be quite lengthy, so
22573 @value{GDBN} provides a way to build an index, which speeds up
22576 For convenience, @value{GDBN} comes with a program,
22577 @command{gdb-add-index}, which can be used to add the index to a
22578 symbol file. It takes the symbol file as its only argument:
22581 $ gdb-add-index symfile
22584 @xref{gdb-add-index}.
22586 It is also possible to do the work manually. Here is what
22587 @command{gdb-add-index} does behind the curtains.
22589 The index is stored as a section in the symbol file. @value{GDBN} can
22590 write the index to a file, then you can put it into the symbol file
22591 using @command{objcopy}.
22593 To create an index file, use the @code{save gdb-index} command:
22596 @item save gdb-index [-dwarf-5] @var{directory}
22597 @kindex save gdb-index
22598 Create index files for all symbol files currently known by
22599 @value{GDBN}. For each known @var{symbol-file}, this command by
22600 default creates it produces a single file
22601 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22602 the @option{-dwarf-5} option, it produces 2 files:
22603 @file{@var{symbol-file}.debug_names} and
22604 @file{@var{symbol-file}.debug_str}. The files are created in the
22605 given @var{directory}.
22608 Once you have created an index file you can merge it into your symbol
22609 file, here named @file{symfile}, using @command{objcopy}:
22612 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22613 --set-section-flags .gdb_index=readonly symfile symfile
22616 Or for @code{-dwarf-5}:
22619 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22620 $ cat symfile.debug_str >>symfile.debug_str.new
22621 $ objcopy --add-section .debug_names=symfile.gdb-index \
22622 --set-section-flags .debug_names=readonly \
22623 --update-section .debug_str=symfile.debug_str.new symfile symfile
22626 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22627 sections that have been deprecated. Usually they are deprecated because
22628 they are missing a new feature or have performance issues.
22629 To tell @value{GDBN} to use a deprecated index section anyway
22630 specify @code{set use-deprecated-index-sections on}.
22631 The default is @code{off}.
22632 This can speed up startup, but may result in some functionality being lost.
22633 @xref{Index Section Format}.
22635 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22636 must be done before gdb reads the file. The following will not work:
22639 $ gdb -ex "set use-deprecated-index-sections on" <program>
22642 Instead you must do, for example,
22645 $ gdb -iex "set use-deprecated-index-sections on" <program>
22648 Indices only work when using DWARF debugging information, not stabs.
22650 @subsection Automatic symbol index cache
22652 @cindex automatic symbol index cache
22653 It is possible for @value{GDBN} to automatically save a copy of this index in a
22654 cache on disk and retrieve it from there when loading the same binary in the
22655 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22656 The following commands can be used to tweak the behavior of the index cache.
22660 @kindex set index-cache
22661 @item set index-cache enabled on
22662 @itemx set index-cache enabled off
22663 Enable or disable the use of the symbol index cache.
22665 @item set index-cache directory @var{directory}
22666 @kindex show index-cache
22667 @itemx show index-cache directory
22668 Set/show the directory where index files will be saved.
22670 The default value for this directory depends on the host platform. On
22671 most systems, the index is cached in the @file{gdb} subdirectory of
22672 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22673 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22674 of your home directory. However, on some systems, the default may
22675 differ according to local convention.
22677 There is no limit on the disk space used by index cache. It is perfectly safe
22678 to delete the content of that directory to free up disk space.
22680 @item show index-cache stats
22681 Print the number of cache hits and misses since the launch of @value{GDBN}.
22685 @node Symbol Errors
22686 @section Errors Reading Symbol Files
22688 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22689 such as symbol types it does not recognize, or known bugs in compiler
22690 output. By default, @value{GDBN} does not notify you of such problems, since
22691 they are relatively common and primarily of interest to people
22692 debugging compilers. If you are interested in seeing information
22693 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22694 only one message about each such type of problem, no matter how many
22695 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22696 to see how many times the problems occur, with the @code{set
22697 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22700 The messages currently printed, and their meanings, include:
22703 @item inner block not inside outer block in @var{symbol}
22705 The symbol information shows where symbol scopes begin and end
22706 (such as at the start of a function or a block of statements). This
22707 error indicates that an inner scope block is not fully contained
22708 in its outer scope blocks.
22710 @value{GDBN} circumvents the problem by treating the inner block as if it had
22711 the same scope as the outer block. In the error message, @var{symbol}
22712 may be shown as ``@code{(don't know)}'' if the outer block is not a
22715 @item block at @var{address} out of order
22717 The symbol information for symbol scope blocks should occur in
22718 order of increasing addresses. This error indicates that it does not
22721 @value{GDBN} does not circumvent this problem, and has trouble
22722 locating symbols in the source file whose symbols it is reading. (You
22723 can often determine what source file is affected by specifying
22724 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22727 @item bad block start address patched
22729 The symbol information for a symbol scope block has a start address
22730 smaller than the address of the preceding source line. This is known
22731 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22733 @value{GDBN} circumvents the problem by treating the symbol scope block as
22734 starting on the previous source line.
22736 @item bad string table offset in symbol @var{n}
22739 Symbol number @var{n} contains a pointer into the string table which is
22740 larger than the size of the string table.
22742 @value{GDBN} circumvents the problem by considering the symbol to have the
22743 name @code{foo}, which may cause other problems if many symbols end up
22746 @item unknown symbol type @code{0x@var{nn}}
22748 The symbol information contains new data types that @value{GDBN} does
22749 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22750 uncomprehended information, in hexadecimal.
22752 @value{GDBN} circumvents the error by ignoring this symbol information.
22753 This usually allows you to debug your program, though certain symbols
22754 are not accessible. If you encounter such a problem and feel like
22755 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22756 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22757 and examine @code{*bufp} to see the symbol.
22759 @item stub type has NULL name
22761 @value{GDBN} could not find the full definition for a struct or class.
22763 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22764 The symbol information for a C@t{++} member function is missing some
22765 information that recent versions of the compiler should have output for
22768 @item info mismatch between compiler and debugger
22770 @value{GDBN} could not parse a type specification output by the compiler.
22775 @section GDB Data Files
22777 @cindex prefix for data files
22778 @value{GDBN} will sometimes read an auxiliary data file. These files
22779 are kept in a directory known as the @dfn{data directory}.
22781 You can set the data directory's name, and view the name @value{GDBN}
22782 is currently using.
22785 @kindex set data-directory
22786 @item set data-directory @var{directory}
22787 Set the directory which @value{GDBN} searches for auxiliary data files
22788 to @var{directory}.
22790 @kindex show data-directory
22791 @item show data-directory
22792 Show the directory @value{GDBN} searches for auxiliary data files.
22795 @cindex default data directory
22796 @cindex @samp{--with-gdb-datadir}
22797 You can set the default data directory by using the configure-time
22798 @samp{--with-gdb-datadir} option. If the data directory is inside
22799 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22800 @samp{--exec-prefix}), then the default data directory will be updated
22801 automatically if the installed @value{GDBN} is moved to a new
22804 The data directory may also be specified with the
22805 @code{--data-directory} command line option.
22806 @xref{Mode Options}.
22809 @chapter Specifying a Debugging Target
22811 @cindex debugging target
22812 A @dfn{target} is the execution environment occupied by your program.
22814 Often, @value{GDBN} runs in the same host environment as your program;
22815 in that case, the debugging target is specified as a side effect when
22816 you use the @code{file} or @code{core} commands. When you need more
22817 flexibility---for example, running @value{GDBN} on a physically separate
22818 host, or controlling a standalone system over a serial port or a
22819 realtime system over a TCP/IP connection---you can use the @code{target}
22820 command to specify one of the target types configured for @value{GDBN}
22821 (@pxref{Target Commands, ,Commands for Managing Targets}).
22823 @cindex target architecture
22824 It is possible to build @value{GDBN} for several different @dfn{target
22825 architectures}. When @value{GDBN} is built like that, you can choose
22826 one of the available architectures with the @kbd{set architecture}
22830 @kindex set architecture
22831 @kindex show architecture
22832 @item set architecture @var{arch}
22833 This command sets the current target architecture to @var{arch}. The
22834 value of @var{arch} can be @code{"auto"}, in addition to one of the
22835 supported architectures.
22837 @item show architecture
22838 Show the current target architecture.
22840 @item set processor
22842 @kindex set processor
22843 @kindex show processor
22844 These are alias commands for, respectively, @code{set architecture}
22845 and @code{show architecture}.
22849 * Active Targets:: Active targets
22850 * Target Commands:: Commands for managing targets
22851 * Byte Order:: Choosing target byte order
22854 @node Active Targets
22855 @section Active Targets
22857 @cindex stacking targets
22858 @cindex active targets
22859 @cindex multiple targets
22861 There are multiple classes of targets such as: processes, executable files or
22862 recording sessions. Core files belong to the process class, making core file
22863 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22864 on multiple active targets, one in each class. This allows you to (for
22865 example) start a process and inspect its activity, while still having access to
22866 the executable file after the process finishes. Or if you start process
22867 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22868 presented a virtual layer of the recording target, while the process target
22869 remains stopped at the chronologically last point of the process execution.
22871 Use the @code{core-file} and @code{exec-file} commands to select a new core
22872 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22873 specify as a target a process that is already running, use the @code{attach}
22874 command (@pxref{Attach, ,Debugging an Already-running Process}).
22876 @node Target Commands
22877 @section Commands for Managing Targets
22880 @item target @var{type} @var{parameters}
22881 Connects the @value{GDBN} host environment to a target machine or
22882 process. A target is typically a protocol for talking to debugging
22883 facilities. You use the argument @var{type} to specify the type or
22884 protocol of the target machine.
22886 Further @var{parameters} are interpreted by the target protocol, but
22887 typically include things like device names or host names to connect
22888 with, process numbers, and baud rates.
22890 The @code{target} command does not repeat if you press @key{RET} again
22891 after executing the command.
22893 @kindex help target
22895 Displays the names of all targets available. To display targets
22896 currently selected, use either @code{info target} or @code{info files}
22897 (@pxref{Files, ,Commands to Specify Files}).
22899 @item help target @var{name}
22900 Describe a particular target, including any parameters necessary to
22903 @kindex set gnutarget
22904 @item set gnutarget @var{args}
22905 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22906 knows whether it is reading an @dfn{executable},
22907 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22908 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22909 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22912 @emph{Warning:} To specify a file format with @code{set gnutarget},
22913 you must know the actual BFD name.
22917 @xref{Files, , Commands to Specify Files}.
22919 @kindex show gnutarget
22920 @item show gnutarget
22921 Use the @code{show gnutarget} command to display what file format
22922 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22923 @value{GDBN} will determine the file format for each file automatically,
22924 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22927 @cindex common targets
22928 Here are some common targets (available, or not, depending on the GDB
22933 @item target exec @var{program}
22934 @cindex executable file target
22935 An executable file. @samp{target exec @var{program}} is the same as
22936 @samp{exec-file @var{program}}.
22938 @item target core @var{filename}
22939 @cindex core dump file target
22940 A core dump file. @samp{target core @var{filename}} is the same as
22941 @samp{core-file @var{filename}}.
22943 @item target remote @var{medium}
22944 @cindex remote target
22945 A remote system connected to @value{GDBN} via a serial line or network
22946 connection. This command tells @value{GDBN} to use its own remote
22947 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22949 For example, if you have a board connected to @file{/dev/ttya} on the
22950 machine running @value{GDBN}, you could say:
22953 target remote /dev/ttya
22956 @code{target remote} supports the @code{load} command. This is only
22957 useful if you have some other way of getting the stub to the target
22958 system, and you can put it somewhere in memory where it won't get
22959 clobbered by the download.
22961 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22962 @cindex built-in simulator target
22963 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22971 works; however, you cannot assume that a specific memory map, device
22972 drivers, or even basic I/O is available, although some simulators do
22973 provide these. For info about any processor-specific simulator details,
22974 see the appropriate section in @ref{Embedded Processors, ,Embedded
22977 @item target native
22978 @cindex native target
22979 Setup for local/native process debugging. Useful to make the
22980 @code{run} command spawn native processes (likewise @code{attach},
22981 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22982 (@pxref{set auto-connect-native-target}).
22986 Different targets are available on different configurations of @value{GDBN};
22987 your configuration may have more or fewer targets.
22989 Many remote targets require you to download the executable's code once
22990 you've successfully established a connection. You may wish to control
22991 various aspects of this process.
22996 @kindex set hash@r{, for remote monitors}
22997 @cindex hash mark while downloading
22998 This command controls whether a hash mark @samp{#} is displayed while
22999 downloading a file to the remote monitor. If on, a hash mark is
23000 displayed after each S-record is successfully downloaded to the
23004 @kindex show hash@r{, for remote monitors}
23005 Show the current status of displaying the hash mark.
23007 @item set debug monitor
23008 @kindex set debug monitor
23009 @cindex display remote monitor communications
23010 Enable or disable display of communications messages between
23011 @value{GDBN} and the remote monitor.
23013 @item show debug monitor
23014 @kindex show debug monitor
23015 Show the current status of displaying communications between
23016 @value{GDBN} and the remote monitor.
23021 @kindex load @var{filename} @var{offset}
23022 @item load @var{filename} @var{offset}
23024 Depending on what remote debugging facilities are configured into
23025 @value{GDBN}, the @code{load} command may be available. Where it exists, it
23026 is meant to make @var{filename} (an executable) available for debugging
23027 on the remote system---by downloading, or dynamic linking, for example.
23028 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
23029 the @code{add-symbol-file} command.
23031 If your @value{GDBN} does not have a @code{load} command, attempting to
23032 execute it gets the error message ``@code{You can't do that when your
23033 target is @dots{}}''
23035 The file is loaded at whatever address is specified in the executable.
23036 For some object file formats, you can specify the load address when you
23037 link the program; for other formats, like a.out, the object file format
23038 specifies a fixed address.
23039 @c FIXME! This would be a good place for an xref to the GNU linker doc.
23041 It is also possible to tell @value{GDBN} to load the executable file at a
23042 specific offset described by the optional argument @var{offset}. When
23043 @var{offset} is provided, @var{filename} must also be provided.
23045 Depending on the remote side capabilities, @value{GDBN} may be able to
23046 load programs into flash memory.
23048 @code{load} does not repeat if you press @key{RET} again after using it.
23053 @kindex flash-erase
23055 @anchor{flash-erase}
23057 Erases all known flash memory regions on the target.
23062 @section Choosing Target Byte Order
23064 @cindex choosing target byte order
23065 @cindex target byte order
23067 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
23068 offer the ability to run either big-endian or little-endian byte
23069 orders. Usually the executable or symbol will include a bit to
23070 designate the endian-ness, and you will not need to worry about
23071 which to use. However, you may still find it useful to adjust
23072 @value{GDBN}'s idea of processor endian-ness manually.
23076 @item set endian big
23077 Instruct @value{GDBN} to assume the target is big-endian.
23079 @item set endian little
23080 Instruct @value{GDBN} to assume the target is little-endian.
23082 @item set endian auto
23083 Instruct @value{GDBN} to use the byte order associated with the
23087 Display @value{GDBN}'s current idea of the target byte order.
23091 If the @code{set endian auto} mode is in effect and no executable has
23092 been selected, then the endianness used is the last one chosen either
23093 by one of the @code{set endian big} and @code{set endian little}
23094 commands or by inferring from the last executable used. If no
23095 endianness has been previously chosen, then the default for this mode
23096 is inferred from the target @value{GDBN} has been built for, and is
23097 @code{little} if the name of the target CPU has an @code{el} suffix
23098 and @code{big} otherwise.
23100 Note that these commands merely adjust interpretation of symbolic
23101 data on the host, and that they have absolutely no effect on the
23105 @node Remote Debugging
23106 @chapter Debugging Remote Programs
23107 @cindex remote debugging
23109 If you are trying to debug a program running on a machine that cannot run
23110 @value{GDBN} in the usual way, it is often useful to use remote debugging.
23111 For example, you might use remote debugging on an operating system kernel,
23112 or on a small system which does not have a general purpose operating system
23113 powerful enough to run a full-featured debugger.
23115 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
23116 to make this work with particular debugging targets. In addition,
23117 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
23118 but not specific to any particular target system) which you can use if you
23119 write the remote stubs---the code that runs on the remote system to
23120 communicate with @value{GDBN}.
23122 Other remote targets may be available in your
23123 configuration of @value{GDBN}; use @code{help target} to list them.
23126 * Connecting:: Connecting to a remote target
23127 * File Transfer:: Sending files to a remote system
23128 * Server:: Using the gdbserver program
23129 * Remote Configuration:: Remote configuration
23130 * Remote Stub:: Implementing a remote stub
23134 @section Connecting to a Remote Target
23135 @cindex remote debugging, connecting
23136 @cindex @code{gdbserver}, connecting
23137 @cindex remote debugging, types of connections
23138 @cindex @code{gdbserver}, types of connections
23139 @cindex @code{gdbserver}, @code{target remote} mode
23140 @cindex @code{gdbserver}, @code{target extended-remote} mode
23142 This section describes how to connect to a remote target, including the
23143 types of connections and their differences, how to set up executable and
23144 symbol files on the host and target, and the commands used for
23145 connecting to and disconnecting from the remote target.
23147 @subsection Types of Remote Connections
23149 @value{GDBN} supports two types of remote connections, @code{target remote}
23150 mode and @code{target extended-remote} mode. Note that many remote targets
23151 support only @code{target remote} mode. There are several major
23152 differences between the two types of connections, enumerated here:
23156 @cindex remote debugging, detach and program exit
23157 @item Result of detach or program exit
23158 @strong{With target remote mode:} When the debugged program exits or you
23159 detach from it, @value{GDBN} disconnects from the target. When using
23160 @code{gdbserver}, @code{gdbserver} will exit.
23162 @strong{With target extended-remote mode:} When the debugged program exits or
23163 you detach from it, @value{GDBN} remains connected to the target, even
23164 though no program is running. You can rerun the program, attach to a
23165 running program, or use @code{monitor} commands specific to the target.
23167 When using @code{gdbserver} in this case, it does not exit unless it was
23168 invoked using the @option{--once} option. If the @option{--once} option
23169 was not used, you can ask @code{gdbserver} to exit using the
23170 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
23172 @item Specifying the program to debug
23173 For both connection types you use the @code{file} command to specify the
23174 program on the host system. If you are using @code{gdbserver} there are
23175 some differences in how to specify the location of the program on the
23178 @strong{With target remote mode:} You must either specify the program to debug
23179 on the @code{gdbserver} command line or use the @option{--attach} option
23180 (@pxref{Attaching to a program,,Attaching to a Running Program}).
23182 @cindex @option{--multi}, @code{gdbserver} option
23183 @strong{With target extended-remote mode:} You may specify the program to debug
23184 on the @code{gdbserver} command line, or you can load the program or attach
23185 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
23187 @anchor{--multi Option in Types of Remote Connnections}
23188 You can start @code{gdbserver} without supplying an initial command to run
23189 or process ID to attach. To do this, use the @option{--multi} command line
23190 option. Then you can connect using @code{target extended-remote} and start
23191 the program you want to debug (see below for details on using the
23192 @code{run} command in this scenario). Note that the conditions under which
23193 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
23194 (@code{target remote} or @code{target extended-remote}). The
23195 @option{--multi} option to @code{gdbserver} has no influence on that.
23197 @item The @code{run} command
23198 @strong{With target remote mode:} The @code{run} command is not
23199 supported. Once a connection has been established, you can use all
23200 the usual @value{GDBN} commands to examine and change data. The
23201 remote program is already running, so you can use commands like
23202 @kbd{step} and @kbd{continue}.
23204 @strong{With target extended-remote mode:} The @code{run} command is
23205 supported. The @code{run} command uses the value set by
23206 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
23207 the program to run. Command line arguments are supported, except for
23208 wildcard expansion and I/O redirection (@pxref{Arguments}).
23210 If you specify the program to debug on the command line, then the
23211 @code{run} command is not required to start execution, and you can
23212 resume using commands like @kbd{step} and @kbd{continue} as with
23213 @code{target remote} mode.
23215 @anchor{Attaching in Types of Remote Connections}
23217 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
23218 not supported. To attach to a running program using @code{gdbserver}, you
23219 must use the @option{--attach} option (@pxref{Running gdbserver}).
23221 @strong{With target extended-remote mode:} To attach to a running program,
23222 you may use the @code{attach} command after the connection has been
23223 established. If you are using @code{gdbserver}, you may also invoke
23224 @code{gdbserver} using the @option{--attach} option
23225 (@pxref{Running gdbserver}).
23227 Some remote targets allow @value{GDBN} to determine the executable file running
23228 in the process the debugger is attaching to. In such a case, @value{GDBN}
23229 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
23230 between the executable file name running in the process and the name of the
23231 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
23235 @anchor{Host and target files}
23236 @subsection Host and Target Files
23237 @cindex remote debugging, symbol files
23238 @cindex symbol files, remote debugging
23240 @value{GDBN}, running on the host, needs access to symbol and debugging
23241 information for your program running on the target. This requires
23242 access to an unstripped copy of your program, and possibly any associated
23243 symbol files. Note that this section applies equally to both @code{target
23244 remote} mode and @code{target extended-remote} mode.
23246 Some remote targets (@pxref{qXfer executable filename read}, and
23247 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
23248 the same connection used to communicate with @value{GDBN}. With such a
23249 target, if the remote program is unstripped, the only command you need is
23250 @code{target remote} (or @code{target extended-remote}).
23252 If the remote program is stripped, or the target does not support remote
23253 program file access, start up @value{GDBN} using the name of the local
23254 unstripped copy of your program as the first argument, or use the
23255 @code{file} command. Use @code{set sysroot} to specify the location (on
23256 the host) of target libraries (unless your @value{GDBN} was compiled with
23257 the correct sysroot using @code{--with-sysroot}). Alternatively, you
23258 may use @code{set solib-search-path} to specify how @value{GDBN} locates
23261 The symbol file and target libraries must exactly match the executable
23262 and libraries on the target, with one exception: the files on the host
23263 system should not be stripped, even if the files on the target system
23264 are. Mismatched or missing files will lead to confusing results
23265 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
23266 files may also prevent @code{gdbserver} from debugging multi-threaded
23269 @subsection Remote Connection Commands
23270 @cindex remote connection commands
23271 @value{GDBN} can communicate with the target over a serial line, a
23272 local Unix domain socket, or
23273 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
23274 each case, @value{GDBN} uses the same protocol for debugging your
23275 program; only the medium carrying the debugging packets varies. The
23276 @code{target remote} and @code{target extended-remote} commands
23277 establish a connection to the target. Both commands accept the same
23278 arguments, which indicate the medium to use:
23282 @item target remote @var{serial-device}
23283 @itemx target extended-remote @var{serial-device}
23284 @cindex serial line, @code{target remote}
23285 Use @var{serial-device} to communicate with the target. For example,
23286 to use a serial line connected to the device named @file{/dev/ttyb}:
23289 target remote /dev/ttyb
23292 If you're using a serial line, you may want to give @value{GDBN} the
23293 @samp{--baud} option, or use the @code{set serial baud} command
23294 (@pxref{Remote Configuration, set serial baud}) before the
23295 @code{target} command.
23297 @item target remote @var{local-socket}
23298 @itemx target extended-remote @var{local-socket}
23299 @cindex local socket, @code{target remote}
23300 @cindex Unix domain socket
23301 Use @var{local-socket} to communicate with the target. For example,
23302 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
23305 target remote /tmp/gdb-socket0
23308 Note that this command has the same form as the command to connect
23309 to a serial line. @value{GDBN} will automatically determine which
23310 kind of file you have specified and will make the appropriate kind
23312 This feature is not available if the host system does not support
23313 Unix domain sockets.
23315 @item target remote @code{@var{host}:@var{port}}
23316 @itemx target remote @code{[@var{host}]:@var{port}}
23317 @itemx target remote @code{tcp:@var{host}:@var{port}}
23318 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
23319 @itemx target remote @code{tcp4:@var{host}:@var{port}}
23320 @itemx target remote @code{tcp6:@var{host}:@var{port}}
23321 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
23322 @itemx target extended-remote @code{@var{host}:@var{port}}
23323 @itemx target extended-remote @code{[@var{host}]:@var{port}}
23324 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
23325 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
23326 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
23327 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
23328 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
23329 @cindex @acronym{TCP} port, @code{target remote}
23330 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
23331 The @var{host} may be either a host name, a numeric @acronym{IPv4}
23332 address, or a numeric @acronym{IPv6} address (with or without the
23333 square brackets to separate the address from the port); @var{port}
23334 must be a decimal number. The @var{host} could be the target machine
23335 itself, if it is directly connected to the net, or it might be a
23336 terminal server which in turn has a serial line to the target.
23338 For example, to connect to port 2828 on a terminal server named
23342 target remote manyfarms:2828
23345 To connect to port 2828 on a terminal server whose address is
23346 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
23347 square bracket syntax:
23350 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
23354 or explicitly specify the @acronym{IPv6} protocol:
23357 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
23360 This last example may be confusing to the reader, because there is no
23361 visible separation between the hostname and the port number.
23362 Therefore, we recommend the user to provide @acronym{IPv6} addresses
23363 using square brackets for clarity. However, it is important to
23364 mention that for @value{GDBN} there is no ambiguity: the number after
23365 the last colon is considered to be the port number.
23367 If your remote target is actually running on the same machine as your
23368 debugger session (e.g.@: a simulator for your target running on the
23369 same host), you can omit the hostname. For example, to connect to
23370 port 1234 on your local machine:
23373 target remote :1234
23377 Note that the colon is still required here.
23379 @item target remote @code{udp:@var{host}:@var{port}}
23380 @itemx target remote @code{udp:[@var{host}]:@var{port}}
23381 @itemx target remote @code{udp4:@var{host}:@var{port}}
23382 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
23383 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23384 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23385 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
23386 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
23387 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
23388 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
23389 @cindex @acronym{UDP} port, @code{target remote}
23390 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
23391 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
23394 target remote udp:manyfarms:2828
23397 When using a @acronym{UDP} connection for remote debugging, you should
23398 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
23399 can silently drop packets on busy or unreliable networks, which will
23400 cause havoc with your debugging session.
23402 @item target remote | @var{command}
23403 @itemx target extended-remote | @var{command}
23404 @cindex pipe, @code{target remote} to
23405 Run @var{command} in the background and communicate with it using a
23406 pipe. The @var{command} is a shell command, to be parsed and expanded
23407 by the system's command shell, @code{/bin/sh}; it should expect remote
23408 protocol packets on its standard input, and send replies on its
23409 standard output. You could use this to run a stand-alone simulator
23410 that speaks the remote debugging protocol, to make net connections
23411 using programs like @code{ssh}, or for other similar tricks.
23413 If @var{command} closes its standard output (perhaps by exiting),
23414 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
23415 program has already exited, this will have no effect.)
23419 @cindex interrupting remote programs
23420 @cindex remote programs, interrupting
23421 Whenever @value{GDBN} is waiting for the remote program, if you type the
23422 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
23423 program. This may or may not succeed, depending in part on the hardware
23424 and the serial drivers the remote system uses. If you type the
23425 interrupt character once again, @value{GDBN} displays this prompt:
23428 Interrupted while waiting for the program.
23429 Give up (and stop debugging it)? (y or n)
23432 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23433 the remote debugging session. (If you decide you want to try again later,
23434 you can use @kbd{target remote} again to connect once more.) If you type
23435 @kbd{n}, @value{GDBN} goes back to waiting.
23437 In @code{target extended-remote} mode, typing @kbd{n} will leave
23438 @value{GDBN} connected to the target.
23441 @kindex detach (remote)
23443 When you have finished debugging the remote program, you can use the
23444 @code{detach} command to release it from @value{GDBN} control.
23445 Detaching from the target normally resumes its execution, but the results
23446 will depend on your particular remote stub. After the @code{detach}
23447 command in @code{target remote} mode, @value{GDBN} is free to connect to
23448 another target. In @code{target extended-remote} mode, @value{GDBN} is
23449 still connected to the target.
23453 The @code{disconnect} command closes the connection to the target, and
23454 the target is generally not resumed. It will wait for @value{GDBN}
23455 (this instance or another one) to connect and continue debugging. After
23456 the @code{disconnect} command, @value{GDBN} is again free to connect to
23459 @cindex send command to remote monitor
23460 @cindex extend @value{GDBN} for remote targets
23461 @cindex add new commands for external monitor
23463 @item monitor @var{cmd}
23464 This command allows you to send arbitrary commands directly to the
23465 remote monitor. Since @value{GDBN} doesn't care about the commands it
23466 sends like this, this command is the way to extend @value{GDBN}---you
23467 can add new commands that only the external monitor will understand
23471 @node File Transfer
23472 @section Sending files to a remote system
23473 @cindex remote target, file transfer
23474 @cindex file transfer
23475 @cindex sending files to remote systems
23477 Some remote targets offer the ability to transfer files over the same
23478 connection used to communicate with @value{GDBN}. This is convenient
23479 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23480 running @code{gdbserver} over a network interface. For other targets,
23481 e.g.@: embedded devices with only a single serial port, this may be
23482 the only way to upload or download files.
23484 Not all remote targets support these commands.
23488 @item remote put @var{hostfile} @var{targetfile}
23489 Copy file @var{hostfile} from the host system (the machine running
23490 @value{GDBN}) to @var{targetfile} on the target system.
23493 @item remote get @var{targetfile} @var{hostfile}
23494 Copy file @var{targetfile} from the target system to @var{hostfile}
23495 on the host system.
23497 @kindex remote delete
23498 @item remote delete @var{targetfile}
23499 Delete @var{targetfile} from the target system.
23504 @section Using the @code{gdbserver} Program
23507 @cindex remote connection without stubs
23508 @code{gdbserver} is a control program for Unix-like systems, which
23509 allows you to connect your program with a remote @value{GDBN} via
23510 @code{target remote} or @code{target extended-remote}---but without
23511 linking in the usual debugging stub.
23513 @code{gdbserver} is not a complete replacement for the debugging stubs,
23514 because it requires essentially the same operating-system facilities
23515 that @value{GDBN} itself does. In fact, a system that can run
23516 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23517 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23518 because it is a much smaller program than @value{GDBN} itself. It is
23519 also easier to port than all of @value{GDBN}, so you may be able to get
23520 started more quickly on a new system by using @code{gdbserver}.
23521 Finally, if you develop code for real-time systems, you may find that
23522 the tradeoffs involved in real-time operation make it more convenient to
23523 do as much development work as possible on another system, for example
23524 by cross-compiling. You can use @code{gdbserver} to make a similar
23525 choice for debugging.
23527 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23528 or a TCP connection, using the standard @value{GDBN} remote serial
23532 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23533 Do not run @code{gdbserver} connected to any public network; a
23534 @value{GDBN} connection to @code{gdbserver} provides access to the
23535 target system with the same privileges as the user running
23539 @anchor{Running gdbserver}
23540 @subsection Running @code{gdbserver}
23541 @cindex arguments, to @code{gdbserver}
23542 @cindex @code{gdbserver}, command-line arguments
23544 Run @code{gdbserver} on the target system. You need a copy of the
23545 program you want to debug, including any libraries it requires.
23546 @code{gdbserver} does not need your program's symbol table, so you can
23547 strip the program if necessary to save space. @value{GDBN} on the host
23548 system does all the symbol handling.
23550 To use the server, you must tell it how to communicate with @value{GDBN};
23551 the name of your program; and the arguments for your program. The usual
23555 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23558 @var{comm} is either a device name (to use a serial line), or a TCP
23559 hostname and portnumber, or @code{-} or @code{stdio} to use
23560 stdin/stdout of @code{gdbserver}.
23561 For example, to debug Emacs with the argument
23562 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23566 target> gdbserver /dev/com1 emacs foo.txt
23569 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23572 To use a TCP connection instead of a serial line:
23575 target> gdbserver host:2345 emacs foo.txt
23578 The only difference from the previous example is the first argument,
23579 specifying that you are communicating with the host @value{GDBN} via
23580 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23581 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23582 (Currently, the @samp{host} part is ignored.) You can choose any number
23583 you want for the port number as long as it does not conflict with any
23584 TCP ports already in use on the target system (for example, @code{23} is
23585 reserved for @code{telnet}).@footnote{If you choose a port number that
23586 conflicts with another service, @code{gdbserver} prints an error message
23587 and exits.} You must use the same port number with the host @value{GDBN}
23588 @code{target remote} command.
23590 The @code{stdio} connection is useful when starting @code{gdbserver}
23594 (@value{GDBP}) target remote | ssh -T hostname gdbserver - hello
23597 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23598 and we don't want escape-character handling. Ssh does this by default when
23599 a command is provided, the flag is provided to make it explicit.
23600 You could elide it if you want to.
23602 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23603 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23604 display through a pipe connected to gdbserver.
23605 Both @code{stdout} and @code{stderr} use the same pipe.
23607 @anchor{Attaching to a program}
23608 @subsubsection Attaching to a Running Program
23609 @cindex attach to a program, @code{gdbserver}
23610 @cindex @option{--attach}, @code{gdbserver} option
23612 On some targets, @code{gdbserver} can also attach to running programs.
23613 This is accomplished via the @code{--attach} argument. The syntax is:
23616 target> gdbserver --attach @var{comm} @var{pid}
23619 @var{pid} is the process ID of a currently running process. It isn't
23620 necessary to point @code{gdbserver} at a binary for the running process.
23622 In @code{target extended-remote} mode, you can also attach using the
23623 @value{GDBN} attach command
23624 (@pxref{Attaching in Types of Remote Connections}).
23627 You can debug processes by name instead of process ID if your target has the
23628 @code{pidof} utility:
23631 target> gdbserver --attach @var{comm} `pidof @var{program}`
23634 In case more than one copy of @var{program} is running, or @var{program}
23635 has multiple threads, most versions of @code{pidof} support the
23636 @code{-s} option to only return the first process ID.
23638 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23640 This section applies only when @code{gdbserver} is run to listen on a TCP
23643 @code{gdbserver} normally terminates after all of its debugged processes have
23644 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23645 extended-remote}, @code{gdbserver} stays running even with no processes left.
23646 @value{GDBN} normally terminates the spawned debugged process on its exit,
23647 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23648 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23649 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23650 stays running even in the @kbd{target remote} mode.
23652 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23653 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23654 completeness, at most one @value{GDBN} can be connected at a time.
23656 @cindex @option{--once}, @code{gdbserver} option
23657 By default, @code{gdbserver} keeps the listening TCP port open, so that
23658 subsequent connections are possible. However, if you start @code{gdbserver}
23659 with the @option{--once} option, it will stop listening for any further
23660 connection attempts after connecting to the first @value{GDBN} session. This
23661 means no further connections to @code{gdbserver} will be possible after the
23662 first one. It also means @code{gdbserver} will terminate after the first
23663 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23664 connections and even in the @kbd{target extended-remote} mode. The
23665 @option{--once} option allows reusing the same port number for connecting to
23666 multiple instances of @code{gdbserver} running on the same host, since each
23667 instance closes its port after the first connection.
23669 @anchor{Other Command-Line Arguments for gdbserver}
23670 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23672 You can use the @option{--multi} option to start @code{gdbserver} without
23673 specifying a program to debug or a process to attach to. Then you can
23674 attach in @code{target extended-remote} mode and run or attach to a
23675 program. For more information,
23676 @pxref{--multi Option in Types of Remote Connnections}.
23678 @cindex @option{--debug}, @code{gdbserver} option
23679 The @option{--debug[=option1,option2,@dots{}]} option tells
23680 @code{gdbserver} to display extra diagnostic information about the
23681 debugging process. The options (@var{option1}, @var{option2}, etc)
23682 control for which areas of @code{gdbserver} additional information
23683 will be displayed, possible values are:
23687 This enables all available diagnostic output.
23689 This enables diagnostic output related to threading. Currently other
23690 general diagnostic output is included in this category, but this could
23691 change in future releases of @code{gdbserver}.
23693 This enables event-loop specific diagnostic output.
23695 This enables diagnostic output related to the transfer of remote
23696 protocol packets too and from the debugger.
23700 If no options are passed to @option{--debug} then this is treated as
23701 equivalent to @option{--debug=threads}. This could change in future
23702 releases of @code{gdbserver}. The options passed to @option{--debug}
23703 are processed left to right, and individual options can be prefixed
23704 with the @kbd{-} (minus) character to disable diagnostic output from
23705 this area, so it is possible to use:
23708 target> gdbserver --debug=all,-event-loop
23712 In order to enable all diagnostic output except that for the
23715 @cindex @option{--debug-file}, @code{gdbserver} option
23716 @cindex @code{gdbserver}, send all debug output to a single file
23717 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23718 write any debug output to the given @var{filename}. These options are intended
23719 for @code{gdbserver} development and for bug reports to the developers.
23721 @cindex @option{--debug-format}, @code{gdbserver} option
23722 The @option{--debug-format=option1[,option2,...]} option tells
23723 @code{gdbserver} to include additional information in each output.
23724 Possible options are:
23728 Turn off all extra information in debugging output.
23730 Turn on all extra information in debugging output.
23732 Include a timestamp in each line of debugging output.
23735 Options are processed in order. Thus, for example, if @option{none}
23736 appears last then no additional information is added to debugging output.
23738 @cindex @option{--wrapper}, @code{gdbserver} option
23739 The @option{--wrapper} option specifies a wrapper to launch programs
23740 for debugging. The option should be followed by the name of the
23741 wrapper, then any command-line arguments to pass to the wrapper, then
23742 @kbd{--} indicating the end of the wrapper arguments.
23744 @code{gdbserver} runs the specified wrapper program with a combined
23745 command line including the wrapper arguments, then the name of the
23746 program to debug, then any arguments to the program. The wrapper
23747 runs until it executes your program, and then @value{GDBN} gains control.
23749 You can use any program that eventually calls @code{execve} with
23750 its arguments as a wrapper. Several standard Unix utilities do
23751 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23752 with @code{exec "$@@"} will also work.
23754 For example, you can use @code{env} to pass an environment variable to
23755 the debugged program, without setting the variable in @code{gdbserver}'s
23759 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23762 @cindex @option{--selftest}
23763 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23766 $ gdbserver --selftest
23767 Ran 2 unit tests, 0 failed
23770 These tests are disabled in release.
23771 @subsection Connecting to @code{gdbserver}
23773 The basic procedure for connecting to the remote target is:
23777 Run @value{GDBN} on the host system.
23780 Make sure you have the necessary symbol files
23781 (@pxref{Host and target files}).
23782 Load symbols for your application using the @code{file} command before you
23783 connect. Use @code{set sysroot} to locate target libraries (unless your
23784 @value{GDBN} was compiled with the correct sysroot using
23785 @code{--with-sysroot}).
23788 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23789 For TCP connections, you must start up @code{gdbserver} prior to using
23790 the @code{target} command. Otherwise you may get an error whose
23791 text depends on the host system, but which usually looks something like
23792 @samp{Connection refused}. Don't use the @code{load}
23793 command in @value{GDBN} when using @code{target remote} mode, since the
23794 program is already on the target.
23798 @anchor{Monitor Commands for gdbserver}
23799 @subsection Monitor Commands for @code{gdbserver}
23800 @cindex monitor commands, for @code{gdbserver}
23802 During a @value{GDBN} session using @code{gdbserver}, you can use the
23803 @code{monitor} command to send special requests to @code{gdbserver}.
23804 Here are the available commands.
23808 List the available monitor commands.
23810 @item monitor set debug off
23811 Disable all internal logging from gdbserver.
23813 @item monitor set debug on
23814 Enable some general logging from within gdbserver. Currently this is
23815 equivalent to @kbd{monitor set debug threads on}, but this might
23816 change in future releases of gdbserver.
23818 @item monitor set debug threads off
23819 @itemx monitor set debug threads on
23820 Disable or enable specific logging messages associated with thread
23821 handling in gdbserver. Currently this category also includes
23822 additional output not specifically related to thread handling, this
23823 could change in future releases of gdbserver.
23825 @item monitor set debug remote off
23826 @itemx monitor set debug remote on
23827 Disable or enable specific logging messages associated with the remote
23828 protocol (@pxref{Remote Protocol}).
23830 @item monitor set debug event-loop off
23831 @itemx monitor set debug event-loop on
23832 Disable or enable specific logging messages associated with
23833 gdbserver's event-loop.
23835 @item monitor set debug-file filename
23836 @itemx monitor set debug-file
23837 Send any debug output to the given file, or to stderr.
23839 @item monitor set debug-format option1@r{[},option2,...@r{]}
23840 Specify additional text to add to debugging messages.
23841 Possible options are:
23845 Turn off all extra information in debugging output.
23847 Turn on all extra information in debugging output.
23849 Include a timestamp in each line of debugging output.
23852 Options are processed in order. Thus, for example, if @option{none}
23853 appears last then no additional information is added to debugging output.
23855 @item monitor set libthread-db-search-path [PATH]
23856 @cindex gdbserver, search path for @code{libthread_db}
23857 When this command is issued, @var{path} is a colon-separated list of
23858 directories to search for @code{libthread_db} (@pxref{Threads,,set
23859 libthread-db-search-path}). If you omit @var{path},
23860 @samp{libthread-db-search-path} will be reset to its default value.
23862 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23863 not supported in @code{gdbserver}.
23866 Tell gdbserver to exit immediately. This command should be followed by
23867 @code{disconnect} to close the debugging session. @code{gdbserver} will
23868 detach from any attached processes and kill any processes it created.
23869 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23870 of a multi-process mode debug session.
23874 @subsection Tracepoints support in @code{gdbserver}
23875 @cindex tracepoints support in @code{gdbserver}
23877 On some targets, @code{gdbserver} supports tracepoints, fast
23878 tracepoints and static tracepoints.
23880 For fast or static tracepoints to work, a special library called the
23881 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23882 This library is built and distributed as an integral part of
23883 @code{gdbserver}. In addition, support for static tracepoints
23884 requires building the in-process agent library with static tracepoints
23885 support. At present, the UST (LTTng Userspace Tracer,
23886 @url{http://lttng.org/ust}) tracing engine is supported. This support
23887 is automatically available if UST development headers are found in the
23888 standard include path when @code{gdbserver} is built, or if
23889 @code{gdbserver} was explicitly configured using @option{--with-ust}
23890 to point at such headers. You can explicitly disable the support
23891 using @option{--with-ust=no}.
23893 There are several ways to load the in-process agent in your program:
23896 @item Specifying it as dependency at link time
23898 You can link your program dynamically with the in-process agent
23899 library. On most systems, this is accomplished by adding
23900 @code{-linproctrace} to the link command.
23902 @item Using the system's preloading mechanisms
23904 You can force loading the in-process agent at startup time by using
23905 your system's support for preloading shared libraries. Many Unixes
23906 support the concept of preloading user defined libraries. In most
23907 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23908 in the environment. See also the description of @code{gdbserver}'s
23909 @option{--wrapper} command line option.
23911 @item Using @value{GDBN} to force loading the agent at run time
23913 On some systems, you can force the inferior to load a shared library,
23914 by calling a dynamic loader function in the inferior that takes care
23915 of dynamically looking up and loading a shared library. On most Unix
23916 systems, the function is @code{dlopen}. You'll use the @code{call}
23917 command for that. For example:
23920 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23923 Note that on most Unix systems, for the @code{dlopen} function to be
23924 available, the program needs to be linked with @code{-ldl}.
23927 On systems that have a userspace dynamic loader, like most Unix
23928 systems, when you connect to @code{gdbserver} using @code{target
23929 remote}, you'll find that the program is stopped at the dynamic
23930 loader's entry point, and no shared library has been loaded in the
23931 program's address space yet, including the in-process agent. In that
23932 case, before being able to use any of the fast or static tracepoints
23933 features, you need to let the loader run and load the shared
23934 libraries. The simplest way to do that is to run the program to the
23935 main procedure. E.g., if debugging a C or C@t{++} program, start
23936 @code{gdbserver} like so:
23939 $ gdbserver :9999 myprogram
23942 Start GDB and connect to @code{gdbserver} like so, and run to main:
23946 (@value{GDBP}) target remote myhost:9999
23947 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23948 (@value{GDBP}) b main
23949 (@value{GDBP}) continue
23952 The in-process tracing agent library should now be loaded into the
23953 process; you can confirm it with the @code{info sharedlibrary}
23954 command, which will list @file{libinproctrace.so} as loaded in the
23955 process. You are now ready to install fast tracepoints, list static
23956 tracepoint markers, probe static tracepoints markers, and start
23959 @node Remote Configuration
23960 @section Remote Configuration
23963 @kindex show remote
23964 This section documents the configuration options available when
23965 debugging remote programs. For the options related to the File I/O
23966 extensions of the remote protocol, see @ref{system,
23967 system-call-allowed}.
23970 @item set remoteaddresssize @var{bits}
23971 @cindex address size for remote targets
23972 @cindex bits in remote address
23973 Set the maximum size of address in a memory packet to the specified
23974 number of bits. @value{GDBN} will mask off the address bits above
23975 that number, when it passes addresses to the remote target. The
23976 default value is the number of bits in the target's address.
23978 @item show remoteaddresssize
23979 Show the current value of remote address size in bits.
23981 @item set serial baud @var{n}
23982 @cindex baud rate for remote targets
23983 Set the baud rate for the remote serial I/O to @var{n} baud. The
23984 value is used to set the speed of the serial port used for debugging
23987 @item show serial baud
23988 Show the current speed of the remote connection.
23990 @item set serial parity @var{parity}
23991 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23992 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23994 @item show serial parity
23995 Show the current parity of the serial port.
23997 @item set remotebreak
23998 @cindex interrupt remote programs
23999 @cindex BREAK signal instead of Ctrl-C
24000 @anchor{set remotebreak}
24001 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
24002 when you type @kbd{Ctrl-c} to interrupt the program running
24003 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
24004 character instead. The default is off, since most remote systems
24005 expect to see @samp{Ctrl-C} as the interrupt signal.
24007 @item show remotebreak
24008 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
24009 interrupt the remote program.
24011 @item set remoteflow on
24012 @itemx set remoteflow off
24013 @kindex set remoteflow
24014 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
24015 on the serial port used to communicate to the remote target.
24017 @item show remoteflow
24018 @kindex show remoteflow
24019 Show the current setting of hardware flow control.
24021 @item set remotelogbase @var{base}
24022 Set the base (a.k.a.@: radix) of logging serial protocol
24023 communications to @var{base}. Supported values of @var{base} are:
24024 @code{ascii}, @code{octal}, and @code{hex}. The default is
24027 @item show remotelogbase
24028 Show the current setting of the radix for logging remote serial
24031 @item set remotelogfile @var{file}
24032 @cindex record serial communications on file
24033 Record remote serial communications on the named @var{file}. The
24034 default is not to record at all.
24036 @item show remotelogfile
24037 Show the current setting of the file name on which to record the
24038 serial communications.
24040 @item set remotetimeout @var{num}
24041 @cindex timeout for serial communications
24042 @cindex remote timeout
24043 Set the timeout limit to wait for the remote target to respond to
24044 @var{num} seconds. The default is 2 seconds.
24046 @item show remotetimeout
24047 Show the current number of seconds to wait for the remote target
24050 @cindex limit hardware breakpoints and watchpoints
24051 @cindex remote target, limit break- and watchpoints
24052 @anchor{set remote hardware-watchpoint-limit}
24053 @anchor{set remote hardware-breakpoint-limit}
24054 @item set remote hardware-watchpoint-limit @var{limit}
24055 @itemx set remote hardware-breakpoint-limit @var{limit}
24056 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
24057 or breakpoints. The @var{limit} can be set to 0 to disable hardware
24058 watchpoints or breakpoints, and @code{unlimited} for unlimited
24059 watchpoints or breakpoints.
24061 @item show remote hardware-watchpoint-limit
24062 @itemx show remote hardware-breakpoint-limit
24063 Show the current limit for the number of hardware watchpoints or
24064 breakpoints that @value{GDBN} can use.
24066 @cindex limit hardware watchpoints length
24067 @cindex remote target, limit watchpoints length
24068 @anchor{set remote hardware-watchpoint-length-limit}
24069 @item set remote hardware-watchpoint-length-limit @var{limit}
24070 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
24071 length of a remote hardware watchpoint. A @var{limit} of 0 disables
24072 hardware watchpoints and @code{unlimited} allows watchpoints of any
24075 @item show remote hardware-watchpoint-length-limit
24076 Show the current limit (in bytes) of the maximum length of
24077 a remote hardware watchpoint.
24079 @item set remote exec-file @var{filename}
24080 @itemx show remote exec-file
24081 @anchor{set remote exec-file}
24082 @cindex executable file, for remote target
24083 Select the file used for @code{run} with @code{target
24084 extended-remote}. This should be set to a filename valid on the
24085 target system. If it is not set, the target will use a default
24086 filename (e.g.@: the last program run).
24088 @item set remote interrupt-sequence
24089 @cindex interrupt remote programs
24090 @cindex select Ctrl-C, BREAK or BREAK-g
24091 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
24092 @samp{BREAK-g} as the
24093 sequence to the remote target in order to interrupt the execution.
24094 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
24095 is high level of serial line for some certain time.
24096 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
24097 It is @code{BREAK} signal followed by character @code{g}.
24099 @item show remote interrupt-sequence
24100 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
24101 is sent by @value{GDBN} to interrupt the remote program.
24102 @code{BREAK-g} is BREAK signal followed by @code{g} and
24103 also known as Magic SysRq g.
24105 @item set remote interrupt-on-connect
24106 @cindex send interrupt-sequence on start
24107 Specify whether interrupt-sequence is sent to remote target when
24108 @value{GDBN} connects to it. This is mostly needed when you debug
24109 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
24110 which is known as Magic SysRq g in order to connect @value{GDBN}.
24112 @item show remote interrupt-on-connect
24113 Show whether interrupt-sequence is sent
24114 to remote target when @value{GDBN} connects to it.
24118 @item set tcp auto-retry on
24119 @cindex auto-retry, for remote TCP target
24120 Enable auto-retry for remote TCP connections. This is useful if the remote
24121 debugging agent is launched in parallel with @value{GDBN}; there is a race
24122 condition because the agent may not become ready to accept the connection
24123 before @value{GDBN} attempts to connect. When auto-retry is
24124 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
24125 to establish the connection using the timeout specified by
24126 @code{set tcp connect-timeout}.
24128 @item set tcp auto-retry off
24129 Do not auto-retry failed TCP connections.
24131 @item show tcp auto-retry
24132 Show the current auto-retry setting.
24134 @item set tcp connect-timeout @var{seconds}
24135 @itemx set tcp connect-timeout unlimited
24136 @cindex connection timeout, for remote TCP target
24137 @cindex timeout, for remote target connection
24138 Set the timeout for establishing a TCP connection to the remote target to
24139 @var{seconds}. The timeout affects both polling to retry failed connections
24140 (enabled by @code{set tcp auto-retry on}) and waiting for connections
24141 that are merely slow to complete, and represents an approximate cumulative
24142 value. If @var{seconds} is @code{unlimited}, there is no timeout and
24143 @value{GDBN} will keep attempting to establish a connection forever,
24144 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
24146 @item show tcp connect-timeout
24147 Show the current connection timeout setting.
24150 @cindex remote packets, enabling and disabling
24151 The @value{GDBN} remote protocol autodetects the packets supported by
24152 your debugging stub. If you need to override the autodetection, you
24153 can use these commands to enable or disable individual packets. Each
24154 packet can be set to @samp{on} (the remote target supports this
24155 packet), @samp{off} (the remote target does not support this packet),
24156 or @samp{auto} (detect remote target support for this packet). They
24157 all default to @samp{auto}. For more information about each packet,
24158 see @ref{Remote Protocol}.
24160 During normal use, you should not have to use any of these commands.
24161 If you do, that may be a bug in your remote debugging stub, or a bug
24162 in @value{GDBN}. You may want to report the problem to the
24163 @value{GDBN} developers.
24165 For each packet @var{name}, the command to enable or disable the
24166 packet is @code{set remote @var{name}-packet}. If you configure a packet, the
24167 configuration will apply for all future remote targets if no target is selected.
24168 In case there is a target selected, only the configuration of the current target
24169 is changed. All other existing remote targets' features are not affected.
24170 The command to print the current configuration of a packet is
24171 @code{show remote @var{name}-packet}. It displays the current remote target's
24172 configuration. If no remote target is selected, the default configuration for
24173 future connections is shown. The available settings are:
24175 @multitable @columnfractions 0.28 0.32 0.25
24178 @tab Related Features
24180 @item @code{fetch-register}
24182 @tab @code{info registers}
24184 @item @code{set-register}
24188 @item @code{binary-download}
24190 @tab @code{load}, @code{set}
24192 @item @code{read-aux-vector}
24193 @tab @code{qXfer:auxv:read}
24194 @tab @code{info auxv}
24196 @item @code{symbol-lookup}
24197 @tab @code{qSymbol}
24198 @tab Detecting multiple threads
24200 @item @code{attach}
24201 @tab @code{vAttach}
24204 @item @code{verbose-resume}
24206 @tab Stepping or resuming multiple threads
24212 @item @code{software-breakpoint}
24216 @item @code{hardware-breakpoint}
24220 @item @code{write-watchpoint}
24224 @item @code{read-watchpoint}
24228 @item @code{access-watchpoint}
24232 @item @code{pid-to-exec-file}
24233 @tab @code{qXfer:exec-file:read}
24234 @tab @code{attach}, @code{run}
24236 @item @code{target-features}
24237 @tab @code{qXfer:features:read}
24238 @tab @code{set architecture}
24240 @item @code{library-info}
24241 @tab @code{qXfer:libraries:read}
24242 @tab @code{info sharedlibrary}
24244 @item @code{memory-map}
24245 @tab @code{qXfer:memory-map:read}
24246 @tab @code{info mem}
24248 @item @code{read-sdata-object}
24249 @tab @code{qXfer:sdata:read}
24250 @tab @code{print $_sdata}
24252 @item @code{read-siginfo-object}
24253 @tab @code{qXfer:siginfo:read}
24254 @tab @code{print $_siginfo}
24256 @item @code{write-siginfo-object}
24257 @tab @code{qXfer:siginfo:write}
24258 @tab @code{set $_siginfo}
24260 @item @code{threads}
24261 @tab @code{qXfer:threads:read}
24262 @tab @code{info threads}
24264 @item @code{get-thread-local-@*storage-address}
24265 @tab @code{qGetTLSAddr}
24266 @tab Displaying @code{__thread} variables
24268 @item @code{get-thread-information-block-address}
24269 @tab @code{qGetTIBAddr}
24270 @tab Display MS-Windows Thread Information Block.
24272 @item @code{search-memory}
24273 @tab @code{qSearch:memory}
24276 @item @code{supported-packets}
24277 @tab @code{qSupported}
24278 @tab Remote communications parameters
24280 @item @code{catch-syscalls}
24281 @tab @code{QCatchSyscalls}
24282 @tab @code{catch syscall}
24284 @item @code{pass-signals}
24285 @tab @code{QPassSignals}
24286 @tab @code{handle @var{signal}}
24288 @item @code{program-signals}
24289 @tab @code{QProgramSignals}
24290 @tab @code{handle @var{signal}}
24292 @item @code{hostio-close-packet}
24293 @tab @code{vFile:close}
24294 @tab @code{remote get}, @code{remote put}
24296 @item @code{hostio-open-packet}
24297 @tab @code{vFile:open}
24298 @tab @code{remote get}, @code{remote put}
24300 @item @code{hostio-pread-packet}
24301 @tab @code{vFile:pread}
24302 @tab @code{remote get}, @code{remote put}
24304 @item @code{hostio-pwrite-packet}
24305 @tab @code{vFile:pwrite}
24306 @tab @code{remote get}, @code{remote put}
24308 @item @code{hostio-unlink-packet}
24309 @tab @code{vFile:unlink}
24310 @tab @code{remote delete}
24312 @item @code{hostio-readlink-packet}
24313 @tab @code{vFile:readlink}
24316 @item @code{hostio-fstat-packet}
24317 @tab @code{vFile:fstat}
24320 @item @code{hostio-setfs-packet}
24321 @tab @code{vFile:setfs}
24324 @item @code{noack-packet}
24325 @tab @code{QStartNoAckMode}
24326 @tab Packet acknowledgment
24328 @item @code{osdata}
24329 @tab @code{qXfer:osdata:read}
24330 @tab @code{info os}
24332 @item @code{query-attached}
24333 @tab @code{qAttached}
24334 @tab Querying remote process attach state.
24336 @item @code{trace-buffer-size}
24337 @tab @code{QTBuffer:size}
24338 @tab @code{set trace-buffer-size}
24340 @item @code{trace-status}
24341 @tab @code{qTStatus}
24342 @tab @code{tstatus}
24344 @item @code{traceframe-info}
24345 @tab @code{qXfer:traceframe-info:read}
24346 @tab Traceframe info
24348 @item @code{install-in-trace}
24349 @tab @code{InstallInTrace}
24350 @tab Install tracepoint in tracing
24352 @item @code{disable-randomization}
24353 @tab @code{QDisableRandomization}
24354 @tab @code{set disable-randomization}
24356 @item @code{startup-with-shell}
24357 @tab @code{QStartupWithShell}
24358 @tab @code{set startup-with-shell}
24360 @item @code{environment-hex-encoded}
24361 @tab @code{QEnvironmentHexEncoded}
24362 @tab @code{set environment}
24364 @item @code{environment-unset}
24365 @tab @code{QEnvironmentUnset}
24366 @tab @code{unset environment}
24368 @item @code{environment-reset}
24369 @tab @code{QEnvironmentReset}
24370 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
24372 @item @code{set-working-dir}
24373 @tab @code{QSetWorkingDir}
24374 @tab @code{set cwd}
24376 @item @code{conditional-breakpoints-packet}
24377 @tab @code{Z0 and Z1}
24378 @tab @code{Support for target-side breakpoint condition evaluation}
24380 @item @code{multiprocess-extensions}
24381 @tab @code{multiprocess extensions}
24382 @tab Debug multiple processes and remote process PID awareness
24384 @item @code{swbreak-feature}
24385 @tab @code{swbreak stop reason}
24388 @item @code{hwbreak-feature}
24389 @tab @code{hwbreak stop reason}
24392 @item @code{fork-event-feature}
24393 @tab @code{fork stop reason}
24396 @item @code{vfork-event-feature}
24397 @tab @code{vfork stop reason}
24400 @item @code{exec-event-feature}
24401 @tab @code{exec stop reason}
24404 @item @code{thread-events}
24405 @tab @code{QThreadEvents}
24406 @tab Tracking thread lifetime.
24408 @item @code{thread-options}
24409 @tab @code{QThreadOptions}
24410 @tab Set thread event reporting options.
24412 @item @code{no-resumed-stop-reply}
24413 @tab @code{no resumed thread left stop reply}
24414 @tab Tracking thread lifetime.
24418 @cindex packet size, remote, configuring
24419 The number of bytes per memory-read or memory-write packet for a remote target
24420 can be configured using the commands
24421 @w{@code{set remote memory-read-packet-size}} and
24422 @w{@code{set remote memory-write-packet-size}}. If set to @samp{0} (zero) the
24423 default packet size will be used. The actual limit is further reduced depending
24424 on the target. Specify @samp{fixed} to disable the target-dependent restriction
24425 and @samp{limit} to enable it. Similar to the enabling and disabling of remote
24426 packets, the command applies to the currently selected target (if available).
24427 If no remote target is selected, it applies to all future remote connections.
24428 The configuration of the selected target can be displayed using the commands
24429 @w{@code{show remote memory-read-packet-size}} and
24430 @w{@code{show remote memory-write-packet-size}}. If no remote target is
24431 selected, the default configuration for future connections is shown.
24434 @section Implementing a Remote Stub
24436 @cindex debugging stub, example
24437 @cindex remote stub, example
24438 @cindex stub example, remote debugging
24439 The stub files provided with @value{GDBN} implement the target side of the
24440 communication protocol, and the @value{GDBN} side is implemented in the
24441 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
24442 these subroutines to communicate, and ignore the details. (If you're
24443 implementing your own stub file, you can still ignore the details: start
24444 with one of the existing stub files. @file{sparc-stub.c} is the best
24445 organized, and therefore the easiest to read.)
24447 @cindex remote serial debugging, overview
24448 To debug a program running on another machine (the debugging
24449 @dfn{target} machine), you must first arrange for all the usual
24450 prerequisites for the program to run by itself. For example, for a C
24455 A startup routine to set up the C runtime environment; these usually
24456 have a name like @file{crt0}. The startup routine may be supplied by
24457 your hardware supplier, or you may have to write your own.
24460 A C subroutine library to support your program's
24461 subroutine calls, notably managing input and output.
24464 A way of getting your program to the other machine---for example, a
24465 download program. These are often supplied by the hardware
24466 manufacturer, but you may have to write your own from hardware
24470 The next step is to arrange for your program to use a serial port to
24471 communicate with the machine where @value{GDBN} is running (the @dfn{host}
24472 machine). In general terms, the scheme looks like this:
24476 @value{GDBN} already understands how to use this protocol; when everything
24477 else is set up, you can simply use the @samp{target remote} command
24478 (@pxref{Targets,,Specifying a Debugging Target}).
24480 @item On the target,
24481 you must link with your program a few special-purpose subroutines that
24482 implement the @value{GDBN} remote serial protocol. The file containing these
24483 subroutines is called a @dfn{debugging stub}.
24485 On certain remote targets, you can use an auxiliary program
24486 @code{gdbserver} instead of linking a stub into your program.
24487 @xref{Server,,Using the @code{gdbserver} Program}, for details.
24490 The debugging stub is specific to the architecture of the remote
24491 machine; for example, use @file{sparc-stub.c} to debug programs on
24494 @cindex remote serial stub list
24495 These working remote stubs are distributed with @value{GDBN}:
24500 @cindex @file{i386-stub.c}
24503 For Intel 386 and compatible architectures.
24506 @cindex @file{m68k-stub.c}
24507 @cindex Motorola 680x0
24509 For Motorola 680x0 architectures.
24512 @cindex @file{sh-stub.c}
24515 For Renesas SH architectures.
24518 @cindex @file{sparc-stub.c}
24520 For @sc{sparc} architectures.
24522 @item sparcl-stub.c
24523 @cindex @file{sparcl-stub.c}
24526 For Fujitsu @sc{sparclite} architectures.
24530 The @file{README} file in the @value{GDBN} distribution may list other
24531 recently added stubs.
24534 * Stub Contents:: What the stub can do for you
24535 * Bootstrapping:: What you must do for the stub
24536 * Debug Session:: Putting it all together
24539 @node Stub Contents
24540 @subsection What the Stub Can Do for You
24542 @cindex remote serial stub
24543 The debugging stub for your architecture supplies these three
24547 @findex set_debug_traps
24548 @item set_debug_traps
24549 @cindex remote serial stub, initialization
24550 This routine arranges for @code{handle_exception} to run when your
24551 program stops. You must call this subroutine explicitly in your
24552 program's startup code.
24554 @findex handle_exception
24555 @item handle_exception
24556 @cindex remote serial stub, main routine
24557 This is the central workhorse, but your program never calls it
24558 explicitly---the setup code arranges for @code{handle_exception} to
24559 run when a trap is triggered.
24561 @code{handle_exception} takes control when your program stops during
24562 execution (for example, on a breakpoint), and mediates communications
24563 with @value{GDBN} on the host machine. This is where the communications
24564 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24565 representative on the target machine. It begins by sending summary
24566 information on the state of your program, then continues to execute,
24567 retrieving and transmitting any information @value{GDBN} needs, until you
24568 execute a @value{GDBN} command that makes your program resume; at that point,
24569 @code{handle_exception} returns control to your own code on the target
24573 @cindex @code{breakpoint} subroutine, remote
24574 Use this auxiliary subroutine to make your program contain a
24575 breakpoint. Depending on the particular situation, this may be the only
24576 way for @value{GDBN} to get control. For instance, if your target
24577 machine has some sort of interrupt button, you won't need to call this;
24578 pressing the interrupt button transfers control to
24579 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24580 simply receiving characters on the serial port may also trigger a trap;
24581 again, in that situation, you don't need to call @code{breakpoint} from
24582 your own program---simply running @samp{target remote} from the host
24583 @value{GDBN} session gets control.
24585 Call @code{breakpoint} if none of these is true, or if you simply want
24586 to make certain your program stops at a predetermined point for the
24587 start of your debugging session.
24590 @node Bootstrapping
24591 @subsection What You Must Do for the Stub
24593 @cindex remote stub, support routines
24594 The debugging stubs that come with @value{GDBN} are set up for a particular
24595 chip architecture, but they have no information about the rest of your
24596 debugging target machine.
24598 First of all you need to tell the stub how to communicate with the
24602 @findex getDebugChar
24603 @item int getDebugChar()
24604 Write this subroutine to read a single character from the serial port.
24605 It may be identical to @code{getchar} for your target system; a
24606 different name is used to allow you to distinguish the two if you wish.
24608 @findex putDebugChar
24609 @item void putDebugChar(int)
24610 Write this subroutine to write a single character to the serial port.
24611 It may be identical to @code{putchar} for your target system; a
24612 different name is used to allow you to distinguish the two if you wish.
24615 @cindex control C, and remote debugging
24616 @cindex interrupting remote targets
24617 If you want @value{GDBN} to be able to stop your program while it is
24618 running, you need to use an interrupt-driven serial driver, and arrange
24619 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24620 character). That is the character which @value{GDBN} uses to tell the
24621 remote system to stop.
24623 Getting the debugging target to return the proper status to @value{GDBN}
24624 probably requires changes to the standard stub; one quick and dirty way
24625 is to just execute a breakpoint instruction (the ``dirty'' part is that
24626 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24628 Other routines you need to supply are:
24631 @findex exceptionHandler
24632 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24633 Write this function to install @var{exception_address} in the exception
24634 handling tables. You need to do this because the stub does not have any
24635 way of knowing what the exception handling tables on your target system
24636 are like (for example, the processor's table might be in @sc{rom},
24637 containing entries which point to a table in @sc{ram}).
24638 The @var{exception_number} specifies the exception which should be changed;
24639 its meaning is architecture-dependent (for example, different numbers
24640 might represent divide by zero, misaligned access, etc). When this
24641 exception occurs, control should be transferred directly to
24642 @var{exception_address}, and the processor state (stack, registers,
24643 and so on) should be just as it is when a processor exception occurs. So if
24644 you want to use a jump instruction to reach @var{exception_address}, it
24645 should be a simple jump, not a jump to subroutine.
24647 For the 386, @var{exception_address} should be installed as an interrupt
24648 gate so that interrupts are masked while the handler runs. The gate
24649 should be at privilege level 0 (the most privileged level). The
24650 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24651 help from @code{exceptionHandler}.
24653 @findex flush_i_cache
24654 @item void flush_i_cache()
24655 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24656 instruction cache, if any, on your target machine. If there is no
24657 instruction cache, this subroutine may be a no-op.
24659 On target machines that have instruction caches, @value{GDBN} requires this
24660 function to make certain that the state of your program is stable.
24664 You must also make sure this library routine is available:
24668 @item void *memset(void *, int, int)
24669 This is the standard library function @code{memset} that sets an area of
24670 memory to a known value. If you have one of the free versions of
24671 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24672 either obtain it from your hardware manufacturer, or write your own.
24675 If you do not use the GNU C compiler, you may need other standard
24676 library subroutines as well; this varies from one stub to another,
24677 but in general the stubs are likely to use any of the common library
24678 subroutines which @code{@value{NGCC}} generates as inline code.
24681 @node Debug Session
24682 @subsection Putting it All Together
24684 @cindex remote serial debugging summary
24685 In summary, when your program is ready to debug, you must follow these
24690 Make sure you have defined the supporting low-level routines
24691 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24693 @code{getDebugChar}, @code{putDebugChar},
24694 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24698 Insert these lines in your program's startup code, before the main
24699 procedure is called:
24706 On some machines, when a breakpoint trap is raised, the hardware
24707 automatically makes the PC point to the instruction after the
24708 breakpoint. If your machine doesn't do that, you may need to adjust
24709 @code{handle_exception} to arrange for it to return to the instruction
24710 after the breakpoint on this first invocation, so that your program
24711 doesn't keep hitting the initial breakpoint instead of making
24715 For the 680x0 stub only, you need to provide a variable called
24716 @code{exceptionHook}. Normally you just use:
24719 void (*exceptionHook)() = 0;
24723 but if before calling @code{set_debug_traps}, you set it to point to a
24724 function in your program, that function is called when
24725 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24726 error). The function indicated by @code{exceptionHook} is called with
24727 one parameter: an @code{int} which is the exception number.
24730 Compile and link together: your program, the @value{GDBN} debugging stub for
24731 your target architecture, and the supporting subroutines.
24734 Make sure you have a serial connection between your target machine and
24735 the @value{GDBN} host, and identify the serial port on the host.
24738 @c The "remote" target now provides a `load' command, so we should
24739 @c document that. FIXME.
24740 Download your program to your target machine (or get it there by
24741 whatever means the manufacturer provides), and start it.
24744 Start @value{GDBN} on the host, and connect to the target
24745 (@pxref{Connecting,,Connecting to a Remote Target}).
24749 @node Configurations
24750 @chapter Configuration-Specific Information
24752 While nearly all @value{GDBN} commands are available for all native and
24753 cross versions of the debugger, there are some exceptions. This chapter
24754 describes things that are only available in certain configurations.
24756 There are three major categories of configurations: native
24757 configurations, where the host and target are the same, embedded
24758 operating system configurations, which are usually the same for several
24759 different processor architectures, and bare embedded processors, which
24760 are quite different from each other.
24765 * Embedded Processors::
24772 This section describes details specific to particular native
24776 * BSD libkvm Interface:: Debugging BSD kernel memory images
24777 * Process Information:: Process information
24778 * DJGPP Native:: Features specific to the DJGPP port
24779 * Cygwin Native:: Features specific to the Cygwin port
24780 * Hurd Native:: Features specific to @sc{gnu} Hurd
24781 * Darwin:: Features specific to Darwin
24782 * FreeBSD:: Features specific to FreeBSD
24785 @node BSD libkvm Interface
24786 @subsection BSD libkvm Interface
24789 @cindex kernel memory image
24790 @cindex kernel crash dump
24792 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24793 interface that provides a uniform interface for accessing kernel virtual
24794 memory images, including live systems and crash dumps. @value{GDBN}
24795 uses this interface to allow you to debug live kernels and kernel crash
24796 dumps on many native BSD configurations. This is implemented as a
24797 special @code{kvm} debugging target. For debugging a live system, load
24798 the currently running kernel into @value{GDBN} and connect to the
24802 (@value{GDBP}) @b{target kvm}
24805 For debugging crash dumps, provide the file name of the crash dump as an
24809 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24812 Once connected to the @code{kvm} target, the following commands are
24818 Set current context from the @dfn{Process Control Block} (PCB) address.
24821 Set current context from proc address. This command isn't available on
24822 modern FreeBSD systems.
24825 @node Process Information
24826 @subsection Process Information
24828 @cindex examine process image
24829 @cindex process info via @file{/proc}
24831 Some operating systems provide interfaces to fetch additional
24832 information about running processes beyond memory and per-thread
24833 register state. If @value{GDBN} is configured for an operating system
24834 with a supported interface, the command @code{info proc} is available
24835 to report information about the process running your program, or about
24836 any process running on your system.
24838 One supported interface is a facility called @samp{/proc} that can be
24839 used to examine the image of a running process using file-system
24840 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24843 On FreeBSD and NetBSD systems, system control nodes are used to query
24844 process information.
24846 In addition, some systems may provide additional process information
24847 in core files. Note that a core file may include a subset of the
24848 information available from a live process. Process information is
24849 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24856 @itemx info proc @var{process-id}
24857 Summarize available information about a process. If a
24858 process ID is specified by @var{process-id}, display information about
24859 that process; otherwise display information about the program being
24860 debugged. The summary includes the debugged process ID, the command
24861 line used to invoke it, its current working directory, and its
24862 executable file's absolute file name.
24864 On some systems, @var{process-id} can be of the form
24865 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24866 within a process. If the optional @var{pid} part is missing, it means
24867 a thread from the process being debugged (the leading @samp{/} still
24868 needs to be present, or else @value{GDBN} will interpret the number as
24869 a process ID rather than a thread ID).
24871 @item info proc cmdline
24872 @cindex info proc cmdline
24873 Show the original command line of the process. This command is
24874 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24876 @item info proc cwd
24877 @cindex info proc cwd
24878 Show the current working directory of the process. This command is
24879 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24881 @item info proc exe
24882 @cindex info proc exe
24883 Show the name of executable of the process. This command is supported
24884 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24886 @item info proc files
24887 @cindex info proc files
24888 Show the file descriptors open by the process. For each open file
24889 descriptor, @value{GDBN} shows its number, type (file, directory,
24890 character device, socket), file pointer offset, and the name of the
24891 resource open on the descriptor. The resource name can be a file name
24892 (for files, directories, and devices) or a protocol followed by socket
24893 address (for network connections). This command is supported on
24896 This example shows the open file descriptors for a process using a
24897 tty for standard input and output as well as two network sockets:
24900 (@value{GDBP}) info proc files 22136
24904 FD Type Offset Flags Name
24905 text file - r-------- /usr/bin/ssh
24906 ctty chr - rw------- /dev/pts/20
24907 cwd dir - r-------- /usr/home/john
24908 root dir - r-------- /
24909 0 chr 0x32933a4 rw------- /dev/pts/20
24910 1 chr 0x32933a4 rw------- /dev/pts/20
24911 2 chr 0x32933a4 rw------- /dev/pts/20
24912 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24913 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24916 @item info proc mappings
24917 @cindex memory address space mappings
24918 Report the memory address space ranges accessible in a process. On
24919 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24920 on whether the process has read, write, or execute access rights to each
24921 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24922 includes the object file which is mapped to that range.
24924 @item info proc stat
24925 @itemx info proc status
24926 @cindex process detailed status information
24927 Show additional process-related information, including the user ID and
24928 group ID; virtual memory usage; the signals that are pending, blocked,
24929 and ignored; its TTY; its consumption of system and user time; its
24930 stack size; its @samp{nice} value; etc. These commands are supported
24931 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24933 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24934 information (type @kbd{man 5 proc} from your shell prompt).
24936 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24937 @code{info proc status}.
24939 @item info proc all
24940 Show all the information about the process described under all of the
24941 above @code{info proc} subcommands.
24944 @comment These sub-options of 'info proc' were not included when
24945 @comment procfs.c was re-written. Keep their descriptions around
24946 @comment against the day when someone finds the time to put them back in.
24947 @kindex info proc times
24948 @item info proc times
24949 Starting time, user CPU time, and system CPU time for your program and
24952 @kindex info proc id
24954 Report on the process IDs related to your program: its own process ID,
24955 the ID of its parent, the process group ID, and the session ID.
24958 @item set procfs-trace
24959 @kindex set procfs-trace
24960 @cindex @code{procfs} API calls
24961 This command enables and disables tracing of @code{procfs} API calls.
24963 @item show procfs-trace
24964 @kindex show procfs-trace
24965 Show the current state of @code{procfs} API call tracing.
24967 @item set procfs-file @var{file}
24968 @kindex set procfs-file
24969 Tell @value{GDBN} to write @code{procfs} API trace to the named
24970 @var{file}. @value{GDBN} appends the trace info to the previous
24971 contents of the file. The default is to display the trace on the
24974 @item show procfs-file
24975 @kindex show procfs-file
24976 Show the file to which @code{procfs} API trace is written.
24978 @item proc-trace-entry
24979 @itemx proc-trace-exit
24980 @itemx proc-untrace-entry
24981 @itemx proc-untrace-exit
24982 @kindex proc-trace-entry
24983 @kindex proc-trace-exit
24984 @kindex proc-untrace-entry
24985 @kindex proc-untrace-exit
24986 These commands enable and disable tracing of entries into and exits
24987 from the @code{syscall} interface.
24990 @kindex info pidlist
24991 @cindex process list, QNX Neutrino
24992 For QNX Neutrino only, this command displays the list of all the
24993 processes and all the threads within each process.
24996 @kindex info meminfo
24997 @cindex mapinfo list, QNX Neutrino
24998 For QNX Neutrino only, this command displays the list of all mapinfos.
25002 @subsection Features for Debugging @sc{djgpp} Programs
25003 @cindex @sc{djgpp} debugging
25004 @cindex native @sc{djgpp} debugging
25005 @cindex MS-DOS-specific commands
25008 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
25009 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
25010 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
25011 top of real-mode DOS systems and their emulations.
25013 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
25014 defines a few commands specific to the @sc{djgpp} port. This
25015 subsection describes those commands.
25020 This is a prefix of @sc{djgpp}-specific commands which print
25021 information about the target system and important OS structures.
25024 @cindex MS-DOS system info
25025 @cindex free memory information (MS-DOS)
25026 @item info dos sysinfo
25027 This command displays assorted information about the underlying
25028 platform: the CPU type and features, the OS version and flavor, the
25029 DPMI version, and the available conventional and DPMI memory.
25034 @cindex segment descriptor tables
25035 @cindex descriptor tables display
25037 @itemx info dos ldt
25038 @itemx info dos idt
25039 These 3 commands display entries from, respectively, Global, Local,
25040 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
25041 tables are data structures which store a descriptor for each segment
25042 that is currently in use. The segment's selector is an index into a
25043 descriptor table; the table entry for that index holds the
25044 descriptor's base address and limit, and its attributes and access
25047 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
25048 segment (used for both data and the stack), and a DOS segment (which
25049 allows access to DOS/BIOS data structures and absolute addresses in
25050 conventional memory). However, the DPMI host will usually define
25051 additional segments in order to support the DPMI environment.
25053 @cindex garbled pointers
25054 These commands allow to display entries from the descriptor tables.
25055 Without an argument, all entries from the specified table are
25056 displayed. An argument, which should be an integer expression, means
25057 display a single entry whose index is given by the argument. For
25058 example, here's a convenient way to display information about the
25059 debugged program's data segment:
25062 @exdent @code{(@value{GDBP}) info dos ldt $ds}
25063 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
25067 This comes in handy when you want to see whether a pointer is outside
25068 the data segment's limit (i.e.@: @dfn{garbled}).
25070 @cindex page tables display (MS-DOS)
25072 @itemx info dos pte
25073 These two commands display entries from, respectively, the Page
25074 Directory and the Page Tables. Page Directories and Page Tables are
25075 data structures which control how virtual memory addresses are mapped
25076 into physical addresses. A Page Table includes an entry for every
25077 page of memory that is mapped into the program's address space; there
25078 may be several Page Tables, each one holding up to 4096 entries. A
25079 Page Directory has up to 4096 entries, one each for every Page Table
25080 that is currently in use.
25082 Without an argument, @kbd{info dos pde} displays the entire Page
25083 Directory, and @kbd{info dos pte} displays all the entries in all of
25084 the Page Tables. An argument, an integer expression, given to the
25085 @kbd{info dos pde} command means display only that entry from the Page
25086 Directory table. An argument given to the @kbd{info dos pte} command
25087 means display entries from a single Page Table, the one pointed to by
25088 the specified entry in the Page Directory.
25090 @cindex direct memory access (DMA) on MS-DOS
25091 These commands are useful when your program uses @dfn{DMA} (Direct
25092 Memory Access), which needs physical addresses to program the DMA
25095 These commands are supported only with some DPMI servers.
25097 @cindex physical address from linear address
25098 @item info dos address-pte @var{addr}
25099 This command displays the Page Table entry for a specified linear
25100 address. The argument @var{addr} is a linear address which should
25101 already have the appropriate segment's base address added to it,
25102 because this command accepts addresses which may belong to @emph{any}
25103 segment. For example, here's how to display the Page Table entry for
25104 the page where a variable @code{i} is stored:
25107 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
25108 @exdent @code{Page Table entry for address 0x11a00d30:}
25109 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
25113 This says that @code{i} is stored at offset @code{0xd30} from the page
25114 whose physical base address is @code{0x02698000}, and shows all the
25115 attributes of that page.
25117 Note that you must cast the addresses of variables to a @code{char *},
25118 since otherwise the value of @code{__djgpp_base_address}, the base
25119 address of all variables and functions in a @sc{djgpp} program, will
25120 be added using the rules of C pointer arithmetics: if @code{i} is
25121 declared an @code{int}, @value{GDBN} will add 4 times the value of
25122 @code{__djgpp_base_address} to the address of @code{i}.
25124 Here's another example, it displays the Page Table entry for the
25128 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
25129 @exdent @code{Page Table entry for address 0x29110:}
25130 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
25134 (The @code{+ 3} offset is because the transfer buffer's address is the
25135 3rd member of the @code{_go32_info_block} structure.) The output
25136 clearly shows that this DPMI server maps the addresses in conventional
25137 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
25138 linear (@code{0x29110}) addresses are identical.
25140 This command is supported only with some DPMI servers.
25143 @cindex DOS serial data link, remote debugging
25144 In addition to native debugging, the DJGPP port supports remote
25145 debugging via a serial data link. The following commands are specific
25146 to remote serial debugging in the DJGPP port of @value{GDBN}.
25149 @kindex set com1base
25150 @kindex set com1irq
25151 @kindex set com2base
25152 @kindex set com2irq
25153 @kindex set com3base
25154 @kindex set com3irq
25155 @kindex set com4base
25156 @kindex set com4irq
25157 @item set com1base @var{addr}
25158 This command sets the base I/O port address of the @file{COM1} serial
25161 @item set com1irq @var{irq}
25162 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
25163 for the @file{COM1} serial port.
25165 There are similar commands @samp{set com2base}, @samp{set com3irq},
25166 etc.@: for setting the port address and the @code{IRQ} lines for the
25169 @kindex show com1base
25170 @kindex show com1irq
25171 @kindex show com2base
25172 @kindex show com2irq
25173 @kindex show com3base
25174 @kindex show com3irq
25175 @kindex show com4base
25176 @kindex show com4irq
25177 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
25178 display the current settings of the base address and the @code{IRQ}
25179 lines used by the COM ports.
25182 @kindex info serial
25183 @cindex DOS serial port status
25184 This command prints the status of the 4 DOS serial ports. For each
25185 port, it prints whether it's active or not, its I/O base address and
25186 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
25187 counts of various errors encountered so far.
25191 @node Cygwin Native
25192 @subsection Features for Debugging MS Windows PE Executables
25193 @cindex MS Windows debugging
25194 @cindex native Cygwin debugging
25195 @cindex Cygwin-specific commands
25197 @value{GDBN} supports native debugging of MS Windows programs, including
25198 DLLs with and without symbolic debugging information.
25200 @cindex Ctrl-BREAK, MS-Windows
25201 @cindex interrupt debuggee on MS-Windows
25202 MS-Windows programs that call @code{SetConsoleMode} to switch off the
25203 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
25204 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
25205 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
25206 sequence, which can be used to interrupt the debuggee even if it
25209 There are various additional Cygwin-specific commands, described in
25210 this section. Working with DLLs that have no debugging symbols is
25211 described in @ref{Non-debug DLL Symbols}.
25216 This is a prefix of MS Windows-specific commands which print
25217 information about the target system and important OS structures.
25219 @item info w32 selector
25220 This command displays information returned by
25221 the Win32 API @code{GetThreadSelectorEntry} function.
25222 It takes an optional argument that is evaluated to
25223 a long value to give the information about this given selector.
25224 Without argument, this command displays information
25225 about the six segment registers.
25227 @item info w32 thread-information-block
25228 This command displays thread specific information stored in the
25229 Thread Information Block (readable on the X86 CPU family using @code{$fs}
25230 selector for 32-bit programs and @code{$gs} for 64-bit programs).
25232 @kindex signal-event
25233 @item signal-event @var{id}
25234 This command signals an event with user-provided @var{id}. Used to resume
25235 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
25237 To use it, create or edit the following keys in
25238 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
25239 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
25240 (for x86_64 versions):
25244 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
25245 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
25246 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
25248 The first @code{%ld} will be replaced by the process ID of the
25249 crashing process, the second @code{%ld} will be replaced by the ID of
25250 the event that blocks the crashing process, waiting for @value{GDBN}
25254 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
25255 make the system run debugger specified by the Debugger key
25256 automatically, @code{0} will cause a dialog box with ``OK'' and
25257 ``Cancel'' buttons to appear, which allows the user to either
25258 terminate the crashing process (OK) or debug it (Cancel).
25261 @kindex set cygwin-exceptions
25262 @cindex debugging the Cygwin DLL
25263 @cindex Cygwin DLL, debugging
25264 @item set cygwin-exceptions @var{mode}
25265 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
25266 happen inside the Cygwin DLL. If @var{mode} is @code{off},
25267 @value{GDBN} will delay recognition of exceptions, and may ignore some
25268 exceptions which seem to be caused by internal Cygwin DLL
25269 ``bookkeeping''. This option is meant primarily for debugging the
25270 Cygwin DLL itself; the default value is @code{off} to avoid annoying
25271 @value{GDBN} users with false @code{SIGSEGV} signals.
25273 @kindex show cygwin-exceptions
25274 @item show cygwin-exceptions
25275 Displays whether @value{GDBN} will break on exceptions that happen
25276 inside the Cygwin DLL itself.
25278 @kindex set new-console
25279 @item set new-console @var{mode}
25280 If @var{mode} is @code{on} the debuggee will
25281 be started in a new console on next start.
25282 If @var{mode} is @code{off}, the debuggee will
25283 be started in the same console as the debugger.
25285 @kindex show new-console
25286 @item show new-console
25287 Displays whether a new console is used
25288 when the debuggee is started.
25290 @kindex set new-group
25291 @item set new-group @var{mode}
25292 This boolean value controls whether the debuggee should
25293 start a new group or stay in the same group as the debugger.
25294 This affects the way the Windows OS handles
25297 @kindex show new-group
25298 @item show new-group
25299 Displays current value of new-group boolean.
25301 @kindex set debugevents
25302 @item set debugevents
25303 This boolean value adds debug output concerning kernel events related
25304 to the debuggee seen by the debugger. This includes events that
25305 signal thread and process creation and exit, DLL loading and
25306 unloading, console interrupts, and debugging messages produced by the
25307 Windows @code{OutputDebugString} API call.
25309 @kindex set debugexec
25310 @item set debugexec
25311 This boolean value adds debug output concerning execute events
25312 (such as resume thread) seen by the debugger.
25314 @kindex set debugexceptions
25315 @item set debugexceptions
25316 This boolean value adds debug output concerning exceptions in the
25317 debuggee seen by the debugger.
25319 @kindex set debugmemory
25320 @item set debugmemory
25321 This boolean value adds debug output concerning debuggee memory reads
25322 and writes by the debugger.
25326 This boolean values specifies whether the debuggee is called
25327 via a shell or directly (default value is on).
25331 Displays if the debuggee will be started with a shell.
25336 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
25339 @node Non-debug DLL Symbols
25340 @subsubsection Support for DLLs without Debugging Symbols
25341 @cindex DLLs with no debugging symbols
25342 @cindex Minimal symbols and DLLs
25344 Very often on windows, some of the DLLs that your program relies on do
25345 not include symbolic debugging information (for example,
25346 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
25347 symbols in a DLL, it relies on the minimal amount of symbolic
25348 information contained in the DLL's export table. This section
25349 describes working with such symbols, known internally to @value{GDBN} as
25350 ``minimal symbols''.
25352 Note that before the debugged program has started execution, no DLLs
25353 will have been loaded. The easiest way around this problem is simply to
25354 start the program --- either by setting a breakpoint or letting the
25355 program run once to completion.
25357 @subsubsection DLL Name Prefixes
25359 In keeping with the naming conventions used by the Microsoft debugging
25360 tools, DLL export symbols are made available with a prefix based on the
25361 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
25362 also entered into the symbol table, so @code{CreateFileA} is often
25363 sufficient. In some cases there will be name clashes within a program
25364 (particularly if the executable itself includes full debugging symbols)
25365 necessitating the use of the fully qualified name when referring to the
25366 contents of the DLL. Use single-quotes around the name to avoid the
25367 exclamation mark (``!'') being interpreted as a language operator.
25369 Note that the internal name of the DLL may be all upper-case, even
25370 though the file name of the DLL is lower-case, or vice-versa. Since
25371 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
25372 some confusion. If in doubt, try the @code{info functions} and
25373 @code{info variables} commands or even @code{maint print msymbols}
25374 (@pxref{Symbols}). Here's an example:
25377 (@value{GDBP}) info function CreateFileA
25378 All functions matching regular expression "CreateFileA":
25380 Non-debugging symbols:
25381 0x77e885f4 CreateFileA
25382 0x77e885f4 KERNEL32!CreateFileA
25386 (@value{GDBP}) info function !
25387 All functions matching regular expression "!":
25389 Non-debugging symbols:
25390 0x6100114c cygwin1!__assert
25391 0x61004034 cygwin1!_dll_crt0@@0
25392 0x61004240 cygwin1!dll_crt0(per_process *)
25396 @subsubsection Working with Minimal Symbols
25398 Symbols extracted from a DLL's export table do not contain very much
25399 type information. All that @value{GDBN} can do is guess whether a symbol
25400 refers to a function or variable depending on the linker section that
25401 contains the symbol. Also note that the actual contents of the memory
25402 contained in a DLL are not available unless the program is running. This
25403 means that you cannot examine the contents of a variable or disassemble
25404 a function within a DLL without a running program.
25406 Variables are generally treated as pointers and dereferenced
25407 automatically. For this reason, it is often necessary to prefix a
25408 variable name with the address-of operator (``&'') and provide explicit
25409 type information in the command. Here's an example of the type of
25413 (@value{GDBP}) print 'cygwin1!__argv'
25414 'cygwin1!__argv' has unknown type; cast it to its declared type
25418 (@value{GDBP}) x 'cygwin1!__argv'
25419 'cygwin1!__argv' has unknown type; cast it to its declared type
25422 And two possible solutions:
25425 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
25426 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
25430 (@value{GDBP}) x/2x &'cygwin1!__argv'
25431 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
25432 (@value{GDBP}) x/x 0x10021608
25433 0x10021608: 0x0022fd98
25434 (@value{GDBP}) x/s 0x0022fd98
25435 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
25438 Setting a break point within a DLL is possible even before the program
25439 starts execution. However, under these circumstances, @value{GDBN} can't
25440 examine the initial instructions of the function in order to skip the
25441 function's frame set-up code. You can work around this by using ``*&''
25442 to set the breakpoint at a raw memory address:
25445 (@value{GDBP}) break *&'python22!PyOS_Readline'
25446 Breakpoint 1 at 0x1e04eff0
25449 The author of these extensions is not entirely convinced that setting a
25450 break point within a shared DLL like @file{kernel32.dll} is completely
25454 @subsection Commands Specific to @sc{gnu} Hurd Systems
25455 @cindex @sc{gnu} Hurd debugging
25457 This subsection describes @value{GDBN} commands specific to the
25458 @sc{gnu} Hurd native debugging.
25463 @kindex set signals@r{, Hurd command}
25464 @kindex set sigs@r{, Hurd command}
25465 This command toggles the state of inferior signal interception by
25466 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
25467 affected by this command. @code{sigs} is a shorthand alias for
25472 @kindex show signals@r{, Hurd command}
25473 @kindex show sigs@r{, Hurd command}
25474 Show the current state of intercepting inferior's signals.
25476 @item set signal-thread
25477 @itemx set sigthread
25478 @kindex set signal-thread
25479 @kindex set sigthread
25480 This command tells @value{GDBN} which thread is the @code{libc} signal
25481 thread. That thread is run when a signal is delivered to a running
25482 process. @code{set sigthread} is the shorthand alias of @code{set
25485 @item show signal-thread
25486 @itemx show sigthread
25487 @kindex show signal-thread
25488 @kindex show sigthread
25489 These two commands show which thread will run when the inferior is
25490 delivered a signal.
25493 @kindex set stopped@r{, Hurd command}
25494 This commands tells @value{GDBN} that the inferior process is stopped,
25495 as with the @code{SIGSTOP} signal. The stopped process can be
25496 continued by delivering a signal to it.
25499 @kindex show stopped@r{, Hurd command}
25500 This command shows whether @value{GDBN} thinks the debuggee is
25503 @item set exceptions
25504 @kindex set exceptions@r{, Hurd command}
25505 Use this command to turn off trapping of exceptions in the inferior.
25506 When exception trapping is off, neither breakpoints nor
25507 single-stepping will work. To restore the default, set exception
25510 @item show exceptions
25511 @kindex show exceptions@r{, Hurd command}
25512 Show the current state of trapping exceptions in the inferior.
25514 @item set task pause
25515 @kindex set task@r{, Hurd commands}
25516 @cindex task attributes (@sc{gnu} Hurd)
25517 @cindex pause current task (@sc{gnu} Hurd)
25518 This command toggles task suspension when @value{GDBN} has control.
25519 Setting it to on takes effect immediately, and the task is suspended
25520 whenever @value{GDBN} gets control. Setting it to off will take
25521 effect the next time the inferior is continued. If this option is set
25522 to off, you can use @code{set thread default pause on} or @code{set
25523 thread pause on} (see below) to pause individual threads.
25525 @item show task pause
25526 @kindex show task@r{, Hurd commands}
25527 Show the current state of task suspension.
25529 @item set task detach-suspend-count
25530 @cindex task suspend count
25531 @cindex detach from task, @sc{gnu} Hurd
25532 This command sets the suspend count the task will be left with when
25533 @value{GDBN} detaches from it.
25535 @item show task detach-suspend-count
25536 Show the suspend count the task will be left with when detaching.
25538 @item set task exception-port
25539 @itemx set task excp
25540 @cindex task exception port, @sc{gnu} Hurd
25541 This command sets the task exception port to which @value{GDBN} will
25542 forward exceptions. The argument should be the value of the @dfn{send
25543 rights} of the task. @code{set task excp} is a shorthand alias.
25545 @item set noninvasive
25546 @cindex noninvasive task options
25547 This command switches @value{GDBN} to a mode that is the least
25548 invasive as far as interfering with the inferior is concerned. This
25549 is the same as using @code{set task pause}, @code{set exceptions}, and
25550 @code{set signals} to values opposite to the defaults.
25552 @item info send-rights
25553 @itemx info receive-rights
25554 @itemx info port-rights
25555 @itemx info port-sets
25556 @itemx info dead-names
25559 @cindex send rights, @sc{gnu} Hurd
25560 @cindex receive rights, @sc{gnu} Hurd
25561 @cindex port rights, @sc{gnu} Hurd
25562 @cindex port sets, @sc{gnu} Hurd
25563 @cindex dead names, @sc{gnu} Hurd
25564 These commands display information about, respectively, send rights,
25565 receive rights, port rights, port sets, and dead names of a task.
25566 There are also shorthand aliases: @code{info ports} for @code{info
25567 port-rights} and @code{info psets} for @code{info port-sets}.
25569 @item set thread pause
25570 @kindex set thread@r{, Hurd command}
25571 @cindex thread properties, @sc{gnu} Hurd
25572 @cindex pause current thread (@sc{gnu} Hurd)
25573 This command toggles current thread suspension when @value{GDBN} has
25574 control. Setting it to on takes effect immediately, and the current
25575 thread is suspended whenever @value{GDBN} gets control. Setting it to
25576 off will take effect the next time the inferior is continued.
25577 Normally, this command has no effect, since when @value{GDBN} has
25578 control, the whole task is suspended. However, if you used @code{set
25579 task pause off} (see above), this command comes in handy to suspend
25580 only the current thread.
25582 @item show thread pause
25583 @kindex show thread@r{, Hurd command}
25584 This command shows the state of current thread suspension.
25586 @item set thread run
25587 This command sets whether the current thread is allowed to run.
25589 @item show thread run
25590 Show whether the current thread is allowed to run.
25592 @item set thread detach-suspend-count
25593 @cindex thread suspend count, @sc{gnu} Hurd
25594 @cindex detach from thread, @sc{gnu} Hurd
25595 This command sets the suspend count @value{GDBN} will leave on a
25596 thread when detaching. This number is relative to the suspend count
25597 found by @value{GDBN} when it notices the thread; use @code{set thread
25598 takeover-suspend-count} to force it to an absolute value.
25600 @item show thread detach-suspend-count
25601 Show the suspend count @value{GDBN} will leave on the thread when
25604 @item set thread exception-port
25605 @itemx set thread excp
25606 Set the thread exception port to which to forward exceptions. This
25607 overrides the port set by @code{set task exception-port} (see above).
25608 @code{set thread excp} is the shorthand alias.
25610 @item set thread takeover-suspend-count
25611 Normally, @value{GDBN}'s thread suspend counts are relative to the
25612 value @value{GDBN} finds when it notices each thread. This command
25613 changes the suspend counts to be absolute instead.
25615 @item set thread default
25616 @itemx show thread default
25617 @cindex thread default settings, @sc{gnu} Hurd
25618 Each of the above @code{set thread} commands has a @code{set thread
25619 default} counterpart (e.g., @code{set thread default pause}, @code{set
25620 thread default exception-port}, etc.). The @code{thread default}
25621 variety of commands sets the default thread properties for all
25622 threads; you can then change the properties of individual threads with
25623 the non-default commands.
25630 @value{GDBN} provides the following commands specific to the Darwin target:
25633 @item set debug darwin @var{num}
25634 @kindex set debug darwin
25635 When set to a non zero value, enables debugging messages specific to
25636 the Darwin support. Higher values produce more verbose output.
25638 @item show debug darwin
25639 @kindex show debug darwin
25640 Show the current state of Darwin messages.
25642 @item set debug mach-o @var{num}
25643 @kindex set debug mach-o
25644 When set to a non zero value, enables debugging messages while
25645 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25646 file format used on Darwin for object and executable files.) Higher
25647 values produce more verbose output. This is a command to diagnose
25648 problems internal to @value{GDBN} and should not be needed in normal
25651 @item show debug mach-o
25652 @kindex show debug mach-o
25653 Show the current state of Mach-O file messages.
25655 @item set mach-exceptions on
25656 @itemx set mach-exceptions off
25657 @kindex set mach-exceptions
25658 On Darwin, faults are first reported as a Mach exception and are then
25659 mapped to a Posix signal. Use this command to turn on trapping of
25660 Mach exceptions in the inferior. This might be sometimes useful to
25661 better understand the cause of a fault. The default is off.
25663 @item show mach-exceptions
25664 @kindex show mach-exceptions
25665 Show the current state of exceptions trapping.
25669 @subsection FreeBSD
25672 When the ABI of a system call is changed in the FreeBSD kernel, this
25673 is implemented by leaving a compatibility system call using the old
25674 ABI at the existing number and allocating a new system call number for
25675 the version using the new ABI. As a convenience, when a system call
25676 is caught by name (@pxref{catch syscall}), compatibility system calls
25679 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25680 system call and catching the @code{kevent} system call by name catches
25684 (@value{GDBP}) catch syscall kevent
25685 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25691 @section Embedded Operating Systems
25693 This section describes configurations involving the debugging of
25694 embedded operating systems that are available for several different
25697 @value{GDBN} includes the ability to debug programs running on
25698 various real-time operating systems.
25700 @node Embedded Processors
25701 @section Embedded Processors
25703 This section goes into details specific to particular embedded
25706 @cindex send command to simulator
25707 Whenever a specific embedded processor has a simulator, @value{GDBN}
25708 allows to send an arbitrary command to the simulator.
25711 @item sim @var{command}
25712 @kindex sim@r{, a command}
25713 Send an arbitrary @var{command} string to the simulator. Consult the
25714 documentation for the specific simulator in use for information about
25715 acceptable commands.
25720 * ARC:: Synopsys ARC
25723 * M68K:: Motorola M68K
25724 * MicroBlaze:: Xilinx MicroBlaze
25725 * MIPS Embedded:: MIPS Embedded
25726 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25727 * PowerPC Embedded:: PowerPC Embedded
25730 * Super-H:: Renesas Super-H
25734 @subsection Synopsys ARC
25735 @cindex Synopsys ARC
25736 @cindex ARC specific commands
25742 @value{GDBN} provides the following ARC-specific commands:
25745 @item set debug arc
25746 @kindex set debug arc
25747 Control the level of ARC specific debug messages. Use 0 for no messages (the
25748 default), 1 for debug messages, and 2 for even more debug messages.
25750 @item show debug arc
25751 @kindex show debug arc
25752 Show the level of ARC specific debugging in operation.
25754 @item maint print arc arc-instruction @var{address}
25755 @kindex maint print arc arc-instruction
25756 Print internal disassembler information about instruction at a given address.
25763 @value{GDBN} provides the following ARM-specific commands:
25766 @item set arm disassembler
25768 This commands selects from a list of disassembly styles. The
25769 @code{"std"} style is the standard style.
25771 @item show arm disassembler
25773 Show the current disassembly style.
25775 @item set arm apcs32
25776 @cindex ARM 32-bit mode
25777 This command toggles ARM operation mode between 32-bit and 26-bit.
25779 @item show arm apcs32
25780 Display the current usage of the ARM 32-bit mode.
25782 @item set arm fpu @var{fputype}
25783 This command sets the ARM floating-point unit (FPU) type. The
25784 argument @var{fputype} can be one of these:
25788 Determine the FPU type by querying the OS ABI.
25790 Software FPU, with mixed-endian doubles on little-endian ARM
25793 GCC-compiled FPA co-processor.
25795 Software FPU with pure-endian doubles.
25801 Show the current type of the FPU.
25804 This command forces @value{GDBN} to use the specified ABI.
25807 Show the currently used ABI.
25809 @item set arm fallback-mode (arm|thumb|auto)
25810 @value{GDBN} uses the symbol table, when available, to determine
25811 whether instructions are ARM or Thumb. This command controls
25812 @value{GDBN}'s default behavior when the symbol table is not
25813 available. The default is @samp{auto}, which causes @value{GDBN} to
25814 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25817 @item show arm fallback-mode
25818 Show the current fallback instruction mode.
25820 @item set arm force-mode (arm|thumb|auto)
25821 This command overrides use of the symbol table to determine whether
25822 instructions are ARM or Thumb. The default is @samp{auto}, which
25823 causes @value{GDBN} to use the symbol table and then the setting
25824 of @samp{set arm fallback-mode}.
25826 @item show arm force-mode
25827 Show the current forced instruction mode.
25829 @item set arm unwind-secure-frames
25830 This command enables unwinding from Non-secure to Secure mode on
25831 Cortex-M with Security extension.
25832 This can trigger security exceptions when unwinding the exception
25834 It is enabled by default.
25836 @item show arm unwind-secure-frames
25837 Show whether unwinding from Non-secure to Secure mode is enabled.
25839 @item set debug arm
25840 Toggle whether to display ARM-specific debugging messages from the ARM
25841 target support subsystem.
25843 @item show debug arm
25844 Show whether ARM-specific debugging messages are enabled.
25848 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25849 The @value{GDBN} ARM simulator accepts the following optional arguments.
25852 @item --swi-support=@var{type}
25853 Tell the simulator which SWI interfaces to support. The argument
25854 @var{type} may be a comma separated list of the following values.
25855 The default value is @code{all}.
25871 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25872 The @value{GDBN} BPF simulator accepts the following optional arguments.
25875 @item --skb-data-offset=@var{offset}
25876 Tell the simulator the offset, measured in bytes, of the
25877 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25878 This offset is used by some BPF specific-purpose load/store
25879 instructions. Defaults to 0.
25886 The Motorola m68k configuration includes ColdFire support.
25889 @subsection MicroBlaze
25890 @cindex Xilinx MicroBlaze
25891 @cindex XMD, Xilinx Microprocessor Debugger
25893 The MicroBlaze is a soft-core processor supported on various Xilinx
25894 FPGAs, such as Spartan or Virtex series. Boards with these processors
25895 usually have JTAG ports which connect to a host system running the Xilinx
25896 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25897 This host system is used to download the configuration bitstream to
25898 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25899 communicates with the target board using the JTAG interface and
25900 presents a @code{gdbserver} interface to the board. By default
25901 @code{xmd} uses port @code{1234}. (While it is possible to change
25902 this default port, it requires the use of undocumented @code{xmd}
25903 commands. Contact Xilinx support if you need to do this.)
25905 Use these GDB commands to connect to the MicroBlaze target processor.
25908 @item target remote :1234
25909 Use this command to connect to the target if you are running @value{GDBN}
25910 on the same system as @code{xmd}.
25912 @item target remote @var{xmd-host}:1234
25913 Use this command to connect to the target if it is connected to @code{xmd}
25914 running on a different system named @var{xmd-host}.
25917 Use this command to download a program to the MicroBlaze target.
25919 @item set debug microblaze @var{n}
25920 Enable MicroBlaze-specific debugging messages if non-zero.
25922 @item show debug microblaze @var{n}
25923 Show MicroBlaze-specific debugging level.
25926 @node MIPS Embedded
25927 @subsection @acronym{MIPS} Embedded
25930 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25933 @item set mipsfpu double
25934 @itemx set mipsfpu single
25935 @itemx set mipsfpu none
25936 @itemx set mipsfpu auto
25937 @itemx show mipsfpu
25938 @kindex set mipsfpu
25939 @kindex show mipsfpu
25940 @cindex @acronym{MIPS} remote floating point
25941 @cindex floating point, @acronym{MIPS} remote
25942 If your target board does not support the @acronym{MIPS} floating point
25943 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25944 need this, you may wish to put the command in your @value{GDBN} init
25945 file). This tells @value{GDBN} how to find the return value of
25946 functions which return floating point values. It also allows
25947 @value{GDBN} to avoid saving the floating point registers when calling
25948 functions on the board. If you are using a floating point coprocessor
25949 with only single precision floating point support, as on the @sc{r4650}
25950 processor, use the command @samp{set mipsfpu single}. The default
25951 double precision floating point coprocessor may be selected using
25952 @samp{set mipsfpu double}.
25954 In previous versions the only choices were double precision or no
25955 floating point, so @samp{set mipsfpu on} will select double precision
25956 and @samp{set mipsfpu off} will select no floating point.
25958 As usual, you can inquire about the @code{mipsfpu} variable with
25959 @samp{show mipsfpu}.
25962 @node OpenRISC 1000
25963 @subsection OpenRISC 1000
25964 @cindex OpenRISC 1000
25967 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25968 mainly provided as a soft-core which can run on Xilinx, Altera and other
25971 @value{GDBN} for OpenRISC supports the below commands when connecting to
25979 Runs the builtin CPU simulator which can run very basic
25980 programs but does not support most hardware functions like MMU.
25981 For more complex use cases the user is advised to run an external
25982 target, and connect using @samp{target remote}.
25984 Example: @code{target sim}
25986 @item set debug or1k
25987 Toggle whether to display OpenRISC-specific debugging messages from the
25988 OpenRISC target support subsystem.
25990 @item show debug or1k
25991 Show whether OpenRISC-specific debugging messages are enabled.
25994 @node PowerPC Embedded
25995 @subsection PowerPC Embedded
25997 @cindex DVC register
25998 @value{GDBN} supports using the DVC (Data Value Compare) register to
25999 implement in hardware simple hardware watchpoint conditions of the form:
26002 (@value{GDBP}) watch @var{address|variable} \
26003 if @var{address|variable} == @var{constant expression}
26006 The DVC register will be automatically used when @value{GDBN} detects
26007 such pattern in a condition expression, and the created watchpoint uses one
26008 debug register (either the @code{exact-watchpoints} option is on and the
26009 variable is scalar, or the variable has a length of one byte). This feature
26010 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
26013 When running on PowerPC embedded processors, @value{GDBN} automatically uses
26014 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
26015 in which case watchpoints using only one debug register are created when
26016 watching variables of scalar types.
26018 You can create an artificial array to watch an arbitrary memory
26019 region using one of the following commands (@pxref{Expressions}):
26022 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
26023 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
26026 PowerPC embedded processors support masked watchpoints. See the discussion
26027 about the @code{mask} argument in @ref{Set Watchpoints}.
26029 @cindex ranged breakpoint
26030 PowerPC embedded processors support hardware accelerated
26031 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
26032 the inferior whenever it executes an instruction at any address within
26033 the range it was set at. To set a ranged breakpoint in @value{GDBN},
26034 use the @code{break-range} command.
26036 @value{GDBN} provides the following PowerPC-specific commands:
26039 @kindex break-range
26040 @item break-range @var{start-locspec}, @var{end-locspec}
26041 Set a breakpoint for an address range given by @var{start-locspec} and
26042 @var{end-locspec}, which are location specs. @xref{Location
26043 Specifications}, for a list of all the possible forms of location
26044 specs. @value{GDBN} resolves both @var{start-locspec} and
26045 @var{end-locspec}, and uses the addresses of the resolved code
26046 locations as start and end addresses of the range to break at. The
26047 breakpoint will stop execution of the inferior whenever it executes an
26048 instruction at any address between the start and end addresses,
26049 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
26050 to multiple code locations in the program, then the command aborts
26051 with an error without creating a breakpoint.
26053 @kindex set powerpc
26054 @item set powerpc soft-float
26055 @itemx show powerpc soft-float
26056 Force @value{GDBN} to use (or not use) a software floating point calling
26057 convention. By default, @value{GDBN} selects the calling convention based
26058 on the selected architecture and the provided executable file.
26060 @item set powerpc vector-abi
26061 @itemx show powerpc vector-abi
26062 Force @value{GDBN} to use the specified calling convention for vector
26063 arguments and return values. The valid options are @samp{auto};
26064 @samp{generic}, to avoid vector registers even if they are present;
26065 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
26066 registers. By default, @value{GDBN} selects the calling convention
26067 based on the selected architecture and the provided executable file.
26069 @item set powerpc exact-watchpoints
26070 @itemx show powerpc exact-watchpoints
26071 Allow @value{GDBN} to use only one debug register when watching a variable
26072 of scalar type, thus assuming that the variable is accessed through the
26073 address of its first byte.
26078 @subsection Atmel AVR
26081 When configured for debugging the Atmel AVR, @value{GDBN} supports the
26082 following AVR-specific commands:
26085 @item info io_registers
26086 @kindex info io_registers@r{, AVR}
26087 @cindex I/O registers (Atmel AVR)
26088 This command displays information about the AVR I/O registers. For
26089 each register, @value{GDBN} prints its number and value.
26096 When configured for debugging CRIS, @value{GDBN} provides the
26097 following CRIS-specific commands:
26100 @item set cris-version @var{ver}
26101 @cindex CRIS version
26102 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
26103 The CRIS version affects register names and sizes. This command is useful in
26104 case autodetection of the CRIS version fails.
26106 @item show cris-version
26107 Show the current CRIS version.
26109 @item set cris-dwarf2-cfi
26110 @cindex DWARF-2 CFI and CRIS
26111 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
26112 Change to @samp{off} when using @code{gcc-cris} whose version is below
26115 @item show cris-dwarf2-cfi
26116 Show the current state of using DWARF-2 CFI.
26118 @item set cris-mode @var{mode}
26120 Set the current CRIS mode to @var{mode}. It should only be changed when
26121 debugging in guru mode, in which case it should be set to
26122 @samp{guru} (the default is @samp{normal}).
26124 @item show cris-mode
26125 Show the current CRIS mode.
26129 @subsection Renesas Super-H
26132 For the Renesas Super-H processor, @value{GDBN} provides these
26136 @item set sh calling-convention @var{convention}
26137 @kindex set sh calling-convention
26138 Set the calling-convention used when calling functions from @value{GDBN}.
26139 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
26140 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
26141 convention. If the DWARF-2 information of the called function specifies
26142 that the function follows the Renesas calling convention, the function
26143 is called using the Renesas calling convention. If the calling convention
26144 is set to @samp{renesas}, the Renesas calling convention is always used,
26145 regardless of the DWARF-2 information. This can be used to override the
26146 default of @samp{gcc} if debug information is missing, or the compiler
26147 does not emit the DWARF-2 calling convention entry for a function.
26149 @item show sh calling-convention
26150 @kindex show sh calling-convention
26151 Show the current calling convention setting.
26156 @node Architectures
26157 @section Architectures
26159 This section describes characteristics of architectures that affect
26160 all uses of @value{GDBN} with the architecture, both native and cross.
26167 * HPPA:: HP PA architecture
26172 * AMD GPU:: @acronym{AMD GPU} architectures
26176 @subsection AArch64
26177 @cindex AArch64 support
26179 When @value{GDBN} is debugging the AArch64 architecture, it provides the
26180 following special commands:
26183 @item set debug aarch64
26184 @kindex set debug aarch64
26185 This command determines whether AArch64 architecture-specific debugging
26186 messages are to be displayed.
26188 @item show debug aarch64
26189 Show whether AArch64 debugging messages are displayed.
26193 @subsubsection AArch64 SVE.
26194 @cindex AArch64 SVE.
26196 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
26197 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
26198 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
26199 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
26200 @code{$vg} will be provided. This is the vector granule for the current thread
26201 and represents the number of 64-bit chunks in an SVE @code{z} register.
26203 If the vector length changes, then the @code{$vg} register will be updated,
26204 but the lengths of the @code{z} and @code{p} registers will not change. This
26205 is a known limitation of @value{GDBN} and does not affect the execution of the
26208 For SVE, the following definitions are used throughout @value{GDBN}'s source
26209 code and in this document:
26214 @var{vl}: The vector length, in bytes. It defines the size of each @code{Z}
26220 @var{vq}: The number of 128 bit units in @var{vl}. This is mostly used
26221 internally by @value{GDBN} and the Linux Kernel.
26226 @var{vg}: The number of 64 bit units in @var{vl}. This is mostly used
26227 internally by @value{GDBN} and the Linux Kernel.
26233 @subsubsection AArch64 SME.
26234 @anchor{AArch64 SME}
26236 @cindex AArch64 SME
26237 @cindex Scalable Matrix Extension
26239 The Scalable Matrix Extension (@url{https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/scalable-matrix-extension-armv9-a-architecture, @acronym{SME}})
26240 is an AArch64 architecture extension that expands on the concept of the
26241 Scalable Vector Extension (@url{https://developer.arm.com/documentation/101726/4-0/Learn-about-the-Scalable-Vector-Extension--SVE-/What-is-the-Scalable-Vector-Extension-, @acronym{SVE}})
26242 by providing a 2-dimensional register @code{ZA}, which is a square
26243 matrix of variable size, just like SVE provides a group of vector registers of
26246 Similarly to SVE, where the size of each @code{Z} register is directly related
26247 to the vector length (@var{vl} for short), the @acronym{SME} @code{ZA} matrix
26248 register's size is directly related to the streaming vector length
26249 (@var{svl} for short). @xref{vl}. @xref{svl}.
26251 The @code{ZA} register state can be either active or inactive, if it is not in
26254 @acronym{SME} also introduces a new execution mode called streaming
26255 @acronym{SVE} mode (streaming mode for short). When streaming mode is
26256 enabled, the program supports execution of @acronym{SVE2} instructions and the
26257 @acronym{SVE} registers will have vector length @var{svl}. When streaming
26258 mode is disabled, the SVE registers have vector length @var{vl}.
26260 For more information about @acronym{SME} and @acronym{SVE}, please refer to
26261 official @url{https://developer.arm.com/documentation/ddi0487/latest,
26262 architecture documentation}.
26264 The following definitions are used throughout @value{GDBN}'s source code and
26270 @var{svl}: The streaming vector length, in bytes. It defines the size of each
26271 dimension of the 2-dimensional square @code{ZA} matrix. The total size of
26272 @code{ZA} is therefore @var{svl} by @var{svl}.
26274 When streaming mode is enabled, it defines the size of the @acronym{SVE}
26280 @var{svq}: The number of 128 bit units in @var{svl}, also known as streaming
26281 vector granule. This is mostly used internally by @value{GDBN} and the Linux
26287 @var{svg}: The number of 64 bit units in @var{svl}. This is mostly used
26288 internally by @value{GDBN} and the Linux Kernel.
26294 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Matrix
26295 Extension (@acronym{SME}) is present, then @value{GDBN} will make the @code{ZA}
26296 register available. @value{GDBN} will also make the @code{SVG} register and
26297 @code{SVCR} pseudo-register available.
26299 The @code{ZA} register is a 2-dimensional square @var{svl} by @var{svl}
26300 matrix of bytes. To simplify the representation and access to the @code{ZA}
26301 register in @value{GDBN}, it is defined as a vector of
26302 @var{svl}x@var{svl} bytes.
26304 If the user wants to index the @code{ZA} register as a matrix, it is possible
26305 to reference @code{ZA} as @code{ZA[@var{i}][@var{j}]}, where @var{i} is the
26306 row number and @var{j} is the column number.
26308 The @code{SVG} register always contains the streaming vector granule
26309 (@var{svg}) for the current thread. From the value of register @code{SVG} we
26310 can easily derive the @var{svl} value.
26312 @anchor{aarch64 sme svcr}
26313 The @code{SVCR} pseudo-register (streaming vector control register) is a status
26314 register that holds two state bits: @sc{sm} in bit 0 and @sc{za} in bit 1.
26316 If the @sc{sm} bit is 1, it means the current thread is in streaming
26317 mode, and the @acronym{SVE} registers will use @var{svl} for their sizes. If
26318 the @sc{sm} bit is 0, the current thread is not in streaming mode, and the
26319 @acronym{SVE} registers will use @var{vl} for their sizes. @xref{vl}.
26321 If the @sc{za} bit is 1, it means the @code{ZA} register is being used and
26322 has meaningful contents. If the @sc{za} bit is 0, the @code{ZA} register is
26323 unavailable and its contents are undefined.
26325 For convenience and simplicity, if the @sc{za} bit is 0, the @code{ZA}
26326 register and all of its pseudo-registers will read as zero.
26328 If @var{svl} changes during the execution of a program, then the @code{ZA}
26329 register size and the bits in the @code{SVCR} pseudo-register will be updated
26332 It is possible for users to change @var{svl} during the execution of a
26333 program by modifying the @code{SVG} register value.
26335 Whenever the @code{SVG} register is modified with a new value, the
26336 following will be observed:
26340 @item The @sc{za} and @sc{sm} bits will be cleared in the @code{SVCR}
26343 @item The @code{ZA} register will have a new size and its state will be
26344 cleared, forcing its contents and the contents of all of its pseudo-registers
26347 @item If the @sc{sm} bit was 1, the @acronym{SVE} registers will be reset to
26348 having their sizes based on @var{vl} as opposed to @var{svl}. If the
26349 @sc{sm} bit was 0 prior to modifying the @code{SVG} register, there will be no
26350 observable effect on the @acronym{SVE} registers.
26354 The possible values for the @code{SVG} register are 2, 4, 8, 16, 32. These
26355 numbers correspond to streaming vector length (@var{svl}) values of 16
26356 bytes, 32 bytes, 64 bytes, 128 bytes and 256 bytes respectively.
26358 The minimum size of the @code{ZA} register is 16 x 16 (256) bytes, and the
26359 maximum size is 256 x 256 (65536) bytes. In streaming mode, with bit @sc{sm}
26360 set, the size of the @code{ZA} register is the size of all the SVE @code{Z}
26361 registers combined.
26363 The @code{ZA} register can also be accessed using tiles and tile slices.
26365 Tile pseudo-registers are square, 2-dimensional sub-arrays of elements within
26366 the @code{ZA} register.
26368 The tile pseudo-registers have the following naming pattern:
26369 @code{ZA<@var{tile number}><@var{qualifier}>}.
26371 There is a total of 31 @code{ZA} tile pseudo-registers. They are
26372 @code{ZA0B}, @code{ZA0H} through @code{ZA1H}, @code{ZA0S} through @code{ZA3S},
26373 @code{ZA0D} through @code{ZA7D} and @code{ZA0Q} through @code{ZA15Q}.
26375 Tile slice pseudo-registers are vectors of horizontally or vertically
26376 contiguous elements within the @code{ZA} register.
26378 The tile slice pseudo-registers have the following naming pattern:
26379 @code{ZA<@var{tile number}><@var{direction}><@var{qualifier}>
26380 <@var{slice number}>}.
26382 There are up to 16 tiles (0 ~ 15), the direction can be either @code{v}
26383 (vertical) or @code{h} (horizontal), the qualifiers can be @code{b} (byte),
26384 @code{h} (halfword), @code{s} (word), @code{d} (doubleword) and @code{q}
26385 (quadword) and there are up to 256 slices (0 ~ 255) depending on the value
26386 of @var{svl}. The number of slices is the same as the value of @var{svl}.
26388 The number of available tile slice pseudo-registers can be large. For a
26389 minimum @var{svl} of 16 bytes, there are 5 (number of qualifiers) x
26390 2 (number of directions) x 16 (@var{svl}) pseudo-registers. For the
26391 maximum @var{svl} of 256 bytes, there are 5 x 2 x 256 pseudo-registers.
26393 When listing all the available registers, users will see the
26394 currently-available @code{ZA} pseudo-registers. Pseudo-registers that don't
26395 exist for a given @var{svl} value will not be displayed.
26397 For more information on @acronym{SME} and its terminology, please refer to the
26398 @url{https://developer.arm.com/documentation/ddi0616/aa/,
26399 Arm Architecture Reference Manual Supplement}, The Scalable Matrix Extension
26400 (@acronym{SME}), for Armv9-A.
26402 Some features are still under development and rely on
26403 @url{https://github.com/ARM-software/acle/releases/latest, ACLE} and
26404 @url{https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst, ABI}
26405 definitions, so there are known limitations to the current @acronym{SME}
26406 support in @value{GDBN}.
26408 One such example is calling functions in the program being debugged by
26409 @value{GDBN}. Such calls are not @acronym{SME}-aware and thus don't take into
26410 account the @code{SVCR} pseudo-register bits nor the @code{ZA} register
26411 contents. @xref{Calling}.
26413 The @url{https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#the-za-lazy-saving-scheme,
26414 lazy saving scheme} involving the @code{TPIDR2} register is not yet supported
26415 by @value{GDBN}, though the @code{TPIDR2} register is known and supported
26418 Lastly, an important limitation for @command{gdbserver} is its inability to
26419 communicate @var{svl} changes to @value{GDBN}. This means @command{gdbserver},
26420 even though it is capable of adjusting its internal caches to reflect a change
26421 in the value of @var{svl} mid-execution, will operate with a potentially
26422 different @var{svl} value compared to @value{GDBN}. This can lead to
26423 @value{GDBN} showing incorrect values for the @code{ZA} register and
26424 incorrect values for SVE registers (when in streaming mode).
26426 This is the same limitation we have for the @acronym{SVE} registers, and there
26427 are plans to address this limitation going forward.
26429 @subsubsection AArch64 SME2.
26430 @anchor{AArch64 SME2}
26432 @cindex AArch64 SME2
26433 @cindex Scalable Matrix Extension 2
26435 The Scalable Matrix Extension 2 is an AArch64 architecture extension that
26436 further expands the @acronym{SME} extension with the following:
26440 @item The ability to address the @code{ZA} array through groups of
26441 one-dimensional @code{ZA} array vectors, as opposed to @code{ZA} tiles
26444 @item Instructions to operate on groups of @acronym{SVE} @code{Z} registers and
26445 @code{ZA} array vectors.
26447 @item A new 512 bit @code{ZT0} lookup table register, for data decompression.
26451 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Matrix
26452 Extension 2 (@acronym{SME2}) is present, then @value{GDBN} will make the
26453 @code{ZT0} register available.
26455 The @code{ZT0} register is only considered active when the @code{ZA} register
26456 state is active, therefore when the @sc{za} bit of the @code{SVCR} is 1.
26458 When the @sc{za} bit of @code{SVCR} is 0, that means the @code{ZA} register
26459 state is not active, which means the @code{ZT0} register state is also not
26462 When @code{ZT0} is not active, it is comprised of zeroes, just like @code{ZA}.
26464 Similarly to the @code{ZA} register, if the @code{ZT0} state is not active and
26465 the user attempts to modify its value such that any of its bytes is non-zero,
26466 then @value{GDBN} will initialize the @code{ZA} register state as well, which
26467 means the @code{SVCR} @sc{za} bit gets set to 1.
26469 For more information about @acronym{SME2}, please refer to the
26470 official @url{https://developer.arm.com/documentation/ddi0487/latest,
26471 architecture documentation}.
26473 @subsubsection AArch64 Pointer Authentication.
26474 @cindex AArch64 Pointer Authentication.
26475 @anchor{AArch64 PAC}
26477 When @value{GDBN} is debugging the AArch64 architecture, and the program is
26478 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
26479 register @code{$lr} is pointing to an PAC function its value will be masked.
26480 When GDB prints a backtrace, any addresses that required unmasking will be
26481 postfixed with the marker [PAC]. When using the MI, this is printed as part
26482 of the @code{addr_flags} field.
26484 @subsubsection AArch64 Memory Tagging Extension.
26485 @cindex AArch64 Memory Tagging Extension.
26487 When @value{GDBN} is debugging the AArch64 architecture, the program is
26488 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
26489 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
26490 available for inspection and editing of logical and allocation tags.
26491 @xref{Memory Tagging}.
26493 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
26494 signals are generated as a result of memory tag failures.
26496 If the tag violation is synchronous, the following will be shown:
26499 Program received signal SIGSEGV, Segmentation fault
26500 Memory tag violation while accessing address 0x0500fffff7ff8000
26505 If the tag violation is asynchronous, the fault address is not available.
26506 In this case @value{GDBN} will show the following:
26509 Program received signal SIGSEGV, Segmentation fault
26510 Memory tag violation
26511 Fault address unavailable.
26514 A special register, @code{tag_ctl}, is made available through the
26515 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
26516 options that can be controlled at runtime and emulates the @code{prctl}
26517 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
26518 documentation in the Linux kernel.
26520 @value{GDBN} supports dumping memory tag data to core files through the
26521 @command{gcore} command and reading memory tag data from core files generated
26522 by the @command{gcore} command or the Linux kernel.
26524 When a process uses memory-mapped pages protected by memory tags (for
26525 example, AArch64 MTE), this additional information will be recorded in
26526 the core file in the event of a crash or if @value{GDBN} generates a core file
26527 from the current process state.
26529 The memory tag data will be used so developers can display the memory
26530 tags from a particular memory region (using the @samp{m} modifier to the
26531 @command{x} command, using the @command{print} command or using the various
26532 @command{memory-tag} subcommands.
26534 In the case of a crash, @value{GDBN} will attempt to retrieve the memory tag
26535 information automatically from the core file, and will show one of the above
26536 messages depending on whether the synchronous or asynchronous mode is selected.
26537 @xref{Memory Tagging}. @xref{Memory}.
26543 @item set struct-convention @var{mode}
26544 @kindex set struct-convention
26545 @cindex struct return convention
26546 @cindex struct/union returned in registers
26547 Set the convention used by the inferior to return @code{struct}s and
26548 @code{union}s from functions to @var{mode}. Possible values of
26549 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
26550 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
26551 are returned on the stack, while @code{"reg"} means that a
26552 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
26553 be returned in a register.
26555 @item show struct-convention
26556 @kindex show struct-convention
26557 Show the current setting of the convention to return @code{struct}s
26562 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
26563 @cindex Intel Memory Protection Extensions (MPX).
26565 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
26566 @footnote{The register named with capital letters represent the architecture
26567 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
26568 which are the lower bound and upper bound. Bounds are effective addresses or
26569 memory locations. The upper bounds are architecturally represented in 1's
26570 complement form. A bound having lower bound = 0, and upper bound = 0
26571 (1's complement of all bits set) will allow access to the entire address space.
26573 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
26574 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
26575 display the upper bound performing the complement of one operation on the
26576 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
26577 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
26578 can also be noted that the upper bounds are inclusive.
26580 As an example, assume that the register BND0 holds bounds for a pointer having
26581 access allowed for the range between 0x32 and 0x71. The values present on
26582 bnd0raw and bnd registers are presented as follows:
26585 bnd0raw = @{0x32, 0xffffffff8e@}
26586 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
26589 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
26590 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
26591 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
26592 Python, the display includes the memory size, in bits, accessible to
26595 Bounds can also be stored in bounds tables, which are stored in
26596 application memory. These tables store bounds for pointers by specifying
26597 the bounds pointer's value along with its bounds. Evaluating and changing
26598 bounds located in bound tables is therefore interesting while investigating
26599 bugs on MPX context. @value{GDBN} provides commands for this purpose:
26602 @item show mpx bound @var{pointer}
26603 @kindex show mpx bound
26604 Display bounds of the given @var{pointer}.
26606 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
26607 @kindex set mpx bound
26608 Set the bounds of a pointer in the bound table.
26609 This command takes three parameters: @var{pointer} is the pointers
26610 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
26611 for lower and upper bounds respectively.
26614 When you call an inferior function on an Intel MPX enabled program,
26615 GDB sets the inferior's bound registers to the init (disabled) state
26616 before calling the function. As a consequence, bounds checks for the
26617 pointer arguments passed to the function will always pass.
26619 This is necessary because when you call an inferior function, the
26620 program is usually in the middle of the execution of other function.
26621 Since at that point bound registers are in an arbitrary state, not
26622 clearing them would lead to random bound violations in the called
26625 You can still examine the influence of the bound registers on the
26626 execution of the called function by stopping the execution of the
26627 called function at its prologue, setting bound registers, and
26628 continuing the execution. For example:
26632 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
26633 $ print upper (a, b, c, d, 1)
26634 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
26636 @{lbound = 0x0, ubound = ffffffff@} : size -1
26639 At this last step the value of bnd0 can be changed for investigation of bound
26640 violations caused along the execution of the call. In order to know how to
26641 set the bound registers or bound table for the call consult the ABI.
26643 @subsubsection x87 registers
26645 @value{GDBN} provides access to the x87 state through the following registers:
26649 @item @code{$st0} to @code{st7}: @code{ST(0)} to @code{ST(7)} floating-point
26651 @item @code{$fctrl}: control word register (@code{FCW})
26652 @item @code{$fstat}: status word register (@code{FSW})
26653 @item @code{$ftag}: tag word (@code{FTW})
26654 @item @code{$fiseg}: last instruction pointer segment
26655 @item @code{$fioff}: last instruction pointer
26656 @item @code{$foseg}: last data pointer segment
26657 @item @code{$fooff}: last data pointer
26658 @item @code{$fop}: last opcode
26665 See the following section.
26668 @subsection @acronym{MIPS}
26670 @cindex stack on Alpha
26671 @cindex stack on @acronym{MIPS}
26672 @cindex Alpha stack
26673 @cindex @acronym{MIPS} stack
26674 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
26675 sometimes requires @value{GDBN} to search backward in the object code to
26676 find the beginning of a function.
26678 @cindex response time, @acronym{MIPS} debugging
26679 To improve response time (especially for embedded applications, where
26680 @value{GDBN} may be restricted to a slow serial line for this search)
26681 you may want to limit the size of this search, using one of these
26685 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
26686 @item set heuristic-fence-post @var{limit}
26687 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
26688 search for the beginning of a function. A value of @var{0} (the
26689 default) means there is no limit. However, except for @var{0}, the
26690 larger the limit the more bytes @code{heuristic-fence-post} must search
26691 and therefore the longer it takes to run. You should only need to use
26692 this command when debugging a stripped executable.
26694 @item show heuristic-fence-post
26695 Display the current limit.
26699 These commands are available @emph{only} when @value{GDBN} is configured
26700 for debugging programs on Alpha or @acronym{MIPS} processors.
26702 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
26706 @item set mips abi @var{arg}
26707 @kindex set mips abi
26708 @cindex set ABI for @acronym{MIPS}
26709 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
26710 values of @var{arg} are:
26714 The default ABI associated with the current binary (this is the
26724 @item show mips abi
26725 @kindex show mips abi
26726 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
26728 @item set mips compression @var{arg}
26729 @kindex set mips compression
26730 @cindex code compression, @acronym{MIPS}
26731 Tell @value{GDBN} which @acronym{MIPS} compressed
26732 @acronym{ISA, Instruction Set Architecture} encoding is used by the
26733 inferior. @value{GDBN} uses this for code disassembly and other
26734 internal interpretation purposes. This setting is only referred to
26735 when no executable has been associated with the debugging session or
26736 the executable does not provide information about the encoding it uses.
26737 Otherwise this setting is automatically updated from information
26738 provided by the executable.
26740 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
26741 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
26742 executables containing @acronym{MIPS16} code frequently are not
26743 identified as such.
26745 This setting is ``sticky''; that is, it retains its value across
26746 debugging sessions until reset either explicitly with this command or
26747 implicitly from an executable.
26749 The compiler and/or assembler typically add symbol table annotations to
26750 identify functions compiled for the @acronym{MIPS16} or
26751 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
26752 are present, @value{GDBN} uses them in preference to the global
26753 compressed @acronym{ISA} encoding setting.
26755 @item show mips compression
26756 @kindex show mips compression
26757 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
26758 @value{GDBN} to debug the inferior.
26761 @itemx show mipsfpu
26762 @xref{MIPS Embedded, set mipsfpu}.
26764 @item set mips mask-address @var{arg}
26765 @kindex set mips mask-address
26766 @cindex @acronym{MIPS} addresses, masking
26767 This command determines whether the most-significant 32 bits of 64-bit
26768 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
26769 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
26770 setting, which lets @value{GDBN} determine the correct value.
26772 @item show mips mask-address
26773 @kindex show mips mask-address
26774 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
26777 @item set remote-mips64-transfers-32bit-regs
26778 @kindex set remote-mips64-transfers-32bit-regs
26779 This command controls compatibility with 64-bit @acronym{MIPS} targets that
26780 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
26781 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
26782 and 64 bits for other registers, set this option to @samp{on}.
26784 @item show remote-mips64-transfers-32bit-regs
26785 @kindex show remote-mips64-transfers-32bit-regs
26786 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
26788 @item set debug mips
26789 @kindex set debug mips
26790 This command turns on and off debugging messages for the @acronym{MIPS}-specific
26791 target code in @value{GDBN}.
26793 @item show debug mips
26794 @kindex show debug mips
26795 Show the current setting of @acronym{MIPS} debugging messages.
26801 @cindex HPPA support
26803 When @value{GDBN} is debugging the HP PA architecture, it provides the
26804 following special commands:
26807 @item set debug hppa
26808 @kindex set debug hppa
26809 This command determines whether HPPA architecture-specific debugging
26810 messages are to be displayed.
26812 @item show debug hppa
26813 Show whether HPPA debugging messages are displayed.
26815 @item maint print unwind @var{address}
26816 @kindex maint print unwind@r{, HPPA}
26817 This command displays the contents of the unwind table entry at the
26818 given @var{address}.
26824 @subsection PowerPC
26825 @cindex PowerPC architecture
26827 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26828 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26829 numbers stored in the floating point registers. These values must be stored
26830 in two consecutive registers, always starting at an even register like
26831 @code{f0} or @code{f2}.
26833 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26834 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26835 @code{f2} and @code{f3} for @code{$dl1} and so on.
26837 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26838 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26841 @subsection Nios II
26842 @cindex Nios II architecture
26844 When @value{GDBN} is debugging the Nios II architecture,
26845 it provides the following special commands:
26849 @item set debug nios2
26850 @kindex set debug nios2
26851 This command turns on and off debugging messages for the Nios II
26852 target code in @value{GDBN}.
26854 @item show debug nios2
26855 @kindex show debug nios2
26856 Show the current setting of Nios II debugging messages.
26860 @subsection Sparc64
26861 @cindex Sparc64 support
26862 @cindex Application Data Integrity
26863 @subsubsection ADI Support
26865 The M7 processor supports an Application Data Integrity (ADI) feature that
26866 detects invalid data accesses. When software allocates memory and enables
26867 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26868 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26869 the 4-bit version in every cacheline of that data. Hardware saves the latter
26870 in spare bits in the cache and memory hierarchy. On each load and store,
26871 the processor compares the upper 4 VA (virtual address) bits to the
26872 cacheline's version. If there is a mismatch, the processor generates a
26873 version mismatch trap which can be either precise or disrupting. The trap
26874 is an error condition which the kernel delivers to the process as a SIGSEGV
26877 Note that only 64-bit applications can use ADI and need to be built with
26880 Values of the ADI version tags, which are in granularity of a
26881 cacheline (64 bytes), can be viewed or modified.
26885 @kindex adi examine
26886 @item adi (examine | x) [ / @var{n} ] @var{addr}
26888 The @code{adi examine} command displays the value of one ADI version tag per
26891 @var{n} is a decimal integer specifying the number in bytes; the default
26892 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26893 block size, to display.
26895 @var{addr} is the address in user address space where you want @value{GDBN}
26896 to begin displaying the ADI version tags.
26898 Below is an example of displaying ADI versions of variable "shmaddr".
26901 (@value{GDBP}) adi x/100 shmaddr
26902 0xfff800010002c000: 0 0
26906 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26908 The @code{adi assign} command is used to assign new ADI version tag
26911 @var{n} is a decimal integer specifying the number in bytes;
26912 the default is 1. It specifies how much ADI version information, at the
26913 ratio of 1:ADI block size, to modify.
26915 @var{addr} is the address in user address space where you want @value{GDBN}
26916 to begin modifying the ADI version tags.
26918 @var{tag} is the new ADI version tag.
26920 For example, do the following to modify then verify ADI versions of
26921 variable "shmaddr":
26924 (@value{GDBP}) adi a/100 shmaddr = 7
26925 (@value{GDBP}) adi x/100 shmaddr
26926 0xfff800010002c000: 7 7
26933 @cindex S12Z support
26935 When @value{GDBN} is debugging the S12Z architecture,
26936 it provides the following special command:
26939 @item maint info bdccsr
26940 @kindex maint info bdccsr@r{, S12Z}
26941 This command displays the current value of the microprocessor's
26946 @subsection @acronym{AMD GPU}
26947 @cindex @acronym{AMD GPU} support
26949 @value{GDBN} supports debugging programs offloaded to @acronym{AMD GPU} devices
26950 using the @url{https://docs.amd.com/, @acronym{AMD ROCm}} platform.
26951 @value{GDBN} presents host threads alongside GPU wavefronts, allowing debugging
26952 both the host and device parts of the program simultaneously.
26954 @subsubsection @acronym{AMD GPU} Architectures
26956 The list of @acronym{AMD GPU} architectures supported by @value{GDBN} depends
26957 on the version of the AMD Debugger API library used. See its
26958 @uref{https://docs.amd.com/bundle/ROCDebugger_User_and_API, documentation} for
26961 @subsubsection @acronym{AMD GPU} Device Driver and @acronym{AMD ROCm} Runtime
26963 @value{GDBN} requires a compatible @acronym{AMD GPU} device driver to
26964 be installed. A warning message is displayed if either the device
26965 driver version or the version of the debug support it implements is
26966 unsupported. @value{GDBN} will continue to function except no
26967 @acronym{AMD GPU} debugging will be possible.
26969 @value{GDBN} requires each agent to have compatible firmware installed
26970 by the device driver. A warning message is displayed if unsupported
26971 firmware is detected. @value{GDBN} will continue to function except
26972 no @acronym{AMD GPU} debugging will be possible on the agent.
26974 @value{GDBN} requires a compatible @acronym{AMD ROCm} runtime to be
26975 loaded in order to detect @acronym{AMD GPU} code objects and
26976 wavefronts. A warning message is displayed if an unsupported
26977 @acronym{AMD ROCm} runtime is detected, or there is an error or
26978 restriction that prevents debugging. @value{GDBN} will continue to
26979 function except no @acronym{AMD GPU} debugging will be possible.
26981 @subsubsection @acronym{AMD GPU} Wavefronts
26984 An @acronym{AMD GPU} wavefront is represented in @value{GDBN} as a
26987 Note that some @acronym{AMD GPU} architectures may have restrictions
26988 on providing information about @acronym{AMD GPU} wavefronts created
26989 when @value{GDBN} is not attached (@pxref{AMD GPU Attaching
26990 Restrictions, , @acronym{AMD GPU} Attaching Restrictions}).
26992 When scheduler-locking is in effect (@pxref{set scheduler-locking}),
26993 new wavefronts created by the resumed thread (either CPU thread or GPU
26994 wavefront) are held in the halt state.
26996 @subsubsection @acronym{AMD GPU} Code Objects
26998 The @samp{info sharedlibrary} command will show the @acronym{AMD GPU}
26999 code objects as file or memory URIs, together with the host's shared
27000 libraries. For example:
27003 (@value{GDBP}) info sharedlibrary
27004 From To Syms Read Shared Object Library
27005 0x1111 0x2222 Yes (*) /lib64/ld-linux-x86-64.so.2
27007 0x3333 0x4444 Yes (*) /opt/rocm-4.5.0/.../libamd_comgr.so
27008 0x5555 0x6666 Yes (*) /lib/x86_64-linux-gnu/libtinfo.so.5
27009 0x7777 0x8888 Yes file:///tmp/a.out#offset=6477&size=10832
27010 0x9999 0xaaaa Yes (*) memory://95557/mem#offset=0x1234&size=100
27011 (*): Shared library is missing debugging information.
27015 For a @samp{file} URI, the path portion is the file on disk containing
27016 the code object. The @var{offset} parameter is a 0-based offset in
27017 this file, to the start of the code object. If omitted, it defaults to
27018 0. The @var{size} parameter is the size of the code object in bytes.
27019 If omitted, it defaults to the size of the file.
27021 For a @samp{memory} URI, the path portion is the process id of the
27022 process owning the memory containing the code object. The @var{offset}
27023 parameter is the memory address where the code object is found, and
27024 the @var{size} parameter is its size in bytes.
27026 @acronym{AMD GPU} code objects are loaded into each @acronym{AMD GPU}
27027 device separately. The @samp{info sharedlibrary} command may
27028 therefore show the same code object loaded multiple times. As a
27029 consequence, setting a breakpoint in @acronym{AMD GPU} code will
27030 result in multiple breakpoint locations if there are multiple
27031 @acronym{AMD GPU} devices.
27033 @subsubsection @acronym{AMD GPU} Entity Target Identifiers and Convenience Variables
27035 The @acronym{AMD GPU} entities have the following target identifier formats:
27039 @item Thread Target ID
27040 The @acronym{AMD GPU} thread target identifier (@var{systag}) string has the
27044 AMDGPU Wave @var{agent-id}:@var{queue-id}:@var{dispatch-id}:@var{wave-id} (@var{work-group-x},@var{work-group-y},@var{work-group-z})/@var{work-group-thread-index}
27049 @anchor{AMD GPU Signals}
27050 @subsubsection @acronym{AMD GPU} Signals
27052 For @acronym{AMD GPU} wavefronts, @value{GDBN} maps target conditions to stop
27053 signals in the following way:
27058 Execution of an illegal instruction.
27061 Execution of a @code{S_TRAP} instruction other than:
27066 @code{S_TRAP 1} which is used by @value{GDBN} to insert breakpoints.
27069 @code{S_TRAP 2} which raises @code{SIGABRT}.
27074 Execution of a @code{S_TRAP 2} instruction.
27077 Execution of a floating point or integer instruction detects a
27078 condition that is enabled to raise a signal. The conditions include:
27083 Floating point operation is invalid.
27086 Floating point operation had subnormal input that was rounded to zero.
27089 Floating point operation performed a division by zero.
27092 Floating point operation produced an overflow result. The result was
27093 rounded to infinity.
27096 Floating point operation produced an underflow result. A subnormal
27097 result was rounded to zero.
27100 Floating point operation produced an inexact result.
27103 Integer operation performed a division by zero.
27107 By default, these conditions are not enabled to raise signals. The
27108 @samp{set $mode} command can be used to change the @acronym{AMD GPU}
27109 wavefront's register that has bits controlling which conditions are
27110 enabled to raise signals. The @samp{print $trapsts} command can be
27111 used to inspect which conditions have been detected even if they are
27112 not enabled to raise a signal.
27115 Execution of an instruction that accessed global memory using an
27116 address that is outside the virtual address range.
27119 Execution of an instruction that accessed a global memory page that is
27120 either not mapped or accessed with incompatible permissions.
27124 If a single instruction raises more than one signal, they will be
27125 reported one at a time each time the wavefront is continued.
27127 @subsubsection @acronym{AMD GPU} Memory Violation Reporting
27129 A wavefront can report memory violation events. However, the program
27130 location at which they are reported may be after the machine instruction
27131 that caused them. This can result in the reported source statement
27132 being incorrect. The following commands can be used to control this
27137 @kindex set amdgpu precise-memory
27138 @cindex AMD GPU precise memory event reporting
27139 @item set amdgpu precise-memory @var{mode}
27140 Controls how @acronym{AMD GPU} devices detect memory violations, where
27146 The program location may not be immediately after the instruction that
27147 caused the memory violation. This is the default.
27150 Requests that the program location will be immediately after the
27151 instruction that caused a memory violation. Enabling this mode may make
27152 the @acronym{AMD GPU} device execution significantly slower as it has to
27153 wait for each memory operation to complete before executing the next
27158 The @code{amdgpu precise-memory} parameter is per-inferior. When an
27159 inferior forks or execs, or the user uses the @code{clone-inferior} command,
27160 and an inferior is created as a result, the newly created inferior inherits
27161 the parameter value of the original inferior.
27163 @kindex show amdgpu precise-memory
27164 @cindex AMD GPU precise memory event reporting
27165 @item show amdgpu precise-memory
27166 Displays the currently requested AMD GPU precise memory setting.
27170 @subsubsection @acronym{AMD GPU} Logging
27172 The @samp{set debug amd-dbgapi} command can be used
27173 to enable diagnostic messages in the @samp{amd-dbgapi} target. The
27174 @samp{show debug amd-dbgapi} command displays the current setting.
27175 @xref{set debug amd-dbgapi}.
27177 The @samp{set debug amd-dbgapi-lib log-level @var{level}} command can be used
27178 to enable diagnostic messages from the @samp{amd-dbgapi} library (which
27179 @value{GDBN} uses under the hood). The @samp{show debug amd-dbgapi-lib
27180 log-level} command displays the current @samp{amd-dbgapi} library log level.
27181 @xref{set debug amd-dbgapi-lib}.
27183 @subsubsection @acronym{AMD GPU} Restrictions
27188 When in non-stop mode, wavefronts may not hit breakpoints inserted
27189 while not stopped, nor see memory updates made while not stopped,
27190 until the wavefront is next stopped. Memory updated by non-stopped
27191 wavefronts may not be visible until the wavefront is next stopped.
27193 @item The HIP runtime performs deferred code object loading by default.
27194 @acronym{AMD GPU} code objects are not loaded until the first kernel is
27195 launched. Before then, all breakpoints have to be set as pending breakpoints.
27197 If source line positions are used that only correspond to source lines in
27198 unloaded code objects, then @value{GDBN} may not set pending breakpoints, and
27199 instead set breakpoints on the next following source line that maps to host
27200 code. This can result in unexpected breakpoint hits being reported. When the
27201 code object containing the source lines is loaded, the incorrect breakpoints
27202 will be removed and replaced by the correct ones. This problem can be avoided
27203 by only setting breakpoints in unloaded code objects using symbol or function
27206 Setting the @code{HIP_ENABLE_DEFERRED_LOADING} environment variable to @code{0}
27207 can be used to disable deferred code object loading by the HIP runtime. This
27208 ensures all code objects will be loaded when the inferior reaches the beginning
27209 of the @code{main} function.
27212 If no CPU thread is running, then @samp{Ctrl-C} is not able to stop
27213 @acronym{AMD GPU} threads. This can happen for example if you enable
27214 @code{scheduler-locking} after the whole program stopped, and then resume an
27215 @acronym{AMD GPU} thread. The only way to unblock the situation is to kill the
27216 @value{GDBN} process.
27218 @anchor{AMD GPU Attaching Restrictions}
27221 By default, for some architectures, the @acronym{AMD GPU} device driver causes
27222 all @acronym{AMD GPU} wavefronts created when @value{GDBN} is not attached to
27223 be unable to report the dispatch associated with the wavefront, or the
27224 wavefront's work-group position. The @samp{info threads} command will display
27225 this missing information with a @samp{?}.
27227 This does not affect wavefronts created while @value{GDBN} is attached which
27228 are always capable of reporting this information.
27230 If the @env{HSA_ENABLE_DEBUG} environment variable is set to @samp{1} when the
27231 @acronym{AMD ROCm} runtime is initialized, then this information will be
27232 available for all architectures even for wavefronts created when @value{GDBN}
27237 @node Controlling GDB
27238 @chapter Controlling @value{GDBN}
27240 You can alter the way @value{GDBN} interacts with you by using the
27241 @code{set} command. For commands controlling how @value{GDBN} displays
27242 data, see @ref{Print Settings, ,Print Settings}. Other settings are
27247 * Editing:: Command editing
27248 * Command History:: Command history
27249 * Screen Size:: Screen size
27250 * Output Styling:: Output styling
27251 * Numbers:: Numbers
27252 * ABI:: Configuring the current ABI
27253 * Auto-loading:: Automatically loading associated files
27254 * Messages/Warnings:: Optional warnings and messages
27255 * Debugging Output:: Optional messages about internal happenings
27256 * Other Misc Settings:: Other Miscellaneous Settings
27264 @value{GDBN} indicates its readiness to read a command by printing a string
27265 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
27266 can change the prompt string with the @code{set prompt} command. For
27267 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
27268 the prompt in one of the @value{GDBN} sessions so that you can always tell
27269 which one you are talking to.
27271 @emph{Note:} @code{set prompt} does not add a space for you after the
27272 prompt you set. This allows you to set a prompt which ends in a space
27273 or a prompt that does not.
27277 @item set prompt @var{newprompt}
27278 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
27280 @kindex show prompt
27282 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
27285 Versions of @value{GDBN} that ship with Python scripting enabled have
27286 prompt extensions. The commands for interacting with these extensions
27290 @kindex set extended-prompt
27291 @item set extended-prompt @var{prompt}
27292 Set an extended prompt that allows for substitutions.
27293 @xref{gdb.prompt}, for a list of escape sequences that can be used for
27294 substitution. Any escape sequences specified as part of the prompt
27295 string are replaced with the corresponding strings each time the prompt
27301 set extended-prompt Current working directory: \w (@value{GDBP})
27304 Note that when an extended-prompt is set, it takes control of the
27305 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
27307 @kindex show extended-prompt
27308 @item show extended-prompt
27309 Prints the extended prompt. Any escape sequences specified as part of
27310 the prompt string with @code{set extended-prompt}, are replaced with the
27311 corresponding strings each time the prompt is displayed.
27315 @section Command Editing
27317 @cindex command line editing
27319 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
27320 @sc{gnu} library provides consistent behavior for programs which provide a
27321 command line interface to the user. Advantages are @sc{gnu} Emacs-style
27322 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
27323 substitution, and a storage and recall of command history across
27324 debugging sessions.
27326 You may control the behavior of command line editing in @value{GDBN} with the
27327 command @code{set}.
27330 @kindex set editing
27333 @itemx set editing on
27334 Enable command line editing (enabled by default).
27336 @item set editing off
27337 Disable command line editing.
27339 @kindex show editing
27341 Show whether command line editing is enabled.
27344 @ifset SYSTEM_READLINE
27345 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
27347 @ifclear SYSTEM_READLINE
27348 @xref{Command Line Editing},
27350 for more details about the Readline
27351 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
27352 encouraged to read that chapter.
27354 @cindex Readline application name
27355 @value{GDBN} sets the Readline application name to @samp{gdb}. This
27356 is useful for conditions in @file{.inputrc}.
27358 @cindex operate-and-get-next
27359 @value{GDBN} defines a bindable Readline command,
27360 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
27361 This command accepts the current line for execution and fetches the
27362 next line relative to the current line from the history for editing.
27363 Any argument is ignored.
27365 @node Command History
27366 @section Command History
27367 @cindex command history
27369 @value{GDBN} can keep track of the commands you type during your
27370 debugging sessions, so that you can be certain of precisely what
27371 happened. Use these commands to manage the @value{GDBN} command
27374 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
27375 package, to provide the history facility.
27376 @ifset SYSTEM_READLINE
27377 @xref{Using History Interactively, , , history, GNU History Library},
27379 @ifclear SYSTEM_READLINE
27380 @xref{Using History Interactively},
27382 for the detailed description of the History library.
27384 To issue a command to @value{GDBN} without affecting certain aspects of
27385 the state which is seen by users, prefix it with @samp{server }
27386 (@pxref{Server Prefix}). This
27387 means that this command will not affect the command history, nor will it
27388 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
27389 pressed on a line by itself.
27391 @cindex @code{server}, command prefix
27392 The server prefix does not affect the recording of values into the value
27393 history; to print a value without recording it into the value history,
27394 use the @code{output} command instead of the @code{print} command.
27396 Here is the description of @value{GDBN} commands related to command
27400 @cindex history substitution
27401 @cindex history file
27402 @kindex set history filename
27403 @cindex @env{GDBHISTFILE}, environment variable
27404 @item set history filename @r{[}@var{fname}@r{]}
27405 Set the name of the @value{GDBN} command history file to @var{fname}.
27406 This is the file where @value{GDBN} reads an initial command history
27407 list, and where it writes the command history from this session when it
27408 exits. You can access this list through history expansion or through
27409 the history command editing characters listed below. This file defaults
27410 to the value of the environment variable @env{GDBHISTFILE}, or to
27411 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
27414 The @env{GDBHISTFILE} environment variable is read after processing
27415 any @value{GDBN} initialization files (@pxref{Startup}) and after
27416 processing any commands passed using command line options (for
27417 example, @code{-ex}).
27419 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
27420 is the empty string then @value{GDBN} will neither try to load an
27421 existing history file, nor will it try to save the history on exit.
27423 @cindex save command history
27424 @kindex set history save
27425 @item set history save
27426 @itemx set history save on
27427 Record command history in a file, whose name may be specified with the
27428 @code{set history filename} command. By default, this option is
27429 disabled. The command history will be recorded when @value{GDBN}
27430 exits. If @code{set history filename} is set to the empty string then
27431 history saving is disabled, even when @code{set history save} is
27434 @item set history save off
27435 Don't record the command history into the file specified by @code{set
27436 history filename} when @value{GDBN} exits.
27438 @cindex history size
27439 @kindex set history size
27440 @cindex @env{GDBHISTSIZE}, environment variable
27441 @item set history size @var{size}
27442 @itemx set history size unlimited
27443 Set the number of commands which @value{GDBN} keeps in its history list.
27444 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
27445 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
27446 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
27447 either a negative number or the empty string, then the number of commands
27448 @value{GDBN} keeps in the history list is unlimited.
27450 The @env{GDBHISTSIZE} environment variable is read after processing
27451 any @value{GDBN} initialization files (@pxref{Startup}) and after
27452 processing any commands passed using command line options (for
27453 example, @code{-ex}).
27455 @cindex remove duplicate history
27456 @kindex set history remove-duplicates
27457 @item set history remove-duplicates @var{count}
27458 @itemx set history remove-duplicates unlimited
27459 Control the removal of duplicate history entries in the command history list.
27460 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
27461 history entries and remove the first entry that is a duplicate of the current
27462 entry being added to the command history list. If @var{count} is
27463 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
27464 removal of duplicate history entries is disabled.
27466 Only history entries added during the current session are considered for
27467 removal. This option is set to 0 by default.
27471 History expansion assigns special meaning to the character @kbd{!}.
27472 @ifset SYSTEM_READLINE
27473 @xref{Event Designators, , , history, GNU History Library},
27475 @ifclear SYSTEM_READLINE
27476 @xref{Event Designators},
27480 @cindex history expansion, turn on/off
27481 Since @kbd{!} is also the logical not operator in C, history expansion
27482 is off by default. If you decide to enable history expansion with the
27483 @code{set history expansion on} command, you may sometimes need to
27484 follow @kbd{!} (when it is used as logical not, in an expression) with
27485 a space or a tab to prevent it from being expanded. The readline
27486 history facilities do not attempt substitution on the strings
27487 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
27489 The commands to control history expansion are:
27492 @item set history expansion on
27493 @itemx set history expansion
27494 @kindex set history expansion
27495 Enable history expansion. History expansion is off by default.
27497 @item set history expansion off
27498 Disable history expansion.
27501 @kindex show history
27503 @itemx show history filename
27504 @itemx show history save
27505 @itemx show history size
27506 @itemx show history expansion
27507 These commands display the state of the @value{GDBN} history parameters.
27508 @code{show history} by itself displays all four states.
27513 @kindex show commands
27514 @cindex show last commands
27515 @cindex display command history
27516 @item show commands
27517 Display the last ten commands in the command history.
27519 @item show commands @var{n}
27520 Print ten commands centered on command number @var{n}.
27522 @item show commands +
27523 Print ten commands just after the commands last printed.
27527 @section Screen Size
27528 @cindex size of screen
27529 @cindex screen size
27532 @cindex pauses in output
27534 Certain commands to @value{GDBN} may produce large amounts of
27535 information output to the screen. To help you read all of it,
27536 @value{GDBN} pauses and asks you for input at the end of each page of
27537 output. Type @key{RET} when you want to see one more page of output,
27538 @kbd{q} to discard the remaining output, or @kbd{c} to continue
27539 without paging for the rest of the current command. Also, the screen
27540 width setting determines when to wrap lines of output. Depending on
27541 what is being printed, @value{GDBN} tries to break the line at a
27542 readable place, rather than simply letting it overflow onto the
27545 Normally @value{GDBN} knows the size of the screen from the terminal
27546 driver software. For example, on Unix @value{GDBN} uses the termcap data base
27547 together with the value of the @env{TERM} environment variable and the
27548 @code{stty rows} and @code{stty cols} settings. If this is not correct,
27549 you can override it with the @code{set height} and @code{set
27556 @kindex show height
27557 @item set height @var{lpp}
27558 @itemx set height unlimited
27560 @itemx set width @var{cpl}
27561 @itemx set width unlimited
27563 These @code{set} commands specify a screen height of @var{lpp} lines and
27564 a screen width of @var{cpl} characters. The associated @code{show}
27565 commands display the current settings.
27567 If you specify a height of either @code{unlimited} or zero lines,
27568 @value{GDBN} does not pause during output no matter how long the
27569 output is. This is useful if output is to a file or to an editor
27572 Likewise, you can specify @samp{set width unlimited} or @samp{set
27573 width 0} to prevent @value{GDBN} from wrapping its output.
27575 @item set pagination on
27576 @itemx set pagination off
27577 @kindex set pagination
27578 Turn the output pagination on or off; the default is on. Turning
27579 pagination off is the alternative to @code{set height unlimited}. Note that
27580 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
27581 Options, -batch}) also automatically disables pagination.
27583 @item show pagination
27584 @kindex show pagination
27585 Show the current pagination mode.
27588 @node Output Styling
27589 @section Output Styling
27595 @value{GDBN} can style its output on a capable terminal. This is
27596 enabled by default on most systems, but disabled by default when in
27597 batch mode (@pxref{Mode Options}). Various style settings are available;
27598 and styles can also be disabled entirely.
27601 @item set style enabled @samp{on|off}
27602 Enable or disable all styling. The default is host-dependent, with
27603 most hosts defaulting to @samp{on}.
27605 If the @env{NO_COLOR} environment variable is set to a non-empty
27606 value, then @value{GDBN} will change this to @samp{off} at startup.
27608 @item show style enabled
27609 Show the current state of styling.
27611 @item set style sources @samp{on|off}
27612 Enable or disable source code styling. This affects whether source
27613 code, such as the output of the @code{list} command, is styled. The
27614 default is @samp{on}. Note that source styling only works if styling
27615 in general is enabled, and if a source highlighting library is
27616 available to @value{GDBN}.
27618 There are two ways that highlighting can be done. First, if
27619 @value{GDBN} was linked with the GNU Source Highlight library, then it
27620 is used. Otherwise, if @value{GDBN} was configured with Python
27621 scripting support, and if the Python Pygments package is available,
27622 then it will be used.
27624 @item show style sources
27625 Show the current state of source code styling.
27627 @item set style tui-current-position @samp{on|off}
27628 Enable or disable styling of the source and assembly code highlighted
27629 by the TUI's current position indicator. The default is @samp{off}.
27630 @xref{TUI, ,@value{GDBN} Text User Interface}.
27632 @item show style tui-current-position
27633 Show whether the source and assembly code highlighted by the TUI's
27634 current position indicator is styled.
27636 @anchor{style_disassembler_enabled}
27637 @item set style disassembler enabled @samp{on|off}
27638 Enable or disable disassembler styling. This affects whether
27639 disassembler output, such as the output of the @code{disassemble}
27640 command, is styled. Disassembler styling only works if styling in
27641 general is enabled (with @code{set style enabled on}), and if a source
27642 highlighting library is available to @value{GDBN}.
27644 The two source highlighting libraries that @value{GDBN} could use to
27645 style disassembler output are; @value{GDBN}'s builtin disassembler, or
27646 the Python Pygments package.
27648 @value{GDBN}'s first choice will be to use the builtin disassembler
27649 for styling, this usually provides better results, being able to style
27650 different types of instruction operands differently. However, the
27651 builtin disassembler is not able to style all architectures.
27653 For architectures that the builtin disassembler is unable to style,
27654 @value{GDBN} will fall back to use the Python Pygments package where
27655 possible. In order to use the Python Pygments package, @value{GDBN}
27656 must be built with Python support, and the Pygments package must be
27659 If neither of these options are available then @value{GDBN} will
27660 produce unstyled disassembler output, even when this setting is
27663 To discover if the current architecture supports styling using the
27664 builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
27665 show libopcodes-styling enabled}}.
27667 @item show style disassembler enabled
27668 Show the current state of disassembler styling.
27672 Subcommands of @code{set style} control specific forms of styling.
27673 These subcommands all follow the same pattern: each style-able object
27674 can be styled with a foreground color, a background color, and an
27677 For example, the style of file names can be controlled using the
27678 @code{set style filename} group of commands:
27681 @item set style filename background @var{color}
27682 Set the background to @var{color}. Valid colors are @samp{none}
27683 (meaning the terminal's default color), @samp{black}, @samp{red},
27684 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
27687 @item set style filename foreground @var{color}
27688 Set the foreground to @var{color}. Valid colors are @samp{none}
27689 (meaning the terminal's default color), @samp{black}, @samp{red},
27690 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
27693 @item set style filename intensity @var{value}
27694 Set the intensity to @var{value}. Valid intensities are @samp{normal}
27695 (the default), @samp{bold}, and @samp{dim}.
27698 The @code{show style} command and its subcommands are styling
27699 a style name in their output using its own style.
27700 So, use @command{show style} to see the complete list of styles,
27701 their characteristics and the visual aspect of each style.
27703 The style-able objects are:
27706 Control the styling of file names and URLs. By default, this style's
27707 foreground color is green.
27710 Control the styling of function names. These are managed with the
27711 @code{set style function} family of commands. By default, this
27712 style's foreground color is yellow.
27714 This style is also used for symbol names in styled disassembler output
27715 if @value{GDBN} is using its builtin disassembler library for styling
27716 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
27720 Control the styling of variable names. These are managed with the
27721 @code{set style variable} family of commands. By default, this style's
27722 foreground color is cyan.
27725 Control the styling of addresses. These are managed with the
27726 @code{set style address} family of commands. By default, this style's
27727 foreground color is blue.
27729 This style is also used for addresses in styled disassembler output
27730 if @value{GDBN} is using its builtin disassembler library for styling
27731 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
27735 Control the styling of @value{GDBN}'s version number text. By
27736 default, this style's foreground color is magenta and it has bold
27737 intensity. The version number is displayed in two places, the output
27738 of @command{show version}, and when @value{GDBN} starts up.
27740 In order to control how @value{GDBN} styles the version number at
27741 startup, add the @code{set style version} family of commands to the
27742 early initialization command file (@pxref{Initialization
27746 Control the styling of titles. These are managed with the
27747 @code{set style title} family of commands. By default, this style's
27748 intensity is bold. Commands are using the title style to improve
27749 the readability of large output. For example, the commands
27750 @command{apropos} and @command{help} are using the title style
27751 for the command names.
27754 Control the styling of highlightings. These are managed with the
27755 @code{set style highlight} family of commands. By default, this style's
27756 foreground color is red. Commands are using the highlight style to draw
27757 the user attention to some specific parts of their output. For example,
27758 the command @command{apropos -v REGEXP} uses the highlight style to
27759 mark the documentation parts matching @var{regexp}.
27762 Control the styling of data annotations added by @value{GDBN} to data
27763 it displays. By default, this style's intensity is dim. Metadata
27764 annotations include the @samp{repeats @var{n} times} annotation for
27765 suppressed display of repeated array elements (@pxref{Print Settings}),
27766 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
27767 for errors and @samp{<optimized-out>} annotations for optimized-out
27768 values in displaying stack frame information in backtraces
27769 (@pxref{Backtrace}), etc.
27772 Control the styling of the TUI border. Note that, unlike other
27773 styling options, only the color of the border can be controlled via
27774 @code{set style}. This was done for compatibility reasons, as TUI
27775 controls to set the border's intensity predated the addition of
27776 general styling to @value{GDBN}. @xref{TUI Configuration}.
27778 @item tui-active-border
27779 Control the styling of the active TUI border; that is, the TUI window
27780 that has the focus.
27782 @item disassembler comment
27783 Control the styling of comments in the disassembler output. These are
27784 managed with the @code{set style disassembler comment} family of
27785 commands. This style is only used when @value{GDBN} is styling using
27786 its builtin disassembler library
27787 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
27788 enabled}}). By default, this style's intensity is dim, and its
27789 foreground color is white.
27791 @item disassembler immediate
27792 Control the styling of numeric operands in the disassembler output.
27793 These are managed with the @code{set style disassembler immediate}
27794 family of commands. This style is not used for instruction operands
27795 that represent addresses, in that case the @samp{disassembler address}
27796 style is used. This style is only used when @value{GDBN} is styling
27797 using its builtin disassembler library. By default, this style's
27798 foreground color is blue.
27800 @item disassembler address
27801 Control the styling of address operands in the disassembler output.
27802 This is an alias for the @samp{address} style.
27804 @item disassembler symbol
27805 Control the styling of symbol names in the disassembler output. This
27806 is an alias for the @samp{function} style.
27808 @item disassembler mnemonic
27809 Control the styling of instruction mnemonics in the disassembler
27810 output. These are managed with the @code{set style disassembler
27811 mnemonic} family of commands. This style is also used for assembler
27812 directives, e.g.@: @code{.byte}, @code{.word}, etc. This style is
27813 only used when @value{GDBN} is styling using its builtin disassembler
27814 library. By default, this style's foreground color is green.
27816 @item disassembler register
27817 Control the styling of register operands in the disassembler output.
27818 These are managed with the @code{set style disassembler register}
27819 family of commands. This style is only used when @value{GDBN} is
27820 styling using its builtin disassembler library. By default, this style's
27821 foreground color is red.
27827 @cindex number representation
27828 @cindex entering numbers
27830 You can always enter numbers in octal, decimal, or hexadecimal in
27831 @value{GDBN} by the usual conventions: octal numbers begin with
27832 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
27833 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
27834 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
27835 10; likewise, the default display for numbers---when no particular
27836 format is specified---is base 10. You can change the default base for
27837 both input and output with the commands described below.
27840 @kindex set input-radix
27841 @item set input-radix @var{base}
27842 Set the default base for numeric input. Supported choices
27843 for @var{base} are decimal 8, 10, or 16. The base must itself be
27844 specified either unambiguously or using the current input radix; for
27848 set input-radix 012
27849 set input-radix 10.
27850 set input-radix 0xa
27854 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
27855 leaves the input radix unchanged, no matter what it was, since
27856 @samp{10}, being without any leading or trailing signs of its base, is
27857 interpreted in the current radix. Thus, if the current radix is 16,
27858 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
27861 @kindex set output-radix
27862 @item set output-radix @var{base}
27863 Set the default base for numeric display. Supported choices
27864 for @var{base} are decimal 8, 10, or 16. The base must itself be
27865 specified either unambiguously or using the current input radix.
27867 @kindex show input-radix
27868 @item show input-radix
27869 Display the current default base for numeric input.
27871 @kindex show output-radix
27872 @item show output-radix
27873 Display the current default base for numeric display.
27875 @item set radix @r{[}@var{base}@r{]}
27879 These commands set and show the default base for both input and output
27880 of numbers. @code{set radix} sets the radix of input and output to
27881 the same base; without an argument, it resets the radix back to its
27882 default value of 10.
27887 @section Configuring the Current ABI
27889 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
27890 application automatically. However, sometimes you need to override its
27891 conclusions. Use these commands to manage @value{GDBN}'s view of the
27897 @cindex Newlib OS ABI and its influence on the longjmp handling
27899 One @value{GDBN} configuration can debug binaries for multiple operating
27900 system targets, either via remote debugging or native emulation.
27901 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
27902 but you can override its conclusion using the @code{set osabi} command.
27903 One example where this is useful is in debugging of binaries which use
27904 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
27905 not have the same identifying marks that the standard C library for your
27908 When @value{GDBN} is debugging the AArch64 architecture, it provides a
27909 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
27910 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
27911 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
27915 Show the OS ABI currently in use.
27918 With no argument, show the list of registered available OS ABI's.
27920 @item set osabi @var{abi}
27921 Set the current OS ABI to @var{abi}.
27924 @cindex float promotion
27926 Generally, the way that an argument of type @code{float} is passed to a
27927 function depends on whether the function is prototyped. For a prototyped
27928 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
27929 according to the architecture's convention for @code{float}. For unprototyped
27930 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
27931 @code{double} and then passed.
27933 Unfortunately, some forms of debug information do not reliably indicate whether
27934 a function is prototyped. If @value{GDBN} calls a function that is not marked
27935 as prototyped, it consults @kbd{set coerce-float-to-double}.
27938 @kindex set coerce-float-to-double
27939 @item set coerce-float-to-double
27940 @itemx set coerce-float-to-double on
27941 Arguments of type @code{float} will be promoted to @code{double} when passed
27942 to an unprototyped function. This is the default setting.
27944 @item set coerce-float-to-double off
27945 Arguments of type @code{float} will be passed directly to unprototyped
27948 @kindex show coerce-float-to-double
27949 @item show coerce-float-to-double
27950 Show the current setting of promoting @code{float} to @code{double}.
27954 @kindex show cp-abi
27955 @value{GDBN} needs to know the ABI used for your program's C@t{++}
27956 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
27957 used to build your application. @value{GDBN} only fully supports
27958 programs with a single C@t{++} ABI; if your program contains code using
27959 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
27960 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
27961 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
27962 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
27963 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
27964 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
27969 Show the C@t{++} ABI currently in use.
27972 With no argument, show the list of supported C@t{++} ABI's.
27974 @item set cp-abi @var{abi}
27975 @itemx set cp-abi auto
27976 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
27980 @section Automatically loading associated files
27981 @cindex auto-loading
27983 @value{GDBN} sometimes reads files with commands and settings automatically,
27984 without being explicitly told so by the user. We call this feature
27985 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
27986 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
27987 results or introduce security risks (e.g., if the file comes from untrusted
27990 There are various kinds of files @value{GDBN} can automatically load.
27991 In addition to these files, @value{GDBN} supports auto-loading code written
27992 in various extension languages. @xref{Auto-loading extensions}.
27994 Note that loading of these associated files (including the local @file{.gdbinit}
27995 file) requires accordingly configured @code{auto-load safe-path}
27996 (@pxref{Auto-loading safe path}).
27998 For these reasons, @value{GDBN} includes commands and options to let you
27999 control when to auto-load files and which files should be auto-loaded.
28002 @anchor{set auto-load off}
28003 @kindex set auto-load off
28004 @item set auto-load off
28005 Globally disable loading of all auto-loaded files.
28006 You may want to use this command with the @samp{-iex} option
28007 (@pxref{Option -init-eval-command}) such as:
28009 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
28012 Be aware that system init file (@pxref{System-wide configuration})
28013 and init files from your home directory (@pxref{Home Directory Init File})
28014 still get read (as they come from generally trusted directories).
28015 To prevent @value{GDBN} from auto-loading even those init files, use the
28016 @option{-nx} option (@pxref{Mode Options}), in addition to
28017 @code{set auto-load no}.
28019 @anchor{show auto-load}
28020 @kindex show auto-load
28021 @item show auto-load
28022 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
28026 (@value{GDBP}) show auto-load
28027 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
28028 libthread-db: Auto-loading of inferior specific libthread_db is on.
28029 local-gdbinit: Auto-loading of .gdbinit script from current directory
28031 python-scripts: Auto-loading of Python scripts is on.
28032 safe-path: List of directories from which it is safe to auto-load files
28033 is $debugdir:$datadir/auto-load.
28034 scripts-directory: List of directories from which to load auto-loaded scripts
28035 is $debugdir:$datadir/auto-load.
28038 @anchor{info auto-load}
28039 @kindex info auto-load
28040 @item info auto-load
28041 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
28045 (@value{GDBP}) info auto-load
28048 Yes /home/user/gdb/gdb-gdb.gdb
28049 libthread-db: No auto-loaded libthread-db.
28050 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
28054 Yes /home/user/gdb/gdb-gdb.py
28058 These are @value{GDBN} control commands for the auto-loading:
28060 @multitable @columnfractions .5 .5
28061 @item @xref{set auto-load off}.
28062 @tab Disable auto-loading globally.
28063 @item @xref{show auto-load}.
28064 @tab Show setting of all kinds of files.
28065 @item @xref{info auto-load}.
28066 @tab Show state of all kinds of files.
28067 @item @xref{set auto-load gdb-scripts}.
28068 @tab Control for @value{GDBN} command scripts.
28069 @item @xref{show auto-load gdb-scripts}.
28070 @tab Show setting of @value{GDBN} command scripts.
28071 @item @xref{info auto-load gdb-scripts}.
28072 @tab Show state of @value{GDBN} command scripts.
28073 @item @xref{set auto-load python-scripts}.
28074 @tab Control for @value{GDBN} Python scripts.
28075 @item @xref{show auto-load python-scripts}.
28076 @tab Show setting of @value{GDBN} Python scripts.
28077 @item @xref{info auto-load python-scripts}.
28078 @tab Show state of @value{GDBN} Python scripts.
28079 @item @xref{set auto-load guile-scripts}.
28080 @tab Control for @value{GDBN} Guile scripts.
28081 @item @xref{show auto-load guile-scripts}.
28082 @tab Show setting of @value{GDBN} Guile scripts.
28083 @item @xref{info auto-load guile-scripts}.
28084 @tab Show state of @value{GDBN} Guile scripts.
28085 @item @xref{set auto-load scripts-directory}.
28086 @tab Control for @value{GDBN} auto-loaded scripts location.
28087 @item @xref{show auto-load scripts-directory}.
28088 @tab Show @value{GDBN} auto-loaded scripts location.
28089 @item @xref{add-auto-load-scripts-directory}.
28090 @tab Add directory for auto-loaded scripts location list.
28091 @item @xref{set auto-load local-gdbinit}.
28092 @tab Control for init file in the current directory.
28093 @item @xref{show auto-load local-gdbinit}.
28094 @tab Show setting of init file in the current directory.
28095 @item @xref{info auto-load local-gdbinit}.
28096 @tab Show state of init file in the current directory.
28097 @item @xref{set auto-load libthread-db}.
28098 @tab Control for thread debugging library.
28099 @item @xref{show auto-load libthread-db}.
28100 @tab Show setting of thread debugging library.
28101 @item @xref{info auto-load libthread-db}.
28102 @tab Show state of thread debugging library.
28103 @item @xref{set auto-load safe-path}.
28104 @tab Control directories trusted for automatic loading.
28105 @item @xref{show auto-load safe-path}.
28106 @tab Show directories trusted for automatic loading.
28107 @item @xref{add-auto-load-safe-path}.
28108 @tab Add directory trusted for automatic loading.
28112 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
28113 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
28115 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
28116 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
28119 @node Init File in the Current Directory
28120 @subsection Automatically loading init file in the current directory
28121 @cindex auto-loading init file in the current directory
28123 By default, @value{GDBN} reads and executes the canned sequences of commands
28124 from init file (if any) in the current working directory,
28125 see @ref{Init File in the Current Directory during Startup}.
28127 Note that loading of this local @file{.gdbinit} file also requires accordingly
28128 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28131 @anchor{set auto-load local-gdbinit}
28132 @kindex set auto-load local-gdbinit
28133 @item set auto-load local-gdbinit [on|off]
28134 Enable or disable the auto-loading of canned sequences of commands
28135 (@pxref{Sequences}) found in init file in the current directory.
28137 @anchor{show auto-load local-gdbinit}
28138 @kindex show auto-load local-gdbinit
28139 @item show auto-load local-gdbinit
28140 Show whether auto-loading of canned sequences of commands from init file in the
28141 current directory is enabled or disabled.
28143 @anchor{info auto-load local-gdbinit}
28144 @kindex info auto-load local-gdbinit
28145 @item info auto-load local-gdbinit
28146 Print whether canned sequences of commands from init file in the
28147 current directory have been auto-loaded.
28150 @node libthread_db.so.1 file
28151 @subsection Automatically loading thread debugging library
28152 @cindex auto-loading libthread_db.so.1
28154 This feature is currently present only on @sc{gnu}/Linux native hosts.
28156 @value{GDBN} reads in some cases thread debugging library from places specific
28157 to the inferior (@pxref{set libthread-db-search-path}).
28159 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
28160 without checking this @samp{set auto-load libthread-db} switch as system
28161 libraries have to be trusted in general. In all other cases of
28162 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
28163 auto-load libthread-db} is enabled before trying to open such thread debugging
28166 Note that loading of this debugging library also requires accordingly configured
28167 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28170 @anchor{set auto-load libthread-db}
28171 @kindex set auto-load libthread-db
28172 @item set auto-load libthread-db [on|off]
28173 Enable or disable the auto-loading of inferior specific thread debugging library.
28175 @anchor{show auto-load libthread-db}
28176 @kindex show auto-load libthread-db
28177 @item show auto-load libthread-db
28178 Show whether auto-loading of inferior specific thread debugging library is
28179 enabled or disabled.
28181 @anchor{info auto-load libthread-db}
28182 @kindex info auto-load libthread-db
28183 @item info auto-load libthread-db
28184 Print the list of all loaded inferior specific thread debugging libraries and
28185 for each such library print list of inferior @var{pid}s using it.
28188 @node Auto-loading safe path
28189 @subsection Security restriction for auto-loading
28190 @cindex auto-loading safe-path
28192 As the files of inferior can come from untrusted source (such as submitted by
28193 an application user) @value{GDBN} does not always load any files automatically.
28194 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
28195 directories trusted for loading files not explicitly requested by user.
28196 Each directory can also be a shell wildcard pattern.
28198 If the path is not set properly you will see a warning and the file will not
28203 Reading symbols from /home/user/gdb/gdb...
28204 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
28205 declined by your `auto-load safe-path' set
28206 to "$debugdir:$datadir/auto-load".
28207 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
28208 declined by your `auto-load safe-path' set
28209 to "$debugdir:$datadir/auto-load".
28213 To instruct @value{GDBN} to go ahead and use the init files anyway,
28214 invoke @value{GDBN} like this:
28217 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
28220 The list of trusted directories is controlled by the following commands:
28223 @anchor{set auto-load safe-path}
28224 @kindex set auto-load safe-path
28225 @item set auto-load safe-path @r{[}@var{directories}@r{]}
28226 Set the list of directories (and their subdirectories) trusted for automatic
28227 loading and execution of scripts. You can also enter a specific trusted file.
28228 Each directory can also be a shell wildcard pattern; wildcards do not match
28229 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
28230 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
28231 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
28232 its default value as specified during @value{GDBN} compilation.
28234 The list of directories uses path separator (@samp{:} on GNU and Unix
28235 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28236 to the @env{PATH} environment variable.
28238 @anchor{show auto-load safe-path}
28239 @kindex show auto-load safe-path
28240 @item show auto-load safe-path
28241 Show the list of directories trusted for automatic loading and execution of
28244 @anchor{add-auto-load-safe-path}
28245 @kindex add-auto-load-safe-path
28246 @item add-auto-load-safe-path
28247 Add an entry (or list of entries) to the list of directories trusted for
28248 automatic loading and execution of scripts. Multiple entries may be delimited
28249 by the host platform path separator in use.
28252 This variable defaults to what @code{--with-auto-load-dir} has been configured
28253 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
28254 substitution applies the same as for @ref{set auto-load scripts-directory}.
28255 The default @code{set auto-load safe-path} value can be also overriden by
28256 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
28258 Setting this variable to @file{/} disables this security protection,
28259 corresponding @value{GDBN} configuration option is
28260 @option{--without-auto-load-safe-path}.
28261 This variable is supposed to be set to the system directories writable by the
28262 system superuser only. Users can add their source directories in init files in
28263 their home directories (@pxref{Home Directory Init File}). See also deprecated
28264 init file in the current directory
28265 (@pxref{Init File in the Current Directory during Startup}).
28267 To force @value{GDBN} to load the files it declined to load in the previous
28268 example, you could use one of the following ways:
28271 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
28272 Specify this trusted directory (or a file) as additional component of the list.
28273 You have to specify also any existing directories displayed by
28274 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
28276 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
28277 Specify this directory as in the previous case but just for a single
28278 @value{GDBN} session.
28280 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
28281 Disable auto-loading safety for a single @value{GDBN} session.
28282 This assumes all the files you debug during this @value{GDBN} session will come
28283 from trusted sources.
28285 @item @kbd{./configure --without-auto-load-safe-path}
28286 During compilation of @value{GDBN} you may disable any auto-loading safety.
28287 This assumes all the files you will ever debug with this @value{GDBN} come from
28291 On the other hand you can also explicitly forbid automatic files loading which
28292 also suppresses any such warning messages:
28295 @item @kbd{gdb -iex "set auto-load no" @dots{}}
28296 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
28298 @item @file{~/.gdbinit}: @samp{set auto-load no}
28299 Disable auto-loading globally for the user
28300 (@pxref{Home Directory Init File}). While it is improbable, you could also
28301 use system init file instead (@pxref{System-wide configuration}).
28304 This setting applies to the file names as entered by user. If no entry matches
28305 @value{GDBN} tries as a last resort to also resolve all the file names into
28306 their canonical form (typically resolving symbolic links) and compare the
28307 entries again. @value{GDBN} already canonicalizes most of the filenames on its
28308 own before starting the comparison so a canonical form of directories is
28309 recommended to be entered.
28311 @node Auto-loading verbose mode
28312 @subsection Displaying files tried for auto-load
28313 @cindex auto-loading verbose mode
28315 For better visibility of all the file locations where you can place scripts to
28316 be auto-loaded with inferior --- or to protect yourself against accidental
28317 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
28318 all the files attempted to be loaded. Both existing and non-existing files may
28321 For example the list of directories from which it is safe to auto-load files
28322 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
28323 may not be too obvious while setting it up.
28326 (@value{GDBP}) set debug auto-load on
28327 (@value{GDBP}) file ~/src/t/true
28328 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
28329 for objfile "/tmp/true".
28330 auto-load: Updating directories of "/usr:/opt".
28331 auto-load: Using directory "/usr".
28332 auto-load: Using directory "/opt".
28333 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
28334 by your `auto-load safe-path' set to "/usr:/opt".
28338 @anchor{set debug auto-load}
28339 @kindex set debug auto-load
28340 @item set debug auto-load [on|off]
28341 Set whether to print the filenames attempted to be auto-loaded.
28343 @anchor{show debug auto-load}
28344 @kindex show debug auto-load
28345 @item show debug auto-load
28346 Show whether printing of the filenames attempted to be auto-loaded is turned
28350 @node Messages/Warnings
28351 @section Optional Warnings and Messages
28353 @cindex verbose operation
28354 @cindex optional warnings
28355 By default, @value{GDBN} is silent about its inner workings. If you are
28356 running on a slow machine, you may want to use the @code{set verbose}
28357 command. This makes @value{GDBN} tell you when it does a lengthy
28358 internal operation, so you will not think it has crashed.
28360 Currently, the messages controlled by @code{set verbose} are those
28361 which announce that the symbol table for a source file is being read;
28362 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
28365 @kindex set verbose
28366 @item set verbose on
28367 Enables @value{GDBN} output of certain informational messages.
28369 @item set verbose off
28370 Disables @value{GDBN} output of certain informational messages.
28372 @kindex show verbose
28374 Displays whether @code{set verbose} is on or off.
28377 By default, if @value{GDBN} encounters bugs in the symbol table of an
28378 object file, it is silent; but if you are debugging a compiler, you may
28379 find this information useful (@pxref{Symbol Errors, ,Errors Reading
28384 @kindex set complaints
28385 @item set complaints @var{limit}
28386 Permits @value{GDBN} to output @var{limit} complaints about each type of
28387 unusual symbols before becoming silent about the problem. Set
28388 @var{limit} to zero to suppress all complaints; set it to a large number
28389 to prevent complaints from being suppressed.
28391 @kindex show complaints
28392 @item show complaints
28393 Displays how many symbol complaints @value{GDBN} is permitted to produce.
28397 @anchor{confirmation requests}
28398 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
28399 lot of stupid questions to confirm certain commands. For example, if
28400 you try to run a program which is already running:
28404 The program being debugged has been started already.
28405 Start it from the beginning? (y or n)
28408 If you are willing to unflinchingly face the consequences of your own
28409 commands, you can disable this ``feature'':
28413 @kindex set confirm
28415 @cindex confirmation
28416 @cindex stupid questions
28417 @item set confirm off
28418 Disables confirmation requests. Note that running @value{GDBN} with
28419 the @option{--batch} option (@pxref{Mode Options, -batch}) also
28420 automatically disables confirmation requests.
28422 @item set confirm on
28423 Enables confirmation requests (the default).
28425 @kindex show confirm
28427 Displays state of confirmation requests.
28431 @cindex command tracing
28432 If you need to debug user-defined commands or sourced files you may find it
28433 useful to enable @dfn{command tracing}. In this mode each command will be
28434 printed as it is executed, prefixed with one or more @samp{+} symbols, the
28435 quantity denoting the call depth of each command.
28438 @kindex set trace-commands
28439 @cindex command scripts, debugging
28440 @item set trace-commands on
28441 Enable command tracing.
28442 @item set trace-commands off
28443 Disable command tracing.
28444 @item show trace-commands
28445 Display the current state of command tracing.
28448 @node Debugging Output
28449 @section Optional Messages about Internal Happenings
28450 @cindex optional debugging messages
28452 @value{GDBN} has commands that enable optional debugging messages from
28453 various @value{GDBN} subsystems; normally these commands are of
28454 interest to @value{GDBN} maintainers, or when reporting a bug. This
28455 section documents those commands.
28458 @kindex set exec-done-display
28459 @item set exec-done-display
28460 Turns on or off the notification of asynchronous commands'
28461 completion. When on, @value{GDBN} will print a message when an
28462 asynchronous command finishes its execution. The default is off.
28463 @kindex show exec-done-display
28464 @item show exec-done-display
28465 Displays the current setting of asynchronous command completion
28469 @cindex ARM AArch64
28470 @item set debug aarch64
28471 Turns on or off display of debugging messages related to ARM AArch64.
28472 The default is off.
28474 @item show debug aarch64
28475 Displays the current state of displaying debugging messages related to
28478 @cindex gdbarch debugging info
28479 @cindex architecture debugging info
28480 @item set debug arch
28481 Turns on or off display of gdbarch debugging info. The default is off
28482 @item show debug arch
28483 Displays the current state of displaying gdbarch debugging info.
28485 @item set debug aix-thread
28486 @cindex AIX threads
28487 Display debugging messages about inner workings of the AIX thread
28489 @item show debug aix-thread
28490 Show the current state of AIX thread debugging info display.
28492 @cindex AMD GPU debugging info
28493 @anchor{set debug amd-dbgapi-lib}
28494 @item set debug amd-dbgapi-lib
28495 @itemx show debug amd-dbgapi-lib
28497 The @code{set debug amd-dbgapi-lib log-level @var{level}} command can be used
28498 to enable diagnostic messages from the @samp{amd-dbgapi} library, where
28499 @var{level} can be:
28504 no logging is enabled
28507 fatal errors are reported
28510 fatal errors and warnings are reported
28513 fatal errors, warnings, and info messages are reported
28516 all messages are reported
28520 The @code{show debug amd-dbgapi-lib log-level} command displays the current
28521 @acronym{amd-dbgapi} library log level.
28523 @anchor{set debug amd-dbgapi}
28524 @item set debug amd-dbgapi
28525 @itemx show debug amd-dbgapi
28527 The @samp{set debug amd-dbgapi} command can be used
28528 to enable diagnostic messages in the @samp{amd-dbgapi} target. The
28529 @samp{show debug amd-dbgapi} command displays the current setting.
28530 @xref{set debug amd-dbgapi}.
28532 @item set debug check-physname
28534 Check the results of the ``physname'' computation. When reading DWARF
28535 debugging information for C@t{++}, @value{GDBN} attempts to compute
28536 each entity's name. @value{GDBN} can do this computation in two
28537 different ways, depending on exactly what information is present.
28538 When enabled, this setting causes @value{GDBN} to compute the names
28539 both ways and display any discrepancies.
28540 @item show debug check-physname
28541 Show the current state of ``physname'' checking.
28543 @item set debug coff-pe-read
28544 @cindex COFF/PE exported symbols
28545 Control display of debugging messages related to reading of COFF/PE
28546 exported symbols. The default is off.
28547 @item show debug coff-pe-read
28548 Displays the current state of displaying debugging messages related to
28549 reading of COFF/PE exported symbols.
28551 @item set debug dwarf-die
28553 Dump DWARF DIEs after they are read in.
28554 The value is the number of nesting levels to print.
28555 A value of zero turns off the display.
28556 @item show debug dwarf-die
28557 Show the current state of DWARF DIE debugging.
28559 @item set debug dwarf-line
28560 @cindex DWARF Line Tables
28561 Turns on or off display of debugging messages related to reading
28562 DWARF line tables. The default is 0 (off).
28563 A value of 1 provides basic information.
28564 A value greater than 1 provides more verbose information.
28565 @item show debug dwarf-line
28566 Show the current state of DWARF line table debugging.
28568 @item set debug dwarf-read
28569 @cindex DWARF Reading
28570 Turns on or off display of debugging messages related to reading
28571 DWARF debug info. The default is 0 (off).
28572 A value of 1 provides basic information.
28573 A value greater than 1 provides more verbose information.
28574 @item show debug dwarf-read
28575 Show the current state of DWARF reader debugging.
28577 @item set debug displaced
28578 @cindex displaced stepping debugging info
28579 Turns on or off display of @value{GDBN} debugging info for the
28580 displaced stepping support. The default is off.
28581 @item show debug displaced
28582 Displays the current state of displaying @value{GDBN} debugging info
28583 related to displaced stepping.
28585 @item set debug event
28586 @cindex event debugging info
28587 Turns on or off display of @value{GDBN} event debugging info. The
28589 @item show debug event
28590 Displays the current state of displaying @value{GDBN} event debugging
28593 @item set debug event-loop
28594 @cindex event-loop debugging
28595 Controls output of debugging info about the event loop. The possible
28596 values are @samp{off}, @samp{all} (shows all debugging info) and
28597 @samp{all-except-ui} (shows all debugging info except those about
28598 UI-related events).
28599 @item show debug event-loop
28600 Shows the current state of displaying debugging info about the event
28603 @item set debug expression
28604 @cindex expression debugging info
28605 Turns on or off display of debugging info about @value{GDBN}
28606 expression parsing. The default is off.
28607 @item show debug expression
28608 Displays the current state of displaying debugging info about
28609 @value{GDBN} expression parsing.
28611 @item set debug fbsd-lwp
28612 @cindex FreeBSD LWP debug messages
28613 Turns on or off debugging messages from the FreeBSD LWP debug support.
28614 @item show debug fbsd-lwp
28615 Show the current state of FreeBSD LWP debugging messages.
28617 @item set debug fbsd-nat
28618 @cindex FreeBSD native target debug messages
28619 Turns on or off debugging messages from the FreeBSD native target.
28620 @item show debug fbsd-nat
28621 Show the current state of FreeBSD native target debugging messages.
28623 @item set debug fortran-array-slicing
28624 @cindex fortran array slicing debugging info
28625 Turns on or off display of @value{GDBN} Fortran array slicing
28626 debugging info. The default is off.
28628 @item show debug fortran-array-slicing
28629 Displays the current state of displaying @value{GDBN} Fortran array
28630 slicing debugging info.
28632 @item set debug frame
28633 @cindex frame debugging info
28634 Turns on or off display of @value{GDBN} frame debugging info. The
28636 @item show debug frame
28637 Displays the current state of displaying @value{GDBN} frame debugging
28640 @item set debug gnu-nat
28641 @cindex @sc{gnu}/Hurd debug messages
28642 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
28643 @item show debug gnu-nat
28644 Show the current state of @sc{gnu}/Hurd debugging messages.
28646 @item set debug infrun
28647 @cindex inferior debugging info
28648 Turns on or off display of @value{GDBN} debugging info for running the inferior.
28649 The default is off. @file{infrun.c} contains GDB's runtime state machine used
28650 for implementing operations such as single-stepping the inferior.
28651 @item show debug infrun
28652 Displays the current state of @value{GDBN} inferior debugging.
28654 @item set debug infcall
28655 @cindex inferior function call debugging info
28656 Turns on or off display of debugging info related to inferior function
28657 calls made by @value{GDBN}.
28658 @item show debug infcall
28659 Displays the current state of @value{GDBN} inferior function call debugging.
28661 @item set debug jit
28662 @cindex just-in-time compilation, debugging messages
28663 Turn on or off debugging messages from JIT debug support.
28664 @item show debug jit
28665 Displays the current state of @value{GDBN} JIT debugging.
28667 @item set debug linux-nat @r{[}on@r{|}off@r{]}
28668 @cindex @sc{gnu}/Linux native target debug messages
28669 @cindex Linux native targets
28670 Turn on or off debugging messages from the Linux native target debug support.
28671 @item show debug linux-nat
28672 Show the current state of Linux native target debugging messages.
28674 @item set debug linux-namespaces
28675 @cindex @sc{gnu}/Linux namespaces debug messages
28676 Turn on or off debugging messages from the Linux namespaces debug support.
28677 @item show debug linux-namespaces
28678 Show the current state of Linux namespaces debugging messages.
28680 @item set debug mach-o
28681 @cindex Mach-O symbols processing
28682 Control display of debugging messages related to Mach-O symbols
28683 processing. The default is off.
28684 @item show debug mach-o
28685 Displays the current state of displaying debugging messages related to
28686 reading of COFF/PE exported symbols.
28688 @item set debug notification
28689 @cindex remote async notification debugging info
28690 Turn on or off debugging messages about remote async notification.
28691 The default is off.
28692 @item show debug notification
28693 Displays the current state of remote async notification debugging messages.
28695 @item set debug observer
28696 @cindex observer debugging info
28697 Turns on or off display of @value{GDBN} observer debugging. This
28698 includes info such as the notification of observable events.
28699 @item show debug observer
28700 Displays the current state of observer debugging.
28702 @item set debug overload
28703 @cindex C@t{++} overload debugging info
28704 Turns on or off display of @value{GDBN} C@t{++} overload debugging
28705 info. This includes info such as ranking of functions, etc. The default
28707 @item show debug overload
28708 Displays the current state of displaying @value{GDBN} C@t{++} overload
28711 @cindex expression parser, debugging info
28712 @cindex debug expression parser
28713 @item set debug parser
28714 Turns on or off the display of expression parser debugging output.
28715 Internally, this sets the @code{yydebug} variable in the expression
28716 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
28717 details. The default is off.
28718 @item show debug parser
28719 Show the current state of expression parser debugging.
28721 @cindex packets, reporting on stdout
28722 @cindex serial connections, debugging
28723 @cindex debug remote protocol
28724 @cindex remote protocol debugging
28725 @cindex display remote packets
28726 @item set debug remote
28727 Turns on or off display of reports on all packets sent back and forth across
28728 the serial line to the remote machine. The info is printed on the
28729 @value{GDBN} standard output stream. The default is off.
28730 @item show debug remote
28731 Displays the state of display of remote packets.
28733 @item set debug remote-packet-max-chars
28734 Sets the maximum number of characters to display for each remote packet when
28735 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
28736 displaying lengthy remote packets and polluting the console.
28738 The default value is @code{512}, which means @value{GDBN} will truncate each
28739 remote packet after 512 bytes.
28741 Setting this option to @code{unlimited} will disable truncation and will output
28742 the full length of the remote packets.
28743 @item show debug remote-packet-max-chars
28744 Displays the number of bytes to output for remote packet debugging.
28746 @item set debug separate-debug-file
28747 Turns on or off display of debug output about separate debug file search.
28748 @item show debug separate-debug-file
28749 Displays the state of separate debug file search debug output.
28751 @item set debug serial
28752 Turns on or off display of @value{GDBN} serial debugging info. The
28754 @item show debug serial
28755 Displays the current state of displaying @value{GDBN} serial debugging
28758 @item set debug solib
28759 Turns on or off display of debugging messages related to shared libraries.
28760 The default is off.
28761 @item show debug solib
28762 Show the current state of solib debugging messages.
28764 @item set debug symbol-lookup
28765 @cindex symbol lookup
28766 Turns on or off display of debugging messages related to symbol lookup.
28767 The default is 0 (off).
28768 A value of 1 provides basic information.
28769 A value greater than 1 provides more verbose information.
28770 @item show debug symbol-lookup
28771 Show the current state of symbol lookup debugging messages.
28773 @item set debug symfile
28774 @cindex symbol file functions
28775 Turns on or off display of debugging messages related to symbol file functions.
28776 The default is off. @xref{Files}.
28777 @item show debug symfile
28778 Show the current state of symbol file debugging messages.
28780 @item set debug symtab-create
28781 @cindex symbol table creation
28782 Turns on or off display of debugging messages related to symbol table creation.
28783 The default is 0 (off).
28784 A value of 1 provides basic information.
28785 A value greater than 1 provides more verbose information.
28786 @item show debug symtab-create
28787 Show the current state of symbol table creation debugging.
28789 @item set debug target
28790 @cindex target debugging info
28791 Turns on or off display of @value{GDBN} target debugging info. This info
28792 includes what is going on at the target level of GDB, as it happens. The
28793 default is 0. Set it to 1 to track events, and to 2 to also track the
28794 value of large memory transfers.
28795 @item show debug target
28796 Displays the current state of displaying @value{GDBN} target debugging
28799 @item set debug timestamp
28800 @cindex timestamping debugging info
28801 Turns on or off display of timestamps with @value{GDBN} debugging info.
28802 When enabled, seconds and microseconds are displayed before each debugging
28804 @item show debug timestamp
28805 Displays the current state of displaying timestamps with @value{GDBN}
28808 @item set debug varobj
28809 @cindex variable object debugging info
28810 Turns on or off display of @value{GDBN} variable object debugging
28811 info. The default is off.
28812 @item show debug varobj
28813 Displays the current state of displaying @value{GDBN} variable object
28816 @item set debug xml
28817 @cindex XML parser debugging
28818 Turn on or off debugging messages for built-in XML parsers.
28819 @item show debug xml
28820 Displays the current state of XML debugging messages.
28822 @item set debug breakpoints
28823 @cindex breakpoint debugging info
28824 Turns on or off display of @value{GDBN} debugging info for breakpoint insertion
28825 and removal. The default is off.
28826 @item show debug breakpoints
28827 Displays the current state of displaying @value{GDBN} debugging info for
28828 breakpoint insertion and removal.
28831 @node Other Misc Settings
28832 @section Other Miscellaneous Settings
28833 @cindex miscellaneous settings
28836 @kindex set interactive-mode
28837 @item set interactive-mode
28838 If @code{on}, forces @value{GDBN} to assume that GDB was started
28839 in a terminal. In practice, this means that @value{GDBN} should wait
28840 for the user to answer queries generated by commands entered at
28841 the command prompt. If @code{off}, forces @value{GDBN} to operate
28842 in the opposite mode, and it uses the default answers to all queries.
28843 If @code{auto} (the default), @value{GDBN} tries to determine whether
28844 its standard input is a terminal, and works in interactive-mode if it
28845 is, non-interactively otherwise.
28847 In the vast majority of cases, the debugger should be able to guess
28848 correctly which mode should be used. But this setting can be useful
28849 in certain specific cases, such as running a MinGW @value{GDBN}
28850 inside a cygwin window.
28852 @kindex show interactive-mode
28853 @item show interactive-mode
28854 Displays whether the debugger is operating in interactive mode or not.
28858 @kindex set suppress-cli-notifications
28859 @item set suppress-cli-notifications
28860 If @code{on}, command-line-interface (CLI) notifications that are
28861 printed by @value{GDBN} are suppressed. If @code{off}, the
28862 notifications are printed as usual. The default value is @code{off}.
28863 CLI notifications occur when you change the selected context or when
28864 the program being debugged stops, as detailed below.
28867 @item User-selected context changes:
28868 When you change the selected context (i.e.@: the current inferior,
28869 thread and/or the frame), @value{GDBN} prints information about the
28870 new context. For example, the default behavior is below:
28874 [Switching to inferior 1 [process 634] (/tmp/test)]
28875 [Switching to thread 1 (process 634)]
28876 #0 main () at test.c:3
28881 When the notifications are suppressed, the new context is not printed:
28884 (gdb) set suppress-cli-notifications on
28889 @item The program being debugged stops:
28890 When the program you are debugging stops (e.g.@: because of hitting a
28891 breakpoint, completing source-stepping, an interrupt, etc.),
28892 @value{GDBN} prints information about the stop event. For example,
28893 below is a breakpoint hit:
28896 (gdb) break test.c:3
28897 Breakpoint 2 at 0x555555555155: file test.c, line 3.
28901 Breakpoint 2, main () at test.c:3
28906 When the notifications are suppressed, the output becomes:
28909 (gdb) break test.c:3
28910 Breakpoint 2 at 0x555555555155: file test.c, line 3.
28911 (gdb) set suppress-cli-notifications on
28917 Suppressing CLI notifications may be useful in scripts to obtain a
28918 reduced output from a list of commands.
28921 @kindex show suppress-cli-notifications
28922 @item show suppress-cli-notifications
28923 Displays whether printing CLI notifications is suppressed or not.
28926 @node Extending GDB
28927 @chapter Extending @value{GDBN}
28928 @cindex extending GDB
28930 @value{GDBN} provides several mechanisms for extension.
28931 @value{GDBN} also provides the ability to automatically load
28932 extensions when it reads a file for debugging. This allows the
28933 user to automatically customize @value{GDBN} for the program
28936 To facilitate the use of extension languages, @value{GDBN} is capable
28937 of evaluating the contents of a file. When doing so, @value{GDBN}
28938 can recognize which extension language is being used by looking at
28939 the filename extension. Files with an unrecognized filename extension
28940 are always treated as a @value{GDBN} Command Files.
28941 @xref{Command Files,, Command files}.
28943 You can control how @value{GDBN} evaluates these files with the following
28947 @kindex set script-extension
28948 @kindex show script-extension
28949 @item set script-extension off
28950 All scripts are always evaluated as @value{GDBN} Command Files.
28952 @item set script-extension soft
28953 The debugger determines the scripting language based on filename
28954 extension. If this scripting language is supported, @value{GDBN}
28955 evaluates the script using that language. Otherwise, it evaluates
28956 the file as a @value{GDBN} Command File.
28958 @item set script-extension strict
28959 The debugger determines the scripting language based on filename
28960 extension, and evaluates the script using that language. If the
28961 language is not supported, then the evaluation fails.
28963 @item show script-extension
28964 Display the current value of the @code{script-extension} option.
28968 @ifset SYSTEM_GDBINIT_DIR
28969 This setting is not used for files in the system-wide gdbinit directory.
28970 Files in that directory must have an extension matching their language,
28971 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
28972 commands. @xref{Startup}.
28976 * Sequences:: Canned Sequences of @value{GDBN} Commands
28977 * Aliases:: Command Aliases
28978 * Python:: Extending @value{GDBN} using Python
28979 * Guile:: Extending @value{GDBN} using Guile
28980 * Auto-loading extensions:: Automatically loading extensions
28981 * Multiple Extension Languages:: Working with multiple extension languages
28985 @section Canned Sequences of Commands
28987 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
28988 Command Lists}), @value{GDBN} provides two ways to store sequences of
28989 commands for execution as a unit: user-defined commands and command
28993 * Define:: How to define your own commands
28994 * Hooks:: Hooks for user-defined commands
28995 * Command Files:: How to write scripts of commands to be stored in a file
28996 * Output:: Commands for controlled output
28997 * Auto-loading sequences:: Controlling auto-loaded command files
29001 @subsection User-defined Commands
29003 @cindex user-defined command
29004 @cindex arguments, to user-defined commands
29005 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
29006 which you assign a new name as a command. This is done with the
29007 @code{define} command. User commands may accept an unlimited number of arguments
29008 separated by whitespace. Arguments are accessed within the user command
29009 via @code{$arg0@dots{}$argN}. A trivial example:
29013 print $arg0 + $arg1 + $arg2
29018 To execute the command use:
29025 This defines the command @code{adder}, which prints the sum of
29026 its three arguments. Note the arguments are text substitutions, so they may
29027 reference variables, use complex expressions, or even perform inferior
29030 @cindex argument count in user-defined commands
29031 @cindex how many arguments (user-defined commands)
29032 In addition, @code{$argc} may be used to find out how many arguments have
29038 print $arg0 + $arg1
29041 print $arg0 + $arg1 + $arg2
29046 Combining with the @code{eval} command (@pxref{eval}) makes it easier
29047 to process a variable number of arguments:
29054 eval "set $sum = $sum + $arg%d", $i
29064 @item define @var{commandname}
29065 Define a command named @var{commandname}. If there is already a command
29066 by that name, you are asked to confirm that you want to redefine it.
29067 The argument @var{commandname} may be a bare command name consisting of letters,
29068 numbers, dashes, dots, and underscores. It may also start with any
29069 predefined or user-defined prefix command.
29070 For example, @samp{define target my-target} creates
29071 a user-defined @samp{target my-target} command.
29073 The definition of the command is made up of other @value{GDBN} command lines,
29074 which are given following the @code{define} command. The end of these
29075 commands is marked by a line containing @code{end}.
29078 @kindex end@r{ (user-defined commands)}
29079 @item document @var{commandname}
29080 Document the user-defined command @var{commandname}, so that it can be
29081 accessed by @code{help}. The command @var{commandname} must already be
29082 defined. This command reads lines of documentation just as @code{define}
29083 reads the lines of the command definition, ending with @code{end}.
29084 After the @code{document} command is finished, @code{help} on command
29085 @var{commandname} displays the documentation you have written.
29087 You may use the @code{document} command again to change the
29088 documentation of a command. Redefining the command with @code{define}
29089 does not change the documentation.
29091 It is also possible to document user-defined aliases. The alias documentation
29092 will then be used by the @code{help} and @code{apropos} commands
29093 instead of the documentation of the aliased command.
29094 Documenting a user-defined alias is particularly useful when defining
29095 an alias as a set of nested @code{with} commands
29096 (@pxref{Command aliases default args}).
29098 @kindex define-prefix
29099 @item define-prefix @var{commandname}
29100 Define or mark the command @var{commandname} as a user-defined prefix
29101 command. Once marked, @var{commandname} can be used as prefix command
29102 by the @code{define} command.
29103 Note that @code{define-prefix} can be used with a not yet defined
29104 @var{commandname}. In such a case, @var{commandname} is defined as
29105 an empty user-defined command.
29106 In case you redefine a command that was marked as a user-defined
29107 prefix command, the subcommands of the redefined command are kept
29108 (and @value{GDBN} indicates so to the user).
29112 (@value{GDBP}) define-prefix abc
29113 (@value{GDBP}) define-prefix abc def
29114 (@value{GDBP}) define abc def
29115 Type commands for definition of "abc def".
29116 End with a line saying just "end".
29117 >echo command initial def\n
29119 (@value{GDBP}) define abc def ghi
29120 Type commands for definition of "abc def ghi".
29121 End with a line saying just "end".
29122 >echo command ghi\n
29124 (@value{GDBP}) define abc def
29125 Keeping subcommands of prefix command "def".
29126 Redefine command "def"? (y or n) y
29127 Type commands for definition of "abc def".
29128 End with a line saying just "end".
29129 >echo command def\n
29131 (@value{GDBP}) abc def ghi
29133 (@value{GDBP}) abc def
29138 @kindex dont-repeat
29139 @cindex don't repeat command
29141 Used inside a user-defined command, this tells @value{GDBN} that this
29142 command should not be repeated when the user hits @key{RET}
29143 (@pxref{Command Syntax, repeat last command}).
29145 @kindex help user-defined
29146 @item help user-defined
29147 List all user-defined commands and all python commands defined in class
29148 COMMAND_USER. The first line of the documentation or docstring is
29153 @itemx show user @var{commandname}
29154 Display the @value{GDBN} commands used to define @var{commandname} (but
29155 not its documentation). If no @var{commandname} is given, display the
29156 definitions for all user-defined commands.
29157 This does not work for user-defined python commands.
29159 @cindex infinite recursion in user-defined commands
29160 @kindex show max-user-call-depth
29161 @kindex set max-user-call-depth
29162 @item show max-user-call-depth
29163 @itemx set max-user-call-depth
29164 The value of @code{max-user-call-depth} controls how many recursion
29165 levels are allowed in user-defined commands before @value{GDBN} suspects an
29166 infinite recursion and aborts the command.
29167 This does not apply to user-defined python commands.
29170 In addition to the above commands, user-defined commands frequently
29171 use control flow commands, described in @ref{Command Files}.
29173 When user-defined commands are executed, the
29174 commands of the definition are not printed. An error in any command
29175 stops execution of the user-defined command.
29177 If used interactively, commands that would ask for confirmation proceed
29178 without asking when used inside a user-defined command. Many @value{GDBN}
29179 commands that normally print messages to say what they are doing omit the
29180 messages when used in a user-defined command.
29183 @subsection User-defined Command Hooks
29184 @cindex command hooks
29185 @cindex hooks, for commands
29186 @cindex hooks, pre-command
29189 You may define @dfn{hooks}, which are a special kind of user-defined
29190 command. Whenever you run the command @samp{foo}, if the user-defined
29191 command @samp{hook-foo} exists, it is executed (with no arguments)
29192 before that command.
29194 @cindex hooks, post-command
29196 A hook may also be defined which is run after the command you executed.
29197 Whenever you run the command @samp{foo}, if the user-defined command
29198 @samp{hookpost-foo} exists, it is executed (with no arguments) after
29199 that command. Post-execution hooks may exist simultaneously with
29200 pre-execution hooks, for the same command.
29202 It is valid for a hook to call the command which it hooks. If this
29203 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
29205 @c It would be nice if hookpost could be passed a parameter indicating
29206 @c if the command it hooks executed properly or not. FIXME!
29208 @kindex stop@r{, a pseudo-command}
29209 In addition, a pseudo-command, @samp{stop} exists. Defining
29210 (@samp{hook-stop}) makes the associated commands execute every time
29211 execution stops in your program: before breakpoint commands are run,
29212 displays are printed, or the stack frame is printed.
29214 For example, to ignore @code{SIGALRM} signals while
29215 single-stepping, but treat them normally during normal execution,
29220 handle SIGALRM nopass
29224 handle SIGALRM pass
29227 define hook-continue
29228 handle SIGALRM pass
29232 As a further example, to hook at the beginning and end of the @code{echo}
29233 command, and to add extra text to the beginning and end of the message,
29241 define hookpost-echo
29245 (@value{GDBP}) echo Hello World
29246 <<<---Hello World--->>>
29251 You can define a hook for any single-word command in @value{GDBN}, but
29252 not for command aliases; you should define a hook for the basic command
29253 name, e.g.@: @code{backtrace} rather than @code{bt}.
29254 @c FIXME! So how does Joe User discover whether a command is an alias
29256 You can hook a multi-word command by adding @code{hook-} or
29257 @code{hookpost-} to the last word of the command, e.g.@:
29258 @samp{define target hook-remote} to add a hook to @samp{target remote}.
29260 If an error occurs during the execution of your hook, execution of
29261 @value{GDBN} commands stops and @value{GDBN} issues a prompt
29262 (before the command that you actually typed had a chance to run).
29264 If you try to define a hook which does not match any known command, you
29265 get a warning from the @code{define} command.
29267 @node Command Files
29268 @subsection Command Files
29270 @cindex command files
29271 @cindex scripting commands
29272 A command file for @value{GDBN} is a text file made of lines that are
29273 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
29274 also be included. An empty line in a command file does nothing; it
29275 does not mean to repeat the last command, as it would from the
29278 You can request the execution of a command file with the @code{source}
29279 command. Note that the @code{source} command is also used to evaluate
29280 scripts that are not Command Files. The exact behavior can be configured
29281 using the @code{script-extension} setting.
29282 @xref{Extending GDB,, Extending GDB}.
29286 @cindex execute commands from a file
29287 @item source [-s] [-v] @var{filename}
29288 Execute the command file @var{filename}.
29291 The lines in a command file are generally executed sequentially,
29292 unless the order of execution is changed by one of the
29293 @emph{flow-control commands} described below. The commands are not
29294 printed as they are executed. An error in any command terminates
29295 execution of the command file and control is returned to the console.
29297 @value{GDBN} first searches for @var{filename} in the current directory.
29298 If the file is not found there, and @var{filename} does not specify a
29299 directory, then @value{GDBN} also looks for the file on the source search path
29300 (specified with the @samp{directory} command);
29301 except that @file{$cdir} is not searched because the compilation directory
29302 is not relevant to scripts.
29304 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
29305 on the search path even if @var{filename} specifies a directory.
29306 The search is done by appending @var{filename} to each element of the
29307 search path. So, for example, if @var{filename} is @file{mylib/myscript}
29308 and the search path contains @file{/home/user} then @value{GDBN} will
29309 look for the script @file{/home/user/mylib/myscript}.
29310 The search is also done if @var{filename} is an absolute path.
29311 For example, if @var{filename} is @file{/tmp/myscript} and
29312 the search path contains @file{/home/user} then @value{GDBN} will
29313 look for the script @file{/home/user/tmp/myscript}.
29314 For DOS-like systems, if @var{filename} contains a drive specification,
29315 it is stripped before concatenation. For example, if @var{filename} is
29316 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
29317 will look for the script @file{c:/tmp/myscript}.
29319 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
29320 each command as it is executed. The option must be given before
29321 @var{filename}, and is interpreted as part of the filename anywhere else.
29323 Commands that would ask for confirmation if used interactively proceed
29324 without asking when used in a command file. Many @value{GDBN} commands that
29325 normally print messages to say what they are doing omit the messages
29326 when called from command files.
29328 @value{GDBN} also accepts command input from standard input. In this
29329 mode, normal output goes to standard output and error output goes to
29330 standard error. Errors in a command file supplied on standard input do
29331 not terminate execution of the command file---execution continues with
29335 gdb < cmds > log 2>&1
29338 (The syntax above will vary depending on the shell used.) This example
29339 will execute commands from the file @file{cmds}. All output and errors
29340 would be directed to @file{log}.
29342 Since commands stored on command files tend to be more general than
29343 commands typed interactively, they frequently need to deal with
29344 complicated situations, such as different or unexpected values of
29345 variables and symbols, changes in how the program being debugged is
29346 built, etc. @value{GDBN} provides a set of flow-control commands to
29347 deal with these complexities. Using these commands, you can write
29348 complex scripts that loop over data structures, execute commands
29349 conditionally, etc.
29356 This command allows to include in your script conditionally executed
29357 commands. The @code{if} command takes a single argument, which is an
29358 expression to evaluate. It is followed by a series of commands that
29359 are executed only if the expression is true (its value is nonzero).
29360 There can then optionally be an @code{else} line, followed by a series
29361 of commands that are only executed if the expression was false. The
29362 end of the list is marked by a line containing @code{end}.
29366 This command allows to write loops. Its syntax is similar to
29367 @code{if}: the command takes a single argument, which is an expression
29368 to evaluate, and must be followed by the commands to execute, one per
29369 line, terminated by an @code{end}. These commands are called the
29370 @dfn{body} of the loop. The commands in the body of @code{while} are
29371 executed repeatedly as long as the expression evaluates to true.
29375 This command exits the @code{while} loop in whose body it is included.
29376 Execution of the script continues after that @code{while}s @code{end}
29379 @kindex loop_continue
29380 @item loop_continue
29381 This command skips the execution of the rest of the body of commands
29382 in the @code{while} loop in whose body it is included. Execution
29383 branches to the beginning of the @code{while} loop, where it evaluates
29384 the controlling expression.
29386 @kindex end@r{ (if/else/while commands)}
29388 Terminate the block of commands that are the body of @code{if},
29389 @code{else}, or @code{while} flow-control commands.
29394 @subsection Commands for Controlled Output
29396 During the execution of a command file or a user-defined command, normal
29397 @value{GDBN} output is suppressed; the only output that appears is what is
29398 explicitly printed by the commands in the definition. This section
29399 describes three commands useful for generating exactly the output you
29404 @item echo @var{text}
29405 @c I do not consider backslash-space a standard C escape sequence
29406 @c because it is not in ANSI.
29407 Print @var{text}. Nonprinting characters can be included in
29408 @var{text} using C escape sequences, such as @samp{\n} to print a
29409 newline. @strong{No newline is printed unless you specify one.}
29410 In addition to the standard C escape sequences, a backslash followed
29411 by a space stands for a space. This is useful for displaying a
29412 string with spaces at the beginning or the end, since leading and
29413 trailing spaces are otherwise trimmed from all arguments.
29414 To print @samp{@w{ }and foo =@w{ }}, use the command
29415 @samp{echo \@w{ }and foo = \@w{ }}.
29417 A backslash at the end of @var{text} can be used, as in C, to continue
29418 the command onto subsequent lines. For example,
29421 echo This is some text\n\
29422 which is continued\n\
29423 onto several lines.\n
29426 produces the same output as
29429 echo This is some text\n
29430 echo which is continued\n
29431 echo onto several lines.\n
29435 @item output @var{expression}
29436 Print the value of @var{expression} and nothing but that value: no
29437 newlines, no @samp{$@var{nn} = }. The value is not entered in the
29438 value history either. @xref{Expressions, ,Expressions}, for more information
29441 @item output/@var{fmt} @var{expression}
29442 Print the value of @var{expression} in format @var{fmt}. You can use
29443 the same formats as for @code{print}. @xref{Output Formats,,Output
29444 Formats}, for more information.
29447 @item printf @var{template}, @var{expressions}@dots{}
29448 Print the values of one or more @var{expressions} under the control of
29449 the string @var{template}. To print several values, make
29450 @var{expressions} be a comma-separated list of individual expressions,
29451 which may be either numbers or pointers. Their values are printed as
29452 specified by @var{template}, exactly as a C program would do by
29453 executing the code below:
29456 printf (@var{template}, @var{expressions}@dots{});
29459 As in @code{C} @code{printf}, ordinary characters in @var{template}
29460 are printed verbatim, while @dfn{conversion specification} introduced
29461 by the @samp{%} character cause subsequent @var{expressions} to be
29462 evaluated, their values converted and formatted according to type and
29463 style information encoded in the conversion specifications, and then
29466 For example, you can print two values in hex like this:
29469 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
29472 @code{printf} supports all the standard @code{C} conversion
29473 specifications, including the flags and modifiers between the @samp{%}
29474 character and the conversion letter, with the following exceptions:
29478 The argument-ordering modifiers, such as @samp{2$}, are not supported.
29481 The modifier @samp{*} is not supported for specifying precision or
29485 The @samp{'} flag (for separation of digits into groups according to
29486 @code{LC_NUMERIC'}) is not supported.
29489 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
29493 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
29496 The conversion letters @samp{a} and @samp{A} are not supported.
29500 Note that the @samp{ll} type modifier is supported only if the
29501 underlying @code{C} implementation used to build @value{GDBN} supports
29502 the @code{long long int} type, and the @samp{L} type modifier is
29503 supported only if @code{long double} type is available.
29505 As in @code{C}, @code{printf} supports simple backslash-escape
29506 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
29507 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
29508 single character. Octal and hexadecimal escape sequences are not
29511 Additionally, @code{printf} supports conversion specifications for DFP
29512 (@dfn{Decimal Floating Point}) types using the following length modifiers
29513 together with a floating point specifier.
29518 @samp{H} for printing @code{Decimal32} types.
29521 @samp{D} for printing @code{Decimal64} types.
29524 @samp{DD} for printing @code{Decimal128} types.
29527 If the underlying @code{C} implementation used to build @value{GDBN} has
29528 support for the three length modifiers for DFP types, other modifiers
29529 such as width and precision will also be available for @value{GDBN} to use.
29531 In case there is no such @code{C} support, no additional modifiers will be
29532 available and the value will be printed in the standard way.
29534 Here's an example of printing DFP types using the above conversion letters:
29536 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
29539 @anchor{%V Format Specifier}
29540 Additionally, @code{printf} supports a special @samp{%V} output format.
29541 This format prints the string representation of an expression just as
29542 @value{GDBN} would produce with the standard @kbd{print} command
29543 (@pxref{Data, ,Examining Data}):
29546 (@value{GDBP}) print array
29547 $1 = @{0, 1, 2, 3, 4, 5@}
29548 (@value{GDBP}) printf "Array is: %V\n", array
29549 Array is: @{0, 1, 2, 3, 4, 5@}
29552 It is possible to include print options with the @samp{%V} format by
29553 placing them in @samp{[...]} immediately after the @samp{%V}, like
29557 (@value{GDBP}) printf "Array is: %V[-array-indexes on]\n", array
29558 Array is: @{[0] = 0, [1] = 1, [2] = 2, [3] = 3, [4] = 4, [5] = 5@}
29561 If you need to print a literal @samp{[} directly after a @samp{%V}, then
29562 just include an empty print options list:
29565 (@value{GDBP}) printf "Array is: %V[][Hello]\n", array
29566 Array is: @{0, 1, 2, 3, 4, 5@}[Hello]
29571 @item eval @var{template}, @var{expressions}@dots{}
29572 Convert the values of one or more @var{expressions} under the control of
29573 the string @var{template} to a command line, and call it.
29577 @node Auto-loading sequences
29578 @subsection Controlling auto-loading native @value{GDBN} scripts
29579 @cindex native script auto-loading
29581 When a new object file is read (for example, due to the @code{file}
29582 command, or because the inferior has loaded a shared library),
29583 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
29584 @xref{Auto-loading extensions}.
29586 Auto-loading can be enabled or disabled,
29587 and the list of auto-loaded scripts can be printed.
29590 @anchor{set auto-load gdb-scripts}
29591 @kindex set auto-load gdb-scripts
29592 @item set auto-load gdb-scripts [on|off]
29593 Enable or disable the auto-loading of canned sequences of commands scripts.
29595 @anchor{show auto-load gdb-scripts}
29596 @kindex show auto-load gdb-scripts
29597 @item show auto-load gdb-scripts
29598 Show whether auto-loading of canned sequences of commands scripts is enabled or
29601 @anchor{info auto-load gdb-scripts}
29602 @kindex info auto-load gdb-scripts
29603 @cindex print list of auto-loaded canned sequences of commands scripts
29604 @item info auto-load gdb-scripts [@var{regexp}]
29605 Print the list of all canned sequences of commands scripts that @value{GDBN}
29609 If @var{regexp} is supplied only canned sequences of commands scripts with
29610 matching names are printed.
29613 @section Command Aliases
29614 @cindex aliases for commands
29616 Aliases allow you to define alternate spellings for existing commands.
29617 For example, if a new @value{GDBN} command defined in Python
29618 (@pxref{Python}) has a long name, it is handy to have an abbreviated
29619 version of it that involves less typing.
29621 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
29622 of the @samp{step} command even though it is otherwise an ambiguous
29623 abbreviation of other commands like @samp{set} and @samp{show}.
29625 Aliases are also used to provide shortened or more common versions
29626 of multi-word commands. For example, @value{GDBN} provides the
29627 @samp{tty} alias of the @samp{set inferior-tty} command.
29629 You can define a new alias with the @samp{alias} command.
29634 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
29638 @var{alias} specifies the name of the new alias. Each word of
29639 @var{alias} must consist of letters, numbers, dashes and underscores.
29641 @var{command} specifies the name of an existing command
29642 that is being aliased.
29644 @var{command} can also be the name of an existing alias. In this
29645 case, @var{command} cannot be an alias that has default arguments.
29647 The @samp{-a} option specifies that the new alias is an abbreviation
29648 of the command. Abbreviations are not used in command completion.
29650 The @samp{--} option specifies the end of options,
29651 and is useful when @var{alias} begins with a dash.
29653 You can specify @var{default-args} for your alias. These
29654 @var{default-args} will be automatically added before the alias
29655 arguments typed explicitly on the command line.
29657 For example, the below defines an alias @code{btfullall} that shows all local
29658 variables and all frame arguments:
29660 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
29663 For more information about @var{default-args}, see @ref{Command
29664 aliases default args, ,Default Arguments}.
29666 Here is a simple example showing how to make an abbreviation of a
29667 command so that there is less to type. Suppose you were tired of
29668 typing @samp{disas}, the current shortest unambiguous abbreviation of
29669 the @samp{disassemble} command and you wanted an even shorter version
29670 named @samp{di}. The following will accomplish this.
29673 (@value{GDBP}) alias -a di = disas
29676 Note that aliases are different from user-defined commands. With a
29677 user-defined command, you also need to write documentation for it with
29678 the @samp{document} command. An alias automatically picks up the
29679 documentation of the existing command.
29681 Here is an example where we make @samp{elms} an abbreviation of
29682 @samp{elements} in the @samp{set print elements} command.
29683 This is to show that you can make an abbreviation of any part
29687 (@value{GDBP}) alias -a set print elms = set print elements
29688 (@value{GDBP}) alias -a show print elms = show print elements
29689 (@value{GDBP}) set p elms 200
29690 (@value{GDBP}) show p elms
29691 Limit on string chars or array elements to print is 200.
29694 Note that if you are defining an alias of a @samp{set} command,
29695 and you want to have an alias for the corresponding @samp{show}
29696 command, then you need to define the latter separately.
29698 Unambiguously abbreviated commands are allowed in @var{command} and
29699 @var{alias}, just as they are normally.
29702 (@value{GDBP}) alias -a set pr elms = set p ele
29705 Finally, here is an example showing the creation of a one word
29706 alias for a more complex command.
29707 This creates alias @samp{spe} of the command @samp{set print elements}.
29710 (@value{GDBP}) alias spe = set print elements
29711 (@value{GDBP}) spe 20
29715 * Command aliases default args:: Default arguments for aliases
29718 @node Command aliases default args
29719 @subsection Default Arguments
29720 @cindex aliases for commands, default arguments
29722 You can tell @value{GDBN} to always prepend some default arguments to
29723 the list of arguments provided explicitly by the user when using a
29724 user-defined alias.
29726 If you repeatedly use the same arguments or options for a command, you
29727 can define an alias for this command and tell @value{GDBN} to
29728 automatically prepend these arguments or options to the list of
29729 arguments you type explicitly when using the alias@footnote{@value{GDBN}
29730 could easily accept default arguments for pre-defined commands and aliases,
29731 but it was deemed this would be confusing, and so is not allowed.}.
29733 For example, if you often use the command @code{thread apply all}
29734 specifying to work on the threads in ascending order and to continue in case it
29735 encounters an error, you can tell @value{GDBN} to automatically preprend
29736 the @code{-ascending} and @code{-c} options by using:
29739 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
29742 Once you have defined this alias with its default args, any time you type
29743 the @code{thread apply asc-all} followed by @code{some arguments},
29744 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
29746 To have even less to type, you can also define a one word alias:
29748 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
29751 As usual, unambiguous abbreviations can be used for @var{alias}
29752 and @var{default-args}.
29754 The different aliases of a command do not share their default args.
29755 For example, you define a new alias @code{bt_ALL} showing all possible
29756 information and another alias @code{bt_SMALL} showing very limited information
29759 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
29760 -past-main -past-entry -full
29761 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
29762 -past-main off -past-entry off
29765 (For more on using the @code{alias} command, see @ref{Aliases}.)
29767 Default args are not limited to the arguments and options of @var{command},
29768 but can specify nested commands if @var{command} accepts such a nested command
29770 For example, the below defines @code{faalocalsoftype} that lists the
29771 frames having locals of a certain type, together with the matching
29774 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
29775 (@value{GDBP}) faalocalsoftype int
29776 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
29781 This is also very useful to define an alias for a set of nested @code{with}
29782 commands to have a particular combination of temporary settings. For example,
29783 the below defines the alias @code{pp10} that pretty prints an expression
29784 argument, with a maximum of 10 elements if the expression is a string or
29787 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
29789 This defines the alias @code{pp10} as being a sequence of 3 commands.
29790 The first part @code{with print pretty --} temporarily activates the setting
29791 @code{set print pretty}, then launches the command that follows the separator
29793 The command following the first part is also a @code{with} command that
29794 temporarily changes the setting @code{set print elements} to 10, then
29795 launches the command that follows the second separator @code{--}.
29796 The third part @code{print} is the command the @code{pp10} alias will launch,
29797 using the temporary values of the settings and the arguments explicitly given
29799 For more information about the @code{with} command usage,
29800 see @ref{Command Settings}.
29802 By default, asking the help for an alias shows the documentation of
29803 the aliased command. When the alias is a set of nested commands, @code{help}
29804 of an alias shows the documentation of the first command. This help
29805 is not particularly useful for an alias such as @code{pp10}.
29806 For such an alias, it is useful to give a specific documentation
29807 using the @code{document} command (@pxref{Define, document}).
29810 @c Python docs live in a separate file.
29811 @include python.texi
29813 @c Guile docs live in a separate file.
29814 @include guile.texi
29816 @node Auto-loading extensions
29817 @section Auto-loading extensions
29818 @cindex auto-loading extensions
29820 @value{GDBN} provides two mechanisms for automatically loading
29821 extensions when a new object file is read (for example, due to the
29822 @code{file} command, or because the inferior has loaded a shared
29823 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
29824 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
29825 @code{.debug_gdb_scripts} section of modern file formats like ELF
29826 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
29827 section}). For a discussion of the differences between these two
29828 approaches see @ref{Which flavor to choose?}.
29830 The auto-loading feature is useful for supplying application-specific
29831 debugging commands and features.
29833 Auto-loading can be enabled or disabled,
29834 and the list of auto-loaded scripts can be printed.
29835 See the @samp{auto-loading} section of each extension language
29836 for more information.
29837 For @value{GDBN} command files see @ref{Auto-loading sequences}.
29838 For Python files see @ref{Python Auto-loading}.
29840 Note that loading of this script file also requires accordingly configured
29841 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29844 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
29845 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
29846 * Which flavor to choose?:: Choosing between these approaches
29849 @node objfile-gdbdotext file
29850 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
29851 @cindex @file{@var{objfile}-gdb.gdb}
29852 @cindex @file{@var{objfile}-gdb.py}
29853 @cindex @file{@var{objfile}-gdb.scm}
29855 When a new object file is read, @value{GDBN} looks for a file named
29856 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
29857 where @var{objfile} is the object file's name and
29858 where @var{ext} is the file extension for the extension language:
29861 @item @file{@var{objfile}-gdb.gdb}
29862 GDB's own command language
29863 @item @file{@var{objfile}-gdb.py}
29865 @item @file{@var{objfile}-gdb.scm}
29869 @var{script-name} is formed by ensuring that the file name of @var{objfile}
29870 is absolute, following all symlinks, and resolving @code{.} and @code{..}
29871 components, and appending the @file{-gdb.@var{ext}} suffix.
29872 If this file exists and is readable, @value{GDBN} will evaluate it as a
29873 script in the specified extension language.
29875 If this file does not exist, then @value{GDBN} will look for
29876 @var{script-name} file in all of the directories as specified below.
29877 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
29878 directories is converted to a one-letter subdirectory, i.e.@:
29879 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
29880 filesystems disallow colons in file names.)
29882 Note that loading of these files requires an accordingly configured
29883 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29885 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
29886 scripts normally according to its @file{.exe} filename. But if no scripts are
29887 found @value{GDBN} also tries script filenames matching the object file without
29888 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
29889 is attempted on any platform. This makes the script filenames compatible
29890 between Unix and MS-Windows hosts.
29893 @anchor{set auto-load scripts-directory}
29894 @kindex set auto-load scripts-directory
29895 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
29896 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
29897 may be delimited by the host platform path separator in use
29898 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
29900 Each entry here needs to be covered also by the security setting
29901 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
29903 @anchor{with-auto-load-dir}
29904 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
29905 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
29906 configuration option @option{--with-auto-load-dir}.
29908 Any reference to @file{$debugdir} will get replaced by
29909 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
29910 reference to @file{$datadir} will get replaced by @var{data-directory} which is
29911 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
29912 @file{$datadir} must be placed as a directory component --- either alone or
29913 delimited by @file{/} or @file{\} directory separators, depending on the host
29916 The list of directories uses path separator (@samp{:} on GNU and Unix
29917 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
29918 to the @env{PATH} environment variable.
29920 @anchor{show auto-load scripts-directory}
29921 @kindex show auto-load scripts-directory
29922 @item show auto-load scripts-directory
29923 Show @value{GDBN} auto-loaded scripts location.
29925 @anchor{add-auto-load-scripts-directory}
29926 @kindex add-auto-load-scripts-directory
29927 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
29928 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
29929 Multiple entries may be delimited by the host platform path separator in use.
29932 @value{GDBN} does not track which files it has already auto-loaded this way.
29933 @value{GDBN} will load the associated script every time the corresponding
29934 @var{objfile} is opened.
29935 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
29936 is evaluated more than once.
29938 @node dotdebug_gdb_scripts section
29939 @subsection The @code{.debug_gdb_scripts} section
29940 @cindex @code{.debug_gdb_scripts} section
29942 For systems using file formats like ELF and COFF,
29943 when @value{GDBN} loads a new object file
29944 it will look for a special section named @code{.debug_gdb_scripts}.
29945 If this section exists, its contents is a list of null-terminated entries
29946 specifying scripts to load. Each entry begins with a non-null prefix byte that
29947 specifies the kind of entry, typically the extension language and whether the
29948 script is in a file or inlined in @code{.debug_gdb_scripts}.
29950 The following entries are supported:
29953 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
29954 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
29955 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
29956 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
29959 @subsubsection Script File Entries
29961 If the entry specifies a file, @value{GDBN} will look for the file first
29962 in the current directory and then along the source search path
29963 (@pxref{Source Path, ,Specifying Source Directories}),
29964 except that @file{$cdir} is not searched, since the compilation
29965 directory is not relevant to scripts.
29967 File entries can be placed in section @code{.debug_gdb_scripts} with,
29968 for example, this GCC macro for Python scripts.
29971 /* Note: The "MS" section flags are to remove duplicates. */
29972 #define DEFINE_GDB_PY_SCRIPT(script_name) \
29974 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
29975 .byte 1 /* Python */\n\
29976 .asciz \"" script_name "\"\n\
29982 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
29983 Then one can reference the macro in a header or source file like this:
29986 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
29989 The script name may include directories if desired.
29991 Note that loading of this script file also requires accordingly configured
29992 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29994 If the macro invocation is put in a header, any application or library
29995 using this header will get a reference to the specified script,
29996 and with the use of @code{"MS"} attributes on the section, the linker
29997 will remove duplicates.
29999 @subsubsection Script Text Entries
30001 Script text entries allow to put the executable script in the entry
30002 itself instead of loading it from a file.
30003 The first line of the entry, everything after the prefix byte and up to
30004 the first newline (@code{0xa}) character, is the script name, and must not
30005 contain any kind of space character, e.g., spaces or tabs.
30006 The rest of the entry, up to the trailing null byte, is the script to
30007 execute in the specified language. The name needs to be unique among
30008 all script names, as @value{GDBN} executes each script only once based
30011 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
30015 #include "symcat.h"
30016 #include "gdb/section-scripts.h"
30018 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
30019 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
30020 ".ascii \"gdb.inlined-script\\n\"\n"
30021 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
30022 ".ascii \" def __init__ (self):\\n\"\n"
30023 ".ascii \" super (test_cmd, self).__init__ ("
30024 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
30025 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
30026 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
30027 ".ascii \"test_cmd ()\\n\"\n"
30033 Loading of inlined scripts requires a properly configured
30034 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
30035 The path to specify in @code{auto-load safe-path} is the path of the file
30036 containing the @code{.debug_gdb_scripts} section.
30038 @node Which flavor to choose?
30039 @subsection Which flavor to choose?
30041 Given the multiple ways of auto-loading extensions, it might not always
30042 be clear which one to choose. This section provides some guidance.
30045 Benefits of the @file{-gdb.@var{ext}} way:
30049 Can be used with file formats that don't support multiple sections.
30052 Ease of finding scripts for public libraries.
30054 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
30055 in the source search path.
30056 For publicly installed libraries, e.g., @file{libstdc++}, there typically
30057 isn't a source directory in which to find the script.
30060 Doesn't require source code additions.
30064 Benefits of the @code{.debug_gdb_scripts} way:
30068 Works with static linking.
30070 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
30071 trigger their loading. When an application is statically linked the only
30072 objfile available is the executable, and it is cumbersome to attach all the
30073 scripts from all the input libraries to the executable's
30074 @file{-gdb.@var{ext}} script.
30077 Works with classes that are entirely inlined.
30079 Some classes can be entirely inlined, and thus there may not be an associated
30080 shared library to attach a @file{-gdb.@var{ext}} script to.
30083 Scripts needn't be copied out of the source tree.
30085 In some circumstances, apps can be built out of large collections of internal
30086 libraries, and the build infrastructure necessary to install the
30087 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
30088 cumbersome. It may be easier to specify the scripts in the
30089 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
30090 top of the source tree to the source search path.
30093 @node Multiple Extension Languages
30094 @section Multiple Extension Languages
30096 The Guile and Python extension languages do not share any state,
30097 and generally do not interfere with each other.
30098 There are some things to be aware of, however.
30100 @subsection Python comes first
30102 Python was @value{GDBN}'s first extension language, and to avoid breaking
30103 existing behaviour Python comes first. This is generally solved by the
30104 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
30105 extension languages, and when it makes a call to an extension language,
30106 (say to pretty-print a value), it tries each in turn until an extension
30107 language indicates it has performed the request (e.g., has returned the
30108 pretty-printed form of a value).
30109 This extends to errors while performing such requests: If an error happens
30110 while, for example, trying to pretty-print an object then the error is
30111 reported and any following extension languages are not tried.
30114 @chapter Command Interpreters
30115 @cindex command interpreters
30117 @value{GDBN} supports multiple command interpreters, and some command
30118 infrastructure to allow users or user interface writers to switch
30119 between interpreters or run commands in other interpreters.
30121 @value{GDBN} currently supports two command interpreters, the console
30122 interpreter (sometimes called the command-line interpreter or @sc{cli})
30123 and the machine interface interpreter (or @sc{gdb/mi}). This manual
30124 describes both of these interfaces in great detail.
30126 By default, @value{GDBN} will start with the console interpreter.
30127 However, the user may choose to start @value{GDBN} with another
30128 interpreter by specifying the @option{-i} or @option{--interpreter}
30129 startup options. Defined interpreters include:
30133 @cindex console interpreter
30134 The traditional console or command-line interpreter. This is the most often
30135 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
30136 @value{GDBN} will use this interpreter.
30140 @cindex Debugger Adapter Protocol
30141 When @value{GDBN} has been built with Python support, it also supports
30142 the Debugger Adapter Protocol. This protocol can be used by a
30143 debugger GUI or an IDE to communicate with @value{GDBN}. This
30144 protocol is documented at
30145 @url{https://microsoft.github.io/debug-adapter-protocol/}.
30146 @xref{Debugger Adapter Protocol}, for information about @value{GDBN}
30147 extensions to the protocol.
30150 @cindex mi interpreter
30151 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
30152 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
30153 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
30157 @cindex mi3 interpreter
30158 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
30161 @cindex mi2 interpreter
30162 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
30166 @cindex invoke another interpreter
30168 @kindex interpreter-exec
30169 You may execute commands in any interpreter from the current
30170 interpreter using the appropriate command. If you are running the
30171 console interpreter, simply use the @code{interpreter-exec} command:
30174 interpreter-exec mi "-data-list-register-names"
30177 @sc{gdb/mi} has a similar command, although it is only available in versions of
30178 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
30180 Note that @code{interpreter-exec} only changes the interpreter for the
30181 duration of the specified command. It does not change the interpreter
30184 @cindex start a new independent interpreter
30186 Although you may only choose a single interpreter at startup, it is
30187 possible to run an independent interpreter on a specified input/output
30188 device (usually a tty).
30190 For example, consider a debugger GUI or IDE that wants to provide a
30191 @value{GDBN} console view. It may do so by embedding a terminal
30192 emulator widget in its GUI, starting @value{GDBN} in the traditional
30193 command-line mode with stdin/stdout/stderr redirected to that
30194 terminal, and then creating an MI interpreter running on a specified
30195 input/output device. The console interpreter created by @value{GDBN}
30196 at startup handles commands the user types in the terminal widget,
30197 while the GUI controls and synchronizes state with @value{GDBN} using
30198 the separate MI interpreter.
30200 To start a new secondary @dfn{user interface} running MI, use the
30201 @code{new-ui} command:
30204 @cindex new user interface
30206 new-ui @var{interpreter} @var{tty}
30209 The @var{interpreter} parameter specifies the interpreter to run.
30210 This accepts the same values as the @code{interpreter-exec} command.
30211 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
30212 @var{tty} parameter specifies the name of the bidirectional file the
30213 interpreter uses for input/output, usually the name of a
30214 pseudoterminal slave on Unix systems. For example:
30217 (@value{GDBP}) new-ui mi /dev/pts/9
30221 runs an MI interpreter on @file{/dev/pts/9}.
30224 @chapter @value{GDBN} Text User Interface
30226 @cindex Text User Interface
30228 The @value{GDBN} Text User Interface (TUI) is a terminal
30229 interface which uses the @code{curses} library to show the source
30230 file, the assembly output, the program registers and @value{GDBN}
30231 commands in separate text windows. The TUI mode is supported only
30232 on platforms where a suitable version of the @code{curses} library
30235 The TUI mode is enabled by default when you invoke @value{GDBN} as
30236 @samp{@value{GDBP} -tui}.
30237 You can also switch in and out of TUI mode while @value{GDBN} runs by
30238 using various TUI commands and key bindings, such as @command{tui
30239 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
30240 @ref{TUI Keys, ,TUI Key Bindings}.
30243 * TUI Overview:: TUI overview
30244 * TUI Keys:: TUI key bindings
30245 * TUI Single Key Mode:: TUI single key mode
30246 * TUI Mouse Support:: TUI mouse support
30247 * TUI Commands:: TUI-specific commands
30248 * TUI Configuration:: TUI configuration variables
30252 @section TUI Overview
30254 In TUI mode, @value{GDBN} can display several text windows:
30258 This window is the @value{GDBN} command window with the @value{GDBN}
30259 prompt and the @value{GDBN} output. The @value{GDBN} input is still
30260 managed using readline.
30263 The source window shows the source file of the program. The current
30264 line and active breakpoints are displayed in this window.
30267 The assembly window shows the disassembly output of the program.
30270 This window shows the processor registers. Registers are highlighted
30271 when their values change.
30274 The source and assembly windows show the current program position by
30275 highlighting the current line and marking it with a @samp{>} marker.
30276 By default, source and assembly code styling is disabled for the
30277 highlighted text, but you can enable it with the @code{set style
30278 tui-current-position on} command. @xref{Output Styling}.
30280 Breakpoints are indicated with two markers. The first marker
30281 indicates the breakpoint type:
30285 Breakpoint which was hit at least once.
30288 Breakpoint which was never hit.
30291 Hardware breakpoint which was hit at least once.
30294 Hardware breakpoint which was never hit.
30297 The second marker indicates whether the breakpoint is enabled or not:
30301 Breakpoint is enabled.
30304 Breakpoint is disabled.
30307 The source, assembly and register windows are updated when the current
30308 thread changes, when the frame changes, or when the program counter
30311 These windows are not all visible at the same time. The command
30312 window is always visible. The others can be arranged in several
30323 source and assembly,
30326 source and registers, or
30329 assembly and registers.
30332 These are the standard layouts, but other layouts can be defined.
30334 A status line above the command window shows the following information:
30338 Indicates the current @value{GDBN} target.
30339 (@pxref{Targets, ,Specifying a Debugging Target}).
30342 Gives the current process or thread number.
30343 When no process is being debugged, this field is set to @code{No process}.
30346 Shows the name of the TUI window that has the focus.
30349 Gives the current function name for the selected frame.
30350 The name is demangled if demangling is turned on (@pxref{Print Settings}).
30351 When there is no symbol corresponding to the current program counter,
30352 the string @code{??} is displayed.
30355 Indicates the current line number for the selected frame.
30356 When the current line number is not known, the string @code{??} is displayed.
30359 Indicates the current program counter address.
30363 @section TUI Key Bindings
30364 @cindex TUI key bindings
30366 The TUI installs several key bindings in the readline keymaps
30367 @ifset SYSTEM_READLINE
30368 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
30370 @ifclear SYSTEM_READLINE
30371 (@pxref{Command Line Editing}).
30373 The following key bindings are installed for both TUI mode and the
30374 @value{GDBN} standard mode.
30383 Enter or leave the TUI mode. When leaving the TUI mode,
30384 the curses window management stops and @value{GDBN} operates using
30385 its standard mode, writing on the terminal directly. When reentering
30386 the TUI mode, control is given back to the curses windows.
30387 The screen is then refreshed.
30389 This key binding uses the bindable Readline function
30390 @code{tui-switch-mode}.
30394 Use a TUI layout with only one window. The layout will
30395 either be @samp{source} or @samp{assembly}. When the TUI mode
30396 is not active, it will switch to the TUI mode.
30398 Think of this key binding as the Emacs @kbd{C-x 1} binding.
30400 This key binding uses the bindable Readline function
30401 @code{tui-delete-other-windows}.
30405 Use a TUI layout with at least two windows. When the current
30406 layout already has two windows, the next layout with two windows is used.
30407 When a new layout is chosen, one window will always be common to the
30408 previous layout and the new one.
30410 Think of it as the Emacs @kbd{C-x 2} binding.
30412 This key binding uses the bindable Readline function
30413 @code{tui-change-windows}.
30417 Change the active window. The TUI associates several key bindings
30418 (like scrolling and arrow keys) with the active window. This command
30419 gives the focus to the next TUI window.
30421 Think of it as the Emacs @kbd{C-x o} binding.
30423 This key binding uses the bindable Readline function
30424 @code{tui-other-window}.
30428 Switch in and out of the TUI SingleKey mode that binds single
30429 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
30431 This key binding uses the bindable Readline function
30432 @code{next-keymap}.
30435 The following key bindings only work in the TUI mode:
30440 Scroll the active window one page up.
30444 Scroll the active window one page down.
30448 Scroll the active window one line up.
30452 Scroll the active window one line down.
30456 Scroll the active window one column left.
30460 Scroll the active window one column right.
30464 Refresh the screen.
30467 Because the arrow keys scroll the active window in the TUI mode, they
30468 are not available for their normal use by readline unless the command
30469 window has the focus. When another window is active, you must use
30470 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
30471 and @kbd{C-f} to control the command window.
30473 @node TUI Single Key Mode
30474 @section TUI Single Key Mode
30475 @cindex TUI single key mode
30477 The TUI also provides a @dfn{SingleKey} mode, which binds several
30478 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
30479 switch into this mode, where the following key bindings are used:
30482 @kindex c @r{(SingleKey TUI key)}
30486 @kindex C @r{(SingleKey TUI key)}
30490 @kindex d @r{(SingleKey TUI key)}
30494 @kindex f @r{(SingleKey TUI key)}
30498 @kindex F @r{(SingleKey TUI key)}
30502 @kindex n @r{(SingleKey TUI key)}
30506 @kindex N @r{(SingleKey TUI key)}
30510 @kindex o @r{(SingleKey TUI key)}
30512 nexti. The shortcut letter @samp{o} stands for ``step Over''.
30514 @kindex O @r{(SingleKey TUI key)}
30518 @kindex q @r{(SingleKey TUI key)}
30520 exit the SingleKey mode.
30522 @kindex r @r{(SingleKey TUI key)}
30526 @kindex s @r{(SingleKey TUI key)}
30530 @kindex S @r{(SingleKey TUI key)}
30534 @kindex i @r{(SingleKey TUI key)}
30536 stepi. The shortcut letter @samp{i} stands for ``step Into''.
30538 @kindex I @r{(SingleKey TUI key)}
30542 @kindex u @r{(SingleKey TUI key)}
30546 @kindex v @r{(SingleKey TUI key)}
30550 @kindex w @r{(SingleKey TUI key)}
30555 Other keys temporarily switch to the @value{GDBN} command prompt.
30556 The key that was pressed is inserted in the editing buffer so that
30557 it is possible to type most @value{GDBN} commands without interaction
30558 with the TUI SingleKey mode. Once the command is entered the TUI
30559 SingleKey mode is restored. The only way to permanently leave
30560 this mode is by typing @kbd{q} or @kbd{C-x s}.
30562 @cindex SingleKey keymap name
30563 If @value{GDBN} was built with Readline 8.0 or later, the TUI
30564 SingleKey keymap will be named @samp{SingleKey}. This can be used in
30565 @file{.inputrc} to add additional bindings to this keymap.
30567 @node TUI Mouse Support
30568 @section TUI Mouse Support
30569 @cindex TUI mouse support
30571 If the curses library supports the mouse, the TUI supports mouse
30574 The mouse wheel scrolls the appropriate window under the mouse cursor.
30576 The TUI itself does not directly support copying/pasting with the
30577 mouse. However, on Unix terminals, you can typically press and hold
30578 the @key{SHIFT} key on your keyboard to temporarily bypass
30579 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
30580 functionality (commonly, click-drag-release or double-click to select
30581 text, middle-click to paste). This copy/paste works with the
30582 terminal's selection buffer, as opposed to the TUI's buffer. Alternatively, to
30583 disable mouse support in the TUI entirely and give the terminal control over
30584 mouse clicks, turn off the @code{tui mouse-events} setting
30585 (@pxref{tui-mouse-events,,set tui mouse-events}).
30587 Python extensions can react to mouse clicks
30588 (@pxref{python-window-click,,Window.click}).
30591 @section TUI-specific Commands
30592 @cindex TUI commands
30594 The TUI has specific commands to control the text windows.
30595 These commands are always available, even when @value{GDBN} is not in
30596 the TUI mode. When @value{GDBN} is in the standard mode, most
30597 of these commands will automatically switch to the TUI mode.
30599 Note that if @value{GDBN}'s @code{stdout} is not connected to a
30600 terminal, or @value{GDBN} has been started with the machine interface
30601 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
30602 these commands will fail with an error, because it would not be
30603 possible or desirable to enable curses window management.
30608 Activate TUI mode. The last active TUI window layout will be used if
30609 TUI mode has previously been used in the current debugging session,
30610 otherwise a default layout is used.
30613 @kindex tui disable
30614 Disable TUI mode, returning to the console interpreter.
30616 @anchor{info_win_command}
30619 List the names and sizes of all currently displayed windows.
30621 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
30622 @kindex tui new-layout
30623 Create a new TUI layout. The new layout will be named @var{name}, and
30624 can be accessed using the @code{layout} command (see below).
30626 Each @var{window} parameter is either the name of a window to display,
30627 or a window description. The windows will be displayed from top to
30628 bottom in the order listed.
30630 The names of the windows are the same as the ones given to the
30631 @code{focus} command (see below); additionally, the @code{status}
30632 window can be specified. Note that, because it is of fixed height,
30633 the weight assigned to the status window is of no importance. It is
30634 conventional to use @samp{0} here.
30636 A window description looks a bit like an invocation of @code{tui
30637 new-layout}, and is of the form
30638 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
30640 This specifies a sub-layout. If @code{-horizontal} is given, the
30641 windows in this description will be arranged side-by-side, rather than
30644 Each @var{weight} is an integer. It is the weight of this window
30645 relative to all the other windows in the layout. These numbers are
30646 used to calculate how much of the screen is given to each window.
30651 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
30654 Here, the new layout is called @samp{example}. It shows the source
30655 and register windows, followed by the status window, and then finally
30656 the command window. The non-status windows all have the same weight,
30657 so the terminal will be split into three roughly equal sections.
30659 Here is a more complex example, showing a horizontal layout:
30662 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
30665 This will result in side-by-side source and assembly windows; with the
30666 status and command window being beneath these, filling the entire
30667 width of the terminal. Because they have weight 2, the source and
30668 assembly windows will be twice the height of the command window.
30672 @item tui layout @var{name}
30673 @itemx layout @var{name}
30674 Changes which TUI windows are displayed. The @var{name} parameter
30675 controls which layout is shown. It can be either one of the built-in
30676 layout names, or the name of a layout defined by the user using
30677 @code{tui new-layout}.
30679 The built-in layouts are as follows:
30683 Display the next layout.
30686 Display the previous layout.
30689 Display the source and command windows.
30692 Display the assembly and command windows.
30695 Display the source, assembly, and command windows.
30698 When in @code{src} layout display the register, source, and command
30699 windows. When in @code{asm} or @code{split} layout display the
30700 register, assembler, and command windows.
30704 @item tui focus @var{name}
30705 @itemx focus @var{name}
30706 Changes which TUI window is currently active for scrolling. The
30707 @var{name} parameter can be any of the following:
30711 Make the next window active for scrolling.
30714 Make the previous window active for scrolling.
30717 Make the source window active for scrolling.
30720 Make the assembly window active for scrolling.
30723 Make the register window active for scrolling.
30726 Make the command window active for scrolling.
30729 @kindex tui refresh
30733 Refresh the screen. This is similar to typing @kbd{C-L}.
30735 @item tui reg @var{group}
30737 Changes the register group displayed in the tui register window to
30738 @var{group}. If the register window is not currently displayed this
30739 command will cause the register window to be displayed. The list of
30740 register groups, as well as their order is target specific. The
30741 following groups are available on most targets:
30744 Repeatedly selecting this group will cause the display to cycle
30745 through all of the available register groups.
30748 Repeatedly selecting this group will cause the display to cycle
30749 through all of the available register groups in the reverse order to
30753 Display the general registers.
30755 Display the floating point registers.
30757 Display the system registers.
30759 Display the vector registers.
30761 Display all registers.
30766 Update the source window and the current execution point.
30768 @kindex tui window height
30770 @item tui window height @var{name} +@var{count}
30771 @itemx tui window height @var{name} -@var{count}
30772 @itemx winheight @var{name} +@var{count}
30773 @itemx winheight @var{name} -@var{count}
30774 Change the height of the window @var{name} by @var{count} lines.
30775 Positive counts increase the height, while negative counts decrease
30776 it. The @var{name} parameter can be the name of any currently visible
30777 window. The names of the currently visible windows can be discovered
30778 using @kbd{info win} (@pxref{info_win_command,,info win}).
30780 The set of currently visible windows must always fill the terminal,
30781 and so, it is only possible to resize on window if there are other
30782 visible windows that can either give or receive the extra terminal
30785 @kindex tui window width
30787 @item tui window width @var{name} +@var{count}
30788 @itemx tui window width @var{name} -@var{count}
30789 @itemx winwidth @var{name} +@var{count}
30790 @itemx winwidth @var{name} -@var{count}
30791 Change the width of the window @var{name} by @var{count} columns.
30792 Positive counts increase the width, while negative counts decrease it.
30793 The @var{name} parameter can be the name of any currently visible
30794 window. The names of the currently visible windows can be discovered
30795 using @code{info win} (@pxref{info_win_command,,info win}).
30797 The set of currently visible windows must always fill the terminal,
30798 and so, it is only possible to resize on window if there are other
30799 visible windows that can either give or receive the extra terminal
30803 @node TUI Configuration
30804 @section TUI Configuration Variables
30805 @cindex TUI configuration variables
30807 Several configuration variables control the appearance of TUI windows.
30810 @item set tui border-kind @var{kind}
30811 @kindex set tui border-kind
30812 Select the border appearance for the source, assembly and register windows.
30813 The possible values are the following:
30816 Use a space character to draw the border.
30819 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
30822 Use the Alternate Character Set to draw the border. The border is
30823 drawn using character line graphics if the terminal supports them.
30826 @item set tui border-mode @var{mode}
30827 @kindex set tui border-mode
30828 @itemx set tui active-border-mode @var{mode}
30829 @kindex set tui active-border-mode
30830 Select the display attributes for the borders of the inactive windows
30831 or the active window. The @var{mode} can be one of the following:
30834 Use normal attributes to display the border.
30840 Use reverse video mode.
30843 Use half bright mode.
30845 @item half-standout
30846 Use half bright and standout mode.
30849 Use extra bright or bold mode.
30851 @item bold-standout
30852 Use extra bright or bold and standout mode.
30855 @item set tui tab-width @var{nchars}
30856 @kindex set tui tab-width
30858 Set the width of tab stops to be @var{nchars} characters. This
30859 setting affects the display of TAB characters in the source and
30862 @item set tui compact-source @r{[}on@r{|}off@r{]}
30863 @kindex set tui compact-source
30864 Set whether the TUI source window is displayed in ``compact'' form.
30865 The default display uses more space for line numbers; the compact
30866 display uses only as much space as is needed for the line numbers in
30869 @anchor{tui-mouse-events}
30870 @item set tui mouse-events @r{[}on@r{|}off@r{]}
30871 @kindex set tui mouse-events
30872 When on (default), mouse clicks control the TUI (@pxref{TUI Mouse Support}).
30873 When off, mouse clicks are handled by the terminal, enabling terminal-native
30876 @kindex set debug tui
30877 @item set debug tui @r{[}on|off@r{]}
30878 Turn on or off display of @value{GDBN} internal debug messages relating
30881 @kindex show debug tui
30882 @item show debug tui
30883 Show the current status of displaying @value{GDBN} internal debug
30884 messages relating to the TUI.
30888 Note that the colors of the TUI borders can be controlled using the
30889 appropriate @code{set style} commands. @xref{Output Styling}.
30892 @chapter Using @value{GDBN} under @sc{gnu} Emacs
30895 @cindex @sc{gnu} Emacs
30896 A special interface allows you to use @sc{gnu} Emacs to view (and
30897 edit) the source files for the program you are debugging with
30900 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
30901 executable file you want to debug as an argument. This command starts
30902 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
30903 created Emacs buffer.
30904 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
30906 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
30911 All ``terminal'' input and output goes through an Emacs buffer, called
30914 This applies both to @value{GDBN} commands and their output, and to the input
30915 and output done by the program you are debugging.
30917 This is useful because it means that you can copy the text of previous
30918 commands and input them again; you can even use parts of the output
30921 All the facilities of Emacs' Shell mode are available for interacting
30922 with your program. In particular, you can send signals the usual
30923 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
30927 @value{GDBN} displays source code through Emacs.
30929 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
30930 source file for that frame and puts an arrow (@samp{=>}) at the
30931 left margin of the current line. Emacs uses a separate buffer for
30932 source display, and splits the screen to show both your @value{GDBN} session
30935 Explicit @value{GDBN} @code{list} or search commands still produce output as
30936 usual, but you probably have no reason to use them from Emacs.
30939 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
30940 a graphical mode, enabled by default, which provides further buffers
30941 that can control the execution and describe the state of your program.
30942 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
30944 If you specify an absolute file name when prompted for the @kbd{M-x
30945 gdb} argument, then Emacs sets your current working directory to where
30946 your program resides. If you only specify the file name, then Emacs
30947 sets your current working directory to the directory associated
30948 with the previous buffer. In this case, @value{GDBN} may find your
30949 program by searching your environment's @env{PATH} variable, but on
30950 some operating systems it might not find the source. So, although the
30951 @value{GDBN} input and output session proceeds normally, the auxiliary
30952 buffer does not display the current source and line of execution.
30954 The initial working directory of @value{GDBN} is printed on the top
30955 line of the GUD buffer and this serves as a default for the commands
30956 that specify files for @value{GDBN} to operate on. @xref{Files,
30957 ,Commands to Specify Files}.
30959 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
30960 need to call @value{GDBN} by a different name (for example, if you
30961 keep several configurations around, with different names) you can
30962 customize the Emacs variable @code{gud-gdb-command-name} to run the
30965 In the GUD buffer, you can use these special Emacs commands in
30966 addition to the standard Shell mode commands:
30970 Describe the features of Emacs' GUD Mode.
30973 Execute to another source line, like the @value{GDBN} @code{step} command; also
30974 update the display window to show the current file and location.
30977 Execute to next source line in this function, skipping all function
30978 calls, like the @value{GDBN} @code{next} command. Then update the display window
30979 to show the current file and location.
30982 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
30983 display window accordingly.
30986 Execute until exit from the selected stack frame, like the @value{GDBN}
30987 @code{finish} command.
30990 Continue execution of your program, like the @value{GDBN} @code{continue}
30994 Go up the number of frames indicated by the numeric argument
30995 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
30996 like the @value{GDBN} @code{up} command.
30999 Go down the number of frames indicated by the numeric argument, like the
31000 @value{GDBN} @code{down} command.
31003 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
31004 tells @value{GDBN} to set a breakpoint on the source line point is on.
31006 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
31007 separate frame which shows a backtrace when the GUD buffer is current.
31008 Move point to any frame in the stack and type @key{RET} to make it
31009 become the current frame and display the associated source in the
31010 source buffer. Alternatively, click @kbd{Mouse-2} to make the
31011 selected frame become the current one. In graphical mode, the
31012 speedbar displays watch expressions.
31014 If you accidentally delete the source-display buffer, an easy way to get
31015 it back is to type the command @code{f} in the @value{GDBN} buffer, to
31016 request a frame display; when you run under Emacs, this recreates
31017 the source buffer if necessary to show you the context of the current
31020 The source files displayed in Emacs are in ordinary Emacs buffers
31021 which are visiting the source files in the usual way. You can edit
31022 the files with these buffers if you wish; but keep in mind that @value{GDBN}
31023 communicates with Emacs in terms of line numbers. If you add or
31024 delete lines from the text, the line numbers that @value{GDBN} knows cease
31025 to correspond properly with the code.
31027 A more detailed description of Emacs' interaction with @value{GDBN} is
31028 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
31032 @chapter The @sc{gdb/mi} Interface
31034 @unnumberedsec Function and Purpose
31036 @cindex @sc{gdb/mi}, its purpose
31037 @sc{gdb/mi} is a line based machine oriented text interface to
31038 @value{GDBN} and is activated by specifying using the
31039 @option{--interpreter} command line option (@pxref{Mode Options}). It
31040 is specifically intended to support the development of systems which
31041 use the debugger as just one small component of a larger system.
31043 This chapter is a specification of the @sc{gdb/mi} interface. It is written
31044 in the form of a reference manual.
31046 Note that @sc{gdb/mi} is still under construction, so some of the
31047 features described below are incomplete and subject to change
31048 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
31050 @unnumberedsec Notation and Terminology
31052 @cindex notational conventions, for @sc{gdb/mi}
31053 This chapter uses the following notation:
31057 @code{|} separates two alternatives.
31060 @code{[ @var{something} ]} indicates that @var{something} is optional:
31061 it may or may not be given.
31064 @code{( @var{group} )*} means that @var{group} inside the parentheses
31065 may repeat zero or more times.
31068 @code{( @var{group} )+} means that @var{group} inside the parentheses
31069 may repeat one or more times.
31072 @code{( @var{group} )} means that @var{group} inside the parentheses
31073 occurs exactly once.
31076 @code{"@var{string}"} means a literal @var{string}.
31080 @heading Dependencies
31084 * GDB/MI General Design::
31085 * GDB/MI Command Syntax::
31086 * GDB/MI Compatibility with CLI::
31087 * GDB/MI Development and Front Ends::
31088 * GDB/MI Output Records::
31089 * GDB/MI Simple Examples::
31090 * GDB/MI Command Description Format::
31091 * GDB/MI Breakpoint Commands::
31092 * GDB/MI Catchpoint Commands::
31093 * GDB/MI Program Context::
31094 * GDB/MI Thread Commands::
31095 * GDB/MI Ada Tasking Commands::
31096 * GDB/MI Program Execution::
31097 * GDB/MI Stack Manipulation::
31098 * GDB/MI Variable Objects::
31099 * GDB/MI Data Manipulation::
31100 * GDB/MI Tracepoint Commands::
31101 * GDB/MI Symbol Query::
31102 * GDB/MI File Commands::
31104 * GDB/MI Kod Commands::
31105 * GDB/MI Memory Overlay Commands::
31106 * GDB/MI Signal Handling Commands::
31108 * GDB/MI Target Manipulation::
31109 * GDB/MI File Transfer Commands::
31110 * GDB/MI Ada Exceptions Commands::
31111 * GDB/MI Support Commands::
31112 * GDB/MI Miscellaneous Commands::
31115 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31116 @node GDB/MI General Design
31117 @section @sc{gdb/mi} General Design
31118 @cindex GDB/MI General Design
31120 Interaction of a @sc{gdb/mi} frontend with @value{GDBN} involves three
31121 parts---commands sent to @value{GDBN}, responses to those commands
31122 and notifications. Each command results in exactly one response,
31123 indicating either successful completion of the command, or an error.
31124 For the commands that do not resume the target, the response contains the
31125 requested information. For the commands that resume the target, the
31126 response only indicates whether the target was successfully resumed.
31127 Notifications is the mechanism for reporting changes in the state of the
31128 target, or in @value{GDBN} state, that cannot conveniently be associated with
31129 a command and reported as part of that command response.
31131 The important examples of notifications are:
31135 Exec notifications. These are used to report changes in
31136 target state---when a target is resumed, or stopped. It would not
31137 be feasible to include this information in response of resuming
31138 commands, because one resume commands can result in multiple events in
31139 different threads. Also, quite some time may pass before any event
31140 happens in the target, while a frontend needs to know whether the resuming
31141 command itself was successfully executed.
31144 Console output, and status notifications. Console output
31145 notifications are used to report output of CLI commands, as well as
31146 diagnostics for other commands. Status notifications are used to
31147 report the progress of a long-running operation. Naturally, including
31148 this information in command response would mean no output is produced
31149 until the command is finished, which is undesirable.
31152 General notifications. Commands may have various side effects on
31153 the @value{GDBN} or target state beyond their official purpose. For example,
31154 a command may change the selected thread. Although such changes can
31155 be included in command response, using notification allows for more
31156 orthogonal frontend design.
31160 There's no guarantee that whenever an MI command reports an error,
31161 @value{GDBN} or the target are in any specific state, and especially,
31162 the state is not reverted to the state before the MI command was
31163 processed. Therefore, whenever an MI command results in an error,
31164 we recommend that the frontend refreshes all the information shown in
31165 the user interface.
31169 * Context management::
31170 * Asynchronous and non-stop modes::
31174 @node Context management
31175 @subsection Context management
31177 @subsubsection Threads and Frames
31179 In most cases when @value{GDBN} accesses the target, this access is
31180 done in context of a specific thread and frame (@pxref{Frames}).
31181 Often, even when accessing global data, the target requires that a thread
31182 be specified. The CLI interface maintains the selected thread and frame,
31183 and supplies them to target on each command. This is convenient,
31184 because a command line user would not want to specify that information
31185 explicitly on each command, and because user interacts with
31186 @value{GDBN} via a single terminal, so no confusion is possible as
31187 to what thread and frame are the current ones.
31189 In the case of MI, the concept of selected thread and frame is less
31190 useful. First, a frontend can easily remember this information
31191 itself. Second, a graphical frontend can have more than one window,
31192 each one used for debugging a different thread, and the frontend might
31193 want to access additional threads for internal purposes. This
31194 increases the risk that by relying on implicitly selected thread, the
31195 frontend may be operating on a wrong one. Therefore, each MI command
31196 should explicitly specify which thread and frame to operate on. To
31197 make it possible, each MI command accepts the @samp{--thread} and
31198 @samp{--frame} options, the value to each is @value{GDBN} global
31199 identifier for thread and frame to operate on.
31201 Usually, each top-level window in a frontend allows the user to select
31202 a thread and a frame, and remembers the user selection for further
31203 operations. However, in some cases @value{GDBN} may suggest that the
31204 current thread or frame be changed. For example, when stopping on a
31205 breakpoint it is reasonable to switch to the thread where breakpoint is
31206 hit. For another example, if the user issues the CLI @samp{thread} or
31207 @samp{frame} commands via the frontend, it is desirable to change the
31208 frontend's selection to the one specified by user. @value{GDBN}
31209 communicates the suggestion to change current thread and frame using the
31210 @samp{=thread-selected} notification.
31212 Note that historically, MI shares the selected thread with CLI, so
31213 frontends used the @code{-thread-select} to execute commands in the
31214 right context. However, getting this to work right is cumbersome. The
31215 simplest way is for frontend to emit @code{-thread-select} command
31216 before every command. This doubles the number of commands that need
31217 to be sent. The alternative approach is to suppress @code{-thread-select}
31218 if the selected thread in @value{GDBN} is supposed to be identical to the
31219 thread the frontend wants to operate on. However, getting this
31220 optimization right can be tricky. In particular, if the frontend
31221 sends several commands to @value{GDBN}, and one of the commands changes the
31222 selected thread, then the behaviour of subsequent commands will
31223 change. So, a frontend should either wait for response from such
31224 problematic commands, or explicitly add @code{-thread-select} for
31225 all subsequent commands. No frontend is known to do this exactly
31226 right, so it is suggested to just always pass the @samp{--thread} and
31227 @samp{--frame} options.
31229 @subsubsection Language
31231 The execution of several commands depends on which language is selected.
31232 By default, the current language (@pxref{show language}) is used.
31233 But for commands known to be language-sensitive, it is recommended
31234 to use the @samp{--language} option. This option takes one argument,
31235 which is the name of the language to use while executing the command.
31239 -data-evaluate-expression --language c "sizeof (void*)"
31244 The valid language names are the same names accepted by the
31245 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
31246 @samp{local} or @samp{unknown}.
31248 @node Asynchronous and non-stop modes
31249 @subsection Asynchronous command execution and non-stop mode
31251 On some targets, @value{GDBN} is capable of processing MI commands
31252 even while the target is running. This is called @dfn{asynchronous
31253 command execution} (@pxref{Background Execution}). The frontend may
31254 specify a preference for asynchronous execution using the
31255 @code{-gdb-set mi-async 1} command, which should be emitted before
31256 either running the executable or attaching to the target. After the
31257 frontend has started the executable or attached to the target, it can
31258 find if asynchronous execution is enabled using the
31259 @code{-list-target-features} command.
31262 @cindex foreground execution
31263 @cindex background execution
31264 @cindex asynchronous execution
31265 @cindex execution, foreground, background and asynchronous
31266 @kindex set mi-async
31267 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
31268 Set whether MI is in asynchronous mode.
31270 When @code{off}, which is the default, MI execution commands (e.g.,
31271 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
31272 for the program to stop before processing further commands.
31274 When @code{on}, MI execution commands are background execution
31275 commands (e.g., @code{-exec-continue} becomes the equivalent of the
31276 @code{c&} CLI command), and so @value{GDBN} is capable of processing
31277 MI commands even while the target is running.
31279 @kindex show mi-async
31280 @item -gdb-show mi-async
31281 Show whether MI asynchronous mode is enabled.
31284 Note: In @value{GDBN} version 7.7 and earlier, this option was called
31285 @code{target-async} instead of @code{mi-async}, and it had the effect
31286 of both putting MI in asynchronous mode and making CLI background
31287 commands possible. CLI background commands are now always possible
31288 ``out of the box'' if the target supports them. The old spelling is
31289 kept as a deprecated alias for backwards compatibility.
31291 Even if @value{GDBN} can accept a command while target is running,
31292 many commands that access the target do not work when the target is
31293 running. Therefore, asynchronous command execution is most useful
31294 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
31295 it is possible to examine the state of one thread, while other threads
31298 When a given thread is running, MI commands that try to access the
31299 target in the context of that thread may not work, or may work only on
31300 some targets. In particular, commands that try to operate on thread's
31301 stack will not work, on any target. Commands that read memory, or
31302 modify breakpoints, may work or not work, depending on the target. Note
31303 that even commands that operate on global state, such as @code{print},
31304 @code{set}, and breakpoint commands, still access the target in the
31305 context of a specific thread, so frontend should try to find a
31306 stopped thread and perform the operation on that thread (using the
31307 @samp{--thread} option).
31309 Which commands will work in the context of a running thread is
31310 highly target dependent. However, the two commands
31311 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
31312 to find the state of a thread, will always work.
31314 @node Thread groups
31315 @subsection Thread groups
31316 @value{GDBN} may be used to debug several processes at the same time.
31317 On some platforms, @value{GDBN} may support debugging of several
31318 hardware systems, each one having several cores with several different
31319 processes running on each core. This section describes the MI
31320 mechanism to support such debugging scenarios.
31322 The key observation is that regardless of the structure of the
31323 target, MI can have a global list of threads, because most commands that
31324 accept the @samp{--thread} option do not need to know what process that
31325 thread belongs to. Therefore, it is not necessary to introduce
31326 neither additional @samp{--process} option, nor an notion of the
31327 current process in the MI interface. The only strictly new feature
31328 that is required is the ability to find how the threads are grouped
31331 To allow the user to discover such grouping, and to support arbitrary
31332 hierarchy of machines/cores/processes, MI introduces the concept of a
31333 @dfn{thread group}. Thread group is a collection of threads and other
31334 thread groups. A thread group always has a string identifier, a type,
31335 and may have additional attributes specific to the type. A new
31336 command, @code{-list-thread-groups}, returns the list of top-level
31337 thread groups, which correspond to processes that @value{GDBN} is
31338 debugging at the moment. By passing an identifier of a thread group
31339 to the @code{-list-thread-groups} command, it is possible to obtain
31340 the members of specific thread group.
31342 To allow the user to easily discover processes, and other objects, he
31343 wishes to debug, a concept of @dfn{available thread group} is
31344 introduced. Available thread group is an thread group that
31345 @value{GDBN} is not debugging, but that can be attached to, using the
31346 @code{-target-attach} command. The list of available top-level thread
31347 groups can be obtained using @samp{-list-thread-groups --available}.
31348 In general, the content of a thread group may be only retrieved only
31349 after attaching to that thread group.
31351 Thread groups are related to inferiors (@pxref{Inferiors Connections and
31352 Programs}). Each inferior corresponds to a thread group of a special
31353 type @samp{process}, and some additional operations are permitted on
31354 such thread groups.
31356 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31357 @node GDB/MI Command Syntax
31358 @section @sc{gdb/mi} Command Syntax
31361 * GDB/MI Input Syntax::
31362 * GDB/MI Output Syntax::
31365 @node GDB/MI Input Syntax
31366 @subsection @sc{gdb/mi} Input Syntax
31368 @cindex input syntax for @sc{gdb/mi}
31369 @cindex @sc{gdb/mi}, input syntax
31371 @item @var{command} @expansion{}
31372 @code{@var{cli-command} | @var{mi-command}}
31374 @item @var{cli-command} @expansion{}
31375 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
31376 @var{cli-command} is any existing @value{GDBN} CLI command.
31378 @item @var{mi-command} @expansion{}
31379 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
31380 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
31382 @item @var{token} @expansion{}
31383 "any sequence of digits"
31385 @item @var{option} @expansion{}
31386 @code{"-" @var{parameter} [ " " @var{parameter} ]}
31388 @item @var{parameter} @expansion{}
31389 @code{@var{non-blank-sequence} | @var{c-string}}
31391 @item @var{operation} @expansion{}
31392 @emph{any of the operations described in this chapter}
31394 @item @var{non-blank-sequence} @expansion{}
31395 @emph{anything, provided it doesn't contain special characters such as
31396 "-", @var{nl}, """ and of course " "}
31398 @item @var{c-string} @expansion{}
31399 @code{""" @var{seven-bit-iso-c-string-content} """}
31401 @item @var{nl} @expansion{}
31410 The CLI commands are still handled by the @sc{mi} interpreter; their
31411 output is described below.
31414 The @code{@var{token}}, when present, is passed back when the command
31418 Some @sc{mi} commands accept optional arguments as part of the parameter
31419 list. Each option is identified by a leading @samp{-} (dash) and may be
31420 followed by an optional argument parameter. Options occur first in the
31421 parameter list and can be delimited from normal parameters using
31422 @samp{--} (this is useful when some parameters begin with a dash).
31429 We want easy access to the existing CLI syntax (for debugging).
31432 We want it to be easy to spot a @sc{mi} operation.
31435 @node GDB/MI Output Syntax
31436 @subsection @sc{gdb/mi} Output Syntax
31438 @cindex output syntax of @sc{gdb/mi}
31439 @cindex @sc{gdb/mi}, output syntax
31440 The output from @sc{gdb/mi} consists of zero or more out-of-band records
31441 followed, optionally, by a single result record. This result record
31442 is for the most recent command. The sequence of output records is
31443 terminated by @samp{(gdb)}.
31445 If an input command was prefixed with a @code{@var{token}} then the
31446 corresponding output for that command will also be prefixed by that same
31450 @item @var{output} @expansion{}
31451 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
31453 @item @var{result-record} @expansion{}
31454 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
31456 @item @var{out-of-band-record} @expansion{}
31457 @code{@var{async-record} | @var{stream-record}}
31459 @item @var{async-record} @expansion{}
31460 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
31462 @item @var{exec-async-output} @expansion{}
31463 @code{[ @var{token} ] "*" @var{async-output nl}}
31465 @item @var{status-async-output} @expansion{}
31466 @code{[ @var{token} ] "+" @var{async-output nl}}
31468 @item @var{notify-async-output} @expansion{}
31469 @code{[ @var{token} ] "=" @var{async-output nl}}
31471 @item @var{async-output} @expansion{}
31472 @code{@var{async-class} ( "," @var{result} )*}
31474 @item @var{result-class} @expansion{}
31475 @code{"done" | "running" | "connected" | "error" | "exit"}
31477 @item @var{async-class} @expansion{}
31478 @code{"stopped" | @var{others}} (where @var{others} will be added
31479 depending on the needs---this is still in development).
31481 @item @var{result} @expansion{}
31482 @code{ @var{variable} "=" @var{value}}
31484 @item @var{variable} @expansion{}
31485 @code{ @var{string} }
31487 @item @var{value} @expansion{}
31488 @code{ @var{const} | @var{tuple} | @var{list} }
31490 @item @var{const} @expansion{}
31491 @code{@var{c-string}}
31493 @item @var{tuple} @expansion{}
31494 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
31496 @item @var{list} @expansion{}
31497 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
31498 @var{result} ( "," @var{result} )* "]" }
31500 @item @var{stream-record} @expansion{}
31501 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
31503 @item @var{console-stream-output} @expansion{}
31504 @code{"~" @var{c-string nl}}
31506 @item @var{target-stream-output} @expansion{}
31507 @code{"@@" @var{c-string nl}}
31509 @item @var{log-stream-output} @expansion{}
31510 @code{"&" @var{c-string nl}}
31512 @item @var{nl} @expansion{}
31515 @item @var{token} @expansion{}
31516 @emph{any sequence of digits}.
31524 All output sequences end in a single line containing a period.
31527 The @code{@var{token}} is from the corresponding request. Note that
31528 for all async output, while the token is allowed by the grammar and
31529 may be output by future versions of @value{GDBN} for select async
31530 output messages, it is generally omitted. Frontends should treat
31531 all async output as reporting general changes in the state of the
31532 target and there should be no need to associate async output to any
31536 @cindex status output in @sc{gdb/mi}
31537 @var{status-async-output} contains on-going status information about the
31538 progress of a slow operation. It can be discarded. All status output is
31539 prefixed by @samp{+}.
31542 @cindex async output in @sc{gdb/mi}
31543 @var{exec-async-output} contains asynchronous state change on the target
31544 (stopped, started, disappeared). All async output is prefixed by
31548 @cindex notify output in @sc{gdb/mi}
31549 @var{notify-async-output} contains supplementary information that the
31550 client should handle (e.g., a new breakpoint information). All notify
31551 output is prefixed by @samp{=}.
31554 @cindex console output in @sc{gdb/mi}
31555 @var{console-stream-output} is output that should be displayed as is in the
31556 console. It is the textual response to a CLI command. All the console
31557 output is prefixed by @samp{~}.
31560 @cindex target output in @sc{gdb/mi}
31561 @var{target-stream-output} is the output produced by the target program.
31562 All the target output is prefixed by @samp{@@}.
31565 @cindex log output in @sc{gdb/mi}
31566 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
31567 instance messages that should be displayed as part of an error log. All
31568 the log output is prefixed by @samp{&}.
31571 @cindex list output in @sc{gdb/mi}
31572 New @sc{gdb/mi} commands should only output @var{lists} containing
31578 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
31579 details about the various output records.
31581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31582 @node GDB/MI Compatibility with CLI
31583 @section @sc{gdb/mi} Compatibility with CLI
31585 @cindex compatibility, @sc{gdb/mi} and CLI
31586 @cindex @sc{gdb/mi}, compatibility with CLI
31588 For the developers convenience CLI commands can be entered directly,
31589 but there may be some unexpected behaviour. For example, commands
31590 that query the user will behave as if the user replied yes, breakpoint
31591 command lists are not executed and some CLI commands, such as
31592 @code{if}, @code{when} and @code{define}, prompt for further input with
31593 @samp{>}, which is not valid MI output.
31595 This feature may be removed at some stage in the future and it is
31596 recommended that front ends use the @code{-interpreter-exec} command
31597 (@pxref{-interpreter-exec}).
31599 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31600 @node GDB/MI Development and Front Ends
31601 @section @sc{gdb/mi} Development and Front Ends
31602 @cindex @sc{gdb/mi} development
31604 The application which takes the MI output and presents the state of the
31605 program being debugged to the user is called a @dfn{front end}.
31607 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
31608 to the MI interface may break existing usage. This section describes how the
31609 protocol changes and how to request previous version of the protocol when it
31612 Some changes in MI need not break a carefully designed front end, and
31613 for these the MI version will remain unchanged. The following is a
31614 list of changes that may occur within one level, so front ends should
31615 parse MI output in a way that can handle them:
31619 New MI commands may be added.
31622 New fields may be added to the output of any MI command.
31625 The range of values for fields with specified values, e.g.,
31626 @code{in_scope} (@pxref{-var-update}) may be extended.
31628 @c The format of field's content e.g type prefix, may change so parse it
31629 @c at your own risk. Yes, in general?
31631 @c The order of fields may change? Shouldn't really matter but it might
31632 @c resolve inconsistencies.
31635 If the changes are likely to break front ends, the MI version level
31636 will be increased by one. The new versions of the MI protocol are not compatible
31637 with the old versions. Old versions of MI remain available, allowing front ends
31638 to keep using them until they are modified to use the latest MI version.
31640 Since @code{--interpreter=mi} always points to the latest MI version, it is
31641 recommended that front ends request a specific version of MI when launching
31642 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
31643 interpreter with the MI version they expect.
31645 The following table gives a summary of the released versions of the MI
31646 interface: the version number, the version of GDB in which it first appeared
31647 and the breaking changes compared to the previous version.
31649 @multitable @columnfractions .1 .1 .8
31650 @headitem MI version @tab GDB version @tab Breaking changes
31667 The @code{-environment-pwd}, @code{-environment-directory} and
31668 @code{-environment-path} commands now returns values using the MI output
31669 syntax, rather than CLI output syntax.
31672 @code{-var-list-children}'s @code{children} result field is now a list, rather
31676 @code{-var-update}'s @code{changelist} result field is now a list, rather than
31688 The output of information about multi-location breakpoints has changed in the
31689 responses to the @code{-break-insert} and @code{-break-info} commands, as well
31690 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
31691 The multiple locations are now placed in a @code{locations} field, whose value
31703 The syntax of the "script" field in breakpoint output has changed in the
31704 responses to the @code{-break-insert} and @code{-break-info} commands, as
31705 well as the @code{=breakpoint-created} and @code{=breakpoint-modified}
31706 events. The previous output was syntactically invalid. The new output is
31712 If your front end cannot yet migrate to a more recent version of the
31713 MI protocol, you can nevertheless selectively enable specific features
31714 available in those recent MI versions, using the following commands:
31718 @item -fix-multi-location-breakpoint-output
31719 Use the output for multi-location breakpoints which was introduced by
31720 MI 3, even when using MI versions below 3. This command has no
31721 effect when using MI version 3 or later.
31723 @item -fix-breakpoint-script-output
31724 Use the output for the breakpoint "script" field which was introduced by
31725 MI 4, even when using MI versions below 4. This command has no effect when
31726 using MI version 4 or later.
31730 The best way to avoid unexpected changes in MI that might break your front
31731 end is to make your project known to @value{GDBN} developers and
31732 follow development on @email{gdb@@sourceware.org} and
31733 @email{gdb-patches@@sourceware.org}.
31734 @cindex mailing lists
31736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31737 @node GDB/MI Output Records
31738 @section @sc{gdb/mi} Output Records
31741 * GDB/MI Result Records::
31742 * GDB/MI Stream Records::
31743 * GDB/MI Async Records::
31744 * GDB/MI Breakpoint Information::
31745 * GDB/MI Frame Information::
31746 * GDB/MI Thread Information::
31747 * GDB/MI Ada Exception Information::
31750 @node GDB/MI Result Records
31751 @subsection @sc{gdb/mi} Result Records
31753 @cindex result records in @sc{gdb/mi}
31754 @cindex @sc{gdb/mi}, result records
31755 In addition to a number of out-of-band notifications, the response to a
31756 @sc{gdb/mi} command includes one of the following result indications:
31760 @item "^done" [ "," @var{results} ]
31761 The synchronous operation was successful, @code{@var{results}} are the return
31766 This result record is equivalent to @samp{^done}. Historically, it
31767 was output instead of @samp{^done} if the command has resumed the
31768 target. This behaviour is maintained for backward compatibility, but
31769 all frontends should treat @samp{^done} and @samp{^running}
31770 identically and rely on the @samp{*running} output record to determine
31771 which threads are resumed.
31775 @value{GDBN} has connected to a remote target.
31778 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
31779 The operation failed. The @code{msg=@var{c-string}} variable contains
31780 the corresponding error message.
31782 If present, the @code{code=@var{c-string}} variable provides an error
31783 code on which consumers can rely on to detect the corresponding
31784 error condition. At present, only one error code is defined:
31787 @item "undefined-command"
31788 Indicates that the command causing the error does not exist.
31793 @value{GDBN} has terminated.
31797 @node GDB/MI Stream Records
31798 @subsection @sc{gdb/mi} Stream Records
31800 @cindex @sc{gdb/mi}, stream records
31801 @cindex stream records in @sc{gdb/mi}
31802 @value{GDBN} internally maintains a number of output streams: the console, the
31803 target, and the log. The output intended for each of these streams is
31804 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
31806 Each stream record begins with a unique @dfn{prefix character} which
31807 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
31808 Syntax}). In addition to the prefix, each stream record contains a
31809 @code{@var{string-output}}. This is either raw text (with an implicit new
31810 line) or a quoted C string (which does not contain an implicit newline).
31813 @item "~" @var{string-output}
31814 The console output stream contains text that should be displayed in the
31815 CLI console window. It contains the textual responses to CLI commands.
31817 @item "@@" @var{string-output}
31818 The target output stream contains any textual output from the running
31819 target. This is only present when GDB's event loop is truly
31820 asynchronous, which is currently only the case for remote targets.
31822 @item "&" @var{string-output}
31823 The log stream contains debugging messages being produced by @value{GDBN}'s
31827 @node GDB/MI Async Records
31828 @subsection @sc{gdb/mi} Async Records
31830 @cindex async records in @sc{gdb/mi}
31831 @cindex @sc{gdb/mi}, async records
31832 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
31833 additional changes that have occurred. Those changes can either be a
31834 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
31835 target activity (e.g., target stopped).
31837 The following is the list of possible async records:
31841 @item *running,thread-id="@var{thread}"
31842 The target is now running. The @var{thread} field can be the global
31843 thread ID of the thread that is now running, and it can be
31844 @samp{all} if all threads are running. The frontend should assume
31845 that no interaction with a running thread is possible after this
31846 notification is produced. The frontend should not assume that this
31847 notification is output only once for any command. @value{GDBN} may
31848 emit this notification several times, either for different threads,
31849 because it cannot resume all threads together, or even for a single
31850 thread, if the thread must be stepped though some code before letting
31853 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
31854 The target has stopped. The @var{reason} field can have one of the
31858 @item breakpoint-hit
31859 A breakpoint was reached.
31860 @item watchpoint-trigger
31861 A watchpoint was triggered.
31862 @item read-watchpoint-trigger
31863 A read watchpoint was triggered.
31864 @item access-watchpoint-trigger
31865 An access watchpoint was triggered.
31866 @item function-finished
31867 An -exec-finish or similar CLI command was accomplished.
31868 @item location-reached
31869 An -exec-until or similar CLI command was accomplished.
31870 @item watchpoint-scope
31871 A watchpoint has gone out of scope.
31872 @item end-stepping-range
31873 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
31874 similar CLI command was accomplished.
31875 @item exited-signalled
31876 The inferior exited because of a signal.
31878 The inferior exited.
31879 @item exited-normally
31880 The inferior exited normally.
31881 @item signal-received
31882 A signal was received by the inferior.
31884 The inferior has stopped due to a library being loaded or unloaded.
31885 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
31886 set or when a @code{catch load} or @code{catch unload} catchpoint is
31887 in use (@pxref{Set Catchpoints}).
31889 The inferior has forked. This is reported when @code{catch fork}
31890 (@pxref{Set Catchpoints}) has been used.
31892 The inferior has vforked. This is reported in when @code{catch vfork}
31893 (@pxref{Set Catchpoints}) has been used.
31894 @item syscall-entry
31895 The inferior entered a system call. This is reported when @code{catch
31896 syscall} (@pxref{Set Catchpoints}) has been used.
31897 @item syscall-return
31898 The inferior returned from a system call. This is reported when
31899 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
31901 The inferior called @code{exec}. This is reported when @code{catch exec}
31902 (@pxref{Set Catchpoints}) has been used.
31904 There isn't enough history recorded to continue reverse execution.
31907 The @var{id} field identifies the global thread ID of the thread
31908 that directly caused the stop -- for example by hitting a breakpoint.
31909 Depending on whether all-stop
31910 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
31911 stop all threads, or only the thread that directly triggered the stop.
31912 If all threads are stopped, the @var{stopped} field will have the
31913 value of @code{"all"}. Otherwise, the value of the @var{stopped}
31914 field will be a list of thread identifiers. Presently, this list will
31915 always include a single thread, but frontend should be prepared to see
31916 several threads in the list. The @var{core} field reports the
31917 processor core on which the stop event has happened. This field may be absent
31918 if such information is not available.
31920 @item =thread-group-added,id="@var{id}"
31921 @itemx =thread-group-removed,id="@var{id}"
31922 A thread group was either added or removed. The @var{id} field
31923 contains the @value{GDBN} identifier of the thread group. When a thread
31924 group is added, it generally might not be associated with a running
31925 process. When a thread group is removed, its id becomes invalid and
31926 cannot be used in any way.
31928 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
31929 A thread group became associated with a running program,
31930 either because the program was just started or the thread group
31931 was attached to a program. The @var{id} field contains the
31932 @value{GDBN} identifier of the thread group. The @var{pid} field
31933 contains process identifier, specific to the operating system.
31935 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
31936 A thread group is no longer associated with a running program,
31937 either because the program has exited, or because it was detached
31938 from. The @var{id} field contains the @value{GDBN} identifier of the
31939 thread group. The @var{code} field is the exit code of the inferior; it exists
31940 only when the inferior exited with some code.
31942 @item =thread-created,id="@var{id}",group-id="@var{gid}"
31943 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
31944 A thread either was created, or has exited. The @var{id} field
31945 contains the global @value{GDBN} identifier of the thread. The @var{gid}
31946 field identifies the thread group this thread belongs to.
31948 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
31949 Informs that the selected thread or frame were changed. This notification
31950 is not emitted as result of the @code{-thread-select} or
31951 @code{-stack-select-frame} commands, but is emitted whenever an MI command
31952 that is not documented to change the selected thread and frame actually
31953 changes them. In particular, invoking, directly or indirectly
31954 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
31955 will generate this notification. Changing the thread or frame from another
31956 user interface (see @ref{Interpreters}) will also generate this notification.
31958 The @var{frame} field is only present if the newly selected thread is
31959 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
31961 We suggest that in response to this notification, front ends
31962 highlight the selected thread and cause subsequent commands to apply to
31965 @item =library-loaded,...
31966 Reports that a new library file was loaded by the program. This
31967 notification has 5 fields---@var{id}, @var{target-name},
31968 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
31969 opaque identifier of the library. For remote debugging case,
31970 @var{target-name} and @var{host-name} fields give the name of the
31971 library file on the target, and on the host respectively. For native
31972 debugging, both those fields have the same value. The
31973 @var{symbols-loaded} field is emitted only for backward compatibility
31974 and should not be relied on to convey any useful information. The
31975 @var{thread-group} field, if present, specifies the id of the thread
31976 group in whose context the library was loaded. If the field is
31977 absent, it means the library was loaded in the context of all present
31978 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
31981 @item =library-unloaded,...
31982 Reports that a library was unloaded by the program. This notification
31983 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
31984 the same meaning as for the @code{=library-loaded} notification.
31985 The @var{thread-group} field, if present, specifies the id of the
31986 thread group in whose context the library was unloaded. If the field is
31987 absent, it means the library was unloaded in the context of all present
31990 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
31991 @itemx =traceframe-changed,end
31992 Reports that the trace frame was changed and its new number is
31993 @var{tfnum}. The number of the tracepoint associated with this trace
31994 frame is @var{tpnum}.
31996 @item =tsv-created,name=@var{name},initial=@var{initial}
31997 Reports that the new trace state variable @var{name} is created with
31998 initial value @var{initial}.
32000 @item =tsv-deleted,name=@var{name}
32001 @itemx =tsv-deleted
32002 Reports that the trace state variable @var{name} is deleted or all
32003 trace state variables are deleted.
32005 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
32006 Reports that the trace state variable @var{name} is modified with
32007 the initial value @var{initial}. The current value @var{current} of
32008 trace state variable is optional and is reported if the current
32009 value of trace state variable is known.
32011 @item =breakpoint-created,bkpt=@{...@}
32012 @itemx =breakpoint-modified,bkpt=@{...@}
32013 @itemx =breakpoint-deleted,id=@var{number}
32014 Reports that a breakpoint was created, modified, or deleted,
32015 respectively. Only user-visible breakpoints are reported to the MI
32018 The @var{bkpt} argument is of the same form as returned by the various
32019 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
32020 @var{number} is the ordinal number of the breakpoint.
32022 Note that if a breakpoint is emitted in the result record of a
32023 command, then it will not also be emitted in an async record.
32025 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
32026 @itemx =record-stopped,thread-group="@var{id}"
32027 Execution log recording was either started or stopped on an
32028 inferior. The @var{id} is the @value{GDBN} identifier of the thread
32029 group corresponding to the affected inferior.
32031 The @var{method} field indicates the method used to record execution. If the
32032 method in use supports multiple recording formats, @var{format} will be present
32033 and contain the currently used format. @xref{Process Record and Replay},
32034 for existing method and format values.
32036 @item =cmd-param-changed,param=@var{param},value=@var{value}
32037 Reports that a parameter of the command @code{set @var{param}} is
32038 changed to @var{value}. In the multi-word @code{set} command,
32039 the @var{param} is the whole parameter list to @code{set} command.
32040 For example, In command @code{set check type on}, @var{param}
32041 is @code{check type} and @var{value} is @code{on}.
32043 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
32044 Reports that bytes from @var{addr} to @var{data} + @var{len} were
32045 written in an inferior. The @var{id} is the identifier of the
32046 thread group corresponding to the affected inferior. The optional
32047 @code{type="code"} part is reported if the memory written to holds
32051 @node GDB/MI Breakpoint Information
32052 @subsection @sc{gdb/mi} Breakpoint Information
32054 When @value{GDBN} reports information about a breakpoint, a
32055 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
32060 The breakpoint number.
32063 The type of the breakpoint. For ordinary breakpoints this will be
32064 @samp{breakpoint}, but many values are possible.
32067 If the type of the breakpoint is @samp{catchpoint}, then this
32068 indicates the exact type of catchpoint.
32071 This is the breakpoint disposition---either @samp{del}, meaning that
32072 the breakpoint will be deleted at the next stop, or @samp{keep},
32073 meaning that the breakpoint will not be deleted.
32076 This indicates whether the breakpoint is enabled, in which case the
32077 value is @samp{y}, or disabled, in which case the value is @samp{n}.
32078 Note that this is not the same as the field @code{enable}.
32081 The address of the breakpoint. This may be a hexidecimal number,
32082 giving the address; or the string @samp{<PENDING>}, for a pending
32083 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
32084 multiple locations. This field will not be present if no address can
32085 be determined. For example, a watchpoint does not have an address.
32088 Optional field containing any flags related to the address. These flags are
32089 architecture-dependent; see @ref{Architectures} for their meaning for a
32093 If known, the function in which the breakpoint appears.
32094 If not known, this field is not present.
32097 The name of the source file which contains this function, if known.
32098 If not known, this field is not present.
32101 The full file name of the source file which contains this function, if
32102 known. If not known, this field is not present.
32105 The line number at which this breakpoint appears, if known.
32106 If not known, this field is not present.
32109 If the source file is not known, this field may be provided. If
32110 provided, this holds the address of the breakpoint, possibly followed
32114 If this breakpoint is pending, this field is present and holds the
32115 text used to set the breakpoint, as entered by the user.
32118 Where this breakpoint's condition is evaluated, either @samp{host} or
32122 If this is a thread-specific breakpoint, then this identifies the
32123 thread in which the breakpoint can trigger.
32126 If this is an inferior-specific breakpoint, this this identifies the
32127 inferior in which the breakpoint can trigger.
32130 If this breakpoint is restricted to a particular Ada task, then this
32131 field will hold the task identifier.
32134 If the breakpoint is conditional, this is the condition expression.
32137 The ignore count of the breakpoint.
32140 The enable count of the breakpoint.
32142 @item traceframe-usage
32145 @item static-tracepoint-marker-string-id
32146 For a static tracepoint, the name of the static tracepoint marker.
32149 For a masked watchpoint, this is the mask.
32152 A tracepoint's pass count.
32154 @item original-location
32155 The location of the breakpoint as originally specified by the user.
32156 This field is optional.
32159 The number of times the breakpoint has been hit.
32162 This field is only given for tracepoints. This is either @samp{y},
32163 meaning that the tracepoint is installed, or @samp{n}, meaning that it
32167 Some extra data, the exact contents of which are type-dependent.
32170 This field is present if the breakpoint has multiple locations. It is also
32171 exceptionally present if the breakpoint is enabled and has a single, disabled
32174 The value is a list of locations. The format of a location is described below.
32178 A location in a multi-location breakpoint is represented as a tuple with the
32184 The location number as a dotted pair, like @samp{1.2}. The first digit is the
32185 number of the parent breakpoint. The second digit is the number of the
32186 location within that breakpoint.
32189 There are three possible values, with the following meanings:
32192 The location is enabled.
32194 The location is disabled by the user.
32196 The location is disabled because the breakpoint condition is invalid
32201 The address of this location as an hexidecimal number.
32204 Optional field containing any flags related to the address. These flags are
32205 architecture-dependent; see @ref{Architectures} for their meaning for a
32209 If known, the function in which the location appears.
32210 If not known, this field is not present.
32213 The name of the source file which contains this location, if known.
32214 If not known, this field is not present.
32217 The full file name of the source file which contains this location, if
32218 known. If not known, this field is not present.
32221 The line number at which this location appears, if known.
32222 If not known, this field is not present.
32224 @item thread-groups
32225 The thread groups this location is in.
32229 For example, here is what the output of @code{-break-insert}
32230 (@pxref{GDB/MI Breakpoint Commands}) might be:
32233 -> -break-insert main
32234 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
32235 enabled="y",addr="0x08048564",func="main",file="myprog.c",
32236 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
32241 @node GDB/MI Frame Information
32242 @subsection @sc{gdb/mi} Frame Information
32244 Response from many MI commands includes an information about stack
32245 frame. This information is a tuple that may have the following
32250 The level of the stack frame. The innermost frame has the level of
32251 zero. This field is always present.
32254 The name of the function corresponding to the frame. This field may
32255 be absent if @value{GDBN} is unable to determine the function name.
32258 The code address for the frame. This field is always present.
32261 Optional field containing any flags related to the address. These flags are
32262 architecture-dependent; see @ref{Architectures} for their meaning for a
32266 The name of the source files that correspond to the frame's code
32267 address. This field may be absent.
32270 The source line corresponding to the frames' code address. This field
32274 The name of the binary file (either executable or shared library) the
32275 corresponds to the frame's code address. This field may be absent.
32279 @node GDB/MI Thread Information
32280 @subsection @sc{gdb/mi} Thread Information
32282 Whenever @value{GDBN} has to report an information about a thread, it
32283 uses a tuple with the following fields. The fields are always present unless
32288 The global numeric id assigned to the thread by @value{GDBN}.
32291 The target-specific string identifying the thread.
32294 Additional information about the thread provided by the target.
32295 It is supposed to be human-readable and not interpreted by the
32296 frontend. This field is optional.
32299 The name of the thread. If the user specified a name using the
32300 @code{thread name} command, then this name is given. Otherwise, if
32301 @value{GDBN} can extract the thread name from the target, then that
32302 name is given. If @value{GDBN} cannot find the thread name, then this
32306 The execution state of the thread, either @samp{stopped} or @samp{running},
32307 depending on whether the thread is presently running.
32310 The stack frame currently executing in the thread. This field is only present
32311 if the thread is stopped. Its format is documented in
32312 @ref{GDB/MI Frame Information}.
32315 The value of this field is an integer number of the processor core the
32316 thread was last seen on. This field is optional.
32319 @node GDB/MI Ada Exception Information
32320 @subsection @sc{gdb/mi} Ada Exception Information
32322 Whenever a @code{*stopped} record is emitted because the program
32323 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
32324 @value{GDBN} provides the name of the exception that was raised via
32325 the @code{exception-name} field. Also, for exceptions that were raised
32326 with an exception message, @value{GDBN} provides that message via
32327 the @code{exception-message} field.
32329 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32330 @node GDB/MI Simple Examples
32331 @section Simple Examples of @sc{gdb/mi} Interaction
32332 @cindex @sc{gdb/mi}, simple examples
32334 This subsection presents several simple examples of interaction using
32335 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
32336 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
32337 the output received from @sc{gdb/mi}.
32339 Note the line breaks shown in the examples are here only for
32340 readability, they don't appear in the real output.
32342 @subheading Setting a Breakpoint
32344 Setting a breakpoint generates synchronous output which contains detailed
32345 information of the breakpoint.
32348 -> -break-insert main
32349 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
32350 enabled="y",addr="0x08048564",func="main",file="myprog.c",
32351 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
32356 @subheading Program Execution
32358 Program execution generates asynchronous records and MI gives the
32359 reason that execution stopped.
32365 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32366 frame=@{addr="0x08048564",func="main",
32367 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
32368 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
32369 arch="i386:x86_64"@}
32374 <- *stopped,reason="exited-normally"
32378 @subheading Quitting @value{GDBN}
32380 Quitting @value{GDBN} just prints the result class @samp{^exit}.
32388 Please note that @samp{^exit} is printed immediately, but it might
32389 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
32390 performs necessary cleanups, including killing programs being debugged
32391 or disconnecting from debug hardware, so the frontend should wait till
32392 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
32393 fails to exit in reasonable time.
32395 @subheading A Bad Command
32397 Here's what happens if you pass a non-existent command:
32401 <- ^error,msg="Undefined MI command: rubbish"
32406 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32407 @node GDB/MI Command Description Format
32408 @section @sc{gdb/mi} Command Description Format
32410 The remaining sections describe blocks of commands. Each block of
32411 commands is laid out in a fashion similar to this section.
32413 @subheading Motivation
32415 The motivation for this collection of commands.
32417 @subheading Introduction
32419 A brief introduction to this collection of commands as a whole.
32421 @subheading Commands
32423 For each command in the block, the following is described:
32425 @subsubheading Synopsis
32428 -command @var{args}@dots{}
32431 @subsubheading Result
32433 @subsubheading @value{GDBN} Command
32435 The corresponding @value{GDBN} CLI command(s), if any.
32437 @subsubheading Example
32439 Example(s) formatted for readability. Some of the described commands have
32440 not been implemented yet and these are labeled N.A.@: (not available).
32443 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32444 @node GDB/MI Breakpoint Commands
32445 @section @sc{gdb/mi} Breakpoint Commands
32447 @cindex breakpoint commands for @sc{gdb/mi}
32448 @cindex @sc{gdb/mi}, breakpoint commands
32449 This section documents @sc{gdb/mi} commands for manipulating
32452 @findex -break-after
32453 @subheading The @code{-break-after} Command
32455 @subsubheading Synopsis
32458 -break-after @var{number} @var{count}
32461 The breakpoint number @var{number} is not in effect until it has been
32462 hit @var{count} times. To see how this is reflected in the output of
32463 the @samp{-break-list} command, see the description of the
32464 @samp{-break-list} command below.
32466 @subsubheading @value{GDBN} Command
32468 The corresponding @value{GDBN} command is @samp{ignore}.
32470 @subsubheading Example
32475 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
32476 enabled="y",addr="0x000100d0",func="main",file="hello.c",
32477 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
32485 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32486 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32487 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32488 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32489 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32490 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32491 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32492 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32493 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
32494 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
32499 @findex -break-catch
32500 @subheading The @code{-break-catch} Command
32503 @findex -break-commands
32504 @subheading The @code{-break-commands} Command
32506 @subsubheading Synopsis
32509 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
32512 Specifies the CLI commands that should be executed when breakpoint
32513 @var{number} is hit. The parameters @var{command1} to @var{commandN}
32514 are the commands. If no command is specified, any previously-set
32515 commands are cleared. @xref{Break Commands}. Typical use of this
32516 functionality is tracing a program, that is, printing of values of
32517 some variables whenever breakpoint is hit and then continuing.
32519 @subsubheading @value{GDBN} Command
32521 The corresponding @value{GDBN} command is @samp{commands}.
32523 @subsubheading Example
32528 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
32529 enabled="y",addr="0x000100d0",func="main",file="hello.c",
32530 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
32533 -break-commands 1 "print v" "continue"
32538 @findex -break-condition
32539 @subheading The @code{-break-condition} Command
32541 @subsubheading Synopsis
32544 -break-condition [ --force ] @var{number} [ @var{expr} ]
32547 Breakpoint @var{number} will stop the program only if the condition in
32548 @var{expr} is true. The condition becomes part of the
32549 @samp{-break-list} output (see the description of the @samp{-break-list}
32550 command below). If the @samp{--force} flag is passed, the condition
32551 is forcibly defined even when it is invalid for all locations of
32552 breakpoint @var{number}. If the @var{expr} argument is omitted,
32553 breakpoint @var{number} becomes unconditional.
32555 @subsubheading @value{GDBN} Command
32557 The corresponding @value{GDBN} command is @samp{condition}.
32559 @subsubheading Example
32563 -break-condition 1 1
32567 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32568 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32569 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32570 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32571 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32572 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32573 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32574 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32575 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
32576 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
32580 @findex -break-delete
32581 @subheading The @code{-break-delete} Command
32583 @subsubheading Synopsis
32586 -break-delete ( @var{breakpoint} )+
32589 Delete the breakpoint(s) whose number(s) are specified in the argument
32590 list. This is obviously reflected in the breakpoint list.
32592 @subsubheading @value{GDBN} Command
32594 The corresponding @value{GDBN} command is @samp{delete}.
32596 @subsubheading Example
32604 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
32605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32615 @findex -break-disable
32616 @subheading The @code{-break-disable} Command
32618 @subsubheading Synopsis
32621 -break-disable ( @var{breakpoint} )+
32624 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
32625 break list is now set to @samp{n} for the named @var{breakpoint}(s).
32627 @subsubheading @value{GDBN} Command
32629 The corresponding @value{GDBN} command is @samp{disable}.
32631 @subsubheading Example
32639 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32640 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32641 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32642 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32643 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32644 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32645 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32646 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
32647 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
32648 line="5",thread-groups=["i1"],times="0"@}]@}
32652 @findex -break-enable
32653 @subheading The @code{-break-enable} Command
32655 @subsubheading Synopsis
32658 -break-enable ( @var{breakpoint} )+
32661 Enable (previously disabled) @var{breakpoint}(s).
32663 @subsubheading @value{GDBN} Command
32665 The corresponding @value{GDBN} command is @samp{enable}.
32667 @subsubheading Example
32675 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32676 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32677 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32678 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32679 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32680 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32681 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32682 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
32683 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
32684 line="5",thread-groups=["i1"],times="0"@}]@}
32688 @findex -break-info
32689 @subheading The @code{-break-info} Command
32691 @subsubheading Synopsis
32694 -break-info @var{breakpoint}
32698 Get information about a single breakpoint.
32700 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
32701 Information}, for details on the format of each breakpoint in the
32704 @subsubheading @value{GDBN} Command
32706 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
32708 @subsubheading Example
32711 @findex -break-insert
32712 @anchor{-break-insert}
32713 @subheading The @code{-break-insert} Command
32715 @subsubheading Synopsis
32718 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
32719 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
32720 [ -p @var{thread-id} ] [ -g @var{thread-group-id} ] [ @var{locspec} ]
32724 If specified, @var{locspec}, can be one of:
32727 @item linespec location
32728 A linespec location. @xref{Linespec Locations}.
32730 @item explicit location
32731 An explicit location. @sc{gdb/mi} explicit locations are
32732 analogous to the CLI's explicit locations using the option names
32733 listed below. @xref{Explicit Locations}.
32736 @item --source @var{filename}
32737 The source file name of the location. This option requires the use
32738 of either @samp{--function} or @samp{--line}.
32740 @item --function @var{function}
32741 The name of a function or method.
32743 @item --label @var{label}
32744 The name of a label.
32746 @item --line @var{lineoffset}
32747 An absolute or relative line offset from the start of the location.
32750 @item address location
32751 An address location, *@var{address}. @xref{Address Locations}.
32755 The possible optional parameters of this command are:
32759 Insert a temporary breakpoint.
32761 Insert a hardware breakpoint.
32763 If @var{locspec} cannot be resolved (for example if it
32764 refers to unknown files or functions), create a pending
32765 breakpoint. Without this flag, @value{GDBN} will report
32766 an error, and won't create a breakpoint, if @var{locspec}
32769 Create a disabled breakpoint.
32771 Create a tracepoint. @xref{Tracepoints}. When this parameter
32772 is used together with @samp{-h}, a fast tracepoint is created.
32773 @item -c @var{condition}
32774 Make the breakpoint conditional on @var{condition}.
32775 @item --force-condition
32776 Forcibly define the breakpoint even if the condition is invalid at
32777 all of the breakpoint locations.
32778 @item -i @var{ignore-count}
32779 Initialize the @var{ignore-count}.
32780 @item -p @var{thread-id}
32781 Restrict the breakpoint to the thread with the specified global
32782 @var{thread-id}. @var{thread-id} must be a valid thread-id at the
32783 time the breakpoint is requested. Breakpoints created with a
32784 @var{thread-id} will automatically be deleted when the corresponding
32786 @item -g @var{thread-group-id}
32787 Restrict the breakpoint to the thread group with the specified
32788 @var{thread-group-id}.
32790 This option makes @value{GDBN} interpret a function name specified as
32791 a complete fully-qualified name.
32794 @subsubheading Result
32796 @xref{GDB/MI Breakpoint Information}, for details on the format of the
32797 resulting breakpoint.
32799 Note: this format is open to change.
32800 @c An out-of-band breakpoint instead of part of the result?
32802 @subsubheading @value{GDBN} Command
32804 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
32805 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
32807 @subsubheading Example
32812 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
32813 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
32816 -break-insert -t foo
32817 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
32818 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
32822 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32823 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32824 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32825 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32826 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32827 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32828 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32829 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32830 addr="0x0001072c", func="main",file="recursive2.c",
32831 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
32833 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
32834 addr="0x00010774",func="foo",file="recursive2.c",
32835 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
32840 @findex -dprintf-insert
32841 @subheading The @code{-dprintf-insert} Command
32843 @subsubheading Synopsis
32846 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
32847 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
32848 [ -p @var{thread-id} ] [ @var{locspec} ] @var{format}
32849 [ @var{argument}@dots{} ]
32853 Insert a new dynamic print breakpoint at the given location.
32854 @xref{Dynamic Printf}. @var{format} is the format to use, and any
32855 remaining arguments are passed as expressions to substitute.
32858 If supplied, @var{locspec} and @code{--qualified} may be specified
32859 the same way as for the @code{-break-insert} command.
32860 @xref{-break-insert}.
32862 The possible optional parameters of this command are:
32866 Insert a temporary breakpoint.
32868 If @var{locspec} cannot be parsed (for example, if it
32869 refers to unknown files or functions), create a pending
32870 breakpoint. Without this flag, @value{GDBN} will report
32871 an error, and won't create a breakpoint, if @var{locspec}
32874 Create a disabled breakpoint.
32875 @item -c @var{condition}
32876 Make the breakpoint conditional on @var{condition}.
32877 @item --force-condition
32878 Forcibly define the breakpoint even if the condition is invalid at
32879 all of the breakpoint locations.
32880 @item -i @var{ignore-count}
32881 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
32882 to @var{ignore-count}.
32883 @item -p @var{thread-id}
32884 Restrict the breakpoint to the thread with the specified global
32888 @subsubheading Result
32890 @xref{GDB/MI Breakpoint Information}, for details on the format of the
32891 resulting breakpoint.
32893 @c An out-of-band breakpoint instead of part of the result?
32895 @subsubheading @value{GDBN} Command
32897 The corresponding @value{GDBN} command is @samp{dprintf}.
32899 @subsubheading Example
32903 4-dprintf-insert foo "At foo entry\n"
32904 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
32905 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
32906 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
32907 times="0",script=["printf \"At foo entry\\n\"","continue"],
32908 original-location="foo"@}
32910 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
32911 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
32912 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
32913 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
32914 times="0",script=["printf \"arg=%d, g=%d\\n\", arg, g","continue"],
32915 original-location="mi-dprintf.c:26"@}
32919 @findex -break-list
32920 @subheading The @code{-break-list} Command
32922 @subsubheading Synopsis
32928 Displays the list of inserted breakpoints, showing the following fields:
32932 number of the breakpoint
32934 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
32936 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
32939 is the breakpoint enabled or no: @samp{y} or @samp{n}
32941 memory location at which the breakpoint is set
32943 logical location of the breakpoint, expressed by function name, file
32945 @item Thread-groups
32946 list of thread groups to which this breakpoint applies
32948 number of times the breakpoint has been hit
32951 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
32952 @code{body} field is an empty list.
32954 @subsubheading @value{GDBN} Command
32956 The corresponding @value{GDBN} command is @samp{info break}.
32958 @subsubheading Example
32963 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32964 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32965 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32966 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32967 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32968 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32969 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32970 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32971 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
32973 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
32974 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
32975 line="13",thread-groups=["i1"],times="0"@}]@}
32979 Here's an example of the result when there are no breakpoints:
32984 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
32985 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32986 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32987 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32988 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32989 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32990 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32995 @findex -break-passcount
32996 @subheading The @code{-break-passcount} Command
32998 @subsubheading Synopsis
33001 -break-passcount @var{tracepoint-number} @var{passcount}
33004 Set the passcount for tracepoint @var{tracepoint-number} to
33005 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
33006 is not a tracepoint, error is emitted. This corresponds to CLI
33007 command @samp{passcount}.
33009 @findex -break-watch
33010 @subheading The @code{-break-watch} Command
33012 @subsubheading Synopsis
33015 -break-watch [ -a | -r ]
33018 Create a watchpoint. With the @samp{-a} option it will create an
33019 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
33020 read from or on a write to the memory location. With the @samp{-r}
33021 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
33022 trigger only when the memory location is accessed for reading. Without
33023 either of the options, the watchpoint created is a regular watchpoint,
33024 i.e., it will trigger when the memory location is accessed for writing.
33025 @xref{Set Watchpoints, , Setting Watchpoints}.
33027 Note that @samp{-break-list} will report a single list of watchpoints and
33028 breakpoints inserted.
33030 @subsubheading @value{GDBN} Command
33032 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
33035 @subsubheading Example
33037 Setting a watchpoint on a variable in the @code{main} function:
33042 ^done,wpt=@{number="2",exp="x"@}
33047 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
33048 value=@{old="-268439212",new="55"@},
33049 frame=@{func="main",args=[],file="recursive2.c",
33050 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
33054 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
33055 the program execution twice: first for the variable changing value, then
33056 for the watchpoint going out of scope.
33061 ^done,wpt=@{number="5",exp="C"@}
33066 *stopped,reason="watchpoint-trigger",
33067 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
33068 frame=@{func="callee4",args=[],
33069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
33071 arch="i386:x86_64"@}
33076 *stopped,reason="watchpoint-scope",wpnum="5",
33077 frame=@{func="callee3",args=[@{name="strarg",
33078 value="0x11940 \"A string argument.\""@}],
33079 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33080 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
33081 arch="i386:x86_64"@}
33085 Listing breakpoints and watchpoints, at different points in the program
33086 execution. Note that once the watchpoint goes out of scope, it is
33092 ^done,wpt=@{number="2",exp="C"@}
33095 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
33096 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
33097 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
33098 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
33099 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
33100 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
33101 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
33102 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33103 addr="0x00010734",func="callee4",
33104 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33105 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
33107 bkpt=@{number="2",type="watchpoint",disp="keep",
33108 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
33113 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
33114 value=@{old="-276895068",new="3"@},
33115 frame=@{func="callee4",args=[],
33116 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33117 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
33118 arch="i386:x86_64"@}
33121 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
33122 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
33123 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
33124 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
33125 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
33126 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
33127 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
33128 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33129 addr="0x00010734",func="callee4",
33130 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33131 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
33133 bkpt=@{number="2",type="watchpoint",disp="keep",
33134 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
33138 ^done,reason="watchpoint-scope",wpnum="2",
33139 frame=@{func="callee3",args=[@{name="strarg",
33140 value="0x11940 \"A string argument.\""@}],
33141 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33142 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
33143 arch="i386:x86_64"@}
33146 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
33147 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
33148 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
33149 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
33150 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
33151 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
33152 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
33153 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33154 addr="0x00010734",func="callee4",
33155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33156 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33157 thread-groups=["i1"],times="1"@}]@}
33162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33163 @node GDB/MI Catchpoint Commands
33164 @section @sc{gdb/mi} Catchpoint Commands
33166 This section documents @sc{gdb/mi} commands for manipulating
33170 * Shared Library GDB/MI Catchpoint Commands::
33171 * Ada Exception GDB/MI Catchpoint Commands::
33172 * C++ Exception GDB/MI Catchpoint Commands::
33175 @node Shared Library GDB/MI Catchpoint Commands
33176 @subsection Shared Library @sc{gdb/mi} Catchpoints
33178 @findex -catch-load
33179 @subheading The @code{-catch-load} Command
33181 @subsubheading Synopsis
33184 -catch-load [ -t ] [ -d ] @var{regexp}
33187 Add a catchpoint for library load events. If the @samp{-t} option is used,
33188 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
33189 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
33190 in a disabled state. The @samp{regexp} argument is a regular
33191 expression used to match the name of the loaded library.
33194 @subsubheading @value{GDBN} Command
33196 The corresponding @value{GDBN} command is @samp{catch load}.
33198 @subsubheading Example
33201 -catch-load -t foo.so
33202 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
33203 what="load of library matching foo.so",catch-type="load",times="0"@}
33208 @findex -catch-unload
33209 @subheading The @code{-catch-unload} Command
33211 @subsubheading Synopsis
33214 -catch-unload [ -t ] [ -d ] @var{regexp}
33217 Add a catchpoint for library unload events. If the @samp{-t} option is
33218 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
33219 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
33220 created in a disabled state. The @samp{regexp} argument is a regular
33221 expression used to match the name of the unloaded library.
33223 @subsubheading @value{GDBN} Command
33225 The corresponding @value{GDBN} command is @samp{catch unload}.
33227 @subsubheading Example
33230 -catch-unload -d bar.so
33231 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
33232 what="load of library matching bar.so",catch-type="unload",times="0"@}
33236 @node Ada Exception GDB/MI Catchpoint Commands
33237 @subsection Ada Exception @sc{gdb/mi} Catchpoints
33239 The following @sc{gdb/mi} commands can be used to create catchpoints
33240 that stop the execution when Ada exceptions are being raised.
33242 @findex -catch-assert
33243 @subheading The @code{-catch-assert} Command
33245 @subsubheading Synopsis
33248 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
33251 Add a catchpoint for failed Ada assertions.
33253 The possible optional parameters for this command are:
33256 @item -c @var{condition}
33257 Make the catchpoint conditional on @var{condition}.
33259 Create a disabled catchpoint.
33261 Create a temporary catchpoint.
33264 @subsubheading @value{GDBN} Command
33266 The corresponding @value{GDBN} command is @samp{catch assert}.
33268 @subsubheading Example
33272 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
33273 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
33274 thread-groups=["i1"],times="0",
33275 original-location="__gnat_debug_raise_assert_failure"@}
33279 @findex -catch-exception
33280 @subheading The @code{-catch-exception} Command
33282 @subsubheading Synopsis
33285 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
33289 Add a catchpoint stopping when Ada exceptions are raised.
33290 By default, the command stops the program when any Ada exception
33291 gets raised. But it is also possible, by using some of the
33292 optional parameters described below, to create more selective
33295 The possible optional parameters for this command are:
33298 @item -c @var{condition}
33299 Make the catchpoint conditional on @var{condition}.
33301 Create a disabled catchpoint.
33302 @item -e @var{exception-name}
33303 Only stop when @var{exception-name} is raised. This option cannot
33304 be used combined with @samp{-u}.
33306 Create a temporary catchpoint.
33308 Stop only when an unhandled exception gets raised. This option
33309 cannot be used combined with @samp{-e}.
33312 @subsubheading @value{GDBN} Command
33314 The corresponding @value{GDBN} commands are @samp{catch exception}
33315 and @samp{catch exception unhandled}.
33317 @subsubheading Example
33320 -catch-exception -e Program_Error
33321 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
33322 enabled="y",addr="0x0000000000404874",
33323 what="`Program_Error' Ada exception", thread-groups=["i1"],
33324 times="0",original-location="__gnat_debug_raise_exception"@}
33328 @findex -catch-handlers
33329 @subheading The @code{-catch-handlers} Command
33331 @subsubheading Synopsis
33334 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
33338 Add a catchpoint stopping when Ada exceptions are handled.
33339 By default, the command stops the program when any Ada exception
33340 gets handled. But it is also possible, by using some of the
33341 optional parameters described below, to create more selective
33344 The possible optional parameters for this command are:
33347 @item -c @var{condition}
33348 Make the catchpoint conditional on @var{condition}.
33350 Create a disabled catchpoint.
33351 @item -e @var{exception-name}
33352 Only stop when @var{exception-name} is handled.
33354 Create a temporary catchpoint.
33357 @subsubheading @value{GDBN} Command
33359 The corresponding @value{GDBN} command is @samp{catch handlers}.
33361 @subsubheading Example
33364 -catch-handlers -e Constraint_Error
33365 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
33366 enabled="y",addr="0x0000000000402f68",
33367 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
33368 times="0",original-location="__gnat_begin_handler"@}
33372 @node C++ Exception GDB/MI Catchpoint Commands
33373 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
33375 The following @sc{gdb/mi} commands can be used to create catchpoints
33376 that stop the execution when C@t{++} exceptions are being throw, rethrown,
33379 @findex -catch-throw
33380 @subheading The @code{-catch-throw} Command
33382 @subsubheading Synopsis
33385 -catch-throw [ -t ] [ -r @var{regexp}]
33388 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
33389 given, then only exceptions whose type matches the regular expression
33392 If @samp{-t} is given, then the catchpoint is enabled only for one
33393 stop, the catchpoint is automatically deleted after stopping once for
33396 @subsubheading @value{GDBN} Command
33398 The corresponding @value{GDBN} commands are @samp{catch throw}
33399 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
33401 @subsubheading Example
33404 -catch-throw -r exception_type
33405 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
33406 what="exception throw",catch-type="throw",
33407 thread-groups=["i1"],
33408 regexp="exception_type",times="0"@}
33414 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
33415 in __cxa_throw () from /lib64/libstdc++.so.6\n"
33416 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
33417 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
33418 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
33419 thread-id="1",stopped-threads="all",core="6"
33423 @findex -catch-rethrow
33424 @subheading The @code{-catch-rethrow} Command
33426 @subsubheading Synopsis
33429 -catch-rethrow [ -t ] [ -r @var{regexp}]
33432 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
33433 then only exceptions whose type matches the regular expression will be
33436 If @samp{-t} is given, then the catchpoint is enabled only for one
33437 stop, the catchpoint is automatically deleted after the first event is
33440 @subsubheading @value{GDBN} Command
33442 The corresponding @value{GDBN} commands are @samp{catch rethrow}
33443 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
33445 @subsubheading Example
33448 -catch-rethrow -r exception_type
33449 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
33450 what="exception rethrow",catch-type="rethrow",
33451 thread-groups=["i1"],
33452 regexp="exception_type",times="0"@}
33458 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
33459 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
33460 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
33461 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
33462 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
33463 thread-id="1",stopped-threads="all",core="6"
33467 @findex -catch-catch
33468 @subheading The @code{-catch-catch} Command
33470 @subsubheading Synopsis
33473 -catch-catch [ -t ] [ -r @var{regexp}]
33476 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
33477 is given, then only exceptions whose type matches the regular
33478 expression will be caught.
33480 If @samp{-t} is given, then the catchpoint is enabled only for one
33481 stop, the catchpoint is automatically deleted after the first event is
33484 @subsubheading @value{GDBN} Command
33486 The corresponding @value{GDBN} commands are @samp{catch catch}
33487 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
33489 @subsubheading Example
33492 -catch-catch -r exception_type
33493 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
33494 what="exception catch",catch-type="catch",
33495 thread-groups=["i1"],
33496 regexp="exception_type",times="0"@}
33502 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
33503 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
33504 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
33505 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
33506 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
33507 thread-id="1",stopped-threads="all",core="6"
33511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33512 @node GDB/MI Program Context
33513 @section @sc{gdb/mi} Program Context
33515 @findex -exec-arguments
33516 @subheading The @code{-exec-arguments} Command
33519 @subsubheading Synopsis
33522 -exec-arguments @var{args}
33525 Set the inferior program arguments, to be used in the next
33528 @subsubheading @value{GDBN} Command
33530 The corresponding @value{GDBN} command is @samp{set args}.
33532 @subsubheading Example
33536 -exec-arguments -v word
33543 @findex -exec-show-arguments
33544 @subheading The @code{-exec-show-arguments} Command
33546 @subsubheading Synopsis
33549 -exec-show-arguments
33552 Print the arguments of the program.
33554 @subsubheading @value{GDBN} Command
33556 The corresponding @value{GDBN} command is @samp{show args}.
33558 @subsubheading Example
33563 @findex -environment-cd
33564 @subheading The @code{-environment-cd} Command
33566 @subsubheading Synopsis
33569 -environment-cd @var{pathdir}
33572 Set @value{GDBN}'s working directory.
33574 @subsubheading @value{GDBN} Command
33576 The corresponding @value{GDBN} command is @samp{cd}.
33578 @subsubheading Example
33582 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
33588 @findex -environment-directory
33589 @subheading The @code{-environment-directory} Command
33591 @subsubheading Synopsis
33594 -environment-directory [ -r ] [ @var{pathdir} ]+
33597 Add directories @var{pathdir} to beginning of search path for source files.
33598 If the @samp{-r} option is used, the search path is reset to the default
33599 search path. If directories @var{pathdir} are supplied in addition to the
33600 @samp{-r} option, the search path is first reset and then addition
33602 Multiple directories may be specified, separated by blanks. Specifying
33603 multiple directories in a single command
33604 results in the directories added to the beginning of the
33605 search path in the same order they were presented in the command.
33606 If blanks are needed as
33607 part of a directory name, double-quotes should be used around
33608 the name. In the command output, the path will show up separated
33609 by the system directory-separator character. The directory-separator
33610 character must not be used
33611 in any directory name.
33612 If no directories are specified, the current search path is displayed.
33614 @subsubheading @value{GDBN} Command
33616 The corresponding @value{GDBN} command is @samp{dir}.
33618 @subsubheading Example
33622 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
33623 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
33625 -environment-directory ""
33626 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
33628 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
33629 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
33631 -environment-directory -r
33632 ^done,source-path="$cdir:$cwd"
33637 @findex -environment-path
33638 @subheading The @code{-environment-path} Command
33640 @subsubheading Synopsis
33643 -environment-path [ -r ] [ @var{pathdir} ]+
33646 Add directories @var{pathdir} to beginning of search path for object files.
33647 If the @samp{-r} option is used, the search path is reset to the original
33648 search path that existed at gdb start-up. If directories @var{pathdir} are
33649 supplied in addition to the
33650 @samp{-r} option, the search path is first reset and then addition
33652 Multiple directories may be specified, separated by blanks. Specifying
33653 multiple directories in a single command
33654 results in the directories added to the beginning of the
33655 search path in the same order they were presented in the command.
33656 If blanks are needed as
33657 part of a directory name, double-quotes should be used around
33658 the name. In the command output, the path will show up separated
33659 by the system directory-separator character. The directory-separator
33660 character must not be used
33661 in any directory name.
33662 If no directories are specified, the current path is displayed.
33665 @subsubheading @value{GDBN} Command
33667 The corresponding @value{GDBN} command is @samp{path}.
33669 @subsubheading Example
33674 ^done,path="/usr/bin"
33676 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
33677 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
33679 -environment-path -r /usr/local/bin
33680 ^done,path="/usr/local/bin:/usr/bin"
33685 @findex -environment-pwd
33686 @subheading The @code{-environment-pwd} Command
33688 @subsubheading Synopsis
33694 Show the current working directory.
33696 @subsubheading @value{GDBN} Command
33698 The corresponding @value{GDBN} command is @samp{pwd}.
33700 @subsubheading Example
33705 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
33709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33710 @node GDB/MI Thread Commands
33711 @section @sc{gdb/mi} Thread Commands
33714 @findex -thread-info
33715 @subheading The @code{-thread-info} Command
33717 @subsubheading Synopsis
33720 -thread-info [ @var{thread-id} ]
33723 Reports information about either a specific thread, if the
33724 @var{thread-id} parameter is present, or about all threads.
33725 @var{thread-id} is the thread's global thread ID. When printing
33726 information about all threads, also reports the global ID of the
33729 @subsubheading @value{GDBN} Command
33731 The @samp{info thread} command prints the same information
33734 @subsubheading Result
33736 The result contains the following attributes:
33740 A list of threads. The format of the elements of the list is described in
33741 @ref{GDB/MI Thread Information}.
33743 @item current-thread-id
33744 The global id of the currently selected thread. This field is omitted if there
33745 is no selected thread (for example, when the selected inferior is not running,
33746 and therefore has no threads) or if a @var{thread-id} argument was passed to
33751 @subsubheading Example
33756 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33757 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
33758 args=[]@},state="running"@},
33759 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33760 frame=@{level="0",addr="0x0804891f",func="foo",
33761 args=[@{name="i",value="10"@}],
33762 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
33763 state="running"@}],
33764 current-thread-id="1"
33768 @findex -thread-list-ids
33769 @subheading The @code{-thread-list-ids} Command
33771 @subsubheading Synopsis
33777 Produces a list of the currently known global @value{GDBN} thread ids.
33778 At the end of the list it also prints the total number of such
33781 This command is retained for historical reasons, the
33782 @code{-thread-info} command should be used instead.
33784 @subsubheading @value{GDBN} Command
33786 Part of @samp{info threads} supplies the same information.
33788 @subsubheading Example
33793 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
33794 current-thread-id="1",number-of-threads="3"
33799 @findex -thread-select
33800 @subheading The @code{-thread-select} Command
33802 @subsubheading Synopsis
33805 -thread-select @var{thread-id}
33808 Make thread with global thread number @var{thread-id} the current
33809 thread. It prints the number of the new current thread, and the
33810 topmost frame for that thread.
33812 This command is deprecated in favor of explicitly using the
33813 @samp{--thread} option to each command.
33815 @subsubheading @value{GDBN} Command
33817 The corresponding @value{GDBN} command is @samp{thread}.
33819 @subsubheading Example
33826 *stopped,reason="end-stepping-range",thread-id="2",line="187",
33827 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
33831 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
33832 number-of-threads="3"
33835 ^done,new-thread-id="3",
33836 frame=@{level="0",func="vprintf",
33837 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
33838 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
33842 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33843 @node GDB/MI Ada Tasking Commands
33844 @section @sc{gdb/mi} Ada Tasking Commands
33846 @findex -ada-task-info
33847 @subheading The @code{-ada-task-info} Command
33849 @subsubheading Synopsis
33852 -ada-task-info [ @var{task-id} ]
33855 Reports information about either a specific Ada task, if the
33856 @var{task-id} parameter is present, or about all Ada tasks.
33858 @subsubheading @value{GDBN} Command
33860 The @samp{info tasks} command prints the same information
33861 about all Ada tasks (@pxref{Ada Tasks}).
33863 @subsubheading Result
33865 The result is a table of Ada tasks. The following columns are
33866 defined for each Ada task:
33870 This field exists only for the current thread. It has the value @samp{*}.
33873 The identifier that @value{GDBN} uses to refer to the Ada task.
33876 The identifier that the target uses to refer to the Ada task.
33879 The global thread identifier of the thread corresponding to the Ada
33882 This field should always exist, as Ada tasks are always implemented
33883 on top of a thread. But if @value{GDBN} cannot find this corresponding
33884 thread for any reason, the field is omitted.
33887 This field exists only when the task was created by another task.
33888 In this case, it provides the ID of the parent task.
33891 The base priority of the task.
33894 The current state of the task. For a detailed description of the
33895 possible states, see @ref{Ada Tasks}.
33898 The name of the task.
33902 @subsubheading Example
33906 ^done,tasks=@{nr_rows="3",nr_cols="8",
33907 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
33908 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
33909 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
33910 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
33911 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
33912 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
33913 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
33914 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
33915 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
33916 state="Child Termination Wait",name="main_task"@}]@}
33920 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33921 @node GDB/MI Program Execution
33922 @section @sc{gdb/mi} Program Execution
33924 These are the asynchronous commands which generate the out-of-band
33925 record @samp{*stopped}. Currently @value{GDBN} only really executes
33926 asynchronously with remote targets and this interaction is mimicked in
33929 @findex -exec-continue
33930 @subheading The @code{-exec-continue} Command
33932 @subsubheading Synopsis
33935 -exec-continue [--reverse] [--all|--thread-group N]
33938 Resumes the execution of the inferior program, which will continue
33939 to execute until it reaches a debugger stop event. If the
33940 @samp{--reverse} option is specified, execution resumes in reverse until
33941 it reaches a stop event. Stop events may include
33944 breakpoints or watchpoints
33946 signals or exceptions
33948 the end of the process (or its beginning under @samp{--reverse})
33950 the end or beginning of a replay log if one is being used.
33952 In all-stop mode (@pxref{All-Stop
33953 Mode}), may resume only one thread, or all threads, depending on the
33954 value of the @samp{scheduler-locking} variable. If @samp{--all} is
33955 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
33956 ignored in all-stop mode. If the @samp{--thread-group} options is
33957 specified, then all threads in that thread group are resumed.
33959 @subsubheading @value{GDBN} Command
33961 The corresponding @value{GDBN} corresponding is @samp{continue}.
33963 @subsubheading Example
33970 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
33971 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
33972 line="13",arch="i386:x86_64"@}
33976 For a @samp{breakpoint-hit} stopped reason, when the breakpoint
33977 encountered has multiple locations, the field @samp{bkptno} is
33978 followed by the field @samp{locno}.
33985 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",locno="3",frame=@{
33986 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
33987 line="13",arch="i386:x86_64"@}
33991 @findex -exec-finish
33992 @subheading The @code{-exec-finish} Command
33994 @subsubheading Synopsis
33997 -exec-finish [--reverse]
34000 Resumes the execution of the inferior program until the current
34001 function is exited. Displays the results returned by the function.
34002 If the @samp{--reverse} option is specified, resumes the reverse
34003 execution of the inferior program until the point where current
34004 function was called.
34006 @subsubheading @value{GDBN} Command
34008 The corresponding @value{GDBN} command is @samp{finish}.
34010 @subsubheading Example
34012 Function returning @code{void}.
34019 *stopped,reason="function-finished",frame=@{func="main",args=[],
34020 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
34024 Function returning other than @code{void}. The name of the internal
34025 @value{GDBN} variable storing the result is printed, together with the
34032 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
34033 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
34034 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34035 arch="i386:x86_64"@},
34036 gdb-result-var="$1",return-value="0"
34041 @findex -exec-interrupt
34042 @subheading The @code{-exec-interrupt} Command
34044 @subsubheading Synopsis
34047 -exec-interrupt [--all|--thread-group N]
34050 Interrupts the background execution of the target. Note how the token
34051 associated with the stop message is the one for the execution command
34052 that has been interrupted. The token for the interrupt itself only
34053 appears in the @samp{^done} output. If the user is trying to
34054 interrupt a non-running program, an error message will be printed.
34056 Note that when asynchronous execution is enabled, this command is
34057 asynchronous just like other execution commands. That is, first the
34058 @samp{^done} response will be printed, and the target stop will be
34059 reported after that using the @samp{*stopped} notification.
34061 In non-stop mode, only the context thread is interrupted by default.
34062 All threads (in all inferiors) will be interrupted if the
34063 @samp{--all} option is specified. If the @samp{--thread-group}
34064 option is specified, all threads in that group will be interrupted.
34066 @subsubheading @value{GDBN} Command
34068 The corresponding @value{GDBN} command is @samp{interrupt}.
34070 @subsubheading Example
34081 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
34082 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
34083 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
34088 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
34093 @subheading The @code{-exec-jump} Command
34095 @subsubheading Synopsis
34098 -exec-jump @var{locspec}
34101 Resumes execution of the inferior program at the address to
34102 which @var{locspec} resolves. @xref{Location Specifications},
34103 for a description of the different forms of @var{locspec}.
34105 @subsubheading @value{GDBN} Command
34107 The corresponding @value{GDBN} command is @samp{jump}.
34109 @subsubheading Example
34112 -exec-jump foo.c:10
34113 *running,thread-id="all"
34119 @subheading The @code{-exec-next} Command
34121 @subsubheading Synopsis
34124 -exec-next [--reverse]
34127 Resumes execution of the inferior program, stopping when the beginning
34128 of the next source line is reached.
34130 If the @samp{--reverse} option is specified, resumes reverse execution
34131 of the inferior program, stopping at the beginning of the previous
34132 source line. If you issue this command on the first line of a
34133 function, it will take you back to the caller of that function, to the
34134 source line where the function was called.
34137 @subsubheading @value{GDBN} Command
34139 The corresponding @value{GDBN} command is @samp{next}.
34141 @subsubheading Example
34147 *stopped,reason="end-stepping-range",line="8",file="hello.c"
34152 @findex -exec-next-instruction
34153 @subheading The @code{-exec-next-instruction} Command
34155 @subsubheading Synopsis
34158 -exec-next-instruction [--reverse]
34161 Executes one machine instruction. If the instruction is a function
34162 call, continues until the function returns. If the program stops at an
34163 instruction in the middle of a source line, the address will be
34166 If the @samp{--reverse} option is specified, resumes reverse execution
34167 of the inferior program, stopping at the previous instruction. If the
34168 previously executed instruction was a return from another function,
34169 it will continue to execute in reverse until the call to that function
34170 (from the current stack frame) is reached.
34172 @subsubheading @value{GDBN} Command
34174 The corresponding @value{GDBN} command is @samp{nexti}.
34176 @subsubheading Example
34180 -exec-next-instruction
34184 *stopped,reason="end-stepping-range",
34185 addr="0x000100d4",line="5",file="hello.c"
34190 @findex -exec-return
34191 @subheading The @code{-exec-return} Command
34193 @subsubheading Synopsis
34199 Makes current function return immediately. Doesn't execute the inferior.
34200 Displays the new current frame.
34202 @subsubheading @value{GDBN} Command
34204 The corresponding @value{GDBN} command is @samp{return}.
34206 @subsubheading Example
34210 200-break-insert callee4
34211 200^done,bkpt=@{number="1",addr="0x00010734",
34212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
34217 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
34218 frame=@{func="callee4",args=[],
34219 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34220 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
34221 arch="i386:x86_64"@}
34227 111^done,frame=@{level="0",func="callee3",
34228 args=[@{name="strarg",
34229 value="0x11940 \"A string argument.\""@}],
34230 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34231 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
34232 arch="i386:x86_64"@}
34238 @subheading The @code{-exec-run} Command
34240 @subsubheading Synopsis
34243 -exec-run [ --all | --thread-group N ] [ --start ]
34246 Starts execution of the inferior from the beginning. The inferior
34247 executes until either a breakpoint is encountered or the program
34248 exits. In the latter case the output will include an exit code, if
34249 the program has exited exceptionally.
34251 When neither the @samp{--all} nor the @samp{--thread-group} option
34252 is specified, the current inferior is started. If the
34253 @samp{--thread-group} option is specified, it should refer to a thread
34254 group of type @samp{process}, and that thread group will be started.
34255 If the @samp{--all} option is specified, then all inferiors will be started.
34257 Using the @samp{--start} option instructs the debugger to stop
34258 the execution at the start of the inferior's main subprogram,
34259 following the same behavior as the @code{start} command
34260 (@pxref{Starting}).
34262 @subsubheading @value{GDBN} Command
34264 The corresponding @value{GDBN} command is @samp{run}.
34266 @subsubheading Examples
34271 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
34276 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
34277 frame=@{func="main",args=[],file="recursive2.c",
34278 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
34283 Program exited normally:
34291 *stopped,reason="exited-normally"
34296 Program exited exceptionally:
34304 *stopped,reason="exited",exit-code="01"
34308 Another way the program can terminate is if it receives a signal such as
34309 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
34313 *stopped,reason="exited-signalled",signal-name="SIGINT",
34314 signal-meaning="Interrupt"
34318 @c @subheading -exec-signal
34322 @subheading The @code{-exec-step} Command
34324 @subsubheading Synopsis
34327 -exec-step [--reverse]
34330 Resumes execution of the inferior program, stopping when the beginning
34331 of the next source line is reached, if the next source line is not a
34332 function call. If it is, stop at the first instruction of the called
34333 function. If the @samp{--reverse} option is specified, resumes reverse
34334 execution of the inferior program, stopping at the beginning of the
34335 previously executed source line.
34337 @subsubheading @value{GDBN} Command
34339 The corresponding @value{GDBN} command is @samp{step}.
34341 @subsubheading Example
34343 Stepping into a function:
34349 *stopped,reason="end-stepping-range",
34350 frame=@{func="foo",args=[@{name="a",value="10"@},
34351 @{name="b",value="0"@}],file="recursive2.c",
34352 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
34362 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
34367 @findex -exec-step-instruction
34368 @subheading The @code{-exec-step-instruction} Command
34370 @subsubheading Synopsis
34373 -exec-step-instruction [--reverse]
34376 Resumes the inferior which executes one machine instruction. If the
34377 @samp{--reverse} option is specified, resumes reverse execution of the
34378 inferior program, stopping at the previously executed instruction.
34379 The output, once @value{GDBN} has stopped, will vary depending on
34380 whether we have stopped in the middle of a source line or not. In the
34381 former case, the address at which the program stopped will be printed
34384 @subsubheading @value{GDBN} Command
34386 The corresponding @value{GDBN} command is @samp{stepi}.
34388 @subsubheading Example
34392 -exec-step-instruction
34396 *stopped,reason="end-stepping-range",
34397 frame=@{func="foo",args=[],file="try.c",
34398 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
34400 -exec-step-instruction
34404 *stopped,reason="end-stepping-range",
34405 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
34406 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
34411 @findex -exec-until
34412 @subheading The @code{-exec-until} Command
34414 @subsubheading Synopsis
34417 -exec-until [ @var{locspec} ]
34420 Executes the inferior until it reaches the address to which
34421 @var{locspec} resolves. If there is no argument, the inferior
34422 executes until it reaches a source line greater than the current one.
34423 The reason for stopping in this case will be @samp{location-reached}.
34425 @subsubheading @value{GDBN} Command
34427 The corresponding @value{GDBN} command is @samp{until}.
34429 @subsubheading Example
34433 -exec-until recursive2.c:6
34437 *stopped,reason="location-reached",frame=@{func="main",args=[],
34438 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
34439 arch="i386:x86_64"@}
34444 @subheading -file-clear
34445 Is this going away????
34448 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34449 @node GDB/MI Stack Manipulation
34450 @section @sc{gdb/mi} Stack Manipulation Commands
34452 @findex -enable-frame-filters
34453 @subheading The @code{-enable-frame-filters} Command
34456 -enable-frame-filters
34459 @value{GDBN} allows Python-based frame filters to affect the output of
34460 the MI commands relating to stack traces. As there is no way to
34461 implement this in a fully backward-compatible way, a front end must
34462 request that this functionality be enabled.
34464 Once enabled, this feature cannot be disabled.
34466 Note that if Python support has not been compiled into @value{GDBN},
34467 this command will still succeed (and do nothing).
34469 @findex -stack-info-frame
34470 @subheading The @code{-stack-info-frame} Command
34472 @subsubheading Synopsis
34478 Get info on the selected frame.
34480 @subsubheading @value{GDBN} Command
34482 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
34483 (without arguments).
34485 @subsubheading Example
34490 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
34491 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34492 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
34493 arch="i386:x86_64"@}
34497 @findex -stack-info-depth
34498 @subheading The @code{-stack-info-depth} Command
34500 @subsubheading Synopsis
34503 -stack-info-depth [ @var{max-depth} ]
34506 Return the depth of the stack. If the integer argument @var{max-depth}
34507 is specified, do not count beyond @var{max-depth} frames.
34509 @subsubheading @value{GDBN} Command
34511 There's no equivalent @value{GDBN} command.
34513 @subsubheading Example
34515 For a stack with frame levels 0 through 11:
34522 -stack-info-depth 4
34525 -stack-info-depth 12
34528 -stack-info-depth 11
34531 -stack-info-depth 13
34536 @anchor{-stack-list-arguments}
34537 @findex -stack-list-arguments
34538 @subheading The @code{-stack-list-arguments} Command
34540 @subsubheading Synopsis
34543 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
34544 [ @var{low-frame} @var{high-frame} ]
34547 Display a list of the arguments for the frames between @var{low-frame}
34548 and @var{high-frame} (inclusive). If @var{low-frame} and
34549 @var{high-frame} are not provided, list the arguments for the whole
34550 call stack. If the two arguments are equal, show the single frame
34551 at the corresponding level. It is an error if @var{low-frame} is
34552 larger than the actual number of frames. On the other hand,
34553 @var{high-frame} may be larger than the actual number of frames, in
34554 which case only existing frames will be returned.
34556 If @var{print-values} is 0 or @code{--no-values}, print only the names of
34557 the variables; if it is 1 or @code{--all-values}, print also their
34558 values; and if it is 2 or @code{--simple-values}, print the name,
34559 type and value for simple data types, and the name and type for arrays,
34560 structures and unions. If the option @code{--no-frame-filters} is
34561 supplied, then Python frame filters will not be executed.
34563 If the @code{--skip-unavailable} option is specified, arguments that
34564 are not available are not listed. Partially available arguments
34565 are still displayed, however.
34567 Use of this command to obtain arguments in a single frame is
34568 deprecated in favor of the @samp{-stack-list-variables} command.
34570 @subsubheading @value{GDBN} Command
34572 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
34573 @samp{gdb_get_args} command which partially overlaps with the
34574 functionality of @samp{-stack-list-arguments}.
34576 @subsubheading Example
34583 frame=@{level="0",addr="0x00010734",func="callee4",
34584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
34586 arch="i386:x86_64"@},
34587 frame=@{level="1",addr="0x0001076c",func="callee3",
34588 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34589 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
34590 arch="i386:x86_64"@},
34591 frame=@{level="2",addr="0x0001078c",func="callee2",
34592 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34593 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
34594 arch="i386:x86_64"@},
34595 frame=@{level="3",addr="0x000107b4",func="callee1",
34596 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34597 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
34598 arch="i386:x86_64"@},
34599 frame=@{level="4",addr="0x000107e0",func="main",
34600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
34601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
34602 arch="i386:x86_64"@}]
34604 -stack-list-arguments 0
34607 frame=@{level="0",args=[]@},
34608 frame=@{level="1",args=[name="strarg"]@},
34609 frame=@{level="2",args=[name="intarg",name="strarg"]@},
34610 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
34611 frame=@{level="4",args=[]@}]
34613 -stack-list-arguments 1
34616 frame=@{level="0",args=[]@},
34618 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
34619 frame=@{level="2",args=[
34620 @{name="intarg",value="2"@},
34621 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
34622 @{frame=@{level="3",args=[
34623 @{name="intarg",value="2"@},
34624 @{name="strarg",value="0x11940 \"A string argument.\""@},
34625 @{name="fltarg",value="3.5"@}]@},
34626 frame=@{level="4",args=[]@}]
34628 -stack-list-arguments 0 2 2
34629 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
34631 -stack-list-arguments 1 2 2
34632 ^done,stack-args=[frame=@{level="2",
34633 args=[@{name="intarg",value="2"@},
34634 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
34638 @c @subheading -stack-list-exception-handlers
34641 @anchor{-stack-list-frames}
34642 @findex -stack-list-frames
34643 @subheading The @code{-stack-list-frames} Command
34645 @subsubheading Synopsis
34648 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
34651 List the frames currently on the stack. For each frame it displays the
34656 The frame number, 0 being the topmost frame, i.e., the innermost function.
34658 The @code{$pc} value for that frame.
34662 File name of the source file where the function lives.
34663 @item @var{fullname}
34664 The full file name of the source file where the function lives.
34666 Line number corresponding to the @code{$pc}.
34668 The shared library where this function is defined. This is only given
34669 if the frame's function is not known.
34671 Frame's architecture.
34674 If invoked without arguments, this command prints a backtrace for the
34675 whole stack. If given two integer arguments, it shows the frames whose
34676 levels are between the two arguments (inclusive). If the two arguments
34677 are equal, it shows the single frame at the corresponding level. It is
34678 an error if @var{low-frame} is larger than the actual number of
34679 frames. On the other hand, @var{high-frame} may be larger than the
34680 actual number of frames, in which case only existing frames will be
34681 returned. If the option @code{--no-frame-filters} is supplied, then
34682 Python frame filters will not be executed.
34684 @subsubheading @value{GDBN} Command
34686 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
34688 @subsubheading Example
34690 Full stack backtrace:
34696 [frame=@{level="0",addr="0x0001076c",func="foo",
34697 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
34698 arch="i386:x86_64"@},
34699 frame=@{level="1",addr="0x000107a4",func="foo",
34700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34701 arch="i386:x86_64"@},
34702 frame=@{level="2",addr="0x000107a4",func="foo",
34703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34704 arch="i386:x86_64"@},
34705 frame=@{level="3",addr="0x000107a4",func="foo",
34706 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34707 arch="i386:x86_64"@},
34708 frame=@{level="4",addr="0x000107a4",func="foo",
34709 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34710 arch="i386:x86_64"@},
34711 frame=@{level="5",addr="0x000107a4",func="foo",
34712 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34713 arch="i386:x86_64"@},
34714 frame=@{level="6",addr="0x000107a4",func="foo",
34715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34716 arch="i386:x86_64"@},
34717 frame=@{level="7",addr="0x000107a4",func="foo",
34718 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34719 arch="i386:x86_64"@},
34720 frame=@{level="8",addr="0x000107a4",func="foo",
34721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34722 arch="i386:x86_64"@},
34723 frame=@{level="9",addr="0x000107a4",func="foo",
34724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34725 arch="i386:x86_64"@},
34726 frame=@{level="10",addr="0x000107a4",func="foo",
34727 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34728 arch="i386:x86_64"@},
34729 frame=@{level="11",addr="0x00010738",func="main",
34730 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
34731 arch="i386:x86_64"@}]
34735 Show frames between @var{low_frame} and @var{high_frame}:
34739 -stack-list-frames 3 5
34741 [frame=@{level="3",addr="0x000107a4",func="foo",
34742 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34743 arch="i386:x86_64"@},
34744 frame=@{level="4",addr="0x000107a4",func="foo",
34745 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34746 arch="i386:x86_64"@},
34747 frame=@{level="5",addr="0x000107a4",func="foo",
34748 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34749 arch="i386:x86_64"@}]
34753 Show a single frame:
34757 -stack-list-frames 3 3
34759 [frame=@{level="3",addr="0x000107a4",func="foo",
34760 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
34761 arch="i386:x86_64"@}]
34766 @findex -stack-list-locals
34767 @anchor{-stack-list-locals}
34768 @subheading The @code{-stack-list-locals} Command
34770 @subsubheading Synopsis
34773 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
34776 Display the local variable names for the selected frame. If
34777 @var{print-values} is 0 or @code{--no-values}, print only the names of
34778 the variables; if it is 1 or @code{--all-values}, print also their
34779 values; and if it is 2 or @code{--simple-values}, print the name,
34780 type and value for simple data types, and the name and type for arrays,
34781 structures and unions. In this last case, a frontend can immediately
34782 display the value of simple data types and create variable objects for
34783 other data types when the user wishes to explore their values in
34784 more detail. If the option @code{--no-frame-filters} is supplied, then
34785 Python frame filters will not be executed.
34787 If the @code{--skip-unavailable} option is specified, local variables
34788 that are not available are not listed. Partially available local
34789 variables are still displayed, however.
34791 This command is deprecated in favor of the
34792 @samp{-stack-list-variables} command.
34794 @subsubheading @value{GDBN} Command
34796 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
34798 @subsubheading Example
34802 -stack-list-locals 0
34803 ^done,locals=[name="A",name="B",name="C"]
34805 -stack-list-locals --all-values
34806 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
34807 @{name="C",value="@{1, 2, 3@}"@}]
34808 -stack-list-locals --simple-values
34809 ^done,locals=[@{name="A",type="int",value="1"@},
34810 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
34814 @anchor{-stack-list-variables}
34815 @findex -stack-list-variables
34816 @subheading The @code{-stack-list-variables} Command
34818 @subsubheading Synopsis
34821 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
34824 Display the names of local variables and function arguments for the selected frame. If
34825 @var{print-values} is 0 or @code{--no-values}, print only the names of
34826 the variables; if it is 1 or @code{--all-values}, print also their
34827 values; and if it is 2 or @code{--simple-values}, print the name,
34828 type and value for simple data types, and the name and type for arrays,
34829 structures and unions. If the option @code{--no-frame-filters} is
34830 supplied, then Python frame filters will not be executed.
34832 If the @code{--skip-unavailable} option is specified, local variables
34833 and arguments that are not available are not listed. Partially
34834 available arguments and local variables are still displayed, however.
34836 @subsubheading Example
34840 -stack-list-variables --thread 1 --frame 0 --all-values
34841 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
34846 @findex -stack-select-frame
34847 @subheading The @code{-stack-select-frame} Command
34849 @subsubheading Synopsis
34852 -stack-select-frame @var{framenum}
34855 Change the selected frame. Select a different frame @var{framenum} on
34858 This command in deprecated in favor of passing the @samp{--frame}
34859 option to every command.
34861 @subsubheading @value{GDBN} Command
34863 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
34864 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
34866 @subsubheading Example
34870 -stack-select-frame 2
34875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34876 @node GDB/MI Variable Objects
34877 @section @sc{gdb/mi} Variable Objects
34881 @subheading Motivation for Variable Objects in @sc{gdb/mi}
34883 For the implementation of a variable debugger window (locals, watched
34884 expressions, etc.), we are proposing the adaptation of the existing code
34885 used by @code{Insight}.
34887 The two main reasons for that are:
34891 It has been proven in practice (it is already on its second generation).
34894 It will shorten development time (needless to say how important it is
34898 The original interface was designed to be used by Tcl code, so it was
34899 slightly changed so it could be used through @sc{gdb/mi}. This section
34900 describes the @sc{gdb/mi} operations that will be available and gives some
34901 hints about their use.
34903 @emph{Note}: In addition to the set of operations described here, we
34904 expect the @sc{gui} implementation of a variable window to require, at
34905 least, the following operations:
34908 @item @code{-gdb-show} @code{output-radix}
34909 @item @code{-stack-list-arguments}
34910 @item @code{-stack-list-locals}
34911 @item @code{-stack-select-frame}
34916 @subheading Introduction to Variable Objects
34918 @cindex variable objects in @sc{gdb/mi}
34920 Variable objects are "object-oriented" MI interface for examining and
34921 changing values of expressions. Unlike some other MI interfaces that
34922 work with expressions, variable objects are specifically designed for
34923 simple and efficient presentation in the frontend. A variable object
34924 is identified by string name. When a variable object is created, the
34925 frontend specifies the expression for that variable object. The
34926 expression can be a simple variable, or it can be an arbitrary complex
34927 expression, and can even involve CPU registers. After creating a
34928 variable object, the frontend can invoke other variable object
34929 operations---for example to obtain or change the value of a variable
34930 object, or to change display format.
34932 Variable objects have hierarchical tree structure. Any variable object
34933 that corresponds to a composite type, such as structure in C, has
34934 a number of child variable objects, for example corresponding to each
34935 element of a structure. A child variable object can itself have
34936 children, recursively. Recursion ends when we reach
34937 leaf variable objects, which always have built-in types. Child variable
34938 objects are created only by explicit request, so if a frontend
34939 is not interested in the children of a particular variable object, no
34940 child will be created.
34942 For a leaf variable object it is possible to obtain its value as a
34943 string, or set the value from a string. String value can be also
34944 obtained for a non-leaf variable object, but it's generally a string
34945 that only indicates the type of the object, and does not list its
34946 contents. Assignment to a non-leaf variable object is not allowed.
34948 A frontend does not need to read the values of all variable objects each time
34949 the program stops. Instead, MI provides an update command that lists all
34950 variable objects whose values has changed since the last update
34951 operation. This considerably reduces the amount of data that must
34952 be transferred to the frontend. As noted above, children variable
34953 objects are created on demand, and only leaf variable objects have a
34954 real value. As result, gdb will read target memory only for leaf
34955 variables that frontend has created.
34957 The automatic update is not always desirable. For example, a frontend
34958 might want to keep a value of some expression for future reference,
34959 and never update it. For another example, fetching memory is
34960 relatively slow for embedded targets, so a frontend might want
34961 to disable automatic update for the variables that are either not
34962 visible on the screen, or ``closed''. This is possible using so
34963 called ``frozen variable objects''. Such variable objects are never
34964 implicitly updated.
34966 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
34967 fixed variable object, the expression is parsed when the variable
34968 object is created, including associating identifiers to specific
34969 variables. The meaning of expression never changes. For a floating
34970 variable object the values of variables whose names appear in the
34971 expressions are re-evaluated every time in the context of the current
34972 frame. Consider this example:
34977 struct work_state state;
34984 If a fixed variable object for the @code{state} variable is created in
34985 this function, and we enter the recursive call, the variable
34986 object will report the value of @code{state} in the top-level
34987 @code{do_work} invocation. On the other hand, a floating variable
34988 object will report the value of @code{state} in the current frame.
34990 If an expression specified when creating a fixed variable object
34991 refers to a local variable, the variable object becomes bound to the
34992 thread and frame in which the variable object is created. When such
34993 variable object is updated, @value{GDBN} makes sure that the
34994 thread/frame combination the variable object is bound to still exists,
34995 and re-evaluates the variable object in context of that thread/frame.
34997 The following is the complete set of @sc{gdb/mi} operations defined to
34998 access this functionality:
35000 @multitable @columnfractions .4 .6
35001 @item @strong{Operation}
35002 @tab @strong{Description}
35004 @item @code{-enable-pretty-printing}
35005 @tab enable Python-based pretty-printing
35006 @item @code{-var-create}
35007 @tab create a variable object
35008 @item @code{-var-delete}
35009 @tab delete the variable object and/or its children
35010 @item @code{-var-set-format}
35011 @tab set the display format of this variable
35012 @item @code{-var-show-format}
35013 @tab show the display format of this variable
35014 @item @code{-var-info-num-children}
35015 @tab tells how many children this object has
35016 @item @code{-var-list-children}
35017 @tab return a list of the object's children
35018 @item @code{-var-info-type}
35019 @tab show the type of this variable object
35020 @item @code{-var-info-expression}
35021 @tab print parent-relative expression that this variable object represents
35022 @item @code{-var-info-path-expression}
35023 @tab print full expression that this variable object represents
35024 @item @code{-var-show-attributes}
35025 @tab is this variable editable? does it exist here?
35026 @item @code{-var-evaluate-expression}
35027 @tab get the value of this variable
35028 @item @code{-var-assign}
35029 @tab set the value of this variable
35030 @item @code{-var-update}
35031 @tab update the variable and its children
35032 @item @code{-var-set-frozen}
35033 @tab set frozenness attribute
35034 @item @code{-var-set-update-range}
35035 @tab set range of children to display on update
35038 In the next subsection we describe each operation in detail and suggest
35039 how it can be used.
35041 @subheading Description And Use of Operations on Variable Objects
35043 @findex -enable-pretty-printing
35044 @subheading The @code{-enable-pretty-printing} Command
35047 -enable-pretty-printing
35050 @value{GDBN} allows Python-based visualizers to affect the output of the
35051 MI variable object commands. However, because there was no way to
35052 implement this in a fully backward-compatible way, a front end must
35053 request that this functionality be enabled.
35055 Once enabled, this feature cannot be disabled.
35057 Note that if Python support has not been compiled into @value{GDBN},
35058 this command will still succeed (and do nothing).
35060 @findex -var-create
35061 @subheading The @code{-var-create} Command
35063 @subsubheading Synopsis
35066 -var-create @{@var{name} | "-"@}
35067 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
35070 This operation creates a variable object, which allows the monitoring of
35071 a variable, the result of an expression, a memory cell or a CPU
35074 The @var{name} parameter is the string by which the object can be
35075 referenced. It must be unique. If @samp{-} is specified, the varobj
35076 system will generate a string ``varNNNNNN'' automatically. It will be
35077 unique provided that one does not specify @var{name} of that format.
35078 The command fails if a duplicate name is found.
35080 The frame under which the expression should be evaluated can be
35081 specified by @var{frame-addr}. A @samp{*} indicates that the current
35082 frame should be used. A @samp{@@} indicates that a floating variable
35083 object must be created.
35085 @var{expression} is any expression valid on the current language set (must not
35086 begin with a @samp{*}), or one of the following:
35090 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
35093 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
35096 @samp{$@var{regname}} --- a CPU register name
35099 @cindex dynamic varobj
35100 A varobj's contents may be provided by a Python-based pretty-printer. In this
35101 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
35102 have slightly different semantics in some cases. If the
35103 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
35104 will never create a dynamic varobj. This ensures backward
35105 compatibility for existing clients.
35107 @subsubheading Result
35109 This operation returns attributes of the newly-created varobj. These
35114 The name of the varobj.
35117 The number of children of the varobj. This number is not necessarily
35118 reliable for a dynamic varobj. Instead, you must examine the
35119 @samp{has_more} attribute.
35122 The varobj's scalar value. For a varobj whose type is some sort of
35123 aggregate (e.g., a @code{struct}), this value will not be interesting.
35124 For a dynamic varobj, this value comes directly from the Python
35125 pretty-printer object's @code{to_string} method.
35128 The varobj's type. This is a string representation of the type, as
35129 would be printed by the @value{GDBN} CLI. If @samp{print object}
35130 (@pxref{Print Settings, set print object}) is set to @code{on}, the
35131 @emph{actual} (derived) type of the object is shown rather than the
35132 @emph{declared} one.
35135 If a variable object is bound to a specific thread, then this is the
35136 thread's global identifier.
35139 For a dynamic varobj, this indicates whether there appear to be any
35140 children available. For a non-dynamic varobj, this will be 0.
35143 This attribute will be present and have the value @samp{1} if the
35144 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
35145 then this attribute will not be present.
35148 A dynamic varobj can supply a display hint to the front end. The
35149 value comes directly from the Python pretty-printer object's
35150 @code{display_hint} method. @xref{Pretty Printing API}.
35153 Typical output will look like this:
35156 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
35157 has_more="@var{has_more}"
35161 @findex -var-delete
35162 @subheading The @code{-var-delete} Command
35164 @subsubheading Synopsis
35167 -var-delete [ -c ] @var{name}
35170 Deletes a previously created variable object and all of its children.
35171 With the @samp{-c} option, just deletes the children.
35173 Returns an error if the object @var{name} is not found.
35176 @findex -var-set-format
35177 @subheading The @code{-var-set-format} Command
35179 @subsubheading Synopsis
35182 -var-set-format @var{name} @var{format-spec}
35185 Sets the output format for the value of the object @var{name} to be
35188 @anchor{-var-set-format}
35189 The syntax for the @var{format-spec} is as follows:
35192 @var{format-spec} @expansion{}
35193 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
35196 The natural format is the default format choosen automatically
35197 based on the variable type (like decimal for an @code{int}, hex
35198 for pointers, etc.).
35200 The zero-hexadecimal format has a representation similar to hexadecimal
35201 but with padding zeroes to the left of the value. For example, a 32-bit
35202 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
35203 zero-hexadecimal format.
35205 For a variable with children, the format is set only on the
35206 variable itself, and the children are not affected.
35208 @findex -var-show-format
35209 @subheading The @code{-var-show-format} Command
35211 @subsubheading Synopsis
35214 -var-show-format @var{name}
35217 Returns the format used to display the value of the object @var{name}.
35220 @var{format} @expansion{}
35225 @findex -var-info-num-children
35226 @subheading The @code{-var-info-num-children} Command
35228 @subsubheading Synopsis
35231 -var-info-num-children @var{name}
35234 Returns the number of children of a variable object @var{name}:
35240 Note that this number is not completely reliable for a dynamic varobj.
35241 It will return the current number of children, but more children may
35245 @findex -var-list-children
35246 @subheading The @code{-var-list-children} Command
35248 @subsubheading Synopsis
35251 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
35253 @anchor{-var-list-children}
35255 Return a list of the children of the specified variable object and
35256 create variable objects for them, if they do not already exist. With
35257 a single argument or if @var{print-values} has a value of 0 or
35258 @code{--no-values}, print only the names of the variables; if
35259 @var{print-values} is 1 or @code{--all-values}, also print their
35260 values; and if it is 2 or @code{--simple-values} print the name and
35261 value for simple data types and just the name for arrays, structures
35264 @var{from} and @var{to}, if specified, indicate the range of children
35265 to report. If @var{from} or @var{to} is less than zero, the range is
35266 reset and all children will be reported. Otherwise, children starting
35267 at @var{from} (zero-based) and up to and excluding @var{to} will be
35270 If a child range is requested, it will only affect the current call to
35271 @code{-var-list-children}, but not future calls to @code{-var-update}.
35272 For this, you must instead use @code{-var-set-update-range}. The
35273 intent of this approach is to enable a front end to implement any
35274 update approach it likes; for example, scrolling a view may cause the
35275 front end to request more children with @code{-var-list-children}, and
35276 then the front end could call @code{-var-set-update-range} with a
35277 different range to ensure that future updates are restricted to just
35280 For each child the following results are returned:
35285 Name of the variable object created for this child.
35288 The expression to be shown to the user by the front end to designate this child.
35289 For example this may be the name of a structure member.
35291 For a dynamic varobj, this value cannot be used to form an
35292 expression. There is no way to do this at all with a dynamic varobj.
35294 For C/C@t{++} structures there are several pseudo children returned to
35295 designate access qualifiers. For these pseudo children @var{exp} is
35296 @samp{public}, @samp{private}, or @samp{protected}. In this case the
35297 type and value are not present.
35299 A dynamic varobj will not report the access qualifying
35300 pseudo-children, regardless of the language. This information is not
35301 available at all with a dynamic varobj.
35304 Number of children this child has. For a dynamic varobj, this will be
35308 The type of the child. If @samp{print object}
35309 (@pxref{Print Settings, set print object}) is set to @code{on}, the
35310 @emph{actual} (derived) type of the object is shown rather than the
35311 @emph{declared} one.
35314 If values were requested, this is the value.
35317 If this variable object is associated with a thread, this is the
35318 thread's global thread id. Otherwise this result is not present.
35321 If the variable object is frozen, this variable will be present with a value of 1.
35324 A dynamic varobj can supply a display hint to the front end. The
35325 value comes directly from the Python pretty-printer object's
35326 @code{display_hint} method. @xref{Pretty Printing API}.
35329 This attribute will be present and have the value @samp{1} if the
35330 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
35331 then this attribute will not be present.
35335 The result may have its own attributes:
35339 A dynamic varobj can supply a display hint to the front end. The
35340 value comes directly from the Python pretty-printer object's
35341 @code{display_hint} method. @xref{Pretty Printing API}.
35344 This is an integer attribute which is nonzero if there are children
35345 remaining after the end of the selected range.
35348 @subsubheading Example
35352 -var-list-children n
35353 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
35354 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
35356 -var-list-children --all-values n
35357 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
35358 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
35362 @findex -var-info-type
35363 @subheading The @code{-var-info-type} Command
35365 @subsubheading Synopsis
35368 -var-info-type @var{name}
35371 Returns the type of the specified variable @var{name}. The type is
35372 returned as a string in the same format as it is output by the
35376 type=@var{typename}
35380 @findex -var-info-expression
35381 @subheading The @code{-var-info-expression} Command
35383 @subsubheading Synopsis
35386 -var-info-expression @var{name}
35389 Returns a string that is suitable for presenting this
35390 variable object in user interface. The string is generally
35391 not valid expression in the current language, and cannot be evaluated.
35393 For example, if @code{a} is an array, and variable object
35394 @code{A} was created for @code{a}, then we'll get this output:
35397 (gdb) -var-info-expression A.1
35398 ^done,lang="C",exp="1"
35402 Here, the value of @code{lang} is the language name, which can be
35403 found in @ref{Supported Languages}.
35405 Note that the output of the @code{-var-list-children} command also
35406 includes those expressions, so the @code{-var-info-expression} command
35409 @findex -var-info-path-expression
35410 @subheading The @code{-var-info-path-expression} Command
35412 @subsubheading Synopsis
35415 -var-info-path-expression @var{name}
35418 Returns an expression that can be evaluated in the current
35419 context and will yield the same value that a variable object has.
35420 Compare this with the @code{-var-info-expression} command, which
35421 result can be used only for UI presentation. Typical use of
35422 the @code{-var-info-path-expression} command is creating a
35423 watchpoint from a variable object.
35425 This command is currently not valid for children of a dynamic varobj,
35426 and will give an error when invoked on one.
35428 For example, suppose @code{C} is a C@t{++} class, derived from class
35429 @code{Base}, and that the @code{Base} class has a member called
35430 @code{m_size}. Assume a variable @code{c} is has the type of
35431 @code{C} and a variable object @code{C} was created for variable
35432 @code{c}. Then, we'll get this output:
35434 (gdb) -var-info-path-expression C.Base.public.m_size
35435 ^done,path_expr=((Base)c).m_size)
35438 @findex -var-show-attributes
35439 @subheading The @code{-var-show-attributes} Command
35441 @subsubheading Synopsis
35444 -var-show-attributes @var{name}
35447 List attributes of the specified variable object @var{name}:
35450 status=@var{attr} [ ( ,@var{attr} )* ]
35454 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
35456 @findex -var-evaluate-expression
35457 @subheading The @code{-var-evaluate-expression} Command
35459 @subsubheading Synopsis
35462 -var-evaluate-expression [-f @var{format-spec}] @var{name}
35465 Evaluates the expression that is represented by the specified variable
35466 object and returns its value as a string. The format of the string
35467 can be specified with the @samp{-f} option. The possible values of
35468 this option are the same as for @code{-var-set-format}
35469 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
35470 the current display format will be used. The current display format
35471 can be changed using the @code{-var-set-format} command.
35477 Note that one must invoke @code{-var-list-children} for a variable
35478 before the value of a child variable can be evaluated.
35480 @findex -var-assign
35481 @subheading The @code{-var-assign} Command
35483 @subsubheading Synopsis
35486 -var-assign @var{name} @var{expression}
35489 Assigns the value of @var{expression} to the variable object specified
35490 by @var{name}. The object must be @samp{editable}. If the variable's
35491 value is altered by the assign, the variable will show up in any
35492 subsequent @code{-var-update} list.
35494 @subsubheading Example
35502 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
35506 @findex -var-update
35507 @subheading The @code{-var-update} Command
35509 @subsubheading Synopsis
35512 -var-update [@var{print-values}] @{@var{name} | "*"@}
35515 Reevaluate the expressions corresponding to the variable object
35516 @var{name} and all its direct and indirect children, and return the
35517 list of variable objects whose values have changed; @var{name} must
35518 be a root variable object. Here, ``changed'' means that the result of
35519 @code{-var-evaluate-expression} before and after the
35520 @code{-var-update} is different. If @samp{*} is used as the variable
35521 object names, all existing variable objects are updated, except
35522 for frozen ones (@pxref{-var-set-frozen}). The option
35523 @var{print-values} determines whether both names and values, or just
35524 names are printed. The possible values of this option are the same
35525 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
35526 recommended to use the @samp{--all-values} option, to reduce the
35527 number of MI commands needed on each program stop.
35529 With the @samp{*} parameter, if a variable object is bound to a
35530 currently running thread, it will not be updated, without any
35533 If @code{-var-set-update-range} was previously used on a varobj, then
35534 only the selected range of children will be reported.
35536 @code{-var-update} reports all the changed varobjs in a tuple named
35539 Each item in the change list is itself a tuple holding:
35543 The name of the varobj.
35546 If values were requested for this update, then this field will be
35547 present and will hold the value of the varobj.
35550 @anchor{-var-update}
35551 This field is a string which may take one of three values:
35555 The variable object's current value is valid.
35558 The variable object does not currently hold a valid value but it may
35559 hold one in the future if its associated expression comes back into
35563 The variable object no longer holds a valid value.
35564 This can occur when the executable file being debugged has changed,
35565 either through recompilation or by using the @value{GDBN} @code{file}
35566 command. The front end should normally choose to delete these variable
35570 In the future new values may be added to this list so the front should
35571 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{gdb/mi} Development and Front Ends}.
35574 This is only present if the varobj is still valid. If the type
35575 changed, then this will be the string @samp{true}; otherwise it will
35578 When a varobj's type changes, its children are also likely to have
35579 become incorrect. Therefore, the varobj's children are automatically
35580 deleted when this attribute is @samp{true}. Also, the varobj's update
35581 range, when set using the @code{-var-set-update-range} command, is
35585 If the varobj's type changed, then this field will be present and will
35588 @item new_num_children
35589 For a dynamic varobj, if the number of children changed, or if the
35590 type changed, this will be the new number of children.
35592 The @samp{numchild} field in other varobj responses is generally not
35593 valid for a dynamic varobj -- it will show the number of children that
35594 @value{GDBN} knows about, but because dynamic varobjs lazily
35595 instantiate their children, this will not reflect the number of
35596 children which may be available.
35598 The @samp{new_num_children} attribute only reports changes to the
35599 number of children known by @value{GDBN}. This is the only way to
35600 detect whether an update has removed children (which necessarily can
35601 only happen at the end of the update range).
35604 The display hint, if any.
35607 This is an integer value, which will be 1 if there are more children
35608 available outside the varobj's update range.
35611 This attribute will be present and have the value @samp{1} if the
35612 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
35613 then this attribute will not be present.
35616 If new children were added to a dynamic varobj within the selected
35617 update range (as set by @code{-var-set-update-range}), then they will
35618 be listed in this attribute.
35621 @subsubheading Example
35628 -var-update --all-values var1
35629 ^done,changelist=[@{name="var1",value="3",in_scope="true",
35630 type_changed="false"@}]
35634 @findex -var-set-frozen
35635 @anchor{-var-set-frozen}
35636 @subheading The @code{-var-set-frozen} Command
35638 @subsubheading Synopsis
35641 -var-set-frozen @var{name} @var{flag}
35644 Set the frozenness flag on the variable object @var{name}. The
35645 @var{flag} parameter should be either @samp{1} to make the variable
35646 frozen or @samp{0} to make it unfrozen. If a variable object is
35647 frozen, then neither itself, nor any of its children, are
35648 implicitly updated by @code{-var-update} of
35649 a parent variable or by @code{-var-update *}. Only
35650 @code{-var-update} of the variable itself will update its value and
35651 values of its children. After a variable object is unfrozen, it is
35652 implicitly updated by all subsequent @code{-var-update} operations.
35653 Unfreezing a variable does not update it, only subsequent
35654 @code{-var-update} does.
35656 @subsubheading Example
35660 -var-set-frozen V 1
35665 @findex -var-set-update-range
35666 @anchor{-var-set-update-range}
35667 @subheading The @code{-var-set-update-range} command
35669 @subsubheading Synopsis
35672 -var-set-update-range @var{name} @var{from} @var{to}
35675 Set the range of children to be returned by future invocations of
35676 @code{-var-update}.
35678 @var{from} and @var{to} indicate the range of children to report. If
35679 @var{from} or @var{to} is less than zero, the range is reset and all
35680 children will be reported. Otherwise, children starting at @var{from}
35681 (zero-based) and up to and excluding @var{to} will be reported.
35683 @subsubheading Example
35687 -var-set-update-range V 1 2
35691 @findex -var-set-visualizer
35692 @anchor{-var-set-visualizer}
35693 @subheading The @code{-var-set-visualizer} command
35695 @subsubheading Synopsis
35698 -var-set-visualizer @var{name} @var{visualizer}
35701 Set a visualizer for the variable object @var{name}.
35703 @var{visualizer} is the visualizer to use. The special value
35704 @samp{None} means to disable any visualizer in use.
35706 If not @samp{None}, @var{visualizer} must be a Python expression.
35707 This expression must evaluate to a callable object which accepts a
35708 single argument. @value{GDBN} will call this object with the value of
35709 the varobj @var{name} as an argument (this is done so that the same
35710 Python pretty-printing code can be used for both the CLI and MI).
35711 When called, this object must return an object which conforms to the
35712 pretty-printing interface (@pxref{Pretty Printing API}).
35714 The pre-defined function @code{gdb.default_visualizer} may be used to
35715 select a visualizer by following the built-in process
35716 (@pxref{Selecting Pretty-Printers}). This is done automatically when
35717 a varobj is created, and so ordinarily is not needed.
35719 This feature is only available if Python support is enabled. The MI
35720 command @code{-list-features} (@pxref{GDB/MI Support Commands})
35721 can be used to check this.
35723 @subsubheading Example
35725 Resetting the visualizer:
35729 -var-set-visualizer V None
35733 Reselecting the default (type-based) visualizer:
35737 -var-set-visualizer V gdb.default_visualizer
35741 Suppose @code{SomeClass} is a visualizer class. A lambda expression
35742 can be used to instantiate this class for a varobj:
35746 -var-set-visualizer V "lambda val: SomeClass()"
35750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35751 @node GDB/MI Data Manipulation
35752 @section @sc{gdb/mi} Data Manipulation
35754 @cindex data manipulation, in @sc{gdb/mi}
35755 @cindex @sc{gdb/mi}, data manipulation
35756 This section describes the @sc{gdb/mi} commands that manipulate data:
35757 examine memory and registers, evaluate expressions, etc.
35759 For details about what an addressable memory unit is,
35760 @pxref{addressable memory unit}.
35762 @c REMOVED FROM THE INTERFACE.
35763 @c @subheading -data-assign
35764 @c Change the value of a program variable. Plenty of side effects.
35765 @c @subsubheading GDB Command
35767 @c @subsubheading Example
35770 @findex -data-disassemble
35771 @subheading The @code{-data-disassemble} Command
35773 @subsubheading Synopsis
35777 ( -s @var{start-addr} -e @var{end-addr}
35779 | -f @var{filename} -l @var{linenum} [ -n @var{lines} ] )
35780 [ --opcodes @var{opcodes-mode} ]
35789 @item @var{start-addr}
35790 is the beginning address (or @code{$pc})
35791 @item @var{end-addr}
35794 is an address anywhere within (or the name of) the function to
35795 disassemble. If an address is specified, the whole function
35796 surrounding that address will be disassembled. If a name is
35797 specified, the whole function with that name will be disassembled.
35798 @item @var{filename}
35799 is the name of the file to disassemble
35800 @item @var{linenum}
35801 is the line number to disassemble around
35803 is the number of disassembly lines to be produced. If it is -1,
35804 the whole function will be disassembled, in case no @var{end-addr} is
35805 specified. If @var{end-addr} is specified as a non-zero value, and
35806 @var{lines} is lower than the number of disassembly lines between
35807 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
35808 displayed; if @var{lines} is higher than the number of lines between
35809 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
35811 @item @var{opcodes-mode}
35812 can only be used with @var{mode} 0, and should be one of the following:
35815 no opcode information will be included in the result.
35818 opcodes will be included in the result, the opcodes will be formatted
35819 as for @kbd{disassemble /b}.
35822 opcodes will be included in the result, the opcodes will be formatted
35823 as for @kbd{disassemble /r}.
35826 the use of @var{mode} is deprecated in favour of using the
35827 @code{--opcodes} and @code{--source} options. When no @var{mode} is
35828 given, @var{mode} 0 will be assumed. However, the @var{mode} is still
35829 available for backward compatibility. The @var{mode} should be one of:
35832 @emph{disassembly only}, this is the default mode if no mode is
35836 @emph{mixed source and disassembly (deprecated)}, it is not possible
35837 to recreate this mode using @code{--opcodes} and @code{--source}
35841 @emph{disassembly with raw opcodes}, this mode is equivalent to using
35842 @var{mode} 0 and passing @code{--opcodes bytes} to the command.
35845 @emph{mixed source and disassembly with raw opcodes (deprecated)}, it
35846 is not possible to recreate this mode using @code{--opcodes} and
35847 @code{--source} options.
35850 @emph{mixed source and disassembly}, this mode is equivalent to using
35851 @var{mode} 0 and passing @code{--source} to the command.
35854 @emph{mixed source and disassembly with raw opcodes}, this mode is
35855 equivalent to using @var{mode} 0 and passing @code{--opcodes bytes}
35856 and @code{--source} to the command.
35858 Modes 1 and 3 are deprecated. The output is ``source centric''
35859 which hasn't proved useful in practice.
35860 @xref{Machine Code}, for a discussion of the difference between
35861 @code{/m} and @code{/s} output of the @code{disassemble} command.
35864 The @code{--source} can only be used with @var{mode} 0. Passing this
35865 option will include the source code in the disassembly result as if
35866 @var{mode} 4 or 5 had been used.
35868 @subsubheading Result
35870 The result of the @code{-data-disassemble} command will be a list named
35871 @samp{asm_insns}, the contents of this list depend on the options used
35872 with the @code{-data-disassemble} command.
35874 For modes 0 and 2, and when the @code{--source} option is not used, the
35875 @samp{asm_insns} list contains tuples with the following fields:
35879 The address at which this instruction was disassembled.
35882 The name of the function this instruction is within.
35885 The decimal offset in bytes from the start of @samp{func-name}.
35888 The text disassembly for this @samp{address}.
35891 This field is only present for modes 2, 3 and 5, or when the
35892 @code{--opcodes} option @samp{bytes} or @samp{display} is used. This
35893 contains the raw opcode bytes for the @samp{inst} field.
35895 When the @samp{--opcodes} option is not passed to
35896 @code{-data-disassemble}, or the @samp{bytes} value is passed to
35897 @samp{--opcodes}, then the bytes are formatted as a series of single
35898 bytes, in hex, in ascending address order, with a single space between
35899 each byte. This format is equivalent to the @samp{/b} option being
35900 used with the @kbd{disassemble} command
35901 (@pxref{disassemble,,@kbd{disassemble}}).
35903 When @samp{--opcodes} is passed the value @samp{display} then the bytes
35904 are formatted in the natural instruction display order. This means
35905 multiple bytes can be grouped together, and the bytes might be
35906 byte-swapped. This format is equivalent to the @samp{/r} option being
35907 used with the @kbd{disassemble} command.
35910 For modes 1, 3, 4 and 5, or when the @code{--source} option is used, the
35911 @samp{asm_insns} list contains tuples named @samp{src_and_asm_line},
35912 each of which has the following fields:
35916 The line number within @samp{file}.
35919 The file name from the compilation unit. This might be an absolute
35920 file name or a relative file name depending on the compile command
35924 Absolute file name of @samp{file}. It is converted to a canonical form
35925 using the source file search path
35926 (@pxref{Source Path, ,Specifying Source Directories})
35927 and after resolving all the symbolic links.
35929 If the source file is not found this field will contain the path as
35930 present in the debug information.
35932 @item line_asm_insn
35933 This is a list of tuples containing the disassembly for @samp{line} in
35934 @samp{file}. The fields of each tuple are the same as for
35935 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
35936 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
35941 Note that whatever included in the @samp{inst} field, is not
35942 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
35945 @subsubheading @value{GDBN} Command
35947 The corresponding @value{GDBN} command is @samp{disassemble}.
35949 @subsubheading Example
35951 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
35955 -data-disassemble -s $pc -e "$pc + 20" -- 0
35958 @{address="0x000107c0",func-name="main",offset="4",
35959 inst="mov 2, %o0"@},
35960 @{address="0x000107c4",func-name="main",offset="8",
35961 inst="sethi %hi(0x11800), %o2"@},
35962 @{address="0x000107c8",func-name="main",offset="12",
35963 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
35964 @{address="0x000107cc",func-name="main",offset="16",
35965 inst="sethi %hi(0x11800), %o2"@},
35966 @{address="0x000107d0",func-name="main",offset="20",
35967 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
35971 Disassemble the whole @code{main} function. Line 32 is part of
35975 -data-disassemble -f basics.c -l 32 -- 0
35977 @{address="0x000107bc",func-name="main",offset="0",
35978 inst="save %sp, -112, %sp"@},
35979 @{address="0x000107c0",func-name="main",offset="4",
35980 inst="mov 2, %o0"@},
35981 @{address="0x000107c4",func-name="main",offset="8",
35982 inst="sethi %hi(0x11800), %o2"@},
35984 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
35985 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
35989 Disassemble 3 instructions from the start of @code{main}:
35993 -data-disassemble -f basics.c -l 32 -n 3 -- 0
35995 @{address="0x000107bc",func-name="main",offset="0",
35996 inst="save %sp, -112, %sp"@},
35997 @{address="0x000107c0",func-name="main",offset="4",
35998 inst="mov 2, %o0"@},
35999 @{address="0x000107c4",func-name="main",offset="8",
36000 inst="sethi %hi(0x11800), %o2"@}]
36004 Disassemble 3 instructions from the start of @code{main} in mixed mode:
36008 -data-disassemble -f basics.c -l 32 -n 3 -- 1
36010 src_and_asm_line=@{line="31",
36011 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
36012 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
36013 line_asm_insn=[@{address="0x000107bc",
36014 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
36015 src_and_asm_line=@{line="32",
36016 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
36017 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
36018 line_asm_insn=[@{address="0x000107c0",
36019 func-name="main",offset="4",inst="mov 2, %o0"@},
36020 @{address="0x000107c4",func-name="main",offset="8",
36021 inst="sethi %hi(0x11800), %o2"@}]@}]
36026 @findex -data-evaluate-expression
36027 @subheading The @code{-data-evaluate-expression} Command
36029 @subsubheading Synopsis
36032 -data-evaluate-expression @var{expr}
36035 Evaluate @var{expr} as an expression. The expression could contain an
36036 inferior function call. The function call will execute synchronously.
36037 If the expression contains spaces, it must be enclosed in double quotes.
36039 @subsubheading @value{GDBN} Command
36041 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
36042 @samp{call}. In @code{gdbtk} only, there's a corresponding
36043 @samp{gdb_eval} command.
36045 @subsubheading Example
36047 In the following example, the numbers that precede the commands are the
36048 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
36049 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
36053 211-data-evaluate-expression A
36056 311-data-evaluate-expression &A
36057 311^done,value="0xefffeb7c"
36059 411-data-evaluate-expression A+3
36062 511-data-evaluate-expression "A + 3"
36068 @findex -data-list-changed-registers
36069 @subheading The @code{-data-list-changed-registers} Command
36071 @subsubheading Synopsis
36074 -data-list-changed-registers
36077 Display a list of the registers that have changed.
36079 @subsubheading @value{GDBN} Command
36081 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
36082 has the corresponding command @samp{gdb_changed_register_list}.
36084 @subsubheading Example
36086 On a PPC MBX board:
36094 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
36095 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
36096 line="5",arch="powerpc"@}
36098 -data-list-changed-registers
36099 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
36100 "10","11","13","14","15","16","17","18","19","20","21","22","23",
36101 "24","25","26","27","28","30","31","64","65","66","67","69"]
36106 @findex -data-list-register-names
36107 @subheading The @code{-data-list-register-names} Command
36109 @subsubheading Synopsis
36112 -data-list-register-names [ ( @var{regno} )+ ]
36115 Show a list of register names for the current target. If no arguments
36116 are given, it shows a list of the names of all the registers. If
36117 integer numbers are given as arguments, it will print a list of the
36118 names of the registers corresponding to the arguments. To ensure
36119 consistency between a register name and its number, the output list may
36120 include empty register names.
36122 @subsubheading @value{GDBN} Command
36124 @value{GDBN} does not have a command which corresponds to
36125 @samp{-data-list-register-names}. In @code{gdbtk} there is a
36126 corresponding command @samp{gdb_regnames}.
36128 @subsubheading Example
36130 For the PPC MBX board:
36133 -data-list-register-names
36134 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
36135 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
36136 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
36137 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
36138 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
36139 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
36140 "", "pc","ps","cr","lr","ctr","xer"]
36142 -data-list-register-names 1 2 3
36143 ^done,register-names=["r1","r2","r3"]
36147 @findex -data-list-register-values
36148 @subheading The @code{-data-list-register-values} Command
36150 @subsubheading Synopsis
36153 -data-list-register-values
36154 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
36157 Display the registers' contents. The format according to which the
36158 registers' contents are to be returned is given by @var{fmt}, followed
36159 by an optional list of numbers specifying the registers to display. A
36160 missing list of numbers indicates that the contents of all the
36161 registers must be returned. The @code{--skip-unavailable} option
36162 indicates that only the available registers are to be returned.
36164 Allowed formats for @var{fmt} are:
36181 @subsubheading @value{GDBN} Command
36183 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
36184 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
36186 @subsubheading Example
36188 For a PPC MBX board (note: line breaks are for readability only, they
36189 don't appear in the actual output):
36193 -data-list-register-values r 64 65
36194 ^done,register-values=[@{number="64",value="0xfe00a300"@},
36195 @{number="65",value="0x00029002"@}]
36197 -data-list-register-values x
36198 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
36199 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
36200 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
36201 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
36202 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
36203 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
36204 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
36205 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
36206 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
36207 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
36208 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
36209 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
36210 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
36211 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
36212 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
36213 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
36214 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
36215 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
36216 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
36217 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
36218 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
36219 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
36220 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
36221 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
36222 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
36223 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
36224 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
36225 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
36226 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
36227 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
36228 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
36229 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
36230 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
36231 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
36232 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
36233 @{number="69",value="0x20002b03"@}]
36238 @findex -data-read-memory
36239 @subheading The @code{-data-read-memory} Command
36241 This command is deprecated, use @code{-data-read-memory-bytes} instead.
36243 @subsubheading Synopsis
36246 -data-read-memory [ -o @var{byte-offset} ]
36247 @var{address} @var{word-format} @var{word-size}
36248 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
36255 @item @var{address}
36256 An expression specifying the address of the first memory word to be
36257 read. Complex expressions containing embedded white space should be
36258 quoted using the C convention.
36260 @item @var{word-format}
36261 The format to be used to print the memory words. The notation is the
36262 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
36265 @item @var{word-size}
36266 The size of each memory word in bytes.
36268 @item @var{nr-rows}
36269 The number of rows in the output table.
36271 @item @var{nr-cols}
36272 The number of columns in the output table.
36275 If present, indicates that each row should include an @sc{ascii} dump. The
36276 value of @var{aschar} is used as a padding character when a byte is not a
36277 member of the printable @sc{ascii} character set (printable @sc{ascii}
36278 characters are those whose code is between 32 and 126, inclusively).
36280 @item @var{byte-offset}
36281 An offset to add to the @var{address} before fetching memory.
36284 This command displays memory contents as a table of @var{nr-rows} by
36285 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
36286 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
36287 (returned as @samp{total-bytes}). Should less than the requested number
36288 of bytes be returned by the target, the missing words are identified
36289 using @samp{N/A}. The number of bytes read from the target is returned
36290 in @samp{nr-bytes} and the starting address used to read memory in
36293 The address of the next/previous row or page is available in
36294 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
36297 @subsubheading @value{GDBN} Command
36299 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
36300 @samp{gdb_get_mem} memory read command.
36302 @subsubheading Example
36304 Read six bytes of memory starting at @code{bytes+6} but then offset by
36305 @code{-6} bytes. Format as three rows of two columns. One byte per
36306 word. Display each word in hex.
36310 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
36311 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
36312 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
36313 prev-page="0x0000138a",memory=[
36314 @{addr="0x00001390",data=["0x00","0x01"]@},
36315 @{addr="0x00001392",data=["0x02","0x03"]@},
36316 @{addr="0x00001394",data=["0x04","0x05"]@}]
36320 Read two bytes of memory starting at address @code{shorts + 64} and
36321 display as a single word formatted in decimal.
36325 5-data-read-memory shorts+64 d 2 1 1
36326 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
36327 next-row="0x00001512",prev-row="0x0000150e",
36328 next-page="0x00001512",prev-page="0x0000150e",memory=[
36329 @{addr="0x00001510",data=["128"]@}]
36333 Read thirty two bytes of memory starting at @code{bytes+16} and format
36334 as eight rows of four columns. Include a string encoding with @samp{x}
36335 used as the non-printable character.
36339 4-data-read-memory bytes+16 x 1 8 4 x
36340 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
36341 next-row="0x000013c0",prev-row="0x0000139c",
36342 next-page="0x000013c0",prev-page="0x00001380",memory=[
36343 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
36344 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
36345 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
36346 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
36347 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
36348 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
36349 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
36350 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
36354 @findex -data-read-memory-bytes
36355 @subheading The @code{-data-read-memory-bytes} Command
36357 @subsubheading Synopsis
36360 -data-read-memory-bytes [ -o @var{offset} ]
36361 @var{address} @var{count}
36368 @item @var{address}
36369 An expression specifying the address of the first addressable memory unit
36370 to be read. Complex expressions containing embedded white space should be
36371 quoted using the C convention.
36374 The number of addressable memory units to read. This should be an integer
36378 The offset relative to @var{address} at which to start reading. This
36379 should be an integer literal. This option is provided so that a frontend
36380 is not required to first evaluate address and then perform address
36381 arithmetics itself.
36385 This command attempts to read all accessible memory regions in the
36386 specified range. First, all regions marked as unreadable in the memory
36387 map (if one is defined) will be skipped. @xref{Memory Region
36388 Attributes}. Second, @value{GDBN} will attempt to read the remaining
36389 regions. For each one, if reading full region results in an errors,
36390 @value{GDBN} will try to read a subset of the region.
36392 In general, every single memory unit in the region may be readable or not,
36393 and the only way to read every readable unit is to try a read at
36394 every address, which is not practical. Therefore, @value{GDBN} will
36395 attempt to read all accessible memory units at either beginning or the end
36396 of the region, using a binary division scheme. This heuristic works
36397 well for reading across a memory map boundary. Note that if a region
36398 has a readable range that is neither at the beginning or the end,
36399 @value{GDBN} will not read it.
36401 The result record (@pxref{GDB/MI Result Records}) that is output of
36402 the command includes a field named @samp{memory} whose content is a
36403 list of tuples. Each tuple represent a successfully read memory block
36404 and has the following fields:
36408 The start address of the memory block, as hexadecimal literal.
36411 The end address of the memory block, as hexadecimal literal.
36414 The offset of the memory block, as hexadecimal literal, relative to
36415 the start address passed to @code{-data-read-memory-bytes}.
36418 The contents of the memory block, in hex.
36424 @subsubheading @value{GDBN} Command
36426 The corresponding @value{GDBN} command is @samp{x}.
36428 @subsubheading Example
36432 -data-read-memory-bytes &a 10
36433 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
36435 contents="01000000020000000300"@}]
36440 @findex -data-write-memory-bytes
36441 @subheading The @code{-data-write-memory-bytes} Command
36443 @subsubheading Synopsis
36446 -data-write-memory-bytes @var{address} @var{contents}
36447 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
36454 @item @var{address}
36455 An expression specifying the address of the first addressable memory unit
36456 to be written. Complex expressions containing embedded white space should
36457 be quoted using the C convention.
36459 @item @var{contents}
36460 The hex-encoded data to write. It is an error if @var{contents} does
36461 not represent an integral number of addressable memory units.
36464 Optional argument indicating the number of addressable memory units to be
36465 written. If @var{count} is greater than @var{contents}' length,
36466 @value{GDBN} will repeatedly write @var{contents} until it fills
36467 @var{count} memory units.
36471 @subsubheading @value{GDBN} Command
36473 There's no corresponding @value{GDBN} command.
36475 @subsubheading Example
36479 -data-write-memory-bytes &a "aabbccdd"
36486 -data-write-memory-bytes &a "aabbccdd" 16e
36491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36492 @node GDB/MI Tracepoint Commands
36493 @section @sc{gdb/mi} Tracepoint Commands
36495 The commands defined in this section implement MI support for
36496 tracepoints. For detailed introduction, see @ref{Tracepoints}.
36498 @findex -trace-find
36499 @subheading The @code{-trace-find} Command
36501 @subsubheading Synopsis
36504 -trace-find @var{mode} [@var{parameters}@dots{}]
36507 Find a trace frame using criteria defined by @var{mode} and
36508 @var{parameters}. The following table lists permissible
36509 modes and their parameters. For details of operation, see @ref{tfind}.
36514 No parameters are required. Stops examining trace frames.
36517 An integer is required as parameter. Selects tracepoint frame with
36520 @item tracepoint-number
36521 An integer is required as parameter. Finds next
36522 trace frame that corresponds to tracepoint with the specified number.
36525 An address is required as parameter. Finds
36526 next trace frame that corresponds to any tracepoint at the specified
36529 @item pc-inside-range
36530 Two addresses are required as parameters. Finds next trace
36531 frame that corresponds to a tracepoint at an address inside the
36532 specified range. Both bounds are considered to be inside the range.
36534 @item pc-outside-range
36535 Two addresses are required as parameters. Finds
36536 next trace frame that corresponds to a tracepoint at an address outside
36537 the specified range. Both bounds are considered to be inside the range.
36540 Location specification is required as parameter. @xref{Location Specifications}.
36541 Finds next trace frame that corresponds to a tracepoint at
36542 the specified location.
36546 If @samp{none} was passed as @var{mode}, the response does not
36547 have fields. Otherwise, the response may have the following fields:
36551 This field has either @samp{0} or @samp{1} as the value, depending
36552 on whether a matching tracepoint was found.
36555 The index of the found traceframe. This field is present iff
36556 the @samp{found} field has value of @samp{1}.
36559 The index of the found tracepoint. This field is present iff
36560 the @samp{found} field has value of @samp{1}.
36563 The information about the frame corresponding to the found trace
36564 frame. This field is present only if a trace frame was found.
36565 @xref{GDB/MI Frame Information}, for description of this field.
36569 @subsubheading @value{GDBN} Command
36571 The corresponding @value{GDBN} command is @samp{tfind}.
36573 @findex -trace-define-variable
36574 @subheading The @code{-trace-define-variable} Command
36576 @subsubheading Synopsis
36579 -trace-define-variable @var{name} [ @var{value} ]
36582 Create trace variable @var{name} if it does not exist. If
36583 @var{value} is specified, sets the initial value of the specified
36584 trace variable to that value. Note that the @var{name} should start
36585 with the @samp{$} character.
36587 @subsubheading @value{GDBN} Command
36589 The corresponding @value{GDBN} command is @samp{tvariable}.
36591 @findex -trace-frame-collected
36592 @subheading The @code{-trace-frame-collected} Command
36594 @subsubheading Synopsis
36597 -trace-frame-collected
36598 [--var-print-values @var{var_pval}]
36599 [--comp-print-values @var{comp_pval}]
36600 [--registers-format @var{regformat}]
36601 [--memory-contents]
36604 This command returns the set of collected objects, register names,
36605 trace state variable names, memory ranges and computed expressions
36606 that have been collected at a particular trace frame. The optional
36607 parameters to the command affect the output format in different ways.
36608 See the output description table below for more details.
36610 The reported names can be used in the normal manner to create
36611 varobjs and inspect the objects themselves. The items returned by
36612 this command are categorized so that it is clear which is a variable,
36613 which is a register, which is a trace state variable, which is a
36614 memory range and which is a computed expression.
36616 For instance, if the actions were
36618 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
36619 collect *(int*)0xaf02bef0@@40
36623 the object collected in its entirety would be @code{myVar}. The
36624 object @code{myArray} would be partially collected, because only the
36625 element at index @code{myIndex} would be collected. The remaining
36626 objects would be computed expressions.
36628 An example output would be:
36632 -trace-frame-collected
36634 explicit-variables=[@{name="myVar",value="1"@}],
36635 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
36636 @{name="myObj.field",value="0"@},
36637 @{name="myPtr->field",value="1"@},
36638 @{name="myCount + 2",value="3"@},
36639 @{name="$tvar1 + 1",value="43970027"@}],
36640 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
36641 @{number="1",value="0x0"@},
36642 @{number="2",value="0x4"@},
36644 @{number="125",value="0x0"@}],
36645 tvars=[@{name="$tvar1",current="43970026"@}],
36646 memory=[@{address="0x0000000000602264",length="4"@},
36647 @{address="0x0000000000615bc0",length="4"@}]
36654 @item explicit-variables
36655 The set of objects that have been collected in their entirety (as
36656 opposed to collecting just a few elements of an array or a few struct
36657 members). For each object, its name and value are printed.
36658 The @code{--var-print-values} option affects how or whether the value
36659 field is output. If @var{var_pval} is 0, then print only the names;
36660 if it is 1, print also their values; and if it is 2, print the name,
36661 type and value for simple data types, and the name and type for
36662 arrays, structures and unions.
36664 @item computed-expressions
36665 The set of computed expressions that have been collected at the
36666 current trace frame. The @code{--comp-print-values} option affects
36667 this set like the @code{--var-print-values} option affects the
36668 @code{explicit-variables} set. See above.
36671 The registers that have been collected at the current trace frame.
36672 For each register collected, the name and current value are returned.
36673 The value is formatted according to the @code{--registers-format}
36674 option. See the @command{-data-list-register-values} command for a
36675 list of the allowed formats. The default is @samp{x}.
36678 The trace state variables that have been collected at the current
36679 trace frame. For each trace state variable collected, the name and
36680 current value are returned.
36683 The set of memory ranges that have been collected at the current trace
36684 frame. Its content is a list of tuples. Each tuple represents a
36685 collected memory range and has the following fields:
36689 The start address of the memory range, as hexadecimal literal.
36692 The length of the memory range, as decimal literal.
36695 The contents of the memory block, in hex. This field is only present
36696 if the @code{--memory-contents} option is specified.
36702 @subsubheading @value{GDBN} Command
36704 There is no corresponding @value{GDBN} command.
36706 @subsubheading Example
36708 @findex -trace-list-variables
36709 @subheading The @code{-trace-list-variables} Command
36711 @subsubheading Synopsis
36714 -trace-list-variables
36717 Return a table of all defined trace variables. Each element of the
36718 table has the following fields:
36722 The name of the trace variable. This field is always present.
36725 The initial value. This is a 64-bit signed integer. This
36726 field is always present.
36729 The value the trace variable has at the moment. This is a 64-bit
36730 signed integer. This field is absent iff current value is
36731 not defined, for example if the trace was never run, or is
36736 @subsubheading @value{GDBN} Command
36738 The corresponding @value{GDBN} command is @samp{tvariables}.
36740 @subsubheading Example
36744 -trace-list-variables
36745 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
36746 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
36747 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
36748 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
36749 body=[variable=@{name="$trace_timestamp",initial="0"@}
36750 variable=@{name="$foo",initial="10",current="15"@}]@}
36754 @findex -trace-save
36755 @subheading The @code{-trace-save} Command
36757 @subsubheading Synopsis
36760 -trace-save [ -r ] [ -ctf ] @var{filename}
36763 Saves the collected trace data to @var{filename}. Without the
36764 @samp{-r} option, the data is downloaded from the target and saved
36765 in a local file. With the @samp{-r} option the target is asked
36766 to perform the save.
36768 By default, this command will save the trace in the tfile format. You can
36769 supply the optional @samp{-ctf} argument to save it the CTF format. See
36770 @ref{Trace Files} for more information about CTF.
36772 @subsubheading @value{GDBN} Command
36774 The corresponding @value{GDBN} command is @samp{tsave}.
36777 @findex -trace-start
36778 @subheading The @code{-trace-start} Command
36780 @subsubheading Synopsis
36786 Starts a tracing experiment. The result of this command does not
36789 @subsubheading @value{GDBN} Command
36791 The corresponding @value{GDBN} command is @samp{tstart}.
36793 @findex -trace-status
36794 @subheading The @code{-trace-status} Command
36796 @subsubheading Synopsis
36802 Obtains the status of a tracing experiment. The result may include
36803 the following fields:
36808 May have a value of either @samp{0}, when no tracing operations are
36809 supported, @samp{1}, when all tracing operations are supported, or
36810 @samp{file} when examining trace file. In the latter case, examining
36811 of trace frame is possible but new tracing experiement cannot be
36812 started. This field is always present.
36815 May have a value of either @samp{0} or @samp{1} depending on whether
36816 tracing experiement is in progress on target. This field is present
36817 if @samp{supported} field is not @samp{0}.
36820 Report the reason why the tracing was stopped last time. This field
36821 may be absent iff tracing was never stopped on target yet. The
36822 value of @samp{request} means the tracing was stopped as result of
36823 the @code{-trace-stop} command. The value of @samp{overflow} means
36824 the tracing buffer is full. The value of @samp{disconnection} means
36825 tracing was automatically stopped when @value{GDBN} has disconnected.
36826 The value of @samp{passcount} means tracing was stopped when a
36827 tracepoint was passed a maximal number of times for that tracepoint.
36828 This field is present if @samp{supported} field is not @samp{0}.
36830 @item stopping-tracepoint
36831 The number of tracepoint whose passcount as exceeded. This field is
36832 present iff the @samp{stop-reason} field has the value of
36836 @itemx frames-created
36837 The @samp{frames} field is a count of the total number of trace frames
36838 in the trace buffer, while @samp{frames-created} is the total created
36839 during the run, including ones that were discarded, such as when a
36840 circular trace buffer filled up. Both fields are optional.
36844 These fields tell the current size of the tracing buffer and the
36845 remaining space. These fields are optional.
36848 The value of the circular trace buffer flag. @code{1} means that the
36849 trace buffer is circular and old trace frames will be discarded if
36850 necessary to make room, @code{0} means that the trace buffer is linear
36854 The value of the disconnected tracing flag. @code{1} means that
36855 tracing will continue after @value{GDBN} disconnects, @code{0} means
36856 that the trace run will stop.
36859 The filename of the trace file being examined. This field is
36860 optional, and only present when examining a trace file.
36864 @subsubheading @value{GDBN} Command
36866 The corresponding @value{GDBN} command is @samp{tstatus}.
36868 @findex -trace-stop
36869 @subheading The @code{-trace-stop} Command
36871 @subsubheading Synopsis
36877 Stops a tracing experiment. The result of this command has the same
36878 fields as @code{-trace-status}, except that the @samp{supported} and
36879 @samp{running} fields are not output.
36881 @subsubheading @value{GDBN} Command
36883 The corresponding @value{GDBN} command is @samp{tstop}.
36886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36887 @node GDB/MI Symbol Query
36888 @section @sc{gdb/mi} Symbol Query Commands
36892 @findex -symbol-info-address
36893 @subheading The @code{-symbol-info-address} Command
36895 @subsubheading Synopsis
36898 -symbol-info-address @var{symbol}
36901 Describe where @var{symbol} is stored.
36903 @subsubheading @value{GDBN} Command
36905 The corresponding @value{GDBN} command is @samp{info address}.
36907 @subsubheading Example
36911 @findex -symbol-info-file
36912 @subheading The @code{-symbol-info-file} Command
36914 @subsubheading Synopsis
36920 Show the file for the symbol.
36922 @subsubheading @value{GDBN} Command
36924 There's no equivalent @value{GDBN} command. @code{gdbtk} has
36925 @samp{gdb_find_file}.
36927 @subsubheading Example
36931 @findex -symbol-info-functions
36932 @anchor{-symbol-info-functions}
36933 @subheading The @code{-symbol-info-functions} Command
36935 @subsubheading Synopsis
36938 -symbol-info-functions [--include-nondebug]
36939 [--type @var{type_regexp}]
36940 [--name @var{name_regexp}]
36941 [--max-results @var{limit}]
36945 Return a list containing the names and types for all global functions
36946 taken from the debug information. The functions are grouped by source
36947 file, and shown with the line number on which each function is
36950 The @code{--include-nondebug} option causes the output to include
36951 code symbols from the symbol table.
36953 The options @code{--type} and @code{--name} allow the symbols returned
36954 to be filtered based on either the name of the function, or the type
36955 signature of the function.
36957 The option @code{--max-results} restricts the command to return no
36958 more than @var{limit} results. If exactly @var{limit} results are
36959 returned then there might be additional results available if a higher
36962 @subsubheading @value{GDBN} Command
36964 The corresponding @value{GDBN} command is @samp{info functions}.
36966 @subsubheading Example
36970 -symbol-info-functions
36973 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36974 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36975 symbols=[@{line="36", name="f4", type="void (int *)",
36976 description="void f4(int *);"@},
36977 @{line="42", name="main", type="int ()",
36978 description="int main();"@},
36979 @{line="30", name="f1", type="my_int_t (int, int)",
36980 description="static my_int_t f1(int, int);"@}]@},
36981 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36982 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36983 symbols=[@{line="33", name="f2", type="float (another_float_t)",
36984 description="float f2(another_float_t);"@},
36985 @{line="39", name="f3", type="int (another_int_t)",
36986 description="int f3(another_int_t);"@},
36987 @{line="27", name="f1", type="another_float_t (int)",
36988 description="static another_float_t f1(int);"@}]@}]@}
36992 -symbol-info-functions --name f1
36995 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36996 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36997 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
36998 description="static my_int_t f1(int, int);"@}]@},
36999 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37000 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37001 symbols=[@{line="27", name="f1", type="another_float_t (int)",
37002 description="static another_float_t f1(int);"@}]@}]@}
37006 -symbol-info-functions --type void
37009 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37010 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37011 symbols=[@{line="36", name="f4", type="void (int *)",
37012 description="void f4(int *);"@}]@}]@}
37016 -symbol-info-functions --include-nondebug
37019 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37020 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37021 symbols=[@{line="36", name="f4", type="void (int *)",
37022 description="void f4(int *);"@},
37023 @{line="42", name="main", type="int ()",
37024 description="int main();"@},
37025 @{line="30", name="f1", type="my_int_t (int, int)",
37026 description="static my_int_t f1(int, int);"@}]@},
37027 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37028 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37029 symbols=[@{line="33", name="f2", type="float (another_float_t)",
37030 description="float f2(another_float_t);"@},
37031 @{line="39", name="f3", type="int (another_int_t)",
37032 description="int f3(another_int_t);"@},
37033 @{line="27", name="f1", type="another_float_t (int)",
37034 description="static another_float_t f1(int);"@}]@}],
37036 [@{address="0x0000000000400398",name="_init"@},
37037 @{address="0x00000000004003b0",name="_start"@},
37043 @findex -symbol-info-module-functions
37044 @anchor{-symbol-info-module-functions}
37045 @subheading The @code{-symbol-info-module-functions} Command
37047 @subsubheading Synopsis
37050 -symbol-info-module-functions [--module @var{module_regexp}]
37051 [--name @var{name_regexp}]
37052 [--type @var{type_regexp}]
37056 Return a list containing the names of all known functions within all
37057 know Fortran modules. The functions are grouped by source file and
37058 containing module, and shown with the line number on which each
37059 function is defined.
37061 The option @code{--module} only returns results for modules matching
37062 @var{module_regexp}. The option @code{--name} only returns functions
37063 whose name matches @var{name_regexp}, and @code{--type} only returns
37064 functions whose type matches @var{type_regexp}.
37066 @subsubheading @value{GDBN} Command
37068 The corresponding @value{GDBN} command is @samp{info module functions}.
37070 @subsubheading Example
37075 -symbol-info-module-functions
37078 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37079 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37080 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
37081 description="void mod1::check_all(void);"@}]@}]@},
37083 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37084 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37085 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
37086 description="void mod2::check_var_i(void);"@}]@}]@},
37088 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37089 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37090 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
37091 description="void mod3::check_all(void);"@},
37092 @{line="27",name="mod3::check_mod2",type="void (void)",
37093 description="void mod3::check_mod2(void);"@}]@}]@},
37094 @{module="modmany",
37095 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37096 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37097 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
37098 description="void modmany::check_some(void);"@}]@}]@},
37100 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37101 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37102 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
37103 description="void moduse::check_all(void);"@},
37104 @{line="49",name="moduse::check_var_x",type="void (void)",
37105 description="void moduse::check_var_x(void);"@}]@}]@}]
37109 @findex -symbol-info-module-variables
37110 @anchor{-symbol-info-module-variables}
37111 @subheading The @code{-symbol-info-module-variables} Command
37113 @subsubheading Synopsis
37116 -symbol-info-module-variables [--module @var{module_regexp}]
37117 [--name @var{name_regexp}]
37118 [--type @var{type_regexp}]
37122 Return a list containing the names of all known variables within all
37123 know Fortran modules. The variables are grouped by source file and
37124 containing module, and shown with the line number on which each
37125 variable is defined.
37127 The option @code{--module} only returns results for modules matching
37128 @var{module_regexp}. The option @code{--name} only returns variables
37129 whose name matches @var{name_regexp}, and @code{--type} only returns
37130 variables whose type matches @var{type_regexp}.
37132 @subsubheading @value{GDBN} Command
37134 The corresponding @value{GDBN} command is @samp{info module variables}.
37136 @subsubheading Example
37141 -symbol-info-module-variables
37144 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37145 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37146 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
37147 description="integer(kind=4) mod1::var_const;"@},
37148 @{line="17",name="mod1::var_i",type="integer(kind=4)",
37149 description="integer(kind=4) mod1::var_i;"@}]@}]@},
37151 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37152 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37153 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
37154 description="integer(kind=4) mod2::var_i;"@}]@}]@},
37156 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37157 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37158 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
37159 description="integer(kind=4) mod3::mod1;"@},
37160 @{line="17",name="mod3::mod2",type="integer(kind=4)",
37161 description="integer(kind=4) mod3::mod2;"@},
37162 @{line="19",name="mod3::var_i",type="integer(kind=4)",
37163 description="integer(kind=4) mod3::var_i;"@}]@}]@},
37164 @{module="modmany",
37165 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37166 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37167 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
37168 description="integer(kind=4) modmany::var_a;"@},
37169 @{line="33",name="modmany::var_b",type="integer(kind=4)",
37170 description="integer(kind=4) modmany::var_b;"@},
37171 @{line="33",name="modmany::var_c",type="integer(kind=4)",
37172 description="integer(kind=4) modmany::var_c;"@},
37173 @{line="33",name="modmany::var_i",type="integer(kind=4)",
37174 description="integer(kind=4) modmany::var_i;"@}]@}]@},
37176 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37177 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37178 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
37179 description="integer(kind=4) moduse::var_x;"@},
37180 @{line="42",name="moduse::var_y",type="integer(kind=4)",
37181 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
37185 @findex -symbol-info-modules
37186 @anchor{-symbol-info-modules}
37187 @subheading The @code{-symbol-info-modules} Command
37189 @subsubheading Synopsis
37192 -symbol-info-modules [--name @var{name_regexp}]
37193 [--max-results @var{limit}]
37198 Return a list containing the names of all known Fortran modules. The
37199 modules are grouped by source file, and shown with the line number on
37200 which each modules is defined.
37202 The option @code{--name} allows the modules returned to be filtered
37203 based the name of the module.
37205 The option @code{--max-results} restricts the command to return no
37206 more than @var{limit} results. If exactly @var{limit} results are
37207 returned then there might be additional results available if a higher
37210 @subsubheading @value{GDBN} Command
37212 The corresponding @value{GDBN} command is @samp{info modules}.
37214 @subsubheading Example
37218 -symbol-info-modules
37221 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37222 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37223 symbols=[@{line="16",name="mod1"@},
37224 @{line="22",name="mod2"@}]@},
37225 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37226 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37227 symbols=[@{line="16",name="mod3"@},
37228 @{line="22",name="modmany"@},
37229 @{line="26",name="moduse"@}]@}]@}
37233 -symbol-info-modules --name mod[123]
37236 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37237 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
37238 symbols=[@{line="16",name="mod1"@},
37239 @{line="22",name="mod2"@}]@},
37240 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37241 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
37242 symbols=[@{line="16",name="mod3"@}]@}]@}
37246 @findex -symbol-info-types
37247 @anchor{-symbol-info-types}
37248 @subheading The @code{-symbol-info-types} Command
37250 @subsubheading Synopsis
37253 -symbol-info-types [--name @var{name_regexp}]
37254 [--max-results @var{limit}]
37259 Return a list of all defined types. The types are grouped by source
37260 file, and shown with the line number on which each user defined type
37261 is defined. Some base types are not defined in the source code but
37262 are added to the debug information by the compiler, for example
37263 @code{int}, @code{float}, etc.; these types do not have an associated
37266 The option @code{--name} allows the list of types returned to be
37269 The option @code{--max-results} restricts the command to return no
37270 more than @var{limit} results. If exactly @var{limit} results are
37271 returned then there might be additional results available if a higher
37274 @subsubheading @value{GDBN} Command
37276 The corresponding @value{GDBN} command is @samp{info types}.
37278 @subsubheading Example
37285 [@{filename="gdb.mi/mi-sym-info-1.c",
37286 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37287 symbols=[@{name="float"@},
37289 @{line="27",name="typedef int my_int_t;"@}]@},
37290 @{filename="gdb.mi/mi-sym-info-2.c",
37291 fullname="/project/gdb.mi/mi-sym-info-2.c",
37292 symbols=[@{line="24",name="typedef float another_float_t;"@},
37293 @{line="23",name="typedef int another_int_t;"@},
37295 @{name="int"@}]@}]@}
37299 -symbol-info-types --name _int_
37302 [@{filename="gdb.mi/mi-sym-info-1.c",
37303 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37304 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
37305 @{filename="gdb.mi/mi-sym-info-2.c",
37306 fullname="/project/gdb.mi/mi-sym-info-2.c",
37307 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
37311 @findex -symbol-info-variables
37312 @anchor{-symbol-info-variables}
37313 @subheading The @code{-symbol-info-variables} Command
37315 @subsubheading Synopsis
37318 -symbol-info-variables [--include-nondebug]
37319 [--type @var{type_regexp}]
37320 [--name @var{name_regexp}]
37321 [--max-results @var{limit}]
37326 Return a list containing the names and types for all global variables
37327 taken from the debug information. The variables are grouped by source
37328 file, and shown with the line number on which each variable is
37331 The @code{--include-nondebug} option causes the output to include
37332 data symbols from the symbol table.
37334 The options @code{--type} and @code{--name} allow the symbols returned
37335 to be filtered based on either the name of the variable, or the type
37338 The option @code{--max-results} restricts the command to return no
37339 more than @var{limit} results. If exactly @var{limit} results are
37340 returned then there might be additional results available if a higher
37343 @subsubheading @value{GDBN} Command
37345 The corresponding @value{GDBN} command is @samp{info variables}.
37347 @subsubheading Example
37351 -symbol-info-variables
37354 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37355 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37356 symbols=[@{line="25",name="global_f1",type="float",
37357 description="static float global_f1;"@},
37358 @{line="24",name="global_i1",type="int",
37359 description="static int global_i1;"@}]@},
37360 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37361 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37362 symbols=[@{line="21",name="global_f2",type="int",
37363 description="int global_f2;"@},
37364 @{line="20",name="global_i2",type="int",
37365 description="int global_i2;"@},
37366 @{line="19",name="global_f1",type="float",
37367 description="static float global_f1;"@},
37368 @{line="18",name="global_i1",type="int",
37369 description="static int global_i1;"@}]@}]@}
37373 -symbol-info-variables --name f1
37376 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37377 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37378 symbols=[@{line="25",name="global_f1",type="float",
37379 description="static float global_f1;"@}]@},
37380 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37381 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37382 symbols=[@{line="19",name="global_f1",type="float",
37383 description="static float global_f1;"@}]@}]@}
37387 -symbol-info-variables --type float
37390 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37391 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37392 symbols=[@{line="25",name="global_f1",type="float",
37393 description="static float global_f1;"@}]@},
37394 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37395 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37396 symbols=[@{line="19",name="global_f1",type="float",
37397 description="static float global_f1;"@}]@}]@}
37401 -symbol-info-variables --include-nondebug
37404 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37405 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
37406 symbols=[@{line="25",name="global_f1",type="float",
37407 description="static float global_f1;"@},
37408 @{line="24",name="global_i1",type="int",
37409 description="static int global_i1;"@}]@},
37410 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37411 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
37412 symbols=[@{line="21",name="global_f2",type="int",
37413 description="int global_f2;"@},
37414 @{line="20",name="global_i2",type="int",
37415 description="int global_i2;"@},
37416 @{line="19",name="global_f1",type="float",
37417 description="static float global_f1;"@},
37418 @{line="18",name="global_i1",type="int",
37419 description="static int global_i1;"@}]@}],
37421 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
37422 @{address="0x00000000004005d8",name="__dso_handle"@}
37429 @findex -symbol-info-line
37430 @subheading The @code{-symbol-info-line} Command
37432 @subsubheading Synopsis
37438 Show the core addresses of the code for a source line.
37440 @subsubheading @value{GDBN} Command
37442 The corresponding @value{GDBN} command is @samp{info line}.
37443 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
37445 @subsubheading Example
37449 @findex -symbol-info-symbol
37450 @subheading The @code{-symbol-info-symbol} Command
37452 @subsubheading Synopsis
37455 -symbol-info-symbol @var{addr}
37458 Describe what symbol is at location @var{addr}.
37460 @subsubheading @value{GDBN} Command
37462 The corresponding @value{GDBN} command is @samp{info symbol}.
37464 @subsubheading Example
37468 @findex -symbol-list-functions
37469 @subheading The @code{-symbol-list-functions} Command
37471 @subsubheading Synopsis
37474 -symbol-list-functions
37477 List the functions in the executable.
37479 @subsubheading @value{GDBN} Command
37481 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
37482 @samp{gdb_search} in @code{gdbtk}.
37484 @subsubheading Example
37489 @findex -symbol-list-lines
37490 @subheading The @code{-symbol-list-lines} Command
37492 @subsubheading Synopsis
37495 -symbol-list-lines @var{filename}
37498 Print the list of lines that contain code and their associated program
37499 addresses for the given source filename. The entries are sorted in
37500 ascending PC order.
37502 @subsubheading @value{GDBN} Command
37504 There is no corresponding @value{GDBN} command.
37506 @subsubheading Example
37509 -symbol-list-lines basics.c
37510 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
37516 @findex -symbol-list-types
37517 @subheading The @code{-symbol-list-types} Command
37519 @subsubheading Synopsis
37525 List all the type names.
37527 @subsubheading @value{GDBN} Command
37529 The corresponding commands are @samp{info types} in @value{GDBN},
37530 @samp{gdb_search} in @code{gdbtk}.
37532 @subsubheading Example
37536 @findex -symbol-list-variables
37537 @subheading The @code{-symbol-list-variables} Command
37539 @subsubheading Synopsis
37542 -symbol-list-variables
37545 List all the global and static variable names.
37547 @subsubheading @value{GDBN} Command
37549 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
37551 @subsubheading Example
37555 @findex -symbol-locate
37556 @subheading The @code{-symbol-locate} Command
37558 @subsubheading Synopsis
37564 @subsubheading @value{GDBN} Command
37566 @samp{gdb_loc} in @code{gdbtk}.
37568 @subsubheading Example
37572 @findex -symbol-type
37573 @subheading The @code{-symbol-type} Command
37575 @subsubheading Synopsis
37578 -symbol-type @var{variable}
37581 Show type of @var{variable}.
37583 @subsubheading @value{GDBN} Command
37585 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
37586 @samp{gdb_obj_variable}.
37588 @subsubheading Example
37593 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37594 @node GDB/MI File Commands
37595 @section @sc{gdb/mi} File Commands
37597 This section describes the GDB/MI commands to specify executable file names
37598 and to read in and obtain symbol table information.
37600 @findex -file-exec-and-symbols
37601 @subheading The @code{-file-exec-and-symbols} Command
37603 @subsubheading Synopsis
37606 -file-exec-and-symbols @var{file}
37609 Specify the executable file to be debugged. This file is the one from
37610 which the symbol table is also read. If no file is specified, the
37611 command clears the executable and symbol information. If breakpoints
37612 are set when using this command with no arguments, @value{GDBN} will produce
37613 error messages. Otherwise, no output is produced, except a completion
37616 @subsubheading @value{GDBN} Command
37618 The corresponding @value{GDBN} command is @samp{file}.
37620 @subsubheading Example
37624 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
37630 @findex -file-exec-file
37631 @subheading The @code{-file-exec-file} Command
37633 @subsubheading Synopsis
37636 -file-exec-file @var{file}
37639 Specify the executable file to be debugged. Unlike
37640 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
37641 from this file. If used without argument, @value{GDBN} clears the information
37642 about the executable file. No output is produced, except a completion
37645 @subsubheading @value{GDBN} Command
37647 The corresponding @value{GDBN} command is @samp{exec-file}.
37649 @subsubheading Example
37653 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
37660 @findex -file-list-exec-sections
37661 @subheading The @code{-file-list-exec-sections} Command
37663 @subsubheading Synopsis
37666 -file-list-exec-sections
37669 List the sections of the current executable file.
37671 @subsubheading @value{GDBN} Command
37673 The @value{GDBN} command @samp{info file} shows, among the rest, the same
37674 information as this command. @code{gdbtk} has a corresponding command
37675 @samp{gdb_load_info}.
37677 @subsubheading Example
37682 @findex -file-list-exec-source-file
37683 @subheading The @code{-file-list-exec-source-file} Command
37685 @subsubheading Synopsis
37688 -file-list-exec-source-file
37691 List the line number, the current source file, and the absolute path
37692 to the current source file for the current executable. The macro
37693 information field has a value of @samp{1} or @samp{0} depending on
37694 whether or not the file includes preprocessor macro information.
37696 @subsubheading @value{GDBN} Command
37698 The @value{GDBN} equivalent is @samp{info source}
37700 @subsubheading Example
37704 123-file-list-exec-source-file
37705 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
37710 @findex -file-list-exec-source-files
37711 @subheading The @code{-file-list-exec-source-files} Command
37712 @kindex info sources
37714 @subsubheading Synopsis
37717 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
37718 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
37720 @r{[} @var{regexp} @r{]}
37723 This command returns information about the source files @value{GDBN}
37724 knows about, it will output both the filename and fullname (absolute
37725 file name) of a source file, though the fullname can be elided if this
37726 information is not known to @value{GDBN}.
37728 With no arguments this command returns a list of source files. Each
37729 source file is represented by a tuple with the fields; @var{file},
37730 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
37731 display name for the file, while @var{fullname} is the absolute name
37732 of the file. The @var{fullname} field can be elided if the absolute
37733 name of the source file can't be computed. The field
37734 @var{debug-fully-read} will be a string, either @code{true} or
37735 @code{false}. When @code{true}, this indicates the full debug
37736 information for the compilation unit describing this file has been
37737 read in. When @code{false}, the full debug information has not yet
37738 been read in. While reading in the full debug information it is
37739 possible that @value{GDBN} could become aware of additional source
37742 The optional @var{regexp} can be used to filter the list of source
37743 files returned. The @var{regexp} will be matched against the full
37744 source file name. The matching is case-sensitive, except on operating
37745 systems that have case-insensitive filesystem (e.g.,
37746 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
37747 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
37748 @var{regexp} starts with @samp{-}).
37750 If @code{--dirname} is provided, then @var{regexp} is matched only
37751 against the directory name of each source file. If @code{--basename}
37752 is provided, then @var{regexp} is matched against the basename of each
37753 source file. Only one of @code{--dirname} or @code{--basename} may be
37754 given, and if either is given then @var{regexp} is required.
37756 If @code{--group-by-objfile} is used then the format of the results is
37757 changed. The results will now be a list of tuples, with each tuple
37758 representing an object file (executable or shared library) loaded into
37759 @value{GDBN}. The fields of these tuples are; @var{filename},
37760 @var{debug-info}, and @var{sources}. The @var{filename} is the
37761 absolute name of the object file, @var{debug-info} is a string with
37762 one of the following values:
37766 This object file has no debug information.
37767 @item partially-read
37768 This object file has debug information, but it is not fully read in
37769 yet. When it is read in later, GDB might become aware of additional
37772 This object file has debug information, and this information is fully
37773 read into GDB. The list of source files is complete.
37776 The @var{sources} is a list or tuples, with each tuple describing a
37777 single source file with the same fields as described previously. The
37778 @var{sources} list can be empty for object files that have no debug
37781 @subsubheading @value{GDBN} Command
37783 The @value{GDBN} equivalent is @samp{info sources}.
37784 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
37786 @subsubheading Example
37789 -file-list-exec-source-files
37790 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
37791 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
37792 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
37794 -file-list-exec-source-files
37795 ^done,files=[@{file="test.c",
37796 fullname="/tmp/info-sources/test.c",
37797 debug-fully-read="true"@},
37798 @{file="/usr/include/stdc-predef.h",
37799 fullname="/usr/include/stdc-predef.h",
37800 debug-fully-read="true"@},
37802 fullname="/tmp/info-sources/header.h",
37803 debug-fully-read="true"@},
37805 fullname="/tmp/info-sources/helper.c",
37806 debug-fully-read="true"@}]
37808 -file-list-exec-source-files -- \\.c
37809 ^done,files=[@{file="test.c",
37810 fullname="/tmp/info-sources/test.c",
37811 debug-fully-read="true"@},
37813 fullname="/tmp/info-sources/helper.c",
37814 debug-fully-read="true"@}]
37816 -file-list-exec-source-files --group-by-objfile
37817 ^done,files=[@{filename="/tmp/info-sources/test.x",
37818 debug-info="fully-read",
37819 sources=[@{file="test.c",
37820 fullname="/tmp/info-sources/test.c",
37821 debug-fully-read="true"@},
37822 @{file="/usr/include/stdc-predef.h",
37823 fullname="/usr/include/stdc-predef.h",
37824 debug-fully-read="true"@},
37826 fullname="/tmp/info-sources/header.h",
37827 debug-fully-read="true"@}]@},
37828 @{filename="/lib64/ld-linux-x86-64.so.2",
37831 @{filename="system-supplied DSO at 0x7ffff7fcf000",
37834 @{filename="/tmp/info-sources/libhelper.so",
37835 debug-info="fully-read",
37836 sources=[@{file="helper.c",
37837 fullname="/tmp/info-sources/helper.c",
37838 debug-fully-read="true"@},
37839 @{file="/usr/include/stdc-predef.h",
37840 fullname="/usr/include/stdc-predef.h",
37841 debug-fully-read="true"@},
37843 fullname="/tmp/info-sources/header.h",
37844 debug-fully-read="true"@}]@},
37845 @{filename="/lib64/libc.so.6",
37850 @findex -file-list-shared-libraries
37851 @subheading The @code{-file-list-shared-libraries} Command
37853 @subsubheading Synopsis
37856 -file-list-shared-libraries [ @var{regexp} ]
37859 List the shared libraries in the program.
37860 With a regular expression @var{regexp}, only those libraries whose
37861 names match @var{regexp} are listed.
37863 @subsubheading @value{GDBN} Command
37865 The corresponding @value{GDBN} command is @samp{info shared}. The fields
37866 have a similar meaning to the @code{=library-loaded} notification.
37867 The @code{ranges} field specifies the multiple segments belonging to this
37868 library. Each range has the following fields:
37872 The address defining the inclusive lower bound of the segment.
37874 The address defining the exclusive upper bound of the segment.
37877 @subsubheading Example
37880 -file-list-exec-source-files
37881 ^done,shared-libraries=[
37882 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
37883 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
37889 @findex -file-list-symbol-files
37890 @subheading The @code{-file-list-symbol-files} Command
37892 @subsubheading Synopsis
37895 -file-list-symbol-files
37900 @subsubheading @value{GDBN} Command
37902 The corresponding @value{GDBN} command is @samp{info file} (part of it).
37904 @subsubheading Example
37909 @findex -file-symbol-file
37910 @subheading The @code{-file-symbol-file} Command
37912 @subsubheading Synopsis
37915 -file-symbol-file @var{file}
37918 Read symbol table info from the specified @var{file} argument. When
37919 used without arguments, clears @value{GDBN}'s symbol table info. No output is
37920 produced, except for a completion notification.
37922 @subsubheading @value{GDBN} Command
37924 The corresponding @value{GDBN} command is @samp{symbol-file}.
37926 @subsubheading Example
37930 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
37936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37937 @node GDB/MI Memory Overlay Commands
37938 @section @sc{gdb/mi} Memory Overlay Commands
37940 The memory overlay commands are not implemented.
37942 @c @subheading -overlay-auto
37944 @c @subheading -overlay-list-mapping-state
37946 @c @subheading -overlay-list-overlays
37948 @c @subheading -overlay-map
37950 @c @subheading -overlay-off
37952 @c @subheading -overlay-on
37954 @c @subheading -overlay-unmap
37956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37957 @node GDB/MI Signal Handling Commands
37958 @section @sc{gdb/mi} Signal Handling Commands
37960 Signal handling commands are not implemented.
37962 @c @subheading -signal-handle
37964 @c @subheading -signal-list-handle-actions
37966 @c @subheading -signal-list-signal-types
37970 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37971 @node GDB/MI Target Manipulation
37972 @section @sc{gdb/mi} Target Manipulation Commands
37975 @findex -target-attach
37976 @subheading The @code{-target-attach} Command
37978 @subsubheading Synopsis
37981 -target-attach @var{pid} | @var{gid} | @var{file}
37984 Attach to a process @var{pid} or a file @var{file} outside of
37985 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
37986 group, the id previously returned by
37987 @samp{-list-thread-groups --available} must be used.
37989 @subsubheading @value{GDBN} Command
37991 The corresponding @value{GDBN} command is @samp{attach}.
37993 @subsubheading Example
37997 =thread-created,id="1"
37998 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
38004 @findex -target-compare-sections
38005 @subheading The @code{-target-compare-sections} Command
38007 @subsubheading Synopsis
38010 -target-compare-sections [ @var{section} ]
38013 Compare data of section @var{section} on target to the exec file.
38014 Without the argument, all sections are compared.
38016 @subsubheading @value{GDBN} Command
38018 The @value{GDBN} equivalent is @samp{compare-sections}.
38020 @subsubheading Example
38025 @findex -target-detach
38026 @subheading The @code{-target-detach} Command
38028 @subsubheading Synopsis
38031 -target-detach [ @var{pid} | @var{gid} ]
38034 Detach from the remote target which normally resumes its execution.
38035 If either @var{pid} or @var{gid} is specified, detaches from either
38036 the specified process, or specified thread group. There's no output.
38038 @subsubheading @value{GDBN} Command
38040 The corresponding @value{GDBN} command is @samp{detach}.
38042 @subsubheading Example
38052 @findex -target-disconnect
38053 @subheading The @code{-target-disconnect} Command
38055 @subsubheading Synopsis
38061 Disconnect from the remote target. There's no output and the target is
38062 generally not resumed.
38064 @subsubheading @value{GDBN} Command
38066 The corresponding @value{GDBN} command is @samp{disconnect}.
38068 @subsubheading Example
38078 @findex -target-download
38079 @subheading The @code{-target-download} Command
38081 @subsubheading Synopsis
38087 Loads the executable onto the remote target.
38088 It prints out an update message every half second, which includes the fields:
38092 The name of the section.
38094 The size of what has been sent so far for that section.
38096 The size of the section.
38098 The total size of what was sent so far (the current and the previous sections).
38100 The size of the overall executable to download.
38104 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
38105 @sc{gdb/mi} Output Syntax}).
38107 In addition, it prints the name and size of the sections, as they are
38108 downloaded. These messages include the following fields:
38112 The name of the section.
38114 The size of the section.
38116 The size of the overall executable to download.
38120 At the end, a summary is printed.
38122 @subsubheading @value{GDBN} Command
38124 The corresponding @value{GDBN} command is @samp{load}.
38126 @subsubheading Example
38128 Note: each status message appears on a single line. Here the messages
38129 have been broken down so that they can fit onto a page.
38134 +download,@{section=".text",section-size="6668",total-size="9880"@}
38135 +download,@{section=".text",section-sent="512",section-size="6668",
38136 total-sent="512",total-size="9880"@}
38137 +download,@{section=".text",section-sent="1024",section-size="6668",
38138 total-sent="1024",total-size="9880"@}
38139 +download,@{section=".text",section-sent="1536",section-size="6668",
38140 total-sent="1536",total-size="9880"@}
38141 +download,@{section=".text",section-sent="2048",section-size="6668",
38142 total-sent="2048",total-size="9880"@}
38143 +download,@{section=".text",section-sent="2560",section-size="6668",
38144 total-sent="2560",total-size="9880"@}
38145 +download,@{section=".text",section-sent="3072",section-size="6668",
38146 total-sent="3072",total-size="9880"@}
38147 +download,@{section=".text",section-sent="3584",section-size="6668",
38148 total-sent="3584",total-size="9880"@}
38149 +download,@{section=".text",section-sent="4096",section-size="6668",
38150 total-sent="4096",total-size="9880"@}
38151 +download,@{section=".text",section-sent="4608",section-size="6668",
38152 total-sent="4608",total-size="9880"@}
38153 +download,@{section=".text",section-sent="5120",section-size="6668",
38154 total-sent="5120",total-size="9880"@}
38155 +download,@{section=".text",section-sent="5632",section-size="6668",
38156 total-sent="5632",total-size="9880"@}
38157 +download,@{section=".text",section-sent="6144",section-size="6668",
38158 total-sent="6144",total-size="9880"@}
38159 +download,@{section=".text",section-sent="6656",section-size="6668",
38160 total-sent="6656",total-size="9880"@}
38161 +download,@{section=".init",section-size="28",total-size="9880"@}
38162 +download,@{section=".fini",section-size="28",total-size="9880"@}
38163 +download,@{section=".data",section-size="3156",total-size="9880"@}
38164 +download,@{section=".data",section-sent="512",section-size="3156",
38165 total-sent="7236",total-size="9880"@}
38166 +download,@{section=".data",section-sent="1024",section-size="3156",
38167 total-sent="7748",total-size="9880"@}
38168 +download,@{section=".data",section-sent="1536",section-size="3156",
38169 total-sent="8260",total-size="9880"@}
38170 +download,@{section=".data",section-sent="2048",section-size="3156",
38171 total-sent="8772",total-size="9880"@}
38172 +download,@{section=".data",section-sent="2560",section-size="3156",
38173 total-sent="9284",total-size="9880"@}
38174 +download,@{section=".data",section-sent="3072",section-size="3156",
38175 total-sent="9796",total-size="9880"@}
38176 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
38183 @findex -target-exec-status
38184 @subheading The @code{-target-exec-status} Command
38186 @subsubheading Synopsis
38189 -target-exec-status
38192 Provide information on the state of the target (whether it is running or
38193 not, for instance).
38195 @subsubheading @value{GDBN} Command
38197 There's no equivalent @value{GDBN} command.
38199 @subsubheading Example
38203 @findex -target-list-available-targets
38204 @subheading The @code{-target-list-available-targets} Command
38206 @subsubheading Synopsis
38209 -target-list-available-targets
38212 List the possible targets to connect to.
38214 @subsubheading @value{GDBN} Command
38216 The corresponding @value{GDBN} command is @samp{help target}.
38218 @subsubheading Example
38222 @findex -target-list-current-targets
38223 @subheading The @code{-target-list-current-targets} Command
38225 @subsubheading Synopsis
38228 -target-list-current-targets
38231 Describe the current target.
38233 @subsubheading @value{GDBN} Command
38235 The corresponding information is printed by @samp{info file} (among
38238 @subsubheading Example
38242 @findex -target-list-parameters
38243 @subheading The @code{-target-list-parameters} Command
38245 @subsubheading Synopsis
38248 -target-list-parameters
38254 @subsubheading @value{GDBN} Command
38258 @subsubheading Example
38261 @findex -target-flash-erase
38262 @subheading The @code{-target-flash-erase} Command
38264 @subsubheading Synopsis
38267 -target-flash-erase
38270 Erases all known flash memory regions on the target.
38272 The corresponding @value{GDBN} command is @samp{flash-erase}.
38274 The output is a list of flash regions that have been erased, with starting
38275 addresses and memory region sizes.
38279 -target-flash-erase
38280 ^done,erased-regions=@{address="0x0",size="0x40000"@}
38284 @findex -target-select
38285 @subheading The @code{-target-select} Command
38287 @subsubheading Synopsis
38290 -target-select @var{type} @var{parameters @dots{}}
38293 Connect @value{GDBN} to the remote target. This command takes two args:
38297 The type of target, for instance @samp{remote}, etc.
38298 @item @var{parameters}
38299 Device names, host names and the like. @xref{Target Commands, ,
38300 Commands for Managing Targets}, for more details.
38303 The output is a connection notification, followed by the address at
38304 which the target program is, in the following form:
38307 ^connected,addr="@var{address}",func="@var{function name}",
38308 args=[@var{arg list}]
38311 @subsubheading @value{GDBN} Command
38313 The corresponding @value{GDBN} command is @samp{target}.
38315 @subsubheading Example
38319 -target-select remote /dev/ttya
38320 ^connected,addr="0xfe00a300",func="??",args=[]
38324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38325 @node GDB/MI File Transfer Commands
38326 @section @sc{gdb/mi} File Transfer Commands
38329 @findex -target-file-put
38330 @subheading The @code{-target-file-put} Command
38332 @subsubheading Synopsis
38335 -target-file-put @var{hostfile} @var{targetfile}
38338 Copy file @var{hostfile} from the host system (the machine running
38339 @value{GDBN}) to @var{targetfile} on the target system.
38341 @subsubheading @value{GDBN} Command
38343 The corresponding @value{GDBN} command is @samp{remote put}.
38345 @subsubheading Example
38349 -target-file-put localfile remotefile
38355 @findex -target-file-get
38356 @subheading The @code{-target-file-get} Command
38358 @subsubheading Synopsis
38361 -target-file-get @var{targetfile} @var{hostfile}
38364 Copy file @var{targetfile} from the target system to @var{hostfile}
38365 on the host system.
38367 @subsubheading @value{GDBN} Command
38369 The corresponding @value{GDBN} command is @samp{remote get}.
38371 @subsubheading Example
38375 -target-file-get remotefile localfile
38381 @findex -target-file-delete
38382 @subheading The @code{-target-file-delete} Command
38384 @subsubheading Synopsis
38387 -target-file-delete @var{targetfile}
38390 Delete @var{targetfile} from the target system.
38392 @subsubheading @value{GDBN} Command
38394 The corresponding @value{GDBN} command is @samp{remote delete}.
38396 @subsubheading Example
38400 -target-file-delete remotefile
38406 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38407 @node GDB/MI Ada Exceptions Commands
38408 @section Ada Exceptions @sc{gdb/mi} Commands
38410 @findex -info-ada-exceptions
38411 @subheading The @code{-info-ada-exceptions} Command
38413 @subsubheading Synopsis
38416 -info-ada-exceptions [ @var{regexp}]
38419 List all Ada exceptions defined within the program being debugged.
38420 With a regular expression @var{regexp}, only those exceptions whose
38421 names match @var{regexp} are listed.
38423 @subsubheading @value{GDBN} Command
38425 The corresponding @value{GDBN} command is @samp{info exceptions}.
38427 @subsubheading Result
38429 The result is a table of Ada exceptions. The following columns are
38430 defined for each exception:
38434 The name of the exception.
38437 The address of the exception.
38441 @subsubheading Example
38444 -info-ada-exceptions aint
38445 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
38446 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
38447 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
38448 body=[@{name="constraint_error",address="0x0000000000613da0"@},
38449 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
38452 @subheading Catching Ada Exceptions
38454 The commands describing how to ask @value{GDBN} to stop when a program
38455 raises an exception are described at @ref{Ada Exception GDB/MI
38456 Catchpoint Commands}.
38459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38460 @node GDB/MI Support Commands
38461 @section @sc{gdb/mi} Support Commands
38463 Since new commands and features get regularly added to @sc{gdb/mi},
38464 some commands are available to help front-ends query the debugger
38465 about support for these capabilities. Similarly, it is also possible
38466 to query @value{GDBN} about target support of certain features.
38468 @cindex @code{-info-gdb-mi-command}
38469 @findex -info-gdb-mi-command
38470 @subheading The @code{-info-gdb-mi-command} Command
38472 @subsubheading Synopsis
38475 -info-gdb-mi-command @var{cmd_name}
38478 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
38480 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
38481 is technically not part of the command name (@pxref{GDB/MI Input
38482 Syntax}), and thus should be omitted in @var{cmd_name}. However,
38483 for ease of use, this command also accepts the form with the leading
38486 @subsubheading @value{GDBN} Command
38488 There is no corresponding @value{GDBN} command.
38490 @subsubheading Result
38492 The result is a tuple. There is currently only one field:
38496 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
38497 @code{"false"} otherwise.
38501 @subsubheading Example
38503 Here is an example where the @sc{gdb/mi} command does not exist:
38506 -info-gdb-mi-command unsupported-command
38507 ^done,command=@{exists="false"@}
38511 And here is an example where the @sc{gdb/mi} command is known
38515 -info-gdb-mi-command symbol-list-lines
38516 ^done,command=@{exists="true"@}
38519 @findex -list-features
38520 @cindex supported @sc{gdb/mi} features, list
38521 @subheading The @code{-list-features} Command
38523 Returns a list of particular features of the MI protocol that
38524 this version of gdb implements. A feature can be a command,
38525 or a new field in an output of some command, or even an
38526 important bugfix. While a frontend can sometimes detect presence
38527 of a feature at runtime, it is easier to perform detection at debugger
38530 The command returns a list of strings, with each string naming an
38531 available feature. Each returned string is just a name, it does not
38532 have any internal structure. The list of possible feature names
38538 (gdb) -list-features
38539 ^done,result=["feature1","feature2"]
38542 The current list of features is:
38545 @item frozen-varobjs
38546 Indicates support for the @code{-var-set-frozen} command, as well
38547 as possible presence of the @code{frozen} field in the output
38548 of @code{-varobj-create}.
38549 @item pending-breakpoints
38550 Indicates support for the @option{-f} option to the @code{-break-insert}
38553 Indicates Python scripting support, Python-based
38554 pretty-printing commands, and possible presence of the
38555 @samp{display_hint} field in the output of @code{-var-list-children}
38557 Indicates support for the @code{-thread-info} command.
38558 @item data-read-memory-bytes
38559 Indicates support for the @code{-data-read-memory-bytes} and the
38560 @code{-data-write-memory-bytes} commands.
38561 @item breakpoint-notifications
38562 Indicates that changes to breakpoints and breakpoints created via the
38563 CLI will be announced via async records.
38564 @item ada-task-info
38565 Indicates support for the @code{-ada-task-info} command.
38566 @item language-option
38567 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
38568 option (@pxref{Context management}).
38569 @item info-gdb-mi-command
38570 Indicates support for the @code{-info-gdb-mi-command} command.
38571 @item undefined-command-error-code
38572 Indicates support for the "undefined-command" error code in error result
38573 records, produced when trying to execute an undefined @sc{gdb/mi} command
38574 (@pxref{GDB/MI Result Records}).
38575 @item exec-run-start-option
38576 Indicates that the @code{-exec-run} command supports the @option{--start}
38577 option (@pxref{GDB/MI Program Execution}).
38578 @item data-disassemble-a-option
38579 Indicates that the @code{-data-disassemble} command supports the @option{-a}
38580 option (@pxref{GDB/MI Data Manipulation}).
38581 @item simple-values-ref-types
38582 Indicates that the @code{--simple-values} argument to the
38583 @code{-stack-list-arguments}, @code{-stack-list-locals},
38584 @code{-stack-list-variables}, and @code{-var-list-children} commands
38585 takes reference types into account: that is, a value is considered
38586 simple if it is neither an array, structure, or union, nor a reference
38587 to an array, structure, or union.
38590 @findex -list-target-features
38591 @subheading The @code{-list-target-features} Command
38593 Returns a list of particular features that are supported by the
38594 target. Those features affect the permitted MI commands, but
38595 unlike the features reported by the @code{-list-features} command, the
38596 features depend on which target GDB is using at the moment. Whenever
38597 a target can change, due to commands such as @code{-target-select},
38598 @code{-target-attach} or @code{-exec-run}, the list of target features
38599 may change, and the frontend should obtain it again.
38603 (gdb) -list-target-features
38604 ^done,result=["async"]
38607 The current list of features is:
38611 Indicates that the target is capable of asynchronous command
38612 execution, which means that @value{GDBN} will accept further commands
38613 while the target is running.
38616 Indicates that the target is capable of reverse execution.
38617 @xref{Reverse Execution}, for more information.
38621 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38622 @node GDB/MI Miscellaneous Commands
38623 @section Miscellaneous @sc{gdb/mi} Commands
38625 @c @subheading -gdb-complete
38628 @subheading The @code{-gdb-exit} Command
38630 @subsubheading Synopsis
38636 Exit @value{GDBN} immediately.
38638 @subsubheading @value{GDBN} Command
38640 Approximately corresponds to @samp{quit}.
38642 @subsubheading Example
38652 @findex -exec-abort
38653 @subheading The @code{-exec-abort} Command
38655 @subsubheading Synopsis
38661 Kill the inferior running program.
38663 @subsubheading @value{GDBN} Command
38665 The corresponding @value{GDBN} command is @samp{kill}.
38667 @subsubheading Example
38673 @subheading The @code{-gdb-set} Command
38675 @subsubheading Synopsis
38681 Set an internal @value{GDBN} variable.
38682 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
38684 @subsubheading @value{GDBN} Command
38686 The corresponding @value{GDBN} command is @samp{set}.
38688 @subsubheading Example
38699 @subheading The @code{-gdb-show} Command
38701 @subsubheading Synopsis
38707 Show the current value of a @value{GDBN} variable.
38709 @subsubheading @value{GDBN} Command
38711 The corresponding @value{GDBN} command is @samp{show}.
38713 @subsubheading Example
38722 @c @subheading -gdb-source
38725 @findex -gdb-version
38726 @subheading The @code{-gdb-version} Command
38728 @subsubheading Synopsis
38734 Show version information for @value{GDBN}. Used mostly in testing.
38736 @subsubheading @value{GDBN} Command
38738 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
38739 default shows this information when you start an interactive session.
38741 @subsubheading Example
38743 @c This example modifies the actual output from GDB to avoid overfull
38749 ~Copyright 2000 Free Software Foundation, Inc.
38750 ~GDB is free software, covered by the GNU General Public License, and
38751 ~you are welcome to change it and/or distribute copies of it under
38752 ~ certain conditions.
38753 ~Type "show copying" to see the conditions.
38754 ~There is absolutely no warranty for GDB. Type "show warranty" for
38756 ~This GDB was configured as
38757 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
38762 @findex -list-thread-groups
38763 @subheading The @code{-list-thread-groups} Command
38765 @subsubheading Synopsis
38768 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
38771 Lists thread groups (@pxref{Thread groups}). When a single thread
38772 group is passed as the argument, lists the children of that group.
38773 When several thread group are passed, lists information about those
38774 thread groups. Without any parameters, lists information about all
38775 top-level thread groups.
38777 Normally, thread groups that are being debugged are reported.
38778 With the @samp{--available} option, @value{GDBN} reports thread groups
38779 available on the target.
38781 The output of this command may have either a @samp{threads} result or
38782 a @samp{groups} result. The @samp{thread} result has a list of tuples
38783 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
38784 Information}). The @samp{groups} result has a list of tuples as value,
38785 each tuple describing a thread group. If top-level groups are
38786 requested (that is, no parameter is passed), or when several groups
38787 are passed, the output always has a @samp{groups} result. The format
38788 of the @samp{group} result is described below.
38790 To reduce the number of roundtrips it's possible to list thread groups
38791 together with their children, by passing the @samp{--recurse} option
38792 and the recursion depth. Presently, only recursion depth of 1 is
38793 permitted. If this option is present, then every reported thread group
38794 will also include its children, either as @samp{group} or
38795 @samp{threads} field.
38797 In general, any combination of option and parameters is permitted, with
38798 the following caveats:
38802 When a single thread group is passed, the output will typically
38803 be the @samp{threads} result. Because threads may not contain
38804 anything, the @samp{recurse} option will be ignored.
38807 When the @samp{--available} option is passed, limited information may
38808 be available. In particular, the list of threads of a process might
38809 be inaccessible. Further, specifying specific thread groups might
38810 not give any performance advantage over listing all thread groups.
38811 The frontend should assume that @samp{-list-thread-groups --available}
38812 is always an expensive operation and cache the results.
38816 The @samp{groups} result is a list of tuples, where each tuple may
38817 have the following fields:
38821 Identifier of the thread group. This field is always present.
38822 The identifier is an opaque string; frontends should not try to
38823 convert it to an integer, even though it might look like one.
38826 The type of the thread group. At present, only @samp{process} is a
38830 The target-specific process identifier. This field is only present
38831 for thread groups of type @samp{process} and only if the process exists.
38834 The exit code of this group's last exited thread, formatted in octal.
38835 This field is only present for thread groups of type @samp{process} and
38836 only if the process is not running.
38839 The number of children this thread group has. This field may be
38840 absent for an available thread group.
38843 This field has a list of tuples as value, each tuple describing a
38844 thread. It may be present if the @samp{--recurse} option is
38845 specified, and it's actually possible to obtain the threads.
38848 This field is a list of integers, each identifying a core that one
38849 thread of the group is running on. This field may be absent if
38850 such information is not available.
38853 The name of the executable file that corresponds to this thread group.
38854 The field is only present for thread groups of type @samp{process},
38855 and only if there is a corresponding executable file.
38859 @subsubheading Example
38863 -list-thread-groups
38864 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
38865 -list-thread-groups 17
38866 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
38867 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
38868 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
38869 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
38870 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
38871 -list-thread-groups --available
38872 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
38873 -list-thread-groups --available --recurse 1
38874 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
38875 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
38876 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
38877 -list-thread-groups --available --recurse 1 17 18
38878 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
38879 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
38880 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
38884 @subheading The @code{-info-os} Command
38886 @subsubheading Synopsis
38889 -info-os [ @var{type} ]
38892 If no argument is supplied, the command returns a table of available
38893 operating-system-specific information types. If one of these types is
38894 supplied as an argument @var{type}, then the command returns a table
38895 of data of that type.
38897 The types of information available depend on the target operating
38900 @subsubheading @value{GDBN} Command
38902 The corresponding @value{GDBN} command is @samp{info os}.
38904 @subsubheading Example
38906 When run on a @sc{gnu}/Linux system, the output will look something
38912 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
38913 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
38914 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
38915 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
38916 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
38918 item=@{col0="files",col1="Listing of all file descriptors",
38919 col2="File descriptors"@},
38920 item=@{col0="modules",col1="Listing of all loaded kernel modules",
38921 col2="Kernel modules"@},
38922 item=@{col0="msg",col1="Listing of all message queues",
38923 col2="Message queues"@},
38924 item=@{col0="processes",col1="Listing of all processes",
38925 col2="Processes"@},
38926 item=@{col0="procgroups",col1="Listing of all process groups",
38927 col2="Process groups"@},
38928 item=@{col0="semaphores",col1="Listing of all semaphores",
38929 col2="Semaphores"@},
38930 item=@{col0="shm",col1="Listing of all shared-memory regions",
38931 col2="Shared-memory regions"@},
38932 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
38934 item=@{col0="threads",col1="Listing of all threads",
38938 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
38939 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
38940 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
38941 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
38942 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
38943 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
38944 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
38945 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
38947 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
38948 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
38952 (Note that the MI output here includes a @code{"Title"} column that
38953 does not appear in command-line @code{info os}; this column is useful
38954 for MI clients that want to enumerate the types of data, such as in a
38955 popup menu, but is needless clutter on the command line, and
38956 @code{info os} omits it.)
38958 @findex -add-inferior
38959 @subheading The @code{-add-inferior} Command
38961 @subsubheading Synopsis
38964 -add-inferior [ --no-connection ]
38967 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
38968 inferior is not associated with any executable. Such association may
38969 be established with the @samp{-file-exec-and-symbols} command
38970 (@pxref{GDB/MI File Commands}).
38972 By default, the new inferior begins connected to the same target
38973 connection as the current inferior. For example, if the current
38974 inferior was connected to @code{gdbserver} with @code{target remote},
38975 then the new inferior will be connected to the same @code{gdbserver}
38976 instance. The @samp{--no-connection} option starts the new inferior
38977 with no connection yet. You can then for example use the
38978 @code{-target-select remote} command to connect to some other
38979 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
38982 The command response always has a field, @var{inferior}, whose value
38983 is the identifier of the thread group corresponding to the new
38986 An additional section field, @var{connection}, is optional. This
38987 field will only exist if the new inferior has a target connection. If
38988 this field exists, then its value will be a tuple containing the
38993 The number of the connection used for the new inferior.
38996 The name of the connection type used for the new inferior.
38999 @subsubheading @value{GDBN} Command
39001 The corresponding @value{GDBN} command is @samp{add-inferior}
39002 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
39004 @subsubheading Example
39009 ^done,inferior="i3"
39012 @findex -remove-inferior
39013 @subheading The @code{-remove-inferior} Command
39015 @subsubheading Synopsis
39018 -remove-inferior @var{inferior-id}
39021 Removes an inferior (@pxref{Inferiors Connections and Programs}).
39022 Only inferiors that have exited can be removed. The @var{inferior-id}
39023 is the inferior to be removed, and should be the same id string as
39024 returned by the @samp{-add-inferior} command.
39026 When an inferior is successfully removed a
39027 @code{=thread-group-removed} notification (@pxref{GDB/MI Async
39028 Records}) is emitted, the @var{id} field of which contains the
39029 @var{inferior-id} for the removed inferior.
39031 @subsubheading @value{GDBN} Command
39033 The corresponding @value{GDBN} command is @samp{remove-inferiors}
39034 (@pxref{remove_inferiors_cli,,@samp{remove-inferiors}}).
39036 @subsubheading Example
39040 -remove-inferior i3
39041 =thread-group-removed,id="i3"
39045 @findex -interpreter-exec
39046 @subheading The @code{-interpreter-exec} Command
39048 @subsubheading Synopsis
39051 -interpreter-exec @var{interpreter} @var{command}
39053 @anchor{-interpreter-exec}
39055 Execute the specified @var{command} in the given @var{interpreter}.
39057 @subsubheading @value{GDBN} Command
39059 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
39061 @subsubheading Example
39065 -interpreter-exec console "break main"
39066 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
39067 &"During symbol reading, bad structure-type format.\n"
39068 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
39073 @findex -inferior-tty-set
39074 @subheading The @code{-inferior-tty-set} Command
39076 @subsubheading Synopsis
39079 -inferior-tty-set /dev/pts/1
39082 Set terminal for future runs of the program being debugged.
39084 @subsubheading @value{GDBN} Command
39086 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
39088 @subsubheading Example
39092 -inferior-tty-set /dev/pts/1
39097 @findex -inferior-tty-show
39098 @subheading The @code{-inferior-tty-show} Command
39100 @subsubheading Synopsis
39106 Show terminal for future runs of program being debugged.
39108 @subsubheading @value{GDBN} Command
39110 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
39112 @subsubheading Example
39116 -inferior-tty-set /dev/pts/1
39120 ^done,inferior_tty_terminal="/dev/pts/1"
39124 @findex -enable-timings
39125 @subheading The @code{-enable-timings} Command
39127 @subsubheading Synopsis
39130 -enable-timings [yes | no]
39133 Toggle the printing of the wallclock, user and system times for an MI
39134 command as a field in its output. This command is to help frontend
39135 developers optimize the performance of their code. No argument is
39136 equivalent to @samp{yes}.
39138 @subsubheading @value{GDBN} Command
39142 @subsubheading Example
39150 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
39151 addr="0x080484ed",func="main",file="myprog.c",
39152 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
39154 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
39162 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
39163 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
39164 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
39165 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
39170 @subheading The @code{-complete} Command
39172 @subsubheading Synopsis
39175 -complete @var{command}
39178 Show a list of completions for partially typed CLI @var{command}.
39180 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
39181 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
39182 because @value{GDBN} is used remotely via a SSH connection.
39184 @subsubheading Result
39186 The result consists of two or three fields:
39190 This field contains the completed @var{command}. If @var{command}
39191 has no known completions, this field is omitted.
39194 This field contains a (possibly empty) array of matches. It is always present.
39196 @item max_completions_reached
39197 This field contains @code{1} if number of known completions is above
39198 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
39199 @code{0}. It is always present.
39203 @subsubheading @value{GDBN} Command
39205 The corresponding @value{GDBN} command is @samp{complete}.
39207 @subsubheading Example
39212 ^done,completion="break",
39213 matches=["break","break-range"],
39214 max_completions_reached="0"
39217 ^done,completion="b ma",
39218 matches=["b madvise","b main"],max_completions_reached="0"
39220 -complete "b push_b"
39221 ^done,completion="b push_back(",
39223 "b A::push_back(void*)",
39224 "b std::string::push_back(char)",
39225 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
39226 max_completions_reached="0"
39228 -complete "nonexist"
39229 ^done,matches=[],max_completions_reached="0"
39235 @chapter @value{GDBN} Annotations
39237 This chapter describes annotations in @value{GDBN}. Annotations were
39238 designed to interface @value{GDBN} to graphical user interfaces or other
39239 similar programs which want to interact with @value{GDBN} at a
39240 relatively high level.
39242 The annotation mechanism has largely been superseded by @sc{gdb/mi}
39246 This is Edition @value{EDITION}, @value{DATE}.
39250 * Annotations Overview:: What annotations are; the general syntax.
39251 * Server Prefix:: Issuing a command without affecting user state.
39252 * Prompting:: Annotations marking @value{GDBN}'s need for input.
39253 * Errors:: Annotations for error messages.
39254 * Invalidation:: Some annotations describe things now invalid.
39255 * Annotations for Running::
39256 Whether the program is running, how it stopped, etc.
39257 * Source Annotations:: Annotations describing source code.
39260 @node Annotations Overview
39261 @section What is an Annotation?
39262 @cindex annotations
39264 Annotations start with a newline character, two @samp{control-z}
39265 characters, and the name of the annotation. If there is no additional
39266 information associated with this annotation, the name of the annotation
39267 is followed immediately by a newline. If there is additional
39268 information, the name of the annotation is followed by a space, the
39269 additional information, and a newline. The additional information
39270 cannot contain newline characters.
39272 Any output not beginning with a newline and two @samp{control-z}
39273 characters denotes literal output from @value{GDBN}. Currently there is
39274 no need for @value{GDBN} to output a newline followed by two
39275 @samp{control-z} characters, but if there was such a need, the
39276 annotations could be extended with an @samp{escape} annotation which
39277 means those three characters as output.
39279 The annotation @var{level}, which is specified using the
39280 @option{--annotate} command line option (@pxref{Mode Options}), controls
39281 how much information @value{GDBN} prints together with its prompt,
39282 values of expressions, source lines, and other types of output. Level 0
39283 is for no annotations, level 1 is for use when @value{GDBN} is run as a
39284 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
39285 for programs that control @value{GDBN}, and level 2 annotations have
39286 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
39287 Interface, annotate, GDB's Obsolete Annotations}).
39290 @kindex set annotate
39291 @item set annotate @var{level}
39292 The @value{GDBN} command @code{set annotate} sets the level of
39293 annotations to the specified @var{level}.
39295 @item show annotate
39296 @kindex show annotate
39297 Show the current annotation level.
39300 This chapter describes level 3 annotations.
39302 A simple example of starting up @value{GDBN} with annotations is:
39305 $ @kbd{gdb --annotate=3}
39307 Copyright 2003 Free Software Foundation, Inc.
39308 GDB is free software, covered by the GNU General Public License,
39309 and you are welcome to change it and/or distribute copies of it
39310 under certain conditions.
39311 Type "show copying" to see the conditions.
39312 There is absolutely no warranty for GDB. Type "show warranty"
39314 This GDB was configured as "i386-pc-linux-gnu"
39325 Here @samp{quit} is input to @value{GDBN}; the rest is output from
39326 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
39327 denotes a @samp{control-z} character) are annotations; the rest is
39328 output from @value{GDBN}.
39330 @node Server Prefix
39331 @section The Server Prefix
39332 @cindex server prefix
39334 If you prefix a command with @samp{server } then it will not affect
39335 the command history, nor will it affect @value{GDBN}'s notion of which
39336 command to repeat if @key{RET} is pressed on a line by itself. This
39337 means that commands can be run behind a user's back by a front-end in
39338 a transparent manner.
39340 The @code{server } prefix does not affect the recording of values into
39341 the value history; to print a value without recording it into the
39342 value history, use the @code{output} command instead of the
39343 @code{print} command.
39345 Using this prefix also disables confirmation requests
39346 (@pxref{confirmation requests}).
39349 @section Annotation for @value{GDBN} Input
39351 @cindex annotations for prompts
39352 When @value{GDBN} prompts for input, it annotates this fact so it is possible
39353 to know when to send output, when the output from a given command is
39356 Different kinds of input each have a different @dfn{input type}. Each
39357 input type has three annotations: a @code{pre-} annotation, which
39358 denotes the beginning of any prompt which is being output, a plain
39359 annotation, which denotes the end of the prompt, and then a @code{post-}
39360 annotation which denotes the end of any echo which may (or may not) be
39361 associated with the input. For example, the @code{prompt} input type
39362 features the following annotations:
39370 The input types are
39373 @findex pre-prompt annotation
39374 @findex prompt annotation
39375 @findex post-prompt annotation
39377 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
39379 @findex pre-commands annotation
39380 @findex commands annotation
39381 @findex post-commands annotation
39383 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
39384 command. The annotations are repeated for each command which is input.
39386 @findex pre-overload-choice annotation
39387 @findex overload-choice annotation
39388 @findex post-overload-choice annotation
39389 @item overload-choice
39390 When @value{GDBN} wants the user to select between various overloaded functions.
39392 @findex pre-query annotation
39393 @findex query annotation
39394 @findex post-query annotation
39396 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
39398 @findex pre-prompt-for-continue annotation
39399 @findex prompt-for-continue annotation
39400 @findex post-prompt-for-continue annotation
39401 @item prompt-for-continue
39402 When @value{GDBN} is asking the user to press return to continue. Note: Don't
39403 expect this to work well; instead use @code{set height 0} to disable
39404 prompting. This is because the counting of lines is buggy in the
39405 presence of annotations.
39410 @cindex annotations for errors, warnings and interrupts
39412 @findex quit annotation
39417 This annotation occurs right before @value{GDBN} responds to an interrupt.
39419 @findex error annotation
39424 This annotation occurs right before @value{GDBN} responds to an error.
39426 Quit and error annotations indicate that any annotations which @value{GDBN} was
39427 in the middle of may end abruptly. For example, if a
39428 @code{value-history-begin} annotation is followed by a @code{error}, one
39429 cannot expect to receive the matching @code{value-history-end}. One
39430 cannot expect not to receive it either, however; an error annotation
39431 does not necessarily mean that @value{GDBN} is immediately returning all the way
39434 @findex error-begin annotation
39435 A quit or error annotation may be preceded by
39441 Any output between that and the quit or error annotation is the error
39444 Warning messages are not yet annotated.
39445 @c If we want to change that, need to fix warning(), type_error(),
39446 @c range_error(), and possibly other places.
39449 @section Invalidation Notices
39451 @cindex annotations for invalidation messages
39452 The following annotations say that certain pieces of state may have
39456 @findex frames-invalid annotation
39457 @item ^Z^Zframes-invalid
39459 The frames (for example, output from the @code{backtrace} command) may
39462 @findex breakpoints-invalid annotation
39463 @item ^Z^Zbreakpoints-invalid
39465 The breakpoints may have changed. For example, the user just added or
39466 deleted a breakpoint.
39469 @node Annotations for Running
39470 @section Running the Program
39471 @cindex annotations for running programs
39473 @findex starting annotation
39474 @findex stopping annotation
39475 When the program starts executing due to a @value{GDBN} command such as
39476 @code{step} or @code{continue},
39482 is output. When the program stops,
39488 is output. Before the @code{stopped} annotation, a variety of
39489 annotations describe how the program stopped.
39492 @findex exited annotation
39493 @item ^Z^Zexited @var{exit-status}
39494 The program exited, and @var{exit-status} is the exit status (zero for
39495 successful exit, otherwise nonzero).
39497 @findex signalled annotation
39498 @findex signal-name annotation
39499 @findex signal-name-end annotation
39500 @findex signal-string annotation
39501 @findex signal-string-end annotation
39502 @item ^Z^Zsignalled
39503 The program exited with a signal. After the @code{^Z^Zsignalled}, the
39504 annotation continues:
39510 ^Z^Zsignal-name-end
39514 ^Z^Zsignal-string-end
39519 where @var{name} is the name of the signal, such as @code{SIGILL} or
39520 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
39521 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
39522 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
39523 user's benefit and have no particular format.
39525 @findex signal annotation
39527 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
39528 just saying that the program received the signal, not that it was
39529 terminated with it.
39531 @findex breakpoint annotation
39532 @item ^Z^Zbreakpoint @var{number}
39533 The program hit breakpoint number @var{number}.
39535 @findex watchpoint annotation
39536 @item ^Z^Zwatchpoint @var{number}
39537 The program hit watchpoint number @var{number}.
39540 @node Source Annotations
39541 @section Displaying Source
39542 @cindex annotations for source display
39544 @findex source annotation
39545 The following annotation is used instead of displaying source code:
39548 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
39551 where @var{filename} is an absolute file name indicating which source
39552 file, @var{line} is the line number within that file (where 1 is the
39553 first line in the file), @var{character} is the character position
39554 within the file (where 0 is the first character in the file) (for most
39555 debug formats this will necessarily point to the beginning of a line),
39556 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
39557 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
39558 @var{addr} is the address in the target program associated with the
39559 source which is being displayed. The @var{addr} is in the form @samp{0x}
39560 followed by one or more lowercase hex digits (note that this does not
39561 depend on the language).
39563 @node Debugger Adapter Protocol
39564 @chapter Debugger Adapter Protocol
39566 The Debugger Adapter Protocol is a generic API that is used by some
39567 IDEs to communicate with debuggers. It is documented at
39568 @url{https://microsoft.github.io/debug-adapter-protocol/}.
39570 Generally, @value{GDBN} implements the Debugger Adapter Protocol as
39571 written. However, in some cases, extensions are either needed or even
39574 @value{GDBN} defines some parameters that can be passed to the
39575 @code{launch} request:
39579 If provided, this should be an array of strings. These strings are
39580 provided as command-line arguments to the inferior, as if by
39581 @code{set args}. @xref{Arguments}.
39584 If provided, this should be a string. @value{GDBN} will change its
39585 working directory to this directory, as if by the @code{cd} command
39586 (@pxref{Working Directory}). The launched program will inherit this
39587 as its working directory. Note that change of directory happens
39588 before the @code{program} parameter is processed. This will affect
39589 the result if @code{program} is a relative filename.
39592 If provided, this should be an object. Each key of the object will be
39593 used as the name of an environment variable; each value must be a
39594 string and will be the value of that variable. The environment of the
39595 inferior will be set to exactly as passed in. @xref{Environment}.
39598 If provided, this is a string that specifies the program to use. This
39599 corresponds to the @code{file} command. @xref{Files}.
39601 @item stopAtBeginningOfMainSubprogram
39602 If provided, this must be a boolean. When @samp{True}, @value{GDBN}
39603 will set a temporary breakpoint at the program's main procedure, using
39604 the same approach as the @code{start} command. @xref{Starting}.
39607 @value{GDBN} defines some parameters that can be passed to the
39608 @code{attach} request. Either @code{pid} or @code{target} must be
39609 specified, but if both are specified then @code{target} will be
39614 The process ID to which @value{GDBN} should attach. @xref{Attach}.
39617 If provided, this is a string that specifies the program to use. This
39618 corresponds to the @code{file} command. @xref{Files}. In some cases,
39619 @value{GDBN} can automatically determine which program is running.
39620 However, for many remote targets, this is not the case, and so this
39621 should be supplied.
39624 The target to which @value{GDBN} should connect. This is a string and
39625 is passed to the @code{target remote} command. @xref{Connecting}.
39628 In response to the @code{disassemble} request, DAP allows the client
39629 to return the bytes of each instruction in an implementation-defined
39630 format. @value{GDBN} implements this by sending a string with the
39631 bytes encoded in hex, like @code{"55a2b900"}.
39633 When the @code{repl} context is used for the @code{evaluate} request,
39634 @value{GDBN} evaluates the provided expression as a CLI command.
39636 Evaluation in general can cause the inferior to continue execution.
39637 For example, evaluating the @code{continue} command could do this, as
39638 could evaluating an expression that involves an inferior function
39641 @code{repl} evaluation can also cause @value{GDBN} to appear to stop
39642 responding to requests, for example if a CLI script does a lengthy
39645 Evaluations like this can be interrupted using the DAP @code{cancel}
39646 request. (In fact, @code{cancel} should work for any request, but it
39647 is unlikely to be useful for most of them.)
39649 @value{GDBN} provides a couple of logging settings that can be used in
39650 DAP mode. These can be set on the command line using the @code{-iex}
39651 option (@pxref{File Options}).
39654 @item set debug dap-log-file @r{[}@var{filename}@r{]}
39655 Enable DAP logging. Logs are written to @var{filename}. If no
39656 @var{filename} is given, logging is stopped.
39658 @item set debug dap-log-level @var{level}
39659 Set the DAP logging level. The default is @samp{1}, which logs the
39660 DAP protocol, whatever debug messages the developers thought were
39661 useful, and unexpected exceptions. Level @samp{2} can be used to log
39662 all exceptions, including ones that are considered to be expected.
39663 For example, a failure to parse an expression would be considered a
39664 normal exception and not normally be logged.
39667 @node JIT Interface
39668 @chapter JIT Compilation Interface
39669 @cindex just-in-time compilation
39670 @cindex JIT compilation interface
39672 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
39673 interface. A JIT compiler is a program or library that generates native
39674 executable code at runtime and executes it, usually in order to achieve good
39675 performance while maintaining platform independence.
39677 Programs that use JIT compilation are normally difficult to debug because
39678 portions of their code are generated at runtime, instead of being loaded from
39679 object files, which is where @value{GDBN} normally finds the program's symbols
39680 and debug information. In order to debug programs that use JIT compilation,
39681 @value{GDBN} has an interface that allows the program to register in-memory
39682 symbol files with @value{GDBN} at runtime.
39684 If you are using @value{GDBN} to debug a program that uses this interface, then
39685 it should work transparently so long as you have not stripped the binary. If
39686 you are developing a JIT compiler, then the interface is documented in the rest
39687 of this chapter. At this time, the only known client of this interface is the
39690 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
39691 JIT compiler communicates with @value{GDBN} by writing data into a global
39692 variable and calling a function at a well-known symbol. When @value{GDBN}
39693 attaches, it reads a linked list of symbol files from the global variable to
39694 find existing code, and puts a breakpoint in the function so that it can find
39695 out about additional code.
39698 * Declarations:: Relevant C struct declarations
39699 * Registering Code:: Steps to register code
39700 * Unregistering Code:: Steps to unregister code
39701 * Custom Debug Info:: Emit debug information in a custom format
39705 @section JIT Declarations
39707 These are the relevant struct declarations that a C program should include to
39708 implement the interface:
39718 struct jit_code_entry
39720 struct jit_code_entry *next_entry;
39721 struct jit_code_entry *prev_entry;
39722 const char *symfile_addr;
39723 uint64_t symfile_size;
39726 struct jit_descriptor
39729 /* This type should be jit_actions_t, but we use uint32_t
39730 to be explicit about the bitwidth. */
39731 uint32_t action_flag;
39732 struct jit_code_entry *relevant_entry;
39733 struct jit_code_entry *first_entry;
39736 /* GDB puts a breakpoint in this function. */
39737 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
39739 /* Make sure to specify the version statically, because the
39740 debugger may check the version before we can set it. */
39741 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
39744 If the JIT is multi-threaded, then it is important that the JIT synchronize any
39745 modifications to this global data properly, which can easily be done by putting
39746 a global mutex around modifications to these structures.
39748 @node Registering Code
39749 @section Registering Code
39751 To register code with @value{GDBN}, the JIT should follow this protocol:
39755 Generate an object file in memory with symbols and other desired debug
39756 information. The file must include the virtual addresses of the sections.
39759 Create a code entry for the file, which gives the start and size of the symbol
39763 Add it to the linked list in the JIT descriptor.
39766 Point the relevant_entry field of the descriptor at the entry.
39769 Set @code{action_flag} to @code{JIT_REGISTER} and call
39770 @code{__jit_debug_register_code}.
39773 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
39774 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
39775 new code. However, the linked list must still be maintained in order to allow
39776 @value{GDBN} to attach to a running process and still find the symbol files.
39778 @node Unregistering Code
39779 @section Unregistering Code
39781 If code is freed, then the JIT should use the following protocol:
39785 Remove the code entry corresponding to the code from the linked list.
39788 Point the @code{relevant_entry} field of the descriptor at the code entry.
39791 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
39792 @code{__jit_debug_register_code}.
39795 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
39796 and the JIT will leak the memory used for the associated symbol files.
39798 @node Custom Debug Info
39799 @section Custom Debug Info
39800 @cindex custom JIT debug info
39801 @cindex JIT debug info reader
39803 Generating debug information in platform-native file formats (like ELF
39804 or COFF) may be an overkill for JIT compilers; especially if all the
39805 debug info is used for is displaying a meaningful backtrace. The
39806 issue can be resolved by having the JIT writers decide on a debug info
39807 format and also provide a reader that parses the debug info generated
39808 by the JIT compiler. This section gives a brief overview on writing
39809 such a parser. More specific details can be found in the source file
39810 @file{gdb/jit-reader.in}, which is also installed as a header at
39811 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
39813 The reader is implemented as a shared object (so this functionality is
39814 not available on platforms which don't allow loading shared objects at
39815 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
39816 @code{jit-reader-unload} are provided, to be used to load and unload
39817 the readers from a preconfigured directory. Once loaded, the shared
39818 object is used the parse the debug information emitted by the JIT
39822 * Using JIT Debug Info Readers:: How to use supplied readers correctly
39823 * Writing JIT Debug Info Readers:: Creating a debug-info reader
39826 @node Using JIT Debug Info Readers
39827 @subsection Using JIT Debug Info Readers
39828 @kindex jit-reader-load
39829 @kindex jit-reader-unload
39831 Readers can be loaded and unloaded using the @code{jit-reader-load}
39832 and @code{jit-reader-unload} commands.
39835 @item jit-reader-load @var{reader}
39836 Load the JIT reader named @var{reader}, which is a shared
39837 object specified as either an absolute or a relative file name. In
39838 the latter case, @value{GDBN} will try to load the reader from a
39839 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
39840 system (here @var{libdir} is the system library directory, often
39841 @file{/usr/local/lib}).
39843 Only one reader can be active at a time; trying to load a second
39844 reader when one is already loaded will result in @value{GDBN}
39845 reporting an error. A new JIT reader can be loaded by first unloading
39846 the current one using @code{jit-reader-unload} and then invoking
39847 @code{jit-reader-load}.
39849 @item jit-reader-unload
39850 Unload the currently loaded JIT reader.
39854 @node Writing JIT Debug Info Readers
39855 @subsection Writing JIT Debug Info Readers
39856 @cindex writing JIT debug info readers
39858 As mentioned, a reader is essentially a shared object conforming to a
39859 certain ABI. This ABI is described in @file{jit-reader.h}.
39861 @file{jit-reader.h} defines the structures, macros and functions
39862 required to write a reader. It is installed (along with
39863 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
39864 the system include directory.
39866 Readers need to be released under a GPL compatible license. A reader
39867 can be declared as released under such a license by placing the macro
39868 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
39870 The entry point for readers is the symbol @code{gdb_init_reader},
39871 which is expected to be a function with the prototype
39873 @findex gdb_init_reader
39875 extern struct gdb_reader_funcs *gdb_init_reader (void);
39878 @cindex @code{struct gdb_reader_funcs}
39880 @code{struct gdb_reader_funcs} contains a set of pointers to callback
39881 functions. These functions are executed to read the debug info
39882 generated by the JIT compiler (@code{read}), to unwind stack frames
39883 (@code{unwind}) and to create canonical frame IDs
39884 (@code{get_frame_id}). It also has a callback that is called when the
39885 reader is being unloaded (@code{destroy}). The struct looks like this
39888 struct gdb_reader_funcs
39890 /* Must be set to GDB_READER_INTERFACE_VERSION. */
39891 int reader_version;
39893 /* For use by the reader. */
39896 gdb_read_debug_info *read;
39897 gdb_unwind_frame *unwind;
39898 gdb_get_frame_id *get_frame_id;
39899 gdb_destroy_reader *destroy;
39903 @cindex @code{struct gdb_symbol_callbacks}
39904 @cindex @code{struct gdb_unwind_callbacks}
39906 The callbacks are provided with another set of callbacks by
39907 @value{GDBN} to do their job. For @code{read}, these callbacks are
39908 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
39909 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
39910 @code{struct gdb_symbol_callbacks} has callbacks to create new object
39911 files and new symbol tables inside those object files. @code{struct
39912 gdb_unwind_callbacks} has callbacks to read registers off the current
39913 frame and to write out the values of the registers in the previous
39914 frame. Both have a callback (@code{target_read}) to read bytes off the
39915 target's address space.
39917 @node In-Process Agent
39918 @chapter In-Process Agent
39919 @cindex debugging agent
39920 The traditional debugging model is conceptually low-speed, but works fine,
39921 because most bugs can be reproduced in debugging-mode execution. However,
39922 as multi-core or many-core processors are becoming mainstream, and
39923 multi-threaded programs become more and more popular, there should be more
39924 and more bugs that only manifest themselves at normal-mode execution, for
39925 example, thread races, because debugger's interference with the program's
39926 timing may conceal the bugs. On the other hand, in some applications,
39927 it is not feasible for the debugger to interrupt the program's execution
39928 long enough for the developer to learn anything helpful about its behavior.
39929 If the program's correctness depends on its real-time behavior, delays
39930 introduced by a debugger might cause the program to fail, even when the
39931 code itself is correct. It is useful to be able to observe the program's
39932 behavior without interrupting it.
39934 Therefore, traditional debugging model is too intrusive to reproduce
39935 some bugs. In order to reduce the interference with the program, we can
39936 reduce the number of operations performed by debugger. The
39937 @dfn{In-Process Agent}, a shared library, is running within the same
39938 process with inferior, and is able to perform some debugging operations
39939 itself. As a result, debugger is only involved when necessary, and
39940 performance of debugging can be improved accordingly. Note that
39941 interference with program can be reduced but can't be removed completely,
39942 because the in-process agent will still stop or slow down the program.
39944 The in-process agent can interpret and execute Agent Expressions
39945 (@pxref{Agent Expressions}) during performing debugging operations. The
39946 agent expressions can be used for different purposes, such as collecting
39947 data in tracepoints, and condition evaluation in breakpoints.
39949 @anchor{Control Agent}
39950 You can control whether the in-process agent is used as an aid for
39951 debugging with the following commands:
39954 @kindex set agent on
39956 Causes the in-process agent to perform some operations on behalf of the
39957 debugger. Just which operations requested by the user will be done
39958 by the in-process agent depends on the its capabilities. For example,
39959 if you request to evaluate breakpoint conditions in the in-process agent,
39960 and the in-process agent has such capability as well, then breakpoint
39961 conditions will be evaluated in the in-process agent.
39963 @kindex set agent off
39964 @item set agent off
39965 Disables execution of debugging operations by the in-process agent. All
39966 of the operations will be performed by @value{GDBN}.
39970 Display the current setting of execution of debugging operations by
39971 the in-process agent.
39975 * In-Process Agent Protocol::
39978 @node In-Process Agent Protocol
39979 @section In-Process Agent Protocol
39980 @cindex in-process agent protocol
39982 The in-process agent is able to communicate with both @value{GDBN} and
39983 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
39984 used for communications between @value{GDBN} or GDBserver and the IPA.
39985 In general, @value{GDBN} or GDBserver sends commands
39986 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
39987 in-process agent replies back with the return result of the command, or
39988 some other information. The data sent to in-process agent is composed
39989 of primitive data types, such as 4-byte or 8-byte type, and composite
39990 types, which are called objects (@pxref{IPA Protocol Objects}).
39993 * IPA Protocol Objects::
39994 * IPA Protocol Commands::
39997 @node IPA Protocol Objects
39998 @subsection IPA Protocol Objects
39999 @cindex ipa protocol objects
40001 The commands sent to and results received from agent may contain some
40002 complex data types called @dfn{objects}.
40004 The in-process agent is running on the same machine with @value{GDBN}
40005 or GDBserver, so it doesn't have to handle as much differences between
40006 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
40007 However, there are still some differences of two ends in two processes:
40011 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
40012 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
40014 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
40015 GDBserver is compiled with one, and in-process agent is compiled with
40019 Here are the IPA Protocol Objects:
40023 agent expression object. It represents an agent expression
40024 (@pxref{Agent Expressions}).
40025 @anchor{agent expression object}
40027 tracepoint action object. It represents a tracepoint action
40028 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
40029 memory, static trace data and to evaluate expression.
40030 @anchor{tracepoint action object}
40032 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
40033 @anchor{tracepoint object}
40037 The following table describes important attributes of each IPA protocol
40040 @multitable @columnfractions .30 .20 .50
40041 @headitem Name @tab Size @tab Description
40042 @item @emph{agent expression object} @tab @tab
40043 @item length @tab 4 @tab length of bytes code
40044 @item byte code @tab @var{length} @tab contents of byte code
40045 @item @emph{tracepoint action for collecting memory} @tab @tab
40046 @item 'M' @tab 1 @tab type of tracepoint action
40047 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
40048 address of the lowest byte to collect, otherwise @var{addr} is the offset
40049 of @var{basereg} for memory collecting.
40050 @item len @tab 8 @tab length of memory for collecting
40051 @item basereg @tab 4 @tab the register number containing the starting
40052 memory address for collecting.
40053 @item @emph{tracepoint action for collecting registers} @tab @tab
40054 @item 'R' @tab 1 @tab type of tracepoint action
40055 @item @emph{tracepoint action for collecting static trace data} @tab @tab
40056 @item 'L' @tab 1 @tab type of tracepoint action
40057 @item @emph{tracepoint action for expression evaluation} @tab @tab
40058 @item 'X' @tab 1 @tab type of tracepoint action
40059 @item agent expression @tab length of @tab @ref{agent expression object}
40060 @item @emph{tracepoint object} @tab @tab
40061 @item number @tab 4 @tab number of tracepoint
40062 @item address @tab 8 @tab address of tracepoint inserted on
40063 @item type @tab 4 @tab type of tracepoint
40064 @item enabled @tab 1 @tab enable or disable of tracepoint
40065 @item step_count @tab 8 @tab step
40066 @item pass_count @tab 8 @tab pass
40067 @item numactions @tab 4 @tab number of tracepoint actions
40068 @item hit count @tab 8 @tab hit count
40069 @item trace frame usage @tab 8 @tab trace frame usage
40070 @item compiled_cond @tab 8 @tab compiled condition
40071 @item orig_size @tab 8 @tab orig size
40072 @item condition @tab 4 if condition is NULL otherwise length of
40073 @ref{agent expression object}
40074 @tab zero if condition is NULL, otherwise is
40075 @ref{agent expression object}
40076 @item actions @tab variable
40077 @tab numactions number of @ref{tracepoint action object}
40080 @node IPA Protocol Commands
40081 @subsection IPA Protocol Commands
40082 @cindex ipa protocol commands
40084 The spaces in each command are delimiters to ease reading this commands
40085 specification. They don't exist in real commands.
40089 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
40090 Installs a new fast tracepoint described by @var{tracepoint_object}
40091 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
40092 head of @dfn{jumppad}, which is used to jump to data collection routine
40097 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
40098 @var{target_address} is address of tracepoint in the inferior.
40099 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
40100 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
40101 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
40102 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
40109 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
40110 is about to kill inferiors.
40118 @item probe_marker_at:@var{address}
40119 Asks in-process agent to probe the marker at @var{address}.
40126 @item unprobe_marker_at:@var{address}
40127 Asks in-process agent to unprobe the marker at @var{address}.
40131 @chapter Reporting Bugs in @value{GDBN}
40132 @cindex bugs in @value{GDBN}
40133 @cindex reporting bugs in @value{GDBN}
40135 Your bug reports play an essential role in making @value{GDBN} reliable.
40137 Reporting a bug may help you by bringing a solution to your problem, or it
40138 may not. But in any case the principal function of a bug report is to help
40139 the entire community by making the next version of @value{GDBN} work better. Bug
40140 reports are your contribution to the maintenance of @value{GDBN}.
40142 In order for a bug report to serve its purpose, you must include the
40143 information that enables us to fix the bug.
40146 * Bug Criteria:: Have you found a bug?
40147 * Bug Reporting:: How to report bugs
40151 @section Have You Found a Bug?
40152 @cindex bug criteria
40154 If you are not sure whether you have found a bug, here are some guidelines:
40157 @cindex fatal signal
40158 @cindex debugger crash
40159 @cindex crash of debugger
40161 If the debugger gets a fatal signal, for any input whatever, that is a
40162 @value{GDBN} bug. Reliable debuggers never crash.
40164 @cindex error on valid input
40166 If @value{GDBN} produces an error message for valid input, that is a
40167 bug. (Note that if you're cross debugging, the problem may also be
40168 somewhere in the connection to the target.)
40170 @cindex invalid input
40172 If @value{GDBN} does not produce an error message for invalid input,
40173 that is a bug. However, you should note that your idea of
40174 ``invalid input'' might be our idea of ``an extension'' or ``support
40175 for traditional practice''.
40178 If you are an experienced user of debugging tools, your suggestions
40179 for improvement of @value{GDBN} are welcome in any case.
40182 @node Bug Reporting
40183 @section How to Report Bugs
40184 @cindex bug reports
40185 @cindex @value{GDBN} bugs, reporting
40187 A number of companies and individuals offer support for @sc{gnu} products.
40188 If you obtained @value{GDBN} from a support organization, we recommend you
40189 contact that organization first.
40191 You can find contact information for many support companies and
40192 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
40194 @c should add a web page ref...
40197 @ifset BUGURL_DEFAULT
40198 In any event, we also recommend that you submit bug reports for
40199 @value{GDBN}. The preferred method is to submit them directly using
40200 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
40201 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
40204 @strong{Do not send bug reports to @samp{info-gdb}, or to
40205 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
40206 not want to receive bug reports. Those that do have arranged to receive
40209 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
40210 serves as a repeater. The mailing list and the newsgroup carry exactly
40211 the same messages. Often people think of posting bug reports to the
40212 newsgroup instead of mailing them. This appears to work, but it has one
40213 problem which can be crucial: a newsgroup posting often lacks a mail
40214 path back to the sender. Thus, if we need to ask for more information,
40215 we may be unable to reach you. For this reason, it is better to send
40216 bug reports to the mailing list.
40218 @ifclear BUGURL_DEFAULT
40219 In any event, we also recommend that you submit bug reports for
40220 @value{GDBN} to @value{BUGURL}.
40224 The fundamental principle of reporting bugs usefully is this:
40225 @strong{report all the facts}. If you are not sure whether to state a
40226 fact or leave it out, state it!
40228 Often people omit facts because they think they know what causes the
40229 problem and assume that some details do not matter. Thus, you might
40230 assume that the name of the variable you use in an example does not matter.
40231 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
40232 stray memory reference which happens to fetch from the location where that
40233 name is stored in memory; perhaps, if the name were different, the contents
40234 of that location would fool the debugger into doing the right thing despite
40235 the bug. Play it safe and give a specific, complete example. That is the
40236 easiest thing for you to do, and the most helpful.
40238 Keep in mind that the purpose of a bug report is to enable us to fix the
40239 bug. It may be that the bug has been reported previously, but neither
40240 you nor we can know that unless your bug report is complete and
40243 Sometimes people give a few sketchy facts and ask, ``Does this ring a
40244 bell?'' Those bug reports are useless, and we urge everyone to
40245 @emph{refuse to respond to them} except to chide the sender to report
40248 To enable us to fix the bug, you should include all these things:
40252 The version of @value{GDBN}. @value{GDBN} announces it if you start
40253 with no arguments; you can also print it at any time using @code{show
40256 Without this, we will not know whether there is any point in looking for
40257 the bug in the current version of @value{GDBN}.
40260 The type of machine you are using, and the operating system name and
40264 The details of the @value{GDBN} build-time configuration.
40265 @value{GDBN} shows these details if you invoke it with the
40266 @option{--configuration} command-line option, or if you type
40267 @code{show configuration} at @value{GDBN}'s prompt.
40270 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
40271 ``@value{GCC}--2.8.1''.
40274 What compiler (and its version) was used to compile the program you are
40275 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
40276 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
40277 to get this information; for other compilers, see the documentation for
40281 The command arguments you gave the compiler to compile your example and
40282 observe the bug. For example, did you use @samp{-O}? To guarantee
40283 you will not omit something important, list them all. A copy of the
40284 Makefile (or the output from make) is sufficient.
40286 If we were to try to guess the arguments, we would probably guess wrong
40287 and then we might not encounter the bug.
40290 A complete input script, and all necessary source files, that will
40294 A description of what behavior you observe that you believe is
40295 incorrect. For example, ``It gets a fatal signal.''
40297 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
40298 will certainly notice it. But if the bug is incorrect output, we might
40299 not notice unless it is glaringly wrong. You might as well not give us
40300 a chance to make a mistake.
40302 Even if the problem you experience is a fatal signal, you should still
40303 say so explicitly. Suppose something strange is going on, such as, your
40304 copy of @value{GDBN} is out of synch, or you have encountered a bug in
40305 the C library on your system. (This has happened!) Your copy might
40306 crash and ours would not. If you told us to expect a crash, then when
40307 ours fails to crash, we would know that the bug was not happening for
40308 us. If you had not told us to expect a crash, then we would not be able
40309 to draw any conclusion from our observations.
40312 @cindex recording a session script
40313 To collect all this information, you can use a session recording program
40314 such as @command{script}, which is available on many Unix systems.
40315 Just run your @value{GDBN} session inside @command{script} and then
40316 include the @file{typescript} file with your bug report.
40318 Another way to record a @value{GDBN} session is to run @value{GDBN}
40319 inside Emacs and then save the entire buffer to a file.
40322 If you wish to suggest changes to the @value{GDBN} source, send us context
40323 diffs. If you even discuss something in the @value{GDBN} source, refer to
40324 it by context, not by line number.
40326 The line numbers in our development sources will not match those in your
40327 sources. Your line numbers would convey no useful information to us.
40331 Here are some things that are not necessary:
40335 A description of the envelope of the bug.
40337 Often people who encounter a bug spend a lot of time investigating
40338 which changes to the input file will make the bug go away and which
40339 changes will not affect it.
40341 This is often time consuming and not very useful, because the way we
40342 will find the bug is by running a single example under the debugger
40343 with breakpoints, not by pure deduction from a series of examples.
40344 We recommend that you save your time for something else.
40346 Of course, if you can find a simpler example to report @emph{instead}
40347 of the original one, that is a convenience for us. Errors in the
40348 output will be easier to spot, running under the debugger will take
40349 less time, and so on.
40351 However, simplification is not vital; if you do not want to do this,
40352 report the bug anyway and send us the entire test case you used.
40355 A patch for the bug.
40357 A patch for the bug does help us if it is a good one. But do not omit
40358 the necessary information, such as the test case, on the assumption that
40359 a patch is all we need. We might see problems with your patch and decide
40360 to fix the problem another way, or we might not understand it at all.
40362 Sometimes with a program as complicated as @value{GDBN} it is very hard to
40363 construct an example that will make the program follow a certain path
40364 through the code. If you do not send us the example, we will not be able
40365 to construct one, so we will not be able to verify that the bug is fixed.
40367 And if we cannot understand what bug you are trying to fix, or why your
40368 patch should be an improvement, we will not install it. A test case will
40369 help us to understand.
40372 A guess about what the bug is or what it depends on.
40374 Such guesses are usually wrong. Even we cannot guess right about such
40375 things without first using the debugger to find the facts.
40378 @c The readline documentation is distributed with the readline code
40379 @c and consists of the two following files:
40382 @c Use -I with makeinfo to point to the appropriate directory,
40383 @c environment var TEXINPUTS with TeX.
40384 @ifclear SYSTEM_READLINE
40385 @include rluser.texi
40386 @include hsuser.texi
40390 @appendix In Memoriam
40392 The @value{GDBN} project mourns the loss of the following long-time
40397 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
40398 to Free Software in general. Outside of @value{GDBN}, he was known in
40399 the Amiga world for his series of Fish Disks, and the GeekGadget project.
40401 @item Michael Snyder
40402 Michael was one of the Global Maintainers of the @value{GDBN} project,
40403 with contributions recorded as early as 1996, until 2011. In addition
40404 to his day to day participation, he was a large driving force behind
40405 adding Reverse Debugging to @value{GDBN}.
40408 Beyond their technical contributions to the project, they were also
40409 enjoyable members of the Free Software Community. We will miss them.
40411 @node Formatting Documentation
40412 @appendix Formatting Documentation
40414 @cindex @value{GDBN} reference card
40415 @cindex reference card
40416 The @value{GDBN} 4 release includes an already-formatted reference card, ready
40417 for printing with PostScript or Ghostscript, in the @file{gdb}
40418 subdirectory of the main source directory@footnote{In
40419 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
40420 release.}. If you can use PostScript or Ghostscript with your printer,
40421 you can print the reference card immediately with @file{refcard.ps}.
40423 The release also includes the source for the reference card. You
40424 can format it, using @TeX{}, by typing:
40430 The @value{GDBN} reference card is designed to print in @dfn{landscape}
40431 mode on US ``letter'' size paper;
40432 that is, on a sheet 11 inches wide by 8.5 inches
40433 high. You will need to specify this form of printing as an option to
40434 your @sc{dvi} output program.
40436 @cindex documentation
40438 All the documentation for @value{GDBN} comes as part of the machine-readable
40439 distribution. The documentation is written in Texinfo format, which is
40440 a documentation system that uses a single source file to produce both
40441 on-line information and a printed manual. You can use one of the Info
40442 formatting commands to create the on-line version of the documentation
40443 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
40445 @value{GDBN} includes an already formatted copy of the on-line Info
40446 version of this manual in the @file{gdb} subdirectory. The main Info
40447 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
40448 subordinate files matching @samp{gdb.info*} in the same directory. If
40449 necessary, you can print out these files, or read them with any editor;
40450 but they are easier to read using the @code{info} subsystem in @sc{gnu}
40451 Emacs or the standalone @code{info} program, available as part of the
40452 @sc{gnu} Texinfo distribution.
40454 If you want to format these Info files yourself, you need one of the
40455 Info formatting programs, such as @code{texinfo-format-buffer} or
40458 If you have @code{makeinfo} installed, and are in the top level
40459 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
40460 version @value{GDBVN}), you can make the Info file by typing:
40467 If you want to typeset and print copies of this manual, you need @TeX{},
40468 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
40469 Texinfo definitions file.
40471 @TeX{} is a typesetting program; it does not print files directly, but
40472 produces output files called @sc{dvi} files. To print a typeset
40473 document, you need a program to print @sc{dvi} files. If your system
40474 has @TeX{} installed, chances are it has such a program. The precise
40475 command to use depends on your system; @kbd{lpr -d} is common; another
40476 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
40477 require a file name without any extension or a @samp{.dvi} extension.
40479 @TeX{} also requires a macro definitions file called
40480 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
40481 written in Texinfo format. On its own, @TeX{} cannot either read or
40482 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
40483 and is located in the @file{gdb-@var{version-number}/texinfo}
40486 If you have @TeX{} and a @sc{dvi} printer program installed, you can
40487 typeset and print this manual. First switch to the @file{gdb}
40488 subdirectory of the main source directory (for example, to
40489 @file{gdb-@value{GDBVN}/gdb}) and type:
40495 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
40497 @node Installing GDB
40498 @appendix Installing @value{GDBN}
40499 @cindex installation
40502 * Requirements:: Requirements for building @value{GDBN}
40503 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
40504 * Separate Objdir:: Compiling @value{GDBN} in another directory
40505 * Config Names:: Specifying names for hosts and targets
40506 * Configure Options:: Summary of options for configure
40507 * System-wide configuration:: Having a system-wide init file
40511 @section Requirements for Building @value{GDBN}
40512 @cindex building @value{GDBN}, requirements for
40514 Building @value{GDBN} requires various tools and packages to be available.
40515 Other packages will be used only if they are found.
40517 @heading Tools/Packages Necessary for Building @value{GDBN}
40519 @item C@t{++}11 compiler
40520 @value{GDBN} is written in C@t{++}11. It should be buildable with any
40521 recent C@t{++}11 compiler, e.g.@: GCC.
40524 @value{GDBN}'s build system relies on features only found in the GNU
40525 make program. Other variants of @code{make} will not work.
40528 The following libraries are mandatory for building @value{GDBN}. The
40529 @file{configure} script searches for each of these libraries in
40530 several standard locations; if some library is installed in an unusual
40531 place, you can use either the @option{--with-@var{lib}}
40532 @file{configure} option to specify its installation directory, or
40533 the two separate options @option{---with-@var{library}-include} (to
40534 specify the location of its header files) and
40535 @option{--with-@var{library}-lib} (to specify the location of its
40536 libraries). For example, for the GMP library, the 3 options are
40537 @option{--with-gmp}, @option{--with-gmp-include}, and
40538 @option{--with-gmp-lib}. @xref{Configure Options}. We mention below
40539 the home site of each library, so that you could download and install
40540 them if your system doesn't already include them.
40543 @item GMP (The GNU Multiple Precision arithmetic library)
40544 @value{GDBN} uses GMP to perform some of its extended-precision
40545 arithmetics. The latest version of GMP is available from
40546 @url{https://gmplib.org/}.
40549 @item MPFR (The GNU Multiple-precision floating-point library)
40550 @value{GDBN} uses MPFR to emulate the target floating-point
40551 arithmetics during expression evaluation, if the target uses different
40552 floating-point formats than the host. The latest version of MPFR is
40553 available from @url{http://www.mpfr.org}.
40558 @heading Tools/Packages Optional for Building @value{GDBN}
40559 The tools/packages and libraries listed below are optional;
40560 @value{GDBN} can be build without them, at the expense of some run-time
40561 functionality that will be missing. As above, we list the home sites
40562 for each package/library, and the command-line options supported by
40563 the @file{configure} script to specify their installation directories
40564 if they are non-standard. In addition, for each package you can use
40565 the option @option{--with-@var{package}} to force @value{GDBN} to be
40566 compiled with the named @var{package}, and
40567 @option{--without-@var{package}} to disable building with it even if
40568 it is available. @xref{Configure Options}, for detailed description
40569 of the options to @file{configure}.
40573 @value{GDBN} can be scripted using Python language. @xref{Python}.
40574 The latest version is available from
40575 @url{https://www.python.org/downloads/}. Use the
40576 @option{--with-python=@var{dir}} to specify the non-standard directory
40577 where Python is installed.
40580 @value{GDBN} can also be scripted using GNU Guile. @xref{Guile}. The
40581 latest version can be found on
40582 @url{https://www.gnu.org/software/guile/download/}. If you have more
40583 than one version of Guile installed, use the
40584 @option{--with-guile=@var{guile-version}} to specify the Guile version
40585 to include in the build.
40589 If available, @value{GDBN} uses the Expat library for parsing XML
40590 files. @value{GDBN} uses XML files for the following functionalities:
40594 Remote protocol memory maps (@pxref{Memory Map Format})
40596 Target descriptions (@pxref{Target Descriptions})
40598 Remote shared library lists (@xref{Library List Format},
40599 or alternatively @pxref{Library List Format for SVR4 Targets})
40601 MS-Windows shared libraries (@pxref{Shared Libraries})
40603 Traceframe info (@pxref{Traceframe Info Format})
40605 Branch trace (@pxref{Branch Trace Format},
40606 @pxref{Branch Trace Configuration Format})
40609 The latest version of Expat is available from
40610 @url{http://expat.sourceforge.net}. Use the
40611 @option{--with-libexpat-prefix} to specify non-standard installation
40615 @value{GDBN}'s features related to character sets (@pxref{Character
40616 Sets}) require a functioning @code{iconv} implementation. If you are
40617 on a GNU system, then this is provided by the GNU C Library. Some
40618 other systems also provide a working @code{iconv}. Use the option
40619 @option{--with-iconv-bin} to specify where to find the @command{iconv}
40622 On systems without @code{iconv}, you can install the GNU Libiconv
40623 library; its latest version can be found on
40624 @url{https://ftp.gnu.org/pub/gnu/libiconv/} if your system doesn't
40625 provide it. Use the @option{--with-libiconv-prefix} option to
40626 @file{configure} to specify non-standard installation place for it.
40628 Alternatively, @value{GDBN}'s top-level @file{configure} and
40629 @file{Makefile} will arrange to build Libiconv if a directory named
40630 @file{libiconv} appears in the top-most source directory. If Libiconv
40631 is built this way, and if the operating system does not provide a
40632 suitable @code{iconv} implementation, then the just-built library will
40633 automatically be used by @value{GDBN}. One easy way to set this up is
40634 to download GNU Libiconv, unpack it inside the top-level directory of
40635 the @value{GDBN} source tree, and then rename the directory holding
40636 the Libiconv source code to @samp{libiconv}.
40638 @cindex compressed debug sections
40640 @value{GDBN} can support debugging sections that are compressed with
40641 the LZMA library. @xref{MiniDebugInfo}. If this library is not
40642 included with your operating system, you can find it in the xz package
40643 at @url{http://tukaani.org/xz/}. Use the
40644 @option{--with-liblzma-prefix} option to specify its non-standard
40648 @value{GDBN} will use the @samp{zlib} library, if available, to read
40649 compressed debug sections. Some linkers, such as GNU @command{gold},
40650 are capable of producing binaries with compressed debug sections. If
40651 @value{GDBN} is compiled with @samp{zlib}, it will be able to read the
40652 debug information in such binaries.
40654 The @samp{zlib} library is likely included with your operating system
40655 distribution; if it is not, you can get the latest version from
40656 @url{http://zlib.net}.
40658 @c FIXME: what about other optional libraries: debuginfod, zstd,
40659 @c libipt, babeltrace, xxhash, source-highlight?
40662 @node Running Configure
40663 @section Invoking the @value{GDBN} @file{configure} Script
40664 @cindex configuring @value{GDBN}
40665 @value{GDBN} comes with a @file{configure} script that automates the process
40666 of preparing @value{GDBN} for installation; you can then use @code{make} to
40667 build the @code{gdb} program.
40669 @c irrelevant in info file; it's as current as the code it lives with.
40670 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
40671 look at the @file{README} file in the sources; we may have improved the
40672 installation procedures since publishing this manual.}
40675 The @value{GDBN} distribution includes all the source code you need for
40676 @value{GDBN} in a single directory, whose name is usually composed by
40677 appending the version number to @samp{gdb}.
40679 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
40680 @file{gdb-@value{GDBVN}} directory. That directory contains:
40683 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
40684 script for configuring @value{GDBN} and all its supporting libraries
40686 @item gdb-@value{GDBVN}/gdb
40687 the source specific to @value{GDBN} itself
40689 @item gdb-@value{GDBVN}/bfd
40690 source for the Binary File Descriptor library
40692 @item gdb-@value{GDBVN}/include
40693 @sc{gnu} include files
40695 @item gdb-@value{GDBVN}/libiberty
40696 source for the @samp{-liberty} free software library
40698 @item gdb-@value{GDBVN}/opcodes
40699 source for the library of opcode tables and disassemblers
40701 @item gdb-@value{GDBVN}/readline
40702 source for the @sc{gnu} command-line interface
40705 There may be other subdirectories as well.
40707 The simplest way to configure and build @value{GDBN} is to run @file{configure}
40708 from the @file{gdb-@var{version-number}} source directory, which in
40709 this example is the @file{gdb-@value{GDBVN}} directory.
40711 First switch to the @file{gdb-@var{version-number}} source directory
40712 if you are not already in it; then run @file{configure}. Pass the
40713 identifier for the platform on which @value{GDBN} will run as an
40719 cd gdb-@value{GDBVN}
40724 Running @samp{configure} and then running @code{make} builds the
40725 included supporting libraries, then @code{gdb} itself. The configured
40726 source files, and the binaries, are left in the corresponding source
40730 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
40731 system does not recognize this automatically when you run a different
40732 shell, you may need to run @code{sh} on it explicitly:
40738 You should run the @file{configure} script from the top directory in the
40739 source tree, the @file{gdb-@var{version-number}} directory. If you run
40740 @file{configure} from one of the subdirectories, you will configure only
40741 that subdirectory. That is usually not what you want. In particular,
40742 if you run the first @file{configure} from the @file{gdb} subdirectory
40743 of the @file{gdb-@var{version-number}} directory, you will omit the
40744 configuration of @file{bfd}, @file{readline}, and other sibling
40745 directories of the @file{gdb} subdirectory. This leads to build errors
40746 about missing include files such as @file{bfd/bfd.h}.
40748 You can install @code{@value{GDBN}} anywhere. The best way to do this
40749 is to pass the @code{--prefix} option to @code{configure}, and then
40750 install it with @code{make install}.
40752 @node Separate Objdir
40753 @section Compiling @value{GDBN} in Another Directory
40755 If you want to run @value{GDBN} versions for several host or target machines,
40756 you need a different @code{gdb} compiled for each combination of
40757 host and target. @file{configure} is designed to make this easy by
40758 allowing you to generate each configuration in a separate subdirectory,
40759 rather than in the source directory. If your @code{make} program
40760 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
40761 @code{make} in each of these directories builds the @code{gdb}
40762 program specified there.
40764 To build @code{gdb} in a separate directory, run @file{configure}
40765 with the @samp{--srcdir} option to specify where to find the source.
40766 (You also need to specify a path to find @file{configure}
40767 itself from your working directory. If the path to @file{configure}
40768 would be the same as the argument to @samp{--srcdir}, you can leave out
40769 the @samp{--srcdir} option; it is assumed.)
40771 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
40772 separate directory for a Sun 4 like this:
40776 cd gdb-@value{GDBVN}
40779 ../gdb-@value{GDBVN}/configure
40784 When @file{configure} builds a configuration using a remote source
40785 directory, it creates a tree for the binaries with the same structure
40786 (and using the same names) as the tree under the source directory. In
40787 the example, you'd find the Sun 4 library @file{libiberty.a} in the
40788 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
40789 @file{gdb-sun4/gdb}.
40791 Make sure that your path to the @file{configure} script has just one
40792 instance of @file{gdb} in it. If your path to @file{configure} looks
40793 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
40794 one subdirectory of @value{GDBN}, not the whole package. This leads to
40795 build errors about missing include files such as @file{bfd/bfd.h}.
40797 One popular reason to build several @value{GDBN} configurations in separate
40798 directories is to configure @value{GDBN} for cross-compiling (where
40799 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
40800 programs that run on another machine---the @dfn{target}).
40801 You specify a cross-debugging target by
40802 giving the @samp{--target=@var{target}} option to @file{configure}.
40804 When you run @code{make} to build a program or library, you must run
40805 it in a configured directory---whatever directory you were in when you
40806 called @file{configure} (or one of its subdirectories).
40808 The @code{Makefile} that @file{configure} generates in each source
40809 directory also runs recursively. If you type @code{make} in a source
40810 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
40811 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
40812 will build all the required libraries, and then build GDB.
40814 When you have multiple hosts or targets configured in separate
40815 directories, you can run @code{make} on them in parallel (for example,
40816 if they are NFS-mounted on each of the hosts); they will not interfere
40820 @section Specifying Names for Hosts and Targets
40822 The specifications used for hosts and targets in the @file{configure}
40823 script are based on a three-part naming scheme, but some short predefined
40824 aliases are also supported. The full naming scheme encodes three pieces
40825 of information in the following pattern:
40828 @var{architecture}-@var{vendor}-@var{os}
40831 For example, you can use the alias @code{sun4} as a @var{host} argument,
40832 or as the value for @var{target} in a @code{--target=@var{target}}
40833 option. The equivalent full name is @samp{sparc-sun-sunos4}.
40835 The @file{configure} script accompanying @value{GDBN} does not provide
40836 any query facility to list all supported host and target names or
40837 aliases. @file{configure} calls the Bourne shell script
40838 @code{config.sub} to map abbreviations to full names; you can read the
40839 script, if you wish, or you can use it to test your guesses on
40840 abbreviations---for example:
40843 % sh config.sub i386-linux
40845 % sh config.sub alpha-linux
40846 alpha-unknown-linux-gnu
40847 % sh config.sub hp9k700
40849 % sh config.sub sun4
40850 sparc-sun-sunos4.1.1
40851 % sh config.sub sun3
40852 m68k-sun-sunos4.1.1
40853 % sh config.sub i986v
40854 Invalid configuration `i986v': machine `i986v' not recognized
40858 @code{config.sub} is also distributed in the @value{GDBN} source
40859 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
40861 @node Configure Options
40862 @section @file{configure} Options
40864 @c FIXME: This largely repeats what was already described in
40865 @c ``Requirements'', and OTOH doesn't describe the more fgine-granular
40866 @c options like --with-libexpat-prefix and --with-python-libdir.
40868 Here is a summary of the @file{configure} options and arguments that
40869 are most often useful for building @value{GDBN}. @file{configure}
40870 also has several other options not listed here. @xref{Running
40871 configure Scripts,,,autoconf}, for a full
40872 explanation of @file{configure}.
40875 configure @r{[}--help@r{]}
40876 @r{[}--prefix=@var{dir}@r{]}
40877 @r{[}--exec-prefix=@var{dir}@r{]}
40878 @r{[}--srcdir=@var{dirname}@r{]}
40879 @r{[}--target=@var{target}@r{]}
40883 You may introduce options with a single @samp{-} rather than
40884 @samp{--} if you prefer; but you may abbreviate option names if you use
40889 Display a quick summary of how to invoke @file{configure}.
40891 @item --prefix=@var{dir}
40892 Configure the source to install programs and files under directory
40895 @item --exec-prefix=@var{dir}
40896 Configure the source to install programs under directory
40899 @c avoid splitting the warning from the explanation:
40901 @item --srcdir=@var{dirname}
40902 Use this option to make configurations in directories separate from the
40903 @value{GDBN} source directories. Among other things, you can use this to
40904 build (or maintain) several configurations simultaneously, in separate
40905 directories. @file{configure} writes configuration-specific files in
40906 the current directory, but arranges for them to use the source in the
40907 directory @var{dirname}. @file{configure} creates directories under
40908 the working directory in parallel to the source directories below
40911 @item --target=@var{target}
40912 Configure @value{GDBN} for cross-debugging programs running on the specified
40913 @var{target}. Without this option, @value{GDBN} is configured to debug
40914 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
40916 There is no convenient way to generate a list of all available
40917 targets. Also see the @code{--enable-targets} option, below.
40920 There are many other options that are specific to @value{GDBN}. This
40921 lists just the most common ones; there are some very specialized
40922 options not described here.
40925 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
40926 @itemx --enable-targets=all
40927 Configure @value{GDBN} for cross-debugging programs running on the
40928 specified list of targets. The special value @samp{all} configures
40929 @value{GDBN} for debugging programs running on any target it supports.
40931 @item --with-gdb-datadir=@var{path}
40932 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
40933 here for certain supporting files or scripts. This defaults to the
40934 @file{gdb} subdirectory of @samp{datadir} (which can be set using
40937 @item --with-relocated-sources=@var{dir}
40938 Sets up the default source path substitution rule so that directory
40939 names recorded in debug information will be automatically adjusted for
40940 any directory under @var{dir}. @var{dir} should be a subdirectory of
40941 @value{GDBN}'s configured prefix, the one mentioned in the
40942 @code{--prefix} or @code{--exec-prefix} options to configure. This
40943 option is useful if GDB is supposed to be moved to a different place
40946 @item --enable-64-bit-bfd
40947 Enable 64-bit support in BFD on 32-bit hosts.
40949 @item --disable-gdbmi
40950 Build @value{GDBN} without the GDB/MI machine interface
40954 Build @value{GDBN} with the text-mode full-screen user interface
40955 (TUI). Requires a curses library (ncurses and cursesX are also
40958 @item --with-curses
40959 Use the curses library instead of the termcap library, for text-mode
40960 terminal operations.
40962 @item --with-debuginfod
40963 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
40964 library. Used to automatically fetch ELF, DWARF and source files from
40965 @code{debuginfod} servers using build IDs associated with any missing
40966 files. Enabled by default if @file{libdebuginfod} is installed and found
40967 at configure time. For more information regarding @code{debuginfod} see
40970 @item --with-libunwind-ia64
40971 Use the libunwind library for unwinding function call stack on ia64
40972 target platforms. See @url{http://www.nongnu.org/libunwind/index.html} for
40975 @item --with-system-readline
40976 Use the readline library installed on the host, rather than the
40977 library supplied as part of @value{GDBN}. Readline 7 or newer is
40978 required; this is enforced by the build system.
40980 @item --with-system-zlib
40981 Use the zlib library installed on the host, rather than the library
40982 supplied as part of @value{GDBN}.
40985 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
40986 default if libexpat is installed and found at configure time.) This
40987 library is used to read XML files supplied with @value{GDBN}. If it
40988 is unavailable, some features, such as remote protocol memory maps,
40989 target descriptions, and shared library lists, that are based on XML
40990 files, will not be available in @value{GDBN}. If your host does not
40991 have libexpat installed, you can get the latest version from
40992 @url{http://expat.sourceforge.net}.
40994 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
40995 Build @value{GDBN} with GNU libiconv, a character set encoding
40996 conversion library. This is not done by default, as on GNU systems
40997 the @code{iconv} that is built in to the C library is sufficient. If
40998 your host does not have a working @code{iconv}, you can get the latest
40999 version of GNU iconv from @url{https://www.gnu.org/software/libiconv/}.
41001 @value{GDBN}'s build system also supports building GNU libiconv as
41002 part of the overall build. @xref{Requirements}.
41005 Build @value{GDBN} with LZMA, a compression library. (Done by default
41006 if liblzma is installed and found at configure time.) LZMA is used by
41007 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
41008 platforms using the ELF object file format. If your host does not
41009 have liblzma installed, you can get the latest version from
41010 @url{https://tukaani.org/xz/}.
41012 @item --with-python@r{[}=@var{python}@r{]}
41013 Build @value{GDBN} with Python scripting support. (Done by default if
41014 libpython is present and found at configure time.) Python makes
41015 @value{GDBN} scripting much more powerful than the restricted CLI
41016 scripting language. If your host does not have Python installed, you
41017 can find it on @url{http://www.python.org/download/}. The oldest version
41018 of Python supported by GDB is 3.0.1. The optional argument @var{python}
41019 is used to find the Python headers and libraries. It can be either
41020 the name of a Python executable, or the name of the directory in which
41021 Python is installed.
41023 @item --with-guile[=@var{guile}]
41024 Build @value{GDBN} with GNU Guile scripting support. (Done by default
41025 if libguile is present and found at configure time.) If your host
41026 does not have Guile installed, you can find it at
41027 @url{https://www.gnu.org/software/guile/}. The optional argument @var{guile}
41028 can be a version number, which will cause @code{configure} to try to
41029 use that version of Guile; or the file name of a @code{pkg-config}
41030 executable, which will be queried to find the information needed to
41031 compile and link against Guile.
41033 @item --without-included-regex
41034 Don't use the regex library included with @value{GDBN} (as part of the
41035 libiberty library). This is the default on hosts with version 2 of
41038 @item --with-sysroot=@var{dir}
41039 Use @var{dir} as the default system root directory for libraries whose
41040 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
41041 @var{dir} can be modified at run time by using the @command{set
41042 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
41043 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
41044 default system root will be automatically adjusted if and when
41045 @value{GDBN} is moved to a different location.
41047 @item --with-system-gdbinit=@var{file}
41048 Configure @value{GDBN} to automatically load a system-wide init file.
41049 @var{file} should be an absolute file name. If @var{file} is in a
41050 directory under the configured prefix, and @value{GDBN} is moved to
41051 another location after being built, the location of the system-wide
41052 init file will be adjusted accordingly.
41054 @item --with-system-gdbinit-dir=@var{directory}
41055 Configure @value{GDBN} to automatically load init files from a
41056 system-wide directory. @var{directory} should be an absolute directory
41057 name. If @var{directory} is in a directory under the configured
41058 prefix, and @value{GDBN} is moved to another location after being
41059 built, the location of the system-wide init directory will be
41060 adjusted accordingly.
41062 @item --enable-build-warnings
41063 When building the @value{GDBN} sources, ask the compiler to warn about
41064 any code which looks even vaguely suspicious. It passes many
41065 different warning flags, depending on the exact version of the
41066 compiler you are using.
41068 @item --enable-werror
41069 Treat compiler warnings as errors. It adds the @code{-Werror} flag
41070 to the compiler, which will fail the compilation if the compiler
41071 outputs any warning messages.
41073 @item --enable-ubsan
41074 Enable the GCC undefined behavior sanitizer. This is disabled by
41075 default, but passing @code{--enable-ubsan=yes} or
41076 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
41077 undefined behavior sanitizer checks for C@t{++} undefined behavior.
41078 It has a performance cost, so if you are looking at @value{GDBN}'s
41079 performance, you should disable it. The undefined behavior sanitizer
41080 was first introduced in GCC 4.9.
41083 @node System-wide configuration
41084 @section System-wide configuration and settings
41085 @cindex system-wide init file
41087 @value{GDBN} can be configured to have a system-wide init file and a
41088 system-wide init file directory; this file and files in that directory
41089 (if they have a recognized file extension) will be read and executed at
41090 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
41092 Here are the corresponding configure options:
41095 @item --with-system-gdbinit=@var{file}
41096 Specify that the default location of the system-wide init file is
41098 @item --with-system-gdbinit-dir=@var{directory}
41099 Specify that the default location of the system-wide init file directory
41100 is @var{directory}.
41103 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
41104 they may be subject to relocation. Two possible cases:
41108 If the default location of this init file/directory contains @file{$prefix},
41109 it will be subject to relocation. Suppose that the configure options
41110 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
41111 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
41112 init file is looked for as @file{$install/etc/gdbinit} instead of
41113 @file{$prefix/etc/gdbinit}.
41116 By contrast, if the default location does not contain the prefix,
41117 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
41118 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
41119 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
41120 wherever @value{GDBN} is installed.
41123 If the configured location of the system-wide init file (as given by the
41124 @option{--with-system-gdbinit} option at configure time) is in the
41125 data-directory (as specified by @option{--with-gdb-datadir} at configure
41126 time) or in one of its subdirectories, then @value{GDBN} will look for the
41127 system-wide init file in the directory specified by the
41128 @option{--data-directory} command-line option.
41129 Note that the system-wide init file is only read once, during @value{GDBN}
41130 initialization. If the data-directory is changed after @value{GDBN} has
41131 started with the @code{set data-directory} command, the file will not be
41134 This applies similarly to the system-wide directory specified in
41135 @option{--with-system-gdbinit-dir}.
41137 Any supported scripting language can be used for these init files, as long
41138 as the file extension matches the scripting language. To be interpreted
41139 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
41143 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
41146 @node System-wide Configuration Scripts
41147 @subsection Installed System-wide Configuration Scripts
41148 @cindex system-wide configuration scripts
41150 The @file{system-gdbinit} directory, located inside the data-directory
41151 (as specified by @option{--with-gdb-datadir} at configure time) contains
41152 a number of scripts which can be used as system-wide init files. To
41153 automatically source those scripts at startup, @value{GDBN} should be
41154 configured with @option{--with-system-gdbinit}. Otherwise, any user
41155 should be able to source them by hand as needed.
41157 The following scripts are currently available:
41160 @item @file{elinos.py}
41162 @cindex ELinOS system-wide configuration script
41163 This script is useful when debugging a program on an ELinOS target.
41164 It takes advantage of the environment variables defined in a standard
41165 ELinOS environment in order to determine the location of the system
41166 shared libraries, and then sets the @samp{solib-absolute-prefix}
41167 and @samp{solib-search-path} variables appropriately.
41169 @item @file{wrs-linux.py}
41170 @pindex wrs-linux.py
41171 @cindex Wind River Linux system-wide configuration script
41172 This script is useful when debugging a program on a target running
41173 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
41174 the host-side sysroot used by the target system.
41178 @node Maintenance Commands
41179 @appendix Maintenance Commands
41180 @cindex maintenance commands
41181 @cindex internal commands
41183 In addition to commands intended for @value{GDBN} users, @value{GDBN}
41184 includes a number of commands intended for @value{GDBN} developers,
41185 that are not documented elsewhere in this manual. These commands are
41186 provided here for reference. (For commands that turn on debugging
41187 messages, see @ref{Debugging Output}.)
41190 @kindex maint agent
41191 @kindex maint agent-eval
41192 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
41193 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
41194 Translate the given @var{expression} into remote agent bytecodes.
41195 This command is useful for debugging the Agent Expression mechanism
41196 (@pxref{Agent Expressions}). The @samp{agent} version produces an
41197 expression useful for data collection, such as by tracepoints, while
41198 @samp{maint agent-eval} produces an expression that evaluates directly
41199 to a result. For instance, a collection expression for @code{globa +
41200 globb} will include bytecodes to record four bytes of memory at each
41201 of the addresses of @code{globa} and @code{globb}, while discarding
41202 the result of the addition, while an evaluation expression will do the
41203 addition and return the sum.
41204 If @code{-at} is given, generate remote agent bytecode for all the
41205 addresses to which @var{linespec} resolves (@pxref{Linespec
41207 If not, generate remote agent bytecode for current frame PC address.
41209 @kindex maint agent-printf
41210 @item maint agent-printf @var{format},@var{expr},...
41211 Translate the given format string and list of argument expressions
41212 into remote agent bytecodes and display them as a disassembled list.
41213 This command is useful for debugging the agent version of dynamic
41214 printf (@pxref{Dynamic Printf}).
41216 @kindex maint info breakpoints
41217 @item @anchor{maint info breakpoints}maint info breakpoints
41218 Using the same format as @samp{info breakpoints}, display both the
41219 breakpoints you've set explicitly, and those @value{GDBN} is using for
41220 internal purposes. Internal breakpoints are shown with negative
41221 breakpoint numbers. The type column identifies what kind of breakpoint
41226 Normal, explicitly set breakpoint.
41229 Normal, explicitly set watchpoint.
41232 Internal breakpoint, used to handle correctly stepping through
41233 @code{longjmp} calls.
41235 @item longjmp resume
41236 Internal breakpoint at the target of a @code{longjmp}.
41239 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
41242 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
41245 Shared library events.
41249 @kindex maint info btrace
41250 @item maint info btrace
41251 Pint information about raw branch tracing data.
41253 @kindex maint btrace packet-history
41254 @item maint btrace packet-history
41255 Print the raw branch trace packets that are used to compute the
41256 execution history for the @samp{record btrace} command. Both the
41257 information and the format in which it is printed depend on the btrace
41262 For the BTS recording format, print a list of blocks of sequential
41263 code. For each block, the following information is printed:
41267 Newer blocks have higher numbers. The oldest block has number zero.
41268 @item Lowest @samp{PC}
41269 @item Highest @samp{PC}
41273 For the Intel Processor Trace recording format, print a list of
41274 Intel Processor Trace packets. For each packet, the following
41275 information is printed:
41278 @item Packet number
41279 Newer packets have higher numbers. The oldest packet has number zero.
41281 The packet's offset in the trace stream.
41282 @item Packet opcode and payload
41286 @kindex maint btrace clear-packet-history
41287 @item maint btrace clear-packet-history
41288 Discards the cached packet history printed by the @samp{maint btrace
41289 packet-history} command. The history will be computed again when
41292 @kindex maint btrace clear
41293 @item maint btrace clear
41294 Discard the branch trace data. The data will be fetched anew and the
41295 branch trace will be recomputed when needed.
41297 This implicitly truncates the branch trace to a single branch trace
41298 buffer. When updating branch trace incrementally, the branch trace
41299 available to @value{GDBN} may be bigger than a single branch trace
41302 @kindex maint set btrace pt skip-pad
41303 @item maint set btrace pt skip-pad
41304 @kindex maint show btrace pt skip-pad
41305 @item maint show btrace pt skip-pad
41306 Control whether @value{GDBN} will skip PAD packets when computing the
41309 @kindex maint info jit
41310 @item maint info jit
41311 Print information about JIT code objects loaded in the current inferior.
41313 @anchor{maint info python-disassemblers}
41314 @kindex maint info python-disassemblers
41315 @item maint info python-disassemblers
41316 This command is defined within the @code{gdb.disassembler} Python
41317 module (@pxref{Disassembly In Python}), and will only be present after
41318 that module has been imported. To force the module to be imported do
41321 @kindex maint info linux-lwps
41322 @item maint info linux-lwps
41323 Print information about LWPs under control of the Linux native target.
41326 (@value{GDBP}) python import gdb.disassembler
41329 This command lists all the architectures for which a disassembler is
41330 currently registered, and the name of the disassembler. If a
41331 disassembler is registered for all architectures, then this is listed
41332 last against the @samp{GLOBAL} architecture.
41334 If one of the disassemblers would be selected for the architecture of
41335 the current inferior, then this disassembler will be marked.
41337 The following example shows a situation in which two disassemblers are
41338 registered, initially the @samp{i386} disassembler matches the current
41339 architecture, then the architecture is changed, now the @samp{GLOBAL}
41340 disassembler matches.
41344 (@value{GDBP}) show architecture
41345 The target architecture is set to "auto" (currently "i386").
41346 (@value{GDBP}) maint info python-disassemblers
41347 Architecture Disassember Name
41348 i386 Disassembler_1 (Matches current architecture)
41349 GLOBAL Disassembler_2
41352 (@value{GDBP}) set architecture arm
41353 The target architecture is set to "arm".
41354 (@value{GDBP}) maint info python-disassemblers
41356 Architecture Disassember Name
41357 i386 Disassembler_1
41358 GLOBAL Disassembler_2 (Matches current architecture)
41362 @kindex set displaced-stepping
41363 @kindex show displaced-stepping
41364 @cindex displaced stepping support
41365 @cindex out-of-line single-stepping
41366 @item set displaced-stepping
41367 @itemx show displaced-stepping
41368 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
41369 if the target supports it. Displaced stepping is a way to single-step
41370 over breakpoints without removing them from the inferior, by executing
41371 an out-of-line copy of the instruction that was originally at the
41372 breakpoint location. It is also known as out-of-line single-stepping.
41375 @item set displaced-stepping on
41376 If the target architecture supports it, @value{GDBN} will use
41377 displaced stepping to step over breakpoints.
41379 @item set displaced-stepping off
41380 @value{GDBN} will not use displaced stepping to step over breakpoints,
41381 even if such is supported by the target architecture.
41383 @cindex non-stop mode, and @samp{set displaced-stepping}
41384 @item set displaced-stepping auto
41385 This is the default mode. @value{GDBN} will use displaced stepping
41386 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
41387 architecture supports displaced stepping.
41390 @kindex maint check-psymtabs
41391 @item maint check-psymtabs
41392 Check the consistency of currently expanded psymtabs versus symtabs.
41393 Use this to check, for example, whether a symbol is in one but not the other.
41395 @kindex maint check-symtabs
41396 @item maint check-symtabs
41397 Check the consistency of currently expanded symtabs.
41399 @kindex maint expand-symtabs
41400 @item maint expand-symtabs [@var{regexp}]
41401 Expand symbol tables.
41402 If @var{regexp} is specified, only expand symbol tables for file
41403 names matching @var{regexp}.
41405 @kindex maint set catch-demangler-crashes
41406 @kindex maint show catch-demangler-crashes
41407 @cindex demangler crashes
41408 @item maint set catch-demangler-crashes [on|off]
41409 @itemx maint show catch-demangler-crashes
41410 Control whether @value{GDBN} should attempt to catch crashes in the
41411 symbol name demangler. The default is to attempt to catch crashes.
41412 If enabled, the first time a crash is caught, a core file is created,
41413 the offending symbol is displayed and the user is presented with the
41414 option to terminate the current session.
41416 @kindex maint cplus first_component
41417 @item maint cplus first_component @var{name}
41418 Print the first C@t{++} class/namespace component of @var{name}.
41420 @kindex maint cplus namespace
41421 @item maint cplus namespace
41422 Print the list of possible C@t{++} namespaces.
41424 @kindex maint deprecate
41425 @kindex maint undeprecate
41426 @cindex deprecated commands
41427 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
41428 @itemx maint undeprecate @var{command}
41429 Deprecate or undeprecate the named @var{command}. Deprecated commands
41430 cause @value{GDBN} to issue a warning when you use them. The optional
41431 argument @var{replacement} says which newer command should be used in
41432 favor of the deprecated one; if it is given, @value{GDBN} will mention
41433 the replacement as part of the warning.
41435 @kindex maint dump-me
41436 @item maint dump-me
41437 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
41438 Cause a fatal signal in the debugger and force it to dump its core.
41439 This is supported only on systems which support aborting a program
41440 with the @code{SIGQUIT} signal.
41442 @kindex maint internal-error
41443 @kindex maint internal-warning
41444 @kindex maint demangler-warning
41445 @cindex demangler crashes
41446 @item maint internal-error @r{[}@var{message-text}@r{]}
41447 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
41448 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
41450 Cause @value{GDBN} to call the internal function @code{internal_error},
41451 @code{internal_warning} or @code{demangler_warning} and hence behave
41452 as though an internal problem has been detected. In addition to
41453 reporting the internal problem, these functions give the user the
41454 opportunity to either quit @value{GDBN} or (for @code{internal_error}
41455 and @code{internal_warning}) create a core file of the current
41456 @value{GDBN} session.
41458 These commands take an optional parameter @var{message-text} that is
41459 used as the text of the error or warning message.
41461 Here's an example of using @code{internal-error}:
41464 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
41465 @dots{}/maint.c:121: internal-error: testing, 1, 2
41466 A problem internal to GDB has been detected. Further
41467 debugging may prove unreliable.
41468 Quit this debugging session? (y or n) @kbd{n}
41469 Create a core file? (y or n) @kbd{n}
41473 @kindex maint set debuginfod download-sections
41474 @kindex maint show debuginfod download-sections
41475 @cindex debuginfod, maintenance commands
41476 @item maint set debuginfod download-sections
41477 @itemx maint set debuginfod download-sections @r{[}on|off@r{]}
41478 @itemx maint show debuginfod download-sections
41479 Controls whether @value{GDBN} will attempt to download individual
41480 ELF/DWARF sections from @code{debuginfod}. If disabled, only
41481 whole debug info files will be downloaded; this could result
41482 in @value{GDBN} downloading larger amounts of data.
41484 @cindex @value{GDBN} internal error
41485 @cindex internal errors, control of @value{GDBN} behavior
41486 @cindex demangler crashes
41488 @kindex maint set internal-error
41489 @kindex maint show internal-error
41490 @kindex maint set internal-warning
41491 @kindex maint show internal-warning
41492 @kindex maint set demangler-warning
41493 @kindex maint show demangler-warning
41494 @item maint set internal-error @var{action} [ask|yes|no]
41495 @itemx maint show internal-error @var{action}
41496 @itemx maint set internal-warning @var{action} [ask|yes|no]
41497 @itemx maint show internal-warning @var{action}
41498 @itemx maint set demangler-warning @var{action} [ask|yes|no]
41499 @itemx maint show demangler-warning @var{action}
41500 When @value{GDBN} reports an internal problem (error or warning) it
41501 gives the user the opportunity to both quit @value{GDBN} and create a
41502 core file of the current @value{GDBN} session. These commands let you
41503 override the default behaviour for each particular @var{action},
41504 described in the table below.
41508 You can specify that @value{GDBN} should always (yes) or never (no)
41509 quit. The default is to ask the user what to do.
41512 You can specify that @value{GDBN} should always (yes) or never (no)
41513 create a core file. The default is to ask the user what to do. Note
41514 that there is no @code{corefile} option for @code{demangler-warning}:
41515 demangler warnings always create a core file and this cannot be
41519 @kindex maint set internal-error
41520 @kindex maint show internal-error
41521 @kindex maint set internal-warning
41522 @kindex maint show internal-warning
41523 @item maint set internal-error backtrace @r{[}on|off@r{]}
41524 @itemx maint show internal-error backtrace
41525 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
41526 @itemx maint show internal-warning backtrace
41527 When @value{GDBN} reports an internal problem (error or warning) it is
41528 possible to have a backtrace of @value{GDBN} printed to the standard
41529 error stream. This is @samp{on} by default for @code{internal-error}
41530 and @samp{off} by default for @code{internal-warning}.
41532 @anchor{maint packet}
41533 @kindex maint packet
41534 @item maint packet @var{text}
41535 If @value{GDBN} is talking to an inferior via the serial protocol,
41536 then this command sends the string @var{text} to the inferior, and
41537 displays the response packet. @value{GDBN} supplies the initial
41538 @samp{$} character, the terminating @samp{#} character, and the
41541 Any non-printable characters in the reply are printed as escaped hex,
41542 e.g. @samp{\x00}, @samp{\x01}, etc.
41544 @kindex maint print architecture
41545 @item maint print architecture @r{[}@var{file}@r{]}
41546 Print the entire architecture configuration. The optional argument
41547 @var{file} names the file where the output goes.
41549 @kindex maint print c-tdesc
41550 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
41551 Print the target description (@pxref{Target Descriptions}) as
41552 a C source file. By default, the target description is for the current
41553 target, but if the optional argument @var{file} is provided, that file
41554 is used to produce the description. The @var{file} should be an XML
41555 document, of the form described in @ref{Target Description Format}.
41556 The created source file is built into @value{GDBN} when @value{GDBN} is
41557 built again. This command is used by developers after they add or
41558 modify XML target descriptions.
41560 When the optional flag @samp{-single-feature} is provided then the
41561 target description being processed (either the default, or from
41562 @var{file}) must only contain a single feature. The source file
41563 produced is different in this case.
41565 @kindex maint print xml-tdesc
41566 @item maint print xml-tdesc @r{[}@var{file}@r{]}
41567 Print the target description (@pxref{Target Descriptions}) as an XML
41568 file. By default print the target description for the current target,
41569 but if the optional argument @var{file} is provided, then that file is
41570 read in by GDB and then used to produce the description. The
41571 @var{file} should be an XML document, of the form described in
41572 @ref{Target Description Format}.
41574 @kindex maint check xml-descriptions
41575 @item maint check xml-descriptions @var{dir}
41576 Check that the target descriptions dynamically created by @value{GDBN}
41577 equal the descriptions created from XML files found in @var{dir}.
41579 @anchor{maint check libthread-db}
41580 @kindex maint check libthread-db
41581 @item maint check libthread-db
41582 Run integrity checks on the current inferior's thread debugging
41583 library. This exercises all @code{libthread_db} functionality used by
41584 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
41585 @code{proc_service} functions provided by @value{GDBN} that
41586 @code{libthread_db} uses. Note that parts of the test may be skipped
41587 on some platforms when debugging core files.
41589 @kindex maint print core-file-backed-mappings
41590 @cindex memory address space mappings
41591 @item maint print core-file-backed-mappings
41592 Print the file-backed mappings which were loaded from a core file note.
41593 This output represents state internal to @value{GDBN} and should be
41594 similar to the mappings displayed by the @code{info proc mappings}
41597 @kindex maint print dummy-frames
41598 @item maint print dummy-frames
41599 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
41602 (@value{GDBP}) @kbd{b add}
41604 (@value{GDBP}) @kbd{print add(2,3)}
41605 Breakpoint 2, add (a=2, b=3) at @dots{}
41607 The program being debugged stopped while in a function called from GDB.
41609 (@value{GDBP}) @kbd{maint print dummy-frames}
41610 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
41614 Takes an optional file parameter.
41616 @kindex maint print frame-id
41617 @item maint print frame-id
41618 @itemx maint print frame-id @var{level}
41619 Print @value{GDBN}'s internal frame-id for the frame at relative
41620 @var{level}, or for the currently selected frame when @var{level} is
41623 If used, @var{level} should be an integer, as displayed in the
41624 @command{backtrace} output.
41627 (@value{GDBP}) maint print frame-id
41628 frame-id for frame #0: @{stack=0x7fffffffac70,code=0x0000000000401106,!special@}
41629 (@value{GDBP}) maint print frame-id 2
41630 frame-id for frame #2: @{stack=0x7fffffffac90,code=0x000000000040111c,!special@}
41633 @kindex maint print registers
41634 @kindex maint print raw-registers
41635 @kindex maint print cooked-registers
41636 @kindex maint print register-groups
41637 @kindex maint print remote-registers
41638 @item maint print registers @r{[}@var{file}@r{]}
41639 @itemx maint print raw-registers @r{[}@var{file}@r{]}
41640 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
41641 @itemx maint print register-groups @r{[}@var{file}@r{]}
41642 @itemx maint print remote-registers @r{[}@var{file}@r{]}
41643 Print @value{GDBN}'s internal register data structures.
41645 The command @code{maint print raw-registers} includes the contents of
41646 the raw register cache; the command @code{maint print
41647 cooked-registers} includes the (cooked) value of all registers,
41648 including registers which aren't available on the target nor visible
41649 to user; the command @code{maint print register-groups} includes the
41650 groups that each register is a member of; and the command @code{maint
41651 print remote-registers} includes the remote target's register numbers
41652 and offsets in the `G' packets.
41654 These commands take an optional parameter, a file name to which to
41655 write the information.
41657 @kindex maint print reggroups
41658 @item maint print reggroups @r{[}@var{file}@r{]}
41659 Print @value{GDBN}'s internal register group data structures. The
41660 optional argument @var{file} tells to what file to write the
41663 The register groups info looks like this:
41666 (@value{GDBP}) @kbd{maint print reggroups}
41677 @kindex maint flush register-cache
41679 @cindex register cache, flushing
41680 @item maint flush register-cache
41682 Flush the contents of the register cache and as a consequence the
41683 frame cache. This command is useful when debugging issues related to
41684 register fetching, or frame unwinding. The command @code{flushregs}
41685 is deprecated in favor of @code{maint flush register-cache}.
41687 @kindex maint flush source-cache
41688 @cindex source code, caching
41689 @item maint flush source-cache
41690 Flush @value{GDBN}'s cache of source code file contents. After
41691 @value{GDBN} reads a source file, and optionally applies styling
41692 (@pxref{Output Styling}), the file contents are cached. This command
41693 clears that cache. The next time @value{GDBN} wants to show lines
41694 from a source file, the content will be re-read.
41696 This command is useful when debugging issues related to source code
41697 styling. After flushing the cache any source code displayed by
41698 @value{GDBN} will be re-read and re-styled.
41700 @kindex maint print objfiles
41701 @cindex info for known object files
41702 @item maint print objfiles @r{[}@var{regexp}@r{]}
41703 Print a dump of all known object files.
41704 If @var{regexp} is specified, only print object files whose names
41705 match @var{regexp}. For each object file, this command prints its name,
41706 address in memory, and all of its psymtabs and symtabs.
41708 @kindex maint print user-registers
41709 @cindex user registers
41710 @item maint print user-registers
41711 List all currently available @dfn{user registers}. User registers
41712 typically provide alternate names for actual hardware registers. They
41713 include the four ``standard'' registers @code{$fp}, @code{$pc},
41714 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
41715 registers can be used in expressions in the same way as the canonical
41716 register names, but only the latter are listed by the @code{info
41717 registers} and @code{maint print registers} commands.
41719 @kindex maint print section-scripts
41720 @cindex info for known .debug_gdb_scripts-loaded scripts
41721 @item maint print section-scripts [@var{regexp}]
41722 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
41723 If @var{regexp} is specified, only print scripts loaded by object files
41724 matching @var{regexp}.
41725 For each script, this command prints its name as specified in the objfile,
41726 and the full path if known.
41727 @xref{dotdebug_gdb_scripts section}.
41729 @kindex maint print statistics
41730 @cindex bcache statistics
41731 @item maint print statistics
41732 This command prints, for each object file in the program, various data
41733 about that object file followed by the byte cache (@dfn{bcache})
41734 statistics for the object file. The objfile data includes the number
41735 of minimal, partial, full, and stabs symbols, the number of types
41736 defined by the objfile, the number of as yet unexpanded psym tables,
41737 the number of line tables and string tables, and the amount of memory
41738 used by the various tables. The bcache statistics include the counts,
41739 sizes, and counts of duplicates of all and unique objects, max,
41740 average, and median entry size, total memory used and its overhead and
41741 savings, and various measures of the hash table size and chain
41744 @kindex maint print target-stack
41745 @cindex target stack description
41746 @item maint print target-stack
41747 A @dfn{target} is an interface between the debugger and a particular
41748 kind of file or process. Targets can be stacked in @dfn{strata},
41749 so that more than one target can potentially respond to a request.
41750 In particular, memory accesses will walk down the stack of targets
41751 until they find a target that is interested in handling that particular
41754 This command prints a short description of each layer that was pushed on
41755 the @dfn{target stack}, starting from the top layer down to the bottom one.
41757 @kindex maint print type
41758 @cindex type chain of a data type
41759 @item maint print type @var{expr}
41760 Print the type chain for a type specified by @var{expr}. The argument
41761 can be either a type name or a symbol. If it is a symbol, the type of
41762 that symbol is described. The type chain produced by this command is
41763 a recursive definition of the data type as stored in @value{GDBN}'s
41764 data structures, including its flags and contained types.
41766 @kindex maint print record-instruction
41767 @item maint print record-instruction
41768 @itemx maint print record-instruction @var{N}
41769 print how GDB recorded a given instruction. If @var{n} is not positive
41770 number, it prints the values stored by the inferior before the @var{n}-th previous
41771 instruction was exectued. If @var{n} is positive, print the values after the @var{n}-th
41772 following instruction is executed. If @var{n} is not given, 0 is assumed.
41774 @kindex maint selftest
41776 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
41777 Run any self tests that were compiled in to @value{GDBN}. This will
41778 print a message showing how many tests were run, and how many failed.
41779 If a @var{filter} is passed, only the tests with @var{filter} in their
41780 name will be ran. If @code{-verbose} is passed, the self tests can be
41783 @kindex maint set selftest verbose
41784 @kindex maint show selftest verbose
41786 @item maint set selftest verbose
41787 @item maint show selftest verbose
41788 Control whether self tests are run verbosely or not.
41790 @kindex maint info selftests
41792 @item maint info selftests
41793 List the selftests compiled in to @value{GDBN}.
41795 @kindex maint set dwarf always-disassemble
41796 @kindex maint show dwarf always-disassemble
41797 @item maint set dwarf always-disassemble
41798 @item maint show dwarf always-disassemble
41799 Control the behavior of @code{info address} when using DWARF debugging
41802 The default is @code{off}, which means that @value{GDBN} should try to
41803 describe a variable's location in an easily readable format. When
41804 @code{on}, @value{GDBN} will instead display the DWARF location
41805 expression in an assembly-like format. Note that some locations are
41806 too complex for @value{GDBN} to describe simply; in this case you will
41807 always see the disassembly form.
41809 Here is an example of the resulting disassembly:
41812 (@value{GDBP}) info addr argc
41813 Symbol "argc" is a complex DWARF expression:
41817 For more information on these expressions, see
41818 @uref{http://www.dwarfstd.org/, the DWARF standard}.
41820 @kindex maint set dwarf max-cache-age
41821 @kindex maint show dwarf max-cache-age
41822 @item maint set dwarf max-cache-age
41823 @itemx maint show dwarf max-cache-age
41824 Control the DWARF compilation unit cache.
41826 @cindex DWARF compilation units cache
41827 In object files with inter-compilation-unit references, such as those
41828 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
41829 reader needs to frequently refer to previously read compilation units.
41830 This setting controls how long a compilation unit will remain in the
41831 cache if it is not referenced. A higher limit means that cached
41832 compilation units will be stored in memory longer, and more total
41833 memory will be used. Setting it to zero disables caching, which will
41834 slow down @value{GDBN} startup, but reduce memory consumption.
41836 @kindex maint set dwarf synchronous
41837 @kindex maint show dwarf synchronous
41838 @item maint set dwarf synchronous
41839 @itemx maint show dwarf synchronous
41840 Control whether DWARF is read asynchronously.
41842 On hosts where threading is available, the DWARF reader is mostly
41843 asynchronous with respect to the rest of @value{GDBN}. That is, the
41844 bulk of the reading is done in the background, and @value{GDBN} will
41845 only pause for completion of this task when absolutely necessary.
41847 When this setting is enabled, @value{GDBN} will instead wait for DWARF
41848 processing to complete before continuing.
41850 On hosts without threading, or where worker threads have been disabled
41851 at runtime, this setting has no effect, as DWARF reading is always
41852 done on the main thread, and is therefore always synchronous.
41854 @kindex maint set dwarf unwinders
41855 @kindex maint show dwarf unwinders
41856 @item maint set dwarf unwinders
41857 @itemx maint show dwarf unwinders
41858 Control use of the DWARF frame unwinders.
41860 @cindex DWARF frame unwinders
41861 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
41862 frame unwinders to build the backtrace. Many of these targets will
41863 also have a second mechanism for building the backtrace for use in
41864 cases where DWARF information is not available, this second mechanism
41865 is often an analysis of a function's prologue.
41867 In order to extend testing coverage of the second level stack
41868 unwinding mechanisms it is helpful to be able to disable the DWARF
41869 stack unwinders, this can be done with this switch.
41871 In normal use of @value{GDBN} disabling the DWARF unwinders is not
41872 advisable, there are cases that are better handled through DWARF than
41873 prologue analysis, and the debug experience is likely to be better
41874 with the DWARF frame unwinders enabled.
41876 If DWARF frame unwinders are not supported for a particular target
41877 architecture, then enabling this flag does not cause them to be used.
41879 @kindex maint info frame-unwinders
41880 @item maint info frame-unwinders
41881 List the frame unwinders currently in effect, starting with the highest priority.
41883 @kindex maint set worker-threads
41884 @kindex maint show worker-threads
41885 @item maint set worker-threads
41886 @item maint show worker-threads
41887 Control the number of worker threads that may be used by @value{GDBN}.
41888 On capable hosts, @value{GDBN} may use multiple threads to speed up
41889 certain CPU-intensive operations, such as demangling symbol names.
41890 While the number of threads used by @value{GDBN} may vary, this
41891 command can be used to set an upper bound on this number. The default
41892 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
41893 number. Note that this only controls worker threads started by
41894 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
41897 @kindex maint set profile
41898 @kindex maint show profile
41899 @cindex profiling GDB
41900 @item maint set profile
41901 @itemx maint show profile
41902 Control profiling of @value{GDBN}.
41904 Profiling will be disabled until you use the @samp{maint set profile}
41905 command to enable it. When you enable profiling, the system will begin
41906 collecting timing and execution count data; when you disable profiling or
41907 exit @value{GDBN}, the results will be written to a log file. Remember that
41908 if you use profiling, @value{GDBN} will overwrite the profiling log file
41909 (often called @file{gmon.out}). If you have a record of important profiling
41910 data in a @file{gmon.out} file, be sure to move it to a safe location.
41912 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
41913 compiled with the @samp{-pg} compiler option.
41915 @kindex maint set show-debug-regs
41916 @kindex maint show show-debug-regs
41917 @cindex hardware debug registers
41918 @item maint set show-debug-regs
41919 @itemx maint show show-debug-regs
41920 Control whether to show variables that mirror the hardware debug
41921 registers. Use @code{on} to enable, @code{off} to disable. If
41922 enabled, the debug registers values are shown when @value{GDBN} inserts or
41923 removes a hardware breakpoint or watchpoint, and when the inferior
41924 triggers a hardware-assisted breakpoint or watchpoint.
41926 @kindex maint set show-all-tib
41927 @kindex maint show show-all-tib
41928 @item maint set show-all-tib
41929 @itemx maint show show-all-tib
41930 Control whether to show all non zero areas within a 1k block starting
41931 at thread local base, when using the @samp{info w32 thread-information-block}
41934 @kindex maint set target-async
41935 @kindex maint show target-async
41936 @item maint set target-async
41937 @itemx maint show target-async
41938 This controls whether @value{GDBN} targets operate in synchronous or
41939 asynchronous mode (@pxref{Background Execution}). Normally the
41940 default is asynchronous, if it is available; but this can be changed
41941 to more easily debug problems occurring only in synchronous mode.
41943 @kindex maint set target-non-stop @var{mode} [on|off|auto]
41944 @kindex maint show target-non-stop
41945 @item maint set target-non-stop
41946 @itemx maint show target-non-stop
41948 This controls whether @value{GDBN} targets always operate in non-stop
41949 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
41950 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
41951 if supported by the target.
41954 @item maint set target-non-stop auto
41955 This is the default mode. @value{GDBN} controls the target in
41956 non-stop mode if the target supports it.
41958 @item maint set target-non-stop on
41959 @value{GDBN} controls the target in non-stop mode even if the target
41960 does not indicate support.
41962 @item maint set target-non-stop off
41963 @value{GDBN} does not control the target in non-stop mode even if the
41964 target supports it.
41967 @kindex maint set tui-resize-message
41968 @kindex maint show tui-resize-message
41969 @item maint set tui-resize-message
41970 @item maint show tui-resize-message
41971 Control whether @value{GDBN} displays a message each time the terminal
41972 is resized when in TUI mode. The default is @code{off}, which means
41973 that @value{GDBN} is silent during resizes. When @code{on},
41974 @value{GDBN} will display a message after a resize is completed; the
41975 message will include a number indicating how many times the terminal
41976 has been resized. This setting is intended for use by the test suite,
41977 where it would otherwise be difficult to determine when a resize and
41978 refresh has been completed.
41980 @kindex maint set tui-left-margin-verbose
41981 @kindex maint show tui-left-margin-verbose
41982 @item maint set tui-left-margin-verbose
41983 @item maint show tui-left-margin-verbose
41984 Control whether the left margin of the TUI source and disassembly windows
41985 uses @samp{_} and @samp{0} at locations where otherwise there would be a
41986 space. The default is @code{off}, which means spaces are used. The
41987 setting is intended to make it clear where the left margin begins and
41988 ends, to avoid incorrectly interpreting a space as being part of the
41991 @kindex maint set per-command
41992 @kindex maint show per-command
41993 @item maint set per-command
41994 @itemx maint show per-command
41995 @cindex resources used by commands
41997 @value{GDBN} can display the resources used by each command.
41998 This is useful in debugging performance problems.
42001 @item maint set per-command space [on|off]
42002 @itemx maint show per-command space
42003 Enable or disable the printing of the memory used by GDB for each command.
42004 If enabled, @value{GDBN} will display how much memory each command
42005 took, following the command's own output.
42006 This can also be requested by invoking @value{GDBN} with the
42007 @option{--statistics} command-line switch (@pxref{Mode Options}).
42009 @item maint set per-command time [on|off]
42010 @itemx maint show per-command time
42011 Enable or disable the printing of the execution time of @value{GDBN}
42013 If enabled, @value{GDBN} will display how much time it
42014 took to execute each command, following the command's own output.
42015 Both CPU time and wallclock time are printed.
42016 Printing both is useful when trying to determine whether the cost is
42017 CPU or, e.g., disk/network latency.
42018 Note that the CPU time printed is for @value{GDBN} only, it does not include
42019 the execution time of the inferior because there's no mechanism currently
42020 to compute how much time was spent by @value{GDBN} and how much time was
42021 spent by the program been debugged.
42022 This can also be requested by invoking @value{GDBN} with the
42023 @option{--statistics} command-line switch (@pxref{Mode Options}).
42025 @item maint set per-command symtab [on|off]
42026 @itemx maint show per-command symtab
42027 Enable or disable the printing of basic symbol table statistics
42029 If enabled, @value{GDBN} will display the following information:
42033 number of symbol tables
42035 number of primary symbol tables
42037 number of blocks in the blockvector
42041 @kindex maint set check-libthread-db
42042 @kindex maint show check-libthread-db
42043 @item maint set check-libthread-db [on|off]
42044 @itemx maint show check-libthread-db
42045 Control whether @value{GDBN} should run integrity checks on inferior
42046 specific thread debugging libraries as they are loaded. The default
42047 is not to perform such checks. If any check fails @value{GDBN} will
42048 unload the library and continue searching for a suitable candidate as
42049 described in @ref{set libthread-db-search-path}. For more information
42050 about the tests, see @ref{maint check libthread-db}.
42052 @kindex maint set gnu-source-highlight enabled
42053 @kindex maint show gnu-source-highlight enabled
42054 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
42055 @itemx maint show gnu-source-highlight enabled
42056 Control whether @value{GDBN} should use the GNU Source Highlight
42057 library for applying styling to source code (@pxref{Output Styling}).
42058 This will be @samp{on} by default if the GNU Source Highlight library
42059 is available. If the GNU Source Highlight library is not available,
42060 then this will be @samp{off} by default, and attempting to change this
42061 value to @samp{on} will give an error.
42063 If the GNU Source Highlight library is not being used, then
42064 @value{GDBN} will use the Python Pygments package for source code
42065 styling, if it is available.
42067 This option is useful for debugging @value{GDBN}'s use of the Pygments
42068 library when @value{GDBN} is linked against the GNU Source Highlight
42071 @anchor{maint_libopcodes_styling}
42072 @kindex maint set libopcodes-styling enabled
42073 @kindex maint show libopcodes-styling enabled
42074 @item maint set libopcodes-styling enabled @r{[}on|off@r{]}
42075 @itemx maint show libopcodes-styling enabled
42076 Control whether @value{GDBN} should use its builtin disassembler
42077 (@file{libopcodes}) to style disassembler output (@pxref{Output
42078 Styling}). The builtin disassembler does not support styling for all
42081 When this option is @samp{off} the builtin disassembler will not be
42082 used for styling, @value{GDBN} will fall back to using the Python
42083 Pygments package if possible.
42085 Trying to set this option @samp{on} for an architecture that the
42086 builtin disassembler is unable to style will give an error, otherwise,
42087 the builtin disassembler will be used to style disassembler output.
42089 This option is @samp{on} by default for supported architectures.
42091 This option is useful for debugging @value{GDBN}'s use of the Pygments
42092 library when @value{GDBN} is built for an architecture that supports
42093 styling with the builtin disassembler
42095 @kindex maint info screen
42096 @cindex show screen characteristics
42097 @item maint info screen
42098 Print various characteristics of the screen, such as various notions
42099 of width and height.
42101 @kindex maint space
42102 @cindex memory used by commands
42103 @item maint space @var{value}
42104 An alias for @code{maint set per-command space}.
42105 A non-zero value enables it, zero disables it.
42108 @cindex time of command execution
42109 @item maint time @var{value}
42110 An alias for @code{maint set per-command time}.
42111 A non-zero value enables it, zero disables it.
42113 @kindex maint translate-address
42114 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
42115 Find the symbol stored at the location specified by the address
42116 @var{addr} and an optional section name @var{section}. If found,
42117 @value{GDBN} prints the name of the closest symbol and an offset from
42118 the symbol's location to the specified address. This is similar to
42119 the @code{info address} command (@pxref{Symbols}), except that this
42120 command also allows to find symbols in other sections.
42122 If section was not specified, the section in which the symbol was found
42123 is also printed. For dynamically linked executables, the name of
42124 executable or shared library containing the symbol is printed as well.
42126 @kindex maint test-options
42127 @item maint test-options require-delimiter
42128 @itemx maint test-options unknown-is-error
42129 @itemx maint test-options unknown-is-operand
42130 These commands are used by the testsuite to validate the command
42131 options framework. The @code{require-delimiter} variant requires a
42132 double-dash delimiter to indicate end of options. The
42133 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
42134 @code{unknown-is-error} variant throws an error on unknown option,
42135 while @code{unknown-is-operand} treats unknown options as the start of
42136 the command's operands. When run, the commands output the result of
42137 the processed options. When completed, the commands store the
42138 internal result of completion in a variable exposed by the @code{maint
42139 show test-options-completion-result} command.
42141 @kindex maint show test-options-completion-result
42142 @item maint show test-options-completion-result
42143 Shows the result of completing the @code{maint test-options}
42144 subcommands. This is used by the testsuite to validate completion
42145 support in the command options framework.
42147 @kindex maint set test-settings
42148 @kindex maint show test-settings
42149 @item maint set test-settings @var{kind}
42150 @itemx maint show test-settings @var{kind}
42151 These are representative commands for each @var{kind} of setting type
42152 @value{GDBN} supports. They are used by the testsuite for exercising
42153 the settings infrastructure.
42155 @kindex maint set backtrace-on-fatal-signal
42156 @kindex maint show backtrace-on-fatal-signal
42157 @item maint set backtrace-on-fatal-signal [on|off]
42158 @itemx maint show backtrace-on-fatal-signal
42159 When this setting is @code{on}, if @value{GDBN} itself terminates with
42160 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
42161 printed to the standard error stream. This backtrace can be used to
42162 help diagnose crashes within @value{GDBN} in situations where a user
42163 is unable to share a corefile with the @value{GDBN} developers.
42165 If the functionality to provide this backtrace is not available for
42166 the platform on which GDB is running then this feature will be
42167 @code{off} by default, and attempting to turn this feature on will
42170 For platforms that do support creating the backtrace this feature is
42171 @code{on} by default.
42173 @kindex maint wait-for-index-cache
42174 @item maint wait-for-index-cache
42175 Wait until all pending writes to the index cache have completed. This
42176 is used by the test suite to avoid races when the index cache is being
42177 updated by a worker thread.
42180 @item maint with @var{setting} [@var{value}] [-- @var{command}]
42181 Like the @code{with} command, but works with @code{maintenance set}
42182 variables. This is used by the testsuite to exercise the @code{with}
42183 command's infrastructure.
42185 @kindex maint ignore-probes
42186 @item maint ignore-probes [@var{-v}|@var{-verbose}] [@var{provider} [@var{name} [@var{objfile}]]]
42187 @itemx maint ignore-probes @var{-reset}
42188 Set or reset the ignore-probes filter. The @var{provider}, @var{name}
42189 and @var{objfile} arguments are as in @code{enable probes} and
42190 @code{disable probes} (@pxref{enable probes}). Only supported for
42193 Here's an example of using @code{maint ignore-probes}:
42195 (gdb) maint ignore-probes -verbose libc ^longjmp$
42196 ignore-probes filter has been set to:
42198 PROBE_NAME: '^longjmp$'
42201 <... more output ...>
42202 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
42203 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
42204 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
42208 The following command is useful for non-interactive invocations of
42209 @value{GDBN}, such as in the test suite.
42212 @item set watchdog @var{nsec}
42213 @kindex set watchdog
42214 @cindex watchdog timer
42215 @cindex timeout for commands
42216 Set the maximum number of seconds @value{GDBN} will wait for the
42217 target operation to finish. If this time expires, @value{GDBN}
42218 reports and error and the command is aborted.
42220 @item show watchdog
42221 Show the current setting of the target wait timeout.
42224 @node Remote Protocol
42225 @appendix @value{GDBN} Remote Serial Protocol
42230 * Stop Reply Packets::
42231 * General Query Packets::
42232 * Architecture-Specific Protocol Details::
42233 * Tracepoint Packets::
42234 * Host I/O Packets::
42236 * Notification Packets::
42237 * Remote Non-Stop::
42238 * Packet Acknowledgment::
42240 * File-I/O Remote Protocol Extension::
42241 * Library List Format::
42242 * Library List Format for SVR4 Targets::
42243 * Memory Map Format::
42244 * Thread List Format::
42245 * Traceframe Info Format::
42246 * Branch Trace Format::
42247 * Branch Trace Configuration Format::
42253 There may be occasions when you need to know something about the
42254 protocol---for example, if there is only one serial port to your target
42255 machine, you might want your program to do something special if it
42256 recognizes a packet meant for @value{GDBN}.
42258 In the examples below, @samp{->} and @samp{<-} are used to indicate
42259 transmitted and received data, respectively.
42261 @cindex protocol, @value{GDBN} remote serial
42262 @cindex serial protocol, @value{GDBN} remote
42263 @cindex remote serial protocol
42264 All @value{GDBN} commands and responses (other than acknowledgments
42265 and notifications, see @ref{Notification Packets}) are sent as a
42266 @var{packet}. A @var{packet} is introduced with the character
42267 @samp{$}, the actual @var{packet-data}, and the terminating character
42268 @samp{#} followed by a two-digit @var{checksum}:
42271 @code{$}@var{packet-data}@code{#}@var{checksum}
42275 @cindex checksum, for @value{GDBN} remote
42277 The two-digit @var{checksum} is computed as the modulo 256 sum of all
42278 characters between the leading @samp{$} and the trailing @samp{#} (an
42279 eight bit unsigned checksum).
42281 Implementors should note that prior to @value{GDBN} 5.0 the protocol
42282 specification also included an optional two-digit @var{sequence-id}:
42285 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
42288 @cindex sequence-id, for @value{GDBN} remote
42290 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
42291 has never output @var{sequence-id}s. Stubs that handle packets added
42292 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
42294 When either the host or the target machine receives a packet, the first
42295 response expected is an acknowledgment: either @samp{+} (to indicate
42296 the package was received correctly) or @samp{-} (to request
42300 -> @code{$}@var{packet-data}@code{#}@var{checksum}
42305 The @samp{+}/@samp{-} acknowledgments can be disabled
42306 once a connection is established.
42307 @xref{Packet Acknowledgment}, for details.
42309 The host (@value{GDBN}) sends @var{command}s, and the target (the
42310 debugging stub incorporated in your program) sends a @var{response}. In
42311 the case of step and continue @var{command}s, the response is only sent
42312 when the operation has completed, and the target has again stopped all
42313 threads in all attached processes. This is the default all-stop mode
42314 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
42315 execution mode; see @ref{Remote Non-Stop}, for details.
42317 @var{packet-data} consists of a sequence of characters with the
42318 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
42321 @cindex remote protocol, field separator
42322 Fields within the packet should be separated using @samp{,} @samp{;} or
42323 @samp{:}. Except where otherwise noted all numbers are represented in
42324 @sc{hex} with leading zeros suppressed.
42326 Implementors should note that prior to @value{GDBN} 5.0, the character
42327 @samp{:} could not appear as the third character in a packet (as it
42328 would potentially conflict with the @var{sequence-id}).
42330 @cindex remote protocol, binary data
42331 @anchor{Binary Data}
42332 Binary data in most packets is encoded either as two hexadecimal
42333 digits per byte of binary data. This allowed the traditional remote
42334 protocol to work over connections which were only seven-bit clean.
42335 Some packets designed more recently assume an eight-bit clean
42336 connection, and use a more efficient encoding to send and receive
42339 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
42340 as an escape character. Any escaped byte is transmitted as the escape
42341 character followed by the original character XORed with @code{0x20}.
42342 For example, the byte @code{0x7d} would be transmitted as the two
42343 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
42344 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
42345 @samp{@}}) must always be escaped. Responses sent by the stub
42346 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
42347 is not interpreted as the start of a run-length encoded sequence
42350 Response @var{data} can be run-length encoded to save space.
42351 Run-length encoding replaces runs of identical characters with one
42352 instance of the repeated character, followed by a @samp{*} and a
42353 repeat count. The repeat count is itself sent encoded, to avoid
42354 binary characters in @var{data}: a value of @var{n} is sent as
42355 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
42356 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
42357 code 32) for a repeat count of 3. (This is because run-length
42358 encoding starts to win for counts 3 or more.) Thus, for example,
42359 @samp{0* } is a run-length encoding of ``0000'': the space character
42360 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
42363 The printable characters @samp{#} and @samp{$} or with a numeric value
42364 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
42365 seven repeats (@samp{$}) can be expanded using a repeat count of only
42366 five (@samp{"}). For example, @samp{00000000} can be encoded as
42369 The error response returned for some packets includes a two character
42370 error number. That number is not well defined.
42372 @cindex empty response, for unsupported packets
42373 For any @var{command} not supported by the stub, an empty response
42374 (@samp{$#00}) should be returned. That way it is possible to extend the
42375 protocol. A newer @value{GDBN} can tell if a packet is supported based
42378 At a minimum, a stub is required to support the @samp{?} command to
42379 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
42380 commands for register access, and the @samp{m} and @samp{M} commands
42381 for memory access. Stubs that only control single-threaded targets
42382 can implement run control with the @samp{c} (continue) command, and if
42383 the target architecture supports hardware-assisted single-stepping,
42384 the @samp{s} (step) command. Stubs that support multi-threading
42385 targets should support the @samp{vCont} command. All other commands
42391 The following table provides a complete list of all currently defined
42392 @var{command}s and their corresponding response @var{data}.
42393 @xref{File-I/O Remote Protocol Extension}, for details about the File
42394 I/O extension of the remote protocol.
42396 Each packet's description has a template showing the packet's overall
42397 syntax, followed by an explanation of the packet's meaning. We
42398 include spaces in some of the templates for clarity; these are not
42399 part of the packet's syntax. No @value{GDBN} packet uses spaces to
42400 separate its components. For example, a template like @samp{foo
42401 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
42402 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
42403 @var{baz}. @value{GDBN} does not transmit a space character between the
42404 @samp{foo} and the @var{bar}, or between the @var{bar} and the
42407 @cindex @var{thread-id}, in remote protocol
42408 @anchor{thread-id syntax}
42409 Several packets and replies include a @var{thread-id} field to identify
42410 a thread. Normally these are positive numbers with a target-specific
42411 interpretation, formatted as big-endian hex strings. A @var{thread-id}
42412 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
42415 In addition, the remote protocol supports a multiprocess feature in
42416 which the @var{thread-id} syntax is extended to optionally include both
42417 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
42418 The @var{pid} (process) and @var{tid} (thread) components each have the
42419 format described above: a positive number with target-specific
42420 interpretation formatted as a big-endian hex string, literal @samp{-1}
42421 to indicate all processes or threads (respectively), or @samp{0} to
42422 indicate an arbitrary process or thread. Specifying just a process, as
42423 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
42424 error to specify all processes but a specific thread, such as
42425 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
42426 for those packets and replies explicitly documented to include a process
42427 ID, rather than a @var{thread-id}.
42429 The multiprocess @var{thread-id} syntax extensions are only used if both
42430 @value{GDBN} and the stub report support for the @samp{multiprocess}
42431 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
42434 Note that all packet forms beginning with an upper- or lower-case
42435 letter, other than those described here, are reserved for future use.
42437 Here are the packet descriptions.
42442 @cindex @samp{!} packet
42443 @anchor{extended mode}
42444 Enable extended mode. In extended mode, the remote server is made
42445 persistent. The @samp{R} packet is used to restart the program being
42451 The remote target both supports and has enabled extended mode.
42455 @cindex @samp{?} packet
42457 This is sent when connection is first established to query the reason
42458 the target halted. The reply is the same as for step and continue.
42459 This packet has a special interpretation when the target is in
42460 non-stop mode; see @ref{Remote Non-Stop}.
42463 @xref{Stop Reply Packets}, for the reply specifications.
42465 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
42466 @cindex @samp{A} packet
42467 Initialized @code{argv[]} array passed into program. @var{arglen}
42468 specifies the number of bytes in the hex encoded byte stream
42469 @var{arg}. See @code{gdbserver} for more details.
42474 The arguments were set.
42480 @cindex @samp{b} packet
42481 (Don't use this packet; its behavior is not well-defined.)
42482 Change the serial line speed to @var{baud}.
42484 JTC: @emph{When does the transport layer state change? When it's
42485 received, or after the ACK is transmitted. In either case, there are
42486 problems if the command or the acknowledgment packet is dropped.}
42488 Stan: @emph{If people really wanted to add something like this, and get
42489 it working for the first time, they ought to modify ser-unix.c to send
42490 some kind of out-of-band message to a specially-setup stub and have the
42491 switch happen "in between" packets, so that from remote protocol's point
42492 of view, nothing actually happened.}
42494 @item B @var{addr},@var{mode}
42495 @cindex @samp{B} packet
42496 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
42497 breakpoint at @var{addr}.
42499 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
42500 (@pxref{insert breakpoint or watchpoint packet}).
42502 @cindex @samp{bc} packet
42505 Backward continue. Execute the target system in reverse. No parameter.
42506 @xref{Reverse Execution}, for more information.
42509 @xref{Stop Reply Packets}, for the reply specifications.
42511 @cindex @samp{bs} packet
42514 Backward single step. Execute one instruction in reverse. No parameter.
42515 @xref{Reverse Execution}, for more information.
42518 @xref{Stop Reply Packets}, for the reply specifications.
42520 @item c @r{[}@var{addr}@r{]}
42521 @cindex @samp{c} packet
42522 Continue at @var{addr}, which is the address to resume. If @var{addr}
42523 is omitted, resume at current address.
42525 This packet is deprecated for multi-threading support. @xref{vCont
42529 @xref{Stop Reply Packets}, for the reply specifications.
42531 @item C @var{sig}@r{[};@var{addr}@r{]}
42532 @cindex @samp{C} packet
42533 Continue with signal @var{sig} (hex signal number). If
42534 @samp{;@var{addr}} is omitted, resume at same address.
42536 This packet is deprecated for multi-threading support. @xref{vCont
42540 @xref{Stop Reply Packets}, for the reply specifications.
42543 @cindex @samp{d} packet
42546 Don't use this packet; instead, define a general set packet
42547 (@pxref{General Query Packets}).
42551 @cindex @samp{D} packet
42552 The first form of the packet is used to detach @value{GDBN} from the
42553 remote system. It is sent to the remote target
42554 before @value{GDBN} disconnects via the @code{detach} command.
42556 The second form, including a process ID, is used when multiprocess
42557 protocol extensions are enabled (@pxref{multiprocess extensions}), to
42558 detach only a specific process. The @var{pid} is specified as a
42559 big-endian hex string.
42569 @item F @var{RC},@var{EE},@var{CF};@var{XX}
42570 @cindex @samp{F} packet
42571 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
42572 This is part of the File-I/O protocol extension. @xref{File-I/O
42573 Remote Protocol Extension}, for the specification.
42576 @anchor{read registers packet}
42577 @cindex @samp{g} packet
42578 Read general registers.
42582 @item @var{XX@dots{}}
42583 Each byte of register data is described by two hex digits. The bytes
42584 with the register are transmitted in target byte order. The size of
42585 each register and their position within the @samp{g} packet are
42586 determined by the target description (@pxref{Target Descriptions}); in
42587 the absence of a target description, this is done using code internal
42588 to @value{GDBN}; typically this is some customary register layout for
42589 the architecture in question.
42591 When reading registers, the stub may also return a string of literal
42592 @samp{x}'s in place of the register data digits, to indicate that the
42593 corresponding register's value is unavailable. For example, when
42594 reading registers from a trace frame (@pxref{Analyze Collected
42595 Data,,Using the Collected Data}), this means that the register has not
42596 been collected in the trace frame. When reading registers from a live
42597 program, this indicates that the stub has no means to access the
42598 register contents, even though the corresponding register is known to
42599 exist. Note that if a register truly does not exist on the target,
42600 then it is better to not include it in the target description in the
42603 For example, for an architecture with 4 registers of
42604 4 bytes each, the following reply indicates to @value{GDBN} that
42605 registers 0 and 2 are unavailable, while registers 1 and 3
42606 are available, and both have zero value:
42610 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
42617 @item G @var{XX@dots{}}
42618 @cindex @samp{G} packet
42619 Write general registers. @xref{read registers packet}, for a
42620 description of the @var{XX@dots{}} data.
42630 @item H @var{op} @var{thread-id}
42631 @cindex @samp{H} packet
42632 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
42633 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
42634 should be @samp{c} for step and continue operations (note that this
42635 is deprecated, supporting the @samp{vCont} command is a better
42636 option), and @samp{g} for other operations. The thread designator
42637 @var{thread-id} has the format and interpretation described in
42638 @ref{thread-id syntax}.
42649 @c 'H': How restrictive (or permissive) is the thread model. If a
42650 @c thread is selected and stopped, are other threads allowed
42651 @c to continue to execute? As I mentioned above, I think the
42652 @c semantics of each command when a thread is selected must be
42653 @c described. For example:
42655 @c 'g': If the stub supports threads and a specific thread is
42656 @c selected, returns the register block from that thread;
42657 @c otherwise returns current registers.
42659 @c 'G' If the stub supports threads and a specific thread is
42660 @c selected, sets the registers of the register block of
42661 @c that thread; otherwise sets current registers.
42663 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
42664 @anchor{cycle step packet}
42665 @cindex @samp{i} packet
42666 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
42667 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
42668 step starting at that address.
42671 @cindex @samp{I} packet
42672 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
42676 @cindex @samp{k} packet
42679 The exact effect of this packet is not specified.
42681 For a bare-metal target, it may power cycle or reset the target
42682 system. For that reason, the @samp{k} packet has no reply.
42684 For a single-process target, it may kill that process if possible.
42686 A multiple-process target may choose to kill just one process, or all
42687 that are under @value{GDBN}'s control. For more precise control, use
42688 the vKill packet (@pxref{vKill packet}).
42690 If the target system immediately closes the connection in response to
42691 @samp{k}, @value{GDBN} does not consider the lack of packet
42692 acknowledgment to be an error, and assumes the kill was successful.
42694 If connected using @kbd{target extended-remote}, and the target does
42695 not close the connection in response to a kill request, @value{GDBN}
42696 probes the target state as if a new connection was opened
42697 (@pxref{? packet}).
42699 @item m @var{addr},@var{length}
42700 @cindex @samp{m} packet
42701 Read @var{length} addressable memory units starting at address @var{addr}
42702 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
42703 any particular boundary.
42705 The stub need not use any particular size or alignment when gathering
42706 data from memory for the response; even if @var{addr} is word-aligned
42707 and @var{length} is a multiple of the word size, the stub is free to
42708 use byte accesses, or not. For this reason, this packet may not be
42709 suitable for accessing memory-mapped I/O devices.
42710 @cindex alignment of remote memory accesses
42711 @cindex size of remote memory accesses
42712 @cindex memory, alignment and size of remote accesses
42716 @item @var{XX@dots{}}
42717 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
42718 The reply may contain fewer addressable memory units than requested if the
42719 server was able to read only part of the region of memory.
42724 @item M @var{addr},@var{length}:@var{XX@dots{}}
42725 @cindex @samp{M} packet
42726 Write @var{length} addressable memory units starting at address @var{addr}
42727 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
42728 byte is transmitted as a two-digit hexadecimal number.
42735 for an error (this includes the case where only part of the data was
42740 @cindex @samp{p} packet
42741 Read the value of register @var{n}; @var{n} is in hex.
42742 @xref{read registers packet}, for a description of how the returned
42743 register value is encoded.
42747 @item @var{XX@dots{}}
42748 the register's value
42752 Indicating an unrecognized @var{query}.
42755 @item P @var{n@dots{}}=@var{r@dots{}}
42756 @anchor{write register packet}
42757 @cindex @samp{P} packet
42758 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
42759 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
42760 digits for each byte in the register (target byte order).
42770 @item q @var{name} @var{params}@dots{}
42771 @itemx Q @var{name} @var{params}@dots{}
42772 @cindex @samp{q} packet
42773 @cindex @samp{Q} packet
42774 General query (@samp{q}) and set (@samp{Q}). These packets are
42775 described fully in @ref{General Query Packets}.
42778 @cindex @samp{r} packet
42779 Reset the entire system.
42781 Don't use this packet; use the @samp{R} packet instead.
42784 @cindex @samp{R} packet
42785 Restart the program being debugged. The @var{XX}, while needed, is ignored.
42786 This packet is only available in extended mode (@pxref{extended mode}).
42788 The @samp{R} packet has no reply.
42790 @item s @r{[}@var{addr}@r{]}
42791 @cindex @samp{s} packet
42792 Single step, resuming at @var{addr}. If
42793 @var{addr} is omitted, resume at same address.
42795 This packet is deprecated for multi-threading support. @xref{vCont
42799 @xref{Stop Reply Packets}, for the reply specifications.
42801 @item S @var{sig}@r{[};@var{addr}@r{]}
42802 @anchor{step with signal packet}
42803 @cindex @samp{S} packet
42804 Step with signal. This is analogous to the @samp{C} packet, but
42805 requests a single-step, rather than a normal resumption of execution.
42807 This packet is deprecated for multi-threading support. @xref{vCont
42811 @xref{Stop Reply Packets}, for the reply specifications.
42813 @item t @var{addr}:@var{PP},@var{MM}
42814 @cindex @samp{t} packet
42815 Search backwards starting at address @var{addr} for a match with pattern
42816 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
42817 There must be at least 3 digits in @var{addr}.
42819 @item T @var{thread-id}
42820 @cindex @samp{T} packet
42821 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
42826 thread is still alive
42832 Packets starting with @samp{v} are identified by a multi-letter name,
42833 up to the first @samp{;} or @samp{?} (or the end of the packet).
42835 @item vAttach;@var{pid}
42836 @cindex @samp{vAttach} packet
42837 Attach to a new process with the specified process ID @var{pid}.
42838 The process ID is a
42839 hexadecimal integer identifying the process. In all-stop mode, all
42840 threads in the attached process are stopped; in non-stop mode, it may be
42841 attached without being stopped if that is supported by the target.
42843 @c In non-stop mode, on a successful vAttach, the stub should set the
42844 @c current thread to a thread of the newly-attached process. After
42845 @c attaching, GDB queries for the attached process's thread ID with qC.
42846 @c Also note that, from a user perspective, whether or not the
42847 @c target is stopped on attach in non-stop mode depends on whether you
42848 @c use the foreground or background version of the attach command, not
42849 @c on what vAttach does; GDB does the right thing with respect to either
42850 @c stopping or restarting threads.
42852 This packet is only available in extended mode (@pxref{extended mode}).
42858 @item @r{Any stop packet}
42859 for success in all-stop mode (@pxref{Stop Reply Packets})
42861 for success in non-stop mode (@pxref{Remote Non-Stop})
42864 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
42865 @cindex @samp{vCont} packet
42866 @anchor{vCont packet}
42867 Resume the inferior, specifying different actions for each thread.
42869 For each inferior thread, the leftmost action with a matching
42870 @var{thread-id} is applied. Threads that don't match any action
42871 remain in their current state. Thread IDs are specified using the
42872 syntax described in @ref{thread-id syntax}. If multiprocess
42873 extensions (@pxref{multiprocess extensions}) are supported, actions
42874 can be specified to match all threads in a process by using the
42875 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
42876 @var{thread-id} matches all threads. Specifying no actions is an
42879 Currently supported actions are:
42885 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
42889 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
42892 @item r @var{start},@var{end}
42893 Step once, and then keep stepping as long as the thread stops at
42894 addresses between @var{start} (inclusive) and @var{end} (exclusive).
42895 The remote stub reports a stop reply when either the thread goes out
42896 of the range or is stopped due to an unrelated reason, such as hitting
42897 a breakpoint. @xref{range stepping}.
42899 If the range is empty (@var{start} == @var{end}), then the action
42900 becomes equivalent to the @samp{s} action. In other words,
42901 single-step once, and report the stop (even if the stepped instruction
42902 jumps to @var{start}).
42904 (A stop reply may be sent at any point even if the PC is still within
42905 the stepping range; for example, it is valid to implement this packet
42906 in a degenerate way as a single instruction step operation.)
42910 The optional argument @var{addr} normally associated with the
42911 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
42912 not supported in @samp{vCont}.
42914 The @samp{t} action is only relevant in non-stop mode
42915 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
42916 A stop reply should be generated for any affected thread not already stopped.
42917 When a thread is stopped by means of a @samp{t} action,
42918 the corresponding stop reply should indicate that the thread has stopped with
42919 signal @samp{0}, regardless of whether the target uses some other signal
42920 as an implementation detail.
42922 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
42923 @samp{r} actions for threads that are already running. Conversely,
42924 the server must ignore @samp{t} actions for threads that are already
42927 @emph{Note:} In non-stop mode, a thread is considered running until
42928 @value{GDBN} acknowledges an asynchronous stop notification for it with
42929 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
42931 The stub must support @samp{vCont} if it reports support for
42932 multiprocess extensions (@pxref{multiprocess extensions}).
42935 @xref{Stop Reply Packets}, for the reply specifications.
42938 @cindex @samp{vCont?} packet
42939 Request a list of actions supported by the @samp{vCont} packet.
42943 @item vCont@r{[};@var{action}@dots{}@r{]}
42944 The @samp{vCont} packet is supported. Each @var{action} is a supported
42945 command in the @samp{vCont} packet.
42947 The @samp{vCont} packet is not supported.
42950 @anchor{vCtrlC packet}
42952 @cindex @samp{vCtrlC} packet
42953 Interrupt remote target as if a control-C was pressed on the remote
42954 terminal. This is the equivalent to reacting to the @code{^C}
42955 (@samp{\003}, the control-C character) character in all-stop mode
42956 while the target is running, except this works in non-stop mode.
42957 @xref{interrupting remote targets}, for more info on the all-stop
42968 @item vFile:@var{operation}:@var{parameter}@dots{}
42969 @cindex @samp{vFile} packet
42970 Perform a file operation on the target system. For details,
42971 see @ref{Host I/O Packets}.
42973 @item vFlashErase:@var{addr},@var{length}
42974 @cindex @samp{vFlashErase} packet
42975 Direct the stub to erase @var{length} bytes of flash starting at
42976 @var{addr}. The region may enclose any number of flash blocks, but
42977 its start and end must fall on block boundaries, as indicated by the
42978 flash block size appearing in the memory map (@pxref{Memory Map
42979 Format}). @value{GDBN} groups flash memory programming operations
42980 together, and sends a @samp{vFlashDone} request after each group; the
42981 stub is allowed to delay erase operation until the @samp{vFlashDone}
42982 packet is received.
42992 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
42993 @cindex @samp{vFlashWrite} packet
42994 Direct the stub to write data to flash address @var{addr}. The data
42995 is passed in binary form using the same encoding as for the @samp{X}
42996 packet (@pxref{Binary Data}). The memory ranges specified by
42997 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
42998 not overlap, and must appear in order of increasing addresses
42999 (although @samp{vFlashErase} packets for higher addresses may already
43000 have been received; the ordering is guaranteed only between
43001 @samp{vFlashWrite} packets). If a packet writes to an address that was
43002 neither erased by a preceding @samp{vFlashErase} packet nor by some other
43003 target-specific method, the results are unpredictable.
43011 for vFlashWrite addressing non-flash memory
43017 @cindex @samp{vFlashDone} packet
43018 Indicate to the stub that flash programming operation is finished.
43019 The stub is permitted to delay or batch the effects of a group of
43020 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
43021 @samp{vFlashDone} packet is received. The contents of the affected
43022 regions of flash memory are unpredictable until the @samp{vFlashDone}
43023 request is completed.
43025 @item vKill;@var{pid}
43026 @cindex @samp{vKill} packet
43027 @anchor{vKill packet}
43028 Kill the process with the specified process ID @var{pid}, which is a
43029 hexadecimal integer identifying the process. This packet is used in
43030 preference to @samp{k} when multiprocess protocol extensions are
43031 supported; see @ref{multiprocess extensions}.
43041 @item vMustReplyEmpty
43042 @cindex @samp{vMustReplyEmpty} packet
43043 The correct reply to an unknown @samp{v} packet is to return the empty
43044 string, however, some older versions of @command{gdbserver} would
43045 incorrectly return @samp{OK} for unknown @samp{v} packets.
43047 The @samp{vMustReplyEmpty} is used as a feature test to check how
43048 @command{gdbserver} handles unknown packets, it is important that this
43049 packet be handled in the same way as other unknown @samp{v} packets.
43050 If this packet is handled differently to other unknown @samp{v}
43051 packets then it is possible that @value{GDBN} may run into problems in
43052 other areas, specifically around use of @samp{vFile:setfs:}.
43054 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
43055 @cindex @samp{vRun} packet
43056 Run the program @var{filename}, passing it each @var{argument} on its
43057 command line. The file and arguments are hex-encoded strings. If
43058 @var{filename} is an empty string, the stub may use a default program
43059 (e.g.@: the last program run). The program is created in the stopped
43062 @c FIXME: What about non-stop mode?
43064 This packet is only available in extended mode (@pxref{extended mode}).
43070 @item @r{Any stop packet}
43071 for success (@pxref{Stop Reply Packets})
43075 @cindex @samp{vStopped} packet
43076 @xref{Notification Packets}.
43078 @item X @var{addr},@var{length}:@var{XX@dots{}}
43080 @cindex @samp{X} packet
43081 Write data to memory, where the data is transmitted in binary.
43082 Memory is specified by its address @var{addr} and number of addressable memory
43083 units @var{length} (@pxref{addressable memory unit});
43084 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
43094 @item z @var{type},@var{addr},@var{kind}
43095 @itemx Z @var{type},@var{addr},@var{kind}
43096 @anchor{insert breakpoint or watchpoint packet}
43097 @cindex @samp{z} packet
43098 @cindex @samp{Z} packets
43099 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
43100 watchpoint starting at address @var{address} of kind @var{kind}.
43102 Each breakpoint and watchpoint packet @var{type} is documented
43105 @emph{Implementation notes: A remote target shall return an empty string
43106 for an unrecognized breakpoint or watchpoint packet @var{type}. A
43107 remote target shall support either both or neither of a given
43108 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
43109 avoid potential problems with duplicate packets, the operations should
43110 be implemented in an idempotent way.}
43112 @item z0,@var{addr},@var{kind}
43113 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
43114 @cindex @samp{z0} packet
43115 @cindex @samp{Z0} packet
43116 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
43117 @var{addr} of type @var{kind}.
43119 A software breakpoint is implemented by replacing the instruction at
43120 @var{addr} with a software breakpoint or trap instruction. The
43121 @var{kind} is target-specific and typically indicates the size of the
43122 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
43123 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
43124 architectures have additional meanings for @var{kind}
43125 (@pxref{Architecture-Specific Protocol Details}); if no
43126 architecture-specific value is being used, it should be @samp{0}.
43127 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
43128 conditional expressions in bytecode form that should be evaluated on
43129 the target's side. These are the conditions that should be taken into
43130 consideration when deciding if the breakpoint trigger should be
43131 reported back to @value{GDBN}.
43133 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
43134 for how to best report a software breakpoint event to @value{GDBN}.
43136 The @var{cond_list} parameter is comprised of a series of expressions,
43137 concatenated without separators. Each expression has the following form:
43141 @item X @var{len},@var{expr}
43142 @var{len} is the length of the bytecode expression and @var{expr} is the
43143 actual conditional expression in bytecode form.
43147 The optional @var{cmd_list} parameter introduces commands that may be
43148 run on the target, rather than being reported back to @value{GDBN}.
43149 The parameter starts with a numeric flag @var{persist}; if the flag is
43150 nonzero, then the breakpoint may remain active and the commands
43151 continue to be run even when @value{GDBN} disconnects from the target.
43152 Following this flag is a series of expressions concatenated with no
43153 separators. Each expression has the following form:
43157 @item X @var{len},@var{expr}
43158 @var{len} is the length of the bytecode expression and @var{expr} is the
43159 actual commands expression in bytecode form.
43163 @emph{Implementation note: It is possible for a target to copy or move
43164 code that contains software breakpoints (e.g., when implementing
43165 overlays). The behavior of this packet, in the presence of such a
43166 target, is not defined.}
43178 @item z1,@var{addr},@var{kind}
43179 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
43180 @cindex @samp{z1} packet
43181 @cindex @samp{Z1} packet
43182 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
43183 address @var{addr}.
43185 A hardware breakpoint is implemented using a mechanism that is not
43186 dependent on being able to modify the target's memory. The
43187 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
43188 same meaning as in @samp{Z0} packets.
43190 @emph{Implementation note: A hardware breakpoint is not affected by code
43203 @item z2,@var{addr},@var{kind}
43204 @itemx Z2,@var{addr},@var{kind}
43205 @cindex @samp{z2} packet
43206 @cindex @samp{Z2} packet
43207 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
43208 The number of bytes to watch is specified by @var{kind}.
43220 @item z3,@var{addr},@var{kind}
43221 @itemx Z3,@var{addr},@var{kind}
43222 @cindex @samp{z3} packet
43223 @cindex @samp{Z3} packet
43224 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
43225 The number of bytes to watch is specified by @var{kind}.
43237 @item z4,@var{addr},@var{kind}
43238 @itemx Z4,@var{addr},@var{kind}
43239 @cindex @samp{z4} packet
43240 @cindex @samp{Z4} packet
43241 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
43242 The number of bytes to watch is specified by @var{kind}.
43256 @node Stop Reply Packets
43257 @section Stop Reply Packets
43258 @cindex stop reply packets
43260 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
43261 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
43262 receive any of the below as a reply. Except for @samp{?}
43263 and @samp{vStopped}, that reply is only returned
43264 when the target halts. In the below the exact meaning of @dfn{signal
43265 number} is defined by the header @file{include/gdb/signals.h} in the
43266 @value{GDBN} source code.
43268 In non-stop mode, the server will simply reply @samp{OK} to commands
43269 such as @samp{vCont}; any stop will be the subject of a future
43270 notification. @xref{Remote Non-Stop}.
43272 As in the description of request packets, we include spaces in the
43273 reply templates for clarity; these are not part of the reply packet's
43274 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
43280 The program received signal number @var{AA} (a two-digit hexadecimal
43281 number). This is equivalent to a @samp{T} response with no
43282 @var{n}:@var{r} pairs.
43284 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
43285 @cindex @samp{T} packet reply
43286 The program received signal number @var{AA} (a two-digit hexadecimal
43287 number). This is equivalent to an @samp{S} response, except that the
43288 @samp{@var{n}:@var{r}} pairs can carry values of important registers
43289 and other information directly in the stop reply packet, reducing
43290 round-trip latency. Single-step and breakpoint traps are reported
43291 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
43295 If @var{n} is a hexadecimal number, it is a register number, and the
43296 corresponding @var{r} gives that register's value. The data @var{r} is a
43297 series of bytes in target byte order, with each byte given by a
43298 two-digit hex number.
43301 If @var{n} is @samp{thread}, then @var{r} is the thread ID of
43302 the stopped thread, as specified in @ref{thread-id syntax}.
43305 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
43306 the core on which the stop event was detected.
43309 If @var{n} is a recognized @dfn{stop reason}, it describes a more
43310 specific event that stopped the target. The currently defined stop
43311 reasons are listed below. The @var{aa} should be @samp{05}, the trap
43312 signal. At most one stop reason should be present.
43315 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
43316 and go on to the next; this allows us to extend the protocol in the
43320 The currently defined stop reasons are:
43326 The packet indicates a watchpoint hit, and @var{r} is the data address, in
43329 @item syscall_entry
43330 @itemx syscall_return
43331 The packet indicates a syscall entry or return, and @var{r} is the
43332 syscall number, in hex.
43334 @cindex shared library events, remote reply
43336 The packet indicates that the loaded libraries have changed.
43337 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
43338 list of loaded libraries. The @var{r} part is ignored.
43340 @cindex replay log events, remote reply
43342 The packet indicates that the target cannot continue replaying
43343 logged execution events, because it has reached the end (or the
43344 beginning when executing backward) of the log. The value of @var{r}
43345 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
43346 for more information.
43349 @anchor{swbreak stop reason}
43350 The packet indicates a software breakpoint instruction was executed,
43351 irrespective of whether it was @value{GDBN} that planted the
43352 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
43353 part must be left empty.
43355 On some architectures, such as x86, at the architecture level, when a
43356 breakpoint instruction executes the program counter points at the
43357 breakpoint address plus an offset. On such targets, the stub is
43358 responsible for adjusting the PC to point back at the breakpoint
43361 This packet should not be sent by default; older @value{GDBN} versions
43362 did not support it. @value{GDBN} requests it, by supplying an
43363 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
43364 remote stub must also supply the appropriate @samp{qSupported} feature
43365 indicating support.
43367 This packet is required for correct non-stop mode operation.
43370 The packet indicates the target stopped for a hardware breakpoint.
43371 The @var{r} part must be left empty.
43373 The same remarks about @samp{qSupported} and non-stop mode above
43376 @cindex fork events, remote reply
43378 The packet indicates that @code{fork} was called, and @var{r} is the
43379 thread ID of the new child process, as specified in @ref{thread-id
43380 syntax}. This packet is only applicable to targets that support fork
43383 This packet should not be sent by default; older @value{GDBN} versions
43384 did not support it. @value{GDBN} requests it, by supplying an
43385 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
43386 remote stub must also supply the appropriate @samp{qSupported} feature
43387 indicating support.
43389 @cindex vfork events, remote reply
43391 The packet indicates that @code{vfork} was called, and @var{r} is the
43392 thread ID of the new child process, as specified in @ref{thread-id
43393 syntax}. This packet is only applicable to targets that support vfork
43396 This packet should not be sent by default; older @value{GDBN} versions
43397 did not support it. @value{GDBN} requests it, by supplying an
43398 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
43399 remote stub must also supply the appropriate @samp{qSupported} feature
43400 indicating support.
43402 @cindex vforkdone events, remote reply
43404 The packet indicates that a child process created by a vfork
43405 has either called @code{exec} or terminated, so that the
43406 address spaces of the parent and child process are no longer
43407 shared. The @var{r} part is ignored. This packet is only
43408 applicable to targets that support vforkdone events.
43410 This packet should not be sent by default; older @value{GDBN} versions
43411 did not support it. @value{GDBN} requests it, by supplying an
43412 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
43413 remote stub must also supply the appropriate @samp{qSupported} feature
43414 indicating support.
43416 @cindex exec events, remote reply
43418 The packet indicates that @code{execve} was called, and @var{r}
43419 is the absolute pathname of the file that was executed, in hex.
43420 This packet is only applicable to targets that support exec events.
43422 This packet should not be sent by default; older @value{GDBN} versions
43423 did not support it. @value{GDBN} requests it, by supplying an
43424 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
43425 remote stub must also supply the appropriate @samp{qSupported} feature
43426 indicating support.
43428 @cindex thread clone events, remote reply
43429 @anchor{thread clone event}
43431 The packet indicates that @code{clone} was called, and @var{r} is the
43432 thread ID of the new child thread, as specified in @ref{thread-id
43433 syntax}. This packet is only applicable to targets that support clone
43436 This packet should not be sent by default; @value{GDBN} requests it
43437 with the @ref{QThreadOptions} packet.
43439 @cindex thread create event, remote reply
43440 @anchor{thread create event}
43442 The packet indicates that the thread was just created. The new thread
43443 is stopped until @value{GDBN} sets it running with a resumption packet
43444 (@pxref{vCont packet}). This packet should not be sent by default;
43445 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
43446 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
43447 @var{r} part is ignored.
43452 @itemx W @var{AA} ; process:@var{pid}
43453 The process exited, and @var{AA} is the exit status. This is only
43454 applicable to certain targets.
43456 The second form of the response, including the process ID of the
43457 exited process, can be used only when @value{GDBN} has reported
43458 support for multiprocess protocol extensions; see @ref{multiprocess
43459 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
43463 @itemx X @var{AA} ; process:@var{pid}
43464 The process terminated with signal @var{AA}.
43466 The second form of the response, including the process ID of the
43467 terminated process, can be used only when @value{GDBN} has reported
43468 support for multiprocess protocol extensions; see @ref{multiprocess
43469 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
43472 @anchor{thread exit event}
43473 @cindex thread exit event, remote reply
43474 @item w @var{AA} ; @var{tid}
43476 The thread exited, and @var{AA} is the exit status. This response
43477 should not be sent by default; @value{GDBN} requests it with either
43478 the @ref{QThreadEvents} or @ref{QThreadOptions} packets. See also
43479 @ref{thread create event} above. @var{AA} is formatted as a
43480 big-endian hex string.
43483 There are no resumed threads left in the target. In other words, even
43484 though the process is alive, the last resumed thread has exited. For
43485 example, say the target process has two threads: thread 1 and thread
43486 2. The client leaves thread 1 stopped, and resumes thread 2, which
43487 subsequently exits. At this point, even though the process is still
43488 alive, and thus no @samp{W} stop reply is sent, no thread is actually
43489 executing either. The @samp{N} stop reply thus informs the client
43490 that it can stop waiting for stop replies. This packet should not be
43491 sent by default; older @value{GDBN} versions did not support it.
43492 @value{GDBN} requests it, by supplying an appropriate
43493 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
43494 also supply the appropriate @samp{qSupported} feature indicating
43497 @item O @var{XX}@dots{}
43498 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
43499 written as the program's console output. This can happen at any time
43500 while the program is running and the debugger should continue to wait
43501 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
43503 @item F @var{call-id},@var{parameter}@dots{}
43504 @var{call-id} is the identifier which says which host system call should
43505 be called. This is just the name of the function. Translation into the
43506 correct system call is only applicable as it's defined in @value{GDBN}.
43507 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
43510 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
43511 this very system call.
43513 The target replies with this packet when it expects @value{GDBN} to
43514 call a host system call on behalf of the target. @value{GDBN} replies
43515 with an appropriate @samp{F} packet and keeps up waiting for the next
43516 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
43517 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
43518 Protocol Extension}, for more details.
43522 @node General Query Packets
43523 @section General Query Packets
43524 @cindex remote query requests
43526 Packets starting with @samp{q} are @dfn{general query packets};
43527 packets starting with @samp{Q} are @dfn{general set packets}. General
43528 query and set packets are a semi-unified form for retrieving and
43529 sending information to and from the stub.
43531 The initial letter of a query or set packet is followed by a name
43532 indicating what sort of thing the packet applies to. For example,
43533 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
43534 definitions with the stub. These packet names follow some
43539 The name must not contain commas, colons or semicolons.
43541 Most @value{GDBN} query and set packets have a leading upper case
43544 The names of custom vendor packets should use a company prefix, in
43545 lower case, followed by a period. For example, packets designed at
43546 the Acme Corporation might begin with @samp{qacme.foo} (for querying
43547 foos) or @samp{Qacme.bar} (for setting bars).
43550 The name of a query or set packet should be separated from any
43551 parameters by a @samp{:}; the parameters themselves should be
43552 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
43553 full packet name, and check for a separator or the end of the packet,
43554 in case two packet names share a common prefix. New packets should not begin
43555 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
43556 packets predate these conventions, and have arguments without any terminator
43557 for the packet name; we suspect they are in widespread use in places that
43558 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
43559 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
43562 Like the descriptions of the other packets, each description here
43563 has a template showing the packet's overall syntax, followed by an
43564 explanation of the packet's meaning. We include spaces in some of the
43565 templates for clarity; these are not part of the packet's syntax. No
43566 @value{GDBN} packet uses spaces to separate its components.
43568 Here are the currently defined query and set packets:
43574 Turn on or off the agent as a helper to perform some debugging operations
43575 delegated from @value{GDBN} (@pxref{Control Agent}).
43577 @item QAllow:@var{op}:@var{val}@dots{}
43578 @cindex @samp{QAllow} packet
43579 Specify which operations @value{GDBN} expects to request of the
43580 target, as a semicolon-separated list of operation name and value
43581 pairs. Possible values for @var{op} include @samp{WriteReg},
43582 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
43583 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
43584 indicating that @value{GDBN} will not request the operation, or 1,
43585 indicating that it may. (The target can then use this to set up its
43586 own internals optimally, for instance if the debugger never expects to
43587 insert breakpoints, it may not need to install its own trap handler.)
43590 @cindex current thread, remote request
43591 @cindex @samp{qC} packet
43592 Return the current thread ID.
43596 @item QC @var{thread-id}
43597 Where @var{thread-id} is a thread ID as documented in
43598 @ref{thread-id syntax}.
43599 @item @r{(anything else)}
43600 Any other reply implies the old thread ID.
43603 @item qCRC:@var{addr},@var{length}
43604 @cindex CRC of memory block, remote request
43605 @cindex @samp{qCRC} packet
43606 @anchor{qCRC packet}
43607 Compute the CRC checksum of a block of memory using CRC-32 defined in
43608 IEEE 802.3. The CRC is computed byte at a time, taking the most
43609 significant bit of each byte first. The initial pattern code
43610 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
43612 @emph{Note:} This is the same CRC used in validating separate debug
43613 files (@pxref{Separate Debug Files, , Debugging Information in Separate
43614 Files}). However the algorithm is slightly different. When validating
43615 separate debug files, the CRC is computed taking the @emph{least}
43616 significant bit of each byte first, and the final result is inverted to
43617 detect trailing zeros.
43622 An error (such as memory fault)
43623 @item C @var{crc32}
43624 The specified memory region's checksum is @var{crc32}.
43627 @item QDisableRandomization:@var{value}
43628 @cindex disable address space randomization, remote request
43629 @cindex @samp{QDisableRandomization} packet
43630 Some target operating systems will randomize the virtual address space
43631 of the inferior process as a security feature, but provide a feature
43632 to disable such randomization, e.g.@: to allow for a more deterministic
43633 debugging experience. On such systems, this packet with a @var{value}
43634 of 1 directs the target to disable address space randomization for
43635 processes subsequently started via @samp{vRun} packets, while a packet
43636 with a @var{value} of 0 tells the target to enable address space
43639 This packet is only available in extended mode (@pxref{extended mode}).
43644 The request succeeded.
43647 An error occurred. The error number @var{nn} is given as hex digits.
43650 An empty reply indicates that @samp{QDisableRandomization} is not supported
43654 This packet is not probed by default; the remote stub must request it,
43655 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43656 This should only be done on targets that actually support disabling
43657 address space randomization.
43659 @item QStartupWithShell:@var{value}
43660 @cindex startup with shell, remote request
43661 @cindex @samp{QStartupWithShell} packet
43662 On UNIX-like targets, it is possible to start the inferior using a
43663 shell program. This is the default behavior on both @value{GDBN} and
43664 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
43665 used to inform @command{gdbserver} whether it should start the
43666 inferior using a shell or not.
43668 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
43669 to start the inferior. If @var{value} is @samp{1},
43670 @command{gdbserver} will use a shell to start the inferior. All other
43671 values are considered an error.
43673 This packet is only available in extended mode (@pxref{extended
43679 The request succeeded.
43682 An error occurred. The error number @var{nn} is given as hex digits.
43685 This packet is not probed by default; the remote stub must request it,
43686 by supplying an appropriate @samp{qSupported} response
43687 (@pxref{qSupported}). This should only be done on targets that
43688 actually support starting the inferior using a shell.
43690 Use of this packet is controlled by the @code{set startup-with-shell}
43691 command; @pxref{set startup-with-shell}.
43693 @item QEnvironmentHexEncoded:@var{hex-value}
43694 @anchor{QEnvironmentHexEncoded}
43695 @cindex set environment variable, remote request
43696 @cindex @samp{QEnvironmentHexEncoded} packet
43697 On UNIX-like targets, it is possible to set environment variables that
43698 will be passed to the inferior during the startup process. This
43699 packet is used to inform @command{gdbserver} of an environment
43700 variable that has been defined by the user on @value{GDBN} (@pxref{set
43703 The packet is composed by @var{hex-value}, an hex encoded
43704 representation of the @var{name=value} format representing an
43705 environment variable. The name of the environment variable is
43706 represented by @var{name}, and the value to be assigned to the
43707 environment variable is represented by @var{value}. If the variable
43708 has no value (i.e., the value is @code{null}), then @var{value} will
43711 This packet is only available in extended mode (@pxref{extended
43717 The request succeeded.
43720 This packet is not probed by default; the remote stub must request it,
43721 by supplying an appropriate @samp{qSupported} response
43722 (@pxref{qSupported}). This should only be done on targets that
43723 actually support passing environment variables to the starting
43726 This packet is related to the @code{set environment} command;
43727 @pxref{set environment}.
43729 @item QEnvironmentUnset:@var{hex-value}
43730 @anchor{QEnvironmentUnset}
43731 @cindex unset environment variable, remote request
43732 @cindex @samp{QEnvironmentUnset} packet
43733 On UNIX-like targets, it is possible to unset environment variables
43734 before starting the inferior in the remote target. This packet is
43735 used to inform @command{gdbserver} of an environment variable that has
43736 been unset by the user on @value{GDBN} (@pxref{unset environment}).
43738 The packet is composed by @var{hex-value}, an hex encoded
43739 representation of the name of the environment variable to be unset.
43741 This packet is only available in extended mode (@pxref{extended
43747 The request succeeded.
43750 This packet is not probed by default; the remote stub must request it,
43751 by supplying an appropriate @samp{qSupported} response
43752 (@pxref{qSupported}). This should only be done on targets that
43753 actually support passing environment variables to the starting
43756 This packet is related to the @code{unset environment} command;
43757 @pxref{unset environment}.
43759 @item QEnvironmentReset
43760 @anchor{QEnvironmentReset}
43761 @cindex reset environment, remote request
43762 @cindex @samp{QEnvironmentReset} packet
43763 On UNIX-like targets, this packet is used to reset the state of
43764 environment variables in the remote target before starting the
43765 inferior. In this context, reset means unsetting all environment
43766 variables that were previously set by the user (i.e., were not
43767 initially present in the environment). It is sent to
43768 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
43769 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
43770 (@pxref{QEnvironmentUnset}) packets.
43772 This packet is only available in extended mode (@pxref{extended
43778 The request succeeded.
43781 This packet is not probed by default; the remote stub must request it,
43782 by supplying an appropriate @samp{qSupported} response
43783 (@pxref{qSupported}). This should only be done on targets that
43784 actually support passing environment variables to the starting
43787 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
43788 @anchor{QSetWorkingDir packet}
43789 @cindex set working directory, remote request
43790 @cindex @samp{QSetWorkingDir} packet
43791 This packet is used to inform the remote server of the intended
43792 current working directory for programs that are going to be executed.
43794 The packet is composed by @var{directory}, an hex encoded
43795 representation of the directory that the remote inferior will use as
43796 its current working directory. If @var{directory} is an empty string,
43797 the remote server should reset the inferior's current working
43798 directory to its original, empty value.
43800 This packet is only available in extended mode (@pxref{extended
43806 The request succeeded.
43810 @itemx qsThreadInfo
43811 @cindex list active threads, remote request
43812 @cindex @samp{qfThreadInfo} packet
43813 @cindex @samp{qsThreadInfo} packet
43814 Obtain a list of all active thread IDs from the target (OS). Since there
43815 may be too many active threads to fit into one reply packet, this query
43816 works iteratively: it may require more than one query/reply sequence to
43817 obtain the entire list of threads. The first query of the sequence will
43818 be the @samp{qfThreadInfo} query; subsequent queries in the
43819 sequence will be the @samp{qsThreadInfo} query.
43821 NOTE: This packet replaces the @samp{qL} query (see below).
43825 @item m @var{thread-id}
43827 @item m @var{thread-id},@var{thread-id}@dots{}
43828 a comma-separated list of thread IDs
43830 (lower case letter @samp{L}) denotes end of list.
43833 In response to each query, the target will reply with a list of one or
43834 more thread IDs, separated by commas.
43835 @value{GDBN} will respond to each reply with a request for more thread
43836 ids (using the @samp{qs} form of the query), until the target responds
43837 with @samp{l} (lower-case ell, for @dfn{last}).
43838 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
43841 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
43842 initial connection with the remote target, and the very first thread ID
43843 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
43844 message. Therefore, the stub should ensure that the first thread ID in
43845 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
43847 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
43848 @cindex get thread-local storage address, remote request
43849 @cindex @samp{qGetTLSAddr} packet
43850 Fetch the address associated with thread local storage specified
43851 by @var{thread-id}, @var{offset}, and @var{lm}.
43853 @var{thread-id} is the thread ID associated with the
43854 thread for which to fetch the TLS address. @xref{thread-id syntax}.
43856 @var{offset} is the (big endian, hex encoded) offset associated with the
43857 thread local variable. (This offset is obtained from the debug
43858 information associated with the variable.)
43860 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
43861 load module associated with the thread local storage. For example,
43862 a @sc{gnu}/Linux system will pass the link map address of the shared
43863 object associated with the thread local storage under consideration.
43864 Other operating environments may choose to represent the load module
43865 differently, so the precise meaning of this parameter will vary.
43869 @item @var{XX}@dots{}
43870 Hex encoded (big endian) bytes representing the address of the thread
43871 local storage requested.
43874 An error occurred. The error number @var{nn} is given as hex digits.
43877 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
43880 @item qGetTIBAddr:@var{thread-id}
43881 @cindex get thread information block address
43882 @cindex @samp{qGetTIBAddr} packet
43883 Fetch address of the Windows OS specific Thread Information Block.
43885 @var{thread-id} is the thread ID associated with the thread.
43889 @item @var{XX}@dots{}
43890 Hex encoded (big endian) bytes representing the linear address of the
43891 thread information block.
43894 An error occurred. This means that either the thread was not found, or the
43895 address could not be retrieved.
43898 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
43901 @item qL @var{startflag} @var{threadcount} @var{nextthread}
43902 Obtain thread information from RTOS. Where: @var{startflag} (one hex
43903 digit) is one to indicate the first query and zero to indicate a
43904 subsequent query; @var{threadcount} (two hex digits) is the maximum
43905 number of threads the response packet can contain; and @var{nextthread}
43906 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
43907 returned in the response as @var{argthread}.
43909 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
43913 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
43914 Where: @var{count} (two hex digits) is the number of threads being
43915 returned; @var{done} (one hex digit) is zero to indicate more threads
43916 and one indicates no further threads; @var{argthreadid} (eight hex
43917 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
43918 is a sequence of thread IDs, @var{threadid} (eight hex
43919 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
43922 @item qMemTags:@var{start address},@var{length}:@var{type}
43924 @cindex fetch memory tags
43925 @cindex @samp{qMemTags} packet
43926 Fetch memory tags of type @var{type} from the address range
43927 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
43928 target is responsible for calculating how many tags will be returned, as this
43929 is architecture-specific.
43931 @var{start address} is the starting address of the memory range.
43933 @var{length} is the length, in bytes, of the memory range.
43935 @var{type} is the type of tag the request wants to fetch. The type is a signed
43940 @item @var{mxx}@dots{}
43941 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
43942 tags found in the requested memory range.
43945 An error occurred. This means that fetching of memory tags failed for some
43949 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
43950 although this should not happen given @value{GDBN} will only send this packet
43951 if the stub has advertised support for memory tagging via @samp{qSupported}.
43954 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
43956 @cindex store memory tags
43957 @cindex @samp{QMemTags} packet
43958 Store memory tags of type @var{type} to the address range
43959 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
43960 target is responsible for interpreting the type, the tag bytes and modifying
43961 the memory tag granules accordingly, given this is architecture-specific.
43963 The interpretation of how many tags (@var{nt}) should be written to how many
43964 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
43965 implementation-specific, but the following is suggested.
43967 If the number of memory tags, @var{nt}, is greater than or equal to the
43968 number of memory tag granules, @var{ng}, only @var{ng} tags will be
43971 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
43972 and the tag bytes will be used as a pattern that will get repeated until
43973 @var{ng} tags are stored.
43975 @var{start address} is the starting address of the memory range. The address
43976 does not have any restriction on alignment or size.
43978 @var{length} is the length, in bytes, of the memory range.
43980 @var{type} is the type of tag the request wants to fetch. The type is a signed
43983 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
43984 interpreted by the target. Each pair of hex digits is interpreted as a
43990 The request was successful and the memory tag granules were modified
43994 An error occurred. This means that modifying the memory tag granules failed
43998 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
43999 although this should not happen given @value{GDBN} will only send this packet
44000 if the stub has advertised support for memory tagging via @samp{qSupported}.
44004 @cindex section offsets, remote request
44005 @cindex @samp{qOffsets} packet
44006 Get section offsets that the target used when relocating the downloaded
44011 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
44012 Relocate the @code{Text} section by @var{xxx} from its original address.
44013 Relocate the @code{Data} section by @var{yyy} from its original address.
44014 If the object file format provides segment information (e.g.@: @sc{elf}
44015 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
44016 segments by the supplied offsets.
44018 @emph{Note: while a @code{Bss} offset may be included in the response,
44019 @value{GDBN} ignores this and instead applies the @code{Data} offset
44020 to the @code{Bss} section.}
44022 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
44023 Relocate the first segment of the object file, which conventionally
44024 contains program code, to a starting address of @var{xxx}. If
44025 @samp{DataSeg} is specified, relocate the second segment, which
44026 conventionally contains modifiable data, to a starting address of
44027 @var{yyy}. @value{GDBN} will report an error if the object file
44028 does not contain segment information, or does not contain at least
44029 as many segments as mentioned in the reply. Extra segments are
44030 kept at fixed offsets relative to the last relocated segment.
44033 @item qP @var{mode} @var{thread-id}
44034 @cindex thread information, remote request
44035 @cindex @samp{qP} packet
44036 Returns information on @var{thread-id}. Where: @var{mode} is a hex
44037 encoded 32 bit mode; @var{thread-id} is a thread ID
44038 (@pxref{thread-id syntax}).
44040 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
44043 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
44047 @cindex non-stop mode, remote request
44048 @cindex @samp{QNonStop} packet
44050 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
44051 @xref{Remote Non-Stop}, for more information.
44056 The request succeeded.
44059 An error occurred. The error number @var{nn} is given as hex digits.
44062 An empty reply indicates that @samp{QNonStop} is not supported by
44066 This packet is not probed by default; the remote stub must request it,
44067 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
44068 Use of this packet is controlled by the @code{set non-stop} command;
44069 @pxref{Non-Stop Mode}.
44071 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
44072 @itemx QCatchSyscalls:0
44073 @cindex catch syscalls from inferior, remote request
44074 @cindex @samp{QCatchSyscalls} packet
44075 @anchor{QCatchSyscalls}
44076 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
44077 catching syscalls from the inferior process.
44079 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
44080 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
44081 is listed, every system call should be reported.
44083 Note that if a syscall not in the list is reported, @value{GDBN} will
44084 still filter the event according to its own list from all corresponding
44085 @code{catch syscall} commands. However, it is more efficient to only
44086 report the requested syscalls.
44088 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
44089 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
44091 If the inferior process execs, the state of @samp{QCatchSyscalls} is
44092 kept for the new process too. On targets where exec may affect syscall
44093 numbers, for example with exec between 32 and 64-bit processes, the
44094 client should send a new packet with the new syscall list.
44099 The request succeeded.
44102 An error occurred. @var{nn} are hex digits.
44105 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
44109 Use of this packet is controlled by the @code{set remote catch-syscalls}
44110 command (@pxref{Remote Configuration, set remote catch-syscalls}).
44111 This packet is not probed by default; the remote stub must request it,
44112 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
44114 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
44115 @cindex pass signals to inferior, remote request
44116 @cindex @samp{QPassSignals} packet
44117 @anchor{QPassSignals}
44118 Each listed @var{signal} should be passed directly to the inferior process.
44119 Signals are numbered identically to continue packets and stop replies
44120 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
44121 strictly greater than the previous item. These signals do not need to stop
44122 the inferior, or be reported to @value{GDBN}. All other signals should be
44123 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
44124 combine; any earlier @samp{QPassSignals} list is completely replaced by the
44125 new list. This packet improves performance when using @samp{handle
44126 @var{signal} nostop noprint pass}.
44131 The request succeeded.
44134 An error occurred. The error number @var{nn} is given as hex digits.
44137 An empty reply indicates that @samp{QPassSignals} is not supported by
44141 Use of this packet is controlled by the @code{set remote pass-signals}
44142 command (@pxref{Remote Configuration, set remote pass-signals}).
44143 This packet is not probed by default; the remote stub must request it,
44144 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
44146 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
44147 @cindex signals the inferior may see, remote request
44148 @cindex @samp{QProgramSignals} packet
44149 @anchor{QProgramSignals}
44150 Each listed @var{signal} may be delivered to the inferior process.
44151 Others should be silently discarded.
44153 In some cases, the remote stub may need to decide whether to deliver a
44154 signal to the program or not without @value{GDBN} involvement. One
44155 example of that is while detaching --- the program's threads may have
44156 stopped for signals that haven't yet had a chance of being reported to
44157 @value{GDBN}, and so the remote stub can use the signal list specified
44158 by this packet to know whether to deliver or ignore those pending
44161 This does not influence whether to deliver a signal as requested by a
44162 resumption packet (@pxref{vCont packet}).
44164 Signals are numbered identically to continue packets and stop replies
44165 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
44166 strictly greater than the previous item. Multiple
44167 @samp{QProgramSignals} packets do not combine; any earlier
44168 @samp{QProgramSignals} list is completely replaced by the new list.
44173 The request succeeded.
44176 An error occurred. The error number @var{nn} is given as hex digits.
44179 An empty reply indicates that @samp{QProgramSignals} is not supported
44183 Use of this packet is controlled by the @code{set remote program-signals}
44184 command (@pxref{Remote Configuration, set remote program-signals}).
44185 This packet is not probed by default; the remote stub must request it,
44186 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
44188 @anchor{QThreadEvents}
44189 @item QThreadEvents:1
44190 @itemx QThreadEvents:0
44191 @cindex thread create/exit events, remote request
44192 @cindex @samp{QThreadEvents} packet
44194 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
44195 reporting of thread create and exit events. @xref{thread create
44196 event}, for the reply specifications. For example, this is used in
44197 non-stop mode when @value{GDBN} stops a set of threads and
44198 synchronously waits for the their corresponding stop replies. Without
44199 exit events, if one of the threads exits, @value{GDBN} would hang
44200 forever not knowing that it should no longer expect a stop for that
44201 same thread. @value{GDBN} does not enable this feature unless the
44202 stub reports that it supports it by including @samp{QThreadEvents+} in
44203 its @samp{qSupported} reply.
44205 This packet always enables/disables event reporting for all threads of
44206 all processes under control of the remote stub. For per-thread
44207 control of optional event reporting, see the @ref{QThreadOptions}
44213 The request succeeded.
44216 An error occurred. The error number @var{nn} is given as hex digits.
44219 An empty reply indicates that @samp{QThreadEvents} is not supported by
44223 Use of this packet is controlled by the @code{set remote thread-events}
44224 command (@pxref{Remote Configuration, set remote thread-events}).
44226 @anchor{QThreadOptions}
44227 @item QThreadOptions@r{[};@var{options}@r{[}:@var{thread-id}@r{]]}@dots{}
44228 @cindex thread options, remote request
44229 @cindex @samp{QThreadOptions} packet
44231 For each inferior thread, the last @var{options} in the list with a
44232 matching @var{thread-id} are applied. Any options previously set on a
44233 thread are discarded and replaced by the new options specified.
44234 Threads that do not match any @var{thread-id} retain their
44235 previously-set options. Thread IDs are specified using the syntax
44236 described in @ref{thread-id syntax}. If multiprocess extensions
44237 (@pxref{multiprocess extensions}) are supported, options can be
44238 specified to apply to all threads of a process by using the
44239 @samp{p@var{pid}.-1} form of @var{thread-id}. Options with no
44240 @var{thread-id} apply to all threads. Specifying no options value is
44241 an error. Zero is a valid value.
44243 @var{options} is an hexadecimal integer specifying the enabled thread
44244 options, and is the bitwise @code{OR} of the following values. All
44245 values are given in hexadecimal representation.
44248 @item GDB_THREAD_OPTION_CLONE (0x1)
44249 Report thread clone events (@pxref{thread clone event}). This is only
44250 meaningful for targets that support clone events (e.g., GNU/Linux
44253 @item GDB_THREAD_OPTION_EXIT (0x2)
44254 Report thread exit events (@pxref{thread exit event}).
44259 For example, @value{GDBN} enables the @code{GDB_THREAD_OPTION_EXIT}
44260 and @code{GDB_THREAD_OPTION_CLONE} options when single-stepping a
44261 thread past a breakpoint, for the following reasons:
44265 If the single-stepped thread exits (e.g., it executes a thread exit
44266 system call), enabling @code{GDB_THREAD_OPTION_EXIT} prevents
44267 @value{GDBN} from waiting forever, not knowing that it should no
44268 longer expect a stop for that same thread, and blocking other threads
44272 If the single-stepped thread spawns a new clone child (i.e., it
44273 executes a clone system call), enabling @code{GDB_THREAD_OPTION_CLONE}
44274 halts the cloned thread before it executes any instructions, and thus
44275 prevents the following problematic situations:
44279 If the breakpoint is stepped-over in-line, the spawned thread would
44280 incorrectly run free while the breakpoint being stepped over is not
44281 inserted, and thus the cloned thread may potentially run past the
44282 breakpoint without stopping for it;
44285 If displaced (out-of-line) stepping is used, the cloned thread starts
44286 running at the out-of-line PC, leading to undefined behavior, usually
44287 crashing or corrupting data.
44292 New threads start with thread options cleared.
44294 @value{GDBN} does not enable this feature unless the stub reports that
44295 it supports it by including
44296 @samp{QThreadOptions=@var{supported_options}} in its @samp{qSupported}
44302 The request succeeded.
44305 An error occurred. The error number @var{nn} is given as hex digits.
44308 An empty reply indicates that @samp{QThreadOptions} is not supported by
44312 Use of this packet is controlled by the @code{set remote thread-options}
44313 command (@pxref{Remote Configuration, set remote thread-options}).
44315 @item qRcmd,@var{command}
44316 @cindex execute remote command, remote request
44317 @cindex @samp{qRcmd} packet
44318 @var{command} (hex encoded) is passed to the local interpreter for
44319 execution. Invalid commands should be reported using the output
44320 string. Before the final result packet, the target may also respond
44321 with a number of intermediate @samp{O@var{output}} console output
44322 packets. @emph{Implementors should note that providing access to a
44323 stubs's interpreter may have security implications}.
44328 A command response with no output.
44330 A command response with the hex encoded output string @var{OUTPUT}.
44332 Indicate a badly formed request. The error number @var{NN} is given as
44335 An empty reply indicates that @samp{qRcmd} is not recognized.
44338 (Note that the @code{qRcmd} packet's name is separated from the
44339 command by a @samp{,}, not a @samp{:}, contrary to the naming
44340 conventions above. Please don't use this packet as a model for new
44343 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
44344 @cindex searching memory, in remote debugging
44346 @cindex @samp{qSearch:memory} packet
44348 @cindex @samp{qSearch memory} packet
44349 @anchor{qSearch memory}
44350 Search @var{length} bytes at @var{address} for @var{search-pattern}.
44351 Both @var{address} and @var{length} are encoded in hex;
44352 @var{search-pattern} is a sequence of bytes, also hex encoded.
44357 The pattern was not found.
44359 The pattern was found at @var{address}.
44361 A badly formed request or an error was encountered while searching memory.
44363 An empty reply indicates that @samp{qSearch:memory} is not recognized.
44366 @item QStartNoAckMode
44367 @cindex @samp{QStartNoAckMode} packet
44368 @anchor{QStartNoAckMode}
44369 Request that the remote stub disable the normal @samp{+}/@samp{-}
44370 protocol acknowledgments (@pxref{Packet Acknowledgment}).
44375 The stub has switched to no-acknowledgment mode.
44376 @value{GDBN} acknowledges this response,
44377 but neither the stub nor @value{GDBN} shall send or expect further
44378 @samp{+}/@samp{-} acknowledgments in the current connection.
44380 An empty reply indicates that the stub does not support no-acknowledgment mode.
44383 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
44384 @cindex supported packets, remote query
44385 @cindex features of the remote protocol
44386 @cindex @samp{qSupported} packet
44387 @anchor{qSupported}
44388 Tell the remote stub about features supported by @value{GDBN}, and
44389 query the stub for features it supports. This packet allows
44390 @value{GDBN} and the remote stub to take advantage of each others'
44391 features. @samp{qSupported} also consolidates multiple feature probes
44392 at startup, to improve @value{GDBN} performance---a single larger
44393 packet performs better than multiple smaller probe packets on
44394 high-latency links. Some features may enable behavior which must not
44395 be on by default, e.g.@: because it would confuse older clients or
44396 stubs. Other features may describe packets which could be
44397 automatically probed for, but are not. These features must be
44398 reported before @value{GDBN} will use them. This ``default
44399 unsupported'' behavior is not appropriate for all packets, but it
44400 helps to keep the initial connection time under control with new
44401 versions of @value{GDBN} which support increasing numbers of packets.
44405 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
44406 The stub supports or does not support each returned @var{stubfeature},
44407 depending on the form of each @var{stubfeature} (see below for the
44410 An empty reply indicates that @samp{qSupported} is not recognized,
44411 or that no features needed to be reported to @value{GDBN}.
44414 The allowed forms for each feature (either a @var{gdbfeature} in the
44415 @samp{qSupported} packet, or a @var{stubfeature} in the response)
44419 @item @var{name}=@var{value}
44420 The remote protocol feature @var{name} is supported, and associated
44421 with the specified @var{value}. The format of @var{value} depends
44422 on the feature, but it must not include a semicolon.
44424 The remote protocol feature @var{name} is supported, and does not
44425 need an associated value.
44427 The remote protocol feature @var{name} is not supported.
44429 The remote protocol feature @var{name} may be supported, and
44430 @value{GDBN} should auto-detect support in some other way when it is
44431 needed. This form will not be used for @var{gdbfeature} notifications,
44432 but may be used for @var{stubfeature} responses.
44435 Whenever the stub receives a @samp{qSupported} request, the
44436 supplied set of @value{GDBN} features should override any previous
44437 request. This allows @value{GDBN} to put the stub in a known
44438 state, even if the stub had previously been communicating with
44439 a different version of @value{GDBN}.
44441 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
44446 This feature indicates whether @value{GDBN} supports multiprocess
44447 extensions to the remote protocol. @value{GDBN} does not use such
44448 extensions unless the stub also reports that it supports them by
44449 including @samp{multiprocess+} in its @samp{qSupported} reply.
44450 @xref{multiprocess extensions}, for details.
44453 This feature indicates that @value{GDBN} supports the XML target
44454 description. If the stub sees @samp{xmlRegisters=} with target
44455 specific strings separated by a comma, it will report register
44459 This feature indicates whether @value{GDBN} supports the
44460 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
44461 instruction reply packet}).
44464 This feature indicates whether @value{GDBN} supports the swbreak stop
44465 reason in stop replies. @xref{swbreak stop reason}, for details.
44468 This feature indicates whether @value{GDBN} supports the hwbreak stop
44469 reason in stop replies. @xref{swbreak stop reason}, for details.
44472 This feature indicates whether @value{GDBN} supports fork event
44473 extensions to the remote protocol. @value{GDBN} does not use such
44474 extensions unless the stub also reports that it supports them by
44475 including @samp{fork-events+} in its @samp{qSupported} reply.
44478 This feature indicates whether @value{GDBN} supports vfork event
44479 extensions to the remote protocol. @value{GDBN} does not use such
44480 extensions unless the stub also reports that it supports them by
44481 including @samp{vfork-events+} in its @samp{qSupported} reply.
44484 This feature indicates whether @value{GDBN} supports exec event
44485 extensions to the remote protocol. @value{GDBN} does not use such
44486 extensions unless the stub also reports that it supports them by
44487 including @samp{exec-events+} in its @samp{qSupported} reply.
44489 @item vContSupported
44490 This feature indicates whether @value{GDBN} wants to know the
44491 supported actions in the reply to @samp{vCont?} packet.
44494 Stubs should ignore any unknown values for
44495 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
44496 packet supports receiving packets of unlimited length (earlier
44497 versions of @value{GDBN} may reject overly long responses). Additional values
44498 for @var{gdbfeature} may be defined in the future to let the stub take
44499 advantage of new features in @value{GDBN}, e.g.@: incompatible
44500 improvements in the remote protocol---the @samp{multiprocess} feature is
44501 an example of such a feature. The stub's reply should be independent
44502 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
44503 describes all the features it supports, and then the stub replies with
44504 all the features it supports.
44506 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
44507 responses, as long as each response uses one of the standard forms.
44509 Some features are flags. A stub which supports a flag feature
44510 should respond with a @samp{+} form response. Other features
44511 require values, and the stub should respond with an @samp{=}
44514 Each feature has a default value, which @value{GDBN} will use if
44515 @samp{qSupported} is not available or if the feature is not mentioned
44516 in the @samp{qSupported} response. The default values are fixed; a
44517 stub is free to omit any feature responses that match the defaults.
44519 Not all features can be probed, but for those which can, the probing
44520 mechanism is useful: in some cases, a stub's internal
44521 architecture may not allow the protocol layer to know some information
44522 about the underlying target in advance. This is especially common in
44523 stubs which may be configured for multiple targets.
44525 These are the currently defined stub features and their properties:
44527 @multitable @columnfractions 0.35 0.2 0.12 0.2
44528 @c NOTE: The first row should be @headitem, but we do not yet require
44529 @c a new enough version of Texinfo (4.7) to use @headitem.
44531 @tab Value Required
44535 @item @samp{PacketSize}
44540 @item @samp{qXfer:auxv:read}
44545 @item @samp{qXfer:btrace:read}
44550 @item @samp{qXfer:btrace-conf:read}
44555 @item @samp{qXfer:exec-file:read}
44560 @item @samp{qXfer:features:read}
44565 @item @samp{qXfer:libraries:read}
44570 @item @samp{qXfer:libraries-svr4:read}
44575 @item @samp{augmented-libraries-svr4-read}
44580 @item @samp{qXfer:memory-map:read}
44585 @item @samp{qXfer:sdata:read}
44590 @item @samp{qXfer:siginfo:read}
44595 @item @samp{qXfer:siginfo:write}
44600 @item @samp{qXfer:threads:read}
44605 @item @samp{qXfer:traceframe-info:read}
44610 @item @samp{qXfer:uib:read}
44615 @item @samp{qXfer:fdpic:read}
44620 @item @samp{Qbtrace:off}
44625 @item @samp{Qbtrace:bts}
44630 @item @samp{Qbtrace:pt}
44635 @item @samp{Qbtrace-conf:bts:size}
44640 @item @samp{Qbtrace-conf:pt:size}
44645 @item @samp{QNonStop}
44650 @item @samp{QCatchSyscalls}
44655 @item @samp{QPassSignals}
44660 @item @samp{QStartNoAckMode}
44665 @item @samp{multiprocess}
44670 @item @samp{ConditionalBreakpoints}
44675 @item @samp{ConditionalTracepoints}
44680 @item @samp{ReverseContinue}
44685 @item @samp{ReverseStep}
44690 @item @samp{TracepointSource}
44695 @item @samp{QAgent}
44700 @item @samp{QAllow}
44705 @item @samp{QDisableRandomization}
44710 @item @samp{EnableDisableTracepoints}
44715 @item @samp{QTBuffer:size}
44720 @item @samp{tracenz}
44725 @item @samp{BreakpointCommands}
44730 @item @samp{swbreak}
44735 @item @samp{hwbreak}
44740 @item @samp{fork-events}
44745 @item @samp{vfork-events}
44750 @item @samp{exec-events}
44755 @item @samp{QThreadEvents}
44760 @item @samp{QThreadOptions}
44765 @item @samp{no-resumed}
44770 @item @samp{memory-tagging}
44777 These are the currently defined stub features, in more detail:
44780 @cindex packet size, remote protocol
44781 @item PacketSize=@var{bytes}
44782 The remote stub can accept packets up to at least @var{bytes} in
44783 length. @value{GDBN} will send packets up to this size for bulk
44784 transfers, and will never send larger packets. This is a limit on the
44785 data characters in the packet, including the frame and checksum.
44786 There is no trailing NUL byte in a remote protocol packet; if the stub
44787 stores packets in a NUL-terminated format, it should allow an extra
44788 byte in its buffer for the NUL. If this stub feature is not supported,
44789 @value{GDBN} guesses based on the size of the @samp{g} packet response.
44791 @item qXfer:auxv:read
44792 The remote stub understands the @samp{qXfer:auxv:read} packet
44793 (@pxref{qXfer auxiliary vector read}).
44795 @item qXfer:btrace:read
44796 The remote stub understands the @samp{qXfer:btrace:read}
44797 packet (@pxref{qXfer btrace read}).
44799 @item qXfer:btrace-conf:read
44800 The remote stub understands the @samp{qXfer:btrace-conf:read}
44801 packet (@pxref{qXfer btrace-conf read}).
44803 @item qXfer:exec-file:read
44804 The remote stub understands the @samp{qXfer:exec-file:read} packet
44805 (@pxref{qXfer executable filename read}).
44807 @item qXfer:features:read
44808 The remote stub understands the @samp{qXfer:features:read} packet
44809 (@pxref{qXfer target description read}).
44811 @item qXfer:libraries:read
44812 The remote stub understands the @samp{qXfer:libraries:read} packet
44813 (@pxref{qXfer library list read}).
44815 @item qXfer:libraries-svr4:read
44816 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
44817 (@pxref{qXfer svr4 library list read}).
44819 @item augmented-libraries-svr4-read
44820 The remote stub understands the augmented form of the
44821 @samp{qXfer:libraries-svr4:read} packet
44822 (@pxref{qXfer svr4 library list read}).
44824 @item qXfer:memory-map:read
44825 The remote stub understands the @samp{qXfer:memory-map:read} packet
44826 (@pxref{qXfer memory map read}).
44828 @item qXfer:sdata:read
44829 The remote stub understands the @samp{qXfer:sdata:read} packet
44830 (@pxref{qXfer sdata read}).
44832 @item qXfer:siginfo:read
44833 The remote stub understands the @samp{qXfer:siginfo:read} packet
44834 (@pxref{qXfer siginfo read}).
44836 @item qXfer:siginfo:write
44837 The remote stub understands the @samp{qXfer:siginfo:write} packet
44838 (@pxref{qXfer siginfo write}).
44840 @item qXfer:threads:read
44841 The remote stub understands the @samp{qXfer:threads:read} packet
44842 (@pxref{qXfer threads read}).
44844 @item qXfer:traceframe-info:read
44845 The remote stub understands the @samp{qXfer:traceframe-info:read}
44846 packet (@pxref{qXfer traceframe info read}).
44848 @item qXfer:uib:read
44849 The remote stub understands the @samp{qXfer:uib:read}
44850 packet (@pxref{qXfer unwind info block}).
44852 @item qXfer:fdpic:read
44853 The remote stub understands the @samp{qXfer:fdpic:read}
44854 packet (@pxref{qXfer fdpic loadmap read}).
44857 The remote stub understands the @samp{QNonStop} packet
44858 (@pxref{QNonStop}).
44860 @item QCatchSyscalls
44861 The remote stub understands the @samp{QCatchSyscalls} packet
44862 (@pxref{QCatchSyscalls}).
44865 The remote stub understands the @samp{QPassSignals} packet
44866 (@pxref{QPassSignals}).
44868 @item QStartNoAckMode
44869 The remote stub understands the @samp{QStartNoAckMode} packet and
44870 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
44873 @anchor{multiprocess extensions}
44874 @cindex multiprocess extensions, in remote protocol
44875 The remote stub understands the multiprocess extensions to the remote
44876 protocol syntax. The multiprocess extensions affect the syntax of
44877 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
44878 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
44879 replies. Note that reporting this feature indicates support for the
44880 syntactic extensions only, not that the stub necessarily supports
44881 debugging of more than one process at a time. The stub must not use
44882 multiprocess extensions in packet replies unless @value{GDBN} has also
44883 indicated it supports them in its @samp{qSupported} request.
44885 @item qXfer:osdata:read
44886 The remote stub understands the @samp{qXfer:osdata:read} packet
44887 ((@pxref{qXfer osdata read}).
44889 @item ConditionalBreakpoints
44890 The target accepts and implements evaluation of conditional expressions
44891 defined for breakpoints. The target will only report breakpoint triggers
44892 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
44894 @item ConditionalTracepoints
44895 The remote stub accepts and implements conditional expressions defined
44896 for tracepoints (@pxref{Tracepoint Conditions}).
44898 @item ReverseContinue
44899 The remote stub accepts and implements the reverse continue packet
44903 The remote stub accepts and implements the reverse step packet
44906 @item TracepointSource
44907 The remote stub understands the @samp{QTDPsrc} packet that supplies
44908 the source form of tracepoint definitions.
44911 The remote stub understands the @samp{QAgent} packet.
44914 The remote stub understands the @samp{QAllow} packet.
44916 @item QDisableRandomization
44917 The remote stub understands the @samp{QDisableRandomization} packet.
44919 @item StaticTracepoint
44920 @cindex static tracepoints, in remote protocol
44921 The remote stub supports static tracepoints.
44923 @item InstallInTrace
44924 @anchor{install tracepoint in tracing}
44925 The remote stub supports installing tracepoint in tracing.
44927 @item EnableDisableTracepoints
44928 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
44929 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
44930 to be enabled and disabled while a trace experiment is running.
44932 @item QTBuffer:size
44933 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
44934 packet that allows to change the size of the trace buffer.
44937 @cindex string tracing, in remote protocol
44938 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
44939 See @ref{Bytecode Descriptions} for details about the bytecode.
44941 @item BreakpointCommands
44942 @cindex breakpoint commands, in remote protocol
44943 The remote stub supports running a breakpoint's command list itself,
44944 rather than reporting the hit to @value{GDBN}.
44947 The remote stub understands the @samp{Qbtrace:off} packet.
44950 The remote stub understands the @samp{Qbtrace:bts} packet.
44953 The remote stub understands the @samp{Qbtrace:pt} packet.
44955 @item Qbtrace-conf:bts:size
44956 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
44958 @item Qbtrace-conf:pt:size
44959 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
44962 The remote stub reports the @samp{swbreak} stop reason for memory
44966 The remote stub reports the @samp{hwbreak} stop reason for hardware
44970 The remote stub reports the @samp{fork} stop reason for fork events.
44973 The remote stub reports the @samp{vfork} stop reason for vfork events
44974 and vforkdone events.
44977 The remote stub reports the @samp{exec} stop reason for exec events.
44979 @item vContSupported
44980 The remote stub reports the supported actions in the reply to
44981 @samp{vCont?} packet.
44983 @item QThreadEvents
44984 The remote stub understands the @samp{QThreadEvents} packet.
44986 @item QThreadOptions=@var{supported_options}
44987 The remote stub understands the @samp{QThreadOptions} packet.
44988 @var{supported_options} indicates the set of thread options the remote
44989 stub supports. @var{supported_options} has the same format as the
44990 @var{options} parameter of the @code{QThreadOptions} packet, described
44991 at @ref{QThreadOptions}.
44994 The remote stub reports the @samp{N} stop reply.
44997 @item memory-tagging
44998 The remote stub supports and implements the required memory tagging
44999 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
45000 @samp{QMemTags} (@pxref{QMemTags}) packets.
45002 For AArch64 GNU/Linux systems, this feature also requires access to the
45003 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
45004 This is done via the @samp{vFile} requests.
45009 @cindex symbol lookup, remote request
45010 @cindex @samp{qSymbol} packet
45011 Notify the target that @value{GDBN} is prepared to serve symbol lookup
45012 requests. Accept requests from the target for the values of symbols.
45017 The target does not need to look up any (more) symbols.
45018 @item qSymbol:@var{sym_name}
45019 The target requests the value of symbol @var{sym_name} (hex encoded).
45020 @value{GDBN} may provide the value by using the
45021 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
45025 @item qSymbol:@var{sym_value}:@var{sym_name}
45026 Set the value of @var{sym_name} to @var{sym_value}.
45028 @var{sym_name} (hex encoded) is the name of a symbol whose value the
45029 target has previously requested.
45031 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
45032 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
45038 The target does not need to look up any (more) symbols.
45039 @item qSymbol:@var{sym_name}
45040 The target requests the value of a new symbol @var{sym_name} (hex
45041 encoded). @value{GDBN} will continue to supply the values of symbols
45042 (if available), until the target ceases to request them.
45047 @itemx QTDisconnected
45054 @itemx qTMinFTPILen
45056 @xref{Tracepoint Packets}.
45058 @anchor{qThreadExtraInfo}
45059 @item qThreadExtraInfo,@var{thread-id}
45060 @cindex thread attributes info, remote request
45061 @cindex @samp{qThreadExtraInfo} packet
45062 Obtain from the target OS a printable string description of thread
45063 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
45064 for the forms of @var{thread-id}. This
45065 string may contain anything that the target OS thinks is interesting
45066 for @value{GDBN} to tell the user about the thread. The string is
45067 displayed in @value{GDBN}'s @code{info threads} display. Some
45068 examples of possible thread extra info strings are @samp{Runnable}, or
45069 @samp{Blocked on Mutex}.
45073 @item @var{XX}@dots{}
45074 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
45075 comprising the printable string containing the extra information about
45076 the thread's attributes.
45079 (Note that the @code{qThreadExtraInfo} packet's name is separated from
45080 the command by a @samp{,}, not a @samp{:}, contrary to the naming
45081 conventions above. Please don't use this packet as a model for new
45100 @xref{Tracepoint Packets}.
45102 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
45103 @cindex read special object, remote request
45104 @cindex @samp{qXfer} packet
45105 @anchor{qXfer read}
45106 Read uninterpreted bytes from the target's special data area
45107 identified by the keyword @var{object}. Request @var{length} bytes
45108 starting at @var{offset} bytes into the data. The content and
45109 encoding of @var{annex} is specific to @var{object}; it can supply
45110 additional details about what data to access.
45115 Data @var{data} (@pxref{Binary Data}) has been read from the
45116 target. There may be more data at a higher address (although
45117 it is permitted to return @samp{m} even for the last valid
45118 block of data, as long as at least one byte of data was read).
45119 It is possible for @var{data} to have fewer bytes than the @var{length} in the
45123 Data @var{data} (@pxref{Binary Data}) has been read from the target.
45124 There is no more data to be read. It is possible for @var{data} to
45125 have fewer bytes than the @var{length} in the request.
45128 The @var{offset} in the request is at the end of the data.
45129 There is no more data to be read.
45132 The request was malformed, or @var{annex} was invalid.
45135 The offset was invalid, or there was an error encountered reading the data.
45136 The @var{nn} part is a hex-encoded @code{errno} value.
45139 An empty reply indicates the @var{object} string was not recognized by
45140 the stub, or that the object does not support reading.
45143 Here are the specific requests of this form defined so far. All the
45144 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
45145 formats, listed above.
45148 @item qXfer:auxv:read::@var{offset},@var{length}
45149 @anchor{qXfer auxiliary vector read}
45150 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
45151 auxiliary vector}. Note @var{annex} must be empty.
45153 This packet is not probed by default; the remote stub must request it,
45154 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45156 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
45157 @anchor{qXfer btrace read}
45159 Return a description of the current branch trace.
45160 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
45161 packet may have one of the following values:
45165 Returns all available branch trace.
45168 Returns all available branch trace if the branch trace changed since
45169 the last read request.
45172 Returns the new branch trace since the last read request. Adds a new
45173 block to the end of the trace that begins at zero and ends at the source
45174 location of the first branch in the trace buffer. This extra block is
45175 used to stitch traces together.
45177 If the trace buffer overflowed, returns an error indicating the overflow.
45180 This packet is not probed by default; the remote stub must request it
45181 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45183 @item qXfer:btrace-conf:read::@var{offset},@var{length}
45184 @anchor{qXfer btrace-conf read}
45186 Return a description of the current branch trace configuration.
45187 @xref{Branch Trace Configuration Format}.
45189 This packet is not probed by default; the remote stub must request it
45190 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45192 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
45193 @anchor{qXfer executable filename read}
45194 Return the full absolute name of the file that was executed to create
45195 a process running on the remote system. The annex specifies the
45196 numeric process ID of the process to query, encoded as a hexadecimal
45197 number. If the annex part is empty the remote stub should return the
45198 filename corresponding to the currently executing process.
45200 This packet is not probed by default; the remote stub must request it,
45201 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45203 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
45204 @anchor{qXfer target description read}
45205 Access the @dfn{target description}. @xref{Target Descriptions}. The
45206 annex specifies which XML document to access. The main description is
45207 always loaded from the @samp{target.xml} annex.
45209 This packet is not probed by default; the remote stub must request it,
45210 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45212 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
45213 @anchor{qXfer library list read}
45214 Access the target's list of loaded libraries. @xref{Library List Format}.
45215 The annex part of the generic @samp{qXfer} packet must be empty
45216 (@pxref{qXfer read}).
45218 Targets which maintain a list of libraries in the program's memory do
45219 not need to implement this packet; it is designed for platforms where
45220 the operating system manages the list of loaded libraries.
45222 This packet is not probed by default; the remote stub must request it,
45223 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45225 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
45226 @anchor{qXfer svr4 library list read}
45227 Access the target's list of loaded libraries when the target is an SVR4
45228 platform. @xref{Library List Format for SVR4 Targets}. The annex part
45229 of the generic @samp{qXfer} packet must be empty unless the remote
45230 stub indicated it supports the augmented form of this packet
45231 by supplying an appropriate @samp{qSupported} response
45232 (@pxref{qXfer read}, @ref{qSupported}).
45234 This packet is optional for better performance on SVR4 targets.
45235 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
45237 This packet is not probed by default; the remote stub must request it,
45238 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45240 If the remote stub indicates it supports the augmented form of this
45241 packet then the annex part of the generic @samp{qXfer} packet may
45242 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
45243 arguments. The currently supported arguments are:
45246 @item start=@var{address}
45247 A hexadecimal number specifying the address of the @samp{struct
45248 link_map} to start reading the library list from. If unset or zero
45249 then the first @samp{struct link_map} in the library list will be
45250 chosen as the starting point.
45252 @item prev=@var{address}
45253 A hexadecimal number specifying the address of the @samp{struct
45254 link_map} immediately preceding the @samp{struct link_map}
45255 specified by the @samp{start} argument. If unset or zero then
45256 the remote stub will expect that no @samp{struct link_map}
45257 exists prior to the starting point.
45259 @item lmid=@var{lmid}
45260 A hexadecimal number specifying a namespace identifier. This is
45261 currently only used together with @samp{start} to provide the
45262 namespace identifier back to @value{GDBN} in the response.
45263 @value{GDBN} will only provide values that were previously reported to
45264 it. If unset, the response will include @samp{lmid="0x0"}.
45267 Arguments that are not understood by the remote stub will be silently
45270 @item qXfer:memory-map:read::@var{offset},@var{length}
45271 @anchor{qXfer memory map read}
45272 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
45273 annex part of the generic @samp{qXfer} packet must be empty
45274 (@pxref{qXfer read}).
45276 This packet is not probed by default; the remote stub must request it,
45277 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45279 @item qXfer:sdata:read::@var{offset},@var{length}
45280 @anchor{qXfer sdata read}
45282 Read contents of the extra collected static tracepoint marker
45283 information. The annex part of the generic @samp{qXfer} packet must
45284 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
45287 This packet is not probed by default; the remote stub must request it,
45288 by supplying an appropriate @samp{qSupported} response
45289 (@pxref{qSupported}).
45291 @item qXfer:siginfo:read::@var{offset},@var{length}
45292 @anchor{qXfer siginfo read}
45293 Read contents of the extra signal information on the target
45294 system. The annex part of the generic @samp{qXfer} packet must be
45295 empty (@pxref{qXfer read}).
45297 This packet is not probed by default; the remote stub must request it,
45298 by supplying an appropriate @samp{qSupported} response
45299 (@pxref{qSupported}).
45301 @item qXfer:threads:read::@var{offset},@var{length}
45302 @anchor{qXfer threads read}
45303 Access the list of threads on target. @xref{Thread List Format}. The
45304 annex part of the generic @samp{qXfer} packet must be empty
45305 (@pxref{qXfer read}).
45307 This packet is not probed by default; the remote stub must request it,
45308 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45310 @item qXfer:traceframe-info:read::@var{offset},@var{length}
45311 @anchor{qXfer traceframe info read}
45313 Return a description of the current traceframe's contents.
45314 @xref{Traceframe Info Format}. The annex part of the generic
45315 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
45317 This packet is not probed by default; the remote stub must request it,
45318 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45320 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
45321 @anchor{qXfer unwind info block}
45323 Return the unwind information block for @var{pc}. This packet is used
45324 on OpenVMS/ia64 to ask the kernel unwind information.
45326 This packet is not probed by default.
45328 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
45329 @anchor{qXfer fdpic loadmap read}
45330 Read contents of @code{loadmap}s on the target system. The
45331 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
45332 executable @code{loadmap} or interpreter @code{loadmap} to read.
45334 This packet is not probed by default; the remote stub must request it,
45335 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
45337 @item qXfer:osdata:read::@var{offset},@var{length}
45338 @anchor{qXfer osdata read}
45339 Access the target's @dfn{operating system information}.
45340 @xref{Operating System Information}.
45344 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
45345 @cindex write data into object, remote request
45346 @anchor{qXfer write}
45347 Write uninterpreted bytes into the target's special data area
45348 identified by the keyword @var{object}, starting at @var{offset} bytes
45349 into the data. The binary-encoded data (@pxref{Binary Data}) to be
45350 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
45351 is specific to @var{object}; it can supply additional details about what data
45357 @var{nn} (hex encoded) is the number of bytes written.
45358 This may be fewer bytes than supplied in the request.
45361 The request was malformed, or @var{annex} was invalid.
45364 The offset was invalid, or there was an error encountered writing the data.
45365 The @var{nn} part is a hex-encoded @code{errno} value.
45368 An empty reply indicates the @var{object} string was not
45369 recognized by the stub, or that the object does not support writing.
45372 Here are the specific requests of this form defined so far. All the
45373 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
45374 formats, listed above.
45377 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
45378 @anchor{qXfer siginfo write}
45379 Write @var{data} to the extra signal information on the target system.
45380 The annex part of the generic @samp{qXfer} packet must be
45381 empty (@pxref{qXfer write}).
45383 This packet is not probed by default; the remote stub must request it,
45384 by supplying an appropriate @samp{qSupported} response
45385 (@pxref{qSupported}).
45388 @item qXfer:@var{object}:@var{operation}:@dots{}
45389 Requests of this form may be added in the future. When a stub does
45390 not recognize the @var{object} keyword, or its support for
45391 @var{object} does not recognize the @var{operation} keyword, the stub
45392 must respond with an empty packet.
45394 @item qAttached:@var{pid}
45395 @cindex query attached, remote request
45396 @cindex @samp{qAttached} packet
45397 Return an indication of whether the remote server attached to an
45398 existing process or created a new process. When the multiprocess
45399 protocol extensions are supported (@pxref{multiprocess extensions}),
45400 @var{pid} is an integer in hexadecimal format identifying the target
45401 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
45402 the query packet will be simplified as @samp{qAttached}.
45404 This query is used, for example, to know whether the remote process
45405 should be detached or killed when a @value{GDBN} session is ended with
45406 the @code{quit} command.
45411 The remote server attached to an existing process.
45413 The remote server created a new process.
45415 A badly formed request or an error was encountered.
45419 Enable branch tracing for the current thread using Branch Trace Store.
45424 Branch tracing has been enabled.
45426 A badly formed request or an error was encountered.
45430 Enable branch tracing for the current thread using Intel Processor Trace.
45435 Branch tracing has been enabled.
45437 A badly formed request or an error was encountered.
45441 Disable branch tracing for the current thread.
45446 Branch tracing has been disabled.
45448 A badly formed request or an error was encountered.
45451 @item Qbtrace-conf:bts:size=@var{value}
45452 Set the requested ring buffer size for new threads that use the
45453 btrace recording method in bts format.
45458 The ring buffer size has been set.
45460 A badly formed request or an error was encountered.
45463 @item Qbtrace-conf:pt:size=@var{value}
45464 Set the requested ring buffer size for new threads that use the
45465 btrace recording method in pt format.
45470 The ring buffer size has been set.
45472 A badly formed request or an error was encountered.
45477 @node Architecture-Specific Protocol Details
45478 @section Architecture-Specific Protocol Details
45480 This section describes how the remote protocol is applied to specific
45481 target architectures. Also see @ref{Standard Target Features}, for
45482 details of XML target descriptions for each architecture.
45485 * ARM-Specific Protocol Details::
45486 * MIPS-Specific Protocol Details::
45489 @node ARM-Specific Protocol Details
45490 @subsection @acronym{ARM}-specific Protocol Details
45493 * ARM Breakpoint Kinds::
45494 * ARM Memory Tag Types::
45497 @node ARM Breakpoint Kinds
45498 @subsubsection @acronym{ARM} Breakpoint Kinds
45499 @cindex breakpoint kinds, @acronym{ARM}
45501 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
45506 16-bit Thumb mode breakpoint.
45509 32-bit Thumb mode (Thumb-2) breakpoint.
45512 32-bit @acronym{ARM} mode breakpoint.
45516 @node ARM Memory Tag Types
45517 @subsubsection @acronym{ARM} Memory Tag Types
45518 @cindex memory tag types, @acronym{ARM}
45520 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
45533 @node MIPS-Specific Protocol Details
45534 @subsection @acronym{MIPS}-specific Protocol Details
45537 * MIPS Register packet Format::
45538 * MIPS Breakpoint Kinds::
45541 @node MIPS Register packet Format
45542 @subsubsection @acronym{MIPS} Register Packet Format
45543 @cindex register packet format, @acronym{MIPS}
45545 The following @code{g}/@code{G} packets have previously been defined.
45546 In the below, some thirty-two bit registers are transferred as
45547 sixty-four bits. Those registers should be zero/sign extended (which?)
45548 to fill the space allocated. Register bytes are transferred in target
45549 byte order. The two nibbles within a register byte are transferred
45550 most-significant -- least-significant.
45555 All registers are transferred as thirty-two bit quantities in the order:
45556 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
45557 registers; fsr; fir; fp.
45560 All registers are transferred as sixty-four bit quantities (including
45561 thirty-two bit registers such as @code{sr}). The ordering is the same
45566 @node MIPS Breakpoint Kinds
45567 @subsubsection @acronym{MIPS} Breakpoint Kinds
45568 @cindex breakpoint kinds, @acronym{MIPS}
45570 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
45575 16-bit @acronym{MIPS16} mode breakpoint.
45578 16-bit @acronym{microMIPS} mode breakpoint.
45581 32-bit standard @acronym{MIPS} mode breakpoint.
45584 32-bit @acronym{microMIPS} mode breakpoint.
45588 @node Tracepoint Packets
45589 @section Tracepoint Packets
45590 @cindex tracepoint packets
45591 @cindex packets, tracepoint
45593 Here we describe the packets @value{GDBN} uses to implement
45594 tracepoints (@pxref{Tracepoints}).
45598 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
45599 @cindex @samp{QTDP} packet
45600 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
45601 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
45602 the tracepoint is disabled. The @var{step} gives the tracepoint's step
45603 count, and @var{pass} gives its pass count. If an @samp{F} is present,
45604 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
45605 the number of bytes that the target should copy elsewhere to make room
45606 for the tracepoint. If an @samp{X} is present, it introduces a
45607 tracepoint condition, which consists of a hexadecimal length, followed
45608 by a comma and hex-encoded bytes, in a manner similar to action
45609 encodings as described below. If the trailing @samp{-} is present,
45610 further @samp{QTDP} packets will follow to specify this tracepoint's
45616 The packet was understood and carried out.
45618 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
45620 The packet was not recognized.
45623 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
45624 Define actions to be taken when a tracepoint is hit. The @var{n} and
45625 @var{addr} must be the same as in the initial @samp{QTDP} packet for
45626 this tracepoint. This packet may only be sent immediately after
45627 another @samp{QTDP} packet that ended with a @samp{-}. If the
45628 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
45629 specifying more actions for this tracepoint.
45631 In the series of action packets for a given tracepoint, at most one
45632 can have an @samp{S} before its first @var{action}. If such a packet
45633 is sent, it and the following packets define ``while-stepping''
45634 actions. Any prior packets define ordinary actions --- that is, those
45635 taken when the tracepoint is first hit. If no action packet has an
45636 @samp{S}, then all the packets in the series specify ordinary
45637 tracepoint actions.
45639 The @samp{@var{action}@dots{}} portion of the packet is a series of
45640 actions, concatenated without separators. Each action has one of the
45646 Collect the registers whose bits are set in @var{mask},
45647 a hexadecimal number whose @var{i}'th bit is set if register number
45648 @var{i} should be collected. (The least significant bit is numbered
45649 zero.) Note that @var{mask} may be any number of digits long; it may
45650 not fit in a 32-bit word.
45652 @item M @var{basereg},@var{offset},@var{len}
45653 Collect @var{len} bytes of memory starting at the address in register
45654 number @var{basereg}, plus @var{offset}. If @var{basereg} is
45655 @samp{-1}, then the range has a fixed address: @var{offset} is the
45656 address of the lowest byte to collect. The @var{basereg},
45657 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
45658 values (the @samp{-1} value for @var{basereg} is a special case).
45660 @item X @var{len},@var{expr}
45661 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
45662 it directs. The agent expression @var{expr} is as described in
45663 @ref{Agent Expressions}. Each byte of the expression is encoded as a
45664 two-digit hex number in the packet; @var{len} is the number of bytes
45665 in the expression (and thus one-half the number of hex digits in the
45670 Any number of actions may be packed together in a single @samp{QTDP}
45671 packet, as long as the packet does not exceed the maximum packet
45672 length (400 bytes, for many stubs). There may be only one @samp{R}
45673 action per tracepoint, and it must precede any @samp{M} or @samp{X}
45674 actions. Any registers referred to by @samp{M} and @samp{X} actions
45675 must be collected by a preceding @samp{R} action. (The
45676 ``while-stepping'' actions are treated as if they were attached to a
45677 separate tracepoint, as far as these restrictions are concerned.)
45682 The packet was understood and carried out.
45684 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
45686 The packet was not recognized.
45689 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
45690 @cindex @samp{QTDPsrc} packet
45691 Specify a source string of tracepoint @var{n} at address @var{addr}.
45692 This is useful to get accurate reproduction of the tracepoints
45693 originally downloaded at the beginning of the trace run. The @var{type}
45694 is the name of the tracepoint part, such as @samp{cond} for the
45695 tracepoint's conditional expression (see below for a list of types), while
45696 @var{bytes} is the string, encoded in hexadecimal.
45698 @var{start} is the offset of the @var{bytes} within the overall source
45699 string, while @var{slen} is the total length of the source string.
45700 This is intended for handling source strings that are longer than will
45701 fit in a single packet.
45702 @c Add detailed example when this info is moved into a dedicated
45703 @c tracepoint descriptions section.
45705 The available string types are @samp{at} for the location,
45706 @samp{cond} for the conditional, and @samp{cmd} for an action command.
45707 @value{GDBN} sends a separate packet for each command in the action
45708 list, in the same order in which the commands are stored in the list.
45710 The target does not need to do anything with source strings except
45711 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
45714 Although this packet is optional, and @value{GDBN} will only send it
45715 if the target replies with @samp{TracepointSource} @xref{General
45716 Query Packets}, it makes both disconnected tracing and trace files
45717 much easier to use. Otherwise the user must be careful that the
45718 tracepoints in effect while looking at trace frames are identical to
45719 the ones in effect during the trace run; even a small discrepancy
45720 could cause @samp{tdump} not to work, or a particular trace frame not
45723 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
45724 @cindex define trace state variable, remote request
45725 @cindex @samp{QTDV} packet
45726 Create a new trace state variable, number @var{n}, with an initial
45727 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
45728 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
45729 the option of not using this packet for initial values of zero; the
45730 target should simply create the trace state variables as they are
45731 mentioned in expressions. The value @var{builtin} should be 1 (one)
45732 if the trace state variable is builtin and 0 (zero) if it is not builtin.
45733 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
45734 @samp{qTsV} packet had it set. The contents of @var{name} is the
45735 hex-encoded name (without the leading @samp{$}) of the trace state
45738 @item QTFrame:@var{n}
45739 @cindex @samp{QTFrame} packet
45740 Select the @var{n}'th tracepoint frame from the buffer, and use the
45741 register and memory contents recorded there to answer subsequent
45742 request packets from @value{GDBN}.
45744 A successful reply from the stub indicates that the stub has found the
45745 requested frame. The response is a series of parts, concatenated
45746 without separators, describing the frame we selected. Each part has
45747 one of the following forms:
45751 The selected frame is number @var{n} in the trace frame buffer;
45752 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
45753 was no frame matching the criteria in the request packet.
45756 The selected trace frame records a hit of tracepoint number @var{t};
45757 @var{t} is a hexadecimal number.
45761 @item QTFrame:pc:@var{addr}
45762 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
45763 currently selected frame whose PC is @var{addr};
45764 @var{addr} is a hexadecimal number.
45766 @item QTFrame:tdp:@var{t}
45767 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
45768 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
45769 is a hexadecimal number.
45771 @item QTFrame:range:@var{start}:@var{end}
45772 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
45773 currently selected frame whose PC is between @var{start} (inclusive)
45774 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
45777 @item QTFrame:outside:@var{start}:@var{end}
45778 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
45779 frame @emph{outside} the given range of addresses (exclusive).
45782 @cindex @samp{qTMinFTPILen} packet
45783 This packet requests the minimum length of instruction at which a fast
45784 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
45785 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
45786 it depends on the target system being able to create trampolines in
45787 the first 64K of memory, which might or might not be possible for that
45788 system. So the reply to this packet will be 4 if it is able to
45795 The minimum instruction length is currently unknown.
45797 The minimum instruction length is @var{length}, where @var{length}
45798 is a hexadecimal number greater or equal to 1. A reply
45799 of 1 means that a fast tracepoint may be placed on any instruction
45800 regardless of size.
45802 An error has occurred.
45804 An empty reply indicates that the request is not supported by the stub.
45808 @cindex @samp{QTStart} packet
45809 Begin the tracepoint experiment. Begin collecting data from
45810 tracepoint hits in the trace frame buffer. This packet supports the
45811 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
45812 instruction reply packet}).
45815 @cindex @samp{QTStop} packet
45816 End the tracepoint experiment. Stop collecting trace frames.
45818 @item QTEnable:@var{n}:@var{addr}
45820 @cindex @samp{QTEnable} packet
45821 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
45822 experiment. If the tracepoint was previously disabled, then collection
45823 of data from it will resume.
45825 @item QTDisable:@var{n}:@var{addr}
45827 @cindex @samp{QTDisable} packet
45828 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
45829 experiment. No more data will be collected from the tracepoint unless
45830 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
45833 @cindex @samp{QTinit} packet
45834 Clear the table of tracepoints, and empty the trace frame buffer.
45836 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
45837 @cindex @samp{QTro} packet
45838 Establish the given ranges of memory as ``transparent''. The stub
45839 will answer requests for these ranges from memory's current contents,
45840 if they were not collected as part of the tracepoint hit.
45842 @value{GDBN} uses this to mark read-only regions of memory, like those
45843 containing program code. Since these areas never change, they should
45844 still have the same contents they did when the tracepoint was hit, so
45845 there's no reason for the stub to refuse to provide their contents.
45847 @item QTDisconnected:@var{value}
45848 @cindex @samp{QTDisconnected} packet
45849 Set the choice to what to do with the tracing run when @value{GDBN}
45850 disconnects from the target. A @var{value} of 1 directs the target to
45851 continue the tracing run, while 0 tells the target to stop tracing if
45852 @value{GDBN} is no longer in the picture.
45855 @cindex @samp{qTStatus} packet
45856 Ask the stub if there is a trace experiment running right now.
45858 The reply has the form:
45862 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
45863 @var{running} is a single digit @code{1} if the trace is presently
45864 running, or @code{0} if not. It is followed by semicolon-separated
45865 optional fields that an agent may use to report additional status.
45869 If the trace is not running, the agent may report any of several
45870 explanations as one of the optional fields:
45875 No trace has been run yet.
45877 @item tstop[:@var{text}]:0
45878 The trace was stopped by a user-originated stop command. The optional
45879 @var{text} field is a user-supplied string supplied as part of the
45880 stop command (for instance, an explanation of why the trace was
45881 stopped manually). It is hex-encoded.
45884 The trace stopped because the trace buffer filled up.
45886 @item tdisconnected:0
45887 The trace stopped because @value{GDBN} disconnected from the target.
45889 @item tpasscount:@var{tpnum}
45890 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
45892 @item terror:@var{text}:@var{tpnum}
45893 The trace stopped because tracepoint @var{tpnum} had an error. The
45894 string @var{text} is available to describe the nature of the error
45895 (for instance, a divide by zero in the condition expression); it
45899 The trace stopped for some other reason.
45903 Additional optional fields supply statistical and other information.
45904 Although not required, they are extremely useful for users monitoring
45905 the progress of a trace run. If a trace has stopped, and these
45906 numbers are reported, they must reflect the state of the just-stopped
45911 @item tframes:@var{n}
45912 The number of trace frames in the buffer.
45914 @item tcreated:@var{n}
45915 The total number of trace frames created during the run. This may
45916 be larger than the trace frame count, if the buffer is circular.
45918 @item tsize:@var{n}
45919 The total size of the trace buffer, in bytes.
45921 @item tfree:@var{n}
45922 The number of bytes still unused in the buffer.
45924 @item circular:@var{n}
45925 The value of the circular trace buffer flag. @code{1} means that the
45926 trace buffer is circular and old trace frames will be discarded if
45927 necessary to make room, @code{0} means that the trace buffer is linear
45930 @item disconn:@var{n}
45931 The value of the disconnected tracing flag. @code{1} means that
45932 tracing will continue after @value{GDBN} disconnects, @code{0} means
45933 that the trace run will stop.
45937 @item qTP:@var{tp}:@var{addr}
45938 @cindex tracepoint status, remote request
45939 @cindex @samp{qTP} packet
45940 Ask the stub for the current state of tracepoint number @var{tp} at
45941 address @var{addr}.
45945 @item V@var{hits}:@var{usage}
45946 The tracepoint has been hit @var{hits} times so far during the trace
45947 run, and accounts for @var{usage} in the trace buffer. Note that
45948 @code{while-stepping} steps are not counted as separate hits, but the
45949 steps' space consumption is added into the usage number.
45953 @item qTV:@var{var}
45954 @cindex trace state variable value, remote request
45955 @cindex @samp{qTV} packet
45956 Ask the stub for the value of the trace state variable number @var{var}.
45961 The value of the variable is @var{value}. This will be the current
45962 value of the variable if the user is examining a running target, or a
45963 saved value if the variable was collected in the trace frame that the
45964 user is looking at. Note that multiple requests may result in
45965 different reply values, such as when requesting values while the
45966 program is running.
45969 The value of the variable is unknown. This would occur, for example,
45970 if the user is examining a trace frame in which the requested variable
45975 @cindex @samp{qTfP} packet
45977 @cindex @samp{qTsP} packet
45978 These packets request data about tracepoints that are being used by
45979 the target. @value{GDBN} sends @code{qTfP} to get the first piece
45980 of data, and multiple @code{qTsP} to get additional pieces. Replies
45981 to these packets generally take the form of the @code{QTDP} packets
45982 that define tracepoints. (FIXME add detailed syntax)
45985 @cindex @samp{qTfV} packet
45987 @cindex @samp{qTsV} packet
45988 These packets request data about trace state variables that are on the
45989 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
45990 and multiple @code{qTsV} to get additional variables. Replies to
45991 these packets follow the syntax of the @code{QTDV} packets that define
45992 trace state variables.
45998 @cindex @samp{qTfSTM} packet
45999 @cindex @samp{qTsSTM} packet
46000 These packets request data about static tracepoint markers that exist
46001 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
46002 first piece of data, and multiple @code{qTsSTM} to get additional
46003 pieces. Replies to these packets take the following form:
46007 @item m @var{address}:@var{id}:@var{extra}
46009 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
46010 a comma-separated list of markers
46012 (lower case letter @samp{L}) denotes end of list.
46014 An error occurred. The error number @var{nn} is given as hex digits.
46016 An empty reply indicates that the request is not supported by the
46020 The @var{address} is encoded in hex;
46021 @var{id} and @var{extra} are strings encoded in hex.
46023 In response to each query, the target will reply with a list of one or
46024 more markers, separated by commas. @value{GDBN} will respond to each
46025 reply with a request for more markers (using the @samp{qs} form of the
46026 query), until the target responds with @samp{l} (lower-case ell, for
46029 @item qTSTMat:@var{address}
46031 @cindex @samp{qTSTMat} packet
46032 This packets requests data about static tracepoint markers in the
46033 target program at @var{address}. Replies to this packet follow the
46034 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
46035 tracepoint markers.
46037 @item QTSave:@var{filename}
46038 @cindex @samp{QTSave} packet
46039 This packet directs the target to save trace data to the file name
46040 @var{filename} in the target's filesystem. The @var{filename} is encoded
46041 as a hex string; the interpretation of the file name (relative vs
46042 absolute, wild cards, etc) is up to the target.
46044 @item qTBuffer:@var{offset},@var{len}
46045 @cindex @samp{qTBuffer} packet
46046 Return up to @var{len} bytes of the current contents of trace buffer,
46047 starting at @var{offset}. The trace buffer is treated as if it were
46048 a contiguous collection of traceframes, as per the trace file format.
46049 The reply consists as many hex-encoded bytes as the target can deliver
46050 in a packet; it is not an error to return fewer than were asked for.
46051 A reply consisting of just @code{l} indicates that no bytes are
46054 @item QTBuffer:circular:@var{value}
46055 This packet directs the target to use a circular trace buffer if
46056 @var{value} is 1, or a linear buffer if the value is 0.
46058 @item QTBuffer:size:@var{size}
46059 @anchor{QTBuffer-size}
46060 @cindex @samp{QTBuffer size} packet
46061 This packet directs the target to make the trace buffer be of size
46062 @var{size} if possible. A value of @code{-1} tells the target to
46063 use whatever size it prefers.
46065 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
46066 @cindex @samp{QTNotes} packet
46067 This packet adds optional textual notes to the trace run. Allowable
46068 types include @code{user}, @code{notes}, and @code{tstop}, the
46069 @var{text} fields are arbitrary strings, hex-encoded.
46073 @subsection Relocate instruction reply packet
46074 When installing fast tracepoints in memory, the target may need to
46075 relocate the instruction currently at the tracepoint address to a
46076 different address in memory. For most instructions, a simple copy is
46077 enough, but, for example, call instructions that implicitly push the
46078 return address on the stack, and relative branches or other
46079 PC-relative instructions require offset adjustment, so that the effect
46080 of executing the instruction at a different address is the same as if
46081 it had executed in the original location.
46083 In response to several of the tracepoint packets, the target may also
46084 respond with a number of intermediate @samp{qRelocInsn} request
46085 packets before the final result packet, to have @value{GDBN} handle
46086 this relocation operation. If a packet supports this mechanism, its
46087 documentation will explicitly say so. See for example the above
46088 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
46089 format of the request is:
46092 @item qRelocInsn:@var{from};@var{to}
46094 This requests @value{GDBN} to copy instruction at address @var{from}
46095 to address @var{to}, possibly adjusted so that executing the
46096 instruction at @var{to} has the same effect as executing it at
46097 @var{from}. @value{GDBN} writes the adjusted instruction to target
46098 memory starting at @var{to}.
46103 @item qRelocInsn:@var{adjusted_size}
46104 Informs the stub the relocation is complete. The @var{adjusted_size} is
46105 the length in bytes of resulting relocated instruction sequence.
46107 A badly formed request was detected, or an error was encountered while
46108 relocating the instruction.
46111 @node Host I/O Packets
46112 @section Host I/O Packets
46113 @cindex Host I/O, remote protocol
46114 @cindex file transfer, remote protocol
46116 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
46117 operations on the far side of a remote link. For example, Host I/O is
46118 used to upload and download files to a remote target with its own
46119 filesystem. Host I/O uses the same constant values and data structure
46120 layout as the target-initiated File-I/O protocol. However, the
46121 Host I/O packets are structured differently. The target-initiated
46122 protocol relies on target memory to store parameters and buffers.
46123 Host I/O requests are initiated by @value{GDBN}, and the
46124 target's memory is not involved. @xref{File-I/O Remote Protocol
46125 Extension}, for more details on the target-initiated protocol.
46127 The Host I/O request packets all encode a single operation along with
46128 its arguments. They have this format:
46132 @item vFile:@var{operation}: @var{parameter}@dots{}
46133 @var{operation} is the name of the particular request; the target
46134 should compare the entire packet name up to the second colon when checking
46135 for a supported operation. The format of @var{parameter} depends on
46136 the operation. Numbers are always passed in hexadecimal. Negative
46137 numbers have an explicit minus sign (i.e.@: two's complement is not
46138 used). Strings (e.g.@: filenames) are encoded as a series of
46139 hexadecimal bytes. The last argument to a system call may be a
46140 buffer of escaped binary data (@pxref{Binary Data}).
46144 The valid responses to Host I/O packets are:
46148 @item F @var{result} [, @var{errno}] [; @var{attachment}]
46149 @var{result} is the integer value returned by this operation, usually
46150 non-negative for success and -1 for errors. If an error has occurred,
46151 @var{errno} will be included in the result specifying a
46152 value defined by the File-I/O protocol (@pxref{Errno Values}). For
46153 operations which return data, @var{attachment} supplies the data as a
46154 binary buffer. Binary buffers in response packets are escaped in the
46155 normal way (@pxref{Binary Data}). See the individual packet
46156 documentation for the interpretation of @var{result} and
46160 An empty response indicates that this operation is not recognized.
46164 These are the supported Host I/O operations:
46167 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
46168 Open a file at @var{filename} and return a file descriptor for it, or
46169 return -1 if an error occurs. The @var{filename} is a string,
46170 @var{flags} is an integer indicating a mask of open flags
46171 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
46172 of mode bits to use if the file is created (@pxref{mode_t Values}).
46173 @xref{open}, for details of the open flags and mode values.
46175 @item vFile:close: @var{fd}
46176 Close the open file corresponding to @var{fd} and return 0, or
46177 -1 if an error occurs.
46179 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
46180 Read data from the open file corresponding to @var{fd}. Up to
46181 @var{count} bytes will be read from the file, starting at @var{offset}
46182 relative to the start of the file. The target may read fewer bytes;
46183 common reasons include packet size limits and an end-of-file
46184 condition. The number of bytes read is returned. Zero should only be
46185 returned for a successful read at the end of the file, or if
46186 @var{count} was zero.
46188 The data read should be returned as a binary attachment on success.
46189 If zero bytes were read, the response should include an empty binary
46190 attachment (i.e.@: a trailing semicolon). The return value is the
46191 number of target bytes read; the binary attachment may be longer if
46192 some characters were escaped.
46194 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
46195 Write @var{data} (a binary buffer) to the open file corresponding
46196 to @var{fd}. Start the write at @var{offset} from the start of the
46197 file. Unlike many @code{write} system calls, there is no
46198 separate @var{count} argument; the length of @var{data} in the
46199 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
46200 which may be shorter than the length of @var{data}, or -1 if an
46203 @item vFile:fstat: @var{fd}
46204 Get information about the open file corresponding to @var{fd}.
46205 On success the information is returned as a binary attachment
46206 and the return value is the size of this attachment in bytes.
46207 If an error occurs the return value is -1. The format of the
46208 returned binary attachment is as described in @ref{struct stat}.
46210 @item vFile:unlink: @var{filename}
46211 Delete the file at @var{filename} on the target. Return 0,
46212 or -1 if an error occurs. The @var{filename} is a string.
46214 @item vFile:readlink: @var{filename}
46215 Read value of symbolic link @var{filename} on the target. Return
46216 the number of bytes read, or -1 if an error occurs.
46218 The data read should be returned as a binary attachment on success.
46219 If zero bytes were read, the response should include an empty binary
46220 attachment (i.e.@: a trailing semicolon). The return value is the
46221 number of target bytes read; the binary attachment may be longer if
46222 some characters were escaped.
46224 @item vFile:setfs: @var{pid}
46225 Select the filesystem on which @code{vFile} operations with
46226 @var{filename} arguments will operate. This is required for
46227 @value{GDBN} to be able to access files on remote targets where
46228 the remote stub does not share a common filesystem with the
46231 If @var{pid} is nonzero, select the filesystem as seen by process
46232 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
46233 the remote stub. Return 0 on success, or -1 if an error occurs.
46234 If @code{vFile:setfs:} indicates success, the selected filesystem
46235 remains selected until the next successful @code{vFile:setfs:}
46241 @section Interrupts
46242 @cindex interrupts (remote protocol)
46243 @anchor{interrupting remote targets}
46245 In all-stop mode, when a program on the remote target is running,
46246 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
46247 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
46248 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
46250 The precise meaning of @code{BREAK} is defined by the transport
46251 mechanism and may, in fact, be undefined. @value{GDBN} does not
46252 currently define a @code{BREAK} mechanism for any of the network
46253 interfaces except for TCP, in which case @value{GDBN} sends the
46254 @code{telnet} BREAK sequence.
46256 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
46257 transport mechanisms. It is represented by sending the single byte
46258 @code{0x03} without any of the usual packet overhead described in
46259 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
46260 transmitted as part of a packet, it is considered to be packet data
46261 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
46262 (@pxref{X packet}), used for binary downloads, may include an unescaped
46263 @code{0x03} as part of its packet.
46265 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
46266 When Linux kernel receives this sequence from serial port,
46267 it stops execution and connects to gdb.
46269 In non-stop mode, because packet resumptions are asynchronous
46270 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
46271 command to the remote stub, even when the target is running. For that
46272 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
46273 packet}) with the usual packet framing instead of the single byte
46276 Stubs are not required to recognize these interrupt mechanisms and the
46277 precise meaning associated with receipt of the interrupt is
46278 implementation defined. If the target supports debugging of multiple
46279 threads and/or processes, it should attempt to interrupt all
46280 currently-executing threads and processes.
46281 If the stub is successful at interrupting the
46282 running program, it should send one of the stop
46283 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
46284 of successfully stopping the program in all-stop mode, and a stop reply
46285 for each stopped thread in non-stop mode.
46286 Interrupts received while the
46287 program is stopped are queued and the program will be interrupted when
46288 it is resumed next time.
46290 @node Notification Packets
46291 @section Notification Packets
46292 @cindex notification packets
46293 @cindex packets, notification
46295 The @value{GDBN} remote serial protocol includes @dfn{notifications},
46296 packets that require no acknowledgment. Both the GDB and the stub
46297 may send notifications (although the only notifications defined at
46298 present are sent by the stub). Notifications carry information
46299 without incurring the round-trip latency of an acknowledgment, and so
46300 are useful for low-impact communications where occasional packet loss
46303 A notification packet has the form @samp{% @var{data} #
46304 @var{checksum}}, where @var{data} is the content of the notification,
46305 and @var{checksum} is a checksum of @var{data}, computed and formatted
46306 as for ordinary @value{GDBN} packets. A notification's @var{data}
46307 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
46308 receiving a notification, the recipient sends no @samp{+} or @samp{-}
46309 to acknowledge the notification's receipt or to report its corruption.
46311 Every notification's @var{data} begins with a name, which contains no
46312 colon characters, followed by a colon character.
46314 Recipients should silently ignore corrupted notifications and
46315 notifications they do not understand. Recipients should restart
46316 timeout periods on receipt of a well-formed notification, whether or
46317 not they understand it.
46319 Senders should only send the notifications described here when this
46320 protocol description specifies that they are permitted. In the
46321 future, we may extend the protocol to permit existing notifications in
46322 new contexts; this rule helps older senders avoid confusing newer
46325 (Older versions of @value{GDBN} ignore bytes received until they see
46326 the @samp{$} byte that begins an ordinary packet, so new stubs may
46327 transmit notifications without fear of confusing older clients. There
46328 are no notifications defined for @value{GDBN} to send at the moment, but we
46329 assume that most older stubs would ignore them, as well.)
46331 Each notification is comprised of three parts:
46333 @item @var{name}:@var{event}
46334 The notification packet is sent by the side that initiates the
46335 exchange (currently, only the stub does that), with @var{event}
46336 carrying the specific information about the notification, and
46337 @var{name} specifying the name of the notification.
46339 The acknowledge sent by the other side, usually @value{GDBN}, to
46340 acknowledge the exchange and request the event.
46343 The purpose of an asynchronous notification mechanism is to report to
46344 @value{GDBN} that something interesting happened in the remote stub.
46346 The remote stub may send notification @var{name}:@var{event}
46347 at any time, but @value{GDBN} acknowledges the notification when
46348 appropriate. The notification event is pending before @value{GDBN}
46349 acknowledges. Only one notification at a time may be pending; if
46350 additional events occur before @value{GDBN} has acknowledged the
46351 previous notification, they must be queued by the stub for later
46352 synchronous transmission in response to @var{ack} packets from
46353 @value{GDBN}. Because the notification mechanism is unreliable,
46354 the stub is permitted to resend a notification if it believes
46355 @value{GDBN} may not have received it.
46357 Specifically, notifications may appear when @value{GDBN} is not
46358 otherwise reading input from the stub, or when @value{GDBN} is
46359 expecting to read a normal synchronous response or a
46360 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
46361 Notification packets are distinct from any other communication from
46362 the stub so there is no ambiguity.
46364 After receiving a notification, @value{GDBN} shall acknowledge it by
46365 sending a @var{ack} packet as a regular, synchronous request to the
46366 stub. Such acknowledgment is not required to happen immediately, as
46367 @value{GDBN} is permitted to send other, unrelated packets to the
46368 stub first, which the stub should process normally.
46370 Upon receiving a @var{ack} packet, if the stub has other queued
46371 events to report to @value{GDBN}, it shall respond by sending a
46372 normal @var{event}. @value{GDBN} shall then send another @var{ack}
46373 packet to solicit further responses; again, it is permitted to send
46374 other, unrelated packets as well which the stub should process
46377 If the stub receives a @var{ack} packet and there are no additional
46378 @var{event} to report, the stub shall return an @samp{OK} response.
46379 At this point, @value{GDBN} has finished processing a notification
46380 and the stub has completed sending any queued events. @value{GDBN}
46381 won't accept any new notifications until the final @samp{OK} is
46382 received . If further notification events occur, the stub shall send
46383 a new notification, @value{GDBN} shall accept the notification, and
46384 the process shall be repeated.
46386 The process of asynchronous notification can be illustrated by the
46389 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
46392 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
46394 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
46399 The following notifications are defined:
46400 @multitable @columnfractions 0.12 0.12 0.38 0.38
46409 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
46410 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
46411 for information on how these notifications are acknowledged by
46413 @tab Report an asynchronous stop event in non-stop mode.
46417 @node Remote Non-Stop
46418 @section Remote Protocol Support for Non-Stop Mode
46420 @value{GDBN}'s remote protocol supports non-stop debugging of
46421 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
46422 supports non-stop mode, it should report that to @value{GDBN} by including
46423 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
46425 @value{GDBN} typically sends a @samp{QNonStop} packet only when
46426 establishing a new connection with the stub. Entering non-stop mode
46427 does not alter the state of any currently-running threads, but targets
46428 must stop all threads in any already-attached processes when entering
46429 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
46430 probe the target state after a mode change.
46432 In non-stop mode, when an attached process encounters an event that
46433 would otherwise be reported with a stop reply, it uses the
46434 asynchronous notification mechanism (@pxref{Notification Packets}) to
46435 inform @value{GDBN}. In contrast to all-stop mode, where all threads
46436 in all processes are stopped when a stop reply is sent, in non-stop
46437 mode only the thread reporting the stop event is stopped. That is,
46438 when reporting a @samp{S} or @samp{T} response to indicate completion
46439 of a step operation, hitting a breakpoint, or a fault, only the
46440 affected thread is stopped; any other still-running threads continue
46441 to run. When reporting a @samp{W} or @samp{X} response, all running
46442 threads belonging to other attached processes continue to run.
46444 In non-stop mode, the target shall respond to the @samp{?} packet as
46445 follows. First, any incomplete stop reply notification/@samp{vStopped}
46446 sequence in progress is abandoned. The target must begin a new
46447 sequence reporting stop events for all stopped threads, whether or not
46448 it has previously reported those events to @value{GDBN}. The first
46449 stop reply is sent as a synchronous reply to the @samp{?} packet, and
46450 subsequent stop replies are sent as responses to @samp{vStopped} packets
46451 using the mechanism described above. The target must not send
46452 asynchronous stop reply notifications until the sequence is complete.
46453 If all threads are running when the target receives the @samp{?} packet,
46454 or if the target is not attached to any process, it shall respond
46457 If the stub supports non-stop mode, it should also support the
46458 @samp{swbreak} stop reason if software breakpoints are supported, and
46459 the @samp{hwbreak} stop reason if hardware breakpoints are supported
46460 (@pxref{swbreak stop reason}). This is because given the asynchronous
46461 nature of non-stop mode, between the time a thread hits a breakpoint
46462 and the time the event is finally processed by @value{GDBN}, the
46463 breakpoint may have already been removed from the target. Due to
46464 this, @value{GDBN} needs to be able to tell whether a trap stop was
46465 caused by a delayed breakpoint event, which should be ignored, as
46466 opposed to a random trap signal, which should be reported to the user.
46467 Note the @samp{swbreak} feature implies that the target is responsible
46468 for adjusting the PC when a software breakpoint triggers, if
46469 necessary, such as on the x86 architecture.
46471 @node Packet Acknowledgment
46472 @section Packet Acknowledgment
46474 @cindex acknowledgment, for @value{GDBN} remote
46475 @cindex packet acknowledgment, for @value{GDBN} remote
46476 By default, when either the host or the target machine receives a packet,
46477 the first response expected is an acknowledgment: either @samp{+} (to indicate
46478 the package was received correctly) or @samp{-} (to request retransmission).
46479 This mechanism allows the @value{GDBN} remote protocol to operate over
46480 unreliable transport mechanisms, such as a serial line.
46482 In cases where the transport mechanism is itself reliable (such as a pipe or
46483 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
46484 It may be desirable to disable them in that case to reduce communication
46485 overhead, or for other reasons. This can be accomplished by means of the
46486 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
46488 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
46489 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
46490 and response format still includes the normal checksum, as described in
46491 @ref{Overview}, but the checksum may be ignored by the receiver.
46493 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
46494 no-acknowledgment mode, it should report that to @value{GDBN}
46495 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
46496 @pxref{qSupported}.
46497 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
46498 disabled via the @code{set remote noack-packet off} command
46499 (@pxref{Remote Configuration}),
46500 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
46501 Only then may the stub actually turn off packet acknowledgments.
46502 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
46503 response, which can be safely ignored by the stub.
46505 Note that @code{set remote noack-packet} command only affects negotiation
46506 between @value{GDBN} and the stub when subsequent connections are made;
46507 it does not affect the protocol acknowledgment state for any current
46509 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
46510 new connection is established,
46511 there is also no protocol request to re-enable the acknowledgments
46512 for the current connection, once disabled.
46517 Example sequence of a target being re-started. Notice how the restart
46518 does not get any direct output:
46523 @emph{target restarts}
46526 <- @code{T001:1234123412341234}
46530 Example sequence of a target being stepped by a single instruction:
46533 -> @code{G1445@dots{}}
46538 <- @code{T001:1234123412341234}
46542 <- @code{1455@dots{}}
46546 @node File-I/O Remote Protocol Extension
46547 @section File-I/O Remote Protocol Extension
46548 @cindex File-I/O remote protocol extension
46551 * File-I/O Overview::
46552 * Protocol Basics::
46553 * The F Request Packet::
46554 * The F Reply Packet::
46555 * The Ctrl-C Message::
46557 * List of Supported Calls::
46558 * Protocol-specific Representation of Datatypes::
46560 * File-I/O Examples::
46563 @node File-I/O Overview
46564 @subsection File-I/O Overview
46565 @cindex file-i/o overview
46567 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
46568 target to use the host's file system and console I/O to perform various
46569 system calls. System calls on the target system are translated into a
46570 remote protocol packet to the host system, which then performs the needed
46571 actions and returns a response packet to the target system.
46572 This simulates file system operations even on targets that lack file systems.
46574 The protocol is defined to be independent of both the host and target systems.
46575 It uses its own internal representation of datatypes and values. Both
46576 @value{GDBN} and the target's @value{GDBN} stub are responsible for
46577 translating the system-dependent value representations into the internal
46578 protocol representations when data is transmitted.
46580 The communication is synchronous. A system call is possible only when
46581 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
46582 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
46583 the target is stopped to allow deterministic access to the target's
46584 memory. Therefore File-I/O is not interruptible by target signals. On
46585 the other hand, it is possible to interrupt File-I/O by a user interrupt
46586 (@samp{Ctrl-C}) within @value{GDBN}.
46588 The target's request to perform a host system call does not finish
46589 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
46590 after finishing the system call, the target returns to continuing the
46591 previous activity (continue, step). No additional continue or step
46592 request from @value{GDBN} is required.
46595 (@value{GDBP}) continue
46596 <- target requests 'system call X'
46597 target is stopped, @value{GDBN} executes system call
46598 -> @value{GDBN} returns result
46599 ... target continues, @value{GDBN} returns to wait for the target
46600 <- target hits breakpoint and sends a Txx packet
46603 The protocol only supports I/O on the console and to regular files on
46604 the host file system. Character or block special devices, pipes,
46605 named pipes, sockets or any other communication method on the host
46606 system are not supported by this protocol.
46608 File I/O is not supported in non-stop mode.
46610 @node Protocol Basics
46611 @subsection Protocol Basics
46612 @cindex protocol basics, file-i/o
46614 The File-I/O protocol uses the @code{F} packet as the request as well
46615 as reply packet. Since a File-I/O system call can only occur when
46616 @value{GDBN} is waiting for a response from the continuing or stepping target,
46617 the File-I/O request is a reply that @value{GDBN} has to expect as a result
46618 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
46619 This @code{F} packet contains all information needed to allow @value{GDBN}
46620 to call the appropriate host system call:
46624 A unique identifier for the requested system call.
46627 All parameters to the system call. Pointers are given as addresses
46628 in the target memory address space. Pointers to strings are given as
46629 pointer/length pair. Numerical values are given as they are.
46630 Numerical control flags are given in a protocol-specific representation.
46634 At this point, @value{GDBN} has to perform the following actions.
46638 If the parameters include pointer values to data needed as input to a
46639 system call, @value{GDBN} requests this data from the target with a
46640 standard @code{m} packet request. This additional communication has to be
46641 expected by the target implementation and is handled as any other @code{m}
46645 @value{GDBN} translates all value from protocol representation to host
46646 representation as needed. Datatypes are coerced into the host types.
46649 @value{GDBN} calls the system call.
46652 It then coerces datatypes back to protocol representation.
46655 If the system call is expected to return data in buffer space specified
46656 by pointer parameters to the call, the data is transmitted to the
46657 target using a @code{M} or @code{X} packet. This packet has to be expected
46658 by the target implementation and is handled as any other @code{M} or @code{X}
46663 Eventually @value{GDBN} replies with another @code{F} packet which contains all
46664 necessary information for the target to continue. This at least contains
46671 @code{errno}, if has been changed by the system call.
46678 After having done the needed type and value coercion, the target continues
46679 the latest continue or step action.
46681 @node The F Request Packet
46682 @subsection The @code{F} Request Packet
46683 @cindex file-i/o request packet
46684 @cindex @code{F} request packet
46686 The @code{F} request packet has the following format:
46689 @item F@var{call-id},@var{parameter@dots{}}
46691 @var{call-id} is the identifier to indicate the host system call to be called.
46692 This is just the name of the function.
46694 @var{parameter@dots{}} are the parameters to the system call.
46695 Parameters are hexadecimal integer values, either the actual values in case
46696 of scalar datatypes, pointers to target buffer space in case of compound
46697 datatypes and unspecified memory areas, or pointer/length pairs in case
46698 of string parameters. These are appended to the @var{call-id} as a
46699 comma-delimited list. All values are transmitted in ASCII
46700 string representation, pointer/length pairs separated by a slash.
46706 @node The F Reply Packet
46707 @subsection The @code{F} Reply Packet
46708 @cindex file-i/o reply packet
46709 @cindex @code{F} reply packet
46711 The @code{F} reply packet has the following format:
46715 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
46717 @var{retcode} is the return code of the system call as hexadecimal value.
46719 @var{errno} is the @code{errno} set by the call, in protocol-specific
46721 This parameter can be omitted if the call was successful.
46723 @var{Ctrl-C flag} is only sent if the user requested a break. In this
46724 case, @var{errno} must be sent as well, even if the call was successful.
46725 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
46732 or, if the call was interrupted before the host call has been performed:
46739 assuming 4 is the protocol-specific representation of @code{EINTR}.
46744 @node The Ctrl-C Message
46745 @subsection The @samp{Ctrl-C} Message
46746 @cindex ctrl-c message, in file-i/o protocol
46748 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
46749 reply packet (@pxref{The F Reply Packet}),
46750 the target should behave as if it had
46751 gotten a break message. The meaning for the target is ``system call
46752 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
46753 (as with a break message) and return to @value{GDBN} with a @code{T02}
46756 It's important for the target to know in which
46757 state the system call was interrupted. There are two possible cases:
46761 The system call hasn't been performed on the host yet.
46764 The system call on the host has been finished.
46768 These two states can be distinguished by the target by the value of the
46769 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
46770 call hasn't been performed. This is equivalent to the @code{EINTR} handling
46771 on POSIX systems. In any other case, the target may presume that the
46772 system call has been finished --- successfully or not --- and should behave
46773 as if the break message arrived right after the system call.
46775 @value{GDBN} must behave reliably. If the system call has not been called
46776 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
46777 @code{errno} in the packet. If the system call on the host has been finished
46778 before the user requests a break, the full action must be finished by
46779 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
46780 The @code{F} packet may only be sent when either nothing has happened
46781 or the full action has been completed.
46784 @subsection Console I/O
46785 @cindex console i/o as part of file-i/o
46787 By default and if not explicitly closed by the target system, the file
46788 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
46789 on the @value{GDBN} console is handled as any other file output operation
46790 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
46791 by @value{GDBN} so that after the target read request from file descriptor
46792 0 all following typing is buffered until either one of the following
46797 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
46799 system call is treated as finished.
46802 The user presses @key{RET}. This is treated as end of input with a trailing
46806 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
46807 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
46811 If the user has typed more characters than fit in the buffer given to
46812 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
46813 either another @code{read(0, @dots{})} is requested by the target, or debugging
46814 is stopped at the user's request.
46817 @node List of Supported Calls
46818 @subsection List of Supported Calls
46819 @cindex list of supported file-i/o calls
46836 @unnumberedsubsubsec open
46837 @cindex open, file-i/o system call
46842 int open(const char *pathname, int flags);
46843 int open(const char *pathname, int flags, mode_t mode);
46847 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
46850 @var{flags} is the bitwise @code{OR} of the following values:
46854 If the file does not exist it will be created. The host
46855 rules apply as far as file ownership and time stamps
46859 When used with @code{O_CREAT}, if the file already exists it is
46860 an error and open() fails.
46863 If the file already exists and the open mode allows
46864 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
46865 truncated to zero length.
46868 The file is opened in append mode.
46871 The file is opened for reading only.
46874 The file is opened for writing only.
46877 The file is opened for reading and writing.
46881 Other bits are silently ignored.
46885 @var{mode} is the bitwise @code{OR} of the following values:
46889 User has read permission.
46892 User has write permission.
46895 Group has read permission.
46898 Group has write permission.
46901 Others have read permission.
46904 Others have write permission.
46908 Other bits are silently ignored.
46911 @item Return value:
46912 @code{open} returns the new file descriptor or -1 if an error
46919 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
46922 @var{pathname} refers to a directory.
46925 The requested access is not allowed.
46928 @var{pathname} was too long.
46931 A directory component in @var{pathname} does not exist.
46934 @var{pathname} refers to a device, pipe, named pipe or socket.
46937 @var{pathname} refers to a file on a read-only filesystem and
46938 write access was requested.
46941 @var{pathname} is an invalid pointer value.
46944 No space on device to create the file.
46947 The process already has the maximum number of files open.
46950 The limit on the total number of files open on the system
46954 The call was interrupted by the user.
46960 @unnumberedsubsubsec close
46961 @cindex close, file-i/o system call
46970 @samp{Fclose,@var{fd}}
46972 @item Return value:
46973 @code{close} returns zero on success, or -1 if an error occurred.
46979 @var{fd} isn't a valid open file descriptor.
46982 The call was interrupted by the user.
46988 @unnumberedsubsubsec read
46989 @cindex read, file-i/o system call
46994 int read(int fd, void *buf, unsigned int count);
46998 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
47000 @item Return value:
47001 On success, the number of bytes read is returned.
47002 Zero indicates end of file. If count is zero, read
47003 returns zero as well. On error, -1 is returned.
47009 @var{fd} is not a valid file descriptor or is not open for
47013 @var{bufptr} is an invalid pointer value.
47016 The call was interrupted by the user.
47022 @unnumberedsubsubsec write
47023 @cindex write, file-i/o system call
47028 int write(int fd, const void *buf, unsigned int count);
47032 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
47034 @item Return value:
47035 On success, the number of bytes written are returned.
47036 Zero indicates nothing was written. On error, -1
47043 @var{fd} is not a valid file descriptor or is not open for
47047 @var{bufptr} is an invalid pointer value.
47050 An attempt was made to write a file that exceeds the
47051 host-specific maximum file size allowed.
47054 No space on device to write the data.
47057 The call was interrupted by the user.
47063 @unnumberedsubsubsec lseek
47064 @cindex lseek, file-i/o system call
47069 long lseek (int fd, long offset, int flag);
47073 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
47075 @var{flag} is one of:
47079 The offset is set to @var{offset} bytes.
47082 The offset is set to its current location plus @var{offset}
47086 The offset is set to the size of the file plus @var{offset}
47090 @item Return value:
47091 On success, the resulting unsigned offset in bytes from
47092 the beginning of the file is returned. Otherwise, a
47093 value of -1 is returned.
47099 @var{fd} is not a valid open file descriptor.
47102 @var{fd} is associated with the @value{GDBN} console.
47105 @var{flag} is not a proper value.
47108 The call was interrupted by the user.
47114 @unnumberedsubsubsec rename
47115 @cindex rename, file-i/o system call
47120 int rename(const char *oldpath, const char *newpath);
47124 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
47126 @item Return value:
47127 On success, zero is returned. On error, -1 is returned.
47133 @var{newpath} is an existing directory, but @var{oldpath} is not a
47137 @var{newpath} is a non-empty directory.
47140 @var{oldpath} or @var{newpath} is a directory that is in use by some
47144 An attempt was made to make a directory a subdirectory
47148 A component used as a directory in @var{oldpath} or new
47149 path is not a directory. Or @var{oldpath} is a directory
47150 and @var{newpath} exists but is not a directory.
47153 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
47156 No access to the file or the path of the file.
47160 @var{oldpath} or @var{newpath} was too long.
47163 A directory component in @var{oldpath} or @var{newpath} does not exist.
47166 The file is on a read-only filesystem.
47169 The device containing the file has no room for the new
47173 The call was interrupted by the user.
47179 @unnumberedsubsubsec unlink
47180 @cindex unlink, file-i/o system call
47185 int unlink(const char *pathname);
47189 @samp{Funlink,@var{pathnameptr}/@var{len}}
47191 @item Return value:
47192 On success, zero is returned. On error, -1 is returned.
47198 No access to the file or the path of the file.
47201 The system does not allow unlinking of directories.
47204 The file @var{pathname} cannot be unlinked because it's
47205 being used by another process.
47208 @var{pathnameptr} is an invalid pointer value.
47211 @var{pathname} was too long.
47214 A directory component in @var{pathname} does not exist.
47217 A component of the path is not a directory.
47220 The file is on a read-only filesystem.
47223 The call was interrupted by the user.
47229 @unnumberedsubsubsec stat/fstat
47230 @cindex fstat, file-i/o system call
47231 @cindex stat, file-i/o system call
47236 int stat(const char *pathname, struct stat *buf);
47237 int fstat(int fd, struct stat *buf);
47241 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
47242 @samp{Ffstat,@var{fd},@var{bufptr}}
47244 @item Return value:
47245 On success, zero is returned. On error, -1 is returned.
47251 @var{fd} is not a valid open file.
47254 A directory component in @var{pathname} does not exist or the
47255 path is an empty string.
47258 A component of the path is not a directory.
47261 @var{pathnameptr} is an invalid pointer value.
47264 No access to the file or the path of the file.
47267 @var{pathname} was too long.
47270 The call was interrupted by the user.
47276 @unnumberedsubsubsec gettimeofday
47277 @cindex gettimeofday, file-i/o system call
47282 int gettimeofday(struct timeval *tv, void *tz);
47286 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
47288 @item Return value:
47289 On success, 0 is returned, -1 otherwise.
47295 @var{tz} is a non-NULL pointer.
47298 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
47304 @unnumberedsubsubsec isatty
47305 @cindex isatty, file-i/o system call
47310 int isatty(int fd);
47314 @samp{Fisatty,@var{fd}}
47316 @item Return value:
47317 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
47323 The call was interrupted by the user.
47328 Note that the @code{isatty} call is treated as a special case: it returns
47329 1 to the target if the file descriptor is attached
47330 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
47331 would require implementing @code{ioctl} and would be more complex than
47336 @unnumberedsubsubsec system
47337 @cindex system, file-i/o system call
47342 int system(const char *command);
47346 @samp{Fsystem,@var{commandptr}/@var{len}}
47348 @item Return value:
47349 If @var{len} is zero, the return value indicates whether a shell is
47350 available. A zero return value indicates a shell is not available.
47351 For non-zero @var{len}, the value returned is -1 on error and the
47352 return status of the command otherwise. Only the exit status of the
47353 command is returned, which is extracted from the host's @code{system}
47354 return value by calling @code{WEXITSTATUS(retval)}. In case
47355 @file{/bin/sh} could not be executed, 127 is returned.
47361 The call was interrupted by the user.
47366 @value{GDBN} takes over the full task of calling the necessary host calls
47367 to perform the @code{system} call. The return value of @code{system} on
47368 the host is simplified before it's returned
47369 to the target. Any termination signal information from the child process
47370 is discarded, and the return value consists
47371 entirely of the exit status of the called command.
47373 Due to security concerns, the @code{system} call is by default refused
47374 by @value{GDBN}. The user has to allow this call explicitly with the
47375 @code{set remote system-call-allowed 1} command.
47378 @item set remote system-call-allowed
47379 @kindex set remote system-call-allowed
47380 Control whether to allow the @code{system} calls in the File I/O
47381 protocol for the remote target. The default is zero (disabled).
47383 @item show remote system-call-allowed
47384 @kindex show remote system-call-allowed
47385 Show whether the @code{system} calls are allowed in the File I/O
47389 @node Protocol-specific Representation of Datatypes
47390 @subsection Protocol-specific Representation of Datatypes
47391 @cindex protocol-specific representation of datatypes, in file-i/o protocol
47394 * Integral Datatypes::
47396 * Memory Transfer::
47401 @node Integral Datatypes
47402 @unnumberedsubsubsec Integral Datatypes
47403 @cindex integral datatypes, in file-i/o protocol
47405 The integral datatypes used in the system calls are @code{int},
47406 @code{unsigned int}, @code{long}, @code{unsigned long},
47407 @code{mode_t}, and @code{time_t}.
47409 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
47410 implemented as 32 bit values in this protocol.
47412 @code{long} and @code{unsigned long} are implemented as 64 bit types.
47414 @xref{Limits}, for corresponding MIN and MAX values (similar to those
47415 in @file{limits.h}) to allow range checking on host and target.
47417 @code{time_t} datatypes are defined as seconds since the Epoch.
47419 All integral datatypes transferred as part of a memory read or write of a
47420 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
47423 @node Pointer Values
47424 @unnumberedsubsubsec Pointer Values
47425 @cindex pointer values, in file-i/o protocol
47427 Pointers to target data are transmitted as they are. An exception
47428 is made for pointers to buffers for which the length isn't
47429 transmitted as part of the function call, namely strings. Strings
47430 are transmitted as a pointer/length pair, both as hex values, e.g.@:
47437 which is a pointer to data of length 18 bytes at position 0x1aaf.
47438 The length is defined as the full string length in bytes, including
47439 the trailing null byte. For example, the string @code{"hello world"}
47440 at address 0x123456 is transmitted as
47446 @node Memory Transfer
47447 @unnumberedsubsubsec Memory Transfer
47448 @cindex memory transfer, in file-i/o protocol
47450 Structured data which is transferred using a memory read or write (for
47451 example, a @code{struct stat}) is expected to be in a protocol-specific format
47452 with all scalar multibyte datatypes being big endian. Translation to
47453 this representation needs to be done both by the target before the @code{F}
47454 packet is sent, and by @value{GDBN} before
47455 it transfers memory to the target. Transferred pointers to structured
47456 data should point to the already-coerced data at any time.
47460 @unnumberedsubsubsec struct stat
47461 @cindex struct stat, in file-i/o protocol
47463 The buffer of type @code{struct stat} used by the target and @value{GDBN}
47464 is defined as follows:
47468 unsigned int st_dev; /* device */
47469 unsigned int st_ino; /* inode */
47470 mode_t st_mode; /* protection */
47471 unsigned int st_nlink; /* number of hard links */
47472 unsigned int st_uid; /* user ID of owner */
47473 unsigned int st_gid; /* group ID of owner */
47474 unsigned int st_rdev; /* device type (if inode device) */
47475 unsigned long st_size; /* total size, in bytes */
47476 unsigned long st_blksize; /* blocksize for filesystem I/O */
47477 unsigned long st_blocks; /* number of blocks allocated */
47478 time_t st_atime; /* time of last access */
47479 time_t st_mtime; /* time of last modification */
47480 time_t st_ctime; /* time of last change */
47484 The integral datatypes conform to the definitions given in the
47485 appropriate section (see @ref{Integral Datatypes}, for details) so this
47486 structure is of size 64 bytes.
47488 The values of several fields have a restricted meaning and/or
47494 A value of 0 represents a file, 1 the console.
47497 No valid meaning for the target. Transmitted unchanged.
47500 Valid mode bits are described in @ref{Constants}. Any other
47501 bits have currently no meaning for the target.
47506 No valid meaning for the target. Transmitted unchanged.
47511 These values have a host and file system dependent
47512 accuracy. Especially on Windows hosts, the file system may not
47513 support exact timing values.
47516 The target gets a @code{struct stat} of the above representation and is
47517 responsible for coercing it to the target representation before
47520 Note that due to size differences between the host, target, and protocol
47521 representations of @code{struct stat} members, these members could eventually
47522 get truncated on the target.
47524 @node struct timeval
47525 @unnumberedsubsubsec struct timeval
47526 @cindex struct timeval, in file-i/o protocol
47528 The buffer of type @code{struct timeval} used by the File-I/O protocol
47529 is defined as follows:
47533 time_t tv_sec; /* second */
47534 long tv_usec; /* microsecond */
47538 The integral datatypes conform to the definitions given in the
47539 appropriate section (see @ref{Integral Datatypes}, for details) so this
47540 structure is of size 8 bytes.
47543 @subsection Constants
47544 @cindex constants, in file-i/o protocol
47546 The following values are used for the constants inside of the
47547 protocol. @value{GDBN} and target are responsible for translating these
47548 values before and after the call as needed.
47559 @unnumberedsubsubsec Open Flags
47560 @cindex open flags, in file-i/o protocol
47562 All values are given in hexadecimal representation.
47574 @node mode_t Values
47575 @unnumberedsubsubsec mode_t Values
47576 @cindex mode_t values, in file-i/o protocol
47578 All values are given in octal representation.
47595 @unnumberedsubsubsec Errno Values
47596 @cindex errno values, in file-i/o protocol
47598 All values are given in decimal representation.
47623 @code{EUNKNOWN} is used as a fallback error value if a host system returns
47624 any error value not in the list of supported error numbers.
47627 @unnumberedsubsubsec Lseek Flags
47628 @cindex lseek flags, in file-i/o protocol
47637 @unnumberedsubsubsec Limits
47638 @cindex limits, in file-i/o protocol
47640 All values are given in decimal representation.
47643 INT_MIN -2147483648
47645 UINT_MAX 4294967295
47646 LONG_MIN -9223372036854775808
47647 LONG_MAX 9223372036854775807
47648 ULONG_MAX 18446744073709551615
47651 @node File-I/O Examples
47652 @subsection File-I/O Examples
47653 @cindex file-i/o examples
47655 Example sequence of a write call, file descriptor 3, buffer is at target
47656 address 0x1234, 6 bytes should be written:
47659 <- @code{Fwrite,3,1234,6}
47660 @emph{request memory read from target}
47663 @emph{return "6 bytes written"}
47667 Example sequence of a read call, file descriptor 3, buffer is at target
47668 address 0x1234, 6 bytes should be read:
47671 <- @code{Fread,3,1234,6}
47672 @emph{request memory write to target}
47673 -> @code{X1234,6:XXXXXX}
47674 @emph{return "6 bytes read"}
47678 Example sequence of a read call, call fails on the host due to invalid
47679 file descriptor (@code{EBADF}):
47682 <- @code{Fread,3,1234,6}
47686 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
47690 <- @code{Fread,3,1234,6}
47695 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
47699 <- @code{Fread,3,1234,6}
47700 -> @code{X1234,6:XXXXXX}
47704 @node Library List Format
47705 @section Library List Format
47706 @cindex library list format, remote protocol
47708 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
47709 same process as your application to manage libraries. In this case,
47710 @value{GDBN} can use the loader's symbol table and normal memory
47711 operations to maintain a list of shared libraries. On other
47712 platforms, the operating system manages loaded libraries.
47713 @value{GDBN} can not retrieve the list of currently loaded libraries
47714 through memory operations, so it uses the @samp{qXfer:libraries:read}
47715 packet (@pxref{qXfer library list read}) instead. The remote stub
47716 queries the target's operating system and reports which libraries
47719 The @samp{qXfer:libraries:read} packet returns an XML document which
47720 lists loaded libraries and their offsets. Each library has an
47721 associated name and one or more segment or section base addresses,
47722 which report where the library was loaded in memory.
47724 For the common case of libraries that are fully linked binaries, the
47725 library should have a list of segments. If the target supports
47726 dynamic linking of a relocatable object file, its library XML element
47727 should instead include a list of allocated sections. The segment or
47728 section bases are start addresses, not relocation offsets; they do not
47729 depend on the library's link-time base addresses.
47731 @value{GDBN} must be linked with the Expat library to support XML
47732 library lists. @xref{Expat}.
47734 A simple memory map, with one loaded library relocated by a single
47735 offset, looks like this:
47739 <library name="/lib/libc.so.6">
47740 <segment address="0x10000000"/>
47745 Another simple memory map, with one loaded library with three
47746 allocated sections (.text, .data, .bss), looks like this:
47750 <library name="sharedlib.o">
47751 <section address="0x10000000"/>
47752 <section address="0x20000000"/>
47753 <section address="0x30000000"/>
47758 The format of a library list is described by this DTD:
47761 <!-- library-list: Root element with versioning -->
47762 <!ELEMENT library-list (library)*>
47763 <!ATTLIST library-list version CDATA #FIXED "1.0">
47764 <!ELEMENT library (segment*, section*)>
47765 <!ATTLIST library name CDATA #REQUIRED>
47766 <!ELEMENT segment EMPTY>
47767 <!ATTLIST segment address CDATA #REQUIRED>
47768 <!ELEMENT section EMPTY>
47769 <!ATTLIST section address CDATA #REQUIRED>
47772 In addition, segments and section descriptors cannot be mixed within a
47773 single library element, and you must supply at least one segment or
47774 section for each library.
47776 @node Library List Format for SVR4 Targets
47777 @section Library List Format for SVR4 Targets
47778 @cindex library list format, remote protocol
47780 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
47781 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
47782 shared libraries. Still a special library list provided by this packet is
47783 more efficient for the @value{GDBN} remote protocol.
47785 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
47786 loaded libraries and their SVR4 linker parameters. For each library on SVR4
47787 target, the following parameters are reported:
47791 @code{name}, the absolute file name from the @code{l_name} field of
47792 @code{struct link_map}.
47794 @code{lm} with address of @code{struct link_map} used for TLS
47795 (Thread Local Storage) access.
47797 @code{l_addr}, the displacement as read from the field @code{l_addr} of
47798 @code{struct link_map}. For prelinked libraries this is not an absolute
47799 memory address. It is a displacement of absolute memory address against
47800 address the file was prelinked to during the library load.
47802 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
47804 @code{lmid}, which is an identifier for a linker namespace, such as
47805 the memory address of the @code{r_debug} object that contains this
47806 namespace's load map or the namespace identifier returned by
47810 Additionally the single @code{main-lm} attribute specifies address of
47811 @code{struct link_map} used for the main executable. This parameter is used
47812 for TLS access and its presence is optional.
47814 @value{GDBN} must be linked with the Expat library to support XML
47815 SVR4 library lists. @xref{Expat}.
47817 A simple memory map, with two loaded libraries (which do not use prelink),
47821 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
47822 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
47823 l_ld="0xe4eefc" lmid="0xfffe0"/>
47824 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
47825 l_ld="0x152350" lmid="0xfffe0"/>
47826 </library-list-svr>
47829 The format of an SVR4 library list is described by this DTD:
47832 <!-- library-list-svr4: Root element with versioning -->
47833 <!ELEMENT library-list-svr4 (library)*>
47834 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
47835 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
47836 <!ELEMENT library EMPTY>
47837 <!ATTLIST library name CDATA #REQUIRED>
47838 <!ATTLIST library lm CDATA #REQUIRED>
47839 <!ATTLIST library l_addr CDATA #REQUIRED>
47840 <!ATTLIST library l_ld CDATA #REQUIRED>
47841 <!ATTLIST library lmid CDATA #IMPLIED>
47844 @node Memory Map Format
47845 @section Memory Map Format
47846 @cindex memory map format
47848 To be able to write into flash memory, @value{GDBN} needs to obtain a
47849 memory map from the target. This section describes the format of the
47852 The memory map is obtained using the @samp{qXfer:memory-map:read}
47853 (@pxref{qXfer memory map read}) packet and is an XML document that
47854 lists memory regions.
47856 @value{GDBN} must be linked with the Expat library to support XML
47857 memory maps. @xref{Expat}.
47859 The top-level structure of the document is shown below:
47862 <?xml version="1.0"?>
47863 <!DOCTYPE memory-map
47864 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
47865 "http://sourceware.org/gdb/gdb-memory-map.dtd">
47871 Each region can be either:
47876 A region of RAM starting at @var{addr} and extending for @var{length}
47880 <memory type="ram" start="@var{addr}" length="@var{length}"/>
47885 A region of read-only memory:
47888 <memory type="rom" start="@var{addr}" length="@var{length}"/>
47893 A region of flash memory, with erasure blocks @var{blocksize}
47897 <memory type="flash" start="@var{addr}" length="@var{length}">
47898 <property name="blocksize">@var{blocksize}</property>
47904 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
47905 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
47906 packets to write to addresses in such ranges.
47908 The formal DTD for memory map format is given below:
47911 <!-- ................................................... -->
47912 <!-- Memory Map XML DTD ................................ -->
47913 <!-- File: memory-map.dtd .............................. -->
47914 <!-- .................................... .............. -->
47915 <!-- memory-map.dtd -->
47916 <!-- memory-map: Root element with versioning -->
47917 <!ELEMENT memory-map (memory)*>
47918 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
47919 <!ELEMENT memory (property)*>
47920 <!-- memory: Specifies a memory region,
47921 and its type, or device. -->
47922 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
47923 start CDATA #REQUIRED
47924 length CDATA #REQUIRED>
47925 <!-- property: Generic attribute tag -->
47926 <!ELEMENT property (#PCDATA | property)*>
47927 <!ATTLIST property name (blocksize) #REQUIRED>
47930 @node Thread List Format
47931 @section Thread List Format
47932 @cindex thread list format
47934 To efficiently update the list of threads and their attributes,
47935 @value{GDBN} issues the @samp{qXfer:threads:read} packet
47936 (@pxref{qXfer threads read}) and obtains the XML document with
47937 the following structure:
47940 <?xml version="1.0"?>
47942 <thread id="id" core="0" name="name">
47943 ... description ...
47948 Each @samp{thread} element must have the @samp{id} attribute that
47949 identifies the thread (@pxref{thread-id syntax}). The
47950 @samp{core} attribute, if present, specifies which processor core
47951 the thread was last executing on. The @samp{name} attribute, if
47952 present, specifies the human-readable name of the thread. The content
47953 of the of @samp{thread} element is interpreted as human-readable
47954 auxiliary information. The @samp{handle} attribute, if present,
47955 is a hex encoded representation of the thread handle.
47958 @node Traceframe Info Format
47959 @section Traceframe Info Format
47960 @cindex traceframe info format
47962 To be able to know which objects in the inferior can be examined when
47963 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
47964 memory ranges, registers and trace state variables that have been
47965 collected in a traceframe.
47967 This list is obtained using the @samp{qXfer:traceframe-info:read}
47968 (@pxref{qXfer traceframe info read}) packet and is an XML document.
47970 @value{GDBN} must be linked with the Expat library to support XML
47971 traceframe info discovery. @xref{Expat}.
47973 The top-level structure of the document is shown below:
47976 <?xml version="1.0"?>
47977 <!DOCTYPE traceframe-info
47978 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
47979 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
47985 Each traceframe block can be either:
47990 A region of collected memory starting at @var{addr} and extending for
47991 @var{length} bytes from there:
47994 <memory start="@var{addr}" length="@var{length}"/>
47998 A block indicating trace state variable numbered @var{number} has been
48002 <tvar id="@var{number}"/>
48007 The formal DTD for the traceframe info format is given below:
48010 <!ELEMENT traceframe-info (memory | tvar)* >
48011 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
48013 <!ELEMENT memory EMPTY>
48014 <!ATTLIST memory start CDATA #REQUIRED
48015 length CDATA #REQUIRED>
48017 <!ATTLIST tvar id CDATA #REQUIRED>
48020 @node Branch Trace Format
48021 @section Branch Trace Format
48022 @cindex branch trace format
48024 In order to display the branch trace of an inferior thread,
48025 @value{GDBN} needs to obtain the list of branches. This list is
48026 represented as list of sequential code blocks that are connected via
48027 branches. The code in each block has been executed sequentially.
48029 This list is obtained using the @samp{qXfer:btrace:read}
48030 (@pxref{qXfer btrace read}) packet and is an XML document.
48032 @value{GDBN} must be linked with the Expat library to support XML
48033 traceframe info discovery. @xref{Expat}.
48035 The top-level structure of the document is shown below:
48038 <?xml version="1.0"?>
48040 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
48041 "http://sourceware.org/gdb/gdb-btrace.dtd">
48050 A block of sequentially executed instructions starting at @var{begin}
48051 and ending at @var{end}:
48054 <block begin="@var{begin}" end="@var{end}"/>
48059 The formal DTD for the branch trace format is given below:
48062 <!ELEMENT btrace (block* | pt) >
48063 <!ATTLIST btrace version CDATA #FIXED "1.0">
48065 <!ELEMENT block EMPTY>
48066 <!ATTLIST block begin CDATA #REQUIRED
48067 end CDATA #REQUIRED>
48069 <!ELEMENT pt (pt-config?, raw?)>
48071 <!ELEMENT pt-config (cpu?)>
48073 <!ELEMENT cpu EMPTY>
48074 <!ATTLIST cpu vendor CDATA #REQUIRED
48075 family CDATA #REQUIRED
48076 model CDATA #REQUIRED
48077 stepping CDATA #REQUIRED>
48079 <!ELEMENT raw (#PCDATA)>
48082 @node Branch Trace Configuration Format
48083 @section Branch Trace Configuration Format
48084 @cindex branch trace configuration format
48086 For each inferior thread, @value{GDBN} can obtain the branch trace
48087 configuration using the @samp{qXfer:btrace-conf:read}
48088 (@pxref{qXfer btrace-conf read}) packet.
48090 The configuration describes the branch trace format and configuration
48091 settings for that format. The following information is described:
48095 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
48098 The size of the @acronym{BTS} ring buffer in bytes.
48101 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
48105 The size of the @acronym{Intel PT} ring buffer in bytes.
48109 @value{GDBN} must be linked with the Expat library to support XML
48110 branch trace configuration discovery. @xref{Expat}.
48112 The formal DTD for the branch trace configuration format is given below:
48115 <!ELEMENT btrace-conf (bts?, pt?)>
48116 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
48118 <!ELEMENT bts EMPTY>
48119 <!ATTLIST bts size CDATA #IMPLIED>
48121 <!ELEMENT pt EMPTY>
48122 <!ATTLIST pt size CDATA #IMPLIED>
48125 @include agentexpr.texi
48127 @node Target Descriptions
48128 @appendix Target Descriptions
48129 @cindex target descriptions
48131 One of the challenges of using @value{GDBN} to debug embedded systems
48132 is that there are so many minor variants of each processor
48133 architecture in use. It is common practice for vendors to start with
48134 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
48135 and then make changes to adapt it to a particular market niche. Some
48136 architectures have hundreds of variants, available from dozens of
48137 vendors. This leads to a number of problems:
48141 With so many different customized processors, it is difficult for
48142 the @value{GDBN} maintainers to keep up with the changes.
48144 Since individual variants may have short lifetimes or limited
48145 audiences, it may not be worthwhile to carry information about every
48146 variant in the @value{GDBN} source tree.
48148 When @value{GDBN} does support the architecture of the embedded system
48149 at hand, the task of finding the correct architecture name to give the
48150 @command{set architecture} command can be error-prone.
48153 To address these problems, the @value{GDBN} remote protocol allows a
48154 target system to not only identify itself to @value{GDBN}, but to
48155 actually describe its own features. This lets @value{GDBN} support
48156 processor variants it has never seen before --- to the extent that the
48157 descriptions are accurate, and that @value{GDBN} understands them.
48159 @value{GDBN} must be linked with the Expat library to support XML
48160 target descriptions. @xref{Expat}.
48163 * Retrieving Descriptions:: How descriptions are fetched from a target.
48164 * Target Description Format:: The contents of a target description.
48165 * Predefined Target Types:: Standard types available for target
48167 * Enum Target Types:: How to define enum target types.
48168 * Standard Target Features:: Features @value{GDBN} knows about.
48171 @node Retrieving Descriptions
48172 @section Retrieving Descriptions
48174 Target descriptions can be read from the target automatically, or
48175 specified by the user manually. The default behavior is to read the
48176 description from the target. @value{GDBN} retrieves it via the remote
48177 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
48178 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
48179 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
48180 XML document, of the form described in @ref{Target Description
48183 Alternatively, you can specify a file to read for the target description.
48184 If a file is set, the target will not be queried. The commands to
48185 specify a file are:
48188 @cindex set tdesc filename
48189 @item set tdesc filename @var{path}
48190 Read the target description from @var{path}.
48192 @cindex unset tdesc filename
48193 @item unset tdesc filename
48194 Do not read the XML target description from a file. @value{GDBN}
48195 will use the description supplied by the current target.
48197 @cindex show tdesc filename
48198 @item show tdesc filename
48199 Show the filename to read for a target description, if any.
48203 @node Target Description Format
48204 @section Target Description Format
48205 @cindex target descriptions, XML format
48207 A target description annex is an @uref{http://www.w3.org/XML/, XML}
48208 document which complies with the Document Type Definition provided in
48209 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
48210 means you can use generally available tools like @command{xmllint} to
48211 check that your feature descriptions are well-formed and valid.
48212 However, to help people unfamiliar with XML write descriptions for
48213 their targets, we also describe the grammar here.
48215 Target descriptions can identify the architecture of the remote target
48216 and (for some architectures) provide information about custom register
48217 sets. They can also identify the OS ABI of the remote target.
48218 @value{GDBN} can use this information to autoconfigure for your
48219 target, or to warn you if you connect to an unsupported target.
48221 Here is a simple target description:
48224 <target version="1.0">
48225 <architecture>i386:x86-64</architecture>
48230 This minimal description only says that the target uses
48231 the x86-64 architecture.
48233 A target description has the following overall form, with [ ] marking
48234 optional elements and @dots{} marking repeatable elements. The elements
48235 are explained further below.
48238 <?xml version="1.0"?>
48239 <!DOCTYPE target SYSTEM "gdb-target.dtd">
48240 <target version="1.0">
48241 @r{[}@var{architecture}@r{]}
48242 @r{[}@var{osabi}@r{]}
48243 @r{[}@var{compatible}@r{]}
48244 @r{[}@var{feature}@dots{}@r{]}
48249 The description is generally insensitive to whitespace and line
48250 breaks, under the usual common-sense rules. The XML version
48251 declaration and document type declaration can generally be omitted
48252 (@value{GDBN} does not require them), but specifying them may be
48253 useful for XML validation tools. The @samp{version} attribute for
48254 @samp{<target>} may also be omitted, but we recommend
48255 including it; if future versions of @value{GDBN} use an incompatible
48256 revision of @file{gdb-target.dtd}, they will detect and report
48257 the version mismatch.
48259 @subsection Inclusion
48260 @cindex target descriptions, inclusion
48263 @cindex <xi:include>
48266 It can sometimes be valuable to split a target description up into
48267 several different annexes, either for organizational purposes, or to
48268 share files between different possible target descriptions. You can
48269 divide a description into multiple files by replacing any element of
48270 the target description with an inclusion directive of the form:
48273 <xi:include href="@var{document}"/>
48277 When @value{GDBN} encounters an element of this form, it will retrieve
48278 the named XML @var{document}, and replace the inclusion directive with
48279 the contents of that document. If the current description was read
48280 using @samp{qXfer}, then so will be the included document;
48281 @var{document} will be interpreted as the name of an annex. If the
48282 current description was read from a file, @value{GDBN} will look for
48283 @var{document} as a file in the same directory where it found the
48284 original description.
48286 @subsection Architecture
48287 @cindex <architecture>
48289 An @samp{<architecture>} element has this form:
48292 <architecture>@var{arch}</architecture>
48295 @var{arch} is one of the architectures from the set accepted by
48296 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
48299 @cindex @code{<osabi>}
48301 This optional field was introduced in @value{GDBN} version 7.0.
48302 Previous versions of @value{GDBN} ignore it.
48304 An @samp{<osabi>} element has this form:
48307 <osabi>@var{abi-name}</osabi>
48310 @var{abi-name} is an OS ABI name from the same selection accepted by
48311 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
48313 @subsection Compatible Architecture
48314 @cindex @code{<compatible>}
48316 This optional field was introduced in @value{GDBN} version 7.0.
48317 Previous versions of @value{GDBN} ignore it.
48319 A @samp{<compatible>} element has this form:
48322 <compatible>@var{arch}</compatible>
48325 @var{arch} is one of the architectures from the set accepted by
48326 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
48328 A @samp{<compatible>} element is used to specify that the target
48329 is able to run binaries in some other than the main target architecture
48330 given by the @samp{<architecture>} element. For example, on the
48331 Cell Broadband Engine, the main architecture is @code{powerpc:common}
48332 or @code{powerpc:common64}, but the system is able to run binaries
48333 in the @code{spu} architecture as well. The way to describe this
48334 capability with @samp{<compatible>} is as follows:
48337 <architecture>powerpc:common</architecture>
48338 <compatible>spu</compatible>
48341 @subsection Features
48344 Each @samp{<feature>} describes some logical portion of the target
48345 system. Features are currently used to describe available CPU
48346 registers and the types of their contents. A @samp{<feature>} element
48350 <feature name="@var{name}">
48351 @r{[}@var{type}@dots{}@r{]}
48357 Each feature's name should be unique within the description. The name
48358 of a feature does not matter unless @value{GDBN} has some special
48359 knowledge of the contents of that feature; if it does, the feature
48360 should have its standard name. @xref{Standard Target Features}.
48364 Any register's value is a collection of bits which @value{GDBN} must
48365 interpret. The default interpretation is a two's complement integer,
48366 but other types can be requested by name in the register description.
48367 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
48368 Target Types}), and the description can define additional composite
48371 Each type element must have an @samp{id} attribute, which gives
48372 a unique (within the containing @samp{<feature>}) name to the type.
48373 Types must be defined before they are used.
48376 Some targets offer vector registers, which can be treated as arrays
48377 of scalar elements. These types are written as @samp{<vector>} elements,
48378 specifying the array element type, @var{type}, and the number of elements,
48382 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
48386 If a register's value is usefully viewed in multiple ways, define it
48387 with a union type containing the useful representations. The
48388 @samp{<union>} element contains one or more @samp{<field>} elements,
48389 each of which has a @var{name} and a @var{type}:
48392 <union id="@var{id}">
48393 <field name="@var{name}" type="@var{type}"/>
48400 If a register's value is composed from several separate values, define
48401 it with either a structure type or a flags type.
48402 A flags type may only contain bitfields.
48403 A structure type may either contain only bitfields or contain no bitfields.
48404 If the value contains only bitfields, its total size in bytes must be
48407 Non-bitfield values have a @var{name} and @var{type}.
48410 <struct id="@var{id}">
48411 <field name="@var{name}" type="@var{type}"/>
48416 Both @var{name} and @var{type} values are required.
48417 No implicit padding is added.
48419 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
48422 <struct id="@var{id}" size="@var{size}">
48423 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
48429 <flags id="@var{id}" size="@var{size}">
48430 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
48435 The @var{name} value is required.
48436 Bitfield values may be named with the empty string, @samp{""},
48437 in which case the field is ``filler'' and its value is not printed.
48438 Not all bits need to be specified, so ``filler'' fields are optional.
48440 The @var{start} and @var{end} values are required, and @var{type}
48442 The field's @var{start} must be less than or equal to its @var{end},
48443 and zero represents the least significant bit.
48445 The default value of @var{type} is @code{bool} for single bit fields,
48446 and an unsigned integer otherwise.
48448 Which to choose? Structures or flags?
48450 Registers defined with @samp{flags} have these advantages over
48451 defining them with @samp{struct}:
48455 Arithmetic may be performed on them as if they were integers.
48457 They are printed in a more readable fashion.
48460 Registers defined with @samp{struct} have one advantage over
48461 defining them with @samp{flags}:
48465 One can fetch individual fields like in @samp{C}.
48468 (@value{GDBP}) print $my_struct_reg.field3
48474 @subsection Registers
48477 Each register is represented as an element with this form:
48480 <reg name="@var{name}"
48481 bitsize="@var{size}"
48482 @r{[}regnum="@var{num}"@r{]}
48483 @r{[}save-restore="@var{save-restore}"@r{]}
48484 @r{[}type="@var{type}"@r{]}
48485 @r{[}group="@var{group}"@r{]}/>
48489 The components are as follows:
48494 The register's name; it must be unique within the target description.
48497 The register's size, in bits.
48500 The register's number. If omitted, a register's number is one greater
48501 than that of the previous register (either in the current feature or in
48502 a preceding feature); the first register in the target description
48503 defaults to zero. This register number is used to read or write
48504 the register; e.g.@: it is used in the remote @code{p} and @code{P}
48505 packets, and registers appear in the @code{g} and @code{G} packets
48506 in order of increasing register number.
48509 Whether the register should be preserved across inferior function
48510 calls; this must be either @code{yes} or @code{no}. The default is
48511 @code{yes}, which is appropriate for most registers except for
48512 some system control registers; this is not related to the target's
48516 The type of the register. It may be a predefined type, a type
48517 defined in the current feature, or one of the special types @code{int}
48518 and @code{float}. @code{int} is an integer type of the correct size
48519 for @var{bitsize}, and @code{float} is a floating point type (in the
48520 architecture's normal floating point format) of the correct size for
48521 @var{bitsize}. The default is @code{int}.
48524 The register group to which this register belongs. It can be one of the
48525 standard register groups @code{general}, @code{float}, @code{vector} or an
48526 arbitrary string. Group names should be limited to alphanumeric characters.
48527 If a group name is made up of multiple words the words may be separated by
48528 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
48529 @var{group} is specified, @value{GDBN} will not display the register in
48530 @code{info registers}.
48534 @node Predefined Target Types
48535 @section Predefined Target Types
48536 @cindex target descriptions, predefined types
48538 Type definitions in the self-description can build up composite types
48539 from basic building blocks, but can not define fundamental types. Instead,
48540 standard identifiers are provided by @value{GDBN} for the fundamental
48541 types. The currently supported types are:
48546 Boolean type, occupying a single bit.
48554 Signed integer types holding the specified number of bits.
48562 Unsigned integer types holding the specified number of bits.
48566 Pointers to unspecified code and data. The program counter and
48567 any dedicated return address register may be marked as code
48568 pointers; printing a code pointer converts it into a symbolic
48569 address. The stack pointer and any dedicated address registers
48570 may be marked as data pointers.
48573 Half precision IEEE floating point.
48576 Single precision IEEE floating point.
48579 Double precision IEEE floating point.
48582 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
48585 The 12-byte extended precision format used by ARM FPA registers.
48588 The 10-byte extended precision format used by x87 registers.
48591 32bit @sc{eflags} register used by x86.
48594 32bit @sc{mxcsr} register used by x86.
48598 @node Enum Target Types
48599 @section Enum Target Types
48600 @cindex target descriptions, enum types
48602 Enum target types are useful in @samp{struct} and @samp{flags}
48603 register descriptions. @xref{Target Description Format}.
48605 Enum types have a name, size and a list of name/value pairs.
48608 <enum id="@var{id}" size="@var{size}">
48609 <evalue name="@var{name}" value="@var{value}"/>
48614 Enums must be defined before they are used.
48617 <enum id="levels_type" size="4">
48618 <evalue name="low" value="0"/>
48619 <evalue name="high" value="1"/>
48621 <flags id="flags_type" size="4">
48622 <field name="X" start="0"/>
48623 <field name="LEVEL" start="1" end="1" type="levels_type"/>
48625 <reg name="flags" bitsize="32" type="flags_type"/>
48628 Given that description, a value of 3 for the @samp{flags} register
48629 would be printed as:
48632 (@value{GDBP}) info register flags
48633 flags 0x3 [ X LEVEL=high ]
48636 @node Standard Target Features
48637 @section Standard Target Features
48638 @cindex target descriptions, standard features
48640 A target description must contain either no registers or all the
48641 target's registers. If the description contains no registers, then
48642 @value{GDBN} will assume a default register layout, selected based on
48643 the architecture. If the description contains any registers, the
48644 default layout will not be used; the standard registers must be
48645 described in the target description, in such a way that @value{GDBN}
48646 can recognize them.
48648 This is accomplished by giving specific names to feature elements
48649 which contain standard registers. @value{GDBN} will look for features
48650 with those names and verify that they contain the expected registers;
48651 if any known feature is missing required registers, or if any required
48652 feature is missing, @value{GDBN} will reject the target
48653 description. You can add additional registers to any of the
48654 standard features --- @value{GDBN} will display them just as if
48655 they were added to an unrecognized feature.
48657 This section lists the known features and their expected contents.
48658 Sample XML documents for these features are included in the
48659 @value{GDBN} source tree, in the directory @file{gdb/features}.
48661 Names recognized by @value{GDBN} should include the name of the
48662 company or organization which selected the name, and the overall
48663 architecture to which the feature applies; so e.g.@: the feature
48664 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
48666 The names of registers are not case sensitive for the purpose
48667 of recognizing standard features, but @value{GDBN} will only display
48668 registers using the capitalization used in the description.
48671 * AArch64 Features::
48675 * LoongArch Features::
48676 * MicroBlaze Features::
48680 * Nios II Features::
48681 * OpenRISC 1000 Features::
48682 * PowerPC Features::
48683 * RISC-V Features::
48685 * S/390 and System z Features::
48691 @node AArch64 Features
48692 @subsection AArch64 Features
48693 @cindex target descriptions, AArch64 features
48695 @subsubsection AArch64 core registers feature
48697 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
48698 targets. It must contain the following:
48702 @samp{x0} through @samp{x30}, the general purpose registers, with size of
48703 64 bits. Register @samp{x30} is also known as the @dfn{link register},
48706 @samp{sp}, the stack pointer register or @samp{x31}. It is 64 bits in size and
48707 has a type of @samp{data_ptr}.
48709 @samp{pc}, the program counter register. It is 64 bits in size and has a type
48710 of @samp{code_ptr}.
48712 @samp{cpsr}, the current program status register. It is 32 bits in size
48713 and has a custom flags type.
48716 The semantics of the individual flags and fields in @samp{cpsr} can change as
48717 new architectural features are added. The current layout can be found in the
48718 aarch64-core.xml file.
48720 Extra registers are allowed in this feature, but they will not affect
48723 @subsubsection AArch64 floating-point registers feature
48725 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
48726 it must contain the following registers:
48730 @samp{v0} through @samp{v31}, the vector registers with size of 128 bits. The
48731 type is a custom vector type.
48733 @samp{fpsr}, the floating-point status register. It is 32 bits in size and has
48734 a custom flags type.
48736 @samp{fpcr}, the floating-point control register. It is 32 bits in size and has
48737 a custom flags type.
48740 The semantics of the individual flags and fields in @samp{fpsr} and @samp{fpcr}
48741 can change as new architectural features are added.
48743 The types for the vector registers, @samp{fpsr} and @samp{fpcr} registers can
48744 be found in the aarch64-fpu.xml file.
48746 Extra registers are allowed in this feature, but they will not affect
48749 @subsubsection AArch64 SVE registers feature
48751 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
48752 it means the target supports the Scalable Vector Extension and must contain
48753 the following registers:
48757 @samp{z0} through @samp{z31}, the scalable vector registers. Their sizes are
48758 variable and a multiple of 128 bits up to a maximum of 2048 bit. Their type is
48759 a custom union type that helps visualize different sizes of sub-vectors.
48761 @samp{fpsr}, the floating-point status register. It is 32 bits in size and has
48762 a custom flags type.
48764 @samp{fpcr}, the floating-point control register. It is 32 bits in size and has
48765 a custom flags type.
48767 @samp{p0} through @samp{p15}, the predicate registers. Their sizes are
48768 variable, based on the current vector length, and a multiple of
48769 16 bits. Their types are a custom union to help visualize sub-elements.
48771 @samp{ffr}, the First Fault register. It has a variable size based on the
48772 current vector length and is a multiple of 16 bits. The type is the same as
48773 the predicate registers.
48775 @samp{vg}, the vector granule. It represents the number of 64 bits chunks in
48776 a @samp{z} register. It is closely associated with the current vector
48777 length. It has a type of @samp{int}.
48780 When @value{GDBN} sees the SVE feature, it will assume the Scalable Vector
48781 Extension is supported, and will adjust the sizes of the @samp{z}, @samp{p}
48782 and @samp{ffr} registers accordingly, based on the value of @samp{vg}.
48784 @value{GDBN} will also create pseudo-registers equivalent to the @samp{v}
48785 vector registers from the @samp{org.gnu.gdb.aarch64.fpu} feature.
48787 The first 128 bits of the @samp{z} registers overlap the 128 bits of the
48788 @samp{v} registers, so changing one will trigger a change to the other.
48790 For the types of the @samp{z}, @samp{p} and @samp{ffr} registers, please
48791 check the aarch64-sve.c file. No XML file is available for this feature
48792 because it is dynamically generated based on the current vector length.
48794 The semantics of the individual flags and fields in @samp{fpsr} and @samp{fpcr}
48795 can change as new architectural features are added.
48797 The types for the @samp{fpsr} and @samp{fpcr} registers can be found in the
48798 aarch64-sve.c file, and should match what is described in aarch64-fpu.xml.
48800 Extra registers are allowed in this feature, but they will not affect
48803 @subsubsection AArch64 Pointer Authentication registers feature
48805 The @samp{org.gnu.gdb.aarch64.pauth} optional feature was introduced so
48806 @value{GDBN} could detect support for the Pointer Authentication
48807 extension. If present, it must contain one of two possible register sets.
48809 Pointer Authentication masks for user-mode:
48813 @samp{pauth_dmask}, the user-mode pointer authentication mask for data
48814 pointers. It is 64 bits in size.
48816 @samp{pauth_cmask}, the user-mode pointer authentication mask for code
48817 pointers. It is 64 bits in size.
48820 Pointer Authentication masks for user-mode and kernel-mode:
48824 @samp{pauth_dmask}, the user-mode pointer authentication mask for data
48825 pointers. It is 64 bits in size.
48827 @samp{pauth_cmask}, the user-mode pointer authentication mask for code
48828 pointers. It is 64 bits in size.
48830 @samp{pauth_dmask_high}, the kernel-mode pointer authentication mask for
48831 data pointers. It is 64 bits in size.
48833 @samp{pauth_cmask_high}, the kernel-mode pointer authentication mask for
48834 code pointers. It is 64 bits in size.
48837 If @value{GDBN} sees any of the two sets of registers in this feature, it will
48838 assume the target is capable of signing pointers. If so, @value{GDBN} will
48839 decorate backtraces with a @samp{[PAC]} marker alongside a function that
48840 has a signed link register value that needs to be unmasked/decoded.
48842 @value{GDBN} will also use the masks to remove non-address bits from pointers.
48844 Extra registers are allowed in this feature, but they will not affect
48847 Please note the @samp{org.gnu.gdb.aarch64.pauth} feature string is deprecated
48848 and must only be used for backwards compatibility with older releases of
48849 @value{GDBN} and @command{gdbserver}. Targets that support Pointer
48850 Authentication must advertise such capability by using the
48851 @samp{org.gnu.gdb.aarch64.pauth_v2} feature string instead.
48853 The @samp{org.gnu.gdb.aarch64.pauth_v2} feature has the exact same contents
48854 as feature @samp{org.gnu.gdb.aarch64.pauth}.
48856 The reason for having feature @samp{org.gnu.gdb.aarch64.pauth_v2} is a bug in
48857 previous versions of @value{GDBN} (versions 9, 10, 11 and 12). This bug
48858 caused @value{GDBN} to crash whenever the target reported support for Pointer
48859 Authentication (using feature string @samp{org.gnu.gdb.aarch64.pauth}) and also
48860 reported additional system registers that were not accounted for by
48861 @value{GDBN}. This is more common when using emulators and on bare-metal
48862 debugging scenarios.
48864 It can also happen if a newer gdbserver is used with an old @value{GDBN} that
48865 has the bug. In such a case, the newer gdbserver might report Pointer
48866 Authentication support via the @samp{org.gnu.gdb.aarch64.pauth} feature string
48867 and also report additional registers the older @value{GDBN} does not know
48868 about, potentially leading to a crash.
48870 @subsubsection AArch64 TLS registers feature
48872 The @samp{org.gnu.gdb.aarch64.tls} optional feature was introduced to expose
48873 the TLS registers to @value{GDBN}. If present, it must contain either one
48874 of the following register sets.
48880 @samp{tpidr}, the software thread id register. It is 64 bits in size and has a
48881 type of @samp{data_ptr}.
48884 Both @samp{tpidr} and @samp{tpidr2}.
48888 @samp{tpidr}, the software thread id register. It is 64 bits in size and has a
48889 type of @samp{data_ptr}.
48891 @samp{tpidr2}, the second software thread id register. It is 64 bits in size
48892 and has a type of @samp{data_ptr}. It may be used in the future alongside
48893 the Scalable Matrix Extension for a lazy restore scheme.
48896 If @value{GDBN} sees this feature, it will attempt to find one of the
48897 variations of the register set. If @samp{tpidr2} is available,
48898 @value{GDBN} may act on it to display additional data in the future.
48900 There is no XML for this feature as the presence of @samp{tpidr2} is
48901 determined dynamically at runtime.
48903 Extra registers are allowed in this feature, but they will not affect
48906 @subsubsection AArch64 MTE registers feature
48908 The @samp{org.gnu.gdb.aarch64.mte} optional feature was introduced so
48909 @value{GDBN} could detect support for the Memory Tagging Extension and
48910 control memory tagging settings. If present, this feature must have the
48911 following register:
48915 @samp{tag_ctl}, the tag control register. It is 64 bits in size and has a type
48919 Memory Tagging detection is done via a runtime check though, so the presence
48920 of this feature and register is not enough to enable memory tagging support.
48922 This restriction may be lifted in the future.
48924 Extra registers are allowed in this feature, but they will not affect
48927 @subsubsection AArch64 SME registers feature
48929 The @samp{org.gnu.gdb.aarch64.sme} feature is optional. If present,
48930 it should contain registers @code{ZA}, @code{SVG} and @code{SVCR}.
48931 @xref{AArch64 SME}.
48936 @code{ZA} is a register represented by a vector of @var{svl}x@var{svl}
48940 @code{SVG} is a 64-bit register containing the value of @var{svg}. @xref{svg}.
48943 @code{SVCR} is a 64-bit status pseudo-register with two valid bits. Bit 0
48944 (@sc{sm}) shows whether the streaming @acronym{SVE} mode is enabled or disabled.
48945 Bit 1 (@sc{ZA}) shows whether the @code{ZA} register state is active (in use) or
48947 @xref{aarch64 sme svcr}.
48949 The rest of the unused bits of the @code{SVCR} pseudo-register is undefined
48950 and reserved. Such bits should not be used and may be defined by future
48951 extensions of the architecture.
48955 Extra registers are allowed in this feature, but they will not affect
48958 The @samp{org.gnu.gdb.aarch64.sme} feature is required when the target also
48959 reports support for the @samp{org.gnu.gdb.aarch64.sme2} feature.
48961 @subsubsection AArch64 SME2 registers feature
48963 The @samp{org.gnu.gdb.aarch64.sme2} feature is optional. If present,
48964 then the @samp{org.gnu.gdb.aarch64.sme} feature must also be present. The
48965 @samp{org.gnu.gdb.aarch64.sme2} feature should contain the following:
48966 @xref{AArch64 SME2}.
48971 @code{ZT0} is a register of 512 bits (64 bytes). It is defined as a vector
48976 Extra registers are allowed in this feature, but they will not affect
48980 @subsection ARC Features
48981 @cindex target descriptions, ARC Features
48983 ARC processors are so configurable that even core registers and their numbers
48984 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
48985 registers, which are important to @value{GDBN}, are not ``core'' registers in
48986 ARC. Therefore, there are two features that their presence is mandatory:
48987 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
48989 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
48994 @samp{r0} through @samp{r25} for normal register file targets.
48996 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
48997 register file targets.
48999 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
49000 @samp{blink}, @samp{lp_count}, @samp{pcl}.
49003 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
49004 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
49005 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
49006 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
49007 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
49008 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
49009 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
49010 because of their inaccessibility during user space debugging sessions.
49012 Extension core registers @samp{r32} through @samp{r59} are optional and their
49013 existence depends on the configuration. When debugging GNU/Linux applications,
49014 i.e.@: user space debugging, these core registers are not available.
49016 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
49017 is the list of registers pertinent to this feature:
49021 mandatory: @samp{pc} and @samp{status32}.
49023 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
49027 @subsection ARM Features
49028 @cindex target descriptions, ARM features
49030 @subsubsection Core register set for non-M-profile
49032 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
49033 ARM targets. It must contain the following registers:
49037 @samp{r0} through @samp{r12}. The general purpose registers. They are 32 bits
49038 in size and have a type of @samp{uint32}.
49040 @samp{sp}, the stack pointer register, also known as @samp{r13}. It is 32 bits
49041 in size and has a type of @samp{data_ptr}.
49043 @samp{lr}, the link register. It is 32 bits in size.
49045 @samp{pc}, the program counter register. It is 32 bit in size and of type
49048 @samp{cpsr}, the current program status register containing all the status
49049 bits. It is 32 bits in size. Historically this register was hardwired to
49050 number 25, but debugging stubs that report XML do not need to use this number
49054 Extra registers are allowed in this feature, but they will not affect
49057 @subsubsection Core register set for M-profile
49059 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
49060 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}, and it is a required
49061 feature. It must contain the following registers:
49065 @samp{r0} through @samp{r12}, the general purpose registers. They have a size
49066 of 32 bits and a type of @samp{uint32}.
49068 @samp{sp}, the stack pointer register, also known as @samp{r13}. It has a size
49069 of 32 bits and a type of @samp{data_ptr}.
49071 @samp{lr}, the link register. It has a size of 32 bits.
49073 @samp{pc}, the program counter register. It has a size of 32 bits and a type
49074 of @samp{code_ptr}.
49076 @samp{xpsr}, the program status register containing all the status
49077 bits. It has a size of 32 bits. Historically this register was hardwired to
49078 number 25, but debugging stubs that report XML do not need to use this number
49082 Upon seeing this feature, @value{GDBN} will acknowledge that it is dealing
49083 with an M-profile target. This means @value{GDBN} will use hooks and
49084 configurations that are meaningful to M-profiles.
49086 Extra registers are allowed in this feature, but they will not affect
49089 @subsubsection FPA registers feature (obsolete)
49091 The @samp{org.gnu.gdb.arm.fpa} feature is obsolete and should not be
49092 advertised by debugging stubs anymore. It used to advertise registers for
49093 the old FPA architecture that has long been discontinued in toolchains.
49095 It is kept in @value{GDBN} for backward compatibility purposes so older
49096 debugging stubs that don't support XML target descriptions still work
49097 correctly. One such example is the KGDB debugging stub from
49098 Linux or BSD kernels.
49100 The description below is for historical purposes only. This feature
49101 used to contain the following registers:
49105 @samp{f0} through @samp{f8}. The floating point registers. They are 96 bits
49106 in size and of type @samp{arm_fpa_ext}. @samp{f0} is pinned to register
49109 @samp{fps}, the status register. It has a size of 32 bits.
49112 @subsubsection M-profile Vector Extension (MVE)
49114 Also known as Helium, the M-profile Vector Extension is advertised via the
49115 optional @samp{org.gnu.gdb.arm.m-profile-mve} feature.
49117 It must contain the following:
49121 @samp{vpr}, the vector predication status and control register. It is 32 bits
49122 in size and has a custom flags type. The flags type is laid out in a way that
49123 exposes the @samp{P0} field from bits 0 to 15, the @samp{MASK01} field from
49124 bits 16 to 19 and the @samp{MASK23} field from bits 20 to 23.
49126 Bits 24 through 31 are reserved.
49129 When this feature is available, @value{GDBN} will synthesize the @samp{p0}
49130 pseudo-register from @samp{vpr} contents.
49132 This feature must only be advertised if the target is M-profile. Advertising
49133 this feature for targets that are not M-profile may cause @value{GDBN} to
49134 assume the target is M-profile when it isn't.
49136 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
49137 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
49138 synthesize the @samp{q} pseudo-registers from @samp{d} register
49141 Extra registers are allowed in this feature, but they will not affect
49144 @subsubsection XScale iwMMXt feature
49146 The XScale @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
49147 it must contain the following:
49151 @samp{wR0} through @samp{wR15}, registers with size 64 bits and a custom type
49152 @samp{iwmmxt_vec64i}. @samp{iwmmxt_vec64i} is a union of four other
49153 types: @samp{uint64}, a 2-element vector of @samp{uint32}, a 4-element
49154 vector of @samp{uint16} and a 8-element vector of @samp{uint8}.
49156 @samp{wCGR0} through @samp{wCGR3}, registers with size 32 bits and
49160 The following registers are optional:
49164 @samp{wCID}, register with size of 32 bits and type @samp{int}.
49166 @samp{wCon}, register with size 32 bits and type @samp{int}.
49168 @samp{wCSSF}, register with size 32 bits and type @samp{int}.
49170 @samp{wCASF}, register with size 32 bit and type @samp{int}.
49173 This feature should only be reported if the target is XScale.
49175 Extra registers are allowed in this feature, but they will not affect
49178 @subsubsection Vector Floating-Point (VFP) feature
49180 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
49181 should contain one of two possible sets of values depending on whether
49182 VFP version 2 or VFP version 3 is in use.
49188 @samp{d0} through @samp{d15}. The double-precision registers. They are
49189 64 bits in size and have type @samp{ieee_double}.
49191 @samp{fpscr}, the floating-point status and control register. It has a size
49192 of 32 bits and a type of @samp{int}.
49199 @samp{d0} through @samp{d31}. The double-precision registers. They are
49200 64 bits in size and have type @samp{ieee_double}.
49202 @samp{fpscr}, the floating-point status and control register. It has a size
49203 of 32 bits and a type of @samp{int}.
49206 If this feature is available, @value{GDBN} will synthesize the
49207 single-precision floating-point registers from halves of the double-precision
49208 registers as pseudo-registers.
49210 Extra registers are allowed in this feature, but they will not affect
49213 @subsubsection NEON architecture feature
49215 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
49216 need to contain registers; it instructs @value{GDBN} to display the
49217 VFP double-precision registers as vectors and to synthesize the
49218 quad-precision registers from pairs of double-precision registers.
49219 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
49220 be present and include 32 double-precision registers.
49222 Extra registers are allowed in this feature, but they will not affect
49225 @subsubsection M-profile Pointer Authentication and Branch Target Identification feature
49227 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
49228 acknowledges support for the ARMv8.1-m PACBTI extensions.
49230 This feature doesn't contain any required registers, and it only serves as a
49231 hint to @value{GDBN} that the debugging stub supports the ARMv8.1-m PACBTI
49234 When @value{GDBN} sees this feature, it will track return address signing
49235 states and will decorate backtraces using the [PAC] marker, similar to
49236 AArch64's PAC extension.
49237 @xref{AArch64 PAC}.
49239 Extra registers are allowed in this feature, but they will not affect
49242 @subsubsection M-profile system registers feature
49244 The @samp{org.gnu.gdb.arm.m-system} optional feature was introduced as a way to
49245 inform @value{GDBN} about additional system registers.
49247 At the moment this feature must contain the following:
49251 @samp{msp}, the main stack pointer register. It is 32 bits in size with
49252 type @samp{data_ptr}.
49254 @samp{psp}, the process stack pointer register. It is 32 bits in size with
49255 type @samp{data_ptr}.
49258 This feature must only be advertised for M-profile targets. When @value{GDBN}
49259 sees this feature, it will attempt to track the values of @samp{msp} and
49260 @samp{psp} across frames.
49262 Extra registers are allowed in this feature, but they will not affect
49265 @subsubsection M-profile Security Extensions feature
49267 The @samp{org.gnu.gdb.arm.secext} optional feature was introduced so
49268 @value{GDBN} could better support the switching of stack pointers and
49269 secure states in the Security Extensions.
49271 At the moment this feature must contain the following:
49275 @samp{msp_ns}, the main stack pointer register (non-secure state). It is
49276 32 bits in size with type @samp{data_ptr}.
49278 @samp{psp_ns}, the process stack pointer register (non-secure state). It is
49279 32 bits in size with type @samp{data_ptr}.
49281 @samp{msp_s}, the main stack pointer register (secure state). It is 32 bits
49282 in size with type @samp{data_ptr}.
49284 @samp{psp_s}, the process stack pointer register (secure state). It is 32 bits
49285 in size with type @samp{data_ptr}.
49288 When @value{GDBN} sees this feature, it will attempt to track the values of
49289 all 4 stack pointers across secure state transitions, potentially improving
49290 unwinding when applications switch between security states.
49292 Extra registers are allowed in this feature, but they will not affect
49295 @subsubsection TLS registers feature
49297 The optional @samp{org.gnu.gdb.arm.tls} feature contains TLS registers.
49299 Currently it contains the following:
49303 @samp{tpidruro}, the user read-only thread id register. It is 32 bits in size
49304 and has type @samp{data_ptr}.
49307 At the moment @value{GDBN} looks for this feature, but doesn't do anything
49308 with it other than displaying it.
49310 Extra registers are allowed in this feature, but they will not affect
49313 @node i386 Features
49314 @subsection i386 Features
49315 @cindex target descriptions, i386 features
49317 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
49318 targets. It should describe the following registers:
49322 @samp{eax} through @samp{edi} plus @samp{eip} for i386
49324 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
49326 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
49327 @samp{fs}, @samp{gs}
49329 @samp{st0} through @samp{st7}
49331 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
49332 @samp{foseg}, @samp{fooff} and @samp{fop}
49335 The register sets may be different, depending on the target.
49337 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
49338 describe registers:
49342 @samp{xmm0} through @samp{xmm7} for i386
49344 @samp{xmm0} through @samp{xmm15} for amd64
49349 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
49350 @samp{org.gnu.gdb.i386.sse} feature. It should
49351 describe the upper 128 bits of @sc{ymm} registers:
49355 @samp{ymm0h} through @samp{ymm7h} for i386
49357 @samp{ymm0h} through @samp{ymm15h} for amd64
49360 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
49361 Memory Protection Extension (MPX). It should describe the following registers:
49365 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
49367 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
49370 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
49371 describe a single register, @samp{orig_eax}.
49373 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
49374 describe two system registers: @samp{fs_base} and @samp{gs_base}.
49376 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
49377 @samp{org.gnu.gdb.i386.avx} feature. It should
49378 describe additional @sc{xmm} registers:
49382 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
49385 It should describe the upper 128 bits of additional @sc{ymm} registers:
49389 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
49393 describe the upper 256 bits of @sc{zmm} registers:
49397 @samp{zmm0h} through @samp{zmm7h} for i386.
49399 @samp{zmm0h} through @samp{zmm15h} for amd64.
49403 describe the additional @sc{zmm} registers:
49407 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
49410 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
49411 describe a single register, @samp{pkru}. It is a 32-bit register
49412 valid for i386 and amd64.
49414 @node LoongArch Features
49415 @subsection LoongArch Features
49416 @cindex target descriptions, LoongArch Features
49418 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
49419 targets. It should contain the registers @samp{r0} through @samp{r31},
49420 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
49421 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
49423 The @samp{org.gnu.gdb.loongarch.fpu} feature is optional. If present,
49424 it should contain registers @samp{f0} through @samp{f31}, @samp{fcc},
49427 @node MicroBlaze Features
49428 @subsection MicroBlaze Features
49429 @cindex target descriptions, MicroBlaze features
49431 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
49432 targets. It should contain registers @samp{r0} through @samp{r31},
49433 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
49434 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
49435 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
49437 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
49438 If present, it should contain registers @samp{rshr} and @samp{rslr}
49440 @node MIPS Features
49441 @subsection @acronym{MIPS} Features
49442 @cindex target descriptions, @acronym{MIPS} features
49444 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
49445 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
49446 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
49449 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
49450 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
49451 registers. They may be 32-bit or 64-bit depending on the target.
49453 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
49454 it may be optional in a future version of @value{GDBN}. It should
49455 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
49456 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
49458 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
49459 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
49460 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
49461 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
49463 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
49464 contain a single register, @samp{restart}, which is used by the
49465 Linux kernel to control restartable syscalls.
49467 @node M68K Features
49468 @subsection M68K Features
49469 @cindex target descriptions, M68K features
49472 @item @samp{org.gnu.gdb.m68k.core}
49473 @itemx @samp{org.gnu.gdb.coldfire.core}
49474 @itemx @samp{org.gnu.gdb.fido.core}
49475 One of those features must be always present.
49476 The feature that is present determines which flavor of m68k is
49477 used. The feature that is present should contain registers
49478 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
49479 @samp{sp}, @samp{ps} and @samp{pc}.
49481 @item @samp{org.gnu.gdb.coldfire.fp}
49482 This feature is optional. If present, it should contain registers
49483 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
49486 Note that, despite the fact that this feature's name says
49487 @samp{coldfire}, it is used to describe any floating point registers.
49488 The size of the registers must match the main m68k flavor; so, for
49489 example, if the primary feature is reported as @samp{coldfire}, then
49490 64-bit floating point registers are required.
49493 @node NDS32 Features
49494 @subsection NDS32 Features
49495 @cindex target descriptions, NDS32 features
49497 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
49498 targets. It should contain at least registers @samp{r0} through
49499 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
49502 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
49503 it should contain 64-bit double-precision floating-point registers
49504 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
49505 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
49507 @emph{Note:} The first sixteen 64-bit double-precision floating-point
49508 registers are overlapped with the thirty-two 32-bit single-precision
49509 floating-point registers. The 32-bit single-precision registers, if
49510 not being listed explicitly, will be synthesized from halves of the
49511 overlapping 64-bit double-precision registers. Listing 32-bit
49512 single-precision registers explicitly is deprecated, and the
49513 support to it could be totally removed some day.
49515 @node Nios II Features
49516 @subsection Nios II Features
49517 @cindex target descriptions, Nios II features
49519 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
49520 targets. It should contain the 32 core registers (@samp{zero},
49521 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
49522 @samp{pc}, and the 16 control registers (@samp{status} through
49525 @node OpenRISC 1000 Features
49526 @subsection Openrisc 1000 Features
49527 @cindex target descriptions, OpenRISC 1000 features
49529 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
49530 targets. It should contain the 32 general purpose registers (@samp{r0}
49531 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
49533 @node PowerPC Features
49534 @subsection PowerPC Features
49535 @cindex target descriptions, PowerPC features
49537 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
49538 targets. It should contain registers @samp{r0} through @samp{r31},
49539 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
49540 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
49542 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
49543 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
49545 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
49546 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
49547 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
49548 through @samp{v31} as aliases for the corresponding @samp{vrX}
49551 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
49552 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
49553 combine these registers with the floating point registers (@samp{f0}
49554 through @samp{f31}) and the altivec registers (@samp{vr0} through
49555 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
49556 @samp{vs63}, the set of vector-scalar registers for POWER7.
49557 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
49558 @samp{org.gnu.gdb.power.altivec}.
49560 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
49561 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
49562 @samp{spefscr}. SPE targets should provide 32-bit registers in
49563 @samp{org.gnu.gdb.power.core} and provide the upper halves in
49564 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
49565 these to present registers @samp{ev0} through @samp{ev31} to the
49568 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
49569 contain the 64-bit register @samp{ppr}.
49571 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
49572 contain the 64-bit register @samp{dscr}.
49574 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
49575 contain the 64-bit register @samp{tar}.
49577 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
49578 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
49581 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
49582 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
49583 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
49584 server PMU registers provided by @sc{gnu}/Linux.
49586 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
49587 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
49590 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
49591 contain the checkpointed general-purpose registers @samp{cr0} through
49592 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
49593 @samp{cctr}. These registers may all be either 32-bit or 64-bit
49594 depending on the target. It should also contain the checkpointed
49595 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
49598 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
49599 contain the checkpointed 64-bit floating-point registers @samp{cf0}
49600 through @samp{cf31}, as well as the checkpointed 64-bit register
49603 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
49604 should contain the checkpointed altivec registers @samp{cvr0} through
49605 @samp{cvr31}, all 128-bit wide. It should also contain the
49606 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
49609 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
49610 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
49611 will combine these registers with the checkpointed floating point
49612 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
49613 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
49614 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
49615 @samp{cvs63}. Therefore, this feature requires both
49616 @samp{org.gnu.gdb.power.htm.altivec} and
49617 @samp{org.gnu.gdb.power.htm.fpu}.
49619 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
49620 contain the 64-bit checkpointed register @samp{cppr}.
49622 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
49623 contain the 64-bit checkpointed register @samp{cdscr}.
49625 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
49626 contain the 64-bit checkpointed register @samp{ctar}.
49629 @node RISC-V Features
49630 @subsection RISC-V Features
49631 @cindex target descriptions, RISC-V Features
49633 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
49634 targets. It should contain the registers @samp{x0} through
49635 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
49636 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
49639 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
49640 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
49641 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
49642 architectural register names, or the ABI names can be used.
49644 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
49645 it should contain registers that are not backed by real registers on
49646 the target, but are instead virtual, where the register value is
49647 derived from other target state. In many ways these are like
49648 @value{GDBN}s pseudo-registers, except implemented by the target.
49649 Currently the only register expected in this set is the one byte
49650 @samp{priv} register that contains the target's privilege level in the
49651 least significant two bits.
49653 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
49654 should contain all of the target's standard CSRs. Standard CSRs are
49655 those defined in the RISC-V specification documents. There is some
49656 overlap between this feature and the fpu feature; the @samp{fflags},
49657 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
49658 expectation is that these registers will be in the fpu feature if the
49659 target has floating point hardware, but can be moved into the csr
49660 feature if the target has the floating point control registers, but no
49661 other floating point hardware.
49663 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
49664 it should contain registers @samp{v0} through @samp{v31}, all of which
49665 must be the same size.
49668 @subsection RX Features
49669 @cindex target descriptions, RX Features
49671 The @samp{org.gnu.gdb.rx.core} feature is required for RX
49672 targets. It should contain the registers @samp{r0} through
49673 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
49674 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
49676 @node S/390 and System z Features
49677 @subsection S/390 and System z Features
49678 @cindex target descriptions, S/390 features
49679 @cindex target descriptions, System z features
49681 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
49682 System z targets. It should contain the PSW and the 16 general
49683 registers. In particular, System z targets should provide the 64-bit
49684 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
49685 S/390 targets should provide the 32-bit versions of these registers.
49686 A System z target that runs in 31-bit addressing mode should provide
49687 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
49688 register's upper halves @samp{r0h} through @samp{r15h}, and their
49689 lower halves @samp{r0l} through @samp{r15l}.
49691 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
49692 contain the 64-bit registers @samp{f0} through @samp{f15}, and
49695 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
49696 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
49698 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
49699 contain the register @samp{orig_r2}, which is 64-bit wide on System z
49700 targets and 32-bit otherwise. In addition, the feature may contain
49701 the @samp{last_break} register, whose width depends on the addressing
49702 mode, as well as the @samp{system_call} register, which is always
49705 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
49706 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
49707 @samp{atia}, and @samp{tr0} through @samp{tr15}.
49709 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
49710 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
49711 combined by @value{GDBN} with the floating point registers @samp{f0}
49712 through @samp{f15} to present the 128-bit wide vector registers
49713 @samp{v0} through @samp{v15}. In addition, this feature should
49714 contain the 128-bit wide vector registers @samp{v16} through
49717 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
49718 the 64-bit wide guarded-storage-control registers @samp{gsd},
49719 @samp{gssm}, and @samp{gsepla}.
49721 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
49722 the 64-bit wide guarded-storage broadcast control registers
49723 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
49725 @node Sparc Features
49726 @subsection Sparc Features
49727 @cindex target descriptions, sparc32 features
49728 @cindex target descriptions, sparc64 features
49729 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
49730 targets. It should describe the following registers:
49734 @samp{g0} through @samp{g7}
49736 @samp{o0} through @samp{o7}
49738 @samp{l0} through @samp{l7}
49740 @samp{i0} through @samp{i7}
49743 They may be 32-bit or 64-bit depending on the target.
49745 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
49746 targets. It should describe the following registers:
49750 @samp{f0} through @samp{f31}
49752 @samp{f32} through @samp{f62} for sparc64
49755 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
49756 targets. It should describe the following registers:
49760 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
49761 @samp{fsr}, and @samp{csr} for sparc32
49763 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
49767 @node TIC6x Features
49768 @subsection TMS320C6x Features
49769 @cindex target descriptions, TIC6x features
49770 @cindex target descriptions, TMS320C6x features
49771 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
49772 targets. It should contain registers @samp{A0} through @samp{A15},
49773 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
49775 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
49776 contain registers @samp{A16} through @samp{A31} and @samp{B16}
49777 through @samp{B31}.
49779 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
49780 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
49782 @node Operating System Information
49783 @appendix Operating System Information
49784 @cindex operating system information
49786 Users of @value{GDBN} often wish to obtain information about the state of
49787 the operating system running on the target---for example the list of
49788 processes, or the list of open files. This section describes the
49789 mechanism that makes it possible. This mechanism is similar to the
49790 target features mechanism (@pxref{Target Descriptions}), but focuses
49791 on a different aspect of target.
49793 Operating system information is retrieved from the target via the
49794 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
49795 read}). The object name in the request should be @samp{osdata}, and
49796 the @var{annex} identifies the data to be fetched.
49803 @appendixsection Process list
49804 @cindex operating system information, process list
49806 When requesting the process list, the @var{annex} field in the
49807 @samp{qXfer} request should be @samp{processes}. The returned data is
49808 an XML document. The formal syntax of this document is defined in
49809 @file{gdb/features/osdata.dtd}.
49811 An example document is:
49814 <?xml version="1.0"?>
49815 <!DOCTYPE target SYSTEM "osdata.dtd">
49816 <osdata type="processes">
49818 <column name="pid">1</column>
49819 <column name="user">root</column>
49820 <column name="command">/sbin/init</column>
49821 <column name="cores">1,2,3</column>
49826 Each item should include a column whose name is @samp{pid}. The value
49827 of that column should identify the process on the target. The
49828 @samp{user} and @samp{command} columns are optional, and will be
49829 displayed by @value{GDBN}. The @samp{cores} column, if present,
49830 should contain a comma-separated list of cores that this process
49831 is running on. Target may provide additional columns,
49832 which @value{GDBN} currently ignores.
49834 @node Trace File Format
49835 @appendix Trace File Format
49836 @cindex trace file format
49838 The trace file comes in three parts: a header, a textual description
49839 section, and a trace frame section with binary data.
49841 The header has the form @code{\x7fTRACE0\n}. The first byte is
49842 @code{0x7f} so as to indicate that the file contains binary data,
49843 while the @code{0} is a version number that may have different values
49846 The description section consists of multiple lines of @sc{ascii} text
49847 separated by newline characters (@code{0xa}). The lines may include a
49848 variety of optional descriptive or context-setting information, such
49849 as tracepoint definitions or register set size. @value{GDBN} will
49850 ignore any line that it does not recognize. An empty line marks the end
49855 Specifies the size of a register block in bytes. This is equal to the
49856 size of a @code{g} packet payload in the remote protocol. @var{size}
49857 is an ascii decimal number. There should be only one such line in
49858 a single trace file.
49860 @item status @var{status}
49861 Trace status. @var{status} has the same format as a @code{qTStatus}
49862 remote packet reply. There should be only one such line in a single trace
49865 @item tp @var{payload}
49866 Tracepoint definition. The @var{payload} has the same format as
49867 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
49868 may take multiple lines of definition, corresponding to the multiple
49871 @item tsv @var{payload}
49872 Trace state variable definition. The @var{payload} has the same format as
49873 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
49874 may take multiple lines of definition, corresponding to the multiple
49877 @item tdesc @var{payload}
49878 Target description in XML format. The @var{payload} is a single line of
49879 the XML file. All such lines should be concatenated together to get
49880 the original XML file. This file is in the same format as @code{qXfer}
49881 @code{features} payload, and corresponds to the main @code{target.xml}
49882 file. Includes are not allowed.
49886 The trace frame section consists of a number of consecutive frames.
49887 Each frame begins with a two-byte tracepoint number, followed by a
49888 four-byte size giving the amount of data in the frame. The data in
49889 the frame consists of a number of blocks, each introduced by a
49890 character indicating its type (at least register, memory, and trace
49891 state variable). The data in this section is raw binary, not a
49892 hexadecimal or other encoding; its endianness matches the target's
49895 @c FIXME bi-arch may require endianness/arch info in description section
49898 @item R @var{bytes}
49899 Register block. The number and ordering of bytes matches that of a
49900 @code{g} packet in the remote protocol. Note that these are the
49901 actual bytes, in target order, not a hexadecimal encoding.
49903 @item M @var{address} @var{length} @var{bytes}...
49904 Memory block. This is a contiguous block of memory, at the 8-byte
49905 address @var{address}, with a 2-byte length @var{length}, followed by
49906 @var{length} bytes.
49908 @item V @var{number} @var{value}
49909 Trace state variable block. This records the 8-byte signed value
49910 @var{value} of trace state variable numbered @var{number}.
49914 Future enhancements of the trace file format may include additional types
49917 @node Index Section Format
49918 @appendix @code{.gdb_index} section format
49919 @cindex .gdb_index section format
49920 @cindex index section format
49922 This section documents the index section that is created by @code{save
49923 gdb-index} (@pxref{Index Files}). The index section is
49924 DWARF-specific; some knowledge of DWARF is assumed in this
49927 The mapped index file format is designed to be directly
49928 @code{mmap}able on any architecture. In most cases, a datum is
49929 represented using a little-endian 32-bit integer value, called an
49930 @code{offset_type}. Big endian machines must byte-swap the values
49931 before using them. Exceptions to this rule are noted. The data is
49932 laid out such that alignment is always respected.
49934 A mapped index consists of several areas, laid out in order.
49938 The file header. This is a sequence of values, of @code{offset_type}
49939 unless otherwise noted:
49943 The version number, currently 9. Versions 1, 2 and 3 are obsolete.
49944 Version 4 uses a different hashing function from versions 5 and 6.
49945 Version 6 includes symbols for inlined functions, whereas versions 4
49946 and 5 do not. Version 7 adds attributes to the CU indices in the
49947 symbol table. Version 8 specifies that symbols from DWARF type units
49948 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
49949 compilation unit (@samp{DW_TAG_comp_unit}) using the type. Version 9 adds
49950 the name and the language of the main function to the index.
49952 @value{GDBN} will only read version 4, 5, or 6 indices
49953 by specifying @code{set use-deprecated-index-sections on}.
49954 GDB has a workaround for potentially broken version 7 indices so it is
49955 currently not flagged as deprecated.
49958 The offset, from the start of the file, of the CU list.
49961 The offset, from the start of the file, of the types CU list. Note
49962 that this area can be empty, in which case this offset will be equal
49963 to the next offset.
49966 The offset, from the start of the file, of the address area.
49969 The offset, from the start of the file, of the symbol table.
49972 The offset, from the start of the file, of the shortcut table.
49975 The offset, from the start of the file, of the constant pool.
49979 The CU list. This is a sequence of pairs of 64-bit little-endian
49980 values, sorted by the CU offset. The first element in each pair is
49981 the offset of a CU in the @code{.debug_info} section. The second
49982 element in each pair is the length of that CU. References to a CU
49983 elsewhere in the map are done using a CU index, which is just the
49984 0-based index into this table. Note that if there are type CUs, then
49985 conceptually CUs and type CUs form a single list for the purposes of
49989 The types CU list. This is a sequence of triplets of 64-bit
49990 little-endian values. In a triplet, the first value is the CU offset,
49991 the second value is the type offset in the CU, and the third value is
49992 the type signature. The types CU list is not sorted.
49995 The address area. The address area consists of a sequence of address
49996 entries. Each address entry has three elements:
50000 The low address. This is a 64-bit little-endian value.
50003 The high address. This is a 64-bit little-endian value. Like
50004 @code{DW_AT_high_pc}, the value is one byte beyond the end.
50007 The CU index. This is an @code{offset_type} value.
50011 The symbol table. This is an open-addressed hash table. The size of
50012 the hash table is always a power of 2.
50014 Each slot in the hash table consists of a pair of @code{offset_type}
50015 values. The first value is the offset of the symbol's name in the
50016 constant pool. The second value is the offset of the CU vector in the
50019 If both values are 0, then this slot in the hash table is empty. This
50020 is ok because while 0 is a valid constant pool index, it cannot be a
50021 valid index for both a string and a CU vector.
50023 The hash value for a table entry is computed by applying an
50024 iterative hash function to the symbol's name. Starting with an
50025 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
50026 the string is incorporated into the hash using the formula depending on the
50031 The formula is @code{r = r * 67 + c - 113}.
50033 @item Versions 5 to 7
50034 The formula is @code{r = r * 67 + tolower (c) - 113}.
50037 The terminating @samp{\0} is not incorporated into the hash.
50039 The step size used in the hash table is computed via
50040 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
50041 value, and @samp{size} is the size of the hash table. The step size
50042 is used to find the next candidate slot when handling a hash
50045 The names of C@t{++} symbols in the hash table are canonicalized. We
50046 don't currently have a simple description of the canonicalization
50047 algorithm; if you intend to create new index sections, you must read
50050 @item The shortcut table
50051 This is a data structure with the following fields:
50054 @item Language of main
50055 An @code{offset_type} value indicating the language of the main function as a
50056 @code{DW_LANG_} constant. This value will be zero if main function information
50060 An @code{offset_type} value indicating the offset of the main function's name
50061 in the constant pool. This value must be ignored if the value for the language
50066 The constant pool. This is simply a bunch of bytes. It is organized
50067 so that alignment is correct: CU vectors are stored first, followed by
50070 A CU vector in the constant pool is a sequence of @code{offset_type}
50071 values. The first value is the number of CU indices in the vector.
50072 Each subsequent value is the index and symbol attributes of a CU in
50073 the CU list. This element in the hash table is used to indicate which
50074 CUs define the symbol and how the symbol is used.
50075 See below for the format of each CU index+attributes entry.
50077 A string in the constant pool is zero-terminated.
50080 Attributes were added to CU index values in @code{.gdb_index} version 7.
50081 If a symbol has multiple uses within a CU then there is one
50082 CU index+attributes value for each use.
50084 The format of each CU index+attributes entry is as follows
50090 This is the index of the CU in the CU list.
50092 These bits are reserved for future purposes and must be zero.
50094 The kind of the symbol in the CU.
50098 This value is reserved and should not be used.
50099 By reserving zero the full @code{offset_type} value is backwards compatible
50100 with previous versions of the index.
50102 The symbol is a type.
50104 The symbol is a variable or an enum value.
50106 The symbol is a function.
50108 Any other kind of symbol.
50110 These values are reserved.
50114 This bit is zero if the value is global and one if it is static.
50116 The determination of whether a symbol is global or static is complicated.
50117 The authorative reference is the file @file{dwarf2read.c} in
50118 @value{GDBN} sources.
50122 This pseudo-code describes the computation of a symbol's kind and
50123 global/static attributes in the index.
50126 is_external = get_attribute (die, DW_AT_external);
50127 language = get_attribute (cu_die, DW_AT_language);
50130 case DW_TAG_typedef:
50131 case DW_TAG_base_type:
50132 case DW_TAG_subrange_type:
50136 case DW_TAG_enumerator:
50138 is_static = language != CPLUS;
50140 case DW_TAG_subprogram:
50142 is_static = ! (is_external || language == ADA);
50144 case DW_TAG_constant:
50146 is_static = ! is_external;
50148 case DW_TAG_variable:
50150 is_static = ! is_external;
50152 case DW_TAG_namespace:
50156 case DW_TAG_class_type:
50157 case DW_TAG_interface_type:
50158 case DW_TAG_structure_type:
50159 case DW_TAG_union_type:
50160 case DW_TAG_enumeration_type:
50162 is_static = language != CPLUS;
50170 @appendix Download debugging resources with Debuginfod
50173 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
50176 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
50177 can query servers using the build IDs associated with missing debug info,
50178 executables and source files in order to download them on demand.
50180 For instructions on building @value{GDBN} with @file{libdebuginfod},
50181 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
50182 with @code{elfutils}, starting with version 0.178. See
50183 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
50184 regarding @code{debuginfod}.
50187 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
50190 @node Debuginfod Settings
50191 @section Debuginfod Settings
50193 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
50196 @kindex set debuginfod enabled
50197 @anchor{set debuginfod enabled}
50198 @item set debuginfod enabled
50199 @itemx set debuginfod enabled on
50200 @cindex enable debuginfod
50201 @value{GDBN} may query @code{debuginfod} servers for missing debug info and
50202 source files. @value{GDBN} may also download individual ELF/DWARF sections
50203 such as @code{.gdb_index} to help reduce the total amount of data downloaded
50204 from @code{debuginfod} servers; this can be controlled by @w{@code{maint
50205 set debuginfod download-sections}} (@pxref{Maintenance Commands, maint set
50206 debuginfod download-sections}).
50208 @item set debuginfod enabled off
50209 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
50210 debug info or source files. By default, @code{debuginfod enabled} is set to
50211 @code{off} for non-interactive sessions.
50213 @item set debuginfod enabled ask
50214 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
50215 attempting to perform the next query. By default, @code{debuginfod enabled}
50216 is set to @code{ask} for interactive sessions.
50218 @kindex show debuginfod enabled
50219 @item show debuginfod enabled
50220 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
50223 @kindex set debuginfod urls
50224 @cindex configure debuginfod URLs
50225 @item set debuginfod urls
50226 @itemx set debuginfod urls @var{urls}
50227 Set the space-separated list of URLs that @code{debuginfod} will attempt to
50228 query. Only @code{http://}, @code{https://} and @code{file://} protocols
50229 should be used. The default value of @code{debuginfod urls} is copied from
50230 the @var{DEBUGINFOD_URLS} environment variable.
50232 @kindex show debuginfod urls
50233 @item show debuginfod urls
50234 Display the list of URLs that @code{debuginfod} will attempt to query.
50236 @kindex set debuginfod verbose
50237 @cindex debuginfod verbosity
50238 @item set debuginfod verbose
50239 @itemx set debuginfod verbose @var{n}
50240 Enable or disable @code{debuginfod}-related output. Use a non-zero value
50241 to enable and @code{0} to disable. @code{debuginfod} output is shown by
50244 @kindex show debuginfod verbose
50245 @item show debuginfod verbose
50246 Show the current verbosity setting.
50251 @appendix Manual pages
50255 * gdb man:: The GNU Debugger man page
50256 * gdbserver man:: Remote Server for the GNU Debugger man page
50257 * gcore man:: Generate a core file of a running program
50258 * gdbinit man:: gdbinit scripts
50259 * gdb-add-index man:: Add index files to speed up GDB
50265 @c man title gdb The GNU Debugger
50267 @c man begin SYNOPSIS gdb
50268 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
50271 @c man begin DESCRIPTION gdb
50272 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
50273 going on ``inside'' another program while it executes -- or what another
50274 program was doing at the moment it crashed.
50276 @value{GDBN} can do four main kinds of things (plus other things in support of
50277 these) to help you catch bugs in the act:
50281 Start your program, specifying anything that might affect its behavior.
50284 Make your program stop on specified conditions.
50287 Examine what has happened, when your program has stopped.
50290 Change things in your program, so you can experiment with correcting the
50291 effects of one bug and go on to learn about another.
50294 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
50297 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
50298 commands from the terminal until you tell it to exit with the @value{GDBN}
50299 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
50300 by using the command @code{help}.
50302 You can run @code{gdb} with no arguments or options; but the most
50303 usual way to start @value{GDBN} is with one argument or two, specifying an
50304 executable program as the argument:
50310 You can also start with both an executable program and a core file specified:
50316 You can, instead, specify a process ID as a second argument or use option
50317 @code{-p}, if you want to debug a running process:
50325 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
50326 can omit the @var{program} filename.
50328 Here are some of the most frequently needed @value{GDBN} commands:
50330 @c pod2man highlights the right hand side of the @item lines.
50332 @item break [@var{file}:][@var{function}|@var{line}]
50333 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
50335 @item run [@var{arglist}]
50336 Start your program (with @var{arglist}, if specified).
50339 Backtrace: display the program stack.
50341 @item print @var{expr}
50342 Display the value of an expression.
50345 Continue running your program (after stopping, e.g.@: at a breakpoint).
50348 Execute next program line (after stopping); step @emph{over} any
50349 function calls in the line.
50351 @item edit [@var{file}:]@var{function}
50352 look at the program line where it is presently stopped.
50354 @item list [@var{file}:]@var{function}
50355 type the text of the program in the vicinity of where it is presently stopped.
50358 Execute next program line (after stopping); step @emph{into} any
50359 function calls in the line.
50361 @item help [@var{name}]
50362 Show information about @value{GDBN} command @var{name}, or general information
50363 about using @value{GDBN}.
50367 Exit from @value{GDBN}.
50371 For full details on @value{GDBN},
50372 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
50373 by Richard M. Stallman and Roland H. Pesch. The same text is available online
50374 as the @code{gdb} entry in the @code{info} program.
50378 @c man begin OPTIONS gdb
50379 Any arguments other than options specify an executable
50380 file and core file (or process ID); that is, the first argument
50381 encountered with no
50382 associated option flag is equivalent to a @option{--se} option, and the second,
50383 if any, is equivalent to a @option{-c} option if it's the name of a file.
50385 both long and abbreviated forms; both are shown here. The long forms are also
50386 recognized if you truncate them, so long as enough of the option is
50387 present to be unambiguous.
50389 The abbreviated forms are shown here with @samp{-} and long forms are shown
50390 with @samp{--} to reflect how they are shown in @option{--help}. However,
50391 @value{GDBN} recognizes all of the following conventions for most options:
50394 @item --option=@var{value}
50395 @item --option @var{value}
50396 @item -option=@var{value}
50397 @item -option @var{value}
50398 @item --o=@var{value}
50399 @item --o @var{value}
50400 @item -o=@var{value}
50401 @item -o @var{value}
50404 All the options and command line arguments you give are processed
50405 in sequential order. The order makes a difference when the @option{-x}
50411 List all options, with brief explanations.
50413 @item --symbols=@var{file}
50414 @itemx -s @var{file}
50415 Read symbol table from @var{file}.
50418 Enable writing into executable and core files.
50420 @item --exec=@var{file}
50421 @itemx -e @var{file}
50422 Use @var{file} as the executable file to execute when
50423 appropriate, and for examining pure data in conjunction with a core
50426 @item --se=@var{file}
50427 Read symbol table from @var{file} and use it as the executable
50430 @item --core=@var{file}
50431 @itemx -c @var{file}
50432 Use @var{file} as a core dump to examine.
50434 @item --command=@var{file}
50435 @itemx -x @var{file}
50436 Execute @value{GDBN} commands from @var{file}.
50438 @item --eval-command=@var{command}
50439 @item -ex @var{command}
50440 Execute given @value{GDBN} @var{command}.
50442 @item --init-eval-command=@var{command}
50444 Execute @value{GDBN} @var{command} before loading the inferior.
50446 @item --directory=@var{directory}
50447 @itemx -d @var{directory}
50448 Add @var{directory} to the path to search for source files.
50451 Do not execute commands from @file{~/.config/gdb/gdbinit},
50452 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
50453 @file{~/.gdbearlyinit}
50457 Do not execute commands from any @file{.gdbinit} or
50458 @file{.gdbearlyinit} initialization files.
50463 ``Quiet''. Do not print the introductory and copyright messages. These
50464 messages are also suppressed in batch mode.
50467 Run in batch mode. Exit with status @code{0} after processing all the command
50468 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
50469 Exit with nonzero status if an error occurs in executing the @value{GDBN}
50470 commands in the command files.
50472 Batch mode may be useful for running @value{GDBN} as a filter, for example to
50473 download and run a program on another computer; in order to make this
50474 more useful, the message
50477 Program exited normally.
50481 (which is ordinarily issued whenever a program running under @value{GDBN} control
50482 terminates) is not issued when running in batch mode.
50484 @item --batch-silent
50485 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
50486 output is suppressed (stderr is unaffected). This is much quieter than
50487 @option{--silent} and would be useless for an interactive session.
50489 This is particularly useful when using targets that give @samp{Loading section}
50490 messages, for example.
50492 Note that targets that give their output via @value{GDBN}, as opposed to writing
50493 directly to @code{stdout}, will also be made silent.
50495 @item --args @var{prog} [@var{arglist}]
50496 Change interpretation of command line so that arguments following this
50497 option are passed as arguments to the inferior. As an example, take
50498 the following command:
50505 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
50506 the other hand, using:
50509 gdb --args ./a.out -q
50513 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
50515 @item --pid=@var{pid}
50516 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
50519 Open the terminal user interface.
50522 Read all symbols from the given symfile on the first access.
50525 Do not read symbol files.
50527 @item --return-child-result
50528 @value{GDBN}'s exit code will be the same as the child's exit code.
50530 @item --configuration
50531 Print details about GDB configuration and then exit.
50534 Print version information and then exit.
50536 @item --cd=@var{directory}
50537 Run @value{GDBN} using @var{directory} as its working directory,
50538 instead of the current directory.
50540 @item --data-directory=@var{directory}
50542 Run @value{GDBN} using @var{directory} as its data directory. The data
50543 directory is where @value{GDBN} searches for its auxiliary files.
50547 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
50548 @value{GDBN} to output the full file name and line number in a standard,
50549 recognizable fashion each time a stack frame is displayed (which
50550 includes each time the program stops). This recognizable format looks
50551 like two @samp{\032} characters, followed by the file name, line number
50552 and character position separated by colons, and a newline. The
50553 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
50554 characters as a signal to display the source code for the frame.
50556 @item -b @var{baudrate}
50557 Set the line speed (baud rate or bits per second) of any serial
50558 interface used by @value{GDBN} for remote debugging.
50560 @item -l @var{timeout}
50561 Set timeout, in seconds, for remote debugging.
50563 @item --tty=@var{device}
50564 Run using @var{device} for your program's standard input and output.
50568 @c man begin SEEALSO gdb
50570 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
50571 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
50572 documentation are properly installed at your site, the command
50579 should give you access to the complete manual.
50581 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
50582 Richard M. Stallman and Roland H. Pesch, July 1991.
50586 @node gdbserver man
50587 @heading gdbserver man
50589 @c man title gdbserver Remote Server for the GNU Debugger
50591 @c man begin SYNOPSIS gdbserver
50592 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
50594 gdbserver --attach @var{comm} @var{pid}
50596 gdbserver --multi @var{comm}
50600 @c man begin DESCRIPTION gdbserver
50601 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
50602 than the one which is running the program being debugged.
50605 @subheading Usage (server (target) side)
50608 Usage (server (target) side):
50611 First, you need to have a copy of the program you want to debug put onto
50612 the target system. The program can be stripped to save space if needed, as
50613 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
50614 the @value{GDBN} running on the host system.
50616 To use the server, you log on to the target system, and run the @command{gdbserver}
50617 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
50618 your program, and (c) its arguments. The general syntax is:
50621 target> gdbserver @var{comm} @var{program} [@var{args} ...]
50624 For example, using a serial port, you might say:
50628 @c @file would wrap it as F</dev/com1>.
50629 target> gdbserver /dev/com1 emacs foo.txt
50632 target> gdbserver @file{/dev/com1} emacs foo.txt
50636 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
50637 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
50638 waits patiently for the host @value{GDBN} to communicate with it.
50640 To use a TCP connection, you could say:
50643 target> gdbserver host:2345 emacs foo.txt
50646 This says pretty much the same thing as the last example, except that we are
50647 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
50648 that we are expecting to see a TCP connection from @code{host} to local TCP port
50649 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
50650 want for the port number as long as it does not conflict with any existing TCP
50651 ports on the target system. This same port number must be used in the host
50652 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
50653 you chose a port number that conflicts with another service, @command{gdbserver} will
50654 print an error message and exit.
50656 @command{gdbserver} can also attach to running programs.
50657 This is accomplished via the @option{--attach} argument. The syntax is:
50660 target> gdbserver --attach @var{comm} @var{pid}
50663 @var{pid} is the process ID of a currently running process. It isn't
50664 necessary to point @command{gdbserver} at a binary for the running process.
50666 To start @code{gdbserver} without supplying an initial command to run
50667 or process ID to attach, use the @option{--multi} command line option.
50668 In such case you should connect using @kbd{target extended-remote} to start
50669 the program you want to debug.
50672 target> gdbserver --multi @var{comm}
50676 @subheading Usage (host side)
50682 You need an unstripped copy of the target program on your host system, since
50683 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
50684 would, with the target program as the first argument. (You may need to use the
50685 @option{--baud} option if the serial line is running at anything except 9600 baud.)
50686 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
50687 new command you need to know about is @code{target remote}
50688 (or @code{target extended-remote}). Its argument is either
50689 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
50690 descriptor. For example:
50694 @c @file would wrap it as F</dev/ttyb>.
50695 (@value{GDBP}) target remote /dev/ttyb
50698 (@value{GDBP}) target remote @file{/dev/ttyb}
50703 communicates with the server via serial line @file{/dev/ttyb}, and:
50706 (@value{GDBP}) target remote the-target:2345
50710 communicates via a TCP connection to port 2345 on host `the-target', where
50711 you previously started up @command{gdbserver} with the same port number. Note that for
50712 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
50713 command, otherwise you may get an error that looks something like
50714 `Connection refused'.
50716 @command{gdbserver} can also debug multiple inferiors at once,
50719 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
50720 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
50723 @ref{Inferiors Connections and Programs}.
50725 In such case use the @code{extended-remote} @value{GDBN} command variant:
50728 (@value{GDBP}) target extended-remote the-target:2345
50731 The @command{gdbserver} option @option{--multi} may or may not be used in such
50735 @c man begin OPTIONS gdbserver
50736 There are three different modes for invoking @command{gdbserver}:
50741 Debug a specific program specified by its program name:
50744 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
50747 The @var{comm} parameter specifies how should the server communicate
50748 with @value{GDBN}; it is either a device name (to use a serial line),
50749 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
50750 stdin/stdout of @code{gdbserver}. Specify the name of the program to
50751 debug in @var{prog}. Any remaining arguments will be passed to the
50752 program verbatim. When the program exits, @value{GDBN} will close the
50753 connection, and @code{gdbserver} will exit.
50756 Debug a specific program by specifying the process ID of a running
50760 gdbserver --attach @var{comm} @var{pid}
50763 The @var{comm} parameter is as described above. Supply the process ID
50764 of a running program in @var{pid}; @value{GDBN} will do everything
50765 else. Like with the previous mode, when the process @var{pid} exits,
50766 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
50769 Multi-process mode -- debug more than one program/process:
50772 gdbserver --multi @var{comm}
50775 In this mode, @value{GDBN} can instruct @command{gdbserver} which
50776 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
50777 close the connection when a process being debugged exits, so you can
50778 debug several processes in the same session.
50781 In each of the modes you may specify these options:
50786 List all options, with brief explanations.
50789 This option causes @command{gdbserver} to print its version number and exit.
50792 @command{gdbserver} will attach to a running program. The syntax is:
50795 target> gdbserver --attach @var{comm} @var{pid}
50798 @var{pid} is the process ID of a currently running process. It isn't
50799 necessary to point @command{gdbserver} at a binary for the running process.
50802 To start @code{gdbserver} without supplying an initial command to run
50803 or process ID to attach, use this command line option.
50804 Then you can connect using @kbd{target extended-remote} and start
50805 the program you want to debug. The syntax is:
50808 target> gdbserver --multi @var{comm}
50811 @item --debug@r{[}=option1,option2,@dots{}@r{]}
50812 Instruct @code{gdbserver} to display extra status information about
50813 the debugging process. This option is intended for @code{gdbserver}
50814 development and for bug reports to the developers.
50816 Each @var{option} is the name of a component for which debugging
50817 should be enabled. The list of possible options is @option{all},
50818 @option{threads}, @option{event-loop}, @option{remote}. The special
50819 option @option{all} enables all components. The option list is
50820 processed left to right, and an option can be prefixed with the
50821 @kbd{-} character to disable output for that component, so you could write:
50824 target> gdbserver --debug=all,-event-loop
50828 to turn on debug output for all components except @option{event-loop}.
50829 If no options are passed to @option{--debug} then this is treated as
50830 equivalent to @option{--debug=threads}. This could change in future
50831 releases of @code{gdbserver}.
50833 @item --debug-file=@var{filename}
50834 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
50835 This option is intended for @code{gdbserver} development and for bug reports to
50838 @item --debug-format=option1@r{[},option2,...@r{]}
50839 Instruct @code{gdbserver} to include extra information in each line
50840 of debugging output.
50841 @xref{Other Command-Line Arguments for gdbserver}.
50844 Specify a wrapper to launch programs
50845 for debugging. The option should be followed by the name of the
50846 wrapper, then any command-line arguments to pass to the wrapper, then
50847 @kbd{--} indicating the end of the wrapper arguments.
50850 By default, @command{gdbserver} keeps the listening TCP port open, so that
50851 additional connections are possible. However, if you start @code{gdbserver}
50852 with the @option{--once} option, it will stop listening for any further
50853 connection attempts after connecting to the first @value{GDBN} session.
50855 @c --disable-packet is not documented for users.
50857 @c --disable-randomization and --no-disable-randomization are superseded by
50858 @c QDisableRandomization.
50863 @c man begin SEEALSO gdbserver
50865 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
50866 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
50867 documentation are properly installed at your site, the command
50873 should give you access to the complete manual.
50875 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
50876 Richard M. Stallman and Roland H. Pesch, July 1991.
50883 @c man title gcore Generate a core file of a running program
50886 @c man begin SYNOPSIS gcore
50887 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
50891 @c man begin DESCRIPTION gcore
50892 Generate core dumps of one or more running programs with process IDs
50893 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
50894 is equivalent to one produced by the kernel when the process crashes
50895 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
50896 limit). However, unlike after a crash, after @command{gcore} finishes
50897 its job the program remains running without any change.
50900 @c man begin OPTIONS gcore
50903 Dump all memory mappings. The actual effect of this option depends on
50904 the Operating System. On @sc{gnu}/Linux, it will disable
50905 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
50906 enable @code{dump-excluded-mappings} (@pxref{set
50907 dump-excluded-mappings}).
50909 @item -o @var{prefix}
50910 The optional argument @var{prefix} specifies the prefix to be used
50911 when composing the file names of the core dumps. The file name is
50912 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
50913 process ID of the running program being analyzed by @command{gcore}.
50914 If not specified, @var{prefix} defaults to @var{gcore}.
50918 @c man begin SEEALSO gcore
50920 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
50921 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
50922 documentation are properly installed at your site, the command
50929 should give you access to the complete manual.
50931 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
50932 Richard M. Stallman and Roland H. Pesch, July 1991.
50939 @c man title gdbinit GDB initialization scripts
50942 @c man begin SYNOPSIS gdbinit
50943 @ifset SYSTEM_GDBINIT
50944 @value{SYSTEM_GDBINIT}
50947 @ifset SYSTEM_GDBINIT_DIR
50948 @value{SYSTEM_GDBINIT_DIR}/*
50951 ~/.config/gdb/gdbinit
50959 @c man begin DESCRIPTION gdbinit
50960 These files contain @value{GDBN} commands to automatically execute during
50961 @value{GDBN} startup. The lines of contents are canned sequences of commands,
50964 the @value{GDBN} manual in node @code{Sequences}
50965 -- shell command @code{info -f gdb -n Sequences}.
50971 Please read more in
50973 the @value{GDBN} manual in node @code{Startup}
50974 -- shell command @code{info -f gdb -n Startup}.
50981 @ifset SYSTEM_GDBINIT
50982 @item @value{SYSTEM_GDBINIT}
50984 @ifclear SYSTEM_GDBINIT
50985 @item (not enabled with @code{--with-system-gdbinit} during compilation)
50987 System-wide initialization file. It is executed unless user specified
50988 @value{GDBN} option @code{-nx} or @code{-n}.
50991 the @value{GDBN} manual in node @code{System-wide configuration}
50992 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
50994 @ifset SYSTEM_GDBINIT_DIR
50995 @item @value{SYSTEM_GDBINIT_DIR}
50997 @ifclear SYSTEM_GDBINIT_DIR
50998 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
51000 System-wide initialization directory. All files in this directory are
51001 executed on startup unless user specified @value{GDBN} option @code{-nx} or
51002 @code{-n}, as long as they have a recognized file extension.
51005 the @value{GDBN} manual in node @code{System-wide configuration}
51006 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
51009 @ref{System-wide configuration}.
51012 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
51013 User initialization file. It is executed unless user specified
51014 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
51016 @item @file{.gdbinit}
51017 Initialization file for current directory. It may need to be enabled with
51018 @value{GDBN} security command @code{set auto-load local-gdbinit}.
51021 the @value{GDBN} manual in node @code{Init File in the Current Directory}
51022 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
51025 @ref{Init File in the Current Directory}.
51030 @c man begin SEEALSO gdbinit
51032 gdb(1), @code{info -f gdb -n Startup}
51034 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
51035 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
51036 documentation are properly installed at your site, the command
51042 should give you access to the complete manual.
51044 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
51045 Richard M. Stallman and Roland H. Pesch, July 1991.
51049 @node gdb-add-index man
51050 @heading gdb-add-index
51051 @pindex gdb-add-index
51052 @anchor{gdb-add-index}
51054 @c man title gdb-add-index Add index files to speed up GDB
51056 @c man begin SYNOPSIS gdb-add-index
51057 gdb-add-index @var{filename}
51060 @c man begin DESCRIPTION gdb-add-index
51061 When @value{GDBN} finds a symbol file, it scans the symbols in the
51062 file in order to construct an internal symbol table. This lets most
51063 @value{GDBN} operations work quickly--at the cost of a delay early on.
51064 For large programs, this delay can be quite lengthy, so @value{GDBN}
51065 provides a way to build an index, which speeds up startup.
51067 To determine whether a file contains such an index, use the command
51068 @kbd{readelf -S filename}: the index is stored in a section named
51069 @code{.gdb_index}. The index file can only be produced on systems
51070 which use ELF binaries and DWARF debug information (i.e., sections
51071 named @code{.debug_*}).
51073 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
51074 in the @env{PATH} environment variable. If you want to use different
51075 versions of these programs, you can specify them through the
51076 @env{GDB} and @env{OBJDUMP} environment variables.
51080 the @value{GDBN} manual in node @code{Index Files}
51081 -- shell command @kbd{info -f gdb -n "Index Files"}.
51088 @c man begin SEEALSO gdb-add-index
51090 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
51091 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
51092 documentation are properly installed at your site, the command
51098 should give you access to the complete manual.
51100 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
51101 Richard M. Stallman and Roland H. Pesch, July 1991.
51107 @node GNU Free Documentation License
51108 @appendix GNU Free Documentation License
51111 @node Concept Index
51112 @unnumbered Concept Index
51116 @node Command and Variable Index
51117 @unnumbered Command, Variable, and Function Index
51122 % I think something like @@colophon should be in texinfo. In the
51124 \long\def\colophon{\hbox to0pt{}\vfill
51125 \centerline{The body of this manual is set in}
51126 \centerline{\fontname\tenrm,}
51127 \centerline{with headings in {\bf\fontname\tenbf}}
51128 \centerline{and examples in {\tt\fontname\tentt}.}
51129 \centerline{{\it\fontname\tenit\/},}
51130 \centerline{{\bf\fontname\tenbf}, and}
51131 \centerline{{\sl\fontname\tensl\/}}
51132 \centerline{are used for emphasis.}\vfill}
51134 % Blame: doc@@cygnus.com, 1991.