1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2022 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{} 1988-2022 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) 1988-2022 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 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share GDB
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
966 form equivalents, the method used to search the file system for the
967 symbol and/or executable file is the same as that used by the
968 @code{file} command. @xref{Files, ,file}.
970 Many options have both long and short forms; both are shown in the
971 following list. @value{GDBN} also recognizes the long forms if you truncate
972 them, so long as enough of the option is present to be unambiguous.
973 (If you prefer, you can flag option arguments with @samp{--} rather
974 than @samp{-}, though we illustrate the more usual convention.)
976 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
977 @c way, both those who look for -foo and --foo in the index, will find
981 @item -symbols @var{file}
983 @cindex @code{--symbols}
985 Read symbol table from file @var{file}.
987 @item -exec @var{file}
989 @cindex @code{--exec}
991 Use file @var{file} as the executable file to execute when appropriate,
992 and for examining pure data in conjunction with a core dump.
996 Read symbol table from file @var{file} and use it as the executable
999 @item -core @var{file}
1000 @itemx -c @var{file}
1001 @cindex @code{--core}
1003 Use file @var{file} as a core dump to examine.
1005 @item -pid @var{number}
1006 @itemx -p @var{number}
1007 @cindex @code{--pid}
1009 Connect to process ID @var{number}, as with the @code{attach} command.
1011 @item -command @var{file}
1012 @itemx -x @var{file}
1013 @cindex @code{--command}
1015 Execute commands from file @var{file}. The contents of this file is
1016 evaluated exactly as the @code{source} command would.
1017 @xref{Command Files,, Command files}.
1019 @item -eval-command @var{command}
1020 @itemx -ex @var{command}
1021 @cindex @code{--eval-command}
1023 Execute a single @value{GDBN} command.
1025 This option may be used multiple times to call multiple commands. It may
1026 also be interleaved with @samp{-command} as required.
1029 @value{GDBP} -ex 'target sim' -ex 'load' \
1030 -x setbreakpoints -ex 'run' a.out
1033 @item -init-command @var{file}
1034 @itemx -ix @var{file}
1035 @cindex @code{--init-command}
1037 Execute commands from file @var{file} before loading the inferior (but
1038 after loading gdbinit files).
1041 @item -init-eval-command @var{command}
1042 @itemx -iex @var{command}
1043 @cindex @code{--init-eval-command}
1045 Execute a single @value{GDBN} command before loading the inferior (but
1046 after loading gdbinit files).
1049 @item -early-init-command @var{file}
1050 @itemx -eix @var{file}
1051 @cindex @code{--early-init-command}
1053 Execute commands from @var{file} very early in the initialization
1054 process, before any output is produced. @xref{Startup}.
1056 @item -early-init-eval-command @var{command}
1057 @itemx -eiex @var{command}
1058 @cindex @code{--early-init-eval-command}
1059 @cindex @code{-eiex}
1060 Execute a single @value{GDBN} command very early in the initialization
1061 process, before any output is produced.
1063 @item -directory @var{directory}
1064 @itemx -d @var{directory}
1065 @cindex @code{--directory}
1067 Add @var{directory} to the path to search for source and script files.
1071 @cindex @code{--readnow}
1073 Read each symbol file's entire symbol table immediately, rather than
1074 the default, which is to read it incrementally as it is needed.
1075 This makes startup slower, but makes future operations faster.
1078 @anchor{--readnever}
1079 @cindex @code{--readnever}, command-line option
1080 Do not read each symbol file's symbolic debug information. This makes
1081 startup faster but at the expense of not being able to perform
1082 symbolic debugging. DWARF unwind information is also not read,
1083 meaning backtraces may become incomplete or inaccurate. One use of
1084 this is when a user simply wants to do the following sequence: attach,
1085 dump core, detach. Loading the debugging information in this case is
1086 an unnecessary cause of delay.
1090 @subsection Choosing Modes
1092 You can run @value{GDBN} in various alternative modes---for example, in
1093 batch mode or quiet mode.
1101 Do not execute commands found in any initialization files
1102 (@pxref{Initialization Files}).
1107 Do not execute commands found in any home directory initialization
1108 file (@pxref{Initialization Files,,Home directory initialization
1109 file}). The system wide and current directory initialization files
1115 @cindex @code{--quiet}
1116 @cindex @code{--silent}
1118 ``Quiet''. Do not print the introductory and copyright messages. These
1119 messages are also suppressed in batch mode.
1121 @kindex set startup-quietly
1122 @kindex show startup-quietly
1123 This can also be enabled using @code{set startup-quietly on}. The
1124 default is @code{off}. Use @code{show startup-quietly} to see the
1125 current setting. Place @code{set startup-quietly on} into your early
1126 initialization file (@pxref{Initialization Files,,Initialization
1127 Files}) to have future @value{GDBN} sessions startup quietly.
1130 @cindex @code{--batch}
1131 Run in batch mode. Exit with status @code{0} after processing all the
1132 command files specified with @samp{-x} (and all commands from
1133 initialization files, if not inhibited with @samp{-n}). Exit with
1134 nonzero status if an error occurs in executing the @value{GDBN} commands
1135 in the command files. Batch mode also disables pagination, sets unlimited
1136 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1137 off} were in effect (@pxref{Messages/Warnings}).
1139 Batch mode may be useful for running @value{GDBN} as a filter, for
1140 example to download and run a program on another computer; in order to
1141 make this more useful, the message
1144 Program exited normally.
1148 (which is ordinarily issued whenever a program running under
1149 @value{GDBN} control terminates) is not issued when running in batch
1153 @cindex @code{--batch-silent}
1154 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1155 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1156 unaffected). This is much quieter than @samp{-silent} and would be useless
1157 for an interactive session.
1159 This is particularly useful when using targets that give @samp{Loading section}
1160 messages, for example.
1162 Note that targets that give their output via @value{GDBN}, as opposed to
1163 writing directly to @code{stdout}, will also be made silent.
1165 @item -return-child-result
1166 @cindex @code{--return-child-result}
1167 The return code from @value{GDBN} will be the return code from the child
1168 process (the process being debugged), with the following exceptions:
1172 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1173 internal error. In this case the exit code is the same as it would have been
1174 without @samp{-return-child-result}.
1176 The user quits with an explicit value. E.g., @samp{quit 1}.
1178 The child process never runs, or is not allowed to terminate, in which case
1179 the exit code will be -1.
1182 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1183 when @value{GDBN} is being used as a remote program loader or simulator
1188 @cindex @code{--nowindows}
1190 ``No windows''. If @value{GDBN} comes with a graphical user interface
1191 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1192 interface. If no GUI is available, this option has no effect.
1196 @cindex @code{--windows}
1198 If @value{GDBN} includes a GUI, then this option requires it to be
1201 @item -cd @var{directory}
1203 Run @value{GDBN} using @var{directory} as its working directory,
1204 instead of the current directory.
1206 @item -data-directory @var{directory}
1207 @itemx -D @var{directory}
1208 @cindex @code{--data-directory}
1210 Run @value{GDBN} using @var{directory} as its data directory.
1211 The data directory is where @value{GDBN} searches for its
1212 auxiliary files. @xref{Data Files}.
1216 @cindex @code{--fullname}
1218 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1219 subprocess. It tells @value{GDBN} to output the full file name and line
1220 number in a standard, recognizable fashion each time a stack frame is
1221 displayed (which includes each time your program stops). This
1222 recognizable format looks like two @samp{\032} characters, followed by
1223 the file name, line number and character position separated by colons,
1224 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1225 @samp{\032} characters as a signal to display the source code for the
1228 @item -annotate @var{level}
1229 @cindex @code{--annotate}
1230 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1231 effect is identical to using @samp{set annotate @var{level}}
1232 (@pxref{Annotations}). The annotation @var{level} controls how much
1233 information @value{GDBN} prints together with its prompt, values of
1234 expressions, source lines, and other types of output. Level 0 is the
1235 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1236 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1237 that control @value{GDBN}, and level 2 has been deprecated.
1239 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1243 @cindex @code{--args}
1244 Change interpretation of command line so that arguments following the
1245 executable file are passed as command line arguments to the inferior.
1246 This option stops option processing.
1248 @item -baud @var{bps}
1250 @cindex @code{--baud}
1252 Set the line speed (baud rate or bits per second) of any serial
1253 interface used by @value{GDBN} for remote debugging.
1255 @item -l @var{timeout}
1257 Set the timeout (in seconds) of any communication used by @value{GDBN}
1258 for remote debugging.
1260 @item -tty @var{device}
1261 @itemx -t @var{device}
1262 @cindex @code{--tty}
1264 Run using @var{device} for your program's standard input and output.
1265 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1267 @c resolve the situation of these eventually
1269 @cindex @code{--tui}
1270 Activate the @dfn{Text User Interface} when starting. The Text User
1271 Interface manages several text windows on the terminal, showing
1272 source, assembly, registers and @value{GDBN} command outputs
1273 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1274 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1275 Using @value{GDBN} under @sc{gnu} Emacs}).
1277 @item -interpreter @var{interp}
1278 @cindex @code{--interpreter}
1279 Use the interpreter @var{interp} for interface with the controlling
1280 program or device. This option is meant to be set by programs which
1281 communicate with @value{GDBN} using it as a back end.
1282 @xref{Interpreters, , Command Interpreters}.
1284 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1285 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1286 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1287 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1288 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1289 interfaces are no longer supported.
1292 @cindex @code{--write}
1293 Open the executable and core files for both reading and writing. This
1294 is equivalent to the @samp{set write on} command inside @value{GDBN}
1298 @cindex @code{--statistics}
1299 This option causes @value{GDBN} to print statistics about time and
1300 memory usage after it completes each command and returns to the prompt.
1303 @cindex @code{--version}
1304 This option causes @value{GDBN} to print its version number and
1305 no-warranty blurb, and exit.
1307 @item -configuration
1308 @cindex @code{--configuration}
1309 This option causes @value{GDBN} to print details about its build-time
1310 configuration parameters, and then exit. These details can be
1311 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1316 @subsection What @value{GDBN} Does During Startup
1317 @cindex @value{GDBN} startup
1319 Here's the description of what @value{GDBN} does during session startup:
1324 Performs minimal setup required to initialize basic internal state.
1327 @cindex early initialization file
1328 Reads commands from the early initialization file (if any) in your
1329 home directory. Only a restricted set of commands can be placed into
1330 an early initialization file, see @ref{Initialization Files}, for
1334 Executes commands and command files specified by the @samp{-eiex} and
1335 @samp{-eix} command line options in their specified order. Only a
1336 restricted set of commands can be used with @samp{-eiex} and
1337 @samp{eix}, see @ref{Initialization Files}, for details.
1340 Sets up the command interpreter as specified by the command line
1341 (@pxref{Mode Options, interpreter}).
1345 Reads the system wide initialization file and the files from the
1346 system wide initialization directory, @pxref{System Wide Init Files}.
1349 Reads the initialization file (if any) in your home directory and
1350 executes all the commands in that file, @pxref{Home Directory Init
1353 @anchor{Option -init-eval-command}
1355 Executes commands and command files specified by the @samp{-iex} and
1356 @samp{-ix} options in their specified order. Usually you should use the
1357 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1358 settings before @value{GDBN} init files get executed and before inferior
1362 Processes command line options and operands.
1365 Reads and executes the commands from the initialization file (if any)
1366 in the current working directory as long as @samp{set auto-load
1367 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1368 Directory}). This is only done if the current directory is different
1369 from your home directory. Thus, you can have more than one init file,
1370 one generic in your home directory, and another, specific to the
1371 program you are debugging, in the directory where you invoke
1372 @value{GDBN}. @xref{Init File in the Current Directory during
1376 If the command line specified a program to debug, or a process to
1377 attach to, or a core file, @value{GDBN} loads any auto-loaded
1378 scripts provided for the program or for its loaded shared libraries.
1379 @xref{Auto-loading}.
1381 If you wish to disable the auto-loading during startup,
1382 you must do something like the following:
1385 $ gdb -iex "set auto-load python-scripts off" myprogram
1388 Option @samp{-ex} does not work because the auto-loading is then turned
1392 Executes commands and command files specified by the @samp{-ex} and
1393 @samp{-x} options in their specified order. @xref{Command Files}, for
1394 more details about @value{GDBN} command files.
1397 Reads the command history recorded in the @dfn{history file}.
1398 @xref{Command History}, for more details about the command history and the
1399 files where @value{GDBN} records it.
1402 @node Initialization Files
1403 @subsection Initialization Files
1404 @cindex init file name
1406 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1407 from several initialization files. These initialization files use the
1408 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1409 processed by @value{GDBN} in the same way.
1411 To display the list of initialization files loaded by @value{GDBN} at
1412 startup, in the order they will be loaded, you can use @kbd{gdb
1415 @cindex early initialization
1416 The @dfn{early initialization} file is loaded very early in
1417 @value{GDBN}'s initialization process, before the interpreter
1418 (@pxref{Interpreters}) has been initialized, and before the default
1419 target (@pxref{Targets}) is initialized. Only @code{set} or
1420 @code{source} commands should be placed into an early initialization
1421 file, and the only @code{set} commands that can be used are those that
1422 control how @value{GDBN} starts up.
1424 Commands that can be placed into an early initialization file will be
1425 documented as such throughout this manual. Any command that is not
1426 documented as being suitable for an early initialization file should
1427 instead be placed into a general initialization file. Command files
1428 passed to @code{--early-init-command} or @code{-eix} are also early
1429 initialization files, with the same command restrictions. Only
1430 commands that can appear in an early initialization file should be
1431 passed to @code{--early-init-eval-command} or @code{-eiex}.
1433 @cindex general initialization
1434 In contrast, the @dfn{general initialization} files are processed
1435 later, after @value{GDBN} has finished its own internal initialization
1436 process, any valid command can be used in these files.
1438 @cindex initialization file
1439 Throughout the rest of this document the term @dfn{initialization
1440 file} refers to one of the general initialization files, not the early
1441 initialization file. Any discussion of the early initialization file
1442 will specifically mention that it is the early initialization file
1445 As the system wide and home directory initialization files are
1446 processed before most command line options, changes to settings
1447 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1448 command line options and operands.
1450 The following sections describe where @value{GDBN} looks for the early
1451 initialization and initialization files, and the order that the files
1454 @subsubsection Home directory early initialization files
1456 @value{GDBN} initially looks for an early initialization file in the
1457 users home directory@footnote{On DOS/Windows systems, the home
1458 directory is the one pointed to by the @env{HOME} environment
1459 variable.}. There are a number of locations that @value{GDBN} will
1460 search in the home directory, these locations are searched in order
1461 and @value{GDBN} will load the first file that it finds, and
1462 subsequent locations will not be checked.
1464 On non-macOS hosts the locations searched are:
1467 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1470 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1471 by the environment variable @env{HOME}, if it is defined.
1473 The file @file{.gdbearlyinit} within the directory pointed to by the
1474 environment variable @env{HOME}, if it is defined.
1477 By contrast, on macOS hosts the locations searched are:
1480 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1481 directory pointed to by the environment variable @env{HOME}, if it is
1484 The file @file{.gdbearlyinit} within the directory pointed to by the
1485 environment variable @env{HOME}, if it is defined.
1488 It is possible to prevent the home directory early initialization file
1489 from being loaded using the @samp{-nx} or @samp{-nh} command line
1490 options, @pxref{Mode Options,,Choosing Modes}.
1492 @anchor{System Wide Init Files}
1493 @subsubsection System wide initialization files
1495 There are two locations that are searched for system wide
1496 initialization files. Both of these locations are always checked:
1500 @item @file{system.gdbinit}
1501 This is a single system-wide initialization file. Its location is
1502 specified with the @code{--with-system-gdbinit} configure option
1503 (@pxref{System-wide configuration}). It is loaded first when
1504 @value{GDBN} starts, before command line options have been processed.
1506 @item @file{system.gdbinit.d}
1507 This is the system-wide initialization directory. Its location is
1508 specified with the @code{--with-system-gdbinit-dir} configure option
1509 (@pxref{System-wide configuration}). Files in this directory are
1510 loaded in alphabetical order immediately after @file{system.gdbinit}
1511 (if enabled) when @value{GDBN} starts, before command line options
1512 have been processed. Files need to have a recognized scripting
1513 language extension (@file{.py}/@file{.scm}) or be named with a
1514 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1515 commands. @value{GDBN} will not recurse into any subdirectories of
1520 It is possible to prevent the system wide initialization files from
1521 being loaded using the @samp{-nx} command line option, @pxref{Mode
1522 Options,,Choosing Modes}.
1524 @anchor{Home Directory Init File}
1525 @subsubsection Home directory initialization file
1526 @cindex @file{gdbinit}
1527 @cindex @file{.gdbinit}
1528 @cindex @file{gdb.ini}
1530 After loading the system wide initialization files @value{GDBN} will
1531 look for an initialization file in the users home
1532 directory@footnote{On DOS/Windows systems, the home directory is the
1533 one pointed to by the @env{HOME} environment variable.}. There are a
1534 number of locations that @value{GDBN} will search in the home
1535 directory, these locations are searched in order and @value{GDBN} will
1536 load the first file that it finds, and subsequent locations will not
1539 On non-Apple hosts the locations searched are:
1541 @item $XDG_CONFIG_HOME/gdb/gdbinit
1542 @item $HOME/.config/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 While on Apple hosts the locations searched are:
1548 @item $HOME/Library/Preferences/gdb/gdbinit
1549 @item $HOME/.gdbinit
1552 It is possible to prevent the home directory initialization file from
1553 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1554 @pxref{Mode Options,,Choosing Modes}.
1556 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1557 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1558 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1559 uses the standard name, but if it finds a @file{gdb.ini} file in your
1560 home directory, it warns you about that and suggests to rename the
1561 file to the standard name.
1563 @anchor{Init File in the Current Directory during Startup}
1564 @subsubsection Local directory initialization file
1566 @value{GDBN} will check the current directory for a file called
1567 @file{.gdbinit}. It is loaded last, after command line options
1568 other than @samp{-x} and @samp{-ex} have been processed. The command
1569 line options @samp{-x} and @samp{-ex} are processed last, after
1570 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1573 If the file in the current directory was already loaded as the home
1574 directory initialization file then it will not be loaded a second
1577 It is possible to prevent the local directory initialization file from
1578 being loaded using the @samp{-nx} command line option, @pxref{Mode
1579 Options,,Choosing Modes}.
1582 @section Quitting @value{GDBN}
1583 @cindex exiting @value{GDBN}
1584 @cindex leaving @value{GDBN}
1587 @kindex quit @r{[}@var{expression}@r{]}
1588 @kindex exit @r{[}@var{expression}@r{]}
1589 @kindex q @r{(@code{quit})}
1590 @item quit @r{[}@var{expression}@r{]}
1591 @itemx exit @r{[}@var{expression}@r{]}
1593 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1594 @code{q}), the @code{exit} command, or type an end-of-file
1595 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1596 @value{GDBN} will terminate normally; otherwise it will terminate using
1597 the result of @var{expression} as the error code.
1601 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1602 terminates the action of any @value{GDBN} command that is in progress and
1603 returns to @value{GDBN} command level. It is safe to type the interrupt
1604 character at any time because @value{GDBN} does not allow it to take effect
1605 until a time when it is safe.
1607 If you have been using @value{GDBN} to control an attached process or
1608 device, you can release it with the @code{detach} command
1609 (@pxref{Attach, ,Debugging an Already-running Process}).
1611 @node Shell Commands
1612 @section Shell Commands
1614 If you need to execute occasional shell commands during your
1615 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1616 just use the @code{shell} command.
1621 @cindex shell escape
1622 @item shell @var{command-string}
1623 @itemx !@var{command-string}
1624 Invoke a standard shell to execute @var{command-string}.
1625 Note that no space is needed between @code{!} and @var{command-string}.
1626 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1627 exists, determines which shell to run. Otherwise @value{GDBN} uses
1628 the default shell (@file{/bin/sh} on GNU and Unix systems,
1629 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1632 The utility @code{make} is often needed in development environments.
1633 You do not have to use the @code{shell} command for this purpose in
1638 @cindex calling make
1639 @item make @var{make-args}
1640 Execute the @code{make} program with the specified
1641 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1647 @cindex send the output of a gdb command to a shell command
1649 @item pipe [@var{command}] | @var{shell_command}
1650 @itemx | [@var{command}] | @var{shell_command}
1651 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1652 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1653 Executes @var{command} and sends its output to @var{shell_command}.
1654 Note that no space is needed around @code{|}.
1655 If no @var{command} is provided, the last command executed is repeated.
1657 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1658 can be used to specify an alternate delimiter string @var{delim} that separates
1659 the @var{command} from the @var{shell_command}.
1692 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1693 this contains a PIPE char
1694 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1695 this contains a PIPE char!
1701 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1702 can be used to examine the exit status of the last shell command launched
1703 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1704 @xref{Convenience Vars,, Convenience Variables}.
1706 @node Logging Output
1707 @section Logging Output
1708 @cindex logging @value{GDBN} output
1709 @cindex save @value{GDBN} output to a file
1711 You may want to save the output of @value{GDBN} commands to a file.
1712 There are several commands to control @value{GDBN}'s logging.
1715 @kindex set logging enabled
1716 @item set logging enabled [on|off]
1717 Enable or disable logging.
1718 @cindex logging file name
1719 @item set logging file @var{file}
1720 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1721 @item set logging overwrite [on|off]
1722 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1723 you want @code{set logging enabled on} to overwrite the logfile instead.
1724 @item set logging redirect [on|off]
1725 By default, @value{GDBN} output will go to both the terminal and the logfile.
1726 Set @code{redirect} if you want output to go only to the log file.
1727 @item set logging debugredirect [on|off]
1728 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1729 Set @code{debugredirect} if you want debug output to go only to the log file.
1730 @kindex show logging
1732 Show the current values of the logging settings.
1735 You can also redirect the output of a @value{GDBN} command to a
1736 shell command. @xref{pipe}.
1738 @chapter @value{GDBN} Commands
1740 You can abbreviate a @value{GDBN} command to the first few letters of the command
1741 name, if that abbreviation is unambiguous; and you can repeat certain
1742 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1743 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1744 show you the alternatives available, if there is more than one possibility).
1747 * Command Syntax:: How to give commands to @value{GDBN}
1748 * Command Settings:: How to change default behavior of commands
1749 * Completion:: Command completion
1750 * Command Options:: Command options
1751 * Help:: How to ask @value{GDBN} for help
1754 @node Command Syntax
1755 @section Command Syntax
1757 A @value{GDBN} command is a single line of input. There is no limit on
1758 how long it can be. It starts with a command name, which is followed by
1759 arguments whose meaning depends on the command name. For example, the
1760 command @code{step} accepts an argument which is the number of times to
1761 step, as in @samp{step 5}. You can also use the @code{step} command
1762 with no arguments. Some commands do not allow any arguments.
1764 @cindex abbreviation
1765 @value{GDBN} command names may always be truncated if that abbreviation is
1766 unambiguous. Other possible command abbreviations are listed in the
1767 documentation for individual commands. In some cases, even ambiguous
1768 abbreviations are allowed; for example, @code{s} is specially defined as
1769 equivalent to @code{step} even though there are other commands whose
1770 names start with @code{s}. You can test abbreviations by using them as
1771 arguments to the @code{help} command.
1773 @cindex repeating commands
1774 @kindex RET @r{(repeat last command)}
1775 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1776 repeat the previous command. Certain commands (for example, @code{run})
1777 will not repeat this way; these are commands whose unintentional
1778 repetition might cause trouble and which you are unlikely to want to
1779 repeat. User-defined commands can disable this feature; see
1780 @ref{Define, dont-repeat}.
1782 The @code{list} and @code{x} commands, when you repeat them with
1783 @key{RET}, construct new arguments rather than repeating
1784 exactly as typed. This permits easy scanning of source or memory.
1786 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1787 output, in a way similar to the common utility @code{more}
1788 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1789 @key{RET} too many in this situation, @value{GDBN} disables command
1790 repetition after any command that generates this sort of display.
1792 @kindex # @r{(a comment)}
1794 Any text from a @kbd{#} to the end of the line is a comment; it does
1795 nothing. This is useful mainly in command files (@pxref{Command
1796 Files,,Command Files}).
1798 @cindex repeating command sequences
1799 @kindex Ctrl-o @r{(operate-and-get-next)}
1800 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1801 commands. This command accepts the current line, like @key{RET}, and
1802 then fetches the next line relative to the current line from the history
1806 @node Command Settings
1807 @section Command Settings
1808 @cindex default behavior of commands, changing
1809 @cindex default settings, changing
1811 Many commands change their behavior according to command-specific
1812 variables or settings. These settings can be changed with the
1813 @code{set} subcommands. For example, the @code{print} command
1814 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1815 settings changeable with the commands @code{set print elements
1816 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1818 You can change these settings to your preference in the gdbinit files
1819 loaded at @value{GDBN} startup. @xref{Startup}.
1821 The settings can also be changed interactively during the debugging
1822 session. For example, to change the limit of array elements to print,
1823 you can do the following:
1825 (@value{GDBN}) set print elements 10
1826 (@value{GDBN}) print some_array
1827 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1830 The above @code{set print elements 10} command changes the number of
1831 elements to print from the default of 200 to 10. If you only intend
1832 this limit of 10 to be used for printing @code{some_array}, then you
1833 must restore the limit back to 200, with @code{set print elements
1836 Some commands allow overriding settings with command options. For
1837 example, the @code{print} command supports a number of options that
1838 allow overriding relevant global print settings as set by @code{set
1839 print} subcommands. @xref{print options}. The example above could be
1842 (@value{GDBN}) print -elements 10 -- some_array
1843 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1846 Alternatively, you can use the @code{with} command to change a setting
1847 temporarily, for the duration of a command invocation.
1850 @kindex with command
1851 @kindex w @r{(@code{with})}
1853 @cindex temporarily change settings
1854 @item with @var{setting} [@var{value}] [-- @var{command}]
1855 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1856 Temporarily set @var{setting} to @var{value} for the duration of
1859 @var{setting} is any setting you can change with the @code{set}
1860 subcommands. @var{value} is the value to assign to @code{setting}
1861 while running @code{command}.
1863 If no @var{command} is provided, the last command executed is
1866 If a @var{command} is provided, it must be preceded by a double dash
1867 (@code{--}) separator. This is required because some settings accept
1868 free-form arguments, such as expressions or filenames.
1870 For example, the command
1872 (@value{GDBN}) with print array on -- print some_array
1875 is equivalent to the following 3 commands:
1877 (@value{GDBN}) set print array on
1878 (@value{GDBN}) print some_array
1879 (@value{GDBN}) set print array off
1882 The @code{with} command is particularly useful when you want to
1883 override a setting while running user-defined commands, or commands
1884 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1887 (@value{GDBN}) with print pretty on -- my_complex_command
1890 To change several settings for the same command, you can nest
1891 @code{with} commands. For example, @code{with language ada -- with
1892 print elements 10} temporarily changes the language to Ada and sets a
1893 limit of 10 elements to print for arrays and strings.
1898 @section Command Completion
1901 @cindex word completion
1902 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1903 only one possibility; it can also show you what the valid possibilities
1904 are for the next word in a command, at any time. This works for @value{GDBN}
1905 commands, @value{GDBN} subcommands, command options, and the names of symbols
1908 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1909 of a word. If there is only one possibility, @value{GDBN} fills in the
1910 word, and waits for you to finish the command (or press @key{RET} to
1911 enter it). For example, if you type
1913 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1914 @c complete accuracy in these examples; space introduced for clarity.
1915 @c If texinfo enhancements make it unnecessary, it would be nice to
1916 @c replace " @key" by "@key" in the following...
1918 (@value{GDBP}) info bre@key{TAB}
1922 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1923 the only @code{info} subcommand beginning with @samp{bre}:
1926 (@value{GDBP}) info breakpoints
1930 You can either press @key{RET} at this point, to run the @code{info
1931 breakpoints} command, or backspace and enter something else, if
1932 @samp{breakpoints} does not look like the command you expected. (If you
1933 were sure you wanted @code{info breakpoints} in the first place, you
1934 might as well just type @key{RET} immediately after @samp{info bre},
1935 to exploit command abbreviations rather than command completion).
1937 If there is more than one possibility for the next word when you press
1938 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1939 characters and try again, or just press @key{TAB} a second time;
1940 @value{GDBN} displays all the possible completions for that word. For
1941 example, you might want to set a breakpoint on a subroutine whose name
1942 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1943 just sounds the bell. Typing @key{TAB} again displays all the
1944 function names in your program that begin with those characters, for
1948 (@value{GDBP}) b make_@key{TAB}
1949 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1950 make_a_section_from_file make_environ
1951 make_abs_section make_function_type
1952 make_blockvector make_pointer_type
1953 make_cleanup make_reference_type
1954 make_command make_symbol_completion_list
1955 (@value{GDBP}) b make_
1959 After displaying the available possibilities, @value{GDBN} copies your
1960 partial input (@samp{b make_} in the example) so you can finish the
1963 If the command you are trying to complete expects either a keyword or a
1964 number to follow, then @samp{NUMBER} will be shown among the available
1965 completions, for example:
1968 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1970 (@value{GDBP}) print -elements@tie{}
1974 Here, the option expects a number (e.g., @code{100}), not literal
1975 @code{NUMBER}. Such metasyntactical arguments are always presented in
1978 If you just want to see the list of alternatives in the first place, you
1979 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1980 means @kbd{@key{META} ?}. You can type this either by holding down a
1981 key designated as the @key{META} shift on your keyboard (if there is
1982 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1984 If the number of possible completions is large, @value{GDBN} will
1985 print as much of the list as it has collected, as well as a message
1986 indicating that the list may be truncated.
1989 (@value{GDBP}) b m@key{TAB}@key{TAB}
1991 <... the rest of the possible completions ...>
1992 *** List may be truncated, max-completions reached. ***
1997 This behavior can be controlled with the following commands:
2000 @kindex set max-completions
2001 @item set max-completions @var{limit}
2002 @itemx set max-completions unlimited
2003 Set the maximum number of completion candidates. @value{GDBN} will
2004 stop looking for more completions once it collects this many candidates.
2005 This is useful when completing on things like function names as collecting
2006 all the possible candidates can be time consuming.
2007 The default value is 200. A value of zero disables tab-completion.
2008 Note that setting either no limit or a very large limit can make
2010 @kindex show max-completions
2011 @item show max-completions
2012 Show the maximum number of candidates that @value{GDBN} will collect and show
2016 @cindex quotes in commands
2017 @cindex completion of quoted strings
2018 Sometimes the string you need, while logically a ``word'', may contain
2019 parentheses or other characters that @value{GDBN} normally excludes from
2020 its notion of a word. To permit word completion to work in this
2021 situation, you may enclose words in @code{'} (single quote marks) in
2022 @value{GDBN} commands.
2024 A likely situation where you might need this is in typing an
2025 expression that involves a C@t{++} symbol name with template
2026 parameters. This is because when completing expressions, GDB treats
2027 the @samp{<} character as word delimiter, assuming that it's the
2028 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2031 For example, when you want to call a C@t{++} template function
2032 interactively using the @code{print} or @code{call} commands, you may
2033 need to distinguish whether you mean the version of @code{name} that
2034 was specialized for @code{int}, @code{name<int>()}, or the version
2035 that was specialized for @code{float}, @code{name<float>()}. To use
2036 the word-completion facilities in this situation, type a single quote
2037 @code{'} at the beginning of the function name. This alerts
2038 @value{GDBN} that it may need to consider more information than usual
2039 when you press @key{TAB} or @kbd{M-?} to request word completion:
2042 (@value{GDBP}) p 'func<@kbd{M-?}
2043 func<int>() func<float>()
2044 (@value{GDBP}) p 'func<
2047 When setting breakpoints however (@pxref{Location Specifications}), you don't
2048 usually need to type a quote before the function name, because
2049 @value{GDBN} understands that you want to set a breakpoint on a
2053 (@value{GDBP}) b func<@kbd{M-?}
2054 func<int>() func<float>()
2055 (@value{GDBP}) b func<
2058 This is true even in the case of typing the name of C@t{++} overloaded
2059 functions (multiple definitions of the same function, distinguished by
2060 argument type). For example, when you want to set a breakpoint you
2061 don't need to distinguish whether you mean the version of @code{name}
2062 that takes an @code{int} parameter, @code{name(int)}, or the version
2063 that takes a @code{float} parameter, @code{name(float)}.
2066 (@value{GDBP}) b bubble(@kbd{M-?}
2067 bubble(int) bubble(double)
2068 (@value{GDBP}) b bubble(dou@kbd{M-?}
2072 See @ref{quoting names} for a description of other scenarios that
2075 For more information about overloaded functions, see @ref{C Plus Plus
2076 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2077 overload-resolution off} to disable overload resolution;
2078 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2080 @cindex completion of structure field names
2081 @cindex structure field name completion
2082 @cindex completion of union field names
2083 @cindex union field name completion
2084 When completing in an expression which looks up a field in a
2085 structure, @value{GDBN} also tries@footnote{The completer can be
2086 confused by certain kinds of invalid expressions. Also, it only
2087 examines the static type of the expression, not the dynamic type.} to
2088 limit completions to the field names available in the type of the
2092 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2093 magic to_fputs to_rewind
2094 to_data to_isatty to_write
2095 to_delete to_put to_write_async_safe
2100 This is because the @code{gdb_stdout} is a variable of the type
2101 @code{struct ui_file} that is defined in @value{GDBN} sources as
2108 ui_file_flush_ftype *to_flush;
2109 ui_file_write_ftype *to_write;
2110 ui_file_write_async_safe_ftype *to_write_async_safe;
2111 ui_file_fputs_ftype *to_fputs;
2112 ui_file_read_ftype *to_read;
2113 ui_file_delete_ftype *to_delete;
2114 ui_file_isatty_ftype *to_isatty;
2115 ui_file_rewind_ftype *to_rewind;
2116 ui_file_put_ftype *to_put;
2121 @node Command Options
2122 @section Command options
2124 @cindex command options
2125 Some commands accept options starting with a leading dash. For
2126 example, @code{print -pretty}. Similarly to command names, you can
2127 abbreviate a @value{GDBN} option to the first few letters of the
2128 option name, if that abbreviation is unambiguous, and you can also use
2129 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2130 in an option (or to show you the alternatives available, if there is
2131 more than one possibility).
2133 @cindex command options, raw input
2134 Some commands take raw input as argument. For example, the print
2135 command processes arbitrary expressions in any of the languages
2136 supported by @value{GDBN}. With such commands, because raw input may
2137 start with a leading dash that would be confused with an option or any
2138 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2139 -pretty} or printing negative @code{p}?), if you specify any command
2140 option, then you must use a double-dash (@code{--}) delimiter to
2141 indicate the end of options.
2143 @cindex command options, boolean
2145 Some options are described as accepting an argument which can be
2146 either @code{on} or @code{off}. These are known as @dfn{boolean
2147 options}. Similarly to boolean settings commands---@code{on} and
2148 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2149 @code{enable} can also be used as ``true'' value, and any of @code{0},
2150 @code{no} and @code{disable} can also be used as ``false'' value. You
2151 can also omit a ``true'' value, as it is implied by default.
2153 For example, these are equivalent:
2156 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2157 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2160 You can discover the set of options some command accepts by completing
2161 on @code{-} after the command name. For example:
2164 (@value{GDBP}) print -@key{TAB}@key{TAB}
2165 -address -max-depth -object -static-members
2166 -array -memory-tag-violations -pretty -symbol
2167 -array-indexes -nibbles -raw-values -union
2168 -elements -null-stop -repeats -vtbl
2171 Completion will in some cases guide you with a suggestion of what kind
2172 of argument an option expects. For example:
2175 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2180 Here, the option expects a number (e.g., @code{100}), not literal
2181 @code{NUMBER}. Such metasyntactical arguments are always presented in
2184 (For more on using the @code{print} command, see @ref{Data, ,Examining
2188 @section Getting Help
2189 @cindex online documentation
2192 You can always ask @value{GDBN} itself for information on its commands,
2193 using the command @code{help}.
2196 @kindex h @r{(@code{help})}
2199 You can use @code{help} (abbreviated @code{h}) with no arguments to
2200 display a short list of named classes of commands:
2204 List of classes of commands:
2206 aliases -- User-defined aliases of other commands
2207 breakpoints -- Making program stop at certain points
2208 data -- Examining data
2209 files -- Specifying and examining files
2210 internals -- Maintenance commands
2211 obscure -- Obscure features
2212 running -- Running the program
2213 stack -- Examining the stack
2214 status -- Status inquiries
2215 support -- Support facilities
2216 tracepoints -- Tracing of program execution without
2217 stopping the program
2218 user-defined -- User-defined commands
2220 Type "help" followed by a class name for a list of
2221 commands in that class.
2222 Type "help" followed by command name for full
2224 Command name abbreviations are allowed if unambiguous.
2227 @c the above line break eliminates huge line overfull...
2229 @item help @var{class}
2230 Using one of the general help classes as an argument, you can get a
2231 list of the individual commands in that class. If a command has
2232 aliases, the aliases are given after the command name, separated by
2233 commas. If an alias has default arguments, the full definition of
2234 the alias is given after the first line.
2235 For example, here is the help display for the class @code{status}:
2238 (@value{GDBP}) help status
2243 @c Line break in "show" line falsifies real output, but needed
2244 @c to fit in smallbook page size.
2245 info, inf, i -- Generic command for showing things
2246 about the program being debugged
2247 info address, iamain -- Describe where symbol SYM is stored.
2248 alias iamain = info address main
2249 info all-registers -- List of all registers and their contents,
2250 for selected stack frame.
2252 show, info set -- Generic command for showing things
2255 Type "help" followed by command name for full
2257 Command name abbreviations are allowed if unambiguous.
2261 @item help @var{command}
2262 With a command name as @code{help} argument, @value{GDBN} displays a
2263 short paragraph on how to use that command. If that command has
2264 one or more aliases, @value{GDBN} will display a first line with
2265 the command name and all its aliases separated by commas.
2266 This first line will be followed by the full definition of all aliases
2267 having default arguments.
2270 @item apropos [-v] @var{regexp}
2271 The @code{apropos} command searches through all of the @value{GDBN}
2272 commands, and their documentation, for the regular expression specified in
2273 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2274 which stands for @samp{verbose}, indicates to output the full documentation
2275 of the matching commands and highlight the parts of the documentation
2276 matching @var{regexp}. For example:
2287 alias -- Define a new command that is an alias of an existing command
2288 aliases -- User-defined aliases of other commands
2296 apropos -v cut.*thread apply
2300 results in the below output, where @samp{cut for 'thread apply}
2301 is highlighted if styling is enabled.
2305 taas -- Apply a command to all threads (ignoring errors
2308 shortcut for 'thread apply all -s COMMAND'
2310 tfaas -- Apply a command to all frames of all threads
2311 (ignoring errors and empty output).
2312 Usage: tfaas COMMAND
2313 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2318 @item complete @var{args}
2319 The @code{complete @var{args}} command lists all the possible completions
2320 for the beginning of a command. Use @var{args} to specify the beginning of the
2321 command you want completed. For example:
2327 @noindent results in:
2338 @noindent This is intended for use by @sc{gnu} Emacs.
2341 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2342 and @code{show} to inquire about the state of your program, or the state
2343 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2344 manual introduces each of them in the appropriate context. The listings
2345 under @code{info} and under @code{show} in the Command, Variable, and
2346 Function Index point to all the sub-commands. @xref{Command and Variable
2352 @kindex i @r{(@code{info})}
2354 This command (abbreviated @code{i}) is for describing the state of your
2355 program. For example, you can show the arguments passed to a function
2356 with @code{info args}, list the registers currently in use with @code{info
2357 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2358 You can get a complete list of the @code{info} sub-commands with
2359 @w{@code{help info}}.
2363 You can assign the result of an expression to an environment variable with
2364 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2365 @code{set prompt $}.
2369 In contrast to @code{info}, @code{show} is for describing the state of
2370 @value{GDBN} itself.
2371 You can change most of the things you can @code{show}, by using the
2372 related command @code{set}; for example, you can control what number
2373 system is used for displays with @code{set radix}, or simply inquire
2374 which is currently in use with @code{show radix}.
2377 To display all the settable parameters and their current
2378 values, you can use @code{show} with no arguments; you may also use
2379 @code{info set}. Both commands produce the same display.
2380 @c FIXME: "info set" violates the rule that "info" is for state of
2381 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2382 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2386 Here are several miscellaneous @code{show} subcommands, all of which are
2387 exceptional in lacking corresponding @code{set} commands:
2390 @kindex show version
2391 @cindex @value{GDBN} version number
2393 Show what version of @value{GDBN} is running. You should include this
2394 information in @value{GDBN} bug-reports. If multiple versions of
2395 @value{GDBN} are in use at your site, you may need to determine which
2396 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2397 commands are introduced, and old ones may wither away. Also, many
2398 system vendors ship variant versions of @value{GDBN}, and there are
2399 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2400 The version number is the same as the one announced when you start
2403 @kindex show copying
2404 @kindex info copying
2405 @cindex display @value{GDBN} copyright
2408 Display information about permission for copying @value{GDBN}.
2410 @kindex show warranty
2411 @kindex info warranty
2413 @itemx info warranty
2414 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2415 if your version of @value{GDBN} comes with one.
2417 @kindex show configuration
2418 @item show configuration
2419 Display detailed information about the way @value{GDBN} was configured
2420 when it was built. This displays the optional arguments passed to the
2421 @file{configure} script and also configuration parameters detected
2422 automatically by @command{configure}. When reporting a @value{GDBN}
2423 bug (@pxref{GDB Bugs}), it is important to include this information in
2429 @chapter Running Programs Under @value{GDBN}
2431 When you run a program under @value{GDBN}, you must first generate
2432 debugging information when you compile it.
2434 You may start @value{GDBN} with its arguments, if any, in an environment
2435 of your choice. If you are doing native debugging, you may redirect
2436 your program's input and output, debug an already running process, or
2437 kill a child process.
2440 * Compilation:: Compiling for debugging
2441 * Starting:: Starting your program
2442 * Arguments:: Your program's arguments
2443 * Environment:: Your program's environment
2445 * Working Directory:: Your program's working directory
2446 * Input/Output:: Your program's input and output
2447 * Attach:: Debugging an already-running process
2448 * Kill Process:: Killing the child process
2449 * Inferiors Connections and Programs:: Debugging multiple inferiors
2450 connections and programs
2451 * Threads:: Debugging programs with multiple threads
2452 * Forks:: Debugging forks
2453 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2457 @section Compiling for Debugging
2459 In order to debug a program effectively, you need to generate
2460 debugging information when you compile it. This debugging information
2461 is stored in the object file; it describes the data type of each
2462 variable or function and the correspondence between source line numbers
2463 and addresses in the executable code.
2465 To request debugging information, specify the @samp{-g} option when you run
2468 Programs that are to be shipped to your customers are compiled with
2469 optimizations, using the @samp{-O} compiler option. However, some
2470 compilers are unable to handle the @samp{-g} and @samp{-O} options
2471 together. Using those compilers, you cannot generate optimized
2472 executables containing debugging information.
2474 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2475 without @samp{-O}, making it possible to debug optimized code. We
2476 recommend that you @emph{always} use @samp{-g} whenever you compile a
2477 program. You may think your program is correct, but there is no sense
2478 in pushing your luck. For more information, see @ref{Optimized Code}.
2480 Older versions of the @sc{gnu} C compiler permitted a variant option
2481 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2482 format; if your @sc{gnu} C compiler has this option, do not use it.
2484 @value{GDBN} knows about preprocessor macros and can show you their
2485 expansion (@pxref{Macros}). Most compilers do not include information
2486 about preprocessor macros in the debugging information if you specify
2487 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2488 the @sc{gnu} C compiler, provides macro information if you are using
2489 the DWARF debugging format, and specify the option @option{-g3}.
2491 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2492 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2493 information on @value{NGCC} options affecting debug information.
2495 You will have the best debugging experience if you use the latest
2496 version of the DWARF debugging format that your compiler supports.
2497 DWARF is currently the most expressive and best supported debugging
2498 format in @value{GDBN}.
2502 @section Starting your Program
2508 @kindex r @r{(@code{run})}
2511 Use the @code{run} command to start your program under @value{GDBN}.
2512 You must first specify the program name with an argument to
2513 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2514 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2515 command (@pxref{Files, ,Commands to Specify Files}).
2519 If you are running your program in an execution environment that
2520 supports processes, @code{run} creates an inferior process and makes
2521 that process run your program. In some environments without processes,
2522 @code{run} jumps to the start of your program. Other targets,
2523 like @samp{remote}, are always running. If you get an error
2524 message like this one:
2527 The "remote" target does not support "run".
2528 Try "help target" or "continue".
2532 then use @code{continue} to run your program. You may need @code{load}
2533 first (@pxref{load}).
2535 The execution of a program is affected by certain information it
2536 receives from its superior. @value{GDBN} provides ways to specify this
2537 information, which you must do @emph{before} starting your program. (You
2538 can change it after starting your program, but such changes only affect
2539 your program the next time you start it.) This information may be
2540 divided into four categories:
2543 @item The @emph{arguments.}
2544 Specify the arguments to give your program as the arguments of the
2545 @code{run} command. If a shell is available on your target, the shell
2546 is used to pass the arguments, so that you may use normal conventions
2547 (such as wildcard expansion or variable substitution) in describing
2549 In Unix systems, you can control which shell is used with the
2550 @env{SHELL} environment variable. If you do not define @env{SHELL},
2551 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2552 use of any shell with the @code{set startup-with-shell} command (see
2555 @item The @emph{environment.}
2556 Your program normally inherits its environment from @value{GDBN}, but you can
2557 use the @value{GDBN} commands @code{set environment} and @code{unset
2558 environment} to change parts of the environment that affect
2559 your program. @xref{Environment, ,Your Program's Environment}.
2561 @item The @emph{working directory.}
2562 You can set your program's working directory with the command
2563 @kbd{set cwd}. If you do not set any working directory with this
2564 command, your program will inherit @value{GDBN}'s working directory if
2565 native debugging, or the remote server's working directory if remote
2566 debugging. @xref{Working Directory, ,Your Program's Working
2569 @item The @emph{standard input and output.}
2570 Your program normally uses the same device for standard input and
2571 standard output as @value{GDBN} is using. You can redirect input and output
2572 in the @code{run} command line, or you can use the @code{tty} command to
2573 set a different device for your program.
2574 @xref{Input/Output, ,Your Program's Input and Output}.
2577 @emph{Warning:} While input and output redirection work, you cannot use
2578 pipes to pass the output of the program you are debugging to another
2579 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2583 When you issue the @code{run} command, your program begins to execute
2584 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2585 of how to arrange for your program to stop. Once your program has
2586 stopped, you may call functions in your program, using the @code{print}
2587 or @code{call} commands. @xref{Data, ,Examining Data}.
2589 If the modification time of your symbol file has changed since the last
2590 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2591 table, and reads it again. When it does this, @value{GDBN} tries to retain
2592 your current breakpoints.
2597 @cindex run to main procedure
2598 The name of the main procedure can vary from language to language.
2599 With C or C@t{++}, the main procedure name is always @code{main}, but
2600 other languages such as Ada do not require a specific name for their
2601 main procedure. The debugger provides a convenient way to start the
2602 execution of the program and to stop at the beginning of the main
2603 procedure, depending on the language used.
2605 The @samp{start} command does the equivalent of setting a temporary
2606 breakpoint at the beginning of the main procedure and then invoking
2607 the @samp{run} command.
2609 @cindex elaboration phase
2610 Some programs contain an @dfn{elaboration} phase where some startup code is
2611 executed before the main procedure is called. This depends on the
2612 languages used to write your program. In C@t{++}, for instance,
2613 constructors for static and global objects are executed before
2614 @code{main} is called. It is therefore possible that the debugger stops
2615 before reaching the main procedure. However, the temporary breakpoint
2616 will remain to halt execution.
2618 Specify the arguments to give to your program as arguments to the
2619 @samp{start} command. These arguments will be given verbatim to the
2620 underlying @samp{run} command. Note that the same arguments will be
2621 reused if no argument is provided during subsequent calls to
2622 @samp{start} or @samp{run}.
2624 It is sometimes necessary to debug the program during elaboration. In
2625 these cases, using the @code{start} command would stop the execution
2626 of your program too late, as the program would have already completed
2627 the elaboration phase. Under these circumstances, either insert
2628 breakpoints in your elaboration code before running your program or
2629 use the @code{starti} command.
2633 @cindex run to first instruction
2634 The @samp{starti} command does the equivalent of setting a temporary
2635 breakpoint at the first instruction of a program's execution and then
2636 invoking the @samp{run} command. For programs containing an
2637 elaboration phase, the @code{starti} command will stop execution at
2638 the start of the elaboration phase.
2640 @anchor{set exec-wrapper}
2641 @kindex set exec-wrapper
2642 @item set exec-wrapper @var{wrapper}
2643 @itemx show exec-wrapper
2644 @itemx unset exec-wrapper
2645 When @samp{exec-wrapper} is set, the specified wrapper is used to
2646 launch programs for debugging. @value{GDBN} starts your program
2647 with a shell command of the form @kbd{exec @var{wrapper}
2648 @var{program}}. Quoting is added to @var{program} and its
2649 arguments, but not to @var{wrapper}, so you should add quotes if
2650 appropriate for your shell. The wrapper runs until it executes
2651 your program, and then @value{GDBN} takes control.
2653 You can use any program that eventually calls @code{execve} with
2654 its arguments as a wrapper. Several standard Unix utilities do
2655 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2656 with @code{exec "$@@"} will also work.
2658 For example, you can use @code{env} to pass an environment variable to
2659 the debugged program, without setting the variable in your shell's
2663 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2667 This command is available when debugging locally on most targets, excluding
2668 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2670 @kindex set startup-with-shell
2671 @anchor{set startup-with-shell}
2672 @item set startup-with-shell
2673 @itemx set startup-with-shell on
2674 @itemx set startup-with-shell off
2675 @itemx show startup-with-shell
2676 On Unix systems, by default, if a shell is available on your target,
2677 @value{GDBN}) uses it to start your program. Arguments of the
2678 @code{run} command are passed to the shell, which does variable
2679 substitution, expands wildcard characters and performs redirection of
2680 I/O. In some circumstances, it may be useful to disable such use of a
2681 shell, for example, when debugging the shell itself or diagnosing
2682 startup failures such as:
2686 Starting program: ./a.out
2687 During startup program terminated with signal SIGSEGV, Segmentation fault.
2691 which indicates the shell or the wrapper specified with
2692 @samp{exec-wrapper} crashed, not your program. Most often, this is
2693 caused by something odd in your shell's non-interactive mode
2694 initialization file---such as @file{.cshrc} for C-shell,
2695 $@file{.zshenv} for the Z shell, or the file specified in the
2696 @env{BASH_ENV} environment variable for BASH.
2698 @anchor{set auto-connect-native-target}
2699 @kindex set auto-connect-native-target
2700 @item set auto-connect-native-target
2701 @itemx set auto-connect-native-target on
2702 @itemx set auto-connect-native-target off
2703 @itemx show auto-connect-native-target
2705 By default, if the current inferior is not connected to any target yet
2706 (e.g., with @code{target remote}), the @code{run} command starts your
2707 program as a native process under @value{GDBN}, on your local machine.
2708 If you're sure you don't want to debug programs on your local machine,
2709 you can tell @value{GDBN} to not connect to the native target
2710 automatically with the @code{set auto-connect-native-target off}
2713 If @code{on}, which is the default, and if the current inferior is not
2714 connected to a target already, the @code{run} command automaticaly
2715 connects to the native target, if one is available.
2717 If @code{off}, and if the current inferior is not connected to a
2718 target already, the @code{run} command fails with an error:
2722 Don't know how to run. Try "help target".
2725 If the current inferior is already connected to a target, @value{GDBN}
2726 always uses it with the @code{run} command.
2728 In any case, you can explicitly connect to the native target with the
2729 @code{target native} command. For example,
2732 (@value{GDBP}) set auto-connect-native-target off
2734 Don't know how to run. Try "help target".
2735 (@value{GDBP}) target native
2737 Starting program: ./a.out
2738 [Inferior 1 (process 10421) exited normally]
2741 In case you connected explicitly to the @code{native} target,
2742 @value{GDBN} remains connected even if all inferiors exit, ready for
2743 the next @code{run} command. Use the @code{disconnect} command to
2746 Examples of other commands that likewise respect the
2747 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2748 proc}, @code{info os}.
2750 @kindex set disable-randomization
2751 @item set disable-randomization
2752 @itemx set disable-randomization on
2753 This option (enabled by default in @value{GDBN}) will turn off the native
2754 randomization of the virtual address space of the started program. This option
2755 is useful for multiple debugging sessions to make the execution better
2756 reproducible and memory addresses reusable across debugging sessions.
2758 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2759 On @sc{gnu}/Linux you can get the same behavior using
2762 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2765 @item set disable-randomization off
2766 Leave the behavior of the started executable unchanged. Some bugs rear their
2767 ugly heads only when the program is loaded at certain addresses. If your bug
2768 disappears when you run the program under @value{GDBN}, that might be because
2769 @value{GDBN} by default disables the address randomization on platforms, such
2770 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2771 disable-randomization off} to try to reproduce such elusive bugs.
2773 On targets where it is available, virtual address space randomization
2774 protects the programs against certain kinds of security attacks. In these
2775 cases the attacker needs to know the exact location of a concrete executable
2776 code. Randomizing its location makes it impossible to inject jumps misusing
2777 a code at its expected addresses.
2779 Prelinking shared libraries provides a startup performance advantage but it
2780 makes addresses in these libraries predictable for privileged processes by
2781 having just unprivileged access at the target system. Reading the shared
2782 library binary gives enough information for assembling the malicious code
2783 misusing it. Still even a prelinked shared library can get loaded at a new
2784 random address just requiring the regular relocation process during the
2785 startup. Shared libraries not already prelinked are always loaded at
2786 a randomly chosen address.
2788 Position independent executables (PIE) contain position independent code
2789 similar to the shared libraries and therefore such executables get loaded at
2790 a randomly chosen address upon startup. PIE executables always load even
2791 already prelinked shared libraries at a random address. You can build such
2792 executable using @command{gcc -fPIE -pie}.
2794 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2795 (as long as the randomization is enabled).
2797 @item show disable-randomization
2798 Show the current setting of the explicit disable of the native randomization of
2799 the virtual address space of the started program.
2804 @section Your Program's Arguments
2806 @cindex arguments (to your program)
2807 The arguments to your program can be specified by the arguments of the
2809 They are passed to a shell, which expands wildcard characters and
2810 performs redirection of I/O, and thence to your program. Your
2811 @env{SHELL} environment variable (if it exists) specifies what shell
2812 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2813 the default shell (@file{/bin/sh} on Unix).
2815 On non-Unix systems, the program is usually invoked directly by
2816 @value{GDBN}, which emulates I/O redirection via the appropriate system
2817 calls, and the wildcard characters are expanded by the startup code of
2818 the program, not by the shell.
2820 @code{run} with no arguments uses the same arguments used by the previous
2821 @code{run}, or those set by the @code{set args} command.
2826 Specify the arguments to be used the next time your program is run. If
2827 @code{set args} has no arguments, @code{run} executes your program
2828 with no arguments. Once you have run your program with arguments,
2829 using @code{set args} before the next @code{run} is the only way to run
2830 it again without arguments.
2834 Show the arguments to give your program when it is started.
2838 @section Your Program's Environment
2840 @cindex environment (of your program)
2841 The @dfn{environment} consists of a set of environment variables and
2842 their values. Environment variables conventionally record such things as
2843 your user name, your home directory, your terminal type, and your search
2844 path for programs to run. Usually you set up environment variables with
2845 the shell and they are inherited by all the other programs you run. When
2846 debugging, it can be useful to try running your program with a modified
2847 environment without having to start @value{GDBN} over again.
2851 @item path @var{directory}
2852 Add @var{directory} to the front of the @env{PATH} environment variable
2853 (the search path for executables) that will be passed to your program.
2854 The value of @env{PATH} used by @value{GDBN} does not change.
2855 You may specify several directory names, separated by whitespace or by a
2856 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2857 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2858 is moved to the front, so it is searched sooner.
2860 You can use the string @samp{$cwd} to refer to whatever is the current
2861 working directory at the time @value{GDBN} searches the path. If you
2862 use @samp{.} instead, it refers to the directory where you executed the
2863 @code{path} command. @value{GDBN} replaces @samp{.} in the
2864 @var{directory} argument (with the current path) before adding
2865 @var{directory} to the search path.
2866 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2867 @c document that, since repeating it would be a no-op.
2871 Display the list of search paths for executables (the @env{PATH}
2872 environment variable).
2874 @kindex show environment
2875 @item show environment @r{[}@var{varname}@r{]}
2876 Print the value of environment variable @var{varname} to be given to
2877 your program when it starts. If you do not supply @var{varname},
2878 print the names and values of all environment variables to be given to
2879 your program. You can abbreviate @code{environment} as @code{env}.
2881 @kindex set environment
2882 @anchor{set environment}
2883 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2884 Set environment variable @var{varname} to @var{value}. The value
2885 changes for your program (and the shell @value{GDBN} uses to launch
2886 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2887 values of environment variables are just strings, and any
2888 interpretation is supplied by your program itself. The @var{value}
2889 parameter is optional; if it is eliminated, the variable is set to a
2891 @c "any string" here does not include leading, trailing
2892 @c blanks. Gnu asks: does anyone care?
2894 For example, this command:
2901 tells the debugged program, when subsequently run, that its user is named
2902 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2903 are not actually required.)
2905 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2906 which also inherits the environment set with @code{set environment}.
2907 If necessary, you can avoid that by using the @samp{env} program as a
2908 wrapper instead of using @code{set environment}. @xref{set
2909 exec-wrapper}, for an example doing just that.
2911 Environment variables that are set by the user are also transmitted to
2912 @command{gdbserver} to be used when starting the remote inferior.
2913 @pxref{QEnvironmentHexEncoded}.
2915 @kindex unset environment
2916 @anchor{unset environment}
2917 @item unset environment @var{varname}
2918 Remove variable @var{varname} from the environment to be passed to your
2919 program. This is different from @samp{set env @var{varname} =};
2920 @code{unset environment} removes the variable from the environment,
2921 rather than assigning it an empty value.
2923 Environment variables that are unset by the user are also unset on
2924 @command{gdbserver} when starting the remote inferior.
2925 @pxref{QEnvironmentUnset}.
2928 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2929 the shell indicated by your @env{SHELL} environment variable if it
2930 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2931 names a shell that runs an initialization file when started
2932 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2933 for the Z shell, or the file specified in the @env{BASH_ENV}
2934 environment variable for BASH---any variables you set in that file
2935 affect your program. You may wish to move setting of environment
2936 variables to files that are only run when you sign on, such as
2937 @file{.login} or @file{.profile}.
2939 @node Working Directory
2940 @section Your Program's Working Directory
2942 @cindex working directory (of your program)
2943 Each time you start your program with @code{run}, the inferior will be
2944 initialized with the current working directory specified by the
2945 @kbd{set cwd} command. If no directory has been specified by this
2946 command, then the inferior will inherit @value{GDBN}'s current working
2947 directory as its working directory if native debugging, or it will
2948 inherit the remote server's current working directory if remote
2953 @cindex change inferior's working directory
2954 @anchor{set cwd command}
2955 @item set cwd @r{[}@var{directory}@r{]}
2956 Set the inferior's working directory to @var{directory}, which will be
2957 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2958 argument has been specified, the command clears the setting and resets
2959 it to an empty state. This setting has no effect on @value{GDBN}'s
2960 working directory, and it only takes effect the next time you start
2961 the inferior. The @file{~} in @var{directory} is a short for the
2962 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2963 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2964 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2967 You can also change @value{GDBN}'s current working directory by using
2968 the @code{cd} command.
2972 @cindex show inferior's working directory
2974 Show the inferior's working directory. If no directory has been
2975 specified by @kbd{set cwd}, then the default inferior's working
2976 directory is the same as @value{GDBN}'s working directory.
2979 @cindex change @value{GDBN}'s working directory
2981 @item cd @r{[}@var{directory}@r{]}
2982 Set the @value{GDBN} working directory to @var{directory}. If not
2983 given, @var{directory} uses @file{'~'}.
2985 The @value{GDBN} working directory serves as a default for the
2986 commands that specify files for @value{GDBN} to operate on.
2987 @xref{Files, ,Commands to Specify Files}.
2988 @xref{set cwd command}.
2992 Print the @value{GDBN} working directory.
2995 It is generally impossible to find the current working directory of
2996 the process being debugged (since a program can change its directory
2997 during its run). If you work on a system where @value{GDBN} supports
2998 the @code{info proc} command (@pxref{Process Information}), you can
2999 use the @code{info proc} command to find out the
3000 current working directory of the debuggee.
3003 @section Your Program's Input and Output
3008 By default, the program you run under @value{GDBN} does input and output to
3009 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3010 to its own terminal modes to interact with you, but it records the terminal
3011 modes your program was using and switches back to them when you continue
3012 running your program.
3015 @kindex info terminal
3017 Displays information recorded by @value{GDBN} about the terminal modes your
3021 You can redirect your program's input and/or output using shell
3022 redirection with the @code{run} command. For example,
3029 starts your program, diverting its output to the file @file{outfile}.
3032 @cindex controlling terminal
3033 Another way to specify where your program should do input and output is
3034 with the @code{tty} command. This command accepts a file name as
3035 argument, and causes this file to be the default for future @code{run}
3036 commands. It also resets the controlling terminal for the child
3037 process, for future @code{run} commands. For example,
3044 directs that processes started with subsequent @code{run} commands
3045 default to do input and output on the terminal @file{/dev/ttyb} and have
3046 that as their controlling terminal.
3048 An explicit redirection in @code{run} overrides the @code{tty} command's
3049 effect on the input/output device, but not its effect on the controlling
3052 When you use the @code{tty} command or redirect input in the @code{run}
3053 command, only the input @emph{for your program} is affected. The input
3054 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3055 for @code{set inferior-tty}.
3057 @cindex inferior tty
3058 @cindex set inferior controlling terminal
3059 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3060 display the name of the terminal that will be used for future runs of your
3064 @item set inferior-tty [ @var{tty} ]
3065 @kindex set inferior-tty
3066 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3067 restores the default behavior, which is to use the same terminal as
3070 @item show inferior-tty
3071 @kindex show inferior-tty
3072 Show the current tty for the program being debugged.
3076 @section Debugging an Already-running Process
3081 @item attach @var{process-id}
3082 This command attaches to a running process---one that was started
3083 outside @value{GDBN}. (@code{info files} shows your active
3084 targets.) The command takes as argument a process ID. The usual way to
3085 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3086 or with the @samp{jobs -l} shell command.
3088 @code{attach} does not repeat if you press @key{RET} a second time after
3089 executing the command.
3092 To use @code{attach}, your program must be running in an environment
3093 which supports processes; for example, @code{attach} does not work for
3094 programs on bare-board targets that lack an operating system. You must
3095 also have permission to send the process a signal.
3097 When you use @code{attach}, the debugger finds the program running in
3098 the process first by looking in the current working directory, then (if
3099 the program is not found) by using the source file search path
3100 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3101 the @code{file} command to load the program. @xref{Files, ,Commands to
3104 @anchor{set exec-file-mismatch}
3105 If the debugger can determine that the executable file running in the
3106 process it is attaching to does not match the current exec-file loaded
3107 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3108 handle the mismatch. @value{GDBN} tries to compare the files by
3109 comparing their build IDs (@pxref{build ID}), if available.
3112 @kindex exec-file-mismatch
3113 @cindex set exec-file-mismatch
3114 @item set exec-file-mismatch @samp{ask|warn|off}
3116 Whether to detect mismatch between the current executable file loaded
3117 by @value{GDBN} and the executable file used to start the process. If
3118 @samp{ask}, the default, display a warning and ask the user whether to
3119 load the process executable file; if @samp{warn}, just display a
3120 warning; if @samp{off}, don't attempt to detect a mismatch.
3121 If the user confirms loading the process executable file, then its symbols
3122 will be loaded as well.
3124 @cindex show exec-file-mismatch
3125 @item show exec-file-mismatch
3126 Show the current value of @code{exec-file-mismatch}.
3130 The first thing @value{GDBN} does after arranging to debug the specified
3131 process is to stop it. You can examine and modify an attached process
3132 with all the @value{GDBN} commands that are ordinarily available when
3133 you start processes with @code{run}. You can insert breakpoints; you
3134 can step and continue; you can modify storage. If you would rather the
3135 process continue running, you may use the @code{continue} command after
3136 attaching @value{GDBN} to the process.
3141 When you have finished debugging the attached process, you can use the
3142 @code{detach} command to release it from @value{GDBN} control. Detaching
3143 the process continues its execution. After the @code{detach} command,
3144 that process and @value{GDBN} become completely independent once more, and you
3145 are ready to @code{attach} another process or start one with @code{run}.
3146 @code{detach} does not repeat if you press @key{RET} again after
3147 executing the command.
3150 If you exit @value{GDBN} while you have an attached process, you detach
3151 that process. If you use the @code{run} command, you kill that process.
3152 By default, @value{GDBN} asks for confirmation if you try to do either of these
3153 things; you can control whether or not you need to confirm by using the
3154 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3158 @section Killing the Child Process
3163 Kill the child process in which your program is running under @value{GDBN}.
3166 This command is useful if you wish to debug a core dump instead of a
3167 running process. @value{GDBN} ignores any core dump file while your program
3170 On some operating systems, a program cannot be executed outside @value{GDBN}
3171 while you have breakpoints set on it inside @value{GDBN}. You can use the
3172 @code{kill} command in this situation to permit running your program
3173 outside the debugger.
3175 The @code{kill} command is also useful if you wish to recompile and
3176 relink your program, since on many systems it is impossible to modify an
3177 executable file while it is running in a process. In this case, when you
3178 next type @code{run}, @value{GDBN} notices that the file has changed, and
3179 reads the symbol table again (while trying to preserve your current
3180 breakpoint settings).
3182 @node Inferiors Connections and Programs
3183 @section Debugging Multiple Inferiors Connections and Programs
3185 @value{GDBN} lets you run and debug multiple programs in a single
3186 session. In addition, @value{GDBN} on some systems may let you run
3187 several programs simultaneously (otherwise you have to exit from one
3188 before starting another). On some systems @value{GDBN} may even let
3189 you debug several programs simultaneously on different remote systems.
3190 In the most general case, you can have multiple threads of execution
3191 in each of multiple processes, launched from multiple executables,
3192 running on different machines.
3195 @value{GDBN} represents the state of each program execution with an
3196 object called an @dfn{inferior}. An inferior typically corresponds to
3197 a process, but is more general and applies also to targets that do not
3198 have processes. Inferiors may be created before a process runs, and
3199 may be retained after a process exits. Inferiors have unique
3200 identifiers that are different from process ids. Usually each
3201 inferior will also have its own distinct address space, although some
3202 embedded targets may have several inferiors running in different parts
3203 of a single address space. Each inferior may in turn have multiple
3204 threads running in it.
3206 To find out what inferiors exist at any moment, use @w{@code{info
3210 @kindex info inferiors [ @var{id}@dots{} ]
3211 @item info inferiors
3212 Print a list of all inferiors currently being managed by @value{GDBN}.
3213 By default all inferiors are printed, but the argument @var{id}@dots{}
3214 -- a space separated list of inferior numbers -- can be used to limit
3215 the display to just the requested inferiors.
3217 @value{GDBN} displays for each inferior (in this order):
3221 the inferior number assigned by @value{GDBN}
3224 the target system's inferior identifier
3227 the target connection the inferior is bound to, including the unique
3228 connection number assigned by @value{GDBN}, and the protocol used by
3232 the name of the executable the inferior is running.
3237 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3238 indicates the current inferior.
3242 @c end table here to get a little more width for example
3245 (@value{GDBP}) info inferiors
3246 Num Description Connection Executable
3247 * 1 process 3401 1 (native) goodbye
3248 2 process 2307 2 (extended-remote host:10000) hello
3251 To get informations about the current inferior, use @code{inferior}:
3256 Shows information about the current inferior.
3260 @c end table here to get a little more width for example
3263 (@value{GDBP}) inferior
3264 [Current inferior is 1 [process 3401] (helloworld)]
3267 To find out what open target connections exist at any moment, use
3268 @w{@code{info connections}}:
3271 @kindex info connections [ @var{id}@dots{} ]
3272 @item info connections
3273 Print a list of all open target connections currently being managed by
3274 @value{GDBN}. By default all connections are printed, but the
3275 argument @var{id}@dots{} -- a space separated list of connections
3276 numbers -- can be used to limit the display to just the requested
3279 @value{GDBN} displays for each connection (in this order):
3283 the connection number assigned by @value{GDBN}.
3286 the protocol used by the connection.
3289 a textual description of the protocol used by the connection.
3294 An asterisk @samp{*} preceding the connection number indicates the
3295 connection of the current inferior.
3299 @c end table here to get a little more width for example
3302 (@value{GDBP}) info connections
3303 Num What Description
3304 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3305 2 native Native process
3306 3 core Local core dump file
3309 To switch focus between inferiors, use the @code{inferior} command:
3312 @kindex inferior @var{infno}
3313 @item inferior @var{infno}
3314 Make inferior number @var{infno} the current inferior. The argument
3315 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3316 in the first field of the @samp{info inferiors} display.
3319 @vindex $_inferior@r{, convenience variable}
3320 The debugger convenience variable @samp{$_inferior} contains the
3321 number of the current inferior. You may find this useful in writing
3322 breakpoint conditional expressions, command scripts, and so forth.
3323 @xref{Convenience Vars,, Convenience Variables}, for general
3324 information on convenience variables.
3326 You can get multiple executables into a debugging session via the
3327 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3328 systems @value{GDBN} can add inferiors to the debug session
3329 automatically by following calls to @code{fork} and @code{exec}. To
3330 remove inferiors from the debugging session use the
3331 @w{@code{remove-inferiors}} command.
3334 @anchor{add_inferior_cli}
3335 @kindex add-inferior
3336 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3337 Adds @var{n} inferiors to be run using @var{executable} as the
3338 executable; @var{n} defaults to 1. If no executable is specified,
3339 the inferiors begins empty, with no program. You can still assign or
3340 change the program assigned to the inferior at any time by using the
3341 @code{file} command with the executable name as its argument.
3343 By default, the new inferior begins connected to the same target
3344 connection as the current inferior. For example, if the current
3345 inferior was connected to @code{gdbserver} with @code{target remote},
3346 then the new inferior will be connected to the same @code{gdbserver}
3347 instance. The @samp{-no-connection} option starts the new inferior
3348 with no connection yet. You can then for example use the @code{target
3349 remote} command to connect to some other @code{gdbserver} instance,
3350 use @code{run} to spawn a local program, etc.
3352 @kindex clone-inferior
3353 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3354 Adds @var{n} inferiors ready to execute the same program as inferior
3355 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3356 number of the current inferior. This command copies the values of the
3357 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3358 current inferior to the new one. It also propagates changes the user
3359 made to environment variables using the @w{@code{set environment}} and
3360 @w{@code{unset environment}} commands. This is a convenient command
3361 when you want to run another instance of the inferior you are debugging.
3364 (@value{GDBP}) info inferiors
3365 Num Description Connection Executable
3366 * 1 process 29964 1 (native) helloworld
3367 (@value{GDBP}) clone-inferior
3370 (@value{GDBP}) info inferiors
3371 Num Description Connection Executable
3372 * 1 process 29964 1 (native) helloworld
3373 2 <null> 1 (native) helloworld
3376 You can now simply switch focus to inferior 2 and run it.
3378 @kindex remove-inferiors
3379 @item remove-inferiors @var{infno}@dots{}
3380 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3381 possible to remove an inferior that is running with this command. For
3382 those, use the @code{kill} or @code{detach} command first.
3386 To quit debugging one of the running inferiors that is not the current
3387 inferior, you can either detach from it by using the @w{@code{detach
3388 inferior}} command (allowing it to run independently), or kill it
3389 using the @w{@code{kill inferiors}} command:
3392 @kindex detach inferiors @var{infno}@dots{}
3393 @item detach inferior @var{infno}@dots{}
3394 Detach from the inferior or inferiors identified by @value{GDBN}
3395 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3396 still stays on the list of inferiors shown by @code{info inferiors},
3397 but its Description will show @samp{<null>}.
3399 @kindex kill inferiors @var{infno}@dots{}
3400 @item kill inferiors @var{infno}@dots{}
3401 Kill the inferior or inferiors identified by @value{GDBN} inferior
3402 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3403 stays on the list of inferiors shown by @code{info inferiors}, but its
3404 Description will show @samp{<null>}.
3407 After the successful completion of a command such as @code{detach},
3408 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3409 a normal process exit, the inferior is still valid and listed with
3410 @code{info inferiors}, ready to be restarted.
3413 To be notified when inferiors are started or exit under @value{GDBN}'s
3414 control use @w{@code{set print inferior-events}}:
3417 @kindex set print inferior-events
3418 @cindex print messages on inferior start and exit
3419 @item set print inferior-events
3420 @itemx set print inferior-events on
3421 @itemx set print inferior-events off
3422 The @code{set print inferior-events} command allows you to enable or
3423 disable printing of messages when @value{GDBN} notices that new
3424 inferiors have started or that inferiors have exited or have been
3425 detached. By default, these messages will be printed.
3427 @kindex show print inferior-events
3428 @item show print inferior-events
3429 Show whether messages will be printed when @value{GDBN} detects that
3430 inferiors have started, exited or have been detached.
3433 Many commands will work the same with multiple programs as with a
3434 single program: e.g., @code{print myglobal} will simply display the
3435 value of @code{myglobal} in the current inferior.
3438 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3439 get more info about the relationship of inferiors, programs, address
3440 spaces in a debug session. You can do that with the @w{@code{maint
3441 info program-spaces}} command.
3444 @kindex maint info program-spaces
3445 @item maint info program-spaces
3446 Print a list of all program spaces currently being managed by
3449 @value{GDBN} displays for each program space (in this order):
3453 the program space number assigned by @value{GDBN}
3456 the name of the executable loaded into the program space, with e.g.,
3457 the @code{file} command.
3462 An asterisk @samp{*} preceding the @value{GDBN} program space number
3463 indicates the current program space.
3465 In addition, below each program space line, @value{GDBN} prints extra
3466 information that isn't suitable to display in tabular form. For
3467 example, the list of inferiors bound to the program space.
3470 (@value{GDBP}) maint info program-spaces
3474 Bound inferiors: ID 1 (process 21561)
3477 Here we can see that no inferior is running the program @code{hello},
3478 while @code{process 21561} is running the program @code{goodbye}. On
3479 some targets, it is possible that multiple inferiors are bound to the
3480 same program space. The most common example is that of debugging both
3481 the parent and child processes of a @code{vfork} call. For example,
3484 (@value{GDBP}) maint info program-spaces
3487 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3490 Here, both inferior 2 and inferior 1 are running in the same program
3491 space as a result of inferior 1 having executed a @code{vfork} call.
3495 @section Debugging Programs with Multiple Threads
3497 @cindex threads of execution
3498 @cindex multiple threads
3499 @cindex switching threads
3500 In some operating systems, such as GNU/Linux and Solaris, a single program
3501 may have more than one @dfn{thread} of execution. The precise semantics
3502 of threads differ from one operating system to another, but in general
3503 the threads of a single program are akin to multiple processes---except
3504 that they share one address space (that is, they can all examine and
3505 modify the same variables). On the other hand, each thread has its own
3506 registers and execution stack, and perhaps private memory.
3508 @value{GDBN} provides these facilities for debugging multi-thread
3512 @item automatic notification of new threads
3513 @item @samp{thread @var{thread-id}}, a command to switch among threads
3514 @item @samp{info threads}, a command to inquire about existing threads
3515 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3516 a command to apply a command to a list of threads
3517 @item thread-specific breakpoints
3518 @item @samp{set print thread-events}, which controls printing of
3519 messages on thread start and exit.
3520 @item @samp{set libthread-db-search-path @var{path}}, which lets
3521 the user specify which @code{libthread_db} to use if the default choice
3522 isn't compatible with the program.
3525 @cindex focus of debugging
3526 @cindex current thread
3527 The @value{GDBN} thread debugging facility allows you to observe all
3528 threads while your program runs---but whenever @value{GDBN} takes
3529 control, one thread in particular is always the focus of debugging.
3530 This thread is called the @dfn{current thread}. Debugging commands show
3531 program information from the perspective of the current thread.
3533 @cindex @code{New} @var{systag} message
3534 @cindex thread identifier (system)
3535 @c FIXME-implementors!! It would be more helpful if the [New...] message
3536 @c included GDB's numeric thread handle, so you could just go to that
3537 @c thread without first checking `info threads'.
3538 Whenever @value{GDBN} detects a new thread in your program, it displays
3539 the target system's identification for the thread with a message in the
3540 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3541 whose form varies depending on the particular system. For example, on
3542 @sc{gnu}/Linux, you might see
3545 [New Thread 0x41e02940 (LWP 25582)]
3549 when @value{GDBN} notices a new thread. In contrast, on other systems,
3550 the @var{systag} is simply something like @samp{process 368}, with no
3553 @c FIXME!! (1) Does the [New...] message appear even for the very first
3554 @c thread of a program, or does it only appear for the
3555 @c second---i.e.@: when it becomes obvious we have a multithread
3557 @c (2) *Is* there necessarily a first thread always? Or do some
3558 @c multithread systems permit starting a program with multiple
3559 @c threads ab initio?
3561 @anchor{thread numbers}
3562 @cindex thread number, per inferior
3563 @cindex thread identifier (GDB)
3564 For debugging purposes, @value{GDBN} associates its own thread number
3565 ---always a single integer---with each thread of an inferior. This
3566 number is unique between all threads of an inferior, but not unique
3567 between threads of different inferiors.
3569 @cindex qualified thread ID
3570 You can refer to a given thread in an inferior using the qualified
3571 @var{inferior-num}.@var{thread-num} syntax, also known as
3572 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3573 number and @var{thread-num} being the thread number of the given
3574 inferior. For example, thread @code{2.3} refers to thread number 3 of
3575 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3576 then @value{GDBN} infers you're referring to a thread of the current
3579 Until you create a second inferior, @value{GDBN} does not show the
3580 @var{inferior-num} part of thread IDs, even though you can always use
3581 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3582 of inferior 1, the initial inferior.
3584 @anchor{thread ID lists}
3585 @cindex thread ID lists
3586 Some commands accept a space-separated @dfn{thread ID list} as
3587 argument. A list element can be:
3591 A thread ID as shown in the first field of the @samp{info threads}
3592 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3596 A range of thread numbers, again with or without an inferior
3597 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3598 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3601 All threads of an inferior, specified with a star wildcard, with or
3602 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3603 @samp{1.*}) or @code{*}. The former refers to all threads of the
3604 given inferior, and the latter form without an inferior qualifier
3605 refers to all threads of the current inferior.
3609 For example, if the current inferior is 1, and inferior 7 has one
3610 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3611 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3612 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3613 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3617 @anchor{global thread numbers}
3618 @cindex global thread number
3619 @cindex global thread identifier (GDB)
3620 In addition to a @emph{per-inferior} number, each thread is also
3621 assigned a unique @emph{global} number, also known as @dfn{global
3622 thread ID}, a single integer. Unlike the thread number component of
3623 the thread ID, no two threads have the same global ID, even when
3624 you're debugging multiple inferiors.
3626 From @value{GDBN}'s perspective, a process always has at least one
3627 thread. In other words, @value{GDBN} assigns a thread number to the
3628 program's ``main thread'' even if the program is not multi-threaded.
3630 @vindex $_thread@r{, convenience variable}
3631 @vindex $_gthread@r{, convenience variable}
3632 The debugger convenience variables @samp{$_thread} and
3633 @samp{$_gthread} contain, respectively, the per-inferior thread number
3634 and the global thread number of the current thread. You may find this
3635 useful in writing breakpoint conditional expressions, command scripts,
3636 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3637 general information on convenience variables.
3639 If @value{GDBN} detects the program is multi-threaded, it augments the
3640 usual message about stopping at a breakpoint with the ID and name of
3641 the thread that hit the breakpoint.
3644 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3647 Likewise when the program receives a signal:
3650 Thread 1 "main" received signal SIGINT, Interrupt.
3654 @anchor{info_threads}
3655 @kindex info threads
3656 @item info threads @r{[}@var{thread-id-list}@r{]}
3658 Display information about one or more threads. With no arguments
3659 displays information about all threads. You can specify the list of
3660 threads that you want to display using the thread ID list syntax
3661 (@pxref{thread ID lists}).
3663 @value{GDBN} displays for each thread (in this order):
3667 the per-inferior thread number assigned by @value{GDBN}
3670 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3671 option was specified
3674 the target system's thread identifier (@var{systag})
3677 the thread's name, if one is known. A thread can either be named by
3678 the user (see @code{thread name}, below), or, in some cases, by the
3682 the current stack frame summary for that thread
3686 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3687 indicates the current thread.
3691 @c end table here to get a little more width for example
3694 (@value{GDBP}) info threads
3696 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3697 2 process 35 thread 23 0x34e5 in sigpause ()
3698 3 process 35 thread 27 0x34e5 in sigpause ()
3702 If you're debugging multiple inferiors, @value{GDBN} displays thread
3703 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3704 Otherwise, only @var{thread-num} is shown.
3706 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3707 indicating each thread's global thread ID:
3710 (@value{GDBP}) info threads
3711 Id GId Target Id Frame
3712 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3713 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3714 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3715 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3718 On Solaris, you can display more information about user threads with a
3719 Solaris-specific command:
3722 @item maint info sol-threads
3723 @kindex maint info sol-threads
3724 @cindex thread info (Solaris)
3725 Display info on Solaris user threads.
3729 @kindex thread @var{thread-id}
3730 @item thread @var{thread-id}
3731 Make thread ID @var{thread-id} the current thread. The command
3732 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3733 the first field of the @samp{info threads} display, with or without an
3734 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3736 @value{GDBN} responds by displaying the system identifier of the
3737 thread you selected, and its current stack frame summary:
3740 (@value{GDBP}) thread 2
3741 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3742 #0 some_function (ignore=0x0) at example.c:8
3743 8 printf ("hello\n");
3747 As with the @samp{[New @dots{}]} message, the form of the text after
3748 @samp{Switching to} depends on your system's conventions for identifying
3751 @anchor{thread apply all}
3752 @kindex thread apply
3753 @cindex apply command to several threads
3754 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3755 The @code{thread apply} command allows you to apply the named
3756 @var{command} to one or more threads. Specify the threads that you
3757 want affected using the thread ID list syntax (@pxref{thread ID
3758 lists}), or specify @code{all} to apply to all threads. To apply a
3759 command to all threads in descending order, type @kbd{thread apply all
3760 @var{command}}. To apply a command to all threads in ascending order,
3761 type @kbd{thread apply all -ascending @var{command}}.
3763 The @var{flag} arguments control what output to produce and how to handle
3764 errors raised when applying @var{command} to a thread. @var{flag}
3765 must start with a @code{-} directly followed by one letter in
3766 @code{qcs}. If several flags are provided, they must be given
3767 individually, such as @code{-c -q}.
3769 By default, @value{GDBN} displays some thread information before the
3770 output produced by @var{command}, and an error raised during the
3771 execution of a @var{command} will abort @code{thread apply}. The
3772 following flags can be used to fine-tune this behavior:
3776 The flag @code{-c}, which stands for @samp{continue}, causes any
3777 errors in @var{command} to be displayed, and the execution of
3778 @code{thread apply} then continues.
3780 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3781 or empty output produced by a @var{command} to be silently ignored.
3782 That is, the execution continues, but the thread information and errors
3785 The flag @code{-q} (@samp{quiet}) disables printing the thread
3789 Flags @code{-c} and @code{-s} cannot be used together.
3792 @cindex apply command to all threads (ignoring errors and empty output)
3793 @item taas [@var{option}]@dots{} @var{command}
3794 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3795 Applies @var{command} on all threads, ignoring errors and empty output.
3797 The @code{taas} command accepts the same options as the @code{thread
3798 apply all} command. @xref{thread apply all}.
3801 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3802 @item tfaas [@var{option}]@dots{} @var{command}
3803 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3804 Applies @var{command} on all frames of all threads, ignoring errors
3805 and empty output. Note that the flag @code{-s} is specified twice:
3806 The first @code{-s} ensures that @code{thread apply} only shows the thread
3807 information of the threads for which @code{frame apply} produces
3808 some output. The second @code{-s} is needed to ensure that @code{frame
3809 apply} shows the frame information of a frame only if the
3810 @var{command} successfully produced some output.
3812 It can for example be used to print a local variable or a function
3813 argument without knowing the thread or frame where this variable or argument
3816 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3819 The @code{tfaas} command accepts the same options as the @code{frame
3820 apply} command. @xref{Frame Apply,,frame apply}.
3823 @cindex name a thread
3824 @item thread name [@var{name}]
3825 This command assigns a name to the current thread. If no argument is
3826 given, any existing user-specified name is removed. The thread name
3827 appears in the @samp{info threads} display.
3829 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3830 determine the name of the thread as given by the OS. On these
3831 systems, a name specified with @samp{thread name} will override the
3832 system-give name, and removing the user-specified name will cause
3833 @value{GDBN} to once again display the system-specified name.
3836 @cindex search for a thread
3837 @item thread find [@var{regexp}]
3838 Search for and display thread ids whose name or @var{systag}
3839 matches the supplied regular expression.
3841 As well as being the complement to the @samp{thread name} command,
3842 this command also allows you to identify a thread by its target
3843 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3847 (@value{GDBN}) thread find 26688
3848 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3849 (@value{GDBN}) info thread 4
3851 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3854 @kindex set print thread-events
3855 @cindex print messages on thread start and exit
3856 @item set print thread-events
3857 @itemx set print thread-events on
3858 @itemx set print thread-events off
3859 The @code{set print thread-events} command allows you to enable or
3860 disable printing of messages when @value{GDBN} notices that new threads have
3861 started or that threads have exited. By default, these messages will
3862 be printed if detection of these events is supported by the target.
3863 Note that these messages cannot be disabled on all targets.
3865 @kindex show print thread-events
3866 @item show print thread-events
3867 Show whether messages will be printed when @value{GDBN} detects that threads
3868 have started and exited.
3871 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3872 more information about how @value{GDBN} behaves when you stop and start
3873 programs with multiple threads.
3875 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3876 watchpoints in programs with multiple threads.
3878 @anchor{set libthread-db-search-path}
3880 @kindex set libthread-db-search-path
3881 @cindex search path for @code{libthread_db}
3882 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3883 If this variable is set, @var{path} is a colon-separated list of
3884 directories @value{GDBN} will use to search for @code{libthread_db}.
3885 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3886 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3887 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3890 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3891 @code{libthread_db} library to obtain information about threads in the
3892 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3893 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3894 specific thread debugging library loading is enabled
3895 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3897 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3898 refers to the default system directories that are
3899 normally searched for loading shared libraries. The @samp{$sdir} entry
3900 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3901 (@pxref{libthread_db.so.1 file}).
3903 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3904 refers to the directory from which @code{libpthread}
3905 was loaded in the inferior process.
3907 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3908 @value{GDBN} attempts to initialize it with the current inferior process.
3909 If this initialization fails (which could happen because of a version
3910 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3911 will unload @code{libthread_db}, and continue with the next directory.
3912 If none of @code{libthread_db} libraries initialize successfully,
3913 @value{GDBN} will issue a warning and thread debugging will be disabled.
3915 Setting @code{libthread-db-search-path} is currently implemented
3916 only on some platforms.
3918 @kindex show libthread-db-search-path
3919 @item show libthread-db-search-path
3920 Display current libthread_db search path.
3922 @kindex set debug libthread-db
3923 @kindex show debug libthread-db
3924 @cindex debugging @code{libthread_db}
3925 @item set debug libthread-db
3926 @itemx show debug libthread-db
3927 Turns on or off display of @code{libthread_db}-related events.
3928 Use @code{1} to enable, @code{0} to disable.
3930 @kindex set debug threads
3931 @kindex show debug threads
3932 @cindex debugging @code{threads}
3933 @item set debug threads @r{[}on@r{|}off@r{]}
3934 @itemx show debug threads
3935 When @samp{on} @value{GDBN} will print additional messages when
3936 threads are created and deleted.
3940 @section Debugging Forks
3942 @cindex fork, debugging programs which call
3943 @cindex multiple processes
3944 @cindex processes, multiple
3945 On most systems, @value{GDBN} has no special support for debugging
3946 programs which create additional processes using the @code{fork}
3947 function. When a program forks, @value{GDBN} will continue to debug the
3948 parent process and the child process will run unimpeded. If you have
3949 set a breakpoint in any code which the child then executes, the child
3950 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3951 will cause it to terminate.
3953 However, if you want to debug the child process there is a workaround
3954 which isn't too painful. Put a call to @code{sleep} in the code which
3955 the child process executes after the fork. It may be useful to sleep
3956 only if a certain environment variable is set, or a certain file exists,
3957 so that the delay need not occur when you don't want to run @value{GDBN}
3958 on the child. While the child is sleeping, use the @code{ps} program to
3959 get its process ID. Then tell @value{GDBN} (a new invocation of
3960 @value{GDBN} if you are also debugging the parent process) to attach to
3961 the child process (@pxref{Attach}). From that point on you can debug
3962 the child process just like any other process which you attached to.
3964 On some systems, @value{GDBN} provides support for debugging programs
3965 that create additional processes using the @code{fork} or @code{vfork}
3966 functions. On @sc{gnu}/Linux platforms, this feature is supported
3967 with kernel version 2.5.46 and later.
3969 The fork debugging commands are supported in native mode and when
3970 connected to @code{gdbserver} in either @code{target remote} mode or
3971 @code{target extended-remote} mode.
3973 By default, when a program forks, @value{GDBN} will continue to debug
3974 the parent process and the child process will run unimpeded.
3976 If you want to follow the child process instead of the parent process,
3977 use the command @w{@code{set follow-fork-mode}}.
3980 @kindex set follow-fork-mode
3981 @item set follow-fork-mode @var{mode}
3982 Set the debugger response to a program call of @code{fork} or
3983 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3984 process. The @var{mode} argument can be:
3988 The original process is debugged after a fork. The child process runs
3989 unimpeded. This is the default.
3992 The new process is debugged after a fork. The parent process runs
3997 @kindex show follow-fork-mode
3998 @item show follow-fork-mode
3999 Display the current debugger response to a @code{fork} or @code{vfork} call.
4002 @cindex debugging multiple processes
4003 On Linux, if you want to debug both the parent and child processes, use the
4004 command @w{@code{set detach-on-fork}}.
4007 @kindex set detach-on-fork
4008 @item set detach-on-fork @var{mode}
4009 Tells gdb whether to detach one of the processes after a fork, or
4010 retain debugger control over them both.
4014 The child process (or parent process, depending on the value of
4015 @code{follow-fork-mode}) will be detached and allowed to run
4016 independently. This is the default.
4019 Both processes will be held under the control of @value{GDBN}.
4020 One process (child or parent, depending on the value of
4021 @code{follow-fork-mode}) is debugged as usual, while the other
4026 @kindex show detach-on-fork
4027 @item show detach-on-fork
4028 Show whether detach-on-fork mode is on/off.
4031 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4032 will retain control of all forked processes (including nested forks).
4033 You can list the forked processes under the control of @value{GDBN} by
4034 using the @w{@code{info inferiors}} command, and switch from one fork
4035 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4036 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4038 To quit debugging one of the forked processes, you can either detach
4039 from it by using the @w{@code{detach inferiors}} command (allowing it
4040 to run independently), or kill it using the @w{@code{kill inferiors}}
4041 command. @xref{Inferiors Connections and Programs, ,Debugging
4042 Multiple Inferiors Connections and Programs}.
4044 If you ask to debug a child process and a @code{vfork} is followed by an
4045 @code{exec}, @value{GDBN} executes the new target up to the first
4046 breakpoint in the new target. If you have a breakpoint set on
4047 @code{main} in your original program, the breakpoint will also be set on
4048 the child process's @code{main}.
4050 On some systems, when a child process is spawned by @code{vfork}, you
4051 cannot debug the child or parent until an @code{exec} call completes.
4053 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4054 call executes, the new target restarts. To restart the parent
4055 process, use the @code{file} command with the parent executable name
4056 as its argument. By default, after an @code{exec} call executes,
4057 @value{GDBN} discards the symbols of the previous executable image.
4058 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4062 @kindex set follow-exec-mode
4063 @item set follow-exec-mode @var{mode}
4065 Set debugger response to a program call of @code{exec}. An
4066 @code{exec} call replaces the program image of a process.
4068 @code{follow-exec-mode} can be:
4072 @value{GDBN} creates a new inferior and rebinds the process to this
4073 new inferior. The program the process was running before the
4074 @code{exec} call can be restarted afterwards by restarting the
4080 (@value{GDBP}) info inferiors
4082 Id Description Executable
4085 process 12020 is executing new program: prog2
4086 Program exited normally.
4087 (@value{GDBP}) info inferiors
4088 Id Description Executable
4094 @value{GDBN} keeps the process bound to the same inferior. The new
4095 executable image replaces the previous executable loaded in the
4096 inferior. Restarting the inferior after the @code{exec} call, with
4097 e.g., the @code{run} command, restarts the executable the process was
4098 running after the @code{exec} call. This is the default mode.
4103 (@value{GDBP}) info inferiors
4104 Id Description Executable
4107 process 12020 is executing new program: prog2
4108 Program exited normally.
4109 (@value{GDBP}) info inferiors
4110 Id Description Executable
4117 @code{follow-exec-mode} is supported in native mode and
4118 @code{target extended-remote} mode.
4120 You can use the @code{catch} command to make @value{GDBN} stop whenever
4121 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4122 Catchpoints, ,Setting Catchpoints}.
4124 @node Checkpoint/Restart
4125 @section Setting a @emph{Bookmark} to Return to Later
4130 @cindex snapshot of a process
4131 @cindex rewind program state
4133 On certain operating systems@footnote{Currently, only
4134 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4135 program's state, called a @dfn{checkpoint}, and come back to it
4138 Returning to a checkpoint effectively undoes everything that has
4139 happened in the program since the @code{checkpoint} was saved. This
4140 includes changes in memory, registers, and even (within some limits)
4141 system state. Effectively, it is like going back in time to the
4142 moment when the checkpoint was saved.
4144 Thus, if you're stepping thru a program and you think you're
4145 getting close to the point where things go wrong, you can save
4146 a checkpoint. Then, if you accidentally go too far and miss
4147 the critical statement, instead of having to restart your program
4148 from the beginning, you can just go back to the checkpoint and
4149 start again from there.
4151 This can be especially useful if it takes a lot of time or
4152 steps to reach the point where you think the bug occurs.
4154 To use the @code{checkpoint}/@code{restart} method of debugging:
4159 Save a snapshot of the debugged program's current execution state.
4160 The @code{checkpoint} command takes no arguments, but each checkpoint
4161 is assigned a small integer id, similar to a breakpoint id.
4163 @kindex info checkpoints
4164 @item info checkpoints
4165 List the checkpoints that have been saved in the current debugging
4166 session. For each checkpoint, the following information will be
4173 @item Source line, or label
4176 @kindex restart @var{checkpoint-id}
4177 @item restart @var{checkpoint-id}
4178 Restore the program state that was saved as checkpoint number
4179 @var{checkpoint-id}. All program variables, registers, stack frames
4180 etc.@: will be returned to the values that they had when the checkpoint
4181 was saved. In essence, gdb will ``wind back the clock'' to the point
4182 in time when the checkpoint was saved.
4184 Note that breakpoints, @value{GDBN} variables, command history etc.
4185 are not affected by restoring a checkpoint. In general, a checkpoint
4186 only restores things that reside in the program being debugged, not in
4189 @kindex delete checkpoint @var{checkpoint-id}
4190 @item delete checkpoint @var{checkpoint-id}
4191 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4195 Returning to a previously saved checkpoint will restore the user state
4196 of the program being debugged, plus a significant subset of the system
4197 (OS) state, including file pointers. It won't ``un-write'' data from
4198 a file, but it will rewind the file pointer to the previous location,
4199 so that the previously written data can be overwritten. For files
4200 opened in read mode, the pointer will also be restored so that the
4201 previously read data can be read again.
4203 Of course, characters that have been sent to a printer (or other
4204 external device) cannot be ``snatched back'', and characters received
4205 from eg.@: a serial device can be removed from internal program buffers,
4206 but they cannot be ``pushed back'' into the serial pipeline, ready to
4207 be received again. Similarly, the actual contents of files that have
4208 been changed cannot be restored (at this time).
4210 However, within those constraints, you actually can ``rewind'' your
4211 program to a previously saved point in time, and begin debugging it
4212 again --- and you can change the course of events so as to debug a
4213 different execution path this time.
4215 @cindex checkpoints and process id
4216 Finally, there is one bit of internal program state that will be
4217 different when you return to a checkpoint --- the program's process
4218 id. Each checkpoint will have a unique process id (or @var{pid}),
4219 and each will be different from the program's original @var{pid}.
4220 If your program has saved a local copy of its process id, this could
4221 potentially pose a problem.
4223 @subsection A Non-obvious Benefit of Using Checkpoints
4225 On some systems such as @sc{gnu}/Linux, address space randomization
4226 is performed on new processes for security reasons. This makes it
4227 difficult or impossible to set a breakpoint, or watchpoint, on an
4228 absolute address if you have to restart the program, since the
4229 absolute location of a symbol will change from one execution to the
4232 A checkpoint, however, is an @emph{identical} copy of a process.
4233 Therefore if you create a checkpoint at (eg.@:) the start of main,
4234 and simply return to that checkpoint instead of restarting the
4235 process, you can avoid the effects of address randomization and
4236 your symbols will all stay in the same place.
4239 @chapter Stopping and Continuing
4241 The principal purposes of using a debugger are so that you can stop your
4242 program before it terminates; or so that, if your program runs into
4243 trouble, you can investigate and find out why.
4245 Inside @value{GDBN}, your program may stop for any of several reasons,
4246 such as a signal, a breakpoint, or reaching a new line after a
4247 @value{GDBN} command such as @code{step}. You may then examine and
4248 change variables, set new breakpoints or remove old ones, and then
4249 continue execution. Usually, the messages shown by @value{GDBN} provide
4250 ample explanation of the status of your program---but you can also
4251 explicitly request this information at any time.
4254 @kindex info program
4256 Display information about the status of your program: whether it is
4257 running or not, what process it is, and why it stopped.
4261 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4262 * Continuing and Stepping:: Resuming execution
4263 * Skipping Over Functions and Files::
4264 Skipping over functions and files
4266 * Thread Stops:: Stopping and starting multi-thread programs
4270 @section Breakpoints, Watchpoints, and Catchpoints
4273 A @dfn{breakpoint} makes your program stop whenever a certain point in
4274 the program is reached. For each breakpoint, you can add conditions to
4275 control in finer detail whether your program stops. You can set
4276 breakpoints with the @code{break} command and its variants (@pxref{Set
4277 Breaks, ,Setting Breakpoints}), to specify the place where your program
4278 should stop by line number, function name or exact address in the
4281 On some systems, you can set breakpoints in shared libraries before
4282 the executable is run.
4285 @cindex data breakpoints
4286 @cindex memory tracing
4287 @cindex breakpoint on memory address
4288 @cindex breakpoint on variable modification
4289 A @dfn{watchpoint} is a special breakpoint that stops your program
4290 when the value of an expression changes. The expression may be a value
4291 of a variable, or it could involve values of one or more variables
4292 combined by operators, such as @samp{a + b}. This is sometimes called
4293 @dfn{data breakpoints}. You must use a different command to set
4294 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4295 from that, you can manage a watchpoint like any other breakpoint: you
4296 enable, disable, and delete both breakpoints and watchpoints using the
4299 You can arrange to have values from your program displayed automatically
4300 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4304 @cindex breakpoint on events
4305 A @dfn{catchpoint} is another special breakpoint that stops your program
4306 when a certain kind of event occurs, such as the throwing of a C@t{++}
4307 exception or the loading of a library. As with watchpoints, you use a
4308 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4309 Catchpoints}), but aside from that, you can manage a catchpoint like any
4310 other breakpoint. (To stop when your program receives a signal, use the
4311 @code{handle} command; see @ref{Signals, ,Signals}.)
4313 @cindex breakpoint numbers
4314 @cindex numbers for breakpoints
4315 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4316 catchpoint when you create it; these numbers are successive integers
4317 starting with one. In many of the commands for controlling various
4318 features of breakpoints you use the breakpoint number to say which
4319 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4320 @dfn{disabled}; if disabled, it has no effect on your program until you
4323 @cindex breakpoint ranges
4324 @cindex breakpoint lists
4325 @cindex ranges of breakpoints
4326 @cindex lists of breakpoints
4327 Some @value{GDBN} commands accept a space-separated list of breakpoints
4328 on which to operate. A list element can be either a single breakpoint number,
4329 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4330 When a breakpoint list is given to a command, all breakpoints in that list
4334 * Set Breaks:: Setting breakpoints
4335 * Set Watchpoints:: Setting watchpoints
4336 * Set Catchpoints:: Setting catchpoints
4337 * Delete Breaks:: Deleting breakpoints
4338 * Disabling:: Disabling breakpoints
4339 * Conditions:: Break conditions
4340 * Break Commands:: Breakpoint command lists
4341 * Dynamic Printf:: Dynamic printf
4342 * Save Breakpoints:: How to save breakpoints in a file
4343 * Static Probe Points:: Listing static probe points
4344 * Error in Breakpoints:: ``Cannot insert breakpoints''
4345 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4349 @subsection Setting Breakpoints
4351 @c FIXME LMB what does GDB do if no code on line of breakpt?
4352 @c consider in particular declaration with/without initialization.
4354 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4357 @kindex b @r{(@code{break})}
4358 @vindex $bpnum@r{, convenience variable}
4359 @cindex latest breakpoint
4360 Breakpoints are set with the @code{break} command (abbreviated
4361 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4362 number of the breakpoint you've set most recently; see @ref{Convenience
4363 Vars,, Convenience Variables}, for a discussion of what you can do with
4364 convenience variables.
4367 @item break @var{locspec}
4368 Set a breakpoint at all the code locations in your program that result
4369 from resolving the given @var{locspec}. @var{locspec} can specify a
4370 function name, a line number, an address of an instruction, and more.
4371 @xref{Location Specifications}, for the various forms of
4372 @var{locspec}. The breakpoint will stop your program just before it
4373 executes the instruction at the address of any of the breakpoint's
4376 When using source languages that permit overloading of symbols, such
4377 as C@t{++}, a function name may refer to more than one symbol, and
4378 thus more than one place to break. @xref{Ambiguous
4379 Expressions,,Ambiguous Expressions}, for a discussion of that
4382 It is also possible to insert a breakpoint that will stop the program
4383 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4384 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4387 When called without any arguments, @code{break} sets a breakpoint at
4388 the next instruction to be executed in the selected stack frame
4389 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4390 innermost, this makes your program stop as soon as control
4391 returns to that frame. This is similar to the effect of a
4392 @code{finish} command in the frame inside the selected frame---except
4393 that @code{finish} does not leave an active breakpoint. If you use
4394 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4395 the next time it reaches the current location; this may be useful
4398 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4399 least one instruction has been executed. If it did not do this, you
4400 would be unable to proceed past a breakpoint without first disabling the
4401 breakpoint. This rule applies whether or not the breakpoint already
4402 existed when your program stopped.
4404 @item break @dots{} if @var{cond}
4405 Set a breakpoint with condition @var{cond}; evaluate the expression
4406 @var{cond} each time the breakpoint is reached, and stop only if the
4407 value is nonzero---that is, if @var{cond} evaluates as true.
4408 @samp{@dots{}} stands for one of the possible arguments described
4409 above (or no argument) specifying where to break. @xref{Conditions,
4410 ,Break Conditions}, for more information on breakpoint conditions.
4412 The breakpoint may be mapped to multiple locations. If the breakpoint
4413 condition @var{cond} is invalid at some but not all of the locations,
4414 the locations for which the condition is invalid are disabled. For
4415 example, @value{GDBN} reports below that two of the three locations
4419 (@value{GDBP}) break func if a == 10
4420 warning: failed to validate condition at location 0x11ce, disabling:
4421 No symbol "a" in current context.
4422 warning: failed to validate condition at location 0x11b6, disabling:
4423 No symbol "a" in current context.
4424 Breakpoint 1 at 0x11b6: func. (3 locations)
4427 Locations that are disabled because of the condition are denoted by an
4428 uppercase @code{N} in the output of the @code{info breakpoints}
4432 (@value{GDBP}) info breakpoints
4433 Num Type Disp Enb Address What
4434 1 breakpoint keep y <MULTIPLE>
4435 stop only if a == 10
4436 1.1 N* 0x00000000000011b6 in ...
4437 1.2 y 0x00000000000011c2 in ...
4438 1.3 N* 0x00000000000011ce in ...
4439 (*): Breakpoint condition is invalid at this location.
4442 If the breakpoint condition @var{cond} is invalid in the context of
4443 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4444 define the breakpoint. For example, if variable @code{foo} is an
4448 (@value{GDBP}) break func if foo
4449 No symbol "foo" in current context.
4452 @item break @dots{} -force-condition if @var{cond}
4453 There may be cases where the condition @var{cond} is invalid at all
4454 the current locations, but the user knows that it will be valid at a
4455 future location; for example, because of a library load. In such
4456 cases, by using the @code{-force-condition} keyword before @samp{if},
4457 @value{GDBN} can be forced to define the breakpoint with the given
4458 condition expression instead of refusing it.
4461 (@value{GDBP}) break func -force-condition if foo
4462 warning: failed to validate condition at location 1, disabling:
4463 No symbol "foo" in current context.
4464 warning: failed to validate condition at location 2, disabling:
4465 No symbol "foo" in current context.
4466 warning: failed to validate condition at location 3, disabling:
4467 No symbol "foo" in current context.
4468 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4471 This causes all the present locations where the breakpoint would
4472 otherwise be inserted, to be disabled, as seen in the example above.
4473 However, if there exist locations at which the condition is valid, the
4474 @code{-force-condition} keyword has no effect.
4477 @item tbreak @var{args}
4478 Set a breakpoint enabled only for one stop. The @var{args} are the
4479 same as for the @code{break} command, and the breakpoint is set in the same
4480 way, but the breakpoint is automatically deleted after the first time your
4481 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4484 @cindex hardware breakpoints
4485 @item hbreak @var{args}
4486 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4487 @code{break} command and the breakpoint is set in the same way, but the
4488 breakpoint requires hardware support and some target hardware may not
4489 have this support. The main purpose of this is EPROM/ROM code
4490 debugging, so you can set a breakpoint at an instruction without
4491 changing the instruction. This can be used with the new trap-generation
4492 provided by SPARClite DSU and most x86-based targets. These targets
4493 will generate traps when a program accesses some data or instruction
4494 address that is assigned to the debug registers. However the hardware
4495 breakpoint registers can take a limited number of breakpoints. For
4496 example, on the DSU, only two data breakpoints can be set at a time, and
4497 @value{GDBN} will reject this command if more than two are used. Delete
4498 or disable unused hardware breakpoints before setting new ones
4499 (@pxref{Disabling, ,Disabling Breakpoints}).
4500 @xref{Conditions, ,Break Conditions}.
4501 For remote targets, you can restrict the number of hardware
4502 breakpoints @value{GDBN} will use, see @ref{set remote
4503 hardware-breakpoint-limit}.
4506 @item thbreak @var{args}
4507 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4508 are the same as for the @code{hbreak} command and the breakpoint is set in
4509 the same way. However, like the @code{tbreak} command,
4510 the breakpoint is automatically deleted after the
4511 first time your program stops there. Also, like the @code{hbreak}
4512 command, the breakpoint requires hardware support and some target hardware
4513 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4514 See also @ref{Conditions, ,Break Conditions}.
4517 @cindex regular expression
4518 @cindex breakpoints at functions matching a regexp
4519 @cindex set breakpoints in many functions
4520 @item rbreak @var{regex}
4521 Set breakpoints on all functions matching the regular expression
4522 @var{regex}. This command sets an unconditional breakpoint on all
4523 matches, printing a list of all breakpoints it set. Once these
4524 breakpoints are set, they are treated just like the breakpoints set with
4525 the @code{break} command. You can delete them, disable them, or make
4526 them conditional the same way as any other breakpoint.
4528 In programs using different languages, @value{GDBN} chooses the syntax
4529 to print the list of all breakpoints it sets according to the
4530 @samp{set language} value: using @samp{set language auto}
4531 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4532 language of the breakpoint's function, other values mean to use
4533 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4535 The syntax of the regular expression is the standard one used with tools
4536 like @file{grep}. Note that this is different from the syntax used by
4537 shells, so for instance @code{foo*} matches all functions that include
4538 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4539 @code{.*} leading and trailing the regular expression you supply, so to
4540 match only functions that begin with @code{foo}, use @code{^foo}.
4542 @cindex non-member C@t{++} functions, set breakpoint in
4543 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4544 breakpoints on overloaded functions that are not members of any special
4547 @cindex set breakpoints on all functions
4548 The @code{rbreak} command can be used to set breakpoints in
4549 @strong{all} the functions in a program, like this:
4552 (@value{GDBP}) rbreak .
4555 @item rbreak @var{file}:@var{regex}
4556 If @code{rbreak} is called with a filename qualification, it limits
4557 the search for functions matching the given regular expression to the
4558 specified @var{file}. This can be used, for example, to set breakpoints on
4559 every function in a given file:
4562 (@value{GDBP}) rbreak file.c:.
4565 The colon separating the filename qualifier from the regex may
4566 optionally be surrounded by spaces.
4568 @kindex info breakpoints
4569 @cindex @code{$_} and @code{info breakpoints}
4570 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4571 @itemx info break @r{[}@var{list}@dots{}@r{]}
4572 Print a table of all breakpoints, watchpoints, and catchpoints set and
4573 not deleted. Optional argument @var{n} means print information only
4574 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4575 For each breakpoint, following columns are printed:
4578 @item Breakpoint Numbers
4580 Breakpoint, watchpoint, or catchpoint.
4582 Whether the breakpoint is marked to be disabled or deleted when hit.
4583 @item Enabled or Disabled
4584 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4585 that are not enabled.
4587 Where the breakpoint is in your program, as a memory address. For a
4588 pending breakpoint whose address is not yet known, this field will
4589 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4590 library that has the symbol or line referred by breakpoint is loaded.
4591 See below for details. A breakpoint with several locations will
4592 have @samp{<MULTIPLE>} in this field---see below for details.
4594 Where the breakpoint is in the source for your program, as a file and
4595 line number. For a pending breakpoint, the original string passed to
4596 the breakpoint command will be listed as it cannot be resolved until
4597 the appropriate shared library is loaded in the future.
4601 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4602 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4603 @value{GDBN} on the host's side. If it is ``target'', then the condition
4604 is evaluated by the target. The @code{info break} command shows
4605 the condition on the line following the affected breakpoint, together with
4606 its condition evaluation mode in between parentheses.
4608 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4609 allowed to have a condition specified for it. The condition is not parsed for
4610 validity until a shared library is loaded that allows the pending
4611 breakpoint to resolve to a valid location.
4614 @code{info break} with a breakpoint
4615 number @var{n} as argument lists only that breakpoint. The
4616 convenience variable @code{$_} and the default examining-address for
4617 the @code{x} command are set to the address of the last breakpoint
4618 listed (@pxref{Memory, ,Examining Memory}).
4621 @code{info break} displays a count of the number of times the breakpoint
4622 has been hit. This is especially useful in conjunction with the
4623 @code{ignore} command. You can ignore a large number of breakpoint
4624 hits, look at the breakpoint info to see how many times the breakpoint
4625 was hit, and then run again, ignoring one less than that number. This
4626 will get you quickly to the last hit of that breakpoint.
4629 For a breakpoints with an enable count (xref) greater than 1,
4630 @code{info break} also displays that count.
4634 @value{GDBN} allows you to set any number of breakpoints at the same place in
4635 your program. There is nothing silly or meaningless about this. When
4636 the breakpoints are conditional, this is even useful
4637 (@pxref{Conditions, ,Break Conditions}).
4639 @cindex multiple locations, breakpoints
4640 @cindex breakpoints, multiple locations
4641 It is possible that a single logical breakpoint is set at several code
4642 locations in your program. @xref{Location Specifications}, for
4645 A breakpoint with multiple code locations is displayed in the
4646 breakpoint table using several rows---one header row, followed by one
4647 row for each code location. The header row has @samp{<MULTIPLE>} in
4648 the address column. Each code location row contains the actual
4649 address, source file, source line and function of its code location.
4650 The number column for a code location is of the form
4651 @var{breakpoint-number}.@var{location-number}.
4656 Num Type Disp Enb Address What
4657 1 breakpoint keep y <MULTIPLE>
4659 breakpoint already hit 1 time
4660 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4661 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4664 You cannot delete the individual locations from a breakpoint. However,
4665 each location can be individually enabled or disabled by passing
4666 @var{breakpoint-number}.@var{location-number} as argument to the
4667 @code{enable} and @code{disable} commands. It's also possible to
4668 @code{enable} and @code{disable} a range of @var{location-number}
4669 locations using a @var{breakpoint-number} and two @var{location-number}s,
4670 in increasing order, separated by a hyphen, like
4671 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4672 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4673 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4674 all of the locations that belong to that breakpoint.
4676 Locations that are enabled while their parent breakpoint is disabled
4677 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4678 column. For example:
4681 (@value{GDBP}) info breakpoints
4682 Num Type Disp Enb Address What
4683 1 breakpoint keep n <MULTIPLE>
4684 1.1 y- 0x00000000000011b6 in ...
4685 1.2 y- 0x00000000000011c2 in ...
4686 1.3 n 0x00000000000011ce in ...
4689 @cindex pending breakpoints
4690 It's quite common to have a breakpoint inside a shared library.
4691 Shared libraries can be loaded and unloaded explicitly,
4692 and possibly repeatedly, as the program is executed. To support
4693 this use case, @value{GDBN} updates breakpoint locations whenever
4694 any shared library is loaded or unloaded. Typically, you would
4695 set a breakpoint in a shared library at the beginning of your
4696 debugging session, when the library is not loaded, and when the
4697 symbols from the library are not available. When you try to set
4698 breakpoint, @value{GDBN} will ask you if you want to set
4699 a so called @dfn{pending breakpoint}---breakpoint whose address
4700 is not yet resolved.
4702 After the program is run, whenever a new shared library is loaded,
4703 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4704 shared library contains the symbol or line referred to by some
4705 pending breakpoint, that breakpoint is resolved and becomes an
4706 ordinary breakpoint. When a library is unloaded, all breakpoints
4707 that refer to its symbols or source lines become pending again.
4709 This logic works for breakpoints with multiple locations, too. For
4710 example, if you have a breakpoint in a C@t{++} template function, and
4711 a newly loaded shared library has an instantiation of that template,
4712 a new location is added to the list of locations for the breakpoint.
4714 Except for having unresolved address, pending breakpoints do not
4715 differ from regular breakpoints. You can set conditions or commands,
4716 enable and disable them and perform other breakpoint operations.
4718 @value{GDBN} provides some additional commands for controlling what
4719 happens when the @samp{break} command cannot resolve the location spec
4720 to any code location in your program (@pxref{Location
4723 @kindex set breakpoint pending
4724 @kindex show breakpoint pending
4726 @item set breakpoint pending auto
4727 This is the default behavior. When @value{GDBN} cannot resolve the
4728 location spec, it queries you whether a pending breakpoint should be
4731 @item set breakpoint pending on
4732 This indicates that when @value{GDBN} cannot resolve the location
4733 spec, it should create a pending breakpoint without confirmation.
4735 @item set breakpoint pending off
4736 This indicates that pending breakpoints are not to be created. If
4737 @value{GDBN} cannot resolve the location spec, it aborts the
4738 breakpoint creation with an error. This setting does not affect any
4739 pending breakpoints previously created.
4741 @item show breakpoint pending
4742 Show the current behavior setting for creating pending breakpoints.
4745 The settings above only affect the @code{break} command and its
4746 variants. Once a breakpoint is set, it will be automatically updated
4747 as shared libraries are loaded and unloaded.
4749 @cindex automatic hardware breakpoints
4750 For some targets, @value{GDBN} can automatically decide if hardware or
4751 software breakpoints should be used, depending on whether the
4752 breakpoint address is read-only or read-write. This applies to
4753 breakpoints set with the @code{break} command as well as to internal
4754 breakpoints set by commands like @code{next} and @code{finish}. For
4755 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4758 You can control this automatic behaviour with the following commands:
4760 @kindex set breakpoint auto-hw
4761 @kindex show breakpoint auto-hw
4763 @item set breakpoint auto-hw on
4764 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4765 will try to use the target memory map to decide if software or hardware
4766 breakpoint must be used.
4768 @item set breakpoint auto-hw off
4769 This indicates @value{GDBN} should not automatically select breakpoint
4770 type. If the target provides a memory map, @value{GDBN} will warn when
4771 trying to set software breakpoint at a read-only address.
4774 @value{GDBN} normally implements breakpoints by replacing the program code
4775 at the breakpoint address with a special instruction, which, when
4776 executed, given control to the debugger. By default, the program
4777 code is so modified only when the program is resumed. As soon as
4778 the program stops, @value{GDBN} restores the original instructions. This
4779 behaviour guards against leaving breakpoints inserted in the
4780 target should gdb abrubptly disconnect. However, with slow remote
4781 targets, inserting and removing breakpoint can reduce the performance.
4782 This behavior can be controlled with the following commands::
4784 @kindex set breakpoint always-inserted
4785 @kindex show breakpoint always-inserted
4787 @item set breakpoint always-inserted off
4788 All breakpoints, including newly added by the user, are inserted in
4789 the target only when the target is resumed. All breakpoints are
4790 removed from the target when it stops. This is the default mode.
4792 @item set breakpoint always-inserted on
4793 Causes all breakpoints to be inserted in the target at all times. If
4794 the user adds a new breakpoint, or changes an existing breakpoint, the
4795 breakpoints in the target are updated immediately. A breakpoint is
4796 removed from the target only when breakpoint itself is deleted.
4799 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4800 when a breakpoint breaks. If the condition is true, then the process being
4801 debugged stops, otherwise the process is resumed.
4803 If the target supports evaluating conditions on its end, @value{GDBN} may
4804 download the breakpoint, together with its conditions, to it.
4806 This feature can be controlled via the following commands:
4808 @kindex set breakpoint condition-evaluation
4809 @kindex show breakpoint condition-evaluation
4811 @item set breakpoint condition-evaluation host
4812 This option commands @value{GDBN} to evaluate the breakpoint
4813 conditions on the host's side. Unconditional breakpoints are sent to
4814 the target which in turn receives the triggers and reports them back to GDB
4815 for condition evaluation. This is the standard evaluation mode.
4817 @item set breakpoint condition-evaluation target
4818 This option commands @value{GDBN} to download breakpoint conditions
4819 to the target at the moment of their insertion. The target
4820 is responsible for evaluating the conditional expression and reporting
4821 breakpoint stop events back to @value{GDBN} whenever the condition
4822 is true. Due to limitations of target-side evaluation, some conditions
4823 cannot be evaluated there, e.g., conditions that depend on local data
4824 that is only known to the host. Examples include
4825 conditional expressions involving convenience variables, complex types
4826 that cannot be handled by the agent expression parser and expressions
4827 that are too long to be sent over to the target, specially when the
4828 target is a remote system. In these cases, the conditions will be
4829 evaluated by @value{GDBN}.
4831 @item set breakpoint condition-evaluation auto
4832 This is the default mode. If the target supports evaluating breakpoint
4833 conditions on its end, @value{GDBN} will download breakpoint conditions to
4834 the target (limitations mentioned previously apply). If the target does
4835 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4836 to evaluating all these conditions on the host's side.
4840 @cindex negative breakpoint numbers
4841 @cindex internal @value{GDBN} breakpoints
4842 @value{GDBN} itself sometimes sets breakpoints in your program for
4843 special purposes, such as proper handling of @code{longjmp} (in C
4844 programs). These internal breakpoints are assigned negative numbers,
4845 starting with @code{-1}; @samp{info breakpoints} does not display them.
4846 You can see these breakpoints with the @value{GDBN} maintenance command
4847 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4850 @node Set Watchpoints
4851 @subsection Setting Watchpoints
4853 @cindex setting watchpoints
4854 You can use a watchpoint to stop execution whenever the value of an
4855 expression changes, without having to predict a particular place where
4856 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4857 The expression may be as simple as the value of a single variable, or
4858 as complex as many variables combined by operators. Examples include:
4862 A reference to the value of a single variable.
4865 An address cast to an appropriate data type. For example,
4866 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4867 address (assuming an @code{int} occupies 4 bytes).
4870 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4871 expression can use any operators valid in the program's native
4872 language (@pxref{Languages}).
4875 You can set a watchpoint on an expression even if the expression can
4876 not be evaluated yet. For instance, you can set a watchpoint on
4877 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4878 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4879 the expression produces a valid value. If the expression becomes
4880 valid in some other way than changing a variable (e.g.@: if the memory
4881 pointed to by @samp{*global_ptr} becomes readable as the result of a
4882 @code{malloc} call), @value{GDBN} may not stop until the next time
4883 the expression changes.
4885 @cindex software watchpoints
4886 @cindex hardware watchpoints
4887 Depending on your system, watchpoints may be implemented in software or
4888 hardware. @value{GDBN} does software watchpointing by single-stepping your
4889 program and testing the variable's value each time, which is hundreds of
4890 times slower than normal execution. (But this may still be worth it, to
4891 catch errors where you have no clue what part of your program is the
4894 On some systems, such as most PowerPC or x86-based targets,
4895 @value{GDBN} includes support for hardware watchpoints, which do not
4896 slow down the running of your program.
4900 @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{]}
4901 Set a watchpoint for an expression. @value{GDBN} will break when the
4902 expression @var{expr} is written into by the program and its value
4903 changes. The simplest (and the most popular) use of this command is
4904 to watch the value of a single variable:
4907 (@value{GDBP}) watch foo
4910 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4911 argument, @value{GDBN} breaks only when the thread identified by
4912 @var{thread-id} changes the value of @var{expr}. If any other threads
4913 change the value of @var{expr}, @value{GDBN} will not break. Note
4914 that watchpoints restricted to a single thread in this way only work
4915 with Hardware Watchpoints.
4917 Similarly, if the @code{task} argument is given, then the watchpoint
4918 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4920 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4921 (see below). The @code{-location} argument tells @value{GDBN} to
4922 instead watch the memory referred to by @var{expr}. In this case,
4923 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4924 and watch the memory at that address. The type of the result is used
4925 to determine the size of the watched memory. If the expression's
4926 result does not have an address, then @value{GDBN} will print an
4929 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4930 of masked watchpoints, if the current architecture supports this
4931 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4932 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4933 to an address to watch. The mask specifies that some bits of an address
4934 (the bits which are reset in the mask) should be ignored when matching
4935 the address accessed by the inferior against the watchpoint address.
4936 Thus, a masked watchpoint watches many addresses simultaneously---those
4937 addresses whose unmasked bits are identical to the unmasked bits in the
4938 watchpoint address. The @code{mask} argument implies @code{-location}.
4942 (@value{GDBP}) watch foo mask 0xffff00ff
4943 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4947 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4948 Set a watchpoint that will break when the value of @var{expr} is read
4952 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4953 Set a watchpoint that will break when @var{expr} is either read from
4954 or written into by the program.
4956 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4957 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4958 This command prints a list of watchpoints, using the same format as
4959 @code{info break} (@pxref{Set Breaks}).
4962 If you watch for a change in a numerically entered address you need to
4963 dereference it, as the address itself is just a constant number which will
4964 never change. @value{GDBN} refuses to create a watchpoint that watches
4965 a never-changing value:
4968 (@value{GDBP}) watch 0x600850
4969 Cannot watch constant value 0x600850.
4970 (@value{GDBP}) watch *(int *) 0x600850
4971 Watchpoint 1: *(int *) 6293584
4974 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4975 watchpoints execute very quickly, and the debugger reports a change in
4976 value at the exact instruction where the change occurs. If @value{GDBN}
4977 cannot set a hardware watchpoint, it sets a software watchpoint, which
4978 executes more slowly and reports the change in value at the next
4979 @emph{statement}, not the instruction, after the change occurs.
4981 @cindex use only software watchpoints
4982 You can force @value{GDBN} to use only software watchpoints with the
4983 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4984 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4985 the underlying system supports them. (Note that hardware-assisted
4986 watchpoints that were set @emph{before} setting
4987 @code{can-use-hw-watchpoints} to zero will still use the hardware
4988 mechanism of watching expression values.)
4991 @item set can-use-hw-watchpoints
4992 @kindex set can-use-hw-watchpoints
4993 Set whether or not to use hardware watchpoints.
4995 @item show can-use-hw-watchpoints
4996 @kindex show can-use-hw-watchpoints
4997 Show the current mode of using hardware watchpoints.
5000 For remote targets, you can restrict the number of hardware
5001 watchpoints @value{GDBN} will use, see @ref{set remote
5002 hardware-breakpoint-limit}.
5004 When you issue the @code{watch} command, @value{GDBN} reports
5007 Hardware watchpoint @var{num}: @var{expr}
5011 if it was able to set a hardware watchpoint.
5013 Currently, the @code{awatch} and @code{rwatch} commands can only set
5014 hardware watchpoints, because accesses to data that don't change the
5015 value of the watched expression cannot be detected without examining
5016 every instruction as it is being executed, and @value{GDBN} does not do
5017 that currently. If @value{GDBN} finds that it is unable to set a
5018 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5019 will print a message like this:
5022 Expression cannot be implemented with read/access watchpoint.
5025 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5026 data type of the watched expression is wider than what a hardware
5027 watchpoint on the target machine can handle. For example, some systems
5028 can only watch regions that are up to 4 bytes wide; on such systems you
5029 cannot set hardware watchpoints for an expression that yields a
5030 double-precision floating-point number (which is typically 8 bytes
5031 wide). As a work-around, it might be possible to break the large region
5032 into a series of smaller ones and watch them with separate watchpoints.
5034 If you set too many hardware watchpoints, @value{GDBN} might be unable
5035 to insert all of them when you resume the execution of your program.
5036 Since the precise number of active watchpoints is unknown until such
5037 time as the program is about to be resumed, @value{GDBN} might not be
5038 able to warn you about this when you set the watchpoints, and the
5039 warning will be printed only when the program is resumed:
5042 Hardware watchpoint @var{num}: Could not insert watchpoint
5046 If this happens, delete or disable some of the watchpoints.
5048 Watching complex expressions that reference many variables can also
5049 exhaust the resources available for hardware-assisted watchpoints.
5050 That's because @value{GDBN} needs to watch every variable in the
5051 expression with separately allocated resources.
5053 If you call a function interactively using @code{print} or @code{call},
5054 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5055 kind of breakpoint or the call completes.
5057 @value{GDBN} automatically deletes watchpoints that watch local
5058 (automatic) variables, or expressions that involve such variables, when
5059 they go out of scope, that is, when the execution leaves the block in
5060 which these variables were defined. In particular, when the program
5061 being debugged terminates, @emph{all} local variables go out of scope,
5062 and so only watchpoints that watch global variables remain set. If you
5063 rerun the program, you will need to set all such watchpoints again. One
5064 way of doing that would be to set a code breakpoint at the entry to the
5065 @code{main} function and when it breaks, set all the watchpoints.
5067 @cindex watchpoints and threads
5068 @cindex threads and watchpoints
5069 In multi-threaded programs, watchpoints will detect changes to the
5070 watched expression from every thread.
5073 @emph{Warning:} In multi-threaded programs, software watchpoints
5074 have only limited usefulness. If @value{GDBN} creates a software
5075 watchpoint, it can only watch the value of an expression @emph{in a
5076 single thread}. If you are confident that the expression can only
5077 change due to the current thread's activity (and if you are also
5078 confident that no other thread can become current), then you can use
5079 software watchpoints as usual. However, @value{GDBN} may not notice
5080 when a non-current thread's activity changes the expression. (Hardware
5081 watchpoints, in contrast, watch an expression in all threads.)
5084 @xref{set remote hardware-watchpoint-limit}.
5086 @node Set Catchpoints
5087 @subsection Setting Catchpoints
5088 @cindex catchpoints, setting
5089 @cindex exception handlers
5090 @cindex event handling
5092 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5093 kinds of program events, such as C@t{++} exceptions or the loading of a
5094 shared library. Use the @code{catch} command to set a catchpoint.
5098 @item catch @var{event}
5099 Stop when @var{event} occurs. The @var{event} can be any of the following:
5102 @item throw @r{[}@var{regexp}@r{]}
5103 @itemx rethrow @r{[}@var{regexp}@r{]}
5104 @itemx catch @r{[}@var{regexp}@r{]}
5106 @kindex catch rethrow
5108 @cindex stop on C@t{++} exceptions
5109 The throwing, re-throwing, or catching of a C@t{++} exception.
5111 If @var{regexp} is given, then only exceptions whose type matches the
5112 regular expression will be caught.
5114 @vindex $_exception@r{, convenience variable}
5115 The convenience variable @code{$_exception} is available at an
5116 exception-related catchpoint, on some systems. This holds the
5117 exception being thrown.
5119 There are currently some limitations to C@t{++} exception handling in
5124 The support for these commands is system-dependent. Currently, only
5125 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5129 The regular expression feature and the @code{$_exception} convenience
5130 variable rely on the presence of some SDT probes in @code{libstdc++}.
5131 If these probes are not present, then these features cannot be used.
5132 These probes were first available in the GCC 4.8 release, but whether
5133 or not they are available in your GCC also depends on how it was
5137 The @code{$_exception} convenience variable is only valid at the
5138 instruction at which an exception-related catchpoint is set.
5141 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5142 location in the system library which implements runtime exception
5143 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5144 (@pxref{Selection}) to get to your code.
5147 If you call a function interactively, @value{GDBN} normally returns
5148 control to you when the function has finished executing. If the call
5149 raises an exception, however, the call may bypass the mechanism that
5150 returns control to you and cause your program either to abort or to
5151 simply continue running until it hits a breakpoint, catches a signal
5152 that @value{GDBN} is listening for, or exits. This is the case even if
5153 you set a catchpoint for the exception; catchpoints on exceptions are
5154 disabled within interactive calls. @xref{Calling}, for information on
5155 controlling this with @code{set unwind-on-terminating-exception}.
5158 You cannot raise an exception interactively.
5161 You cannot install an exception handler interactively.
5164 @item exception @r{[}@var{name}@r{]}
5165 @kindex catch exception
5166 @cindex Ada exception catching
5167 @cindex catch Ada exceptions
5168 An Ada exception being raised. If an exception name is specified
5169 at the end of the command (eg @code{catch exception Program_Error}),
5170 the debugger will stop only when this specific exception is raised.
5171 Otherwise, the debugger stops execution when any Ada exception is raised.
5173 When inserting an exception catchpoint on a user-defined exception whose
5174 name is identical to one of the exceptions defined by the language, the
5175 fully qualified name must be used as the exception name. Otherwise,
5176 @value{GDBN} will assume that it should stop on the pre-defined exception
5177 rather than the user-defined one. For instance, assuming an exception
5178 called @code{Constraint_Error} is defined in package @code{Pck}, then
5179 the command to use to catch such exceptions is @kbd{catch exception
5180 Pck.Constraint_Error}.
5182 @vindex $_ada_exception@r{, convenience variable}
5183 The convenience variable @code{$_ada_exception} holds the address of
5184 the exception being thrown. This can be useful when setting a
5185 condition for such a catchpoint.
5187 @item exception unhandled
5188 @kindex catch exception unhandled
5189 An exception that was raised but is not handled by the program. The
5190 convenience variable @code{$_ada_exception} is set as for @code{catch
5193 @item handlers @r{[}@var{name}@r{]}
5194 @kindex catch handlers
5195 @cindex Ada exception handlers catching
5196 @cindex catch Ada exceptions when handled
5197 An Ada exception being handled. If an exception name is
5198 specified at the end of the command
5199 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5200 only when this specific exception is handled.
5201 Otherwise, the debugger stops execution when any Ada exception is handled.
5203 When inserting a handlers catchpoint on a user-defined
5204 exception whose name is identical to one of the exceptions
5205 defined by the language, the fully qualified name must be used
5206 as the exception name. Otherwise, @value{GDBN} will assume that it
5207 should stop on the pre-defined exception rather than the
5208 user-defined one. For instance, assuming an exception called
5209 @code{Constraint_Error} is defined in package @code{Pck}, then the
5210 command to use to catch such exceptions handling is
5211 @kbd{catch handlers Pck.Constraint_Error}.
5213 The convenience variable @code{$_ada_exception} is set as for
5214 @code{catch exception}.
5217 @kindex catch assert
5218 A failed Ada assertion. Note that the convenience variable
5219 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5223 @cindex break on fork/exec
5224 A call to @code{exec}.
5226 @anchor{catch syscall}
5228 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5229 @kindex catch syscall
5230 @cindex break on a system call.
5231 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5232 syscall is a mechanism for application programs to request a service
5233 from the operating system (OS) or one of the OS system services.
5234 @value{GDBN} can catch some or all of the syscalls issued by the
5235 debuggee, and show the related information for each syscall. If no
5236 argument is specified, calls to and returns from all system calls
5239 @var{name} can be any system call name that is valid for the
5240 underlying OS. Just what syscalls are valid depends on the OS. On
5241 GNU and Unix systems, you can find the full list of valid syscall
5242 names on @file{/usr/include/asm/unistd.h}.
5244 @c For MS-Windows, the syscall names and the corresponding numbers
5245 @c can be found, e.g., on this URL:
5246 @c http://www.metasploit.com/users/opcode/syscalls.html
5247 @c but we don't support Windows syscalls yet.
5249 Normally, @value{GDBN} knows in advance which syscalls are valid for
5250 each OS, so you can use the @value{GDBN} command-line completion
5251 facilities (@pxref{Completion,, command completion}) to list the
5254 You may also specify the system call numerically. A syscall's
5255 number is the value passed to the OS's syscall dispatcher to
5256 identify the requested service. When you specify the syscall by its
5257 name, @value{GDBN} uses its database of syscalls to convert the name
5258 into the corresponding numeric code, but using the number directly
5259 may be useful if @value{GDBN}'s database does not have the complete
5260 list of syscalls on your system (e.g., because @value{GDBN} lags
5261 behind the OS upgrades).
5263 You may specify a group of related syscalls to be caught at once using
5264 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5265 instance, on some platforms @value{GDBN} allows you to catch all
5266 network related syscalls, by passing the argument @code{group:network}
5267 to @code{catch syscall}. Note that not all syscall groups are
5268 available in every system. You can use the command completion
5269 facilities (@pxref{Completion,, command completion}) to list the
5270 syscall groups available on your environment.
5272 The example below illustrates how this command works if you don't provide
5276 (@value{GDBP}) catch syscall
5277 Catchpoint 1 (syscall)
5279 Starting program: /tmp/catch-syscall
5281 Catchpoint 1 (call to syscall 'close'), \
5282 0xffffe424 in __kernel_vsyscall ()
5286 Catchpoint 1 (returned from syscall 'close'), \
5287 0xffffe424 in __kernel_vsyscall ()
5291 Here is an example of catching a system call by name:
5294 (@value{GDBP}) catch syscall chroot
5295 Catchpoint 1 (syscall 'chroot' [61])
5297 Starting program: /tmp/catch-syscall
5299 Catchpoint 1 (call to syscall 'chroot'), \
5300 0xffffe424 in __kernel_vsyscall ()
5304 Catchpoint 1 (returned from syscall 'chroot'), \
5305 0xffffe424 in __kernel_vsyscall ()
5309 An example of specifying a system call numerically. In the case
5310 below, the syscall number has a corresponding entry in the XML
5311 file, so @value{GDBN} finds its name and prints it:
5314 (@value{GDBP}) catch syscall 252
5315 Catchpoint 1 (syscall(s) 'exit_group')
5317 Starting program: /tmp/catch-syscall
5319 Catchpoint 1 (call to syscall 'exit_group'), \
5320 0xffffe424 in __kernel_vsyscall ()
5324 Program exited normally.
5328 Here is an example of catching a syscall group:
5331 (@value{GDBP}) catch syscall group:process
5332 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5333 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5334 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5336 Starting program: /tmp/catch-syscall
5338 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5339 from /lib64/ld-linux-x86-64.so.2
5345 However, there can be situations when there is no corresponding name
5346 in XML file for that syscall number. In this case, @value{GDBN} prints
5347 a warning message saying that it was not able to find the syscall name,
5348 but the catchpoint will be set anyway. See the example below:
5351 (@value{GDBP}) catch syscall 764
5352 warning: The number '764' does not represent a known syscall.
5353 Catchpoint 2 (syscall 764)
5357 If you configure @value{GDBN} using the @samp{--without-expat} option,
5358 it will not be able to display syscall names. Also, if your
5359 architecture does not have an XML file describing its system calls,
5360 you will not be able to see the syscall names. It is important to
5361 notice that these two features are used for accessing the syscall
5362 name database. In either case, you will see a warning like this:
5365 (@value{GDBP}) catch syscall
5366 warning: Could not open "syscalls/i386-linux.xml"
5367 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5368 GDB will not be able to display syscall names.
5369 Catchpoint 1 (syscall)
5373 Of course, the file name will change depending on your architecture and system.
5375 Still using the example above, you can also try to catch a syscall by its
5376 number. In this case, you would see something like:
5379 (@value{GDBP}) catch syscall 252
5380 Catchpoint 1 (syscall(s) 252)
5383 Again, in this case @value{GDBN} would not be able to display syscall's names.
5387 A call to @code{fork}.
5391 A call to @code{vfork}.
5393 @item load @r{[}@var{regexp}@r{]}
5394 @itemx unload @r{[}@var{regexp}@r{]}
5396 @kindex catch unload
5397 The loading or unloading of a shared library. If @var{regexp} is
5398 given, then the catchpoint will stop only if the regular expression
5399 matches one of the affected libraries.
5401 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5402 @kindex catch signal
5403 The delivery of a signal.
5405 With no arguments, this catchpoint will catch any signal that is not
5406 used internally by @value{GDBN}, specifically, all signals except
5407 @samp{SIGTRAP} and @samp{SIGINT}.
5409 With the argument @samp{all}, all signals, including those used by
5410 @value{GDBN}, will be caught. This argument cannot be used with other
5413 Otherwise, the arguments are a list of signal names as given to
5414 @code{handle} (@pxref{Signals}). Only signals specified in this list
5417 One reason that @code{catch signal} can be more useful than
5418 @code{handle} is that you can attach commands and conditions to the
5421 When a signal is caught by a catchpoint, the signal's @code{stop} and
5422 @code{print} settings, as specified by @code{handle}, are ignored.
5423 However, whether the signal is still delivered to the inferior depends
5424 on the @code{pass} setting; this can be changed in the catchpoint's
5429 @item tcatch @var{event}
5431 Set a catchpoint that is enabled only for one stop. The catchpoint is
5432 automatically deleted after the first time the event is caught.
5436 Use the @code{info break} command to list the current catchpoints.
5440 @subsection Deleting Breakpoints
5442 @cindex clearing breakpoints, watchpoints, catchpoints
5443 @cindex deleting breakpoints, watchpoints, catchpoints
5444 It is often necessary to eliminate a breakpoint, watchpoint, or
5445 catchpoint once it has done its job and you no longer want your program
5446 to stop there. This is called @dfn{deleting} the breakpoint. A
5447 breakpoint that has been deleted no longer exists; it is forgotten.
5449 With the @code{clear} command you can delete breakpoints according to
5450 where they are in your program. With the @code{delete} command you can
5451 delete individual breakpoints, watchpoints, or catchpoints by specifying
5452 their breakpoint numbers.
5454 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5455 automatically ignores breakpoints on the first instruction to be executed
5456 when you continue execution without changing the execution address.
5461 Delete any breakpoints at the next instruction to be executed in the
5462 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5463 the innermost frame is selected, this is a good way to delete a
5464 breakpoint where your program just stopped.
5466 @item clear @var{locspec}
5467 Delete any breakpoint with a code location that corresponds to
5468 @var{locspec}. @xref{Location Specifications}, for the various forms
5469 of @var{locspec}. Which code locations correspond to @var{locspec}
5470 depends on the form used in the location specification @var{locspec}:
5474 @itemx @var{filename}:@var{linenum}
5475 @itemx -line @var{linenum}
5476 @itemx -source @var{filename} -line @var{linenum}
5477 If @var{locspec} specifies a line number, with or without a file name,
5478 the command deletes any breakpoint with a code location that is at or
5479 within the specified line @var{linenum} in files that match the
5480 specified @var{filename}. If @var{filename} is omitted, it defaults
5481 to the current source file.
5483 @item *@var{address}
5484 If @var{locspec} specifies an address, the command deletes any
5485 breakpoint with a code location that is at the given @var{address}.
5487 @item @var{function}
5488 @itemx -function @var{function}
5489 If @var{locspec} specifies a function, the command deletes any
5490 breakpoint with a code location that is at the entry to any function
5491 whose name matches @var{function}.
5494 Ambiguity in names of files and functions can be resolved as described
5495 in @ref{Location Specifications}.
5497 @cindex delete breakpoints
5499 @kindex d @r{(@code{delete})}
5500 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5501 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5502 list specified as argument. If no argument is specified, delete all
5503 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5504 confirm off}). You can abbreviate this command as @code{d}.
5508 @subsection Disabling Breakpoints
5510 @cindex enable/disable a breakpoint
5511 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5512 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5513 it had been deleted, but remembers the information on the breakpoint so
5514 that you can @dfn{enable} it again later.
5516 You disable and enable breakpoints, watchpoints, and catchpoints with
5517 the @code{enable} and @code{disable} commands, optionally specifying
5518 one or more breakpoint numbers as arguments. Use @code{info break} to
5519 print a list of all breakpoints, watchpoints, and catchpoints if you
5520 do not know which numbers to use.
5522 Disabling and enabling a breakpoint that has multiple locations
5523 affects all of its locations.
5525 A breakpoint, watchpoint, or catchpoint can have any of several
5526 different states of enablement:
5530 Enabled. The breakpoint stops your program. A breakpoint set
5531 with the @code{break} command starts out in this state.
5533 Disabled. The breakpoint has no effect on your program.
5535 Enabled once. The breakpoint stops your program, but then becomes
5538 Enabled for a count. The breakpoint stops your program for the next
5539 N times, then becomes disabled.
5541 Enabled for deletion. The breakpoint stops your program, but
5542 immediately after it does so it is deleted permanently. A breakpoint
5543 set with the @code{tbreak} command starts out in this state.
5546 You can use the following commands to enable or disable breakpoints,
5547 watchpoints, and catchpoints:
5551 @kindex dis @r{(@code{disable})}
5552 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5553 Disable the specified breakpoints---or all breakpoints, if none are
5554 listed. A disabled breakpoint has no effect but is not forgotten. All
5555 options such as ignore-counts, conditions and commands are remembered in
5556 case the breakpoint is enabled again later. You may abbreviate
5557 @code{disable} as @code{dis}.
5560 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5561 Enable the specified breakpoints (or all defined breakpoints). They
5562 become effective once again in stopping your program.
5564 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5565 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5566 of these breakpoints immediately after stopping your program.
5568 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5569 Enable the specified breakpoints temporarily. @value{GDBN} records
5570 @var{count} with each of the specified breakpoints, and decrements a
5571 breakpoint's count when it is hit. When any count reaches 0,
5572 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5573 count (@pxref{Conditions, ,Break Conditions}), that will be
5574 decremented to 0 before @var{count} is affected.
5576 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5577 Enable the specified breakpoints to work once, then die. @value{GDBN}
5578 deletes any of these breakpoints as soon as your program stops there.
5579 Breakpoints set by the @code{tbreak} command start out in this state.
5582 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5583 @c confusing: tbreak is also initially enabled.
5584 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5585 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5586 subsequently, they become disabled or enabled only when you use one of
5587 the commands above. (The command @code{until} can set and delete a
5588 breakpoint of its own, but it does not change the state of your other
5589 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5593 @subsection Break Conditions
5594 @cindex conditional breakpoints
5595 @cindex breakpoint conditions
5597 @c FIXME what is scope of break condition expr? Context where wanted?
5598 @c in particular for a watchpoint?
5599 The simplest sort of breakpoint breaks every time your program reaches a
5600 specified place. You can also specify a @dfn{condition} for a
5601 breakpoint. A condition is just a Boolean expression in your
5602 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5603 a condition evaluates the expression each time your program reaches it,
5604 and your program stops only if the condition is @emph{true}.
5606 This is the converse of using assertions for program validation; in that
5607 situation, you want to stop when the assertion is violated---that is,
5608 when the condition is false. In C, if you want to test an assertion expressed
5609 by the condition @var{assert}, you should set the condition
5610 @samp{! @var{assert}} on the appropriate breakpoint.
5612 Conditions are also accepted for watchpoints; you may not need them,
5613 since a watchpoint is inspecting the value of an expression anyhow---but
5614 it might be simpler, say, to just set a watchpoint on a variable name,
5615 and specify a condition that tests whether the new value is an interesting
5618 Break conditions can have side effects, and may even call functions in
5619 your program. This can be useful, for example, to activate functions
5620 that log program progress, or to use your own print functions to
5621 format special data structures. The effects are completely predictable
5622 unless there is another enabled breakpoint at the same address. (In
5623 that case, @value{GDBN} might see the other breakpoint first and stop your
5624 program without checking the condition of this one.) Note that
5625 breakpoint commands are usually more convenient and flexible than break
5627 purpose of performing side effects when a breakpoint is reached
5628 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5630 Breakpoint conditions can also be evaluated on the target's side if
5631 the target supports it. Instead of evaluating the conditions locally,
5632 @value{GDBN} encodes the expression into an agent expression
5633 (@pxref{Agent Expressions}) suitable for execution on the target,
5634 independently of @value{GDBN}. Global variables become raw memory
5635 locations, locals become stack accesses, and so forth.
5637 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5638 when its condition evaluates to true. This mechanism may provide faster
5639 response times depending on the performance characteristics of the target
5640 since it does not need to keep @value{GDBN} informed about
5641 every breakpoint trigger, even those with false conditions.
5643 Break conditions can be specified when a breakpoint is set, by using
5644 @samp{if} in the arguments to the @code{break} command. @xref{Set
5645 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5646 with the @code{condition} command.
5648 You can also use the @code{if} keyword with the @code{watch} command.
5649 The @code{catch} command does not recognize the @code{if} keyword;
5650 @code{condition} is the only way to impose a further condition on a
5655 @item condition @var{bnum} @var{expression}
5656 Specify @var{expression} as the break condition for breakpoint,
5657 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5658 breakpoint @var{bnum} stops your program only if the value of
5659 @var{expression} is true (nonzero, in C). When you use
5660 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5661 syntactic correctness, and to determine whether symbols in it have
5662 referents in the context of your breakpoint. If @var{expression} uses
5663 symbols not referenced in the context of the breakpoint, @value{GDBN}
5664 prints an error message:
5667 No symbol "foo" in current context.
5672 not actually evaluate @var{expression} at the time the @code{condition}
5673 command (or a command that sets a breakpoint with a condition, like
5674 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5676 @item condition -force @var{bnum} @var{expression}
5677 When the @code{-force} flag is used, define the condition even if
5678 @var{expression} is invalid at all the current locations of breakpoint
5679 @var{bnum}. This is similar to the @code{-force-condition} option
5680 of the @code{break} command.
5682 @item condition @var{bnum}
5683 Remove the condition from breakpoint number @var{bnum}. It becomes
5684 an ordinary unconditional breakpoint.
5687 @cindex ignore count (of breakpoint)
5688 A special case of a breakpoint condition is to stop only when the
5689 breakpoint has been reached a certain number of times. This is so
5690 useful that there is a special way to do it, using the @dfn{ignore
5691 count} of the breakpoint. Every breakpoint has an ignore count, which
5692 is an integer. Most of the time, the ignore count is zero, and
5693 therefore has no effect. But if your program reaches a breakpoint whose
5694 ignore count is positive, then instead of stopping, it just decrements
5695 the ignore count by one and continues. As a result, if the ignore count
5696 value is @var{n}, the breakpoint does not stop the next @var{n} times
5697 your program reaches it.
5701 @item ignore @var{bnum} @var{count}
5702 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5703 The next @var{count} times the breakpoint is reached, your program's
5704 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5707 To make the breakpoint stop the next time it is reached, specify
5710 When you use @code{continue} to resume execution of your program from a
5711 breakpoint, you can specify an ignore count directly as an argument to
5712 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5713 Stepping,,Continuing and Stepping}.
5715 If a breakpoint has a positive ignore count and a condition, the
5716 condition is not checked. Once the ignore count reaches zero,
5717 @value{GDBN} resumes checking the condition.
5719 You could achieve the effect of the ignore count with a condition such
5720 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5721 is decremented each time. @xref{Convenience Vars, ,Convenience
5725 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5728 @node Break Commands
5729 @subsection Breakpoint Command Lists
5731 @cindex breakpoint commands
5732 You can give any breakpoint (or watchpoint or catchpoint) a series of
5733 commands to execute when your program stops due to that breakpoint. For
5734 example, you might want to print the values of certain expressions, or
5735 enable other breakpoints.
5739 @kindex end@r{ (breakpoint commands)}
5740 @item commands @r{[}@var{list}@dots{}@r{]}
5741 @itemx @dots{} @var{command-list} @dots{}
5743 Specify a list of commands for the given breakpoints. The commands
5744 themselves appear on the following lines. Type a line containing just
5745 @code{end} to terminate the commands.
5747 To remove all commands from a breakpoint, type @code{commands} and
5748 follow it immediately with @code{end}; that is, give no commands.
5750 With no argument, @code{commands} refers to the last breakpoint,
5751 watchpoint, or catchpoint set (not to the breakpoint most recently
5752 encountered). If the most recent breakpoints were set with a single
5753 command, then the @code{commands} will apply to all the breakpoints
5754 set by that command. This applies to breakpoints set by
5755 @code{rbreak}, and also applies when a single @code{break} command
5756 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5760 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5761 disabled within a @var{command-list}.
5763 You can use breakpoint commands to start your program up again. Simply
5764 use the @code{continue} command, or @code{step}, or any other command
5765 that resumes execution.
5767 Any other commands in the command list, after a command that resumes
5768 execution, are ignored. This is because any time you resume execution
5769 (even with a simple @code{next} or @code{step}), you may encounter
5770 another breakpoint---which could have its own command list, leading to
5771 ambiguities about which list to execute.
5774 If the first command you specify in a command list is @code{silent}, the
5775 usual message about stopping at a breakpoint is not printed. This may
5776 be desirable for breakpoints that are to print a specific message and
5777 then continue. If none of the remaining commands print anything, you
5778 see no sign that the breakpoint was reached. @code{silent} is
5779 meaningful only at the beginning of a breakpoint command list.
5781 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5782 print precisely controlled output, and are often useful in silent
5783 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5785 For example, here is how you could use breakpoint commands to print the
5786 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5792 printf "x is %d\n",x
5797 One application for breakpoint commands is to compensate for one bug so
5798 you can test for another. Put a breakpoint just after the erroneous line
5799 of code, give it a condition to detect the case in which something
5800 erroneous has been done, and give it commands to assign correct values
5801 to any variables that need them. End with the @code{continue} command
5802 so that your program does not stop, and start with the @code{silent}
5803 command so that no output is produced. Here is an example:
5814 @node Dynamic Printf
5815 @subsection Dynamic Printf
5817 @cindex dynamic printf
5819 The dynamic printf command @code{dprintf} combines a breakpoint with
5820 formatted printing of your program's data to give you the effect of
5821 inserting @code{printf} calls into your program on-the-fly, without
5822 having to recompile it.
5824 In its most basic form, the output goes to the GDB console. However,
5825 you can set the variable @code{dprintf-style} for alternate handling.
5826 For instance, you can ask to format the output by calling your
5827 program's @code{printf} function. This has the advantage that the
5828 characters go to the program's output device, so they can recorded in
5829 redirects to files and so forth.
5831 If you are doing remote debugging with a stub or agent, you can also
5832 ask to have the printf handled by the remote agent. In addition to
5833 ensuring that the output goes to the remote program's device along
5834 with any other output the program might produce, you can also ask that
5835 the dprintf remain active even after disconnecting from the remote
5836 target. Using the stub/agent is also more efficient, as it can do
5837 everything without needing to communicate with @value{GDBN}.
5841 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
5842 Whenever execution reaches a code location that results from resolving
5843 @var{locspec}, print the values of one or more @var{expressions} under
5844 the control of the string @var{template}. To print several values,
5845 separate them with commas.
5847 @item set dprintf-style @var{style}
5848 Set the dprintf output to be handled in one of several different
5849 styles enumerated below. A change of style affects all existing
5850 dynamic printfs immediately. (If you need individual control over the
5851 print commands, simply define normal breakpoints with
5852 explicitly-supplied command lists.)
5856 @kindex dprintf-style gdb
5857 Handle the output using the @value{GDBN} @code{printf} command.
5860 @kindex dprintf-style call
5861 Handle the output by calling a function in your program (normally
5865 @kindex dprintf-style agent
5866 Have the remote debugging agent (such as @code{gdbserver}) handle
5867 the output itself. This style is only available for agents that
5868 support running commands on the target.
5871 @item set dprintf-function @var{function}
5872 Set the function to call if the dprintf style is @code{call}. By
5873 default its value is @code{printf}. You may set it to any expression.
5874 that @value{GDBN} can evaluate to a function, as per the @code{call}
5877 @item set dprintf-channel @var{channel}
5878 Set a ``channel'' for dprintf. If set to a non-empty value,
5879 @value{GDBN} will evaluate it as an expression and pass the result as
5880 a first argument to the @code{dprintf-function}, in the manner of
5881 @code{fprintf} and similar functions. Otherwise, the dprintf format
5882 string will be the first argument, in the manner of @code{printf}.
5884 As an example, if you wanted @code{dprintf} output to go to a logfile
5885 that is a standard I/O stream assigned to the variable @code{mylog},
5886 you could do the following:
5889 (gdb) set dprintf-style call
5890 (gdb) set dprintf-function fprintf
5891 (gdb) set dprintf-channel mylog
5892 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5893 Dprintf 1 at 0x123456: file main.c, line 25.
5895 1 dprintf keep y 0x00123456 in main at main.c:25
5896 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5901 Note that the @code{info break} displays the dynamic printf commands
5902 as normal breakpoint commands; you can thus easily see the effect of
5903 the variable settings.
5905 @item set disconnected-dprintf on
5906 @itemx set disconnected-dprintf off
5907 @kindex set disconnected-dprintf
5908 Choose whether @code{dprintf} commands should continue to run if
5909 @value{GDBN} has disconnected from the target. This only applies
5910 if the @code{dprintf-style} is @code{agent}.
5912 @item show disconnected-dprintf off
5913 @kindex show disconnected-dprintf
5914 Show the current choice for disconnected @code{dprintf}.
5918 @value{GDBN} does not check the validity of function and channel,
5919 relying on you to supply values that are meaningful for the contexts
5920 in which they are being used. For instance, the function and channel
5921 may be the values of local variables, but if that is the case, then
5922 all enabled dynamic prints must be at locations within the scope of
5923 those locals. If evaluation fails, @value{GDBN} will report an error.
5925 @node Save Breakpoints
5926 @subsection How to save breakpoints to a file
5928 To save breakpoint definitions to a file use the @w{@code{save
5929 breakpoints}} command.
5932 @kindex save breakpoints
5933 @cindex save breakpoints to a file for future sessions
5934 @item save breakpoints [@var{filename}]
5935 This command saves all current breakpoint definitions together with
5936 their commands and ignore counts, into a file @file{@var{filename}}
5937 suitable for use in a later debugging session. This includes all
5938 types of breakpoints (breakpoints, watchpoints, catchpoints,
5939 tracepoints). To read the saved breakpoint definitions, use the
5940 @code{source} command (@pxref{Command Files}). Note that watchpoints
5941 with expressions involving local variables may fail to be recreated
5942 because it may not be possible to access the context where the
5943 watchpoint is valid anymore. Because the saved breakpoint definitions
5944 are simply a sequence of @value{GDBN} commands that recreate the
5945 breakpoints, you can edit the file in your favorite editing program,
5946 and remove the breakpoint definitions you're not interested in, or
5947 that can no longer be recreated.
5950 @node Static Probe Points
5951 @subsection Static Probe Points
5953 @cindex static probe point, SystemTap
5954 @cindex static probe point, DTrace
5955 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5956 for Statically Defined Tracing, and the probes are designed to have a tiny
5957 runtime code and data footprint, and no dynamic relocations.
5959 Currently, the following types of probes are supported on
5960 ELF-compatible systems:
5964 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5965 @acronym{SDT} probes@footnote{See
5966 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5967 for more information on how to add @code{SystemTap} @acronym{SDT}
5968 probes in your applications.}. @code{SystemTap} probes are usable
5969 from assembly, C and C@t{++} languages@footnote{See
5970 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5971 for a good reference on how the @acronym{SDT} probes are implemented.}.
5973 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5974 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5978 @cindex semaphores on static probe points
5979 Some @code{SystemTap} probes have an associated semaphore variable;
5980 for instance, this happens automatically if you defined your probe
5981 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5982 @value{GDBN} will automatically enable it when you specify a
5983 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5984 breakpoint at a probe's location by some other method (e.g.,
5985 @code{break file:line}), then @value{GDBN} will not automatically set
5986 the semaphore. @code{DTrace} probes do not support semaphores.
5988 You can examine the available static static probes using @code{info
5989 probes}, with optional arguments:
5993 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5994 If given, @var{type} is either @code{stap} for listing
5995 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5996 probes. If omitted all probes are listed regardless of their types.
5998 If given, @var{provider} is a regular expression used to match against provider
5999 names when selecting which probes to list. If omitted, probes by all
6000 probes from all providers are listed.
6002 If given, @var{name} is a regular expression to match against probe names
6003 when selecting which probes to list. If omitted, probe names are not
6004 considered when deciding whether to display them.
6006 If given, @var{objfile} is a regular expression used to select which
6007 object files (executable or shared libraries) to examine. If not
6008 given, all object files are considered.
6010 @item info probes all
6011 List the available static probes, from all types.
6014 @cindex enabling and disabling probes
6015 Some probe points can be enabled and/or disabled. The effect of
6016 enabling or disabling a probe depends on the type of probe being
6017 handled. Some @code{DTrace} probes can be enabled or
6018 disabled, but @code{SystemTap} probes cannot be disabled.
6020 You can enable (or disable) one or more probes using the following
6021 commands, with optional arguments:
6024 @kindex enable probes
6025 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6026 If given, @var{provider} is a regular expression used to match against
6027 provider names when selecting which probes to enable. If omitted,
6028 all probes from all providers are enabled.
6030 If given, @var{name} is a regular expression to match against probe
6031 names when selecting which probes to enable. If omitted, probe names
6032 are not considered when deciding whether to enable them.
6034 If given, @var{objfile} is a regular expression used to select which
6035 object files (executable or shared libraries) to examine. If not
6036 given, all object files are considered.
6038 @kindex disable probes
6039 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6040 See the @code{enable probes} command above for a description of the
6041 optional arguments accepted by this command.
6044 @vindex $_probe_arg@r{, convenience variable}
6045 A probe may specify up to twelve arguments. These are available at the
6046 point at which the probe is defined---that is, when the current PC is
6047 at the probe's location. The arguments are available using the
6048 convenience variables (@pxref{Convenience Vars})
6049 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6050 probes each probe argument is an integer of the appropriate size;
6051 types are not preserved. In @code{DTrace} probes types are preserved
6052 provided that they are recognized as such by @value{GDBN}; otherwise
6053 the value of the probe argument will be a long integer. The
6054 convenience variable @code{$_probe_argc} holds the number of arguments
6055 at the current probe point.
6057 These variables are always available, but attempts to access them at
6058 any location other than a probe point will cause @value{GDBN} to give
6062 @c @ifclear BARETARGET
6063 @node Error in Breakpoints
6064 @subsection ``Cannot insert breakpoints''
6066 If you request too many active hardware-assisted breakpoints and
6067 watchpoints, you will see this error message:
6069 @c FIXME: the precise wording of this message may change; the relevant
6070 @c source change is not committed yet (Sep 3, 1999).
6072 Stopped; cannot insert breakpoints.
6073 You may have requested too many hardware breakpoints and watchpoints.
6077 This message is printed when you attempt to resume the program, since
6078 only then @value{GDBN} knows exactly how many hardware breakpoints and
6079 watchpoints it needs to insert.
6081 When this message is printed, you need to disable or remove some of the
6082 hardware-assisted breakpoints and watchpoints, and then continue.
6084 @node Breakpoint-related Warnings
6085 @subsection ``Breakpoint address adjusted...''
6086 @cindex breakpoint address adjusted
6088 Some processor architectures place constraints on the addresses at
6089 which breakpoints may be placed. For architectures thus constrained,
6090 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6091 with the constraints dictated by the architecture.
6093 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6094 a VLIW architecture in which a number of RISC-like instructions may be
6095 bundled together for parallel execution. The FR-V architecture
6096 constrains the location of a breakpoint instruction within such a
6097 bundle to the instruction with the lowest address. @value{GDBN}
6098 honors this constraint by adjusting a breakpoint's address to the
6099 first in the bundle.
6101 It is not uncommon for optimized code to have bundles which contain
6102 instructions from different source statements, thus it may happen that
6103 a breakpoint's address will be adjusted from one source statement to
6104 another. Since this adjustment may significantly alter @value{GDBN}'s
6105 breakpoint related behavior from what the user expects, a warning is
6106 printed when the breakpoint is first set and also when the breakpoint
6109 A warning like the one below is printed when setting a breakpoint
6110 that's been subject to address adjustment:
6113 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6116 Such warnings are printed both for user settable and @value{GDBN}'s
6117 internal breakpoints. If you see one of these warnings, you should
6118 verify that a breakpoint set at the adjusted address will have the
6119 desired affect. If not, the breakpoint in question may be removed and
6120 other breakpoints may be set which will have the desired behavior.
6121 E.g., it may be sufficient to place the breakpoint at a later
6122 instruction. A conditional breakpoint may also be useful in some
6123 cases to prevent the breakpoint from triggering too often.
6125 @value{GDBN} will also issue a warning when stopping at one of these
6126 adjusted breakpoints:
6129 warning: Breakpoint 1 address previously adjusted from 0x00010414
6133 When this warning is encountered, it may be too late to take remedial
6134 action except in cases where the breakpoint is hit earlier or more
6135 frequently than expected.
6137 @node Continuing and Stepping
6138 @section Continuing and Stepping
6142 @cindex resuming execution
6143 @dfn{Continuing} means resuming program execution until your program
6144 completes normally. In contrast, @dfn{stepping} means executing just
6145 one more ``step'' of your program, where ``step'' may mean either one
6146 line of source code, or one machine instruction (depending on what
6147 particular command you use). Either when continuing or when stepping,
6148 your program may stop even sooner, due to a breakpoint or a signal. (If
6149 it stops due to a signal, you may want to use @code{handle}, or use
6150 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6151 or you may step into the signal's handler (@pxref{stepping and signal
6156 @kindex c @r{(@code{continue})}
6157 @kindex fg @r{(resume foreground execution)}
6158 @item continue @r{[}@var{ignore-count}@r{]}
6159 @itemx c @r{[}@var{ignore-count}@r{]}
6160 @itemx fg @r{[}@var{ignore-count}@r{]}
6161 Resume program execution, at the address where your program last stopped;
6162 any breakpoints set at that address are bypassed. The optional argument
6163 @var{ignore-count} allows you to specify a further number of times to
6164 ignore a breakpoint at this location; its effect is like that of
6165 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6167 The argument @var{ignore-count} is meaningful only when your program
6168 stopped due to a breakpoint. At other times, the argument to
6169 @code{continue} is ignored.
6171 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6172 debugged program is deemed to be the foreground program) are provided
6173 purely for convenience, and have exactly the same behavior as
6177 To resume execution at a different place, you can use @code{return}
6178 (@pxref{Returning, ,Returning from a Function}) to go back to the
6179 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6180 Different Address}) to go to an arbitrary location in your program.
6182 A typical technique for using stepping is to set a breakpoint
6183 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6184 beginning of the function or the section of your program where a problem
6185 is believed to lie, run your program until it stops at that breakpoint,
6186 and then step through the suspect area, examining the variables that are
6187 interesting, until you see the problem happen.
6191 @kindex s @r{(@code{step})}
6193 Continue running your program until control reaches a different source
6194 line, then stop it and return control to @value{GDBN}. This command is
6195 abbreviated @code{s}.
6198 @c "without debugging information" is imprecise; actually "without line
6199 @c numbers in the debugging information". (gcc -g1 has debugging info but
6200 @c not line numbers). But it seems complex to try to make that
6201 @c distinction here.
6202 @emph{Warning:} If you use the @code{step} command while control is
6203 within a function that was compiled without debugging information,
6204 execution proceeds until control reaches a function that does have
6205 debugging information. Likewise, it will not step into a function which
6206 is compiled without debugging information. To step through functions
6207 without debugging information, use the @code{stepi} command, described
6211 The @code{step} command only stops at the first instruction of a source
6212 line. This prevents the multiple stops that could otherwise occur in
6213 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6214 to stop if a function that has debugging information is called within
6215 the line. In other words, @code{step} @emph{steps inside} any functions
6216 called within the line.
6218 Also, the @code{step} command only enters a function if there is line
6219 number information for the function. Otherwise it acts like the
6220 @code{next} command. This avoids problems when using @code{cc -gl}
6221 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6222 was any debugging information about the routine.
6224 @item step @var{count}
6225 Continue running as in @code{step}, but do so @var{count} times. If a
6226 breakpoint is reached, or a signal not related to stepping occurs before
6227 @var{count} steps, stepping stops right away.
6230 @kindex n @r{(@code{next})}
6231 @item next @r{[}@var{count}@r{]}
6232 Continue to the next source line in the current (innermost) stack frame.
6233 This is similar to @code{step}, but function calls that appear within
6234 the line of code are executed without stopping. Execution stops when
6235 control reaches a different line of code at the original stack level
6236 that was executing when you gave the @code{next} command. This command
6237 is abbreviated @code{n}.
6239 An argument @var{count} is a repeat count, as for @code{step}.
6242 @c FIX ME!! Do we delete this, or is there a way it fits in with
6243 @c the following paragraph? --- Vctoria
6245 @c @code{next} within a function that lacks debugging information acts like
6246 @c @code{step}, but any function calls appearing within the code of the
6247 @c function are executed without stopping.
6249 The @code{next} command only stops at the first instruction of a
6250 source line. This prevents multiple stops that could otherwise occur in
6251 @code{switch} statements, @code{for} loops, etc.
6253 @kindex set step-mode
6255 @cindex functions without line info, and stepping
6256 @cindex stepping into functions with no line info
6257 @itemx set step-mode on
6258 The @code{set step-mode on} command causes the @code{step} command to
6259 stop at the first instruction of a function which contains no debug line
6260 information rather than stepping over it.
6262 This is useful in cases where you may be interested in inspecting the
6263 machine instructions of a function which has no symbolic info and do not
6264 want @value{GDBN} to automatically skip over this function.
6266 @item set step-mode off
6267 Causes the @code{step} command to step over any functions which contains no
6268 debug information. This is the default.
6270 @item show step-mode
6271 Show whether @value{GDBN} will stop in or step over functions without
6272 source line debug information.
6275 @kindex fin @r{(@code{finish})}
6277 Continue running until just after function in the selected stack frame
6278 returns. Print the returned value (if any). This command can be
6279 abbreviated as @code{fin}.
6281 Contrast this with the @code{return} command (@pxref{Returning,
6282 ,Returning from a Function}).
6284 @kindex set print finish
6285 @kindex show print finish
6286 @item set print finish @r{[}on|off@r{]}
6287 @itemx show print finish
6288 By default the @code{finish} command will show the value that is
6289 returned by the function. This can be disabled using @code{set print
6290 finish off}. When disabled, the value is still entered into the value
6291 history (@pxref{Value History}), but not displayed.
6294 @kindex u @r{(@code{until})}
6295 @cindex run until specified location
6298 Continue running until a source line past the current line, in the
6299 current stack frame, is reached. This command is used to avoid single
6300 stepping through a loop more than once. It is like the @code{next}
6301 command, except that when @code{until} encounters a jump, it
6302 automatically continues execution until the program counter is greater
6303 than the address of the jump.
6305 This means that when you reach the end of a loop after single stepping
6306 though it, @code{until} makes your program continue execution until it
6307 exits the loop. In contrast, a @code{next} command at the end of a loop
6308 simply steps back to the beginning of the loop, which forces you to step
6309 through the next iteration.
6311 @code{until} always stops your program if it attempts to exit the current
6314 @code{until} may produce somewhat counterintuitive results if the order
6315 of machine code does not match the order of the source lines. For
6316 example, in the following excerpt from a debugging session, the @code{f}
6317 (@code{frame}) command shows that execution is stopped at line
6318 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6322 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6324 (@value{GDBP}) until
6325 195 for ( ; argc > 0; NEXTARG) @{
6328 This happened because, for execution efficiency, the compiler had
6329 generated code for the loop closure test at the end, rather than the
6330 start, of the loop---even though the test in a C @code{for}-loop is
6331 written before the body of the loop. The @code{until} command appeared
6332 to step back to the beginning of the loop when it advanced to this
6333 expression; however, it has not really gone to an earlier
6334 statement---not in terms of the actual machine code.
6336 @code{until} with no argument works by means of single
6337 instruction stepping, and hence is slower than @code{until} with an
6340 @item until @var{locspec}
6341 @itemx u @var{locspec}
6342 Continue running your program until either it reaches a code location
6343 that results from resolving @var{locspec}, or the current stack frame
6344 returns. @var{locspec} is any of the forms described in @ref{Location
6346 This form of the command uses temporary breakpoints, and
6347 hence is quicker than @code{until} without an argument. The specified
6348 location is actually reached only if it is in the current frame. This
6349 implies that @code{until} can be used to skip over recursive function
6350 invocations. For instance in the code below, if the current location is
6351 line @code{96}, issuing @code{until 99} will execute the program up to
6352 line @code{99} in the same invocation of factorial, i.e., after the inner
6353 invocations have returned.
6356 94 int factorial (int value)
6358 96 if (value > 1) @{
6359 97 value *= factorial (value - 1);
6366 @kindex advance @var{locspec}
6367 @item advance @var{locspec}
6368 Continue running your program until either it reaches a code location
6369 that results from resolving @var{locspec}, or the current stack frame
6370 returns. @var{locspec} is any of the forms described in @ref{Location
6371 Specifications}. This command is similar to @code{until}, but
6372 @code{advance} will not skip over recursive function calls, and the
6373 target code location doesn't have to be in the same frame as the
6378 @kindex si @r{(@code{stepi})}
6380 @itemx stepi @var{arg}
6382 Execute one machine instruction, then stop and return to the debugger.
6384 It is often useful to do @samp{display/i $pc} when stepping by machine
6385 instructions. This makes @value{GDBN} automatically display the next
6386 instruction to be executed, each time your program stops. @xref{Auto
6387 Display,, Automatic Display}.
6389 An argument is a repeat count, as in @code{step}.
6393 @kindex ni @r{(@code{nexti})}
6395 @itemx nexti @var{arg}
6397 Execute one machine instruction, but if it is a function call,
6398 proceed until the function returns.
6400 An argument is a repeat count, as in @code{next}.
6404 @anchor{range stepping}
6405 @cindex range stepping
6406 @cindex target-assisted range stepping
6407 By default, and if available, @value{GDBN} makes use of
6408 target-assisted @dfn{range stepping}. In other words, whenever you
6409 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6410 tells the target to step the corresponding range of instruction
6411 addresses instead of issuing multiple single-steps. This speeds up
6412 line stepping, particularly for remote targets. Ideally, there should
6413 be no reason you would want to turn range stepping off. However, it's
6414 possible that a bug in the debug info, a bug in the remote stub (for
6415 remote targets), or even a bug in @value{GDBN} could make line
6416 stepping behave incorrectly when target-assisted range stepping is
6417 enabled. You can use the following command to turn off range stepping
6421 @kindex set range-stepping
6422 @kindex show range-stepping
6423 @item set range-stepping
6424 @itemx show range-stepping
6425 Control whether range stepping is enabled.
6427 If @code{on}, and the target supports it, @value{GDBN} tells the
6428 target to step a range of addresses itself, instead of issuing
6429 multiple single-steps. If @code{off}, @value{GDBN} always issues
6430 single-steps, even if range stepping is supported by the target. The
6431 default is @code{on}.
6435 @node Skipping Over Functions and Files
6436 @section Skipping Over Functions and Files
6437 @cindex skipping over functions and files
6439 The program you are debugging may contain some functions which are
6440 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6441 skip a function, all functions in a file or a particular function in
6442 a particular file when stepping.
6444 For example, consider the following C function:
6455 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6456 are not interested in stepping through @code{boring}. If you run @code{step}
6457 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6458 step over both @code{foo} and @code{boring}!
6460 One solution is to @code{step} into @code{boring} and use the @code{finish}
6461 command to immediately exit it. But this can become tedious if @code{boring}
6462 is called from many places.
6464 A more flexible solution is to execute @kbd{skip boring}. This instructs
6465 @value{GDBN} never to step into @code{boring}. Now when you execute
6466 @code{step} at line 103, you'll step over @code{boring} and directly into
6469 Functions may be skipped by providing either a function name, linespec
6470 (@pxref{Location Specifications}), regular expression that matches the function's
6471 name, file name or a @code{glob}-style pattern that matches the file name.
6473 On Posix systems the form of the regular expression is
6474 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6475 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6476 expression is whatever is provided by the @code{regcomp} function of
6477 the underlying system.
6478 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6479 description of @code{glob}-style patterns.
6483 @item skip @r{[}@var{options}@r{]}
6484 The basic form of the @code{skip} command takes zero or more options
6485 that specify what to skip.
6486 The @var{options} argument is any useful combination of the following:
6489 @item -file @var{file}
6490 @itemx -fi @var{file}
6491 Functions in @var{file} will be skipped over when stepping.
6493 @item -gfile @var{file-glob-pattern}
6494 @itemx -gfi @var{file-glob-pattern}
6495 @cindex skipping over files via glob-style patterns
6496 Functions in files matching @var{file-glob-pattern} will be skipped
6500 (gdb) skip -gfi utils/*.c
6503 @item -function @var{linespec}
6504 @itemx -fu @var{linespec}
6505 Functions named by @var{linespec} or the function containing the line
6506 named by @var{linespec} will be skipped over when stepping.
6507 @xref{Location Specifications}.
6509 @item -rfunction @var{regexp}
6510 @itemx -rfu @var{regexp}
6511 @cindex skipping over functions via regular expressions
6512 Functions whose name matches @var{regexp} will be skipped over when stepping.
6514 This form is useful for complex function names.
6515 For example, there is generally no need to step into C@t{++} @code{std::string}
6516 constructors or destructors. Plus with C@t{++} templates it can be hard to
6517 write out the full name of the function, and often it doesn't matter what
6518 the template arguments are. Specifying the function to be skipped as a
6519 regular expression makes this easier.
6522 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6525 If you want to skip every templated C@t{++} constructor and destructor
6526 in the @code{std} namespace you can do:
6529 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6533 If no options are specified, the function you're currently debugging
6536 @kindex skip function
6537 @item skip function @r{[}@var{linespec}@r{]}
6538 After running this command, the function named by @var{linespec} or the
6539 function containing the line named by @var{linespec} will be skipped over when
6540 stepping. @xref{Location Specifications}.
6542 If you do not specify @var{linespec}, the function you're currently debugging
6545 (If you have a function called @code{file} that you want to skip, use
6546 @kbd{skip function file}.)
6549 @item skip file @r{[}@var{filename}@r{]}
6550 After running this command, any function whose source lives in @var{filename}
6551 will be skipped over when stepping.
6554 (gdb) skip file boring.c
6555 File boring.c will be skipped when stepping.
6558 If you do not specify @var{filename}, functions whose source lives in the file
6559 you're currently debugging will be skipped.
6562 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6563 These are the commands for managing your list of skips:
6567 @item info skip @r{[}@var{range}@r{]}
6568 Print details about the specified skip(s). If @var{range} is not specified,
6569 print a table with details about all functions and files marked for skipping.
6570 @code{info skip} prints the following information about each skip:
6574 A number identifying this skip.
6575 @item Enabled or Disabled
6576 Enabled skips are marked with @samp{y}.
6577 Disabled skips are marked with @samp{n}.
6579 If the file name is a @samp{glob} pattern this is @samp{y}.
6580 Otherwise it is @samp{n}.
6582 The name or @samp{glob} pattern of the file to be skipped.
6583 If no file is specified this is @samp{<none>}.
6585 If the function name is a @samp{regular expression} this is @samp{y}.
6586 Otherwise it is @samp{n}.
6588 The name or regular expression of the function to skip.
6589 If no function is specified this is @samp{<none>}.
6593 @item skip delete @r{[}@var{range}@r{]}
6594 Delete the specified skip(s). If @var{range} is not specified, delete all
6598 @item skip enable @r{[}@var{range}@r{]}
6599 Enable the specified skip(s). If @var{range} is not specified, enable all
6602 @kindex skip disable
6603 @item skip disable @r{[}@var{range}@r{]}
6604 Disable the specified skip(s). If @var{range} is not specified, disable all
6607 @kindex set debug skip
6608 @item set debug skip @r{[}on|off@r{]}
6609 Set whether to print the debug output about skipping files and functions.
6611 @kindex show debug skip
6612 @item show debug skip
6613 Show whether the debug output about skipping files and functions is printed.
6621 A signal is an asynchronous event that can happen in a program. The
6622 operating system defines the possible kinds of signals, and gives each
6623 kind a name and a number. For example, in Unix @code{SIGINT} is the
6624 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6625 @code{SIGSEGV} is the signal a program gets from referencing a place in
6626 memory far away from all the areas in use; @code{SIGALRM} occurs when
6627 the alarm clock timer goes off (which happens only if your program has
6628 requested an alarm).
6630 @cindex fatal signals
6631 Some signals, including @code{SIGALRM}, are a normal part of the
6632 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6633 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6634 program has not specified in advance some other way to handle the signal.
6635 @code{SIGINT} does not indicate an error in your program, but it is normally
6636 fatal so it can carry out the purpose of the interrupt: to kill the program.
6638 @value{GDBN} has the ability to detect any occurrence of a signal in your
6639 program. You can tell @value{GDBN} in advance what to do for each kind of
6642 @cindex handling signals
6643 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6644 @code{SIGALRM} be silently passed to your program
6645 (so as not to interfere with their role in the program's functioning)
6646 but to stop your program immediately whenever an error signal happens.
6647 You can change these settings with the @code{handle} command.
6650 @kindex info signals
6654 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6655 handle each one. You can use this to see the signal numbers of all
6656 the defined types of signals.
6658 @item info signals @var{sig}
6659 Similar, but print information only about the specified signal number.
6661 @code{info handle} is an alias for @code{info signals}.
6663 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6664 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6665 for details about this command.
6668 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6669 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6670 can be the number of a signal or its name (with or without the
6671 @samp{SIG} at the beginning); a list of signal numbers of the form
6672 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6673 known signals. Optional arguments @var{keywords}, described below,
6674 say what change to make.
6678 The keywords allowed by the @code{handle} command can be abbreviated.
6679 Their full names are:
6683 @value{GDBN} should not stop your program when this signal happens. It may
6684 still print a message telling you that the signal has come in.
6687 @value{GDBN} should stop your program when this signal happens. This implies
6688 the @code{print} keyword as well.
6691 @value{GDBN} should print a message when this signal happens.
6694 @value{GDBN} should not mention the occurrence of the signal at all. This
6695 implies the @code{nostop} keyword as well.
6699 @value{GDBN} should allow your program to see this signal; your program
6700 can handle the signal, or else it may terminate if the signal is fatal
6701 and not handled. @code{pass} and @code{noignore} are synonyms.
6705 @value{GDBN} should not allow your program to see this signal.
6706 @code{nopass} and @code{ignore} are synonyms.
6710 When a signal stops your program, the signal is not visible to the
6712 continue. Your program sees the signal then, if @code{pass} is in
6713 effect for the signal in question @emph{at that time}. In other words,
6714 after @value{GDBN} reports a signal, you can use the @code{handle}
6715 command with @code{pass} or @code{nopass} to control whether your
6716 program sees that signal when you continue.
6718 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6719 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6720 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6723 You can also use the @code{signal} command to prevent your program from
6724 seeing a signal, or cause it to see a signal it normally would not see,
6725 or to give it any signal at any time. For example, if your program stopped
6726 due to some sort of memory reference error, you might store correct
6727 values into the erroneous variables and continue, hoping to see more
6728 execution; but your program would probably terminate immediately as
6729 a result of the fatal signal once it saw the signal. To prevent this,
6730 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6733 @cindex stepping and signal handlers
6734 @anchor{stepping and signal handlers}
6736 @value{GDBN} optimizes for stepping the mainline code. If a signal
6737 that has @code{handle nostop} and @code{handle pass} set arrives while
6738 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6739 in progress, @value{GDBN} lets the signal handler run and then resumes
6740 stepping the mainline code once the signal handler returns. In other
6741 words, @value{GDBN} steps over the signal handler. This prevents
6742 signals that you've specified as not interesting (with @code{handle
6743 nostop}) from changing the focus of debugging unexpectedly. Note that
6744 the signal handler itself may still hit a breakpoint, stop for another
6745 signal that has @code{handle stop} in effect, or for any other event
6746 that normally results in stopping the stepping command sooner. Also
6747 note that @value{GDBN} still informs you that the program received a
6748 signal if @code{handle print} is set.
6750 @anchor{stepping into signal handlers}
6752 If you set @code{handle pass} for a signal, and your program sets up a
6753 handler for it, then issuing a stepping command, such as @code{step}
6754 or @code{stepi}, when your program is stopped due to the signal will
6755 step @emph{into} the signal handler (if the target supports that).
6757 Likewise, if you use the @code{queue-signal} command to queue a signal
6758 to be delivered to the current thread when execution of the thread
6759 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6760 stepping command will step into the signal handler.
6762 Here's an example, using @code{stepi} to step to the first instruction
6763 of @code{SIGUSR1}'s handler:
6766 (@value{GDBP}) handle SIGUSR1
6767 Signal Stop Print Pass to program Description
6768 SIGUSR1 Yes Yes Yes User defined signal 1
6772 Program received signal SIGUSR1, User defined signal 1.
6773 main () sigusr1.c:28
6776 sigusr1_handler () at sigusr1.c:9
6780 The same, but using @code{queue-signal} instead of waiting for the
6781 program to receive the signal first:
6786 (@value{GDBP}) queue-signal SIGUSR1
6788 sigusr1_handler () at sigusr1.c:9
6793 @cindex extra signal information
6794 @anchor{extra signal information}
6796 On some targets, @value{GDBN} can inspect extra signal information
6797 associated with the intercepted signal, before it is actually
6798 delivered to the program being debugged. This information is exported
6799 by the convenience variable @code{$_siginfo}, and consists of data
6800 that is passed by the kernel to the signal handler at the time of the
6801 receipt of a signal. The data type of the information itself is
6802 target dependent. You can see the data type using the @code{ptype
6803 $_siginfo} command. On Unix systems, it typically corresponds to the
6804 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6807 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6808 referenced address that raised a segmentation fault.
6812 (@value{GDBP}) continue
6813 Program received signal SIGSEGV, Segmentation fault.
6814 0x0000000000400766 in main ()
6816 (@value{GDBP}) ptype $_siginfo
6823 struct @{...@} _kill;
6824 struct @{...@} _timer;
6826 struct @{...@} _sigchld;
6827 struct @{...@} _sigfault;
6828 struct @{...@} _sigpoll;
6831 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6835 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6836 $1 = (void *) 0x7ffff7ff7000
6840 Depending on target support, @code{$_siginfo} may also be writable.
6842 @cindex Intel MPX boundary violations
6843 @cindex boundary violations, Intel MPX
6844 On some targets, a @code{SIGSEGV} can be caused by a boundary
6845 violation, i.e., accessing an address outside of the allowed range.
6846 In those cases @value{GDBN} may displays additional information,
6847 depending on how @value{GDBN} has been told to handle the signal.
6848 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6849 kind: "Upper" or "Lower", the memory address accessed and the
6850 bounds, while with @code{handle nostop SIGSEGV} no additional
6851 information is displayed.
6853 The usual output of a segfault is:
6855 Program received signal SIGSEGV, Segmentation fault
6856 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6857 68 value = *(p + len);
6860 While a bound violation is presented as:
6862 Program received signal SIGSEGV, Segmentation fault
6863 Upper bound violation while accessing address 0x7fffffffc3b3
6864 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6865 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6866 68 value = *(p + len);
6870 @section Stopping and Starting Multi-thread Programs
6872 @cindex stopped threads
6873 @cindex threads, stopped
6875 @cindex continuing threads
6876 @cindex threads, continuing
6878 @value{GDBN} supports debugging programs with multiple threads
6879 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6880 are two modes of controlling execution of your program within the
6881 debugger. In the default mode, referred to as @dfn{all-stop mode},
6882 when any thread in your program stops (for example, at a breakpoint
6883 or while being stepped), all other threads in the program are also stopped by
6884 @value{GDBN}. On some targets, @value{GDBN} also supports
6885 @dfn{non-stop mode}, in which other threads can continue to run freely while
6886 you examine the stopped thread in the debugger.
6889 * All-Stop Mode:: All threads stop when GDB takes control
6890 * Non-Stop Mode:: Other threads continue to execute
6891 * Background Execution:: Running your program asynchronously
6892 * Thread-Specific Breakpoints:: Controlling breakpoints
6893 * Interrupted System Calls:: GDB may interfere with system calls
6894 * Observer Mode:: GDB does not alter program behavior
6898 @subsection All-Stop Mode
6900 @cindex all-stop mode
6902 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6903 @emph{all} threads of execution stop, not just the current thread. This
6904 allows you to examine the overall state of the program, including
6905 switching between threads, without worrying that things may change
6908 Conversely, whenever you restart the program, @emph{all} threads start
6909 executing. @emph{This is true even when single-stepping} with commands
6910 like @code{step} or @code{next}.
6912 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6913 Since thread scheduling is up to your debugging target's operating
6914 system (not controlled by @value{GDBN}), other threads may
6915 execute more than one statement while the current thread completes a
6916 single step. Moreover, in general other threads stop in the middle of a
6917 statement, rather than at a clean statement boundary, when the program
6920 You might even find your program stopped in another thread after
6921 continuing or even single-stepping. This happens whenever some other
6922 thread runs into a breakpoint, a signal, or an exception before the
6923 first thread completes whatever you requested.
6925 @cindex automatic thread selection
6926 @cindex switching threads automatically
6927 @cindex threads, automatic switching
6928 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6929 signal, it automatically selects the thread where that breakpoint or
6930 signal happened. @value{GDBN} alerts you to the context switch with a
6931 message such as @samp{[Switching to Thread @var{n}]} to identify the
6934 On some OSes, you can modify @value{GDBN}'s default behavior by
6935 locking the OS scheduler to allow only a single thread to run.
6938 @item set scheduler-locking @var{mode}
6939 @cindex scheduler locking mode
6940 @cindex lock scheduler
6941 Set the scheduler locking mode. It applies to normal execution,
6942 record mode, and replay mode. @var{mode} can be one of
6947 There is no locking and any thread may run at any time.
6950 Only the current thread may run when the inferior is resumed.
6953 Behaves like @code{on} when stepping, and @code{off} otherwise.
6954 Threads other than the current never get a chance to run when you
6955 step, and they are completely free to run when you use commands like
6956 @samp{continue}, @samp{until}, or @samp{finish}.
6958 This mode optimizes for single-stepping; it prevents other threads
6959 from preempting the current thread while you are stepping, so that the
6960 focus of debugging does not change unexpectedly. However, unless
6961 another thread hits a breakpoint during its timeslice, @value{GDBN}
6962 does not change the current thread away from the thread that you are
6966 Behaves like @code{on} in replay mode, and @code{off} in either record
6967 mode or during normal execution. This is the default mode.
6970 @item show scheduler-locking
6971 Display the current scheduler locking mode.
6974 @cindex resume threads of multiple processes simultaneously
6975 By default, when you issue one of the execution commands such as
6976 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6977 threads of the current inferior to run. For example, if @value{GDBN}
6978 is attached to two inferiors, each with two threads, the
6979 @code{continue} command resumes only the two threads of the current
6980 inferior. This is useful, for example, when you debug a program that
6981 forks and you want to hold the parent stopped (so that, for instance,
6982 it doesn't run to exit), while you debug the child. In other
6983 situations, you may not be interested in inspecting the current state
6984 of any of the processes @value{GDBN} is attached to, and you may want
6985 to resume them all until some breakpoint is hit. In the latter case,
6986 you can instruct @value{GDBN} to allow all threads of all the
6987 inferiors to run with the @w{@code{set schedule-multiple}} command.
6990 @kindex set schedule-multiple
6991 @item set schedule-multiple
6992 Set the mode for allowing threads of multiple processes to be resumed
6993 when an execution command is issued. When @code{on}, all threads of
6994 all processes are allowed to run. When @code{off}, only the threads
6995 of the current process are resumed. The default is @code{off}. The
6996 @code{scheduler-locking} mode takes precedence when set to @code{on},
6997 or while you are stepping and set to @code{step}.
6999 @item show schedule-multiple
7000 Display the current mode for resuming the execution of threads of
7005 @subsection Non-Stop Mode
7007 @cindex non-stop mode
7009 @c This section is really only a place-holder, and needs to be expanded
7010 @c with more details.
7012 For some multi-threaded targets, @value{GDBN} supports an optional
7013 mode of operation in which you can examine stopped program threads in
7014 the debugger while other threads continue to execute freely. This
7015 minimizes intrusion when debugging live systems, such as programs
7016 where some threads have real-time constraints or must continue to
7017 respond to external events. This is referred to as @dfn{non-stop} mode.
7019 In non-stop mode, when a thread stops to report a debugging event,
7020 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7021 threads as well, in contrast to the all-stop mode behavior. Additionally,
7022 execution commands such as @code{continue} and @code{step} apply by default
7023 only to the current thread in non-stop mode, rather than all threads as
7024 in all-stop mode. This allows you to control threads explicitly in
7025 ways that are not possible in all-stop mode --- for example, stepping
7026 one thread while allowing others to run freely, stepping
7027 one thread while holding all others stopped, or stepping several threads
7028 independently and simultaneously.
7030 To enter non-stop mode, use this sequence of commands before you run
7031 or attach to your program:
7034 # If using the CLI, pagination breaks non-stop.
7037 # Finally, turn it on!
7041 You can use these commands to manipulate the non-stop mode setting:
7044 @kindex set non-stop
7045 @item set non-stop on
7046 Enable selection of non-stop mode.
7047 @item set non-stop off
7048 Disable selection of non-stop mode.
7049 @kindex show non-stop
7051 Show the current non-stop enablement setting.
7054 Note these commands only reflect whether non-stop mode is enabled,
7055 not whether the currently-executing program is being run in non-stop mode.
7056 In particular, the @code{set non-stop} preference is only consulted when
7057 @value{GDBN} starts or connects to the target program, and it is generally
7058 not possible to switch modes once debugging has started. Furthermore,
7059 since not all targets support non-stop mode, even when you have enabled
7060 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7063 In non-stop mode, all execution commands apply only to the current thread
7064 by default. That is, @code{continue} only continues one thread.
7065 To continue all threads, issue @code{continue -a} or @code{c -a}.
7067 You can use @value{GDBN}'s background execution commands
7068 (@pxref{Background Execution}) to run some threads in the background
7069 while you continue to examine or step others from @value{GDBN}.
7070 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7071 always executed asynchronously in non-stop mode.
7073 Suspending execution is done with the @code{interrupt} command when
7074 running in the background, or @kbd{Ctrl-c} during foreground execution.
7075 In all-stop mode, this stops the whole process;
7076 but in non-stop mode the interrupt applies only to the current thread.
7077 To stop the whole program, use @code{interrupt -a}.
7079 Other execution commands do not currently support the @code{-a} option.
7081 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7082 that thread current, as it does in all-stop mode. This is because the
7083 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7084 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7085 changed to a different thread just as you entered a command to operate on the
7086 previously current thread.
7088 @node Background Execution
7089 @subsection Background Execution
7091 @cindex foreground execution
7092 @cindex background execution
7093 @cindex asynchronous execution
7094 @cindex execution, foreground, background and asynchronous
7096 @value{GDBN}'s execution commands have two variants: the normal
7097 foreground (synchronous) behavior, and a background
7098 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7099 the program to report that some thread has stopped before prompting for
7100 another command. In background execution, @value{GDBN} immediately gives
7101 a command prompt so that you can issue other commands while your program runs.
7103 If the target doesn't support async mode, @value{GDBN} issues an error
7104 message if you attempt to use the background execution commands.
7106 @cindex @code{&}, background execution of commands
7107 To specify background execution, add a @code{&} to the command. For example,
7108 the background form of the @code{continue} command is @code{continue&}, or
7109 just @code{c&}. The execution commands that accept background execution
7115 @xref{Starting, , Starting your Program}.
7119 @xref{Attach, , Debugging an Already-running Process}.
7123 @xref{Continuing and Stepping, step}.
7127 @xref{Continuing and Stepping, stepi}.
7131 @xref{Continuing and Stepping, next}.
7135 @xref{Continuing and Stepping, nexti}.
7139 @xref{Continuing and Stepping, continue}.
7143 @xref{Continuing and Stepping, finish}.
7147 @xref{Continuing and Stepping, until}.
7151 Background execution is especially useful in conjunction with non-stop
7152 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7153 However, you can also use these commands in the normal all-stop mode with
7154 the restriction that you cannot issue another execution command until the
7155 previous one finishes. Examples of commands that are valid in all-stop
7156 mode while the program is running include @code{help} and @code{info break}.
7158 You can interrupt your program while it is running in the background by
7159 using the @code{interrupt} command.
7166 Suspend execution of the running program. In all-stop mode,
7167 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7168 only the current thread. To stop the whole program in non-stop mode,
7169 use @code{interrupt -a}.
7172 @node Thread-Specific Breakpoints
7173 @subsection Thread-Specific Breakpoints
7175 When your program has multiple threads (@pxref{Threads,, Debugging
7176 Programs with Multiple Threads}), you can choose whether to set
7177 breakpoints on all threads, or on a particular thread.
7180 @cindex breakpoints and threads
7181 @cindex thread breakpoints
7182 @kindex break @dots{} thread @var{thread-id}
7183 @item break @var{locspec} thread @var{thread-id}
7184 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7185 @var{locspec} specifies a code location or locations in your program.
7186 @xref{Location Specifications}, for details.
7188 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7189 to specify that you only want @value{GDBN} to stop the program when a
7190 particular thread reaches this breakpoint. The @var{thread-id} specifier
7191 is one of the thread identifiers assigned by @value{GDBN}, shown
7192 in the first column of the @samp{info threads} display.
7194 If you do not specify @samp{thread @var{thread-id}} when you set a
7195 breakpoint, the breakpoint applies to @emph{all} threads of your
7198 You can use the @code{thread} qualifier on conditional breakpoints as
7199 well; in this case, place @samp{thread @var{thread-id}} before or
7200 after the breakpoint condition, like this:
7203 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7208 Thread-specific breakpoints are automatically deleted when
7209 @value{GDBN} detects the corresponding thread is no longer in the
7210 thread list. For example:
7214 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7217 There are several ways for a thread to disappear, such as a regular
7218 thread exit, but also when you detach from the process with the
7219 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7220 Process}), or if @value{GDBN} loses the remote connection
7221 (@pxref{Remote Debugging}), etc. Note that with some targets,
7222 @value{GDBN} is only able to detect a thread has exited when the user
7223 explictly asks for the thread list with the @code{info threads}
7226 @node Interrupted System Calls
7227 @subsection Interrupted System Calls
7229 @cindex thread breakpoints and system calls
7230 @cindex system calls and thread breakpoints
7231 @cindex premature return from system calls
7232 There is an unfortunate side effect when using @value{GDBN} to debug
7233 multi-threaded programs. If one thread stops for a
7234 breakpoint, or for some other reason, and another thread is blocked in a
7235 system call, then the system call may return prematurely. This is a
7236 consequence of the interaction between multiple threads and the signals
7237 that @value{GDBN} uses to implement breakpoints and other events that
7240 To handle this problem, your program should check the return value of
7241 each system call and react appropriately. This is good programming
7244 For example, do not write code like this:
7250 The call to @code{sleep} will return early if a different thread stops
7251 at a breakpoint or for some other reason.
7253 Instead, write this:
7258 unslept = sleep (unslept);
7261 A system call is allowed to return early, so the system is still
7262 conforming to its specification. But @value{GDBN} does cause your
7263 multi-threaded program to behave differently than it would without
7266 Also, @value{GDBN} uses internal breakpoints in the thread library to
7267 monitor certain events such as thread creation and thread destruction.
7268 When such an event happens, a system call in another thread may return
7269 prematurely, even though your program does not appear to stop.
7272 @subsection Observer Mode
7274 If you want to build on non-stop mode and observe program behavior
7275 without any chance of disruption by @value{GDBN}, you can set
7276 variables to disable all of the debugger's attempts to modify state,
7277 whether by writing memory, inserting breakpoints, etc. These operate
7278 at a low level, intercepting operations from all commands.
7280 When all of these are set to @code{off}, then @value{GDBN} is said to
7281 be @dfn{observer mode}. As a convenience, the variable
7282 @code{observer} can be set to disable these, plus enable non-stop
7285 Note that @value{GDBN} will not prevent you from making nonsensical
7286 combinations of these settings. For instance, if you have enabled
7287 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7288 then breakpoints that work by writing trap instructions into the code
7289 stream will still not be able to be placed.
7294 @item set observer on
7295 @itemx set observer off
7296 When set to @code{on}, this disables all the permission variables
7297 below (except for @code{insert-fast-tracepoints}), plus enables
7298 non-stop debugging. Setting this to @code{off} switches back to
7299 normal debugging, though remaining in non-stop mode.
7302 Show whether observer mode is on or off.
7304 @kindex may-write-registers
7305 @item set may-write-registers on
7306 @itemx set may-write-registers off
7307 This controls whether @value{GDBN} will attempt to alter the values of
7308 registers, such as with assignment expressions in @code{print}, or the
7309 @code{jump} command. It defaults to @code{on}.
7311 @item show may-write-registers
7312 Show the current permission to write registers.
7314 @kindex may-write-memory
7315 @item set may-write-memory on
7316 @itemx set may-write-memory off
7317 This controls whether @value{GDBN} will attempt to alter the contents
7318 of memory, such as with assignment expressions in @code{print}. It
7319 defaults to @code{on}.
7321 @item show may-write-memory
7322 Show the current permission to write memory.
7324 @kindex may-insert-breakpoints
7325 @item set may-insert-breakpoints on
7326 @itemx set may-insert-breakpoints off
7327 This controls whether @value{GDBN} will attempt to insert breakpoints.
7328 This affects all breakpoints, including internal breakpoints defined
7329 by @value{GDBN}. It defaults to @code{on}.
7331 @item show may-insert-breakpoints
7332 Show the current permission to insert breakpoints.
7334 @kindex may-insert-tracepoints
7335 @item set may-insert-tracepoints on
7336 @itemx set may-insert-tracepoints off
7337 This controls whether @value{GDBN} will attempt to insert (regular)
7338 tracepoints at the beginning of a tracing experiment. It affects only
7339 non-fast tracepoints, fast tracepoints being under the control of
7340 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7342 @item show may-insert-tracepoints
7343 Show the current permission to insert tracepoints.
7345 @kindex may-insert-fast-tracepoints
7346 @item set may-insert-fast-tracepoints on
7347 @itemx set may-insert-fast-tracepoints off
7348 This controls whether @value{GDBN} will attempt to insert fast
7349 tracepoints at the beginning of a tracing experiment. It affects only
7350 fast tracepoints, regular (non-fast) tracepoints being under the
7351 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7353 @item show may-insert-fast-tracepoints
7354 Show the current permission to insert fast tracepoints.
7356 @kindex may-interrupt
7357 @item set may-interrupt on
7358 @itemx set may-interrupt off
7359 This controls whether @value{GDBN} will attempt to interrupt or stop
7360 program execution. When this variable is @code{off}, the
7361 @code{interrupt} command will have no effect, nor will
7362 @kbd{Ctrl-c}. It defaults to @code{on}.
7364 @item show may-interrupt
7365 Show the current permission to interrupt or stop the program.
7369 @node Reverse Execution
7370 @chapter Running programs backward
7371 @cindex reverse execution
7372 @cindex running programs backward
7374 When you are debugging a program, it is not unusual to realize that
7375 you have gone too far, and some event of interest has already happened.
7376 If the target environment supports it, @value{GDBN} can allow you to
7377 ``rewind'' the program by running it backward.
7379 A target environment that supports reverse execution should be able
7380 to ``undo'' the changes in machine state that have taken place as the
7381 program was executing normally. Variables, registers etc.@: should
7382 revert to their previous values. Obviously this requires a great
7383 deal of sophistication on the part of the target environment; not
7384 all target environments can support reverse execution.
7386 When a program is executed in reverse, the instructions that
7387 have most recently been executed are ``un-executed'', in reverse
7388 order. The program counter runs backward, following the previous
7389 thread of execution in reverse. As each instruction is ``un-executed'',
7390 the values of memory and/or registers that were changed by that
7391 instruction are reverted to their previous states. After executing
7392 a piece of source code in reverse, all side effects of that code
7393 should be ``undone'', and all variables should be returned to their
7394 prior values@footnote{
7395 Note that some side effects are easier to undo than others. For instance,
7396 memory and registers are relatively easy, but device I/O is hard. Some
7397 targets may be able undo things like device I/O, and some may not.
7399 The contract between @value{GDBN} and the reverse executing target
7400 requires only that the target do something reasonable when
7401 @value{GDBN} tells it to execute backwards, and then report the
7402 results back to @value{GDBN}. Whatever the target reports back to
7403 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7404 assumes that the memory and registers that the target reports are in a
7405 consistent state, but @value{GDBN} accepts whatever it is given.
7408 On some platforms, @value{GDBN} has built-in support for reverse
7409 execution, activated with the @code{record} or @code{record btrace}
7410 commands. @xref{Process Record and Replay}. Some remote targets,
7411 typically full system emulators, support reverse execution directly
7412 without requiring any special command.
7414 If you are debugging in a target environment that supports
7415 reverse execution, @value{GDBN} provides the following commands.
7418 @kindex reverse-continue
7419 @kindex rc @r{(@code{reverse-continue})}
7420 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7421 @itemx rc @r{[}@var{ignore-count}@r{]}
7422 Beginning at the point where your program last stopped, start executing
7423 in reverse. Reverse execution will stop for breakpoints and synchronous
7424 exceptions (signals), just like normal execution. Behavior of
7425 asynchronous signals depends on the target environment.
7427 @kindex reverse-step
7428 @kindex rs @r{(@code{step})}
7429 @item reverse-step @r{[}@var{count}@r{]}
7430 Run the program backward until control reaches the start of a
7431 different source line; then stop it, and return control to @value{GDBN}.
7433 Like the @code{step} command, @code{reverse-step} will only stop
7434 at the beginning of a source line. It ``un-executes'' the previously
7435 executed source line. If the previous source line included calls to
7436 debuggable functions, @code{reverse-step} will step (backward) into
7437 the called function, stopping at the beginning of the @emph{last}
7438 statement in the called function (typically a return statement).
7440 Also, as with the @code{step} command, if non-debuggable functions are
7441 called, @code{reverse-step} will run thru them backward without stopping.
7443 @kindex reverse-stepi
7444 @kindex rsi @r{(@code{reverse-stepi})}
7445 @item reverse-stepi @r{[}@var{count}@r{]}
7446 Reverse-execute one machine instruction. Note that the instruction
7447 to be reverse-executed is @emph{not} the one pointed to by the program
7448 counter, but the instruction executed prior to that one. For instance,
7449 if the last instruction was a jump, @code{reverse-stepi} will take you
7450 back from the destination of the jump to the jump instruction itself.
7452 @kindex reverse-next
7453 @kindex rn @r{(@code{reverse-next})}
7454 @item reverse-next @r{[}@var{count}@r{]}
7455 Run backward to the beginning of the previous line executed in
7456 the current (innermost) stack frame. If the line contains function
7457 calls, they will be ``un-executed'' without stopping. Starting from
7458 the first line of a function, @code{reverse-next} will take you back
7459 to the caller of that function, @emph{before} the function was called,
7460 just as the normal @code{next} command would take you from the last
7461 line of a function back to its return to its caller
7462 @footnote{Unless the code is too heavily optimized.}.
7464 @kindex reverse-nexti
7465 @kindex rni @r{(@code{reverse-nexti})}
7466 @item reverse-nexti @r{[}@var{count}@r{]}
7467 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7468 in reverse, except that called functions are ``un-executed'' atomically.
7469 That is, if the previously executed instruction was a return from
7470 another function, @code{reverse-nexti} will continue to execute
7471 in reverse until the call to that function (from the current stack
7474 @kindex reverse-finish
7475 @item reverse-finish
7476 Just as the @code{finish} command takes you to the point where the
7477 current function returns, @code{reverse-finish} takes you to the point
7478 where it was called. Instead of ending up at the end of the current
7479 function invocation, you end up at the beginning.
7481 @kindex set exec-direction
7482 @item set exec-direction
7483 Set the direction of target execution.
7484 @item set exec-direction reverse
7485 @cindex execute forward or backward in time
7486 @value{GDBN} will perform all execution commands in reverse, until the
7487 exec-direction mode is changed to ``forward''. Affected commands include
7488 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7489 command cannot be used in reverse mode.
7490 @item set exec-direction forward
7491 @value{GDBN} will perform all execution commands in the normal fashion.
7492 This is the default.
7496 @node Process Record and Replay
7497 @chapter Recording Inferior's Execution and Replaying It
7498 @cindex process record and replay
7499 @cindex recording inferior's execution and replaying it
7501 On some platforms, @value{GDBN} provides a special @dfn{process record
7502 and replay} target that can record a log of the process execution, and
7503 replay it later with both forward and reverse execution commands.
7506 When this target is in use, if the execution log includes the record
7507 for the next instruction, @value{GDBN} will debug in @dfn{replay
7508 mode}. In the replay mode, the inferior does not really execute code
7509 instructions. Instead, all the events that normally happen during
7510 code execution are taken from the execution log. While code is not
7511 really executed in replay mode, the values of registers (including the
7512 program counter register) and the memory of the inferior are still
7513 changed as they normally would. Their contents are taken from the
7517 If the record for the next instruction is not in the execution log,
7518 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7519 inferior executes normally, and @value{GDBN} records the execution log
7522 The process record and replay target supports reverse execution
7523 (@pxref{Reverse Execution}), even if the platform on which the
7524 inferior runs does not. However, the reverse execution is limited in
7525 this case by the range of the instructions recorded in the execution
7526 log. In other words, reverse execution on platforms that don't
7527 support it directly can only be done in the replay mode.
7529 When debugging in the reverse direction, @value{GDBN} will work in
7530 replay mode as long as the execution log includes the record for the
7531 previous instruction; otherwise, it will work in record mode, if the
7532 platform supports reverse execution, or stop if not.
7534 Currently, process record and replay is supported on ARM, Aarch64,
7535 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7536 GNU/Linux. Process record and replay can be used both when native
7537 debugging, and when remote debugging via @code{gdbserver}.
7539 For architecture environments that support process record and replay,
7540 @value{GDBN} provides the following commands:
7543 @kindex target record
7544 @kindex target record-full
7545 @kindex target record-btrace
7548 @kindex record btrace
7549 @kindex record btrace bts
7550 @kindex record btrace pt
7556 @kindex rec btrace bts
7557 @kindex rec btrace pt
7560 @item record @var{method}
7561 This command starts the process record and replay target. The
7562 recording method can be specified as parameter. Without a parameter
7563 the command uses the @code{full} recording method. The following
7564 recording methods are available:
7568 Full record/replay recording using @value{GDBN}'s software record and
7569 replay implementation. This method allows replaying and reverse
7572 @item btrace @var{format}
7573 Hardware-supported instruction recording, supported on Intel
7574 processors. This method does not record data. Further, the data is
7575 collected in a ring buffer so old data will be overwritten when the
7576 buffer is full. It allows limited reverse execution. Variables and
7577 registers are not available during reverse execution. In remote
7578 debugging, recording continues on disconnect. Recorded data can be
7579 inspected after reconnecting. The recording may be stopped using
7582 The recording format can be specified as parameter. Without a parameter
7583 the command chooses the recording format. The following recording
7584 formats are available:
7588 @cindex branch trace store
7589 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7590 this format, the processor stores a from/to record for each executed
7591 branch in the btrace ring buffer.
7594 @cindex Intel Processor Trace
7595 Use the @dfn{Intel Processor Trace} recording format. In this
7596 format, the processor stores the execution trace in a compressed form
7597 that is afterwards decoded by @value{GDBN}.
7599 The trace can be recorded with very low overhead. The compressed
7600 trace format also allows small trace buffers to already contain a big
7601 number of instructions compared to @acronym{BTS}.
7603 Decoding the recorded execution trace, on the other hand, is more
7604 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7605 increased number of instructions to process. You should increase the
7606 buffer-size with care.
7609 Not all recording formats may be available on all processors.
7612 The process record and replay target can only debug a process that is
7613 already running. Therefore, you need first to start the process with
7614 the @kbd{run} or @kbd{start} commands, and then start the recording
7615 with the @kbd{record @var{method}} command.
7617 @cindex displaced stepping, and process record and replay
7618 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7619 will be automatically disabled when process record and replay target
7620 is started. That's because the process record and replay target
7621 doesn't support displaced stepping.
7623 @cindex non-stop mode, and process record and replay
7624 @cindex asynchronous execution, and process record and replay
7625 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7626 the asynchronous execution mode (@pxref{Background Execution}), not
7627 all recording methods are available. The @code{full} recording method
7628 does not support these two modes.
7633 Stop the process record and replay target. When process record and
7634 replay target stops, the entire execution log will be deleted and the
7635 inferior will either be terminated, or will remain in its final state.
7637 When you stop the process record and replay target in record mode (at
7638 the end of the execution log), the inferior will be stopped at the
7639 next instruction that would have been recorded. In other words, if
7640 you record for a while and then stop recording, the inferior process
7641 will be left in the same state as if the recording never happened.
7643 On the other hand, if the process record and replay target is stopped
7644 while in replay mode (that is, not at the end of the execution log,
7645 but at some earlier point), the inferior process will become ``live''
7646 at that earlier state, and it will then be possible to continue the
7647 usual ``live'' debugging of the process from that state.
7649 When the inferior process exits, or @value{GDBN} detaches from it,
7650 process record and replay target will automatically stop itself.
7654 Go to a specific location in the execution log. There are several
7655 ways to specify the location to go to:
7658 @item record goto begin
7659 @itemx record goto start
7660 Go to the beginning of the execution log.
7662 @item record goto end
7663 Go to the end of the execution log.
7665 @item record goto @var{n}
7666 Go to instruction number @var{n} in the execution log.
7670 @item record save @var{filename}
7671 Save the execution log to a file @file{@var{filename}}.
7672 Default filename is @file{gdb_record.@var{process_id}}, where
7673 @var{process_id} is the process ID of the inferior.
7675 This command may not be available for all recording methods.
7677 @kindex record restore
7678 @item record restore @var{filename}
7679 Restore the execution log from a file @file{@var{filename}}.
7680 File must have been created with @code{record save}.
7682 @kindex set record full
7683 @item set record full insn-number-max @var{limit}
7684 @itemx set record full insn-number-max unlimited
7685 Set the limit of instructions to be recorded for the @code{full}
7686 recording method. Default value is 200000.
7688 If @var{limit} is a positive number, then @value{GDBN} will start
7689 deleting instructions from the log once the number of the record
7690 instructions becomes greater than @var{limit}. For every new recorded
7691 instruction, @value{GDBN} will delete the earliest recorded
7692 instruction to keep the number of recorded instructions at the limit.
7693 (Since deleting recorded instructions loses information, @value{GDBN}
7694 lets you control what happens when the limit is reached, by means of
7695 the @code{stop-at-limit} option, described below.)
7697 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7698 delete recorded instructions from the execution log. The number of
7699 recorded instructions is limited only by the available memory.
7701 @kindex show record full
7702 @item show record full insn-number-max
7703 Show the limit of instructions to be recorded with the @code{full}
7706 @item set record full stop-at-limit
7707 Control the behavior of the @code{full} recording method when the
7708 number of recorded instructions reaches the limit. If ON (the
7709 default), @value{GDBN} will stop when the limit is reached for the
7710 first time and ask you whether you want to stop the inferior or
7711 continue running it and recording the execution log. If you decide
7712 to continue recording, each new recorded instruction will cause the
7713 oldest one to be deleted.
7715 If this option is OFF, @value{GDBN} will automatically delete the
7716 oldest record to make room for each new one, without asking.
7718 @item show record full stop-at-limit
7719 Show the current setting of @code{stop-at-limit}.
7721 @item set record full memory-query
7722 Control the behavior when @value{GDBN} is unable to record memory
7723 changes caused by an instruction for the @code{full} recording method.
7724 If ON, @value{GDBN} will query whether to stop the inferior in that
7727 If this option is OFF (the default), @value{GDBN} will automatically
7728 ignore the effect of such instructions on memory. Later, when
7729 @value{GDBN} replays this execution log, it will mark the log of this
7730 instruction as not accessible, and it will not affect the replay
7733 @item show record full memory-query
7734 Show the current setting of @code{memory-query}.
7736 @kindex set record btrace
7737 The @code{btrace} record target does not trace data. As a
7738 convenience, when replaying, @value{GDBN} reads read-only memory off
7739 the live program directly, assuming that the addresses of the
7740 read-only areas don't change. This for example makes it possible to
7741 disassemble code while replaying, but not to print variables.
7742 In some cases, being able to inspect variables might be useful.
7743 You can use the following command for that:
7745 @item set record btrace replay-memory-access
7746 Control the behavior of the @code{btrace} recording method when
7747 accessing memory during replay. If @code{read-only} (the default),
7748 @value{GDBN} will only allow accesses to read-only memory.
7749 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7750 and to read-write memory. Beware that the accessed memory corresponds
7751 to the live target and not necessarily to the current replay
7754 @item set record btrace cpu @var{identifier}
7755 Set the processor to be used for enabling workarounds for processor
7756 errata when decoding the trace.
7758 Processor errata are defects in processor operation, caused by its
7759 design or manufacture. They can cause a trace not to match the
7760 specification. This, in turn, may cause trace decode to fail.
7761 @value{GDBN} can detect erroneous trace packets and correct them, thus
7762 avoiding the decoding failures. These corrections are known as
7763 @dfn{errata workarounds}, and are enabled based on the processor on
7764 which the trace was recorded.
7766 By default, @value{GDBN} attempts to detect the processor
7767 automatically, and apply the necessary workarounds for it. However,
7768 you may need to specify the processor if @value{GDBN} does not yet
7769 support it. This command allows you to do that, and also allows to
7770 disable the workarounds.
7772 The argument @var{identifier} identifies the @sc{cpu} and is of the
7773 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7774 there are two special identifiers, @code{none} and @code{auto}
7777 The following vendor identifiers and corresponding processor
7778 identifiers are currently supported:
7780 @multitable @columnfractions .1 .9
7783 @tab @var{family}/@var{model}[/@var{stepping}]
7787 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7788 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7790 If @var{identifier} is @code{auto}, enable errata workarounds for the
7791 processor on which the trace was recorded. If @var{identifier} is
7792 @code{none}, errata workarounds are disabled.
7794 For example, when using an old @value{GDBN} on a new system, decode
7795 may fail because @value{GDBN} does not support the new processor. It
7796 often suffices to specify an older processor that @value{GDBN}
7801 Active record target: record-btrace
7802 Recording format: Intel Processor Trace.
7804 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7805 (gdb) set record btrace cpu intel:6/158
7807 Active record target: record-btrace
7808 Recording format: Intel Processor Trace.
7810 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7813 @kindex show record btrace
7814 @item show record btrace replay-memory-access
7815 Show the current setting of @code{replay-memory-access}.
7817 @item show record btrace cpu
7818 Show the processor to be used for enabling trace decode errata
7821 @kindex set record btrace bts
7822 @item set record btrace bts buffer-size @var{size}
7823 @itemx set record btrace bts buffer-size unlimited
7824 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7825 format. Default is 64KB.
7827 If @var{size} is a positive number, then @value{GDBN} will try to
7828 allocate a buffer of at least @var{size} bytes for each new thread
7829 that uses the btrace recording method and the @acronym{BTS} format.
7830 The actually obtained buffer size may differ from the requested
7831 @var{size}. Use the @code{info record} command to see the actual
7832 buffer size for each thread that uses the btrace recording method and
7833 the @acronym{BTS} format.
7835 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7836 allocate a buffer of 4MB.
7838 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7839 also need longer to process the branch trace data before it can be used.
7841 @item show record btrace bts buffer-size @var{size}
7842 Show the current setting of the requested ring buffer size for branch
7843 tracing in @acronym{BTS} format.
7845 @kindex set record btrace pt
7846 @item set record btrace pt buffer-size @var{size}
7847 @itemx set record btrace pt buffer-size unlimited
7848 Set the requested ring buffer size for branch tracing in Intel
7849 Processor Trace format. Default is 16KB.
7851 If @var{size} is a positive number, then @value{GDBN} will try to
7852 allocate a buffer of at least @var{size} bytes for each new thread
7853 that uses the btrace recording method and the Intel Processor Trace
7854 format. The actually obtained buffer size may differ from the
7855 requested @var{size}. Use the @code{info record} command to see the
7856 actual buffer size for each thread.
7858 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7859 allocate a buffer of 4MB.
7861 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7862 also need longer to process the branch trace data before it can be used.
7864 @item show record btrace pt buffer-size @var{size}
7865 Show the current setting of the requested ring buffer size for branch
7866 tracing in Intel Processor Trace format.
7870 Show various statistics about the recording depending on the recording
7875 For the @code{full} recording method, it shows the state of process
7876 record and its in-memory execution log buffer, including:
7880 Whether in record mode or replay mode.
7882 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7884 Highest recorded instruction number.
7886 Current instruction about to be replayed (if in replay mode).
7888 Number of instructions contained in the execution log.
7890 Maximum number of instructions that may be contained in the execution log.
7894 For the @code{btrace} recording method, it shows:
7900 Number of instructions that have been recorded.
7902 Number of blocks of sequential control-flow formed by the recorded
7905 Whether in record mode or replay mode.
7908 For the @code{bts} recording format, it also shows:
7911 Size of the perf ring buffer.
7914 For the @code{pt} recording format, it also shows:
7917 Size of the perf ring buffer.
7921 @kindex record delete
7924 When record target runs in replay mode (``in the past''), delete the
7925 subsequent execution log and begin to record a new execution log starting
7926 from the current address. This means you will abandon the previously
7927 recorded ``future'' and begin recording a new ``future''.
7929 @kindex record instruction-history
7930 @kindex rec instruction-history
7931 @item record instruction-history
7932 Disassembles instructions from the recorded execution log. By
7933 default, ten instructions are disassembled. This can be changed using
7934 the @code{set record instruction-history-size} command. Instructions
7935 are printed in execution order.
7937 It can also print mixed source+disassembly if you specify the the
7938 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7939 as well as in symbolic form by specifying the @code{/r} modifier.
7941 The current position marker is printed for the instruction at the
7942 current program counter value. This instruction can appear multiple
7943 times in the trace and the current position marker will be printed
7944 every time. To omit the current position marker, specify the
7947 To better align the printed instructions when the trace contains
7948 instructions from more than one function, the function name may be
7949 omitted by specifying the @code{/f} modifier.
7951 Speculatively executed instructions are prefixed with @samp{?}. This
7952 feature is not available for all recording formats.
7954 There are several ways to specify what part of the execution log to
7958 @item record instruction-history @var{insn}
7959 Disassembles ten instructions starting from instruction number
7962 @item record instruction-history @var{insn}, +/-@var{n}
7963 Disassembles @var{n} instructions around instruction number
7964 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7965 @var{n} instructions after instruction number @var{insn}. If
7966 @var{n} is preceded with @code{-}, disassembles @var{n}
7967 instructions before instruction number @var{insn}.
7969 @item record instruction-history
7970 Disassembles ten more instructions after the last disassembly.
7972 @item record instruction-history -
7973 Disassembles ten more instructions before the last disassembly.
7975 @item record instruction-history @var{begin}, @var{end}
7976 Disassembles instructions beginning with instruction number
7977 @var{begin} until instruction number @var{end}. The instruction
7978 number @var{end} is included.
7981 This command may not be available for all recording methods.
7984 @item set record instruction-history-size @var{size}
7985 @itemx set record instruction-history-size unlimited
7986 Define how many instructions to disassemble in the @code{record
7987 instruction-history} command. The default value is 10.
7988 A @var{size} of @code{unlimited} means unlimited instructions.
7991 @item show record instruction-history-size
7992 Show how many instructions to disassemble in the @code{record
7993 instruction-history} command.
7995 @kindex record function-call-history
7996 @kindex rec function-call-history
7997 @item record function-call-history
7998 Prints the execution history at function granularity. For each sequence
7999 of instructions that belong to the same function, it prints the name of
8000 that function, the source lines for this instruction sequence (if the
8001 @code{/l} modifier is specified), and the instructions numbers that form
8002 the sequence (if the @code{/i} modifier is specified). The function names
8003 are indented to reflect the call stack depth if the @code{/c} modifier is
8004 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
8008 (@value{GDBP}) @b{list 1, 10}
8019 (@value{GDBP}) @b{record function-call-history /ilc}
8020 1 bar inst 1,4 at foo.c:6,8
8021 2 foo inst 5,10 at foo.c:2,3
8022 3 bar inst 11,13 at foo.c:9,10
8025 By default, ten functions are printed. This can be changed using the
8026 @code{set record function-call-history-size} command. Functions are
8027 printed in execution order. There are several ways to specify what
8031 @item record function-call-history @var{func}
8032 Prints ten functions starting from function number @var{func}.
8034 @item record function-call-history @var{func}, +/-@var{n}
8035 Prints @var{n} functions around function number @var{func}. If
8036 @var{n} is preceded with @code{+}, prints @var{n} functions after
8037 function number @var{func}. If @var{n} is preceded with @code{-},
8038 prints @var{n} functions before function number @var{func}.
8040 @item record function-call-history
8041 Prints ten more functions after the last ten-function print.
8043 @item record function-call-history -
8044 Prints ten more functions before the last ten-function print.
8046 @item record function-call-history @var{begin}, @var{end}
8047 Prints functions beginning with function number @var{begin} until
8048 function number @var{end}. The function number @var{end} is included.
8051 This command may not be available for all recording methods.
8053 @item set record function-call-history-size @var{size}
8054 @itemx set record function-call-history-size unlimited
8055 Define how many functions to print in the
8056 @code{record function-call-history} command. The default value is 10.
8057 A size of @code{unlimited} means unlimited functions.
8059 @item show record function-call-history-size
8060 Show how many functions to print in the
8061 @code{record function-call-history} command.
8066 @chapter Examining the Stack
8068 When your program has stopped, the first thing you need to know is where it
8069 stopped and how it got there.
8072 Each time your program performs a function call, information about the call
8074 That information includes the location of the call in your program,
8075 the arguments of the call,
8076 and the local variables of the function being called.
8077 The information is saved in a block of data called a @dfn{stack frame}.
8078 The stack frames are allocated in a region of memory called the @dfn{call
8081 When your program stops, the @value{GDBN} commands for examining the
8082 stack allow you to see all of this information.
8084 @cindex selected frame
8085 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8086 @value{GDBN} commands refer implicitly to the selected frame. In
8087 particular, whenever you ask @value{GDBN} for the value of a variable in
8088 your program, the value is found in the selected frame. There are
8089 special @value{GDBN} commands to select whichever frame you are
8090 interested in. @xref{Selection, ,Selecting a Frame}.
8092 When your program stops, @value{GDBN} automatically selects the
8093 currently executing frame and describes it briefly, similar to the
8094 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8097 * Frames:: Stack frames
8098 * Backtrace:: Backtraces
8099 * Selection:: Selecting a frame
8100 * Frame Info:: Information on a frame
8101 * Frame Apply:: Applying a command to several frames
8102 * Frame Filter Management:: Managing frame filters
8107 @section Stack Frames
8109 @cindex frame, definition
8111 The call stack is divided up into contiguous pieces called @dfn{stack
8112 frames}, or @dfn{frames} for short; each frame is the data associated
8113 with one call to one function. The frame contains the arguments given
8114 to the function, the function's local variables, and the address at
8115 which the function is executing.
8117 @cindex initial frame
8118 @cindex outermost frame
8119 @cindex innermost frame
8120 When your program is started, the stack has only one frame, that of the
8121 function @code{main}. This is called the @dfn{initial} frame or the
8122 @dfn{outermost} frame. Each time a function is called, a new frame is
8123 made. Each time a function returns, the frame for that function invocation
8124 is eliminated. If a function is recursive, there can be many frames for
8125 the same function. The frame for the function in which execution is
8126 actually occurring is called the @dfn{innermost} frame. This is the most
8127 recently created of all the stack frames that still exist.
8129 @cindex frame pointer
8130 Inside your program, stack frames are identified by their addresses. A
8131 stack frame consists of many bytes, each of which has its own address; each
8132 kind of computer has a convention for choosing one byte whose
8133 address serves as the address of the frame. Usually this address is kept
8134 in a register called the @dfn{frame pointer register}
8135 (@pxref{Registers, $fp}) while execution is going on in that frame.
8138 @cindex frame number
8139 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8140 number that is zero for the innermost frame, one for the frame that
8141 called it, and so on upward. These level numbers give you a way of
8142 designating stack frames in @value{GDBN} commands. The terms
8143 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8144 describe this number.
8146 @c The -fomit-frame-pointer below perennially causes hbox overflow
8147 @c underflow problems.
8148 @cindex frameless execution
8149 Some compilers provide a way to compile functions so that they operate
8150 without stack frames. (For example, the @value{NGCC} option
8152 @samp{-fomit-frame-pointer}
8154 generates functions without a frame.)
8155 This is occasionally done with heavily used library functions to save
8156 the frame setup time. @value{GDBN} has limited facilities for dealing
8157 with these function invocations. If the innermost function invocation
8158 has no stack frame, @value{GDBN} nevertheless regards it as though
8159 it had a separate frame, which is numbered zero as usual, allowing
8160 correct tracing of the function call chain. However, @value{GDBN} has
8161 no provision for frameless functions elsewhere in the stack.
8167 @cindex call stack traces
8168 A backtrace is a summary of how your program got where it is. It shows one
8169 line per frame, for many frames, starting with the currently executing
8170 frame (frame zero), followed by its caller (frame one), and on up the
8173 @anchor{backtrace-command}
8175 @kindex bt @r{(@code{backtrace})}
8176 To print a backtrace of the entire stack, use the @code{backtrace}
8177 command, or its alias @code{bt}. This command will print one line per
8178 frame for frames in the stack. By default, all stack frames are
8179 printed. You can stop the backtrace at any time by typing the system
8180 interrupt character, normally @kbd{Ctrl-c}.
8183 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8184 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8185 Print the backtrace of the entire stack.
8187 The optional @var{count} can be one of the following:
8192 Print only the innermost @var{n} frames, where @var{n} is a positive
8197 Print only the outermost @var{n} frames, where @var{n} is a positive
8205 Print the values of the local variables also. This can be combined
8206 with the optional @var{count} to limit the number of frames shown.
8209 Do not run Python frame filters on this backtrace. @xref{Frame
8210 Filter API}, for more information. Additionally use @ref{disable
8211 frame-filter all} to turn off all frame filters. This is only
8212 relevant when @value{GDBN} has been configured with @code{Python}
8216 A Python frame filter might decide to ``elide'' some frames. Normally
8217 such elided frames are still printed, but they are indented relative
8218 to the filtered frames that cause them to be elided. The @code{-hide}
8219 option causes elided frames to not be printed at all.
8222 The @code{backtrace} command also supports a number of options that
8223 allow overriding relevant global print settings as set by @code{set
8224 backtrace} and @code{set print} subcommands:
8227 @item -past-main [@code{on}|@code{off}]
8228 Set whether backtraces should continue past @code{main}. Related setting:
8229 @ref{set backtrace past-main}.
8231 @item -past-entry [@code{on}|@code{off}]
8232 Set whether backtraces should continue past the entry point of a program.
8233 Related setting: @ref{set backtrace past-entry}.
8235 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8236 Set printing of function arguments at function entry.
8237 Related setting: @ref{set print entry-values}.
8239 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8240 Set printing of non-scalar frame arguments.
8241 Related setting: @ref{set print frame-arguments}.
8243 @item -raw-frame-arguments [@code{on}|@code{off}]
8244 Set whether to print frame arguments in raw form.
8245 Related setting: @ref{set print raw-frame-arguments}.
8247 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8248 Set printing of frame information.
8249 Related setting: @ref{set print frame-info}.
8252 The optional @var{qualifier} is maintained for backward compatibility.
8253 It can be one of the following:
8257 Equivalent to the @code{-full} option.
8260 Equivalent to the @code{-no-filters} option.
8263 Equivalent to the @code{-hide} option.
8270 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8271 are additional aliases for @code{backtrace}.
8273 @cindex multiple threads, backtrace
8274 In a multi-threaded program, @value{GDBN} by default shows the
8275 backtrace only for the current thread. To display the backtrace for
8276 several or all of the threads, use the command @code{thread apply}
8277 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8278 apply all backtrace}, @value{GDBN} will display the backtrace for all
8279 the threads; this is handy when you debug a core dump of a
8280 multi-threaded program.
8282 Each line in the backtrace shows the frame number and the function name.
8283 The program counter value is also shown---unless you use @code{set
8284 print address off}. The backtrace also shows the source file name and
8285 line number, as well as the arguments to the function. The program
8286 counter value is omitted if it is at the beginning of the code for that
8289 Here is an example of a backtrace. It was made with the command
8290 @samp{bt 3}, so it shows the innermost three frames.
8294 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8296 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8297 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8299 (More stack frames follow...)
8304 The display for frame zero does not begin with a program counter
8305 value, indicating that your program has stopped at the beginning of the
8306 code for line @code{993} of @code{builtin.c}.
8309 The value of parameter @code{data} in frame 1 has been replaced by
8310 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8311 only if it is a scalar (integer, pointer, enumeration, etc). See command
8312 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8313 on how to configure the way function parameter values are printed.
8314 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8315 what frame information is printed.
8317 @cindex optimized out, in backtrace
8318 @cindex function call arguments, optimized out
8319 If your program was compiled with optimizations, some compilers will
8320 optimize away arguments passed to functions if those arguments are
8321 never used after the call. Such optimizations generate code that
8322 passes arguments through registers, but doesn't store those arguments
8323 in the stack frame. @value{GDBN} has no way of displaying such
8324 arguments in stack frames other than the innermost one. Here's what
8325 such a backtrace might look like:
8329 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8331 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8332 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8334 (More stack frames follow...)
8339 The values of arguments that were not saved in their stack frames are
8340 shown as @samp{<optimized out>}.
8342 If you need to display the values of such optimized-out arguments,
8343 either deduce that from other variables whose values depend on the one
8344 you are interested in, or recompile without optimizations.
8346 @cindex backtrace beyond @code{main} function
8347 @cindex program entry point
8348 @cindex startup code, and backtrace
8349 Most programs have a standard user entry point---a place where system
8350 libraries and startup code transition into user code. For C this is
8351 @code{main}@footnote{
8352 Note that embedded programs (the so-called ``free-standing''
8353 environment) are not required to have a @code{main} function as the
8354 entry point. They could even have multiple entry points.}.
8355 When @value{GDBN} finds the entry function in a backtrace
8356 it will terminate the backtrace, to avoid tracing into highly
8357 system-specific (and generally uninteresting) code.
8359 If you need to examine the startup code, or limit the number of levels
8360 in a backtrace, you can change this behavior:
8363 @item set backtrace past-main
8364 @itemx set backtrace past-main on
8365 @anchor{set backtrace past-main}
8366 @kindex set backtrace
8367 Backtraces will continue past the user entry point.
8369 @item set backtrace past-main off
8370 Backtraces will stop when they encounter the user entry point. This is the
8373 @item show backtrace past-main
8374 @kindex show backtrace
8375 Display the current user entry point backtrace policy.
8377 @item set backtrace past-entry
8378 @itemx set backtrace past-entry on
8379 @anchor{set backtrace past-entry}
8380 Backtraces will continue past the internal entry point of an application.
8381 This entry point is encoded by the linker when the application is built,
8382 and is likely before the user entry point @code{main} (or equivalent) is called.
8384 @item set backtrace past-entry off
8385 Backtraces will stop when they encounter the internal entry point of an
8386 application. This is the default.
8388 @item show backtrace past-entry
8389 Display the current internal entry point backtrace policy.
8391 @item set backtrace limit @var{n}
8392 @itemx set backtrace limit 0
8393 @itemx set backtrace limit unlimited
8394 @anchor{set backtrace limit}
8395 @cindex backtrace limit
8396 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8397 or zero means unlimited levels.
8399 @item show backtrace limit
8400 Display the current limit on backtrace levels.
8403 You can control how file names are displayed.
8406 @item set filename-display
8407 @itemx set filename-display relative
8408 @cindex filename-display
8409 Display file names relative to the compilation directory. This is the default.
8411 @item set filename-display basename
8412 Display only basename of a filename.
8414 @item set filename-display absolute
8415 Display an absolute filename.
8417 @item show filename-display
8418 Show the current way to display filenames.
8422 @section Selecting a Frame
8424 Most commands for examining the stack and other data in your program work on
8425 whichever stack frame is selected at the moment. Here are the commands for
8426 selecting a stack frame; all of them finish by printing a brief description
8427 of the stack frame just selected.
8430 @kindex frame@r{, selecting}
8431 @kindex f @r{(@code{frame})}
8432 @item frame @r{[} @var{frame-selection-spec} @r{]}
8433 @item f @r{[} @var{frame-selection-spec} @r{]}
8434 The @command{frame} command allows different stack frames to be
8435 selected. The @var{frame-selection-spec} can be any of the following:
8440 @item level @var{num}
8441 Select frame level @var{num}. Recall that frame zero is the innermost
8442 (currently executing) frame, frame one is the frame that called the
8443 innermost one, and so on. The highest level frame is usually the one
8446 As this is the most common method of navigating the frame stack, the
8447 string @command{level} can be omitted. For example, the following two
8448 commands are equivalent:
8451 (@value{GDBP}) frame 3
8452 (@value{GDBP}) frame level 3
8455 @kindex frame address
8456 @item address @var{stack-address}
8457 Select the frame with stack address @var{stack-address}. The
8458 @var{stack-address} for a frame can be seen in the output of
8459 @command{info frame}, for example:
8463 Stack level 1, frame at 0x7fffffffda30:
8464 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8465 tail call frame, caller of frame at 0x7fffffffda30
8466 source language c++.
8467 Arglist at unknown address.
8468 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8471 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8472 indicated by the line:
8475 Stack level 1, frame at 0x7fffffffda30:
8478 @kindex frame function
8479 @item function @var{function-name}
8480 Select the stack frame for function @var{function-name}. If there are
8481 multiple stack frames for function @var{function-name} then the inner
8482 most stack frame is selected.
8485 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8486 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8487 viewed has stack address @var{stack-addr}, and optionally, a program
8488 counter address of @var{pc-addr}.
8490 This is useful mainly if the chaining of stack frames has been
8491 damaged by a bug, making it impossible for @value{GDBN} to assign
8492 numbers properly to all frames. In addition, this can be useful
8493 when your program has multiple stacks and switches between them.
8495 When viewing a frame outside the current backtrace using
8496 @command{frame view} then you can always return to the original
8497 stack using one of the previous stack frame selection instructions,
8498 for example @command{frame level 0}.
8504 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8505 numbers @var{n}, this advances toward the outermost frame, to higher
8506 frame numbers, to frames that have existed longer.
8509 @kindex do @r{(@code{down})}
8511 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8512 positive numbers @var{n}, this advances toward the innermost frame, to
8513 lower frame numbers, to frames that were created more recently.
8514 You may abbreviate @code{down} as @code{do}.
8517 All of these commands end by printing two lines of output describing the
8518 frame. The first line shows the frame number, the function name, the
8519 arguments, and the source file and line number of execution in that
8520 frame. The second line shows the text of that source line.
8528 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8530 10 read_input_file (argv[i]);
8534 After such a printout, the @code{list} command with no arguments
8535 prints ten lines centered on the point of execution in the frame.
8536 You can also edit the program at the point of execution with your favorite
8537 editing program by typing @code{edit}.
8538 @xref{List, ,Printing Source Lines},
8542 @kindex select-frame
8543 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8544 The @code{select-frame} command is a variant of @code{frame} that does
8545 not display the new frame after selecting it. This command is
8546 intended primarily for use in @value{GDBN} command scripts, where the
8547 output might be unnecessary and distracting. The
8548 @var{frame-selection-spec} is as for the @command{frame} command
8549 described in @ref{Selection, ,Selecting a Frame}.
8551 @kindex down-silently
8553 @item up-silently @var{n}
8554 @itemx down-silently @var{n}
8555 These two commands are variants of @code{up} and @code{down},
8556 respectively; they differ in that they do their work silently, without
8557 causing display of the new frame. They are intended primarily for use
8558 in @value{GDBN} command scripts, where the output might be unnecessary and
8563 @section Information About a Frame
8565 There are several other commands to print information about the selected
8571 When used without any argument, this command does not change which
8572 frame is selected, but prints a brief description of the currently
8573 selected stack frame. It can be abbreviated @code{f}. With an
8574 argument, this command is used to select a stack frame.
8575 @xref{Selection, ,Selecting a Frame}.
8578 @kindex info f @r{(@code{info frame})}
8581 This command prints a verbose description of the selected stack frame,
8586 the address of the frame
8588 the address of the next frame down (called by this frame)
8590 the address of the next frame up (caller of this frame)
8592 the language in which the source code corresponding to this frame is written
8594 the address of the frame's arguments
8596 the address of the frame's local variables
8598 the program counter saved in it (the address of execution in the caller frame)
8600 which registers were saved in the frame
8603 @noindent The verbose description is useful when
8604 something has gone wrong that has made the stack format fail to fit
8605 the usual conventions.
8607 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8608 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8609 Print a verbose description of the frame selected by
8610 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8611 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8612 a Frame}). The selected frame remains unchanged by this command.
8615 @item info args [-q]
8616 Print the arguments of the selected frame, each on a separate line.
8618 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8619 printing header information and messages explaining why no argument
8622 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8623 Like @kbd{info args}, but only print the arguments selected
8624 with the provided regexp(s).
8626 If @var{regexp} is provided, print only the arguments whose names
8627 match the regular expression @var{regexp}.
8629 If @var{type_regexp} is provided, print only the arguments whose
8630 types, as printed by the @code{whatis} command, match
8631 the regular expression @var{type_regexp}.
8632 If @var{type_regexp} contains space(s), it should be enclosed in
8633 quote characters. If needed, use backslash to escape the meaning
8634 of special characters or quotes.
8636 If both @var{regexp} and @var{type_regexp} are provided, an argument
8637 is printed only if its name matches @var{regexp} and its type matches
8640 @item info locals [-q]
8642 Print the local variables of the selected frame, each on a separate
8643 line. These are all variables (declared either static or automatic)
8644 accessible at the point of execution of the selected frame.
8646 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8647 printing header information and messages explaining why no local variables
8650 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8651 Like @kbd{info locals}, but only print the local variables selected
8652 with the provided regexp(s).
8654 If @var{regexp} is provided, print only the local variables whose names
8655 match the regular expression @var{regexp}.
8657 If @var{type_regexp} is provided, print only the local variables whose
8658 types, as printed by the @code{whatis} command, match
8659 the regular expression @var{type_regexp}.
8660 If @var{type_regexp} contains space(s), it should be enclosed in
8661 quote characters. If needed, use backslash to escape the meaning
8662 of special characters or quotes.
8664 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8665 is printed only if its name matches @var{regexp} and its type matches
8668 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8669 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8670 For example, your program might use Resource Acquisition Is
8671 Initialization types (RAII) such as @code{lock_something_t}: each
8672 local variable of type @code{lock_something_t} automatically places a
8673 lock that is destroyed when the variable goes out of scope. You can
8674 then list all acquired locks in your program by doing
8676 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8679 or the equivalent shorter form
8681 tfaas i lo -q -t lock_something_t
8687 @section Applying a Command to Several Frames.
8689 @cindex apply command to several frames
8691 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8692 The @code{frame apply} command allows you to apply the named
8693 @var{command} to one or more frames.
8697 Specify @code{all} to apply @var{command} to all frames.
8700 Use @var{count} to apply @var{command} to the innermost @var{count}
8701 frames, where @var{count} is a positive number.
8704 Use @var{-count} to apply @var{command} to the outermost @var{count}
8705 frames, where @var{count} is a positive number.
8708 Use @code{level} to apply @var{command} to the set of frames identified
8709 by the @var{level} list. @var{level} is a frame level or a range of frame
8710 levels as @var{level1}-@var{level2}. The frame level is the number shown
8711 in the first field of the @samp{backtrace} command output.
8712 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8713 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8717 Note that the frames on which @code{frame apply} applies a command are
8718 also influenced by the @code{set backtrace} settings such as @code{set
8719 backtrace past-main} and @code{set backtrace limit N}.
8720 @xref{Backtrace,,Backtraces}.
8722 The @code{frame apply} command also supports a number of options that
8723 allow overriding relevant @code{set backtrace} settings:
8726 @item -past-main [@code{on}|@code{off}]
8727 Whether backtraces should continue past @code{main}.
8728 Related setting: @ref{set backtrace past-main}.
8730 @item -past-entry [@code{on}|@code{off}]
8731 Whether backtraces should continue past the entry point of a program.
8732 Related setting: @ref{set backtrace past-entry}.
8735 By default, @value{GDBN} displays some frame information before the
8736 output produced by @var{command}, and an error raised during the
8737 execution of a @var{command} will abort @code{frame apply}. The
8738 following options can be used to fine-tune these behaviors:
8742 The flag @code{-c}, which stands for @samp{continue}, causes any
8743 errors in @var{command} to be displayed, and the execution of
8744 @code{frame apply} then continues.
8746 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8747 or empty output produced by a @var{command} to be silently ignored.
8748 That is, the execution continues, but the frame information and errors
8751 The flag @code{-q} (@samp{quiet}) disables printing the frame
8755 The following example shows how the flags @code{-c} and @code{-s} are
8756 working when applying the command @code{p j} to all frames, where
8757 variable @code{j} can only be successfully printed in the outermost
8758 @code{#1 main} frame.
8762 (gdb) frame apply all p j
8763 #0 some_function (i=5) at fun.c:4
8764 No symbol "j" in current context.
8765 (gdb) frame apply all -c p j
8766 #0 some_function (i=5) at fun.c:4
8767 No symbol "j" in current context.
8768 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8770 (gdb) frame apply all -s p j
8771 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8777 By default, @samp{frame apply}, prints the frame location
8778 information before the command output:
8782 (gdb) frame apply all p $sp
8783 #0 some_function (i=5) at fun.c:4
8784 $4 = (void *) 0xffffd1e0
8785 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8786 $5 = (void *) 0xffffd1f0
8791 If the flag @code{-q} is given, no frame information is printed:
8794 (gdb) frame apply all -q p $sp
8795 $12 = (void *) 0xffffd1e0
8796 $13 = (void *) 0xffffd1f0
8806 @cindex apply a command to all frames (ignoring errors and empty output)
8807 @item faas @var{command}
8808 Shortcut for @code{frame apply all -s @var{command}}.
8809 Applies @var{command} on all frames, ignoring errors and empty output.
8811 It can for example be used to print a local variable or a function
8812 argument without knowing the frame where this variable or argument
8815 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8818 The @code{faas} command accepts the same options as the @code{frame
8819 apply} command. @xref{Frame Apply,,frame apply}.
8821 Note that the command @code{tfaas @var{command}} applies @var{command}
8822 on all frames of all threads. See @xref{Threads,,Threads}.
8826 @node Frame Filter Management
8827 @section Management of Frame Filters.
8828 @cindex managing frame filters
8830 Frame filters are Python based utilities to manage and decorate the
8831 output of frames. @xref{Frame Filter API}, for further information.
8833 Managing frame filters is performed by several commands available
8834 within @value{GDBN}, detailed here.
8837 @kindex info frame-filter
8838 @item info frame-filter
8839 Print a list of installed frame filters from all dictionaries, showing
8840 their name, priority and enabled status.
8842 @kindex disable frame-filter
8843 @anchor{disable frame-filter all}
8844 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8845 Disable a frame filter in the dictionary matching
8846 @var{filter-dictionary} and @var{filter-name}. The
8847 @var{filter-dictionary} may be @code{all}, @code{global},
8848 @code{progspace}, or the name of the object file where the frame filter
8849 dictionary resides. When @code{all} is specified, all frame filters
8850 across all dictionaries are disabled. The @var{filter-name} is the name
8851 of the frame filter and is used when @code{all} is not the option for
8852 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8853 may be enabled again later.
8855 @kindex enable frame-filter
8856 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8857 Enable a frame filter in the dictionary matching
8858 @var{filter-dictionary} and @var{filter-name}. The
8859 @var{filter-dictionary} may be @code{all}, @code{global},
8860 @code{progspace} or the name of the object file where the frame filter
8861 dictionary resides. When @code{all} is specified, all frame filters across
8862 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8863 filter and is used when @code{all} is not the option for
8864 @var{filter-dictionary}.
8869 (gdb) info frame-filter
8871 global frame-filters:
8872 Priority Enabled Name
8873 1000 No PrimaryFunctionFilter
8876 progspace /build/test frame-filters:
8877 Priority Enabled Name
8878 100 Yes ProgspaceFilter
8880 objfile /build/test frame-filters:
8881 Priority Enabled Name
8882 999 Yes BuildProgramFilter
8884 (gdb) disable frame-filter /build/test BuildProgramFilter
8885 (gdb) info frame-filter
8887 global frame-filters:
8888 Priority Enabled Name
8889 1000 No PrimaryFunctionFilter
8892 progspace /build/test frame-filters:
8893 Priority Enabled Name
8894 100 Yes ProgspaceFilter
8896 objfile /build/test frame-filters:
8897 Priority Enabled Name
8898 999 No BuildProgramFilter
8900 (gdb) enable frame-filter global PrimaryFunctionFilter
8901 (gdb) info frame-filter
8903 global frame-filters:
8904 Priority Enabled Name
8905 1000 Yes PrimaryFunctionFilter
8908 progspace /build/test frame-filters:
8909 Priority Enabled Name
8910 100 Yes ProgspaceFilter
8912 objfile /build/test frame-filters:
8913 Priority Enabled Name
8914 999 No BuildProgramFilter
8917 @kindex set frame-filter priority
8918 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8919 Set the @var{priority} of a frame filter in the dictionary matching
8920 @var{filter-dictionary}, and the frame filter name matching
8921 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8922 @code{progspace} or the name of the object file where the frame filter
8923 dictionary resides. The @var{priority} is an integer.
8925 @kindex show frame-filter priority
8926 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8927 Show the @var{priority} of a frame filter in the dictionary matching
8928 @var{filter-dictionary}, and the frame filter name matching
8929 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8930 @code{progspace} or the name of the object file where the frame filter
8936 (gdb) info frame-filter
8938 global frame-filters:
8939 Priority Enabled Name
8940 1000 Yes PrimaryFunctionFilter
8943 progspace /build/test frame-filters:
8944 Priority Enabled Name
8945 100 Yes ProgspaceFilter
8947 objfile /build/test frame-filters:
8948 Priority Enabled Name
8949 999 No BuildProgramFilter
8951 (gdb) set frame-filter priority global Reverse 50
8952 (gdb) info frame-filter
8954 global frame-filters:
8955 Priority Enabled Name
8956 1000 Yes PrimaryFunctionFilter
8959 progspace /build/test frame-filters:
8960 Priority Enabled Name
8961 100 Yes ProgspaceFilter
8963 objfile /build/test frame-filters:
8964 Priority Enabled Name
8965 999 No BuildProgramFilter
8970 @chapter Examining Source Files
8972 @value{GDBN} can print parts of your program's source, since the debugging
8973 information recorded in the program tells @value{GDBN} what source files were
8974 used to build it. When your program stops, @value{GDBN} spontaneously prints
8975 the line where it stopped. Likewise, when you select a stack frame
8976 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8977 execution in that frame has stopped. You can print other portions of
8978 source files by explicit command.
8980 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8981 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8982 @value{GDBN} under @sc{gnu} Emacs}.
8985 * List:: Printing source lines
8986 * Location Specifications:: How to specify code locations
8987 * Edit:: Editing source files
8988 * Search:: Searching source files
8989 * Source Path:: Specifying source directories
8990 * Machine Code:: Source and machine code
8991 * Disable Reading Source:: Disable Reading Source Code
8995 @section Printing Source Lines
8998 @kindex l @r{(@code{list})}
8999 To print lines from a source file, use the @code{list} command
9000 (abbreviated @code{l}). By default, ten lines are printed.
9001 There are several ways to specify what part of the file you want to
9002 print; see @ref{Location Specifications}, for the full list.
9004 Here are the forms of the @code{list} command most commonly used:
9007 @item list @var{linenum}
9008 Print lines centered around line number @var{linenum} in the
9009 current source file.
9011 @item list @var{function}
9012 Print lines centered around the beginning of function
9016 Print more lines. If the last lines printed were printed with a
9017 @code{list} command, this prints lines following the last lines
9018 printed; however, if the last line printed was a solitary line printed
9019 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9020 Stack}), this prints lines centered around that line.
9023 Print lines just before the lines last printed.
9026 @cindex @code{list}, how many lines to display
9027 By default, @value{GDBN} prints ten source lines with any of these forms of
9028 the @code{list} command. You can change this using @code{set listsize}:
9031 @kindex set listsize
9032 @item set listsize @var{count}
9033 @itemx set listsize unlimited
9034 Make the @code{list} command display @var{count} source lines (unless
9035 the @code{list} argument explicitly specifies some other number).
9036 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9038 @kindex show listsize
9040 Display the number of lines that @code{list} prints.
9043 Repeating a @code{list} command with @key{RET} discards the argument,
9044 so it is equivalent to typing just @code{list}. This is more useful
9045 than listing the same lines again. An exception is made for an
9046 argument of @samp{-}; that argument is preserved in repetition so that
9047 each repetition moves up in the source file.
9049 In general, the @code{list} command expects you to supply zero, one or
9050 two location specs. These location specs are interpreted to resolve
9051 to source code lines; there are several ways of writing them
9052 (@pxref{Location Specifications}), but the effect is always to resolve
9053 to some source lines to display.
9055 Here is a complete description of the possible arguments for @code{list}:
9058 @item list @var{locspec}
9059 Print lines centered around the line or lines of all the code
9060 locations that result from resolving @var{locspec}.
9062 @item list @var{first},@var{last}
9063 Print lines from @var{first} to @var{last}. Both arguments are
9064 location specs. When a @code{list} command has two location specs,
9065 and the source file of the second location spec is omitted, this
9066 refers to the same source file as the first location spec. If either
9067 @var{first} or @var{last} resolve to more than one source line in the
9068 program, then the list command shows the list of resolved source
9069 lines and does not proceed with the source code listing.
9071 @item list ,@var{last}
9072 Print lines ending with @var{last}.
9074 Likewise, if @var{last} resolves to more than one source line in the
9075 program, then the list command prints the list of resolved source
9076 lines and does not proceed with the source code listing.
9078 @item list @var{first},
9079 Print lines starting with @var{first}.
9082 Print lines just after the lines last printed.
9085 Print lines just before the lines last printed.
9088 As described in the preceding table.
9091 @node Location Specifications
9092 @section Location Specifications
9093 @cindex specifying location
9095 @cindex source location
9096 @cindex code location
9098 @cindex location spec
9099 Several @value{GDBN} commands accept arguments that specify a location
9100 or locations of your program's code. Many times locations are
9101 specified using a source line number, but they can also be specified
9102 by a function name, an address, a label, etc. The different
9103 forms of specifying a location that @value{GDBN} recognizes are
9104 collectively known as forms of @dfn{location specification}, or
9105 @dfn{location spec}. This section documents the forms of specifying
9106 locations that @value{GDBN} recognizes.
9108 @cindex location resolution
9109 @cindex resolution of location spec
9110 When you specify a location, @value{GDBN} needs to find the place in
9111 your program, known as @dfn{code location}, that corresponds to the
9112 given location spec. We call this process of finding actual code
9113 locations corresponding to a location spec @dfn{location resolution}.
9115 A concrete code location in your program is uniquely identifiable by a
9116 set of several attributes: its source line number, the name of its
9117 source file, the fully-qualified and prototyped function in which it
9118 is defined, and an instruction address. Because each inferior has its
9119 own address space, the inferior number is also a necessary part of
9122 By contrast, location specs you type will many times omit some of
9123 these attributes. For example, it is customary to specify just the
9124 source line number to mean a line in the current source file, or
9125 specify just the basename of the file, omitting its directories. In
9126 other words, a location spec is usually incomplete, a kind of
9127 blueprint, and @value{GDBN} needs to complete the missing attributes
9128 by using the implied defaults, and by considering the source code and
9129 the debug information available to it. This is what location
9130 resolution is about.
9132 The resolution of an incomplete location spec can produce more than a
9133 single code location, if the spec doesn't allow distinguishing between
9134 them. Here are some examples of situations that result in a location
9135 spec matching multiple code locations in your program:
9139 The location spec specifies a function name, and there are several
9140 functions in the program which have that name. (To distinguish
9141 between them, you can specify a fully-qualified and prototyped
9142 function name, such as @code{A::func(int)} instead of just
9146 The location spec specifies a source file name, and there are several
9147 source files in the program that share the same name, for example
9148 several files with the same basename in different subdirectories. (To
9149 distinguish between them, specify enough leading directories with the
9153 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9154 instances of the function body, used in different cases, but their
9155 source-level names are identical.
9158 For a C@t{++} template function, a given line in the function can
9159 correspond to any number of instantiations.
9162 For an inlined function, a given source line can correspond to several
9163 actual code locations with that function's inlined code.
9166 Resolution of a location spec can also fail to produce a complete code
9167 location, or even fail to produce any code location. Here are some
9168 examples of such situations:
9172 Some parts of the program lack detailed enough debug info, so the
9173 resolved code location lacks some attributes, like source file name
9174 and line number, leaving just the instruction address and perhaps also
9175 a function name. Such an incomplete code location is only usable in
9176 contexts that work with addresses and/or function names. Some
9177 commands can only work with complete code locations.
9180 The location spec specifies a function name, and there are no
9181 functions in the program by that name, or they only exist in a
9182 yet-unloaded shared library.
9185 The location spec specifies a source file name, and there are no
9186 source files in the program by that name, or they only exist in a
9187 yet-unloaded shared library.
9190 The location spec specifies both a source file name and a source line
9191 number, and even though there are source files in the program that
9192 match the file name, none of those files has the specified line
9196 Locations may be specified using three different formats: linespec
9197 locations, explicit locations, or address locations. The following
9198 subsections describe these formats.
9201 * Linespec Locations:: Linespec locations
9202 * Explicit Locations:: Explicit locations
9203 * Address Locations:: Address locations
9206 @node Linespec Locations
9207 @subsection Linespec Locations
9208 @cindex linespec locations
9210 A @dfn{linespec} is a colon-separated list of source location parameters such
9211 as file name, function name, etc. Here are all the different ways of
9212 specifying a linespec:
9216 Specifies the line number @var{linenum} of the current source file.
9219 @itemx +@var{offset}
9220 Specifies the line @var{offset} lines before or after the @dfn{current
9221 line}. For the @code{list} command, the current line is the last one
9222 printed; for the breakpoint commands, this is the line at which
9223 execution stopped in the currently selected @dfn{stack frame}
9224 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9225 used as the second of the two linespecs in a @code{list} command,
9226 this specifies the line @var{offset} lines up or down from the first
9229 @item @var{filename}:@var{linenum}
9230 Specifies the line @var{linenum} in the source file @var{filename}.
9231 If @var{filename} is a relative file name, then it will match any
9232 source file name with the same trailing components. For example, if
9233 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9234 name of @file{/build/trunk/gcc/expr.c}, but not
9235 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9237 @item @var{function}
9238 Specifies the line that begins the body of the function @var{function}.
9239 For example, in C, this is the line with the open brace.
9241 By default, in C@t{++} and Ada, @var{function} is interpreted as
9242 specifying all functions named @var{function} in all scopes. For
9243 C@t{++}, this means in all namespaces and classes. For Ada, this
9244 means in all packages.
9246 For example, assuming a program with C@t{++} symbols named
9247 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9248 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9250 Commands that accept a linespec let you override this with the
9251 @code{-qualified} option. For example, @w{@kbd{break -qualified
9252 func}} sets a breakpoint on a free-function named @code{func} ignoring
9253 any C@t{++} class methods and namespace functions called @code{func}.
9255 @xref{Explicit Locations}.
9257 @item @var{function}:@var{label}
9258 Specifies the line where @var{label} appears in @var{function}.
9260 @item @var{filename}:@var{function}
9261 Specifies the line that begins the body of the function @var{function}
9262 in the file @var{filename}. You only need the file name with a
9263 function name to avoid ambiguity when there are identically named
9264 functions in different source files.
9267 Specifies the line at which the label named @var{label} appears
9268 in the function corresponding to the currently selected stack frame.
9269 If there is no current selected stack frame (for instance, if the inferior
9270 is not running), then @value{GDBN} will not search for a label.
9272 @cindex breakpoint at static probe point
9273 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9274 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9275 applications to embed static probes. @xref{Static Probe Points}, for more
9276 information on finding and using static probes. This form of linespec
9277 specifies the location of such a static probe.
9279 If @var{objfile} is given, only probes coming from that shared library
9280 or executable matching @var{objfile} as a regular expression are considered.
9281 If @var{provider} is given, then only probes from that provider are considered.
9282 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9283 each one of those probes.
9286 @node Explicit Locations
9287 @subsection Explicit Locations
9288 @cindex explicit locations
9290 @dfn{Explicit locations} allow the user to directly specify the source
9291 location's parameters using option-value pairs.
9293 Explicit locations are useful when several functions, labels, or
9294 file names have the same name (base name for files) in the program's
9295 sources. In these cases, explicit locations point to the source
9296 line you meant more accurately and unambiguously. Also, using
9297 explicit locations might be faster in large programs.
9299 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9300 defined in the file named @file{foo} or the label @code{bar} in a function
9301 named @code{foo}. @value{GDBN} must search either the file system or
9302 the symbol table to know.
9304 The list of valid explicit location options is summarized in the
9308 @item -source @var{filename}
9309 The value specifies the source file name. To differentiate between
9310 files with the same base name, prepend as many directories as is necessary
9311 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9312 @value{GDBN} will use the first file it finds with the given base
9313 name. This option requires the use of either @code{-function} or @code{-line}.
9315 @item -function @var{function}
9316 The value specifies the name of a function. Operations
9317 on function locations unmodified by other options (such as @code{-label}
9318 or @code{-line}) refer to the line that begins the body of the function.
9319 In C, for example, this is the line with the open brace.
9321 By default, in C@t{++} and Ada, @var{function} is interpreted as
9322 specifying all functions named @var{function} in all scopes. For
9323 C@t{++}, this means in all namespaces and classes. For Ada, this
9324 means in all packages.
9326 For example, assuming a program with C@t{++} symbols named
9327 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9328 -function func}} and @w{@kbd{break -function B::func}} set a
9329 breakpoint on both symbols.
9331 You can use the @kbd{-qualified} flag to override this (see below).
9335 This flag makes @value{GDBN} interpret a function name specified with
9336 @kbd{-function} as a complete fully-qualified name.
9338 For example, assuming a C@t{++} program with symbols named
9339 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9340 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9342 (Note: the @kbd{-qualified} option can precede a linespec as well
9343 (@pxref{Linespec Locations}), so the particular example above could be
9344 simplified as @w{@kbd{break -qualified B::func}}.)
9346 @item -label @var{label}
9347 The value specifies the name of a label. When the function
9348 name is not specified, the label is searched in the function of the currently
9349 selected stack frame.
9351 @item -line @var{number}
9352 The value specifies a line offset for the location. The offset may either
9353 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9354 the command. When specified without any other options, the line offset is
9355 relative to the current line.
9358 Explicit location options may be abbreviated by omitting any non-unique
9359 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9361 @node Address Locations
9362 @subsection Address Locations
9363 @cindex address locations
9365 @dfn{Address locations} indicate a specific program address. They have
9366 the generalized form *@var{address}.
9368 For line-oriented commands, such as @code{list} and @code{edit}, this
9369 specifies a source line that contains @var{address}. For @code{break} and
9370 other breakpoint-oriented commands, this can be used to set breakpoints in
9371 parts of your program which do not have debugging information or
9374 Here @var{address} may be any expression valid in the current working
9375 language (@pxref{Languages, working language}) that specifies a code
9376 address. In addition, as a convenience, @value{GDBN} extends the
9377 semantics of expressions used in locations to cover several situations
9378 that frequently occur during debugging. Here are the various forms
9382 @item @var{expression}
9383 Any expression valid in the current working language.
9385 @item @var{funcaddr}
9386 An address of a function or procedure derived from its name. In C,
9387 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9388 simply the function's name @var{function} (and actually a special case
9389 of a valid expression). In Pascal and Modula-2, this is
9390 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9391 (although the Pascal form also works).
9393 This form specifies the address of the function's first instruction,
9394 before the stack frame and arguments have been set up.
9396 @item '@var{filename}':@var{funcaddr}
9397 Like @var{funcaddr} above, but also specifies the name of the source
9398 file explicitly. This is useful if the name of the function does not
9399 specify the function unambiguously, e.g., if there are several
9400 functions with identical names in different source files.
9404 @section Editing Source Files
9405 @cindex editing source files
9408 @kindex e @r{(@code{edit})}
9409 To edit the lines in a source file, use the @code{edit} command.
9410 The editing program of your choice
9411 is invoked with the current line set to
9412 the active line in the program.
9413 Alternatively, there are several ways to specify what part of the file you
9414 want to print if you want to see other parts of the program:
9417 @item edit @var{locspec}
9418 Edit the source file of the code location that results from resolving
9419 @code{locspec}. Editing starts at the source file and source line
9420 @code{locspec} resolves to.
9421 @xref{Location Specifications}, for all the possible forms of the
9422 @var{locspec} argument.
9424 If @code{locspec} resolves to more than one source line in your
9425 program, then the command prints the list of resolved source lines and
9426 does not proceed with the editing.
9428 Here are the forms of the @code{edit} command most commonly used:
9431 @item edit @var{number}
9432 Edit the current source file with @var{number} as the active line number.
9434 @item edit @var{function}
9435 Edit the file containing @var{function} at the beginning of its definition.
9440 @subsection Choosing your Editor
9441 You can customize @value{GDBN} to use any editor you want
9443 The only restriction is that your editor (say @code{ex}), recognizes the
9444 following command-line syntax:
9446 ex +@var{number} file
9448 The optional numeric value +@var{number} specifies the number of the line in
9449 the file where to start editing.}.
9450 By default, it is @file{@value{EDITOR}}, but you can change this
9451 by setting the environment variable @env{EDITOR} before using
9452 @value{GDBN}. For example, to configure @value{GDBN} to use the
9453 @code{vi} editor, you could use these commands with the @code{sh} shell:
9459 or in the @code{csh} shell,
9461 setenv EDITOR /usr/bin/vi
9466 @section Searching Source Files
9467 @cindex searching source files
9469 There are two commands for searching through the current source file for a
9474 @kindex forward-search
9475 @kindex fo @r{(@code{forward-search})}
9476 @item forward-search @var{regexp}
9477 @itemx search @var{regexp}
9478 The command @samp{forward-search @var{regexp}} checks each line,
9479 starting with the one following the last line listed, for a match for
9480 @var{regexp}. It lists the line that is found. You can use the
9481 synonym @samp{search @var{regexp}} or abbreviate the command name as
9484 @kindex reverse-search
9485 @item reverse-search @var{regexp}
9486 The command @samp{reverse-search @var{regexp}} checks each line, starting
9487 with the one before the last line listed and going backward, for a match
9488 for @var{regexp}. It lists the line that is found. You can abbreviate
9489 this command as @code{rev}.
9493 @section Specifying Source Directories
9496 @cindex directories for source files
9497 Executable programs sometimes do not record the directories of the source
9498 files from which they were compiled, just the names. Even when they do,
9499 the directories could be moved between the compilation and your debugging
9500 session. @value{GDBN} has a list of directories to search for source files;
9501 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9502 it tries all the directories in the list, in the order they are present
9503 in the list, until it finds a file with the desired name.
9505 For example, suppose an executable references the file
9506 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9507 directory, and the @dfn{source path} is @file{/mnt/cross}.
9508 @value{GDBN} would look for the source file in the following
9513 @item @file{/usr/src/foo-1.0/lib/foo.c}
9514 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9515 @item @file{/mnt/cross/foo.c}
9519 If the source file is not present at any of the above locations then
9520 an error is printed. @value{GDBN} does not look up the parts of the
9521 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9522 Likewise, the subdirectories of the source path are not searched: if
9523 the source path is @file{/mnt/cross}, and the binary refers to
9524 @file{foo.c}, @value{GDBN} would not find it under
9525 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9527 Plain file names, relative file names with leading directories, file
9528 names containing dots, etc.@: are all treated as described above,
9529 except that non-absolute file names are not looked up literally. If
9530 the @dfn{source path} is @file{/mnt/cross}, the source file is
9531 recorded as @file{../lib/foo.c}, and no compilation directory is
9532 recorded, then @value{GDBN} will search in the following locations:
9536 @item @file{/mnt/cross/../lib/foo.c}
9537 @item @file{/mnt/cross/foo.c}
9543 @vindex $cdir@r{, convenience variable}
9544 @vindex $cwd@r{, convenience variable}
9545 @cindex compilation directory
9546 @cindex current directory
9547 @cindex working directory
9548 @cindex directory, current
9549 @cindex directory, compilation
9550 The @dfn{source path} will always include two special entries
9551 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9552 (if one is recorded) and the current working directory respectively.
9554 @samp{$cdir} causes @value{GDBN} to search within the compilation
9555 directory, if one is recorded in the debug information. If no
9556 compilation directory is recorded in the debug information then
9557 @samp{$cdir} is ignored.
9559 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9560 current working directory as it changes during your @value{GDBN}
9561 session, while the latter is immediately expanded to the current
9562 directory at the time you add an entry to the source path.
9564 If a compilation directory is recorded in the debug information, and
9565 @value{GDBN} has not found the source file after the first search
9566 using @dfn{source path}, then @value{GDBN} will combine the
9567 compilation directory and the filename, and then search for the source
9568 file again using the @dfn{source path}.
9570 For example, if the executable records the source file as
9571 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9572 recorded as @file{/project/build}, and the @dfn{source path} is
9573 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9574 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9575 search for the source file in the following locations:
9579 @item @file{/usr/src/foo-1.0/lib/foo.c}
9580 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9581 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9582 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9583 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9584 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9585 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9586 @item @file{/mnt/cross/foo.c}
9587 @item @file{/project/build/foo.c}
9588 @item @file{/home/user/foo.c}
9592 If the file name in the previous example had been recorded in the
9593 executable as a relative path rather than an absolute path, then the
9594 first look up would not have occurred, but all of the remaining steps
9597 When searching for source files on MS-DOS and MS-Windows, where
9598 absolute paths start with a drive letter (e.g.@:
9599 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9600 from the file name before appending it to a search directory from
9601 @dfn{source path}; for instance if the executable references the
9602 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9603 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9604 locations for the source file:
9608 @item @file{C:/project/foo.c}
9609 @item @file{D:/mnt/cross/project/foo.c}
9610 @item @file{D:/mnt/cross/foo.c}
9614 Note that the executable search path is @emph{not} used to locate the
9617 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9618 any information it has cached about where source files are found and where
9619 each line is in the file.
9623 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9624 and @samp{$cwd}, in that order.
9625 To add other directories, use the @code{directory} command.
9627 The search path is used to find both program source files and @value{GDBN}
9628 script files (read using the @samp{-command} option and @samp{source} command).
9630 In addition to the source path, @value{GDBN} provides a set of commands
9631 that manage a list of source path substitution rules. A @dfn{substitution
9632 rule} specifies how to rewrite source directories stored in the program's
9633 debug information in case the sources were moved to a different
9634 directory between compilation and debugging. A rule is made of
9635 two strings, the first specifying what needs to be rewritten in
9636 the path, and the second specifying how it should be rewritten.
9637 In @ref{set substitute-path}, we name these two parts @var{from} and
9638 @var{to} respectively. @value{GDBN} does a simple string replacement
9639 of @var{from} with @var{to} at the start of the directory part of the
9640 source file name, and uses that result instead of the original file
9641 name to look up the sources.
9643 Using the previous example, suppose the @file{foo-1.0} tree has been
9644 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9645 @value{GDBN} to replace @file{/usr/src} in all source path names with
9646 @file{/mnt/cross}. The first lookup will then be
9647 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9648 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9649 substitution rule, use the @code{set substitute-path} command
9650 (@pxref{set substitute-path}).
9652 To avoid unexpected substitution results, a rule is applied only if the
9653 @var{from} part of the directory name ends at a directory separator.
9654 For instance, a rule substituting @file{/usr/source} into
9655 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9656 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9657 is applied only at the beginning of the directory name, this rule will
9658 not be applied to @file{/root/usr/source/baz.c} either.
9660 In many cases, you can achieve the same result using the @code{directory}
9661 command. However, @code{set substitute-path} can be more efficient in
9662 the case where the sources are organized in a complex tree with multiple
9663 subdirectories. With the @code{directory} command, you need to add each
9664 subdirectory of your project. If you moved the entire tree while
9665 preserving its internal organization, then @code{set substitute-path}
9666 allows you to direct the debugger to all the sources with one single
9669 @code{set substitute-path} is also more than just a shortcut command.
9670 The source path is only used if the file at the original location no
9671 longer exists. On the other hand, @code{set substitute-path} modifies
9672 the debugger behavior to look at the rewritten location instead. So, if
9673 for any reason a source file that is not relevant to your executable is
9674 located at the original location, a substitution rule is the only
9675 method available to point @value{GDBN} at the new location.
9677 @cindex @samp{--with-relocated-sources}
9678 @cindex default source path substitution
9679 You can configure a default source path substitution rule by
9680 configuring @value{GDBN} with the
9681 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9682 should be the name of a directory under @value{GDBN}'s configured
9683 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9684 directory names in debug information under @var{dir} will be adjusted
9685 automatically if the installed @value{GDBN} is moved to a new
9686 location. This is useful if @value{GDBN}, libraries or executables
9687 with debug information and corresponding source code are being moved
9691 @item directory @var{dirname} @dots{}
9692 @item dir @var{dirname} @dots{}
9693 Add directory @var{dirname} to the front of the source path. Several
9694 directory names may be given to this command, separated by @samp{:}
9695 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9696 part of absolute file names) or
9697 whitespace. You may specify a directory that is already in the source
9698 path; this moves it forward, so @value{GDBN} searches it sooner.
9700 The special strings @samp{$cdir} (to refer to the compilation
9701 directory, if one is recorded), and @samp{$cwd} (to refer to the
9702 current working directory) can also be included in the list of
9703 directories @var{dirname}. Though these will already be in the source
9704 path they will be moved forward in the list so @value{GDBN} searches
9708 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9710 @c RET-repeat for @code{directory} is explicitly disabled, but since
9711 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9713 @item set directories @var{path-list}
9714 @kindex set directories
9715 Set the source path to @var{path-list}.
9716 @samp{$cdir:$cwd} are added if missing.
9718 @item show directories
9719 @kindex show directories
9720 Print the source path: show which directories it contains.
9722 @anchor{set substitute-path}
9723 @item set substitute-path @var{from} @var{to}
9724 @kindex set substitute-path
9725 Define a source path substitution rule, and add it at the end of the
9726 current list of existing substitution rules. If a rule with the same
9727 @var{from} was already defined, then the old rule is also deleted.
9729 For example, if the file @file{/foo/bar/baz.c} was moved to
9730 @file{/mnt/cross/baz.c}, then the command
9733 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9737 will tell @value{GDBN} to replace @samp{/foo/bar} with
9738 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9739 @file{baz.c} even though it was moved.
9741 In the case when more than one substitution rule have been defined,
9742 the rules are evaluated one by one in the order where they have been
9743 defined. The first one matching, if any, is selected to perform
9746 For instance, if we had entered the following commands:
9749 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9750 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9754 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9755 @file{/mnt/include/defs.h} by using the first rule. However, it would
9756 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9757 @file{/mnt/src/lib/foo.c}.
9760 @item unset substitute-path [path]
9761 @kindex unset substitute-path
9762 If a path is specified, search the current list of substitution rules
9763 for a rule that would rewrite that path. Delete that rule if found.
9764 A warning is emitted by the debugger if no rule could be found.
9766 If no path is specified, then all substitution rules are deleted.
9768 @item show substitute-path [path]
9769 @kindex show substitute-path
9770 If a path is specified, then print the source path substitution rule
9771 which would rewrite that path, if any.
9773 If no path is specified, then print all existing source path substitution
9778 If your source path is cluttered with directories that are no longer of
9779 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9780 versions of source. You can correct the situation as follows:
9784 Use @code{directory} with no argument to reset the source path to its default value.
9787 Use @code{directory} with suitable arguments to reinstall the
9788 directories you want in the source path. You can add all the
9789 directories in one command.
9793 @section Source and Machine Code
9794 @cindex source line and its code address
9796 You can use the command @code{info line} to map source lines to program
9797 addresses (and vice versa), and the command @code{disassemble} to display
9798 a range of addresses as machine instructions. You can use the command
9799 @code{set disassemble-next-line} to set whether to disassemble next
9800 source line when execution stops. When run under @sc{gnu} Emacs
9801 mode, the @code{info line} command causes the arrow to point to the
9802 line specified. Also, @code{info line} prints addresses in symbolic form as
9808 @itemx info line @var{locspec}
9809 Print the starting and ending addresses of the compiled code for the
9810 source lines of the code locations that result from resolving
9811 @var{locspec}. @xref{Location Specifications}, for the various forms
9813 With no @var{locspec}, information about the current source line is
9817 For example, we can use @code{info line} to discover the location of
9818 the object code for the first line of function
9819 @code{m4_changequote}:
9822 (@value{GDBP}) info line m4_changequote
9823 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9824 ends at 0x6350 <m4_changequote+4>.
9828 @cindex code address and its source line
9829 We can also inquire, using @code{*@var{addr}} as the form for
9830 @var{locspec}, what source line covers a particular address
9833 (@value{GDBP}) info line *0x63ff
9834 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9835 ends at 0x6404 <m4_changequote+184>.
9838 @cindex @code{$_} and @code{info line}
9839 @cindex @code{x} command, default address
9840 @kindex x@r{(examine), and} info line
9841 After @code{info line}, the default address for the @code{x} command
9842 is changed to the starting address of the line, so that @samp{x/i} is
9843 sufficient to begin examining the machine code (@pxref{Memory,
9844 ,Examining Memory}). Also, this address is saved as the value of the
9845 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9848 @cindex info line, repeated calls
9849 After @code{info line}, using @code{info line} again without
9850 specifying a location will display information about the next source
9855 @cindex assembly instructions
9856 @cindex instructions, assembly
9857 @cindex machine instructions
9858 @cindex listing machine instructions
9860 @itemx disassemble /m
9861 @itemx disassemble /s
9862 @itemx disassemble /r
9863 This specialized command dumps a range of memory as machine
9864 instructions. It can also print mixed source+disassembly by specifying
9865 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9866 as well as in symbolic form by specifying the @code{/r} modifier.
9867 The default memory range is the function surrounding the
9868 program counter of the selected frame. A single argument to this
9869 command is a program counter value; @value{GDBN} dumps the function
9870 surrounding this value. When two arguments are given, they should
9871 be separated by a comma, possibly surrounded by whitespace. The
9872 arguments specify a range of addresses to dump, in one of two forms:
9875 @item @var{start},@var{end}
9876 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9877 @item @var{start},+@var{length}
9878 the addresses from @var{start} (inclusive) to
9879 @code{@var{start}+@var{length}} (exclusive).
9883 When 2 arguments are specified, the name of the function is also
9884 printed (since there could be several functions in the given range).
9886 The argument(s) can be any expression yielding a numeric value, such as
9887 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9889 If the range of memory being disassembled contains current program counter,
9890 the instruction at that location is shown with a @code{=>} marker.
9893 The following example shows the disassembly of a range of addresses of
9894 HP PA-RISC 2.0 code:
9897 (@value{GDBP}) disas 0x32c4, 0x32e4
9898 Dump of assembler code from 0x32c4 to 0x32e4:
9899 0x32c4 <main+204>: addil 0,dp
9900 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9901 0x32cc <main+212>: ldil 0x3000,r31
9902 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9903 0x32d4 <main+220>: ldo 0(r31),rp
9904 0x32d8 <main+224>: addil -0x800,dp
9905 0x32dc <main+228>: ldo 0x588(r1),r26
9906 0x32e0 <main+232>: ldil 0x3000,r31
9907 End of assembler dump.
9910 Here is an example showing mixed source+assembly for Intel x86
9911 with @code{/m} or @code{/s}, when the program is stopped just after
9912 function prologue in a non-optimized function with no inline code.
9915 (@value{GDBP}) disas /m main
9916 Dump of assembler code for function main:
9918 0x08048330 <+0>: push %ebp
9919 0x08048331 <+1>: mov %esp,%ebp
9920 0x08048333 <+3>: sub $0x8,%esp
9921 0x08048336 <+6>: and $0xfffffff0,%esp
9922 0x08048339 <+9>: sub $0x10,%esp
9924 6 printf ("Hello.\n");
9925 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9926 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9930 0x08048348 <+24>: mov $0x0,%eax
9931 0x0804834d <+29>: leave
9932 0x0804834e <+30>: ret
9934 End of assembler dump.
9937 The @code{/m} option is deprecated as its output is not useful when
9938 there is either inlined code or re-ordered code.
9939 The @code{/s} option is the preferred choice.
9940 Here is an example for AMD x86-64 showing the difference between
9941 @code{/m} output and @code{/s} output.
9942 This example has one inline function defined in a header file,
9943 and the code is compiled with @samp{-O2} optimization.
9944 Note how the @code{/m} output is missing the disassembly of
9945 several instructions that are present in the @code{/s} output.
9975 (@value{GDBP}) disas /m main
9976 Dump of assembler code for function main:
9980 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9981 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9985 0x000000000040041d <+29>: xor %eax,%eax
9986 0x000000000040041f <+31>: retq
9987 0x0000000000400420 <+32>: add %eax,%eax
9988 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9990 End of assembler dump.
9991 (@value{GDBP}) disas /s main
9992 Dump of assembler code for function main:
9996 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10000 0x0000000000400406 <+6>: test %eax,%eax
10001 0x0000000000400408 <+8>: js 0x400420 <main+32>
10006 0x000000000040040a <+10>: lea 0xa(%rax),%edx
10007 0x000000000040040d <+13>: test %eax,%eax
10008 0x000000000040040f <+15>: mov $0x1,%eax
10009 0x0000000000400414 <+20>: cmovne %edx,%eax
10013 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10017 0x000000000040041d <+29>: xor %eax,%eax
10018 0x000000000040041f <+31>: retq
10022 0x0000000000400420 <+32>: add %eax,%eax
10023 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10024 End of assembler dump.
10027 Here is another example showing raw instructions in hex for AMD x86-64,
10030 (gdb) disas /r 0x400281,+10
10031 Dump of assembler code from 0x400281 to 0x40028b:
10032 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10033 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10034 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10035 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10036 End of assembler dump.
10039 Note that the @samp{disassemble} command's address arguments are
10040 specified using expressions in your programming language
10041 (@pxref{Expressions, ,Expressions}), not location specs
10042 (@pxref{Location Specifications}). So, for example, if you want to
10043 disassemble function @code{bar} in file @file{foo.c}, you must type
10044 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10046 Some architectures have more than one commonly-used set of instruction
10047 mnemonics or other syntax.
10049 For programs that were dynamically linked and use shared libraries,
10050 instructions that call functions or branch to locations in the shared
10051 libraries might show a seemingly bogus location---it's actually a
10052 location of the relocation table. On some architectures, @value{GDBN}
10053 might be able to resolve these to actual function names.
10056 @kindex set disassembler-options
10057 @cindex disassembler options
10058 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10059 This command controls the passing of target specific information to
10060 the disassembler. For a list of valid options, please refer to the
10061 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10062 manual and/or the output of @kbd{objdump --help}
10063 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10064 The default value is the empty string.
10066 If it is necessary to specify more than one disassembler option, then
10067 multiple options can be placed together into a comma separated list.
10068 Currently this command is only supported on targets ARC, ARM, MIPS,
10071 @kindex show disassembler-options
10072 @item show disassembler-options
10073 Show the current setting of the disassembler options.
10077 @kindex set disassembly-flavor
10078 @cindex Intel disassembly flavor
10079 @cindex AT&T disassembly flavor
10080 @item set disassembly-flavor @var{instruction-set}
10081 Select the instruction set to use when disassembling the
10082 program via the @code{disassemble} or @code{x/i} commands.
10084 Currently this command is only defined for the Intel x86 family. You
10085 can set @var{instruction-set} to either @code{intel} or @code{att}.
10086 The default is @code{att}, the AT&T flavor used by default by Unix
10087 assemblers for x86-based targets.
10089 @kindex show disassembly-flavor
10090 @item show disassembly-flavor
10091 Show the current setting of the disassembly flavor.
10095 @kindex set disassemble-next-line
10096 @kindex show disassemble-next-line
10097 @item set disassemble-next-line
10098 @itemx show disassemble-next-line
10099 Control whether or not @value{GDBN} will disassemble the next source
10100 line or instruction when execution stops. If ON, @value{GDBN} will
10101 display disassembly of the next source line when execution of the
10102 program being debugged stops. This is @emph{in addition} to
10103 displaying the source line itself, which @value{GDBN} always does if
10104 possible. If the next source line cannot be displayed for some reason
10105 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10106 info in the debug info), @value{GDBN} will display disassembly of the
10107 next @emph{instruction} instead of showing the next source line. If
10108 AUTO, @value{GDBN} will display disassembly of next instruction only
10109 if the source line cannot be displayed. This setting causes
10110 @value{GDBN} to display some feedback when you step through a function
10111 with no line info or whose source file is unavailable. The default is
10112 OFF, which means never display the disassembly of the next line or
10116 @node Disable Reading Source
10117 @section Disable Reading Source Code
10118 @cindex source code, disable access
10120 In some cases it can be desirable to prevent @value{GDBN} from
10121 accessing source code files. One case where this might be desirable
10122 is if the source code files are located over a slow network
10125 The following command can be used to control whether @value{GDBN}
10126 should access source code files or not:
10129 @kindex set source open
10130 @kindex show source open
10131 @item set source open @r{[}on@r{|}off@r{]}
10132 @itemx show source open
10133 When this option is @code{on}, which is the default, @value{GDBN} will
10134 access source code files when needed, for example to print source
10135 lines when @value{GDBN} stops, or in response to the @code{list}
10138 When this option is @code{off}, @value{GDBN} will not access source
10143 @chapter Examining Data
10145 @cindex printing data
10146 @cindex examining data
10149 The usual way to examine data in your program is with the @code{print}
10150 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10151 evaluates and prints the value of an expression of the language your
10152 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10153 Different Languages}). It may also print the expression using a
10154 Python-based pretty-printer (@pxref{Pretty Printing}).
10157 @item print [[@var{options}] --] @var{expr}
10158 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10159 @var{expr} is an expression (in the source language). By default the
10160 value of @var{expr} is printed in a format appropriate to its data type;
10161 you can choose a different format by specifying @samp{/@var{f}}, where
10162 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10165 @anchor{print options}
10166 The @code{print} command supports a number of options that allow
10167 overriding relevant global print settings as set by @code{set print}
10171 @item -address [@code{on}|@code{off}]
10172 Set printing of addresses.
10173 Related setting: @ref{set print address}.
10175 @item -array [@code{on}|@code{off}]
10176 Pretty formatting of arrays.
10177 Related setting: @ref{set print array}.
10179 @item -array-indexes [@code{on}|@code{off}]
10180 Set printing of array indexes.
10181 Related setting: @ref{set print array-indexes}.
10183 @item -elements @var{number-of-elements}|@code{unlimited}
10184 Set limit on string chars or array elements to print. The value
10185 @code{unlimited} causes there to be no limit. Related setting:
10186 @ref{set print elements}.
10188 @item -max-depth @var{depth}|@code{unlimited}
10189 Set the threshold after which nested structures are replaced with
10190 ellipsis. Related setting: @ref{set print max-depth}.
10192 @item -nibbles [@code{on}|@code{off}]
10193 Set whether to print binary values in groups of four bits, known
10194 as ``nibbles''. @xref{set print nibbles}.
10196 @item -memory-tag-violations [@code{on}|@code{off}]
10197 Set printing of additional information about memory tag violations.
10198 @xref{set print memory-tag-violations}.
10200 @item -null-stop [@code{on}|@code{off}]
10201 Set printing of char arrays to stop at first null char. Related
10202 setting: @ref{set print null-stop}.
10204 @item -object [@code{on}|@code{off}]
10205 Set printing C@t{++} virtual function tables. Related setting:
10206 @ref{set print object}.
10208 @item -pretty [@code{on}|@code{off}]
10209 Set pretty formatting of structures. Related setting: @ref{set print
10212 @item -raw-values [@code{on}|@code{off}]
10213 Set whether to print values in raw form, bypassing any
10214 pretty-printers for that value. Related setting: @ref{set print
10217 @item -repeats @var{number-of-repeats}|@code{unlimited}
10218 Set threshold for repeated print elements. @code{unlimited} causes
10219 all elements to be individually printed. Related setting: @ref{set
10222 @item -static-members [@code{on}|@code{off}]
10223 Set printing C@t{++} static members. Related setting: @ref{set print
10226 @item -symbol [@code{on}|@code{off}]
10227 Set printing of symbol names when printing pointers. Related setting:
10228 @ref{set print symbol}.
10230 @item -union [@code{on}|@code{off}]
10231 Set printing of unions interior to structures. Related setting:
10232 @ref{set print union}.
10234 @item -vtbl [@code{on}|@code{off}]
10235 Set printing of C++ virtual function tables. Related setting:
10236 @ref{set print vtbl}.
10239 Because the @code{print} command accepts arbitrary expressions which
10240 may look like options (including abbreviations), if you specify any
10241 command option, then you must use a double dash (@code{--}) to mark
10242 the end of option processing.
10244 For example, this prints the value of the @code{-p} expression:
10247 (@value{GDBP}) print -p
10250 While this repeats the last value in the value history (see below)
10251 with the @code{-pretty} option in effect:
10254 (@value{GDBP}) print -p --
10257 Here is an example including both on option and an expression:
10261 (@value{GDBP}) print -pretty -- *myptr
10273 @item print [@var{options}]
10274 @itemx print [@var{options}] /@var{f}
10275 @cindex reprint the last value
10276 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10277 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10278 conveniently inspect the same value in an alternative format.
10281 If the architecture supports memory tagging, the @code{print} command will
10282 display pointer/memory tag mismatches if what is being printed is a pointer
10283 or reference type. @xref{Memory Tagging}.
10285 A more low-level way of examining data is with the @code{x} command.
10286 It examines data in memory at a specified address and prints it in a
10287 specified format. @xref{Memory, ,Examining Memory}.
10289 If you are interested in information about types, or about how the
10290 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10291 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10294 @cindex exploring hierarchical data structures
10296 Another way of examining values of expressions and type information is
10297 through the Python extension command @code{explore} (available only if
10298 the @value{GDBN} build is configured with @code{--with-python}). It
10299 offers an interactive way to start at the highest level (or, the most
10300 abstract level) of the data type of an expression (or, the data type
10301 itself) and explore all the way down to leaf scalar values/fields
10302 embedded in the higher level data types.
10305 @item explore @var{arg}
10306 @var{arg} is either an expression (in the source language), or a type
10307 visible in the current context of the program being debugged.
10310 The working of the @code{explore} command can be illustrated with an
10311 example. If a data type @code{struct ComplexStruct} is defined in your
10315 struct SimpleStruct
10321 struct ComplexStruct
10323 struct SimpleStruct *ss_p;
10329 followed by variable declarations as
10332 struct SimpleStruct ss = @{ 10, 1.11 @};
10333 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10337 then, the value of the variable @code{cs} can be explored using the
10338 @code{explore} command as follows.
10342 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10343 the following fields:
10345 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10346 arr = <Enter 1 to explore this field of type `int [10]'>
10348 Enter the field number of choice:
10352 Since the fields of @code{cs} are not scalar values, you are being
10353 prompted to chose the field you want to explore. Let's say you choose
10354 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10355 pointer, you will be asked if it is pointing to a single value. From
10356 the declaration of @code{cs} above, it is indeed pointing to a single
10357 value, hence you enter @code{y}. If you enter @code{n}, then you will
10358 be asked if it were pointing to an array of values, in which case this
10359 field will be explored as if it were an array.
10362 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10363 Continue exploring it as a pointer to a single value [y/n]: y
10364 The value of `*(cs.ss_p)' is a struct/class of type `struct
10365 SimpleStruct' with the following fields:
10367 i = 10 .. (Value of type `int')
10368 d = 1.1100000000000001 .. (Value of type `double')
10370 Press enter to return to parent value:
10374 If the field @code{arr} of @code{cs} was chosen for exploration by
10375 entering @code{1} earlier, then since it is as array, you will be
10376 prompted to enter the index of the element in the array that you want
10380 `cs.arr' is an array of `int'.
10381 Enter the index of the element you want to explore in `cs.arr': 5
10383 `(cs.arr)[5]' is a scalar value of type `int'.
10387 Press enter to return to parent value:
10390 In general, at any stage of exploration, you can go deeper towards the
10391 leaf values by responding to the prompts appropriately, or hit the
10392 return key to return to the enclosing data structure (the @i{higher}
10393 level data structure).
10395 Similar to exploring values, you can use the @code{explore} command to
10396 explore types. Instead of specifying a value (which is typically a
10397 variable name or an expression valid in the current context of the
10398 program being debugged), you specify a type name. If you consider the
10399 same example as above, your can explore the type
10400 @code{struct ComplexStruct} by passing the argument
10401 @code{struct ComplexStruct} to the @code{explore} command.
10404 (gdb) explore struct ComplexStruct
10408 By responding to the prompts appropriately in the subsequent interactive
10409 session, you can explore the type @code{struct ComplexStruct} in a
10410 manner similar to how the value @code{cs} was explored in the above
10413 The @code{explore} command also has two sub-commands,
10414 @code{explore value} and @code{explore type}. The former sub-command is
10415 a way to explicitly specify that value exploration of the argument is
10416 being invoked, while the latter is a way to explicitly specify that type
10417 exploration of the argument is being invoked.
10420 @item explore value @var{expr}
10421 @cindex explore value
10422 This sub-command of @code{explore} explores the value of the
10423 expression @var{expr} (if @var{expr} is an expression valid in the
10424 current context of the program being debugged). The behavior of this
10425 command is identical to that of the behavior of the @code{explore}
10426 command being passed the argument @var{expr}.
10428 @item explore type @var{arg}
10429 @cindex explore type
10430 This sub-command of @code{explore} explores the type of @var{arg} (if
10431 @var{arg} is a type visible in the current context of program being
10432 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10433 is an expression valid in the current context of the program being
10434 debugged). If @var{arg} is a type, then the behavior of this command is
10435 identical to that of the @code{explore} command being passed the
10436 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10437 this command will be identical to that of the @code{explore} command
10438 being passed the type of @var{arg} as the argument.
10442 * Expressions:: Expressions
10443 * Ambiguous Expressions:: Ambiguous Expressions
10444 * Variables:: Program variables
10445 * Arrays:: Artificial arrays
10446 * Output Formats:: Output formats
10447 * Memory:: Examining memory
10448 * Memory Tagging:: Memory Tagging
10449 * Auto Display:: Automatic display
10450 * Print Settings:: Print settings
10451 * Pretty Printing:: Python pretty printing
10452 * Value History:: Value history
10453 * Convenience Vars:: Convenience variables
10454 * Convenience Funs:: Convenience functions
10455 * Registers:: Registers
10456 * Floating Point Hardware:: Floating point hardware
10457 * Vector Unit:: Vector Unit
10458 * OS Information:: Auxiliary data provided by operating system
10459 * Memory Region Attributes:: Memory region attributes
10460 * Dump/Restore Files:: Copy between memory and a file
10461 * Core File Generation:: Cause a program dump its core
10462 * Character Sets:: Debugging programs that use a different
10463 character set than GDB does
10464 * Caching Target Data:: Data caching for targets
10465 * Searching Memory:: Searching memory for a sequence of bytes
10466 * Value Sizes:: Managing memory allocated for values
10470 @section Expressions
10472 @cindex expressions
10473 @code{print} and many other @value{GDBN} commands accept an expression and
10474 compute its value. Any kind of constant, variable or operator defined
10475 by the programming language you are using is valid in an expression in
10476 @value{GDBN}. This includes conditional expressions, function calls,
10477 casts, and string constants. It also includes preprocessor macros, if
10478 you compiled your program to include this information; see
10481 @cindex arrays in expressions
10482 @value{GDBN} supports array constants in expressions input by
10483 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10484 you can use the command @code{print @{1, 2, 3@}} to create an array
10485 of three integers. If you pass an array to a function or assign it
10486 to a program variable, @value{GDBN} copies the array to memory that
10487 is @code{malloc}ed in the target program.
10489 Because C is so widespread, most of the expressions shown in examples in
10490 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10491 Languages}, for information on how to use expressions in other
10494 In this section, we discuss operators that you can use in @value{GDBN}
10495 expressions regardless of your programming language.
10497 @cindex casts, in expressions
10498 Casts are supported in all languages, not just in C, because it is so
10499 useful to cast a number into a pointer in order to examine a structure
10500 at that address in memory.
10501 @c FIXME: casts supported---Mod2 true?
10503 @value{GDBN} supports these operators, in addition to those common
10504 to programming languages:
10508 @samp{@@} is a binary operator for treating parts of memory as arrays.
10509 @xref{Arrays, ,Artificial Arrays}, for more information.
10512 @samp{::} allows you to specify a variable in terms of the file or
10513 function where it is defined. @xref{Variables, ,Program Variables}.
10515 @cindex @{@var{type}@}
10516 @cindex type casting memory
10517 @cindex memory, viewing as typed object
10518 @cindex casts, to view memory
10519 @item @{@var{type}@} @var{addr}
10520 Refers to an object of type @var{type} stored at address @var{addr} in
10521 memory. The address @var{addr} may be any expression whose value is
10522 an integer or pointer (but parentheses are required around binary
10523 operators, just as in a cast). This construct is allowed regardless
10524 of what kind of data is normally supposed to reside at @var{addr}.
10527 @node Ambiguous Expressions
10528 @section Ambiguous Expressions
10529 @cindex ambiguous expressions
10531 Expressions can sometimes contain some ambiguous elements. For instance,
10532 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10533 a single function name to be defined several times, for application in
10534 different contexts. This is called @dfn{overloading}. Another example
10535 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10536 templates and is typically instantiated several times, resulting in
10537 the same function name being defined in different contexts.
10539 In some cases and depending on the language, it is possible to adjust
10540 the expression to remove the ambiguity. For instance in C@t{++}, you
10541 can specify the signature of the function you want to break on, as in
10542 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10543 qualified name of your function often makes the expression unambiguous
10546 When an ambiguity that needs to be resolved is detected, the debugger
10547 has the capability to display a menu of numbered choices for each
10548 possibility, and then waits for the selection with the prompt @samp{>}.
10549 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10550 aborts the current command. If the command in which the expression was
10551 used allows more than one choice to be selected, the next option in the
10552 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10555 For example, the following session excerpt shows an attempt to set a
10556 breakpoint at the overloaded symbol @code{String::after}.
10557 We choose three particular definitions of that function name:
10559 @c FIXME! This is likely to change to show arg type lists, at least
10562 (@value{GDBP}) b String::after
10565 [2] file:String.cc; line number:867
10566 [3] file:String.cc; line number:860
10567 [4] file:String.cc; line number:875
10568 [5] file:String.cc; line number:853
10569 [6] file:String.cc; line number:846
10570 [7] file:String.cc; line number:735
10572 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10573 Breakpoint 2 at 0xb344: file String.cc, line 875.
10574 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10575 Multiple breakpoints were set.
10576 Use the "delete" command to delete unwanted
10583 @kindex set multiple-symbols
10584 @item set multiple-symbols @var{mode}
10585 @cindex multiple-symbols menu
10587 This option allows you to adjust the debugger behavior when an expression
10590 By default, @var{mode} is set to @code{all}. If the command with which
10591 the expression is used allows more than one choice, then @value{GDBN}
10592 automatically selects all possible choices. For instance, inserting
10593 a breakpoint on a function using an ambiguous name results in a breakpoint
10594 inserted on each possible match. However, if a unique choice must be made,
10595 then @value{GDBN} uses the menu to help you disambiguate the expression.
10596 For instance, printing the address of an overloaded function will result
10597 in the use of the menu.
10599 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10600 when an ambiguity is detected.
10602 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10603 an error due to the ambiguity and the command is aborted.
10605 @kindex show multiple-symbols
10606 @item show multiple-symbols
10607 Show the current value of the @code{multiple-symbols} setting.
10611 @section Program Variables
10613 The most common kind of expression to use is the name of a variable
10616 Variables in expressions are understood in the selected stack frame
10617 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10621 global (or file-static)
10628 visible according to the scope rules of the
10629 programming language from the point of execution in that frame
10632 @noindent This means that in the function
10647 you can examine and use the variable @code{a} whenever your program is
10648 executing within the function @code{foo}, but you can only use or
10649 examine the variable @code{b} while your program is executing inside
10650 the block where @code{b} is declared.
10652 @cindex variable name conflict
10653 There is an exception: you can refer to a variable or function whose
10654 scope is a single source file even if the current execution point is not
10655 in this file. But it is possible to have more than one such variable or
10656 function with the same name (in different source files). If that
10657 happens, referring to that name has unpredictable effects. If you wish,
10658 you can specify a static variable in a particular function or file by
10659 using the colon-colon (@code{::}) notation:
10661 @cindex colon-colon, context for variables/functions
10663 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10664 @cindex @code{::}, context for variables/functions
10667 @var{file}::@var{variable}
10668 @var{function}::@var{variable}
10672 Here @var{file} or @var{function} is the name of the context for the
10673 static @var{variable}. In the case of file names, you can use quotes to
10674 make sure @value{GDBN} parses the file name as a single word---for example,
10675 to print a global value of @code{x} defined in @file{f2.c}:
10678 (@value{GDBP}) p 'f2.c'::x
10681 The @code{::} notation is normally used for referring to
10682 static variables, since you typically disambiguate uses of local variables
10683 in functions by selecting the appropriate frame and using the
10684 simple name of the variable. However, you may also use this notation
10685 to refer to local variables in frames enclosing the selected frame:
10694 process (a); /* Stop here */
10705 For example, if there is a breakpoint at the commented line,
10706 here is what you might see
10707 when the program stops after executing the call @code{bar(0)}:
10712 (@value{GDBP}) p bar::a
10714 (@value{GDBP}) up 2
10715 #2 0x080483d0 in foo (a=5) at foobar.c:12
10718 (@value{GDBP}) p bar::a
10722 @cindex C@t{++} scope resolution
10723 These uses of @samp{::} are very rarely in conflict with the very
10724 similar use of the same notation in C@t{++}. When they are in
10725 conflict, the C@t{++} meaning takes precedence; however, this can be
10726 overridden by quoting the file or function name with single quotes.
10728 For example, suppose the program is stopped in a method of a class
10729 that has a field named @code{includefile}, and there is also an
10730 include file named @file{includefile} that defines a variable,
10731 @code{some_global}.
10734 (@value{GDBP}) p includefile
10736 (@value{GDBP}) p includefile::some_global
10737 A syntax error in expression, near `'.
10738 (@value{GDBP}) p 'includefile'::some_global
10742 @cindex wrong values
10743 @cindex variable values, wrong
10744 @cindex function entry/exit, wrong values of variables
10745 @cindex optimized code, wrong values of variables
10747 @emph{Warning:} Occasionally, a local variable may appear to have the
10748 wrong value at certain points in a function---just after entry to a new
10749 scope, and just before exit.
10751 You may see this problem when you are stepping by machine instructions.
10752 This is because, on most machines, it takes more than one instruction to
10753 set up a stack frame (including local variable definitions); if you are
10754 stepping by machine instructions, variables may appear to have the wrong
10755 values until the stack frame is completely built. On exit, it usually
10756 also takes more than one machine instruction to destroy a stack frame;
10757 after you begin stepping through that group of instructions, local
10758 variable definitions may be gone.
10760 This may also happen when the compiler does significant optimizations.
10761 To be sure of always seeing accurate values, turn off all optimization
10764 @cindex ``No symbol "foo" in current context''
10765 Another possible effect of compiler optimizations is to optimize
10766 unused variables out of existence, or assign variables to registers (as
10767 opposed to memory addresses). Depending on the support for such cases
10768 offered by the debug info format used by the compiler, @value{GDBN}
10769 might not be able to display values for such local variables. If that
10770 happens, @value{GDBN} will print a message like this:
10773 No symbol "foo" in current context.
10776 To solve such problems, either recompile without optimizations, or use a
10777 different debug info format, if the compiler supports several such
10778 formats. @xref{Compilation}, for more information on choosing compiler
10779 options. @xref{C, ,C and C@t{++}}, for more information about debug
10780 info formats that are best suited to C@t{++} programs.
10782 If you ask to print an object whose contents are unknown to
10783 @value{GDBN}, e.g., because its data type is not completely specified
10784 by the debug information, @value{GDBN} will say @samp{<incomplete
10785 type>}. @xref{Symbols, incomplete type}, for more about this.
10787 @cindex no debug info variables
10788 If you try to examine or use the value of a (global) variable for
10789 which @value{GDBN} has no type information, e.g., because the program
10790 includes no debug information, @value{GDBN} displays an error message.
10791 @xref{Symbols, unknown type}, for more about unknown types. If you
10792 cast the variable to its declared type, @value{GDBN} gets the
10793 variable's value using the cast-to type as the variable's type. For
10794 example, in a C program:
10797 (@value{GDBP}) p var
10798 'var' has unknown type; cast it to its declared type
10799 (@value{GDBP}) p (float) var
10803 If you append @kbd{@@entry} string to a function parameter name you get its
10804 value at the time the function got called. If the value is not available an
10805 error message is printed. Entry values are available only with some compilers.
10806 Entry values are normally also printed at the function parameter list according
10807 to @ref{set print entry-values}.
10810 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10816 (gdb) print i@@entry
10820 Strings are identified as arrays of @code{char} values without specified
10821 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10822 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10823 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10824 defines literal string type @code{"char"} as @code{char} without a sign.
10829 signed char var1[] = "A";
10832 You get during debugging
10837 $2 = @{65 'A', 0 '\0'@}
10841 @section Artificial Arrays
10843 @cindex artificial array
10845 @kindex @@@r{, referencing memory as an array}
10846 It is often useful to print out several successive objects of the
10847 same type in memory; a section of an array, or an array of
10848 dynamically determined size for which only a pointer exists in the
10851 You can do this by referring to a contiguous span of memory as an
10852 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10853 operand of @samp{@@} should be the first element of the desired array
10854 and be an individual object. The right operand should be the desired length
10855 of the array. The result is an array value whose elements are all of
10856 the type of the left argument. The first element is actually the left
10857 argument; the second element comes from bytes of memory immediately
10858 following those that hold the first element, and so on. Here is an
10859 example. If a program says
10862 int *array = (int *) malloc (len * sizeof (int));
10866 you can print the contents of @code{array} with
10872 The left operand of @samp{@@} must reside in memory. Array values made
10873 with @samp{@@} in this way behave just like other arrays in terms of
10874 subscripting, and are coerced to pointers when used in expressions.
10875 Artificial arrays most often appear in expressions via the value history
10876 (@pxref{Value History, ,Value History}), after printing one out.
10878 Another way to create an artificial array is to use a cast.
10879 This re-interprets a value as if it were an array.
10880 The value need not be in memory:
10882 (@value{GDBP}) p/x (short[2])0x12345678
10883 $1 = @{0x1234, 0x5678@}
10886 As a convenience, if you leave the array length out (as in
10887 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10888 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10890 (@value{GDBP}) p/x (short[])0x12345678
10891 $2 = @{0x1234, 0x5678@}
10894 Sometimes the artificial array mechanism is not quite enough; in
10895 moderately complex data structures, the elements of interest may not
10896 actually be adjacent---for example, if you are interested in the values
10897 of pointers in an array. One useful work-around in this situation is
10898 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10899 Variables}) as a counter in an expression that prints the first
10900 interesting value, and then repeat that expression via @key{RET}. For
10901 instance, suppose you have an array @code{dtab} of pointers to
10902 structures, and you are interested in the values of a field @code{fv}
10903 in each structure. Here is an example of what you might type:
10913 @node Output Formats
10914 @section Output Formats
10916 @cindex formatted output
10917 @cindex output formats
10918 By default, @value{GDBN} prints a value according to its data type. Sometimes
10919 this is not what you want. For example, you might want to print a number
10920 in hex, or a pointer in decimal. Or you might want to view data in memory
10921 at a certain address as a character string or as an instruction. To do
10922 these things, specify an @dfn{output format} when you print a value.
10924 The simplest use of output formats is to say how to print a value
10925 already computed. This is done by starting the arguments of the
10926 @code{print} command with a slash and a format letter. The format
10927 letters supported are:
10931 Print the binary representation of the value in hexadecimal.
10934 Print the binary representation of the value in decimal.
10937 Print the binary representation of the value as an decimal, as if it
10941 Print the binary representation of the value in octal.
10944 Print the binary representation of the value in binary. The letter
10945 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
10946 because these format letters are also used with the @code{x} command,
10947 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
10951 @cindex unknown address, locating
10952 @cindex locate address
10953 Print as an address, both absolute in hexadecimal and as an offset from
10954 the nearest preceding symbol. You can use this format used to discover
10955 where (in what function) an unknown address is located:
10958 (@value{GDBP}) p/a 0x54320
10959 $3 = 0x54320 <_initialize_vx+396>
10963 The command @code{info symbol 0x54320} yields similar results.
10964 @xref{Symbols, info symbol}.
10967 Cast the value to an integer (unlike other formats, this does not just
10968 reinterpret the underlying bits) and print it as a character constant.
10969 This prints both the numerical value and its character representation.
10970 The character representation is replaced with the octal escape
10971 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
10973 Without this format, @value{GDBN} displays @code{char},
10974 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10975 constants. Single-byte members of vectors are displayed as integer
10979 Regard the bits of the value as a floating point number and print
10980 using typical floating point syntax.
10983 @cindex printing strings
10984 @cindex printing byte arrays
10985 Regard as a string, if possible. With this format, pointers to single-byte
10986 data are displayed as null-terminated strings and arrays of single-byte data
10987 are displayed as fixed-length strings. Other values are displayed in their
10990 Without this format, @value{GDBN} displays pointers to and arrays of
10991 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10992 strings. Single-byte members of a vector are displayed as an integer
10996 Like @samp{x} formatting, the value is treated as an integer and
10997 printed as hexadecimal, but leading zeros are printed to pad the value
10998 to the size of the integer type.
11001 @cindex raw printing
11002 Print using the @samp{raw} formatting. By default, @value{GDBN} will
11003 use a Python-based pretty-printer, if one is available (@pxref{Pretty
11004 Printing}). This typically results in a higher-level display of the
11005 value's contents. The @samp{r} format bypasses any Python
11006 pretty-printer which might exist.
11009 For example, to print the program counter in hex (@pxref{Registers}), type
11016 Note that no space is required before the slash; this is because command
11017 names in @value{GDBN} cannot contain a slash.
11019 To reprint the last value in the value history with a different format,
11020 you can use the @code{print} command with just a format and no
11021 expression. For example, @samp{p/x} reprints the last value in hex.
11024 @section Examining Memory
11026 You can use the command @code{x} (for ``examine'') to examine memory in
11027 any of several formats, independently of your program's data types.
11029 @cindex examining memory
11031 @kindex x @r{(examine memory)}
11032 @item x/@var{nfu} @var{addr}
11033 @itemx x @var{addr}
11035 Use the @code{x} command to examine memory.
11038 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11039 much memory to display and how to format it; @var{addr} is an
11040 expression giving the address where you want to start displaying memory.
11041 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11042 Several commands set convenient defaults for @var{addr}.
11045 @item @var{n}, the repeat count
11046 The repeat count is a decimal integer; the default is 1. It specifies
11047 how much memory (counting by units @var{u}) to display. If a negative
11048 number is specified, memory is examined backward from @var{addr}.
11049 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11052 @item @var{f}, the display format
11053 The display format is one of the formats used by @code{print}
11054 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11055 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11056 @samp{m} (for displaying memory tags).
11057 The default is @samp{x} (hexadecimal) initially. The default changes
11058 each time you use either @code{x} or @code{print}.
11060 @item @var{u}, the unit size
11061 The unit size is any of
11067 Halfwords (two bytes).
11069 Words (four bytes). This is the initial default.
11071 Giant words (eight bytes).
11074 Each time you specify a unit size with @code{x}, that size becomes the
11075 default unit the next time you use @code{x}. For the @samp{i} format,
11076 the unit size is ignored and is normally not written. For the @samp{s} format,
11077 the unit size defaults to @samp{b}, unless it is explicitly given.
11078 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11079 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11080 Note that the results depend on the programming language of the
11081 current compilation unit. If the language is C, the @samp{s}
11082 modifier will use the UTF-16 encoding while @samp{w} will use
11083 UTF-32. The encoding is set by the programming language and cannot
11086 @item @var{addr}, starting display address
11087 @var{addr} is the address where you want @value{GDBN} to begin displaying
11088 memory. The expression need not have a pointer value (though it may);
11089 it is always interpreted as an integer address of a byte of memory.
11090 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11091 @var{addr} is usually just after the last address examined---but several
11092 other commands also set the default address: @code{info breakpoints} (to
11093 the address of the last breakpoint listed), @code{info line} (to the
11094 starting address of a line), and @code{print} (if you use it to display
11095 a value from memory).
11098 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11099 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11100 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11101 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11102 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11104 You can also specify a negative repeat count to examine memory backward
11105 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11106 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11108 Since the letters indicating unit sizes are all distinct from the
11109 letters specifying output formats, you do not have to remember whether
11110 unit size or format comes first; either order works. The output
11111 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11112 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11114 Even though the unit size @var{u} is ignored for the formats @samp{s}
11115 and @samp{i}, you might still want to use a count @var{n}; for example,
11116 @samp{3i} specifies that you want to see three machine instructions,
11117 including any operands. For convenience, especially when used with
11118 the @code{display} command, the @samp{i} format also prints branch delay
11119 slot instructions, if any, beyond the count specified, which immediately
11120 follow the last instruction that is within the count. The command
11121 @code{disassemble} gives an alternative way of inspecting machine
11122 instructions; see @ref{Machine Code,,Source and Machine Code}.
11124 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11125 the command displays null-terminated strings or instructions before the given
11126 address as many as the absolute value of the given number. For the @samp{i}
11127 format, we use line number information in the debug info to accurately locate
11128 instruction boundaries while disassembling backward. If line info is not
11129 available, the command stops examining memory with an error message.
11131 All the defaults for the arguments to @code{x} are designed to make it
11132 easy to continue scanning memory with minimal specifications each time
11133 you use @code{x}. For example, after you have inspected three machine
11134 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11135 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11136 the repeat count @var{n} is used again; the other arguments default as
11137 for successive uses of @code{x}.
11139 When examining machine instructions, the instruction at current program
11140 counter is shown with a @code{=>} marker. For example:
11143 (@value{GDBP}) x/5i $pc-6
11144 0x804837f <main+11>: mov %esp,%ebp
11145 0x8048381 <main+13>: push %ecx
11146 0x8048382 <main+14>: sub $0x4,%esp
11147 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11148 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11151 If the architecture supports memory tagging, the tags can be displayed by
11152 using @samp{m}. @xref{Memory Tagging}.
11154 The information will be displayed once per granule size
11155 (the amount of bytes a particular memory tag covers). For example, AArch64
11156 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11158 Due to the way @value{GDBN} prints information with the @code{x} command (not
11159 aligned to a particular boundary), the tag information will refer to the
11160 initial address displayed on a particular line. If a memory tag boundary
11161 is crossed in the middle of a line displayed by the @code{x} command, it
11162 will be displayed on the next line.
11164 The @samp{m} format doesn't affect any other specified formats that were
11165 passed to the @code{x} command.
11167 @cindex @code{$_}, @code{$__}, and value history
11168 The addresses and contents printed by the @code{x} command are not saved
11169 in the value history because there is often too much of them and they
11170 would get in the way. Instead, @value{GDBN} makes these values available for
11171 subsequent use in expressions as values of the convenience variables
11172 @code{$_} and @code{$__}. After an @code{x} command, the last address
11173 examined is available for use in expressions in the convenience variable
11174 @code{$_}. The contents of that address, as examined, are available in
11175 the convenience variable @code{$__}.
11177 If the @code{x} command has a repeat count, the address and contents saved
11178 are from the last memory unit printed; this is not the same as the last
11179 address printed if several units were printed on the last line of output.
11181 @anchor{addressable memory unit}
11182 @cindex addressable memory unit
11183 Most targets have an addressable memory unit size of 8 bits. This means
11184 that to each memory address are associated 8 bits of data. Some
11185 targets, however, have other addressable memory unit sizes.
11186 Within @value{GDBN} and this document, the term
11187 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11188 when explicitly referring to a chunk of data of that size. The word
11189 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11190 the addressable memory unit size of the target. For most systems,
11191 addressable memory unit is a synonym of byte.
11193 @cindex remote memory comparison
11194 @cindex target memory comparison
11195 @cindex verify remote memory image
11196 @cindex verify target memory image
11197 When you are debugging a program running on a remote target machine
11198 (@pxref{Remote Debugging}), you may wish to verify the program's image
11199 in the remote machine's memory against the executable file you
11200 downloaded to the target. Or, on any target, you may want to check
11201 whether the program has corrupted its own read-only sections. The
11202 @code{compare-sections} command is provided for such situations.
11205 @kindex compare-sections
11206 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11207 Compare the data of a loadable section @var{section-name} in the
11208 executable file of the program being debugged with the same section in
11209 the target machine's memory, and report any mismatches. With no
11210 arguments, compares all loadable sections. With an argument of
11211 @code{-r}, compares all loadable read-only sections.
11213 Note: for remote targets, this command can be accelerated if the
11214 target supports computing the CRC checksum of a block of memory
11215 (@pxref{qCRC packet}).
11218 @node Memory Tagging
11219 @section Memory Tagging
11221 Memory tagging is a memory protection technology that uses a pair of tags to
11222 validate memory accesses through pointers. The tags are integer values
11223 usually comprised of a few bits, depending on the architecture.
11225 There are two types of tags that are used in this setup: logical and
11226 allocation. A logical tag is stored in the pointers themselves, usually at the
11227 higher bits of the pointers. An allocation tag is the tag associated
11228 with particular ranges of memory in the physical address space, against which
11229 the logical tags from pointers are compared.
11231 The pointer tag (logical tag) must match the memory tag (allocation tag)
11232 for the memory access to be valid. If the logical tag does not match the
11233 allocation tag, that will raise a memory violation.
11235 Allocation tags cover multiple contiguous bytes of physical memory. This
11236 range of bytes is called a memory tag granule and is architecture-specific.
11237 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11238 tag spans 16 bytes of memory.
11240 If the underlying architecture supports memory tagging, like AArch64 MTE
11241 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11242 against memory allocation tags.
11244 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11245 display tag information when appropriate, and a command prefix of
11246 @code{memory-tag} gives access to the various memory tagging commands.
11248 The @code{memory-tag} commands are the following:
11251 @kindex memory-tag print-logical-tag
11252 @item memory-tag print-logical-tag @var{pointer_expression}
11253 Print the logical tag stored in @var{pointer_expression}.
11254 @kindex memory-tag with-logical-tag
11255 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11256 Print the pointer given by @var{pointer_expression}, augmented with a logical
11257 tag of @var{tag_bytes}.
11258 @kindex memory-tag print-allocation-tag
11259 @item memory-tag print-allocation-tag @var{address_expression}
11260 Print the allocation tag associated with the memory address given by
11261 @var{address_expression}.
11262 @kindex memory-tag setatag
11263 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11264 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11265 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11266 @kindex memory-tag check
11267 @item memory-tag check @var{pointer_expression}
11268 Check if the logical tag in the pointer given by @var{pointer_expression}
11269 matches the allocation tag for the memory referenced by the pointer.
11271 This essentially emulates the hardware validation that is done when tagged
11272 memory is accessed through a pointer, but does not cause a memory fault as
11273 it would during hardware validation.
11275 It can be used to inspect potential memory tagging violations in the running
11276 process, before any faults get triggered.
11280 @section Automatic Display
11281 @cindex automatic display
11282 @cindex display of expressions
11284 If you find that you want to print the value of an expression frequently
11285 (to see how it changes), you might want to add it to the @dfn{automatic
11286 display list} so that @value{GDBN} prints its value each time your program stops.
11287 Each expression added to the list is given a number to identify it;
11288 to remove an expression from the list, you specify that number.
11289 The automatic display looks like this:
11293 3: bar[5] = (struct hack *) 0x3804
11297 This display shows item numbers, expressions and their current values. As with
11298 displays you request manually using @code{x} or @code{print}, you can
11299 specify the output format you prefer; in fact, @code{display} decides
11300 whether to use @code{print} or @code{x} depending your format
11301 specification---it uses @code{x} if you specify either the @samp{i}
11302 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11306 @item display @var{expr}
11307 Add the expression @var{expr} to the list of expressions to display
11308 each time your program stops. @xref{Expressions, ,Expressions}.
11310 @code{display} does not repeat if you press @key{RET} again after using it.
11312 @item display/@var{fmt} @var{expr}
11313 For @var{fmt} specifying only a display format and not a size or
11314 count, add the expression @var{expr} to the auto-display list but
11315 arrange to display it each time in the specified format @var{fmt}.
11316 @xref{Output Formats,,Output Formats}.
11318 @item display/@var{fmt} @var{addr}
11319 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11320 number of units, add the expression @var{addr} as a memory address to
11321 be examined each time your program stops. Examining means in effect
11322 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11325 For example, @samp{display/i $pc} can be helpful, to see the machine
11326 instruction about to be executed each time execution stops (@samp{$pc}
11327 is a common name for the program counter; @pxref{Registers, ,Registers}).
11330 @kindex delete display
11332 @item undisplay @var{dnums}@dots{}
11333 @itemx delete display @var{dnums}@dots{}
11334 Remove items from the list of expressions to display. Specify the
11335 numbers of the displays that you want affected with the command
11336 argument @var{dnums}. It can be a single display number, one of the
11337 numbers shown in the first field of the @samp{info display} display;
11338 or it could be a range of display numbers, as in @code{2-4}.
11340 @code{undisplay} does not repeat if you press @key{RET} after using it.
11341 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11343 @kindex disable display
11344 @item disable display @var{dnums}@dots{}
11345 Disable the display of item numbers @var{dnums}. A disabled display
11346 item is not printed automatically, but is not forgotten. It may be
11347 enabled again later. Specify the numbers of the displays that you
11348 want affected with the command argument @var{dnums}. It can be a
11349 single display number, one of the numbers shown in the first field of
11350 the @samp{info display} display; or it could be a range of display
11351 numbers, as in @code{2-4}.
11353 @kindex enable display
11354 @item enable display @var{dnums}@dots{}
11355 Enable display of item numbers @var{dnums}. It becomes effective once
11356 again in auto display of its expression, until you specify otherwise.
11357 Specify the numbers of the displays that you want affected with the
11358 command argument @var{dnums}. It can be a single display number, one
11359 of the numbers shown in the first field of the @samp{info display}
11360 display; or it could be a range of display numbers, as in @code{2-4}.
11363 Display the current values of the expressions on the list, just as is
11364 done when your program stops.
11366 @kindex info display
11368 Print the list of expressions previously set up to display
11369 automatically, each one with its item number, but without showing the
11370 values. This includes disabled expressions, which are marked as such.
11371 It also includes expressions which would not be displayed right now
11372 because they refer to automatic variables not currently available.
11375 @cindex display disabled out of scope
11376 If a display expression refers to local variables, then it does not make
11377 sense outside the lexical context for which it was set up. Such an
11378 expression is disabled when execution enters a context where one of its
11379 variables is not defined. For example, if you give the command
11380 @code{display last_char} while inside a function with an argument
11381 @code{last_char}, @value{GDBN} displays this argument while your program
11382 continues to stop inside that function. When it stops elsewhere---where
11383 there is no variable @code{last_char}---the display is disabled
11384 automatically. The next time your program stops where @code{last_char}
11385 is meaningful, you can enable the display expression once again.
11387 @node Print Settings
11388 @section Print Settings
11390 @cindex format options
11391 @cindex print settings
11392 @value{GDBN} provides the following ways to control how arrays, structures,
11393 and symbols are printed.
11396 These settings are useful for debugging programs in any language:
11400 @anchor{set print address}
11401 @item set print address
11402 @itemx set print address on
11403 @cindex print/don't print memory addresses
11404 @value{GDBN} prints memory addresses showing the location of stack
11405 traces, structure values, pointer values, breakpoints, and so forth,
11406 even when it also displays the contents of those addresses. The default
11407 is @code{on}. For example, this is what a stack frame display looks like with
11408 @code{set print address on}:
11413 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11415 530 if (lquote != def_lquote)
11419 @item set print address off
11420 Do not print addresses when displaying their contents. For example,
11421 this is the same stack frame displayed with @code{set print address off}:
11425 (@value{GDBP}) set print addr off
11427 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11428 530 if (lquote != def_lquote)
11432 You can use @samp{set print address off} to eliminate all machine
11433 dependent displays from the @value{GDBN} interface. For example, with
11434 @code{print address off}, you should get the same text for backtraces on
11435 all machines---whether or not they involve pointer arguments.
11438 @item show print address
11439 Show whether or not addresses are to be printed.
11442 When @value{GDBN} prints a symbolic address, it normally prints the
11443 closest earlier symbol plus an offset. If that symbol does not uniquely
11444 identify the address (for example, it is a name whose scope is a single
11445 source file), you may need to clarify. One way to do this is with
11446 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11447 you can set @value{GDBN} to print the source file and line number when
11448 it prints a symbolic address:
11451 @item set print symbol-filename on
11452 @cindex source file and line of a symbol
11453 @cindex symbol, source file and line
11454 Tell @value{GDBN} to print the source file name and line number of a
11455 symbol in the symbolic form of an address.
11457 @item set print symbol-filename off
11458 Do not print source file name and line number of a symbol. This is the
11461 @item show print symbol-filename
11462 Show whether or not @value{GDBN} will print the source file name and
11463 line number of a symbol in the symbolic form of an address.
11466 Another situation where it is helpful to show symbol filenames and line
11467 numbers is when disassembling code; @value{GDBN} shows you the line
11468 number and source file that corresponds to each instruction.
11470 Also, you may wish to see the symbolic form only if the address being
11471 printed is reasonably close to the closest earlier symbol:
11474 @item set print max-symbolic-offset @var{max-offset}
11475 @itemx set print max-symbolic-offset unlimited
11476 @cindex maximum value for offset of closest symbol
11477 Tell @value{GDBN} to only display the symbolic form of an address if the
11478 offset between the closest earlier symbol and the address is less than
11479 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11480 to always print the symbolic form of an address if any symbol precedes
11481 it. Zero is equivalent to @code{unlimited}.
11483 @item show print max-symbolic-offset
11484 Ask how large the maximum offset is that @value{GDBN} prints in a
11488 @cindex wild pointer, interpreting
11489 @cindex pointer, finding referent
11490 If you have a pointer and you are not sure where it points, try
11491 @samp{set print symbol-filename on}. Then you can determine the name
11492 and source file location of the variable where it points, using
11493 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11494 For example, here @value{GDBN} shows that a variable @code{ptt} points
11495 at another variable @code{t}, defined in @file{hi2.c}:
11498 (@value{GDBP}) set print symbol-filename on
11499 (@value{GDBP}) p/a ptt
11500 $4 = 0xe008 <t in hi2.c>
11504 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11505 does not show the symbol name and filename of the referent, even with
11506 the appropriate @code{set print} options turned on.
11509 You can also enable @samp{/a}-like formatting all the time using
11510 @samp{set print symbol on}:
11512 @anchor{set print symbol}
11514 @item set print symbol on
11515 Tell @value{GDBN} to print the symbol corresponding to an address, if
11518 @item set print symbol off
11519 Tell @value{GDBN} not to print the symbol corresponding to an
11520 address. In this mode, @value{GDBN} will still print the symbol
11521 corresponding to pointers to functions. This is the default.
11523 @item show print symbol
11524 Show whether @value{GDBN} will display the symbol corresponding to an
11528 Other settings control how different kinds of objects are printed:
11531 @anchor{set print array}
11532 @item set print array
11533 @itemx set print array on
11534 @cindex pretty print arrays
11535 Pretty print arrays. This format is more convenient to read,
11536 but uses more space. The default is off.
11538 @item set print array off
11539 Return to compressed format for arrays.
11541 @item show print array
11542 Show whether compressed or pretty format is selected for displaying
11545 @cindex print array indexes
11546 @anchor{set print array-indexes}
11547 @item set print array-indexes
11548 @itemx set print array-indexes on
11549 Print the index of each element when displaying arrays. May be more
11550 convenient to locate a given element in the array or quickly find the
11551 index of a given element in that printed array. The default is off.
11553 @item set print array-indexes off
11554 Stop printing element indexes when displaying arrays.
11556 @item show print array-indexes
11557 Show whether the index of each element is printed when displaying
11560 @anchor{set print nibbles}
11561 @item set print nibbles
11562 @itemx set print nibbles on
11563 @cindex print binary values in groups of four bits
11564 Print binary values in groups of four bits, known as @dfn{nibbles},
11565 when using the print command of @value{GDBN} with the option @samp{/t}.
11566 For example, this is what it looks like with @code{set print nibbles on}:
11570 (@value{GDBP}) print val_flags
11572 (@value{GDBP}) print/t val_flags
11573 $2 = 0100 1100 1110
11577 @item set print nibbles off
11578 Don't printing binary values in groups. This is the default.
11580 @item show print nibbles
11581 Show whether to print binary values in groups of four bits.
11583 @anchor{set print elements}
11584 @item set print elements @var{number-of-elements}
11585 @itemx set print elements unlimited
11586 @cindex number of array elements to print
11587 @cindex limit on number of printed array elements
11588 Set a limit on how many elements of an array @value{GDBN} will print.
11589 If @value{GDBN} is printing a large array, it stops printing after it has
11590 printed the number of elements set by the @code{set print elements} command.
11591 This limit also applies to the display of strings.
11592 When @value{GDBN} starts, this limit is set to 200.
11593 Setting @var{number-of-elements} to @code{unlimited} or zero means
11594 that the number of elements to print is unlimited.
11596 @item show print elements
11597 Display the number of elements of a large array that @value{GDBN} will print.
11599 @anchor{set print frame-arguments}
11600 @item set print frame-arguments @var{value}
11601 @kindex set print frame-arguments
11602 @cindex printing frame argument values
11603 @cindex print all frame argument values
11604 @cindex print frame argument values for scalars only
11605 @cindex do not print frame arguments
11606 This command allows to control how the values of arguments are printed
11607 when the debugger prints a frame (@pxref{Frames}). The possible
11612 The values of all arguments are printed.
11615 Print the value of an argument only if it is a scalar. The value of more
11616 complex arguments such as arrays, structures, unions, etc, is replaced
11617 by @code{@dots{}}. This is the default. Here is an example where
11618 only scalar arguments are shown:
11621 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11626 None of the argument values are printed. Instead, the value of each argument
11627 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11630 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11635 Only the presence of arguments is indicated by @code{@dots{}}.
11636 The @code{@dots{}} are not printed for function without any arguments.
11637 None of the argument names and values are printed.
11638 In this case, the example above now becomes:
11641 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11646 By default, only scalar arguments are printed. This command can be used
11647 to configure the debugger to print the value of all arguments, regardless
11648 of their type. However, it is often advantageous to not print the value
11649 of more complex parameters. For instance, it reduces the amount of
11650 information printed in each frame, making the backtrace more readable.
11651 Also, it improves performance when displaying Ada frames, because
11652 the computation of large arguments can sometimes be CPU-intensive,
11653 especially in large applications. Setting @code{print frame-arguments}
11654 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11655 this computation, thus speeding up the display of each Ada frame.
11657 @item show print frame-arguments
11658 Show how the value of arguments should be displayed when printing a frame.
11660 @anchor{set print raw-frame-arguments}
11661 @item set print raw-frame-arguments on
11662 Print frame arguments in raw, non pretty-printed, form.
11664 @item set print raw-frame-arguments off
11665 Print frame arguments in pretty-printed form, if there is a pretty-printer
11666 for the value (@pxref{Pretty Printing}),
11667 otherwise print the value in raw form.
11668 This is the default.
11670 @item show print raw-frame-arguments
11671 Show whether to print frame arguments in raw form.
11673 @anchor{set print entry-values}
11674 @item set print entry-values @var{value}
11675 @kindex set print entry-values
11676 Set printing of frame argument values at function entry. In some cases
11677 @value{GDBN} can determine the value of function argument which was passed by
11678 the function caller, even if the value was modified inside the called function
11679 and therefore is different. With optimized code, the current value could be
11680 unavailable, but the entry value may still be known.
11682 The default value is @code{default} (see below for its description). Older
11683 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11684 this feature will behave in the @code{default} setting the same way as with the
11687 This functionality is currently supported only by DWARF 2 debugging format and
11688 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11689 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11692 The @var{value} parameter can be one of the following:
11696 Print only actual parameter values, never print values from function entry
11700 #0 different (val=6)
11701 #0 lost (val=<optimized out>)
11703 #0 invalid (val=<optimized out>)
11707 Print only parameter values from function entry point. The actual parameter
11708 values are never printed.
11710 #0 equal (val@@entry=5)
11711 #0 different (val@@entry=5)
11712 #0 lost (val@@entry=5)
11713 #0 born (val@@entry=<optimized out>)
11714 #0 invalid (val@@entry=<optimized out>)
11718 Print only parameter values from function entry point. If value from function
11719 entry point is not known while the actual value is known, print the actual
11720 value for such parameter.
11722 #0 equal (val@@entry=5)
11723 #0 different (val@@entry=5)
11724 #0 lost (val@@entry=5)
11726 #0 invalid (val@@entry=<optimized out>)
11730 Print actual parameter values. If actual parameter value is not known while
11731 value from function entry point is known, print the entry point value for such
11735 #0 different (val=6)
11736 #0 lost (val@@entry=5)
11738 #0 invalid (val=<optimized out>)
11742 Always print both the actual parameter value and its value from function entry
11743 point, even if values of one or both are not available due to compiler
11746 #0 equal (val=5, val@@entry=5)
11747 #0 different (val=6, val@@entry=5)
11748 #0 lost (val=<optimized out>, val@@entry=5)
11749 #0 born (val=10, val@@entry=<optimized out>)
11750 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11754 Print the actual parameter value if it is known and also its value from
11755 function entry point if it is known. If neither is known, print for the actual
11756 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11757 values are known and identical, print the shortened
11758 @code{param=param@@entry=VALUE} notation.
11760 #0 equal (val=val@@entry=5)
11761 #0 different (val=6, val@@entry=5)
11762 #0 lost (val@@entry=5)
11764 #0 invalid (val=<optimized out>)
11768 Always print the actual parameter value. Print also its value from function
11769 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11770 if both values are known and identical, print the shortened
11771 @code{param=param@@entry=VALUE} notation.
11773 #0 equal (val=val@@entry=5)
11774 #0 different (val=6, val@@entry=5)
11775 #0 lost (val=<optimized out>, val@@entry=5)
11777 #0 invalid (val=<optimized out>)
11781 For analysis messages on possible failures of frame argument values at function
11782 entry resolution see @ref{set debug entry-values}.
11784 @item show print entry-values
11785 Show the method being used for printing of frame argument values at function
11788 @anchor{set print frame-info}
11789 @item set print frame-info @var{value}
11790 @kindex set print frame-info
11791 @cindex printing frame information
11792 @cindex frame information, printing
11793 This command allows to control the information printed when
11794 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11795 for a general explanation about frames and frame information.
11796 Note that some other settings (such as @code{set print frame-arguments}
11797 and @code{set print address}) are also influencing if and how some frame
11798 information is displayed. In particular, the frame program counter is never
11799 printed if @code{set print address} is off.
11801 The possible values for @code{set print frame-info} are:
11803 @item short-location
11804 Print the frame level, the program counter (if not at the
11805 beginning of the location source line), the function, the function
11808 Same as @code{short-location} but also print the source file and source line
11810 @item location-and-address
11811 Same as @code{location} but print the program counter even if located at the
11812 beginning of the location source line.
11814 Print the program counter (if not at the beginning of the location
11815 source line), the line number and the source line.
11816 @item source-and-location
11817 Print what @code{location} and @code{source-line} are printing.
11819 The information printed for a frame is decided automatically
11820 by the @value{GDBN} command that prints a frame.
11821 For example, @code{frame} prints the information printed by
11822 @code{source-and-location} while @code{stepi} will switch between
11823 @code{source-line} and @code{source-and-location} depending on the program
11825 The default value is @code{auto}.
11828 @anchor{set print repeats}
11829 @item set print repeats @var{number-of-repeats}
11830 @itemx set print repeats unlimited
11831 @cindex repeated array elements
11832 Set the threshold for suppressing display of repeated array
11833 elements. When the number of consecutive identical elements of an
11834 array exceeds the threshold, @value{GDBN} prints the string
11835 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11836 identical repetitions, instead of displaying the identical elements
11837 themselves. Setting the threshold to @code{unlimited} or zero will
11838 cause all elements to be individually printed. The default threshold
11841 @item show print repeats
11842 Display the current threshold for printing repeated identical
11845 @anchor{set print max-depth}
11846 @item set print max-depth @var{depth}
11847 @item set print max-depth unlimited
11848 @cindex printing nested structures
11849 Set the threshold after which nested structures are replaced with
11850 ellipsis, this can make visualising deeply nested structures easier.
11852 For example, given this C code
11855 typedef struct s1 @{ int a; @} s1;
11856 typedef struct s2 @{ s1 b; @} s2;
11857 typedef struct s3 @{ s2 c; @} s3;
11858 typedef struct s4 @{ s3 d; @} s4;
11860 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11863 The following table shows how different values of @var{depth} will
11864 effect how @code{var} is printed by @value{GDBN}:
11866 @multitable @columnfractions .3 .7
11867 @headitem @var{depth} setting @tab Result of @samp{p var}
11869 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11871 @tab @code{$1 = @{...@}}
11873 @tab @code{$1 = @{d = @{...@}@}}
11875 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11877 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11879 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11882 To see the contents of structures that have been hidden the user can
11883 either increase the print max-depth, or they can print the elements of
11884 the structure that are visible, for example
11887 (gdb) set print max-depth 2
11889 $1 = @{d = @{c = @{...@}@}@}
11891 $2 = @{c = @{b = @{...@}@}@}
11893 $3 = @{b = @{a = 3@}@}
11896 The pattern used to replace nested structures varies based on
11897 language, for most languages @code{@{...@}} is used, but Fortran uses
11900 @item show print max-depth
11901 Display the current threshold after which nested structures are
11902 replaces with ellipsis.
11904 @anchor{set print memory-tag-violations}
11905 @cindex printing memory tag violation information
11906 @item set print memory-tag-violations
11907 @itemx set print memory-tag-violations on
11908 Cause @value{GDBN} to display additional information about memory tag violations
11909 when printing pointers and addresses.
11911 @item set print memory-tag-violations off
11912 Stop printing memory tag violation information.
11914 @item show print memory-tag-violations
11915 Show whether memory tag violation information is displayed when printing
11916 pointers and addresses.
11918 @anchor{set print null-stop}
11919 @item set print null-stop
11920 @cindex @sc{null} elements in arrays
11921 Cause @value{GDBN} to stop printing the characters of an array when the first
11922 @sc{null} is encountered. This is useful when large arrays actually
11923 contain only short strings.
11924 The default is off.
11926 @item show print null-stop
11927 Show whether @value{GDBN} stops printing an array on the first
11928 @sc{null} character.
11930 @anchor{set print pretty}
11931 @item set print pretty on
11932 @cindex print structures in indented form
11933 @cindex indentation in structure display
11934 Cause @value{GDBN} to print structures in an indented format with one member
11935 per line, like this:
11950 @item set print pretty off
11951 Cause @value{GDBN} to print structures in a compact format, like this:
11955 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11956 meat = 0x54 "Pork"@}
11961 This is the default format.
11963 @item show print pretty
11964 Show which format @value{GDBN} is using to print structures.
11966 @anchor{set print raw-values}
11967 @item set print raw-values on
11968 Print values in raw form, without applying the pretty
11969 printers for the value.
11971 @item set print raw-values off
11972 Print values in pretty-printed form, if there is a pretty-printer
11973 for the value (@pxref{Pretty Printing}),
11974 otherwise print the value in raw form.
11976 The default setting is ``off''.
11978 @item show print raw-values
11979 Show whether to print values in raw form.
11981 @item set print sevenbit-strings on
11982 @cindex eight-bit characters in strings
11983 @cindex octal escapes in strings
11984 Print using only seven-bit characters; if this option is set,
11985 @value{GDBN} displays any eight-bit characters (in strings or
11986 character values) using the notation @code{\}@var{nnn}. This setting is
11987 best if you are working in English (@sc{ascii}) and you use the
11988 high-order bit of characters as a marker or ``meta'' bit.
11990 @item set print sevenbit-strings off
11991 Print full eight-bit characters. This allows the use of more
11992 international character sets, and is the default.
11994 @item show print sevenbit-strings
11995 Show whether or not @value{GDBN} is printing only seven-bit characters.
11997 @anchor{set print union}
11998 @item set print union on
11999 @cindex unions in structures, printing
12000 Tell @value{GDBN} to print unions which are contained in structures
12001 and other unions. This is the default setting.
12003 @item set print union off
12004 Tell @value{GDBN} not to print unions which are contained in
12005 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
12008 @item show print union
12009 Ask @value{GDBN} whether or not it will print unions which are contained in
12010 structures and other unions.
12012 For example, given the declarations
12015 typedef enum @{Tree, Bug@} Species;
12016 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12017 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12028 struct thing foo = @{Tree, @{Acorn@}@};
12032 with @code{set print union on} in effect @samp{p foo} would print
12035 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12039 and with @code{set print union off} in effect it would print
12042 $1 = @{it = Tree, form = @{...@}@}
12046 @code{set print union} affects programs written in C-like languages
12052 These settings are of interest when debugging C@t{++} programs:
12055 @cindex demangling C@t{++} names
12056 @item set print demangle
12057 @itemx set print demangle on
12058 Print C@t{++} names in their source form rather than in the encoded
12059 (``mangled'') form passed to the assembler and linker for type-safe
12060 linkage. The default is on.
12062 @item show print demangle
12063 Show whether C@t{++} names are printed in mangled or demangled form.
12065 @item set print asm-demangle
12066 @itemx set print asm-demangle on
12067 Print C@t{++} names in their source form rather than their mangled form, even
12068 in assembler code printouts such as instruction disassemblies.
12069 The default is off.
12071 @item show print asm-demangle
12072 Show whether C@t{++} names in assembly listings are printed in mangled
12075 @cindex C@t{++} symbol decoding style
12076 @cindex symbol decoding style, C@t{++}
12077 @kindex set demangle-style
12078 @item set demangle-style @var{style}
12079 Choose among several encoding schemes used by different compilers to represent
12080 C@t{++} names. If you omit @var{style}, you will see a list of possible
12081 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12082 decoding style by inspecting your program.
12084 @item show demangle-style
12085 Display the encoding style currently in use for decoding C@t{++} symbols.
12087 @anchor{set print object}
12088 @item set print object
12089 @itemx set print object on
12090 @cindex derived type of an object, printing
12091 @cindex display derived types
12092 When displaying a pointer to an object, identify the @emph{actual}
12093 (derived) type of the object rather than the @emph{declared} type, using
12094 the virtual function table. Note that the virtual function table is
12095 required---this feature can only work for objects that have run-time
12096 type identification; a single virtual method in the object's declared
12097 type is sufficient. Note that this setting is also taken into account when
12098 working with variable objects via MI (@pxref{GDB/MI}).
12100 @item set print object off
12101 Display only the declared type of objects, without reference to the
12102 virtual function table. This is the default setting.
12104 @item show print object
12105 Show whether actual, or declared, object types are displayed.
12107 @anchor{set print static-members}
12108 @item set print static-members
12109 @itemx set print static-members on
12110 @cindex static members of C@t{++} objects
12111 Print static members when displaying a C@t{++} object. The default is on.
12113 @item set print static-members off
12114 Do not print static members when displaying a C@t{++} object.
12116 @item show print static-members
12117 Show whether C@t{++} static members are printed or not.
12119 @item set print pascal_static-members
12120 @itemx set print pascal_static-members on
12121 @cindex static members of Pascal objects
12122 @cindex Pascal objects, static members display
12123 Print static members when displaying a Pascal object. The default is on.
12125 @item set print pascal_static-members off
12126 Do not print static members when displaying a Pascal object.
12128 @item show print pascal_static-members
12129 Show whether Pascal static members are printed or not.
12131 @c These don't work with HP ANSI C++ yet.
12132 @anchor{set print vtbl}
12133 @item set print vtbl
12134 @itemx set print vtbl on
12135 @cindex pretty print C@t{++} virtual function tables
12136 @cindex virtual functions (C@t{++}) display
12137 @cindex VTBL display
12138 Pretty print C@t{++} virtual function tables. The default is off.
12139 (The @code{vtbl} commands do not work on programs compiled with the HP
12140 ANSI C@t{++} compiler (@code{aCC}).)
12142 @item set print vtbl off
12143 Do not pretty print C@t{++} virtual function tables.
12145 @item show print vtbl
12146 Show whether C@t{++} virtual function tables are pretty printed, or not.
12149 @node Pretty Printing
12150 @section Pretty Printing
12152 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12153 Python code. It greatly simplifies the display of complex objects. This
12154 mechanism works for both MI and the CLI.
12157 * Pretty-Printer Introduction:: Introduction to pretty-printers
12158 * Pretty-Printer Example:: An example pretty-printer
12159 * Pretty-Printer Commands:: Pretty-printer commands
12162 @node Pretty-Printer Introduction
12163 @subsection Pretty-Printer Introduction
12165 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12166 registered for the value. If there is then @value{GDBN} invokes the
12167 pretty-printer to print the value. Otherwise the value is printed normally.
12169 Pretty-printers are normally named. This makes them easy to manage.
12170 The @samp{info pretty-printer} command will list all the installed
12171 pretty-printers with their names.
12172 If a pretty-printer can handle multiple data types, then its
12173 @dfn{subprinters} are the printers for the individual data types.
12174 Each such subprinter has its own name.
12175 The format of the name is @var{printer-name};@var{subprinter-name}.
12177 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12178 Typically they are automatically loaded and registered when the corresponding
12179 debug information is loaded, thus making them available without having to
12180 do anything special.
12182 There are three places where a pretty-printer can be registered.
12186 Pretty-printers registered globally are available when debugging
12190 Pretty-printers registered with a program space are available only
12191 when debugging that program.
12192 @xref{Progspaces In Python}, for more details on program spaces in Python.
12195 Pretty-printers registered with an objfile are loaded and unloaded
12196 with the corresponding objfile (e.g., shared library).
12197 @xref{Objfiles In Python}, for more details on objfiles in Python.
12200 @xref{Selecting Pretty-Printers}, for further information on how
12201 pretty-printers are selected,
12203 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12206 @node Pretty-Printer Example
12207 @subsection Pretty-Printer Example
12209 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12212 (@value{GDBP}) print s
12214 static npos = 4294967295,
12216 <std::allocator<char>> = @{
12217 <__gnu_cxx::new_allocator<char>> = @{
12218 <No data fields>@}, <No data fields>
12220 members of std::basic_string<char, std::char_traits<char>,
12221 std::allocator<char> >::_Alloc_hider:
12222 _M_p = 0x804a014 "abcd"
12227 With a pretty-printer for @code{std::string} only the contents are printed:
12230 (@value{GDBP}) print s
12234 @node Pretty-Printer Commands
12235 @subsection Pretty-Printer Commands
12236 @cindex pretty-printer commands
12239 @kindex info pretty-printer
12240 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12241 Print the list of installed pretty-printers.
12242 This includes disabled pretty-printers, which are marked as such.
12244 @var{object-regexp} is a regular expression matching the objects
12245 whose pretty-printers to list.
12246 Objects can be @code{global}, the program space's file
12247 (@pxref{Progspaces In Python}),
12248 and the object files within that program space (@pxref{Objfiles In Python}).
12249 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12250 looks up a printer from these three objects.
12252 @var{name-regexp} is a regular expression matching the name of the printers
12255 @kindex disable pretty-printer
12256 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12257 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12258 A disabled pretty-printer is not forgotten, it may be enabled again later.
12260 @kindex enable pretty-printer
12261 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12262 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12267 Suppose we have three pretty-printers installed: one from library1.so
12268 named @code{foo} that prints objects of type @code{foo}, and
12269 another from library2.so named @code{bar} that prints two types of objects,
12270 @code{bar1} and @code{bar2}.
12274 (@value{GDBP}) info pretty-printer
12283 (@value{GDBP}) info pretty-printer library2
12290 (@value{GDBP}) disable pretty-printer library1
12292 2 of 3 printers enabled
12293 (@value{GDBP}) info pretty-printer
12302 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12304 1 of 3 printers enabled
12305 (@value{GDBP}) info pretty-printer library2
12312 (@value{GDBP}) disable pretty-printer library2 bar
12314 0 of 3 printers enabled
12315 (@value{GDBP}) info pretty-printer
12325 Note that for @code{bar} the entire printer can be disabled,
12326 as can each individual subprinter.
12328 Printing values and frame arguments is done by default using
12329 the enabled pretty printers.
12331 The print option @code{-raw-values} and @value{GDBN} setting
12332 @code{set print raw-values} (@pxref{set print raw-values}) can be
12333 used to print values without applying the enabled pretty printers.
12335 Similarly, the backtrace option @code{-raw-frame-arguments} and
12336 @value{GDBN} setting @code{set print raw-frame-arguments}
12337 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12338 enabled pretty printers when printing frame argument values.
12340 @node Value History
12341 @section Value History
12343 @cindex value history
12344 @cindex history of values printed by @value{GDBN}
12345 Values printed by the @code{print} command are saved in the @value{GDBN}
12346 @dfn{value history}. This allows you to refer to them in other expressions.
12347 Values are kept until the symbol table is re-read or discarded
12348 (for example with the @code{file} or @code{symbol-file} commands).
12349 When the symbol table changes, the value history is discarded,
12350 since the values may contain pointers back to the types defined in the
12355 @cindex history number
12356 The values printed are given @dfn{history numbers} by which you can
12357 refer to them. These are successive integers starting with one.
12358 @code{print} shows you the history number assigned to a value by
12359 printing @samp{$@var{num} = } before the value; here @var{num} is the
12362 To refer to any previous value, use @samp{$} followed by the value's
12363 history number. The way @code{print} labels its output is designed to
12364 remind you of this. Just @code{$} refers to the most recent value in
12365 the history, and @code{$$} refers to the value before that.
12366 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12367 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12368 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12370 For example, suppose you have just printed a pointer to a structure and
12371 want to see the contents of the structure. It suffices to type
12377 If you have a chain of structures where the component @code{next} points
12378 to the next one, you can print the contents of the next one with this:
12385 You can print successive links in the chain by repeating this
12386 command---which you can do by just typing @key{RET}.
12388 Note that the history records values, not expressions. If the value of
12389 @code{x} is 4 and you type these commands:
12397 then the value recorded in the value history by the @code{print} command
12398 remains 4 even though the value of @code{x} has changed.
12401 @kindex show values
12403 Print the last ten values in the value history, with their item numbers.
12404 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12405 values} does not change the history.
12407 @item show values @var{n}
12408 Print ten history values centered on history item number @var{n}.
12410 @item show values +
12411 Print ten history values just after the values last printed. If no more
12412 values are available, @code{show values +} produces no display.
12415 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12416 same effect as @samp{show values +}.
12418 @node Convenience Vars
12419 @section Convenience Variables
12421 @cindex convenience variables
12422 @cindex user-defined variables
12423 @value{GDBN} provides @dfn{convenience variables} that you can use within
12424 @value{GDBN} to hold on to a value and refer to it later. These variables
12425 exist entirely within @value{GDBN}; they are not part of your program, and
12426 setting a convenience variable has no direct effect on further execution
12427 of your program. That is why you can use them freely.
12429 Convenience variables are prefixed with @samp{$}. Any name preceded by
12430 @samp{$} can be used for a convenience variable, unless it is one of
12431 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12432 (Value history references, in contrast, are @emph{numbers} preceded
12433 by @samp{$}. @xref{Value History, ,Value History}.)
12435 You can save a value in a convenience variable with an assignment
12436 expression, just as you would set a variable in your program.
12440 set $foo = *object_ptr
12444 would save in @code{$foo} the value contained in the object pointed to by
12447 Using a convenience variable for the first time creates it, but its
12448 value is @code{void} until you assign a new value. You can alter the
12449 value with another assignment at any time.
12451 Convenience variables have no fixed types. You can assign a convenience
12452 variable any type of value, including structures and arrays, even if
12453 that variable already has a value of a different type. The convenience
12454 variable, when used as an expression, has the type of its current value.
12457 @kindex show convenience
12458 @cindex show all user variables and functions
12459 @item show convenience
12460 Print a list of convenience variables used so far, and their values,
12461 as well as a list of the convenience functions.
12462 Abbreviated @code{show conv}.
12464 @kindex init-if-undefined
12465 @cindex convenience variables, initializing
12466 @item init-if-undefined $@var{variable} = @var{expression}
12467 Set a convenience variable if it has not already been set. This is useful
12468 for user-defined commands that keep some state. It is similar, in concept,
12469 to using local static variables with initializers in C (except that
12470 convenience variables are global). It can also be used to allow users to
12471 override default values used in a command script.
12473 If the variable is already defined then the expression is not evaluated so
12474 any side-effects do not occur.
12477 One of the ways to use a convenience variable is as a counter to be
12478 incremented or a pointer to be advanced. For example, to print
12479 a field from successive elements of an array of structures:
12483 print bar[$i++]->contents
12487 Repeat that command by typing @key{RET}.
12489 Some convenience variables are created automatically by @value{GDBN} and given
12490 values likely to be useful.
12493 @vindex $_@r{, convenience variable}
12495 The variable @code{$_} is automatically set by the @code{x} command to
12496 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12497 commands which provide a default address for @code{x} to examine also
12498 set @code{$_} to that address; these commands include @code{info line}
12499 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12500 except when set by the @code{x} command, in which case it is a pointer
12501 to the type of @code{$__}.
12503 @vindex $__@r{, convenience variable}
12505 The variable @code{$__} is automatically set by the @code{x} command
12506 to the value found in the last address examined. Its type is chosen
12507 to match the format in which the data was printed.
12510 @vindex $_exitcode@r{, convenience variable}
12511 When the program being debugged terminates normally, @value{GDBN}
12512 automatically sets this variable to the exit code of the program, and
12513 resets @code{$_exitsignal} to @code{void}.
12516 @vindex $_exitsignal@r{, convenience variable}
12517 When the program being debugged dies due to an uncaught signal,
12518 @value{GDBN} automatically sets this variable to that signal's number,
12519 and resets @code{$_exitcode} to @code{void}.
12521 To distinguish between whether the program being debugged has exited
12522 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12523 @code{$_exitsignal} is not @code{void}), the convenience function
12524 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12525 Functions}). For example, considering the following source code:
12528 #include <signal.h>
12531 main (int argc, char *argv[])
12538 A valid way of telling whether the program being debugged has exited
12539 or signalled would be:
12542 (@value{GDBP}) define has_exited_or_signalled
12543 Type commands for definition of ``has_exited_or_signalled''.
12544 End with a line saying just ``end''.
12545 >if $_isvoid ($_exitsignal)
12546 >echo The program has exited\n
12548 >echo The program has signalled\n
12554 Program terminated with signal SIGALRM, Alarm clock.
12555 The program no longer exists.
12556 (@value{GDBP}) has_exited_or_signalled
12557 The program has signalled
12560 As can be seen, @value{GDBN} correctly informs that the program being
12561 debugged has signalled, since it calls @code{raise} and raises a
12562 @code{SIGALRM} signal. If the program being debugged had not called
12563 @code{raise}, then @value{GDBN} would report a normal exit:
12566 (@value{GDBP}) has_exited_or_signalled
12567 The program has exited
12571 The variable @code{$_exception} is set to the exception object being
12572 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12574 @item $_ada_exception
12575 The variable @code{$_ada_exception} is set to the address of the
12576 exception being caught or thrown at an Ada exception-related
12577 catchpoint. @xref{Set Catchpoints}.
12580 @itemx $_probe_arg0@dots{}$_probe_arg11
12581 Arguments to a static probe. @xref{Static Probe Points}.
12584 @vindex $_sdata@r{, inspect, convenience variable}
12585 The variable @code{$_sdata} contains extra collected static tracepoint
12586 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12587 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12588 if extra static tracepoint data has not been collected.
12591 @vindex $_siginfo@r{, convenience variable}
12592 The variable @code{$_siginfo} contains extra signal information
12593 (@pxref{extra signal information}). Note that @code{$_siginfo}
12594 could be empty, if the application has not yet received any signals.
12595 For example, it will be empty before you execute the @code{run} command.
12598 @vindex $_tlb@r{, convenience variable}
12599 The variable @code{$_tlb} is automatically set when debugging
12600 applications running on MS-Windows in native mode or connected to
12601 gdbserver that supports the @code{qGetTIBAddr} request.
12602 @xref{General Query Packets}.
12603 This variable contains the address of the thread information block.
12606 The number of the current inferior. @xref{Inferiors Connections and
12607 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12610 The thread number of the current thread. @xref{thread numbers}.
12613 The global number of the current thread. @xref{global thread numbers}.
12617 @vindex $_gdb_major@r{, convenience variable}
12618 @vindex $_gdb_minor@r{, convenience variable}
12619 The major and minor version numbers of the running @value{GDBN}.
12620 Development snapshots and pretest versions have their minor version
12621 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12622 the value 12 for @code{$_gdb_minor}. These variables allow you to
12623 write scripts that work with different versions of @value{GDBN}
12624 without errors caused by features unavailable in some of those
12627 @item $_shell_exitcode
12628 @itemx $_shell_exitsignal
12629 @vindex $_shell_exitcode@r{, convenience variable}
12630 @vindex $_shell_exitsignal@r{, convenience variable}
12631 @cindex shell command, exit code
12632 @cindex shell command, exit signal
12633 @cindex exit status of shell commands
12634 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12635 shell commands. When a launched command terminates, @value{GDBN}
12636 automatically maintains the variables @code{$_shell_exitcode}
12637 and @code{$_shell_exitsignal} according to the exit status of the last
12638 launched command. These variables are set and used similarly to
12639 the variables @code{$_exitcode} and @code{$_exitsignal}.
12643 @node Convenience Funs
12644 @section Convenience Functions
12646 @cindex convenience functions
12647 @value{GDBN} also supplies some @dfn{convenience functions}. These
12648 have a syntax similar to convenience variables. A convenience
12649 function can be used in an expression just like an ordinary function;
12650 however, a convenience function is implemented internally to
12653 These functions do not require @value{GDBN} to be configured with
12654 @code{Python} support, which means that they are always available.
12658 @item $_isvoid (@var{expr})
12659 @findex $_isvoid@r{, convenience function}
12660 Return one if the expression @var{expr} is @code{void}. Otherwise it
12663 A @code{void} expression is an expression where the type of the result
12664 is @code{void}. For example, you can examine a convenience variable
12665 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12669 (@value{GDBP}) print $_exitcode
12671 (@value{GDBP}) print $_isvoid ($_exitcode)
12674 Starting program: ./a.out
12675 [Inferior 1 (process 29572) exited normally]
12676 (@value{GDBP}) print $_exitcode
12678 (@value{GDBP}) print $_isvoid ($_exitcode)
12682 In the example above, we used @code{$_isvoid} to check whether
12683 @code{$_exitcode} is @code{void} before and after the execution of the
12684 program being debugged. Before the execution there is no exit code to
12685 be examined, therefore @code{$_exitcode} is @code{void}. After the
12686 execution the program being debugged returned zero, therefore
12687 @code{$_exitcode} is zero, which means that it is not @code{void}
12690 The @code{void} expression can also be a call of a function from the
12691 program being debugged. For example, given the following function:
12700 The result of calling it inside @value{GDBN} is @code{void}:
12703 (@value{GDBP}) print foo ()
12705 (@value{GDBP}) print $_isvoid (foo ())
12707 (@value{GDBP}) set $v = foo ()
12708 (@value{GDBP}) print $v
12710 (@value{GDBP}) print $_isvoid ($v)
12714 @item $_gdb_setting_str (@var{setting})
12715 @findex $_gdb_setting_str@r{, convenience function}
12716 Return the value of the @value{GDBN} @var{setting} as a string.
12717 @var{setting} is any setting that can be used in a @code{set} or
12718 @code{show} command (@pxref{Controlling GDB}).
12721 (@value{GDBP}) show print frame-arguments
12722 Printing of non-scalar frame arguments is "scalars".
12723 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12725 (@value{GDBP}) p $_gdb_setting_str("height")
12730 @item $_gdb_setting (@var{setting})
12731 @findex $_gdb_setting@r{, convenience function}
12732 Return the value of the @value{GDBN} @var{setting}.
12733 The type of the returned value depends on the setting.
12735 The value type for boolean and auto boolean settings is @code{int}.
12736 The boolean values @code{off} and @code{on} are converted to
12737 the integer values @code{0} and @code{1}. The value @code{auto} is
12738 converted to the value @code{-1}.
12740 The value type for integer settings is either @code{unsigned int}
12741 or @code{int}, depending on the setting.
12743 Some integer settings accept an @code{unlimited} value.
12744 Depending on the setting, the @code{set} command also accepts
12745 the value @code{0} or the value @code{@minus{}1} as a synonym for
12747 For example, @code{set height unlimited} is equivalent to
12748 @code{set height 0}.
12750 Some other settings that accept the @code{unlimited} value
12751 use the value @code{0} to literally mean zero.
12752 For example, @code{set history size 0} indicates to not
12753 record any @value{GDBN} commands in the command history.
12754 For such settings, @code{@minus{}1} is the synonym
12755 for @code{unlimited}.
12757 See the documentation of the corresponding @code{set} command for
12758 the numerical value equivalent to @code{unlimited}.
12760 The @code{$_gdb_setting} function converts the unlimited value
12761 to a @code{0} or a @code{@minus{}1} value according to what the
12762 @code{set} command uses.
12766 (@value{GDBP}) p $_gdb_setting_str("height")
12768 (@value{GDBP}) p $_gdb_setting("height")
12770 (@value{GDBP}) set height unlimited
12771 (@value{GDBP}) p $_gdb_setting_str("height")
12773 (@value{GDBP}) p $_gdb_setting("height")
12777 (@value{GDBP}) p $_gdb_setting_str("history size")
12779 (@value{GDBP}) p $_gdb_setting("history size")
12781 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12783 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12789 Other setting types (enum, filename, optional filename, string, string noescape)
12790 are returned as string values.
12793 @item $_gdb_maint_setting_str (@var{setting})
12794 @findex $_gdb_maint_setting_str@r{, convenience function}
12795 Like the @code{$_gdb_setting_str} function, but works with
12796 @code{maintenance set} variables.
12798 @item $_gdb_maint_setting (@var{setting})
12799 @findex $_gdb_maint_setting@r{, convenience function}
12800 Like the @code{$_gdb_setting} function, but works with
12801 @code{maintenance set} variables.
12805 The following functions require @value{GDBN} to be configured with
12806 @code{Python} support.
12810 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12811 @findex $_memeq@r{, convenience function}
12812 Returns one if the @var{length} bytes at the addresses given by
12813 @var{buf1} and @var{buf2} are equal.
12814 Otherwise it returns zero.
12816 @item $_regex(@var{str}, @var{regex})
12817 @findex $_regex@r{, convenience function}
12818 Returns one if the string @var{str} matches the regular expression
12819 @var{regex}. Otherwise it returns zero.
12820 The syntax of the regular expression is that specified by @code{Python}'s
12821 regular expression support.
12823 @item $_streq(@var{str1}, @var{str2})
12824 @findex $_streq@r{, convenience function}
12825 Returns one if the strings @var{str1} and @var{str2} are equal.
12826 Otherwise it returns zero.
12828 @item $_strlen(@var{str})
12829 @findex $_strlen@r{, convenience function}
12830 Returns the length of string @var{str}.
12832 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12833 @findex $_caller_is@r{, convenience function}
12834 Returns one if the calling function's name is equal to @var{name}.
12835 Otherwise it returns zero.
12837 If the optional argument @var{number_of_frames} is provided,
12838 it is the number of frames up in the stack to look.
12846 at testsuite/gdb.python/py-caller-is.c:21
12847 #1 0x00000000004005a0 in middle_func ()
12848 at testsuite/gdb.python/py-caller-is.c:27
12849 #2 0x00000000004005ab in top_func ()
12850 at testsuite/gdb.python/py-caller-is.c:33
12851 #3 0x00000000004005b6 in main ()
12852 at testsuite/gdb.python/py-caller-is.c:39
12853 (gdb) print $_caller_is ("middle_func")
12855 (gdb) print $_caller_is ("top_func", 2)
12859 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12860 @findex $_caller_matches@r{, convenience function}
12861 Returns one if the calling function's name matches the regular expression
12862 @var{regexp}. Otherwise it returns zero.
12864 If the optional argument @var{number_of_frames} is provided,
12865 it is the number of frames up in the stack to look.
12868 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12869 @findex $_any_caller_is@r{, convenience function}
12870 Returns one if any calling function's name is equal to @var{name}.
12871 Otherwise it returns zero.
12873 If the optional argument @var{number_of_frames} is provided,
12874 it is the number of frames up in the stack to look.
12877 This function differs from @code{$_caller_is} in that this function
12878 checks all stack frames from the immediate caller to the frame specified
12879 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12880 frame specified by @var{number_of_frames}.
12882 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12883 @findex $_any_caller_matches@r{, convenience function}
12884 Returns one if any calling function's name matches the regular expression
12885 @var{regexp}. Otherwise it returns zero.
12887 If the optional argument @var{number_of_frames} is provided,
12888 it is the number of frames up in the stack to look.
12891 This function differs from @code{$_caller_matches} in that this function
12892 checks all stack frames from the immediate caller to the frame specified
12893 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12894 frame specified by @var{number_of_frames}.
12896 @item $_as_string(@var{value})
12897 @findex $_as_string@r{, convenience function}
12898 Return the string representation of @var{value}.
12900 This function is useful to obtain the textual label (enumerator) of an
12901 enumeration value. For example, assuming the variable @var{node} is of
12902 an enumerated type:
12905 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12906 Visiting node of type NODE_INTEGER
12909 @item $_cimag(@var{value})
12910 @itemx $_creal(@var{value})
12911 @findex $_cimag@r{, convenience function}
12912 @findex $_creal@r{, convenience function}
12913 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12914 the complex number @var{value}.
12916 The type of the imaginary or real part depends on the type of the
12917 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12918 will return an imaginary part of type @code{float}.
12922 @value{GDBN} provides the ability to list and get help on
12923 convenience functions.
12926 @item help function
12927 @kindex help function
12928 @cindex show all convenience functions
12929 Print a list of all convenience functions.
12936 You can refer to machine register contents, in expressions, as variables
12937 with names starting with @samp{$}. The names of registers are different
12938 for each machine; use @code{info registers} to see the names used on
12942 @kindex info registers
12943 @item info registers
12944 Print the names and values of all registers except floating-point
12945 and vector registers (in the selected stack frame).
12947 @kindex info all-registers
12948 @cindex floating point registers
12949 @item info all-registers
12950 Print the names and values of all registers, including floating-point
12951 and vector registers (in the selected stack frame).
12953 @anchor{info_registers_reggroup}
12954 @item info registers @var{reggroup} @dots{}
12955 Print the name and value of the registers in each of the specified
12956 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12957 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12959 @item info registers @var{regname} @dots{}
12960 Print the @dfn{relativized} value of each specified register @var{regname}.
12961 As discussed in detail below, register values are normally relative to
12962 the selected stack frame. The @var{regname} may be any register name valid on
12963 the machine you are using, with or without the initial @samp{$}.
12966 @anchor{standard registers}
12967 @cindex stack pointer register
12968 @cindex program counter register
12969 @cindex process status register
12970 @cindex frame pointer register
12971 @cindex standard registers
12972 @value{GDBN} has four ``standard'' register names that are available (in
12973 expressions) on most machines---whenever they do not conflict with an
12974 architecture's canonical mnemonics for registers. The register names
12975 @code{$pc} and @code{$sp} are used for the program counter register and
12976 the stack pointer. @code{$fp} is used for a register that contains a
12977 pointer to the current stack frame, and @code{$ps} is used for a
12978 register that contains the processor status. For example,
12979 you could print the program counter in hex with
12986 or print the instruction to be executed next with
12993 or add four to the stack pointer@footnote{This is a way of removing
12994 one word from the stack, on machines where stacks grow downward in
12995 memory (most machines, nowadays). This assumes that the innermost
12996 stack frame is selected; setting @code{$sp} is not allowed when other
12997 stack frames are selected. To pop entire frames off the stack,
12998 regardless of machine architecture, use @code{return};
12999 see @ref{Returning, ,Returning from a Function}.} with
13005 Whenever possible, these four standard register names are available on
13006 your machine even though the machine has different canonical mnemonics,
13007 so long as there is no conflict. The @code{info registers} command
13008 shows the canonical names. For example, on the SPARC, @code{info
13009 registers} displays the processor status register as @code{$psr} but you
13010 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
13011 is an alias for the @sc{eflags} register.
13013 @value{GDBN} always considers the contents of an ordinary register as an
13014 integer when the register is examined in this way. Some machines have
13015 special registers which can hold nothing but floating point; these
13016 registers are considered to have floating point values. There is no way
13017 to refer to the contents of an ordinary register as floating point value
13018 (although you can @emph{print} it as a floating point value with
13019 @samp{print/f $@var{regname}}).
13021 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13022 means that the data format in which the register contents are saved by
13023 the operating system is not the same one that your program normally
13024 sees. For example, the registers of the 68881 floating point
13025 coprocessor are always saved in ``extended'' (raw) format, but all C
13026 programs expect to work with ``double'' (virtual) format. In such
13027 cases, @value{GDBN} normally works with the virtual format only (the format
13028 that makes sense for your program), but the @code{info registers} command
13029 prints the data in both formats.
13031 @cindex SSE registers (x86)
13032 @cindex MMX registers (x86)
13033 Some machines have special registers whose contents can be interpreted
13034 in several different ways. For example, modern x86-based machines
13035 have SSE and MMX registers that can hold several values packed
13036 together in several different formats. @value{GDBN} refers to such
13037 registers in @code{struct} notation:
13040 (@value{GDBP}) print $xmm1
13042 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13043 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13044 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13045 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13046 v4_int32 = @{0, 20657912, 11, 13@},
13047 v2_int64 = @{88725056443645952, 55834574859@},
13048 uint128 = 0x0000000d0000000b013b36f800000000
13053 To set values of such registers, you need to tell @value{GDBN} which
13054 view of the register you wish to change, as if you were assigning
13055 value to a @code{struct} member:
13058 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13061 Normally, register values are relative to the selected stack frame
13062 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13063 value that the register would contain if all stack frames farther in
13064 were exited and their saved registers restored. In order to see the
13065 true contents of hardware registers, you must select the innermost
13066 frame (with @samp{frame 0}).
13068 @cindex caller-saved registers
13069 @cindex call-clobbered registers
13070 @cindex volatile registers
13071 @cindex <not saved> values
13072 Usually ABIs reserve some registers as not needed to be saved by the
13073 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13074 registers). It may therefore not be possible for @value{GDBN} to know
13075 the value a register had before the call (in other words, in the outer
13076 frame), if the register value has since been changed by the callee.
13077 @value{GDBN} tries to deduce where the inner frame saved
13078 (``callee-saved'') registers, from the debug info, unwind info, or the
13079 machine code generated by your compiler. If some register is not
13080 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13081 its own knowledge of the ABI, or because the debug/unwind info
13082 explicitly says the register's value is undefined), @value{GDBN}
13083 displays @w{@samp{<not saved>}} as the register's value. With targets
13084 that @value{GDBN} has no knowledge of the register saving convention,
13085 if a register was not saved by the callee, then its value and location
13086 in the outer frame are assumed to be the same of the inner frame.
13087 This is usually harmless, because if the register is call-clobbered,
13088 the caller either does not care what is in the register after the
13089 call, or has code to restore the value that it does care about. Note,
13090 however, that if you change such a register in the outer frame, you
13091 may also be affecting the inner frame. Also, the more ``outer'' the
13092 frame is you're looking at, the more likely a call-clobbered
13093 register's value is to be wrong, in the sense that it doesn't actually
13094 represent the value the register had just before the call.
13096 @node Floating Point Hardware
13097 @section Floating Point Hardware
13098 @cindex floating point
13100 Depending on the configuration, @value{GDBN} may be able to give
13101 you more information about the status of the floating point hardware.
13106 Display hardware-dependent information about the floating
13107 point unit. The exact contents and layout vary depending on the
13108 floating point chip. Currently, @samp{info float} is supported on
13109 the ARM and x86 machines.
13113 @section Vector Unit
13114 @cindex vector unit
13116 Depending on the configuration, @value{GDBN} may be able to give you
13117 more information about the status of the vector unit.
13120 @kindex info vector
13122 Display information about the vector unit. The exact contents and
13123 layout vary depending on the hardware.
13126 @node OS Information
13127 @section Operating System Auxiliary Information
13128 @cindex OS information
13130 @value{GDBN} provides interfaces to useful OS facilities that can help
13131 you debug your program.
13133 @cindex auxiliary vector
13134 @cindex vector, auxiliary
13135 Some operating systems supply an @dfn{auxiliary vector} to programs at
13136 startup. This is akin to the arguments and environment that you
13137 specify for a program, but contains a system-dependent variety of
13138 binary values that tell system libraries important details about the
13139 hardware, operating system, and process. Each value's purpose is
13140 identified by an integer tag; the meanings are well-known but system-specific.
13141 Depending on the configuration and operating system facilities,
13142 @value{GDBN} may be able to show you this information. For remote
13143 targets, this functionality may further depend on the remote stub's
13144 support of the @samp{qXfer:auxv:read} packet, see
13145 @ref{qXfer auxiliary vector read}.
13150 Display the auxiliary vector of the inferior, which can be either a
13151 live process or a core dump file. @value{GDBN} prints each tag value
13152 numerically, and also shows names and text descriptions for recognized
13153 tags. Some values in the vector are numbers, some bit masks, and some
13154 pointers to strings or other data. @value{GDBN} displays each value in the
13155 most appropriate form for a recognized tag, and in hexadecimal for
13156 an unrecognized tag.
13159 On some targets, @value{GDBN} can access operating system-specific
13160 information and show it to you. The types of information available
13161 will differ depending on the type of operating system running on the
13162 target. The mechanism used to fetch the data is described in
13163 @ref{Operating System Information}. For remote targets, this
13164 functionality depends on the remote stub's support of the
13165 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13169 @item info os @var{infotype}
13171 Display OS information of the requested type.
13173 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13175 @anchor{linux info os infotypes}
13177 @kindex info os cpus
13179 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13180 the available fields from /proc/cpuinfo. For each supported architecture
13181 different fields are available. Two common entries are processor which gives
13182 CPU number and bogomips; a system constant that is calculated during
13183 kernel initialization.
13185 @kindex info os files
13187 Display the list of open file descriptors on the target. For each
13188 file descriptor, @value{GDBN} prints the identifier of the process
13189 owning the descriptor, the command of the owning process, the value
13190 of the descriptor, and the target of the descriptor.
13192 @kindex info os modules
13194 Display the list of all loaded kernel modules on the target. For each
13195 module, @value{GDBN} prints the module name, the size of the module in
13196 bytes, the number of times the module is used, the dependencies of the
13197 module, the status of the module, and the address of the loaded module
13200 @kindex info os msg
13202 Display the list of all System V message queues on the target. For each
13203 message queue, @value{GDBN} prints the message queue key, the message
13204 queue identifier, the access permissions, the current number of bytes
13205 on the queue, the current number of messages on the queue, the processes
13206 that last sent and received a message on the queue, the user and group
13207 of the owner and creator of the message queue, the times at which a
13208 message was last sent and received on the queue, and the time at which
13209 the message queue was last changed.
13211 @kindex info os processes
13213 Display the list of processes on the target. For each process,
13214 @value{GDBN} prints the process identifier, the name of the user, the
13215 command corresponding to the process, and the list of processor cores
13216 that the process is currently running on. (To understand what these
13217 properties mean, for this and the following info types, please consult
13218 the general @sc{gnu}/Linux documentation.)
13220 @kindex info os procgroups
13222 Display the list of process groups on the target. For each process,
13223 @value{GDBN} prints the identifier of the process group that it belongs
13224 to, the command corresponding to the process group leader, the process
13225 identifier, and the command line of the process. The list is sorted
13226 first by the process group identifier, then by the process identifier,
13227 so that processes belonging to the same process group are grouped together
13228 and the process group leader is listed first.
13230 @kindex info os semaphores
13232 Display the list of all System V semaphore sets on the target. For each
13233 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13234 set identifier, the access permissions, the number of semaphores in the
13235 set, the user and group of the owner and creator of the semaphore set,
13236 and the times at which the semaphore set was operated upon and changed.
13238 @kindex info os shm
13240 Display the list of all System V shared-memory regions on the target.
13241 For each shared-memory region, @value{GDBN} prints the region key,
13242 the shared-memory identifier, the access permissions, the size of the
13243 region, the process that created the region, the process that last
13244 attached to or detached from the region, the current number of live
13245 attaches to the region, and the times at which the region was last
13246 attached to, detach from, and changed.
13248 @kindex info os sockets
13250 Display the list of Internet-domain sockets on the target. For each
13251 socket, @value{GDBN} prints the address and port of the local and
13252 remote endpoints, the current state of the connection, the creator of
13253 the socket, the IP address family of the socket, and the type of the
13256 @kindex info os threads
13258 Display the list of threads running on the target. For each thread,
13259 @value{GDBN} prints the identifier of the process that the thread
13260 belongs to, the command of the process, the thread identifier, and the
13261 processor core that it is currently running on. The main thread of a
13262 process is not listed.
13266 If @var{infotype} is omitted, then list the possible values for
13267 @var{infotype} and the kind of OS information available for each
13268 @var{infotype}. If the target does not return a list of possible
13269 types, this command will report an error.
13272 @node Memory Region Attributes
13273 @section Memory Region Attributes
13274 @cindex memory region attributes
13276 @dfn{Memory region attributes} allow you to describe special handling
13277 required by regions of your target's memory. @value{GDBN} uses
13278 attributes to determine whether to allow certain types of memory
13279 accesses; whether to use specific width accesses; and whether to cache
13280 target memory. By default the description of memory regions is
13281 fetched from the target (if the current target supports this), but the
13282 user can override the fetched regions.
13284 Defined memory regions can be individually enabled and disabled. When a
13285 memory region is disabled, @value{GDBN} uses the default attributes when
13286 accessing memory in that region. Similarly, if no memory regions have
13287 been defined, @value{GDBN} uses the default attributes when accessing
13290 When a memory region is defined, it is given a number to identify it;
13291 to enable, disable, or remove a memory region, you specify that number.
13295 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13296 Define a memory region bounded by @var{lower} and @var{upper} with
13297 attributes @var{attributes}@dots{}, and add it to the list of regions
13298 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13299 case: it is treated as the target's maximum memory address.
13300 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13303 Discard any user changes to the memory regions and use target-supplied
13304 regions, if available, or no regions if the target does not support.
13307 @item delete mem @var{nums}@dots{}
13308 Remove memory regions @var{nums}@dots{} from the list of regions
13309 monitored by @value{GDBN}.
13311 @kindex disable mem
13312 @item disable mem @var{nums}@dots{}
13313 Disable monitoring of memory regions @var{nums}@dots{}.
13314 A disabled memory region is not forgotten.
13315 It may be enabled again later.
13318 @item enable mem @var{nums}@dots{}
13319 Enable monitoring of memory regions @var{nums}@dots{}.
13323 Print a table of all defined memory regions, with the following columns
13327 @item Memory Region Number
13328 @item Enabled or Disabled.
13329 Enabled memory regions are marked with @samp{y}.
13330 Disabled memory regions are marked with @samp{n}.
13333 The address defining the inclusive lower bound of the memory region.
13336 The address defining the exclusive upper bound of the memory region.
13339 The list of attributes set for this memory region.
13344 @subsection Attributes
13346 @subsubsection Memory Access Mode
13347 The access mode attributes set whether @value{GDBN} may make read or
13348 write accesses to a memory region.
13350 While these attributes prevent @value{GDBN} from performing invalid
13351 memory accesses, they do nothing to prevent the target system, I/O DMA,
13352 etc.@: from accessing memory.
13356 Memory is read only.
13358 Memory is write only.
13360 Memory is read/write. This is the default.
13363 @subsubsection Memory Access Size
13364 The access size attribute tells @value{GDBN} to use specific sized
13365 accesses in the memory region. Often memory mapped device registers
13366 require specific sized accesses. If no access size attribute is
13367 specified, @value{GDBN} may use accesses of any size.
13371 Use 8 bit memory accesses.
13373 Use 16 bit memory accesses.
13375 Use 32 bit memory accesses.
13377 Use 64 bit memory accesses.
13380 @c @subsubsection Hardware/Software Breakpoints
13381 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13382 @c will use hardware or software breakpoints for the internal breakpoints
13383 @c used by the step, next, finish, until, etc. commands.
13387 @c Always use hardware breakpoints
13388 @c @item swbreak (default)
13391 @subsubsection Data Cache
13392 The data cache attributes set whether @value{GDBN} will cache target
13393 memory. While this generally improves performance by reducing debug
13394 protocol overhead, it can lead to incorrect results because @value{GDBN}
13395 does not know about volatile variables or memory mapped device
13400 Enable @value{GDBN} to cache target memory.
13402 Disable @value{GDBN} from caching target memory. This is the default.
13405 @subsection Memory Access Checking
13406 @value{GDBN} can be instructed to refuse accesses to memory that is
13407 not explicitly described. This can be useful if accessing such
13408 regions has undesired effects for a specific target, or to provide
13409 better error checking. The following commands control this behaviour.
13412 @kindex set mem inaccessible-by-default
13413 @item set mem inaccessible-by-default [on|off]
13414 If @code{on} is specified, make @value{GDBN} treat memory not
13415 explicitly described by the memory ranges as non-existent and refuse accesses
13416 to such memory. The checks are only performed if there's at least one
13417 memory range defined. If @code{off} is specified, make @value{GDBN}
13418 treat the memory not explicitly described by the memory ranges as RAM.
13419 The default value is @code{on}.
13420 @kindex show mem inaccessible-by-default
13421 @item show mem inaccessible-by-default
13422 Show the current handling of accesses to unknown memory.
13426 @c @subsubsection Memory Write Verification
13427 @c The memory write verification attributes set whether @value{GDBN}
13428 @c will re-reads data after each write to verify the write was successful.
13432 @c @item noverify (default)
13435 @node Dump/Restore Files
13436 @section Copy Between Memory and a File
13437 @cindex dump/restore files
13438 @cindex append data to a file
13439 @cindex dump data to a file
13440 @cindex restore data from a file
13442 You can use the commands @code{dump}, @code{append}, and
13443 @code{restore} to copy data between target memory and a file. The
13444 @code{dump} and @code{append} commands write data to a file, and the
13445 @code{restore} command reads data from a file back into the inferior's
13446 memory. Files may be in binary, Motorola S-record, Intel hex,
13447 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13448 append to binary files, and cannot read from Verilog Hex files.
13453 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13454 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13455 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13456 or the value of @var{expr}, to @var{filename} in the given format.
13458 The @var{format} parameter may be any one of:
13465 Motorola S-record format.
13467 Tektronix Hex format.
13469 Verilog Hex format.
13472 @value{GDBN} uses the same definitions of these formats as the
13473 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13474 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13478 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13479 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13480 Append the contents of memory from @var{start_addr} to @var{end_addr},
13481 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13482 (@value{GDBN} can only append data to files in raw binary form.)
13485 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13486 Restore the contents of file @var{filename} into memory. The
13487 @code{restore} command can automatically recognize any known @sc{bfd}
13488 file format, except for raw binary. To restore a raw binary file you
13489 must specify the optional keyword @code{binary} after the filename.
13491 If @var{bias} is non-zero, its value will be added to the addresses
13492 contained in the file. Binary files always start at address zero, so
13493 they will be restored at address @var{bias}. Other bfd files have
13494 a built-in location; they will be restored at offset @var{bias}
13495 from that location.
13497 If @var{start} and/or @var{end} are non-zero, then only data between
13498 file offset @var{start} and file offset @var{end} will be restored.
13499 These offsets are relative to the addresses in the file, before
13500 the @var{bias} argument is applied.
13504 @node Core File Generation
13505 @section How to Produce a Core File from Your Program
13506 @cindex dump core from inferior
13508 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13509 image of a running process and its process status (register values
13510 etc.). Its primary use is post-mortem debugging of a program that
13511 crashed while it ran outside a debugger. A program that crashes
13512 automatically produces a core file, unless this feature is disabled by
13513 the user. @xref{Files}, for information on invoking @value{GDBN} in
13514 the post-mortem debugging mode.
13516 Occasionally, you may wish to produce a core file of the program you
13517 are debugging in order to preserve a snapshot of its state.
13518 @value{GDBN} has a special command for that.
13522 @kindex generate-core-file
13523 @item generate-core-file [@var{file}]
13524 @itemx gcore [@var{file}]
13525 Produce a core dump of the inferior process. The optional argument
13526 @var{file} specifies the file name where to put the core dump. If not
13527 specified, the file name defaults to @file{core.@var{pid}}, where
13528 @var{pid} is the inferior process ID.
13530 Note that this command is implemented only for some systems (as of
13531 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13533 On @sc{gnu}/Linux, this command can take into account the value of the
13534 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13535 dump (@pxref{set use-coredump-filter}), and by default honors the
13536 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13537 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13539 @kindex set use-coredump-filter
13540 @anchor{set use-coredump-filter}
13541 @item set use-coredump-filter on
13542 @itemx set use-coredump-filter off
13543 Enable or disable the use of the file
13544 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13545 files. This file is used by the Linux kernel to decide what types of
13546 memory mappings will be dumped or ignored when generating a core dump
13547 file. @var{pid} is the process ID of a currently running process.
13549 To make use of this feature, you have to write in the
13550 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13551 which is a bit mask representing the memory mapping types. If a bit
13552 is set in the bit mask, then the memory mappings of the corresponding
13553 types will be dumped; otherwise, they will be ignored. This
13554 configuration is inherited by child processes. For more information
13555 about the bits that can be set in the
13556 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13557 manpage of @code{core(5)}.
13559 By default, this option is @code{on}. If this option is turned
13560 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13561 and instead uses the same default value as the Linux kernel in order
13562 to decide which pages will be dumped in the core dump file. This
13563 value is currently @code{0x33}, which means that bits @code{0}
13564 (anonymous private mappings), @code{1} (anonymous shared mappings),
13565 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13566 This will cause these memory mappings to be dumped automatically.
13568 @kindex set dump-excluded-mappings
13569 @anchor{set dump-excluded-mappings}
13570 @item set dump-excluded-mappings on
13571 @itemx set dump-excluded-mappings off
13572 If @code{on} is specified, @value{GDBN} will dump memory mappings
13573 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13574 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13576 The default value is @code{off}.
13579 @node Character Sets
13580 @section Character Sets
13581 @cindex character sets
13583 @cindex translating between character sets
13584 @cindex host character set
13585 @cindex target character set
13587 If the program you are debugging uses a different character set to
13588 represent characters and strings than the one @value{GDBN} uses itself,
13589 @value{GDBN} can automatically translate between the character sets for
13590 you. The character set @value{GDBN} uses we call the @dfn{host
13591 character set}; the one the inferior program uses we call the
13592 @dfn{target character set}.
13594 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13595 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13596 remote protocol (@pxref{Remote Debugging}) to debug a program
13597 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13598 then the host character set is Latin-1, and the target character set is
13599 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13600 target-charset EBCDIC-US}, then @value{GDBN} translates between
13601 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13602 character and string literals in expressions.
13604 @value{GDBN} has no way to automatically recognize which character set
13605 the inferior program uses; you must tell it, using the @code{set
13606 target-charset} command, described below.
13608 Here are the commands for controlling @value{GDBN}'s character set
13612 @item set target-charset @var{charset}
13613 @kindex set target-charset
13614 Set the current target character set to @var{charset}. To display the
13615 list of supported target character sets, type
13616 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13618 @item set host-charset @var{charset}
13619 @kindex set host-charset
13620 Set the current host character set to @var{charset}.
13622 By default, @value{GDBN} uses a host character set appropriate to the
13623 system it is running on; you can override that default using the
13624 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13625 automatically determine the appropriate host character set. In this
13626 case, @value{GDBN} uses @samp{UTF-8}.
13628 @value{GDBN} can only use certain character sets as its host character
13629 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13630 @value{GDBN} will list the host character sets it supports.
13632 @item set charset @var{charset}
13633 @kindex set charset
13634 Set the current host and target character sets to @var{charset}. As
13635 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13636 @value{GDBN} will list the names of the character sets that can be used
13637 for both host and target.
13640 @kindex show charset
13641 Show the names of the current host and target character sets.
13643 @item show host-charset
13644 @kindex show host-charset
13645 Show the name of the current host character set.
13647 @item show target-charset
13648 @kindex show target-charset
13649 Show the name of the current target character set.
13651 @item set target-wide-charset @var{charset}
13652 @kindex set target-wide-charset
13653 Set the current target's wide character set to @var{charset}. This is
13654 the character set used by the target's @code{wchar_t} type. To
13655 display the list of supported wide character sets, type
13656 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13658 @item show target-wide-charset
13659 @kindex show target-wide-charset
13660 Show the name of the current target's wide character set.
13663 Here is an example of @value{GDBN}'s character set support in action.
13664 Assume that the following source code has been placed in the file
13665 @file{charset-test.c}:
13671 = @{72, 101, 108, 108, 111, 44, 32, 119,
13672 111, 114, 108, 100, 33, 10, 0@};
13673 char ibm1047_hello[]
13674 = @{200, 133, 147, 147, 150, 107, 64, 166,
13675 150, 153, 147, 132, 90, 37, 0@};
13679 printf ("Hello, world!\n");
13683 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13684 containing the string @samp{Hello, world!} followed by a newline,
13685 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13687 We compile the program, and invoke the debugger on it:
13690 $ gcc -g charset-test.c -o charset-test
13691 $ gdb -nw charset-test
13692 GNU gdb 2001-12-19-cvs
13693 Copyright 2001 Free Software Foundation, Inc.
13698 We can use the @code{show charset} command to see what character sets
13699 @value{GDBN} is currently using to interpret and display characters and
13703 (@value{GDBP}) show charset
13704 The current host and target character set is `ISO-8859-1'.
13708 For the sake of printing this manual, let's use @sc{ascii} as our
13709 initial character set:
13711 (@value{GDBP}) set charset ASCII
13712 (@value{GDBP}) show charset
13713 The current host and target character set is `ASCII'.
13717 Let's assume that @sc{ascii} is indeed the correct character set for our
13718 host system --- in other words, let's assume that if @value{GDBN} prints
13719 characters using the @sc{ascii} character set, our terminal will display
13720 them properly. Since our current target character set is also
13721 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13724 (@value{GDBP}) print ascii_hello
13725 $1 = 0x401698 "Hello, world!\n"
13726 (@value{GDBP}) print ascii_hello[0]
13731 @value{GDBN} uses the target character set for character and string
13732 literals you use in expressions:
13735 (@value{GDBP}) print '+'
13740 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13743 @value{GDBN} relies on the user to tell it which character set the
13744 target program uses. If we print @code{ibm1047_hello} while our target
13745 character set is still @sc{ascii}, we get jibberish:
13748 (@value{GDBP}) print ibm1047_hello
13749 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13750 (@value{GDBP}) print ibm1047_hello[0]
13755 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13756 @value{GDBN} tells us the character sets it supports:
13759 (@value{GDBP}) set target-charset
13760 ASCII EBCDIC-US IBM1047 ISO-8859-1
13761 (@value{GDBP}) set target-charset
13764 We can select @sc{ibm1047} as our target character set, and examine the
13765 program's strings again. Now the @sc{ascii} string is wrong, but
13766 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13767 target character set, @sc{ibm1047}, to the host character set,
13768 @sc{ascii}, and they display correctly:
13771 (@value{GDBP}) set target-charset IBM1047
13772 (@value{GDBP}) show charset
13773 The current host character set is `ASCII'.
13774 The current target character set is `IBM1047'.
13775 (@value{GDBP}) print ascii_hello
13776 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13777 (@value{GDBP}) print ascii_hello[0]
13779 (@value{GDBP}) print ibm1047_hello
13780 $8 = 0x4016a8 "Hello, world!\n"
13781 (@value{GDBP}) print ibm1047_hello[0]
13786 As above, @value{GDBN} uses the target character set for character and
13787 string literals you use in expressions:
13790 (@value{GDBP}) print '+'
13795 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13798 @node Caching Target Data
13799 @section Caching Data of Targets
13800 @cindex caching data of targets
13802 @value{GDBN} caches data exchanged between the debugger and a target.
13803 Each cache is associated with the address space of the inferior.
13804 @xref{Inferiors Connections and Programs}, about inferior and address space.
13805 Such caching generally improves performance in remote debugging
13806 (@pxref{Remote Debugging}), because it reduces the overhead of the
13807 remote protocol by bundling memory reads and writes into large chunks.
13808 Unfortunately, simply caching everything would lead to incorrect results,
13809 since @value{GDBN} does not necessarily know anything about volatile
13810 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13811 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13813 Therefore, by default, @value{GDBN} only caches data
13814 known to be on the stack@footnote{In non-stop mode, it is moderately
13815 rare for a running thread to modify the stack of a stopped thread
13816 in a way that would interfere with a backtrace, and caching of
13817 stack reads provides a significant speed up of remote backtraces.} or
13818 in the code segment.
13819 Other regions of memory can be explicitly marked as
13820 cacheable; @pxref{Memory Region Attributes}.
13823 @kindex set remotecache
13824 @item set remotecache on
13825 @itemx set remotecache off
13826 This option no longer does anything; it exists for compatibility
13829 @kindex show remotecache
13830 @item show remotecache
13831 Show the current state of the obsolete remotecache flag.
13833 @kindex set stack-cache
13834 @item set stack-cache on
13835 @itemx set stack-cache off
13836 Enable or disable caching of stack accesses. When @code{on}, use
13837 caching. By default, this option is @code{on}.
13839 @kindex show stack-cache
13840 @item show stack-cache
13841 Show the current state of data caching for memory accesses.
13843 @kindex set code-cache
13844 @item set code-cache on
13845 @itemx set code-cache off
13846 Enable or disable caching of code segment accesses. When @code{on},
13847 use caching. By default, this option is @code{on}. This improves
13848 performance of disassembly in remote debugging.
13850 @kindex show code-cache
13851 @item show code-cache
13852 Show the current state of target memory cache for code segment
13855 @kindex info dcache
13856 @item info dcache @r{[}line@r{]}
13857 Print the information about the performance of data cache of the
13858 current inferior's address space. The information displayed
13859 includes the dcache width and depth, and for each cache line, its
13860 number, address, and how many times it was referenced. This
13861 command is useful for debugging the data cache operation.
13863 If a line number is specified, the contents of that line will be
13866 @item set dcache size @var{size}
13867 @cindex dcache size
13868 @kindex set dcache size
13869 Set maximum number of entries in dcache (dcache depth above).
13871 @item set dcache line-size @var{line-size}
13872 @cindex dcache line-size
13873 @kindex set dcache line-size
13874 Set number of bytes each dcache entry caches (dcache width above).
13875 Must be a power of 2.
13877 @item show dcache size
13878 @kindex show dcache size
13879 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13881 @item show dcache line-size
13882 @kindex show dcache line-size
13883 Show default size of dcache lines.
13885 @item maint flush dcache
13886 @cindex dcache, flushing
13887 @kindex maint flush dcache
13888 Flush the contents (if any) of the dcache. This maintainer command is
13889 useful when debugging the dcache implementation.
13893 @node Searching Memory
13894 @section Search Memory
13895 @cindex searching memory
13897 Memory can be searched for a particular sequence of bytes with the
13898 @code{find} command.
13902 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13903 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13904 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13905 etc. The search begins at address @var{start_addr} and continues for either
13906 @var{len} bytes or through to @var{end_addr} inclusive.
13909 @var{s} and @var{n} are optional parameters.
13910 They may be specified in either order, apart or together.
13913 @item @var{s}, search query size
13914 The size of each search query value.
13920 halfwords (two bytes)
13924 giant words (eight bytes)
13927 All values are interpreted in the current language.
13928 This means, for example, that if the current source language is C/C@t{++}
13929 then searching for the string ``hello'' includes the trailing '\0'.
13930 The null terminator can be removed from searching by using casts,
13931 e.g.: @samp{@{char[5]@}"hello"}.
13933 If the value size is not specified, it is taken from the
13934 value's type in the current language.
13935 This is useful when one wants to specify the search
13936 pattern as a mixture of types.
13937 Note that this means, for example, that in the case of C-like languages
13938 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13939 which is typically four bytes.
13941 @item @var{n}, maximum number of finds
13942 The maximum number of matches to print. The default is to print all finds.
13945 You can use strings as search values. Quote them with double-quotes
13947 The string value is copied into the search pattern byte by byte,
13948 regardless of the endianness of the target and the size specification.
13950 The address of each match found is printed as well as a count of the
13951 number of matches found.
13953 The address of the last value found is stored in convenience variable
13955 A count of the number of matches is stored in @samp{$numfound}.
13957 For example, if stopped at the @code{printf} in this function:
13963 static char hello[] = "hello-hello";
13964 static struct @{ char c; short s; int i; @}
13965 __attribute__ ((packed)) mixed
13966 = @{ 'c', 0x1234, 0x87654321 @};
13967 printf ("%s\n", hello);
13972 you get during debugging:
13975 (gdb) find &hello[0], +sizeof(hello), "hello"
13976 0x804956d <hello.1620+6>
13978 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13979 0x8049567 <hello.1620>
13980 0x804956d <hello.1620+6>
13982 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13983 0x8049567 <hello.1620>
13984 0x804956d <hello.1620+6>
13986 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13987 0x8049567 <hello.1620>
13989 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13990 0x8049560 <mixed.1625>
13992 (gdb) print $numfound
13995 $2 = (void *) 0x8049560
13999 @section Value Sizes
14001 Whenever @value{GDBN} prints a value memory will be allocated within
14002 @value{GDBN} to hold the contents of the value. It is possible in
14003 some languages with dynamic typing systems, that an invalid program
14004 may indicate a value that is incorrectly large, this in turn may cause
14005 @value{GDBN} to try and allocate an overly large amount of memory.
14008 @kindex set max-value-size
14009 @item set max-value-size @var{bytes}
14010 @itemx set max-value-size unlimited
14011 Set the maximum size of memory that @value{GDBN} will allocate for the
14012 contents of a value to @var{bytes}, trying to display a value that
14013 requires more memory than that will result in an error.
14015 Setting this variable does not effect values that have already been
14016 allocated within @value{GDBN}, only future allocations.
14018 There's a minimum size that @code{max-value-size} can be set to in
14019 order that @value{GDBN} can still operate correctly, this minimum is
14020 currently 16 bytes.
14022 The limit applies to the results of some subexpressions as well as to
14023 complete expressions. For example, an expression denoting a simple
14024 integer component, such as @code{x.y.z}, may fail if the size of
14025 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14026 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14027 @var{A} is an array variable with non-constant size, will generally
14028 succeed regardless of the bounds on @var{A}, as long as the component
14029 size is less than @var{bytes}.
14031 The default value of @code{max-value-size} is currently 64k.
14033 @kindex show max-value-size
14034 @item show max-value-size
14035 Show the maximum size of memory, in bytes, that @value{GDBN} will
14036 allocate for the contents of a value.
14039 @node Optimized Code
14040 @chapter Debugging Optimized Code
14041 @cindex optimized code, debugging
14042 @cindex debugging optimized code
14044 Almost all compilers support optimization. With optimization
14045 disabled, the compiler generates assembly code that corresponds
14046 directly to your source code, in a simplistic way. As the compiler
14047 applies more powerful optimizations, the generated assembly code
14048 diverges from your original source code. With help from debugging
14049 information generated by the compiler, @value{GDBN} can map from
14050 the running program back to constructs from your original source.
14052 @value{GDBN} is more accurate with optimization disabled. If you
14053 can recompile without optimization, it is easier to follow the
14054 progress of your program during debugging. But, there are many cases
14055 where you may need to debug an optimized version.
14057 When you debug a program compiled with @samp{-g -O}, remember that the
14058 optimizer has rearranged your code; the debugger shows you what is
14059 really there. Do not be too surprised when the execution path does not
14060 exactly match your source file! An extreme example: if you define a
14061 variable, but never use it, @value{GDBN} never sees that
14062 variable---because the compiler optimizes it out of existence.
14064 Some things do not work as well with @samp{-g -O} as with just
14065 @samp{-g}, particularly on machines with instruction scheduling. If in
14066 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14067 please report it to us as a bug (including a test case!).
14068 @xref{Variables}, for more information about debugging optimized code.
14071 * Inline Functions:: How @value{GDBN} presents inlining
14072 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14075 @node Inline Functions
14076 @section Inline Functions
14077 @cindex inline functions, debugging
14079 @dfn{Inlining} is an optimization that inserts a copy of the function
14080 body directly at each call site, instead of jumping to a shared
14081 routine. @value{GDBN} displays inlined functions just like
14082 non-inlined functions. They appear in backtraces. You can view their
14083 arguments and local variables, step into them with @code{step}, skip
14084 them with @code{next}, and escape from them with @code{finish}.
14085 You can check whether a function was inlined by using the
14086 @code{info frame} command.
14088 For @value{GDBN} to support inlined functions, the compiler must
14089 record information about inlining in the debug information ---
14090 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14091 other compilers do also. @value{GDBN} only supports inlined functions
14092 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14093 do not emit two required attributes (@samp{DW_AT_call_file} and
14094 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14095 function calls with earlier versions of @value{NGCC}. It instead
14096 displays the arguments and local variables of inlined functions as
14097 local variables in the caller.
14099 The body of an inlined function is directly included at its call site;
14100 unlike a non-inlined function, there are no instructions devoted to
14101 the call. @value{GDBN} still pretends that the call site and the
14102 start of the inlined function are different instructions. Stepping to
14103 the call site shows the call site, and then stepping again shows
14104 the first line of the inlined function, even though no additional
14105 instructions are executed.
14107 This makes source-level debugging much clearer; you can see both the
14108 context of the call and then the effect of the call. Only stepping by
14109 a single instruction using @code{stepi} or @code{nexti} does not do
14110 this; single instruction steps always show the inlined body.
14112 There are some ways that @value{GDBN} does not pretend that inlined
14113 function calls are the same as normal calls:
14117 Setting breakpoints at the call site of an inlined function may not
14118 work, because the call site does not contain any code. @value{GDBN}
14119 may incorrectly move the breakpoint to the next line of the enclosing
14120 function, after the call. This limitation will be removed in a future
14121 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14122 or inside the inlined function instead.
14125 @value{GDBN} cannot locate the return value of inlined calls after
14126 using the @code{finish} command. This is a limitation of compiler-generated
14127 debugging information; after @code{finish}, you can step to the next line
14128 and print a variable where your program stored the return value.
14132 @node Tail Call Frames
14133 @section Tail Call Frames
14134 @cindex tail call frames, debugging
14136 Function @code{B} can call function @code{C} in its very last statement. In
14137 unoptimized compilation the call of @code{C} is immediately followed by return
14138 instruction at the end of @code{B} code. Optimizing compiler may replace the
14139 call and return in function @code{B} into one jump to function @code{C}
14140 instead. Such use of a jump instruction is called @dfn{tail call}.
14142 During execution of function @code{C}, there will be no indication in the
14143 function call stack frames that it was tail-called from @code{B}. If function
14144 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14145 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14146 some cases @value{GDBN} can determine that @code{C} was tail-called from
14147 @code{B}, and it will then create fictitious call frame for that, with the
14148 return address set up as if @code{B} called @code{C} normally.
14150 This functionality is currently supported only by DWARF 2 debugging format and
14151 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14152 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14155 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14156 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14160 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14162 Stack level 1, frame at 0x7fffffffda30:
14163 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14164 tail call frame, caller of frame at 0x7fffffffda30
14165 source language c++.
14166 Arglist at unknown address.
14167 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14170 The detection of all the possible code path executions can find them ambiguous.
14171 There is no execution history stored (possible @ref{Reverse Execution} is never
14172 used for this purpose) and the last known caller could have reached the known
14173 callee by multiple different jump sequences. In such case @value{GDBN} still
14174 tries to show at least all the unambiguous top tail callers and all the
14175 unambiguous bottom tail calees, if any.
14178 @anchor{set debug entry-values}
14179 @item set debug entry-values
14180 @kindex set debug entry-values
14181 When set to on, enables printing of analysis messages for both frame argument
14182 values at function entry and tail calls. It will show all the possible valid
14183 tail calls code paths it has considered. It will also print the intersection
14184 of them with the final unambiguous (possibly partial or even empty) code path
14187 @item show debug entry-values
14188 @kindex show debug entry-values
14189 Show the current state of analysis messages printing for both frame argument
14190 values at function entry and tail calls.
14193 The analysis messages for tail calls can for example show why the virtual tail
14194 call frame for function @code{c} has not been recognized (due to the indirect
14195 reference by variable @code{x}):
14198 static void __attribute__((noinline, noclone)) c (void);
14199 void (*x) (void) = c;
14200 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14201 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14202 int main (void) @{ x (); return 0; @}
14204 Breakpoint 1, DW_OP_entry_value resolving cannot find
14205 DW_TAG_call_site 0x40039a in main
14207 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14210 #1 0x000000000040039a in main () at t.c:5
14213 Another possibility is an ambiguous virtual tail call frames resolution:
14217 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14218 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14219 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14220 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14221 static void __attribute__((noinline, noclone)) b (void)
14222 @{ if (i) c (); else e (); @}
14223 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14224 int main (void) @{ a (); return 0; @}
14226 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14227 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14228 tailcall: reduced: 0x4004d2(a) |
14231 #1 0x00000000004004d2 in a () at t.c:8
14232 #2 0x0000000000400395 in main () at t.c:9
14235 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14236 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14238 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14239 @ifset HAVE_MAKEINFO_CLICK
14240 @set ARROW @click{}
14241 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14242 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14244 @ifclear HAVE_MAKEINFO_CLICK
14246 @set CALLSEQ1B @value{CALLSEQ1A}
14247 @set CALLSEQ2B @value{CALLSEQ2A}
14250 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14251 The code can have possible execution paths @value{CALLSEQ1B} or
14252 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14254 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14255 has found. It then finds another possible calling sequence - that one is
14256 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14257 printed as the @code{reduced:} calling sequence. That one could have many
14258 further @code{compare:} and @code{reduced:} statements as long as there remain
14259 any non-ambiguous sequence entries.
14261 For the frame of function @code{b} in both cases there are different possible
14262 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14263 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14264 therefore this one is displayed to the user while the ambiguous frames are
14267 There can be also reasons why printing of frame argument values at function
14272 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14273 static void __attribute__((noinline, noclone)) a (int i);
14274 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14275 static void __attribute__((noinline, noclone)) a (int i)
14276 @{ if (i) b (i - 1); else c (0); @}
14277 int main (void) @{ a (5); return 0; @}
14280 #0 c (i=i@@entry=0) at t.c:2
14281 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14282 function "a" at 0x400420 can call itself via tail calls
14283 i=<optimized out>) at t.c:6
14284 #2 0x000000000040036e in main () at t.c:7
14287 @value{GDBN} cannot find out from the inferior state if and how many times did
14288 function @code{a} call itself (via function @code{b}) as these calls would be
14289 tail calls. Such tail calls would modify the @code{i} variable, therefore
14290 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14291 prints @code{<optimized out>} instead.
14294 @chapter C Preprocessor Macros
14296 Some languages, such as C and C@t{++}, provide a way to define and invoke
14297 ``preprocessor macros'' which expand into strings of tokens.
14298 @value{GDBN} can evaluate expressions containing macro invocations, show
14299 the result of macro expansion, and show a macro's definition, including
14300 where it was defined.
14302 You may need to compile your program specially to provide @value{GDBN}
14303 with information about preprocessor macros. Most compilers do not
14304 include macros in their debugging information, even when you compile
14305 with the @option{-g} flag. @xref{Compilation}.
14307 A program may define a macro at one point, remove that definition later,
14308 and then provide a different definition after that. Thus, at different
14309 points in the program, a macro may have different definitions, or have
14310 no definition at all. If there is a current stack frame, @value{GDBN}
14311 uses the macros in scope at that frame's source code line. Otherwise,
14312 @value{GDBN} uses the macros in scope at the current listing location;
14315 Whenever @value{GDBN} evaluates an expression, it always expands any
14316 macro invocations present in the expression. @value{GDBN} also provides
14317 the following commands for working with macros explicitly.
14321 @kindex macro expand
14322 @cindex macro expansion, showing the results of preprocessor
14323 @cindex preprocessor macro expansion, showing the results of
14324 @cindex expanding preprocessor macros
14325 @item macro expand @var{expression}
14326 @itemx macro exp @var{expression}
14327 Show the results of expanding all preprocessor macro invocations in
14328 @var{expression}. Since @value{GDBN} simply expands macros, but does
14329 not parse the result, @var{expression} need not be a valid expression;
14330 it can be any string of tokens.
14333 @item macro expand-once @var{expression}
14334 @itemx macro exp1 @var{expression}
14335 @cindex expand macro once
14336 @i{(This command is not yet implemented.)} Show the results of
14337 expanding those preprocessor macro invocations that appear explicitly in
14338 @var{expression}. Macro invocations appearing in that expansion are
14339 left unchanged. This command allows you to see the effect of a
14340 particular macro more clearly, without being confused by further
14341 expansions. Since @value{GDBN} simply expands macros, but does not
14342 parse the result, @var{expression} need not be a valid expression; it
14343 can be any string of tokens.
14346 @cindex macro definition, showing
14347 @cindex definition of a macro, showing
14348 @cindex macros, from debug info
14349 @item info macro [-a|-all] [--] @var{macro}
14350 Show the current definition or all definitions of the named @var{macro},
14351 and describe the source location or compiler command-line where that
14352 definition was established. The optional double dash is to signify the end of
14353 argument processing and the beginning of @var{macro} for non C-like macros where
14354 the macro may begin with a hyphen.
14356 @kindex info macros
14357 @item info macros @var{locspec}
14358 Show all macro definitions that are in effect at the source line of
14359 the code location that results from resolving @var{locspec}, and
14360 describe the source location or compiler command-line where those
14361 definitions were established.
14363 @kindex macro define
14364 @cindex user-defined macros
14365 @cindex defining macros interactively
14366 @cindex macros, user-defined
14367 @item macro define @var{macro} @var{replacement-list}
14368 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14369 Introduce a definition for a preprocessor macro named @var{macro},
14370 invocations of which are replaced by the tokens given in
14371 @var{replacement-list}. The first form of this command defines an
14372 ``object-like'' macro, which takes no arguments; the second form
14373 defines a ``function-like'' macro, which takes the arguments given in
14376 A definition introduced by this command is in scope in every
14377 expression evaluated in @value{GDBN}, until it is removed with the
14378 @code{macro undef} command, described below. The definition overrides
14379 all definitions for @var{macro} present in the program being debugged,
14380 as well as any previous user-supplied definition.
14382 @kindex macro undef
14383 @item macro undef @var{macro}
14384 Remove any user-supplied definition for the macro named @var{macro}.
14385 This command only affects definitions provided with the @code{macro
14386 define} command, described above; it cannot remove definitions present
14387 in the program being debugged.
14391 List all the macros defined using the @code{macro define} command.
14394 @cindex macros, example of debugging with
14395 Here is a transcript showing the above commands in action. First, we
14396 show our source files:
14401 #include "sample.h"
14404 #define ADD(x) (M + x)
14409 printf ("Hello, world!\n");
14411 printf ("We're so creative.\n");
14413 printf ("Goodbye, world!\n");
14420 Now, we compile the program using the @sc{gnu} C compiler,
14421 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14422 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14423 and @option{-gdwarf-4}; we recommend always choosing the most recent
14424 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14425 includes information about preprocessor macros in the debugging
14429 $ gcc -gdwarf-2 -g3 sample.c -o sample
14433 Now, we start @value{GDBN} on our sample program:
14437 GNU gdb 2002-05-06-cvs
14438 Copyright 2002 Free Software Foundation, Inc.
14439 GDB is free software, @dots{}
14443 We can expand macros and examine their definitions, even when the
14444 program is not running. @value{GDBN} uses the current listing position
14445 to decide which macro definitions are in scope:
14448 (@value{GDBP}) list main
14451 5 #define ADD(x) (M + x)
14456 10 printf ("Hello, world!\n");
14458 12 printf ("We're so creative.\n");
14459 (@value{GDBP}) info macro ADD
14460 Defined at /home/jimb/gdb/macros/play/sample.c:5
14461 #define ADD(x) (M + x)
14462 (@value{GDBP}) info macro Q
14463 Defined at /home/jimb/gdb/macros/play/sample.h:1
14464 included at /home/jimb/gdb/macros/play/sample.c:2
14466 (@value{GDBP}) macro expand ADD(1)
14467 expands to: (42 + 1)
14468 (@value{GDBP}) macro expand-once ADD(1)
14469 expands to: once (M + 1)
14473 In the example above, note that @code{macro expand-once} expands only
14474 the macro invocation explicit in the original text --- the invocation of
14475 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14476 which was introduced by @code{ADD}.
14478 Once the program is running, @value{GDBN} uses the macro definitions in
14479 force at the source line of the current stack frame:
14482 (@value{GDBP}) break main
14483 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14485 Starting program: /home/jimb/gdb/macros/play/sample
14487 Breakpoint 1, main () at sample.c:10
14488 10 printf ("Hello, world!\n");
14492 At line 10, the definition of the macro @code{N} at line 9 is in force:
14495 (@value{GDBP}) info macro N
14496 Defined at /home/jimb/gdb/macros/play/sample.c:9
14498 (@value{GDBP}) macro expand N Q M
14499 expands to: 28 < 42
14500 (@value{GDBP}) print N Q M
14505 As we step over directives that remove @code{N}'s definition, and then
14506 give it a new definition, @value{GDBN} finds the definition (or lack
14507 thereof) in force at each point:
14510 (@value{GDBP}) next
14512 12 printf ("We're so creative.\n");
14513 (@value{GDBP}) info macro N
14514 The symbol `N' has no definition as a C/C++ preprocessor macro
14515 at /home/jimb/gdb/macros/play/sample.c:12
14516 (@value{GDBP}) next
14518 14 printf ("Goodbye, world!\n");
14519 (@value{GDBP}) info macro N
14520 Defined at /home/jimb/gdb/macros/play/sample.c:13
14522 (@value{GDBP}) macro expand N Q M
14523 expands to: 1729 < 42
14524 (@value{GDBP}) print N Q M
14529 In addition to source files, macros can be defined on the compilation command
14530 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14531 such a way, @value{GDBN} displays the location of their definition as line zero
14532 of the source file submitted to the compiler.
14535 (@value{GDBP}) info macro __STDC__
14536 Defined at /home/jimb/gdb/macros/play/sample.c:0
14543 @chapter Tracepoints
14544 @c This chapter is based on the documentation written by Michael
14545 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14547 @cindex tracepoints
14548 In some applications, it is not feasible for the debugger to interrupt
14549 the program's execution long enough for the developer to learn
14550 anything helpful about its behavior. If the program's correctness
14551 depends on its real-time behavior, delays introduced by a debugger
14552 might cause the program to change its behavior drastically, or perhaps
14553 fail, even when the code itself is correct. It is useful to be able
14554 to observe the program's behavior without interrupting it.
14556 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14557 specify locations in the program, called @dfn{tracepoints}, and
14558 arbitrary expressions to evaluate when those tracepoints are reached.
14559 Later, using the @code{tfind} command, you can examine the values
14560 those expressions had when the program hit the tracepoints. The
14561 expressions may also denote objects in memory---structures or arrays,
14562 for example---whose values @value{GDBN} should record; while visiting
14563 a particular tracepoint, you may inspect those objects as if they were
14564 in memory at that moment. However, because @value{GDBN} records these
14565 values without interacting with you, it can do so quickly and
14566 unobtrusively, hopefully not disturbing the program's behavior.
14568 The tracepoint facility is currently available only for remote
14569 targets. @xref{Targets}. In addition, your remote target must know
14570 how to collect trace data. This functionality is implemented in the
14571 remote stub; however, none of the stubs distributed with @value{GDBN}
14572 support tracepoints as of this writing. The format of the remote
14573 packets used to implement tracepoints are described in @ref{Tracepoint
14576 It is also possible to get trace data from a file, in a manner reminiscent
14577 of corefiles; you specify the filename, and use @code{tfind} to search
14578 through the file. @xref{Trace Files}, for more details.
14580 This chapter describes the tracepoint commands and features.
14583 * Set Tracepoints::
14584 * Analyze Collected Data::
14585 * Tracepoint Variables::
14589 @node Set Tracepoints
14590 @section Commands to Set Tracepoints
14592 Before running such a @dfn{trace experiment}, an arbitrary number of
14593 tracepoints can be set. A tracepoint is actually a special type of
14594 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14595 standard breakpoint commands. For instance, as with breakpoints,
14596 tracepoint numbers are successive integers starting from one, and many
14597 of the commands associated with tracepoints take the tracepoint number
14598 as their argument, to identify which tracepoint to work on.
14600 For each tracepoint, you can specify, in advance, some arbitrary set
14601 of data that you want the target to collect in the trace buffer when
14602 it hits that tracepoint. The collected data can include registers,
14603 local variables, or global data. Later, you can use @value{GDBN}
14604 commands to examine the values these data had at the time the
14605 tracepoint was hit.
14607 Tracepoints do not support every breakpoint feature. Ignore counts on
14608 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14609 commands when they are hit. Tracepoints may not be thread-specific
14612 @cindex fast tracepoints
14613 Some targets may support @dfn{fast tracepoints}, which are inserted in
14614 a different way (such as with a jump instead of a trap), that is
14615 faster but possibly restricted in where they may be installed.
14617 @cindex static tracepoints
14618 @cindex markers, static tracepoints
14619 @cindex probing markers, static tracepoints
14620 Regular and fast tracepoints are dynamic tracing facilities, meaning
14621 that they can be used to insert tracepoints at (almost) any location
14622 in the target. Some targets may also support controlling @dfn{static
14623 tracepoints} from @value{GDBN}. With static tracing, a set of
14624 instrumentation points, also known as @dfn{markers}, are embedded in
14625 the target program, and can be activated or deactivated by name or
14626 address. These are usually placed at locations which facilitate
14627 investigating what the target is actually doing. @value{GDBN}'s
14628 support for static tracing includes being able to list instrumentation
14629 points, and attach them with @value{GDBN} defined high level
14630 tracepoints that expose the whole range of convenience of
14631 @value{GDBN}'s tracepoints support. Namely, support for collecting
14632 registers values and values of global or local (to the instrumentation
14633 point) variables; tracepoint conditions and trace state variables.
14634 The act of installing a @value{GDBN} static tracepoint on an
14635 instrumentation point, or marker, is referred to as @dfn{probing} a
14636 static tracepoint marker.
14638 @code{gdbserver} supports tracepoints on some target systems.
14639 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14641 This section describes commands to set tracepoints and associated
14642 conditions and actions.
14645 * Create and Delete Tracepoints::
14646 * Enable and Disable Tracepoints::
14647 * Tracepoint Passcounts::
14648 * Tracepoint Conditions::
14649 * Trace State Variables::
14650 * Tracepoint Actions::
14651 * Listing Tracepoints::
14652 * Listing Static Tracepoint Markers::
14653 * Starting and Stopping Trace Experiments::
14654 * Tracepoint Restrictions::
14657 @node Create and Delete Tracepoints
14658 @subsection Create and Delete Tracepoints
14661 @cindex set tracepoint
14663 @item trace @var{locspec}
14664 The @code{trace} command is very similar to the @code{break} command.
14665 Its argument @var{locspec} can be any valid location specification.
14666 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
14667 which is a point in the target program where the debugger will briefly stop,
14668 collect some data, and then allow the program to continue. Setting a tracepoint
14669 or changing its actions takes effect immediately if the remote stub
14670 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14672 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14673 these changes don't take effect until the next @code{tstart}
14674 command, and once a trace experiment is running, further changes will
14675 not have any effect until the next trace experiment starts. In addition,
14676 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14677 address is not yet resolved. (This is similar to pending breakpoints.)
14678 Pending tracepoints are not downloaded to the target and not installed
14679 until they are resolved. The resolution of pending tracepoints requires
14680 @value{GDBN} support---when debugging with the remote target, and
14681 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14682 tracing}), pending tracepoints can not be resolved (and downloaded to
14683 the remote stub) while @value{GDBN} is disconnected.
14685 Here are some examples of using the @code{trace} command:
14688 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14690 (@value{GDBP}) @b{trace +2} // 2 lines forward
14692 (@value{GDBP}) @b{trace my_function} // first source line of function
14694 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14696 (@value{GDBP}) @b{trace *0x2117c4} // an address
14700 You can abbreviate @code{trace} as @code{tr}.
14702 @item trace @var{locspec} if @var{cond}
14703 Set a tracepoint with condition @var{cond}; evaluate the expression
14704 @var{cond} each time the tracepoint is reached, and collect data only
14705 if the value is nonzero---that is, if @var{cond} evaluates as true.
14706 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14707 information on tracepoint conditions.
14709 @item ftrace @var{locspec} [ if @var{cond} ]
14710 @cindex set fast tracepoint
14711 @cindex fast tracepoints, setting
14713 The @code{ftrace} command sets a fast tracepoint. For targets that
14714 support them, fast tracepoints will use a more efficient but possibly
14715 less general technique to trigger data collection, such as a jump
14716 instruction instead of a trap, or some sort of hardware support. It
14717 may not be possible to create a fast tracepoint at the desired
14718 location, in which case the command will exit with an explanatory
14721 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14724 On 32-bit x86-architecture systems, fast tracepoints normally need to
14725 be placed at an instruction that is 5 bytes or longer, but can be
14726 placed at 4-byte instructions if the low 64K of memory of the target
14727 program is available to install trampolines. Some Unix-type systems,
14728 such as @sc{gnu}/Linux, exclude low addresses from the program's
14729 address space; but for instance with the Linux kernel it is possible
14730 to let @value{GDBN} use this area by doing a @command{sysctl} command
14731 to set the @code{mmap_min_addr} kernel parameter, as in
14734 sudo sysctl -w vm.mmap_min_addr=32768
14738 which sets the low address to 32K, which leaves plenty of room for
14739 trampolines. The minimum address should be set to a page boundary.
14741 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
14742 @cindex set static tracepoint
14743 @cindex static tracepoints, setting
14744 @cindex probe static tracepoint marker
14746 The @code{strace} command sets a static tracepoint. For targets that
14747 support it, setting a static tracepoint probes a static
14748 instrumentation point, or marker, found at the code locations that
14749 result from resolving @var{locspec}. It may not be possible to set a
14750 static tracepoint at the desired code location, in which case the
14751 command will exit with an explanatory message.
14753 @value{GDBN} handles arguments to @code{strace} exactly as for
14754 @code{trace}, with the addition that the user can also specify
14755 @code{-m @var{marker}} instead of a location spec. This probes the marker
14756 identified by the @var{marker} string identifier. This identifier
14757 depends on the static tracepoint backend library your program is
14758 using. You can find all the marker identifiers in the @samp{ID} field
14759 of the @code{info static-tracepoint-markers} command output.
14760 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14761 Markers}. For example, in the following small program using the UST
14767 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14772 the marker id is composed of joining the first two arguments to the
14773 @code{trace_mark} call with a slash, which translates to:
14776 (@value{GDBP}) info static-tracepoint-markers
14777 Cnt Enb ID Address What
14778 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14784 so you may probe the marker above with:
14787 (@value{GDBP}) strace -m ust/bar33
14790 Static tracepoints accept an extra collect action --- @code{collect
14791 $_sdata}. This collects arbitrary user data passed in the probe point
14792 call to the tracing library. In the UST example above, you'll see
14793 that the third argument to @code{trace_mark} is a printf-like format
14794 string. The user data is then the result of running that formatting
14795 string against the following arguments. Note that @code{info
14796 static-tracepoint-markers} command output lists that format string in
14797 the @samp{Data:} field.
14799 You can inspect this data when analyzing the trace buffer, by printing
14800 the $_sdata variable like any other variable available to
14801 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14804 @cindex last tracepoint number
14805 @cindex recent tracepoint number
14806 @cindex tracepoint number
14807 The convenience variable @code{$tpnum} records the tracepoint number
14808 of the most recently set tracepoint.
14810 @kindex delete tracepoint
14811 @cindex tracepoint deletion
14812 @item delete tracepoint @r{[}@var{num}@r{]}
14813 Permanently delete one or more tracepoints. With no argument, the
14814 default is to delete all tracepoints. Note that the regular
14815 @code{delete} command can remove tracepoints also.
14820 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14822 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14826 You can abbreviate this command as @code{del tr}.
14829 @node Enable and Disable Tracepoints
14830 @subsection Enable and Disable Tracepoints
14832 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14835 @kindex disable tracepoint
14836 @item disable tracepoint @r{[}@var{num}@r{]}
14837 Disable tracepoint @var{num}, or all tracepoints if no argument
14838 @var{num} is given. A disabled tracepoint will have no effect during
14839 a trace experiment, but it is not forgotten. You can re-enable
14840 a disabled tracepoint using the @code{enable tracepoint} command.
14841 If the command is issued during a trace experiment and the debug target
14842 has support for disabling tracepoints during a trace experiment, then the
14843 change will be effective immediately. Otherwise, it will be applied to the
14844 next trace experiment.
14846 @kindex enable tracepoint
14847 @item enable tracepoint @r{[}@var{num}@r{]}
14848 Enable tracepoint @var{num}, or all tracepoints. If this command is
14849 issued during a trace experiment and the debug target supports enabling
14850 tracepoints during a trace experiment, then the enabled tracepoints will
14851 become effective immediately. Otherwise, they will become effective the
14852 next time a trace experiment is run.
14855 @node Tracepoint Passcounts
14856 @subsection Tracepoint Passcounts
14860 @cindex tracepoint pass count
14861 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14862 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14863 automatically stop a trace experiment. If a tracepoint's passcount is
14864 @var{n}, then the trace experiment will be automatically stopped on
14865 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14866 @var{num} is not specified, the @code{passcount} command sets the
14867 passcount of the most recently defined tracepoint. If no passcount is
14868 given, the trace experiment will run until stopped explicitly by the
14874 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14875 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14877 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14878 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14879 (@value{GDBP}) @b{trace foo}
14880 (@value{GDBP}) @b{pass 3}
14881 (@value{GDBP}) @b{trace bar}
14882 (@value{GDBP}) @b{pass 2}
14883 (@value{GDBP}) @b{trace baz}
14884 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14885 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14886 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14887 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14891 @node Tracepoint Conditions
14892 @subsection Tracepoint Conditions
14893 @cindex conditional tracepoints
14894 @cindex tracepoint conditions
14896 The simplest sort of tracepoint collects data every time your program
14897 reaches a specified place. You can also specify a @dfn{condition} for
14898 a tracepoint. A condition is just a Boolean expression in your
14899 programming language (@pxref{Expressions, ,Expressions}). A
14900 tracepoint with a condition evaluates the expression each time your
14901 program reaches it, and data collection happens only if the condition
14904 Tracepoint conditions can be specified when a tracepoint is set, by
14905 using @samp{if} in the arguments to the @code{trace} command.
14906 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14907 also be set or changed at any time with the @code{condition} command,
14908 just as with breakpoints.
14910 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14911 the conditional expression itself. Instead, @value{GDBN} encodes the
14912 expression into an agent expression (@pxref{Agent Expressions})
14913 suitable for execution on the target, independently of @value{GDBN}.
14914 Global variables become raw memory locations, locals become stack
14915 accesses, and so forth.
14917 For instance, suppose you have a function that is usually called
14918 frequently, but should not be called after an error has occurred. You
14919 could use the following tracepoint command to collect data about calls
14920 of that function that happen while the error code is propagating
14921 through the program; an unconditional tracepoint could end up
14922 collecting thousands of useless trace frames that you would have to
14926 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14929 @node Trace State Variables
14930 @subsection Trace State Variables
14931 @cindex trace state variables
14933 A @dfn{trace state variable} is a special type of variable that is
14934 created and managed by target-side code. The syntax is the same as
14935 that for GDB's convenience variables (a string prefixed with ``$''),
14936 but they are stored on the target. They must be created explicitly,
14937 using a @code{tvariable} command. They are always 64-bit signed
14940 Trace state variables are remembered by @value{GDBN}, and downloaded
14941 to the target along with tracepoint information when the trace
14942 experiment starts. There are no intrinsic limits on the number of
14943 trace state variables, beyond memory limitations of the target.
14945 @cindex convenience variables, and trace state variables
14946 Although trace state variables are managed by the target, you can use
14947 them in print commands and expressions as if they were convenience
14948 variables; @value{GDBN} will get the current value from the target
14949 while the trace experiment is running. Trace state variables share
14950 the same namespace as other ``$'' variables, which means that you
14951 cannot have trace state variables with names like @code{$23} or
14952 @code{$pc}, nor can you have a trace state variable and a convenience
14953 variable with the same name.
14957 @item tvariable $@var{name} [ = @var{expression} ]
14959 The @code{tvariable} command creates a new trace state variable named
14960 @code{$@var{name}}, and optionally gives it an initial value of
14961 @var{expression}. The @var{expression} is evaluated when this command is
14962 entered; the result will be converted to an integer if possible,
14963 otherwise @value{GDBN} will report an error. A subsequent
14964 @code{tvariable} command specifying the same name does not create a
14965 variable, but instead assigns the supplied initial value to the
14966 existing variable of that name, overwriting any previous initial
14967 value. The default initial value is 0.
14969 @item info tvariables
14970 @kindex info tvariables
14971 List all the trace state variables along with their initial values.
14972 Their current values may also be displayed, if the trace experiment is
14975 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14976 @kindex delete tvariable
14977 Delete the given trace state variables, or all of them if no arguments
14982 @node Tracepoint Actions
14983 @subsection Tracepoint Action Lists
14987 @cindex tracepoint actions
14988 @item actions @r{[}@var{num}@r{]}
14989 This command will prompt for a list of actions to be taken when the
14990 tracepoint is hit. If the tracepoint number @var{num} is not
14991 specified, this command sets the actions for the one that was most
14992 recently defined (so that you can define a tracepoint and then say
14993 @code{actions} without bothering about its number). You specify the
14994 actions themselves on the following lines, one action at a time, and
14995 terminate the actions list with a line containing just @code{end}. So
14996 far, the only defined actions are @code{collect}, @code{teval}, and
14997 @code{while-stepping}.
14999 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
15000 Commands, ,Breakpoint Command Lists}), except that only the defined
15001 actions are allowed; any other @value{GDBN} command is rejected.
15003 @cindex remove actions from a tracepoint
15004 To remove all actions from a tracepoint, type @samp{actions @var{num}}
15005 and follow it immediately with @samp{end}.
15008 (@value{GDBP}) @b{collect @var{data}} // collect some data
15010 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
15012 (@value{GDBP}) @b{end} // signals the end of actions.
15015 In the following example, the action list begins with @code{collect}
15016 commands indicating the things to be collected when the tracepoint is
15017 hit. Then, in order to single-step and collect additional data
15018 following the tracepoint, a @code{while-stepping} command is used,
15019 followed by the list of things to be collected after each step in a
15020 sequence of single steps. The @code{while-stepping} command is
15021 terminated by its own separate @code{end} command. Lastly, the action
15022 list is terminated by an @code{end} command.
15025 (@value{GDBP}) @b{trace foo}
15026 (@value{GDBP}) @b{actions}
15027 Enter actions for tracepoint 1, one per line:
15030 > while-stepping 12
15031 > collect $pc, arr[i]
15036 @kindex collect @r{(tracepoints)}
15037 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15038 Collect values of the given expressions when the tracepoint is hit.
15039 This command accepts a comma-separated list of any valid expressions.
15040 In addition to global, static, or local variables, the following
15041 special arguments are supported:
15045 Collect all registers.
15048 Collect all function arguments.
15051 Collect all local variables.
15054 Collect the return address. This is helpful if you want to see more
15057 @emph{Note:} The return address location can not always be reliably
15058 determined up front, and the wrong address / registers may end up
15059 collected instead. On some architectures the reliability is higher
15060 for tracepoints at function entry, while on others it's the opposite.
15061 When this happens, backtracing will stop because the return address is
15062 found unavailable (unless another collect rule happened to match it).
15065 Collects the number of arguments from the static probe at which the
15066 tracepoint is located.
15067 @xref{Static Probe Points}.
15069 @item $_probe_arg@var{n}
15070 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15071 from the static probe at which the tracepoint is located.
15072 @xref{Static Probe Points}.
15075 @vindex $_sdata@r{, collect}
15076 Collect static tracepoint marker specific data. Only available for
15077 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15078 Lists}. On the UST static tracepoints library backend, an
15079 instrumentation point resembles a @code{printf} function call. The
15080 tracing library is able to collect user specified data formatted to a
15081 character string using the format provided by the programmer that
15082 instrumented the program. Other backends have similar mechanisms.
15083 Here's an example of a UST marker call:
15086 const char master_name[] = "$your_name";
15087 trace_mark(channel1, marker1, "hello %s", master_name)
15090 In this case, collecting @code{$_sdata} collects the string
15091 @samp{hello $yourname}. When analyzing the trace buffer, you can
15092 inspect @samp{$_sdata} like any other variable available to
15096 You can give several consecutive @code{collect} commands, each one
15097 with a single argument, or one @code{collect} command with several
15098 arguments separated by commas; the effect is the same.
15100 The optional @var{mods} changes the usual handling of the arguments.
15101 @code{s} requests that pointers to chars be handled as strings, in
15102 particular collecting the contents of the memory being pointed at, up
15103 to the first zero. The upper bound is by default the value of the
15104 @code{print elements} variable; if @code{s} is followed by a decimal
15105 number, that is the upper bound instead. So for instance
15106 @samp{collect/s25 mystr} collects as many as 25 characters at
15109 The command @code{info scope} (@pxref{Symbols, info scope}) is
15110 particularly useful for figuring out what data to collect.
15112 @kindex teval @r{(tracepoints)}
15113 @item teval @var{expr1}, @var{expr2}, @dots{}
15114 Evaluate the given expressions when the tracepoint is hit. This
15115 command accepts a comma-separated list of expressions. The results
15116 are discarded, so this is mainly useful for assigning values to trace
15117 state variables (@pxref{Trace State Variables}) without adding those
15118 values to the trace buffer, as would be the case if the @code{collect}
15121 @kindex while-stepping @r{(tracepoints)}
15122 @item while-stepping @var{n}
15123 Perform @var{n} single-step instruction traces after the tracepoint,
15124 collecting new data after each step. The @code{while-stepping}
15125 command is followed by the list of what to collect while stepping
15126 (followed by its own @code{end} command):
15129 > while-stepping 12
15130 > collect $regs, myglobal
15136 Note that @code{$pc} is not automatically collected by
15137 @code{while-stepping}; you need to explicitly collect that register if
15138 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15141 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15142 @kindex set default-collect
15143 @cindex default collection action
15144 This variable is a list of expressions to collect at each tracepoint
15145 hit. It is effectively an additional @code{collect} action prepended
15146 to every tracepoint action list. The expressions are parsed
15147 individually for each tracepoint, so for instance a variable named
15148 @code{xyz} may be interpreted as a global for one tracepoint, and a
15149 local for another, as appropriate to the tracepoint's location.
15151 @item show default-collect
15152 @kindex show default-collect
15153 Show the list of expressions that are collected by default at each
15158 @node Listing Tracepoints
15159 @subsection Listing Tracepoints
15162 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15163 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15164 @cindex information about tracepoints
15165 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15166 Display information about the tracepoint @var{num}. If you don't
15167 specify a tracepoint number, displays information about all the
15168 tracepoints defined so far. The format is similar to that used for
15169 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15170 command, simply restricting itself to tracepoints.
15172 A tracepoint's listing may include additional information specific to
15177 its passcount as given by the @code{passcount @var{n}} command
15180 the state about installed on target of each location
15184 (@value{GDBP}) @b{info trace}
15185 Num Type Disp Enb Address What
15186 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15188 collect globfoo, $regs
15193 2 tracepoint keep y <MULTIPLE>
15195 2.1 y 0x0804859c in func4 at change-loc.h:35
15196 installed on target
15197 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15198 installed on target
15199 2.3 y <PENDING> set_tracepoint
15200 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15201 not installed on target
15206 This command can be abbreviated @code{info tp}.
15209 @node Listing Static Tracepoint Markers
15210 @subsection Listing Static Tracepoint Markers
15213 @kindex info static-tracepoint-markers
15214 @cindex information about static tracepoint markers
15215 @item info static-tracepoint-markers
15216 Display information about all static tracepoint markers defined in the
15219 For each marker, the following columns are printed:
15223 An incrementing counter, output to help readability. This is not a
15226 The marker ID, as reported by the target.
15227 @item Enabled or Disabled
15228 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15229 that are not enabled.
15231 Where the marker is in your program, as a memory address.
15233 Where the marker is in the source for your program, as a file and line
15234 number. If the debug information included in the program does not
15235 allow @value{GDBN} to locate the source of the marker, this column
15236 will be left blank.
15240 In addition, the following information may be printed for each marker:
15244 User data passed to the tracing library by the marker call. In the
15245 UST backend, this is the format string passed as argument to the
15247 @item Static tracepoints probing the marker
15248 The list of static tracepoints attached to the marker.
15252 (@value{GDBP}) info static-tracepoint-markers
15253 Cnt ID Enb Address What
15254 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15255 Data: number1 %d number2 %d
15256 Probed by static tracepoints: #2
15257 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15263 @node Starting and Stopping Trace Experiments
15264 @subsection Starting and Stopping Trace Experiments
15267 @kindex tstart [ @var{notes} ]
15268 @cindex start a new trace experiment
15269 @cindex collected data discarded
15271 This command starts the trace experiment, and begins collecting data.
15272 It has the side effect of discarding all the data collected in the
15273 trace buffer during the previous trace experiment. If any arguments
15274 are supplied, they are taken as a note and stored with the trace
15275 experiment's state. The notes may be arbitrary text, and are
15276 especially useful with disconnected tracing in a multi-user context;
15277 the notes can explain what the trace is doing, supply user contact
15278 information, and so forth.
15280 @kindex tstop [ @var{notes} ]
15281 @cindex stop a running trace experiment
15283 This command stops the trace experiment. If any arguments are
15284 supplied, they are recorded with the experiment as a note. This is
15285 useful if you are stopping a trace started by someone else, for
15286 instance if the trace is interfering with the system's behavior and
15287 needs to be stopped quickly.
15289 @strong{Note}: a trace experiment and data collection may stop
15290 automatically if any tracepoint's passcount is reached
15291 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15294 @cindex status of trace data collection
15295 @cindex trace experiment, status of
15297 This command displays the status of the current trace data
15301 Here is an example of the commands we described so far:
15304 (@value{GDBP}) @b{trace gdb_c_test}
15305 (@value{GDBP}) @b{actions}
15306 Enter actions for tracepoint #1, one per line.
15307 > collect $regs,$locals,$args
15308 > while-stepping 11
15312 (@value{GDBP}) @b{tstart}
15313 [time passes @dots{}]
15314 (@value{GDBP}) @b{tstop}
15317 @anchor{disconnected tracing}
15318 @cindex disconnected tracing
15319 You can choose to continue running the trace experiment even if
15320 @value{GDBN} disconnects from the target, voluntarily or
15321 involuntarily. For commands such as @code{detach}, the debugger will
15322 ask what you want to do with the trace. But for unexpected
15323 terminations (@value{GDBN} crash, network outage), it would be
15324 unfortunate to lose hard-won trace data, so the variable
15325 @code{disconnected-tracing} lets you decide whether the trace should
15326 continue running without @value{GDBN}.
15329 @item set disconnected-tracing on
15330 @itemx set disconnected-tracing off
15331 @kindex set disconnected-tracing
15332 Choose whether a tracing run should continue to run if @value{GDBN}
15333 has disconnected from the target. Note that @code{detach} or
15334 @code{quit} will ask you directly what to do about a running trace no
15335 matter what this variable's setting, so the variable is mainly useful
15336 for handling unexpected situations, such as loss of the network.
15338 @item show disconnected-tracing
15339 @kindex show disconnected-tracing
15340 Show the current choice for disconnected tracing.
15344 When you reconnect to the target, the trace experiment may or may not
15345 still be running; it might have filled the trace buffer in the
15346 meantime, or stopped for one of the other reasons. If it is running,
15347 it will continue after reconnection.
15349 Upon reconnection, the target will upload information about the
15350 tracepoints in effect. @value{GDBN} will then compare that
15351 information to the set of tracepoints currently defined, and attempt
15352 to match them up, allowing for the possibility that the numbers may
15353 have changed due to creation and deletion in the meantime. If one of
15354 the target's tracepoints does not match any in @value{GDBN}, the
15355 debugger will create a new tracepoint, so that you have a number with
15356 which to specify that tracepoint. This matching-up process is
15357 necessarily heuristic, and it may result in useless tracepoints being
15358 created; you may simply delete them if they are of no use.
15360 @cindex circular trace buffer
15361 If your target agent supports a @dfn{circular trace buffer}, then you
15362 can run a trace experiment indefinitely without filling the trace
15363 buffer; when space runs out, the agent deletes already-collected trace
15364 frames, oldest first, until there is enough room to continue
15365 collecting. This is especially useful if your tracepoints are being
15366 hit too often, and your trace gets terminated prematurely because the
15367 buffer is full. To ask for a circular trace buffer, simply set
15368 @samp{circular-trace-buffer} to on. You can set this at any time,
15369 including during tracing; if the agent can do it, it will change
15370 buffer handling on the fly, otherwise it will not take effect until
15374 @item set circular-trace-buffer on
15375 @itemx set circular-trace-buffer off
15376 @kindex set circular-trace-buffer
15377 Choose whether a tracing run should use a linear or circular buffer
15378 for trace data. A linear buffer will not lose any trace data, but may
15379 fill up prematurely, while a circular buffer will discard old trace
15380 data, but it will have always room for the latest tracepoint hits.
15382 @item show circular-trace-buffer
15383 @kindex show circular-trace-buffer
15384 Show the current choice for the trace buffer. Note that this may not
15385 match the agent's current buffer handling, nor is it guaranteed to
15386 match the setting that might have been in effect during a past run,
15387 for instance if you are looking at frames from a trace file.
15392 @item set trace-buffer-size @var{n}
15393 @itemx set trace-buffer-size unlimited
15394 @kindex set trace-buffer-size
15395 Request that the target use a trace buffer of @var{n} bytes. Not all
15396 targets will honor the request; they may have a compiled-in size for
15397 the trace buffer, or some other limitation. Set to a value of
15398 @code{unlimited} or @code{-1} to let the target use whatever size it
15399 likes. This is also the default.
15401 @item show trace-buffer-size
15402 @kindex show trace-buffer-size
15403 Show the current requested size for the trace buffer. Note that this
15404 will only match the actual size if the target supports size-setting,
15405 and was able to handle the requested size. For instance, if the
15406 target can only change buffer size between runs, this variable will
15407 not reflect the change until the next run starts. Use @code{tstatus}
15408 to get a report of the actual buffer size.
15412 @item set trace-user @var{text}
15413 @kindex set trace-user
15415 @item show trace-user
15416 @kindex show trace-user
15418 @item set trace-notes @var{text}
15419 @kindex set trace-notes
15420 Set the trace run's notes.
15422 @item show trace-notes
15423 @kindex show trace-notes
15424 Show the trace run's notes.
15426 @item set trace-stop-notes @var{text}
15427 @kindex set trace-stop-notes
15428 Set the trace run's stop notes. The handling of the note is as for
15429 @code{tstop} arguments; the set command is convenient way to fix a
15430 stop note that is mistaken or incomplete.
15432 @item show trace-stop-notes
15433 @kindex show trace-stop-notes
15434 Show the trace run's stop notes.
15438 @node Tracepoint Restrictions
15439 @subsection Tracepoint Restrictions
15441 @cindex tracepoint restrictions
15442 There are a number of restrictions on the use of tracepoints. As
15443 described above, tracepoint data gathering occurs on the target
15444 without interaction from @value{GDBN}. Thus the full capabilities of
15445 the debugger are not available during data gathering, and then at data
15446 examination time, you will be limited by only having what was
15447 collected. The following items describe some common problems, but it
15448 is not exhaustive, and you may run into additional difficulties not
15454 Tracepoint expressions are intended to gather objects (lvalues). Thus
15455 the full flexibility of GDB's expression evaluator is not available.
15456 You cannot call functions, cast objects to aggregate types, access
15457 convenience variables or modify values (except by assignment to trace
15458 state variables). Some language features may implicitly call
15459 functions (for instance Objective-C fields with accessors), and therefore
15460 cannot be collected either.
15463 Collection of local variables, either individually or in bulk with
15464 @code{$locals} or @code{$args}, during @code{while-stepping} may
15465 behave erratically. The stepping action may enter a new scope (for
15466 instance by stepping into a function), or the location of the variable
15467 may change (for instance it is loaded into a register). The
15468 tracepoint data recorded uses the location information for the
15469 variables that is correct for the tracepoint location. When the
15470 tracepoint is created, it is not possible, in general, to determine
15471 where the steps of a @code{while-stepping} sequence will advance the
15472 program---particularly if a conditional branch is stepped.
15475 Collection of an incompletely-initialized or partially-destroyed object
15476 may result in something that @value{GDBN} cannot display, or displays
15477 in a misleading way.
15480 When @value{GDBN} displays a pointer to character it automatically
15481 dereferences the pointer to also display characters of the string
15482 being pointed to. However, collecting the pointer during tracing does
15483 not automatically collect the string. You need to explicitly
15484 dereference the pointer and provide size information if you want to
15485 collect not only the pointer, but the memory pointed to. For example,
15486 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15490 It is not possible to collect a complete stack backtrace at a
15491 tracepoint. Instead, you may collect the registers and a few hundred
15492 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15493 (adjust to use the name of the actual stack pointer register on your
15494 target architecture, and the amount of stack you wish to capture).
15495 Then the @code{backtrace} command will show a partial backtrace when
15496 using a trace frame. The number of stack frames that can be examined
15497 depends on the sizes of the frames in the collected stack. Note that
15498 if you ask for a block so large that it goes past the bottom of the
15499 stack, the target agent may report an error trying to read from an
15503 If you do not collect registers at a tracepoint, @value{GDBN} can
15504 infer that the value of @code{$pc} must be the same as the address of
15505 the tracepoint and use that when you are looking at a trace frame
15506 for that tracepoint. However, this cannot work if the tracepoint has
15507 multiple locations (for instance if it was set in a function that was
15508 inlined), or if it has a @code{while-stepping} loop. In those cases
15509 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15514 @node Analyze Collected Data
15515 @section Using the Collected Data
15517 After the tracepoint experiment ends, you use @value{GDBN} commands
15518 for examining the trace data. The basic idea is that each tracepoint
15519 collects a trace @dfn{snapshot} every time it is hit and another
15520 snapshot every time it single-steps. All these snapshots are
15521 consecutively numbered from zero and go into a buffer, and you can
15522 examine them later. The way you examine them is to @dfn{focus} on a
15523 specific trace snapshot. When the remote stub is focused on a trace
15524 snapshot, it will respond to all @value{GDBN} requests for memory and
15525 registers by reading from the buffer which belongs to that snapshot,
15526 rather than from @emph{real} memory or registers of the program being
15527 debugged. This means that @strong{all} @value{GDBN} commands
15528 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15529 behave as if we were currently debugging the program state as it was
15530 when the tracepoint occurred. Any requests for data that are not in
15531 the buffer will fail.
15534 * tfind:: How to select a trace snapshot
15535 * tdump:: How to display all data for a snapshot
15536 * save tracepoints:: How to save tracepoints for a future run
15540 @subsection @code{tfind @var{n}}
15543 @cindex select trace snapshot
15544 @cindex find trace snapshot
15545 The basic command for selecting a trace snapshot from the buffer is
15546 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15547 counting from zero. If no argument @var{n} is given, the next
15548 snapshot is selected.
15550 Here are the various forms of using the @code{tfind} command.
15554 Find the first snapshot in the buffer. This is a synonym for
15555 @code{tfind 0} (since 0 is the number of the first snapshot).
15558 Stop debugging trace snapshots, resume @emph{live} debugging.
15561 Same as @samp{tfind none}.
15564 No argument means find the next trace snapshot or find the first
15565 one if no trace snapshot is selected.
15568 Find the previous trace snapshot before the current one. This permits
15569 retracing earlier steps.
15571 @item tfind tracepoint @var{num}
15572 Find the next snapshot associated with tracepoint @var{num}. Search
15573 proceeds forward from the last examined trace snapshot. If no
15574 argument @var{num} is given, it means find the next snapshot collected
15575 for the same tracepoint as the current snapshot.
15577 @item tfind pc @var{addr}
15578 Find the next snapshot associated with the value @var{addr} of the
15579 program counter. Search proceeds forward from the last examined trace
15580 snapshot. If no argument @var{addr} is given, it means find the next
15581 snapshot with the same value of PC as the current snapshot.
15583 @item tfind outside @var{addr1}, @var{addr2}
15584 Find the next snapshot whose PC is outside the given range of
15585 addresses (exclusive).
15587 @item tfind range @var{addr1}, @var{addr2}
15588 Find the next snapshot whose PC is between @var{addr1} and
15589 @var{addr2} (inclusive).
15591 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15592 Find the next snapshot associated with the source line @var{n}. If
15593 the optional argument @var{file} is given, refer to line @var{n} in
15594 that source file. Search proceeds forward from the last examined
15595 trace snapshot. If no argument @var{n} is given, it means find the
15596 next line other than the one currently being examined; thus saying
15597 @code{tfind line} repeatedly can appear to have the same effect as
15598 stepping from line to line in a @emph{live} debugging session.
15601 The default arguments for the @code{tfind} commands are specifically
15602 designed to make it easy to scan through the trace buffer. For
15603 instance, @code{tfind} with no argument selects the next trace
15604 snapshot, and @code{tfind -} with no argument selects the previous
15605 trace snapshot. So, by giving one @code{tfind} command, and then
15606 simply hitting @key{RET} repeatedly you can examine all the trace
15607 snapshots in order. Or, by saying @code{tfind -} and then hitting
15608 @key{RET} repeatedly you can examine the snapshots in reverse order.
15609 The @code{tfind line} command with no argument selects the snapshot
15610 for the next source line executed. The @code{tfind pc} command with
15611 no argument selects the next snapshot with the same program counter
15612 (PC) as the current frame. The @code{tfind tracepoint} command with
15613 no argument selects the next trace snapshot collected by the same
15614 tracepoint as the current one.
15616 In addition to letting you scan through the trace buffer manually,
15617 these commands make it easy to construct @value{GDBN} scripts that
15618 scan through the trace buffer and print out whatever collected data
15619 you are interested in. Thus, if we want to examine the PC, FP, and SP
15620 registers from each trace frame in the buffer, we can say this:
15623 (@value{GDBP}) @b{tfind start}
15624 (@value{GDBP}) @b{while ($trace_frame != -1)}
15625 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15626 $trace_frame, $pc, $sp, $fp
15630 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15631 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15632 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15633 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15634 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15635 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15636 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15637 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15638 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15639 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15640 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15643 Or, if we want to examine the variable @code{X} at each source line in
15647 (@value{GDBP}) @b{tfind start}
15648 (@value{GDBP}) @b{while ($trace_frame != -1)}
15649 > printf "Frame %d, X == %d\n", $trace_frame, X
15659 @subsection @code{tdump}
15661 @cindex dump all data collected at tracepoint
15662 @cindex tracepoint data, display
15664 This command takes no arguments. It prints all the data collected at
15665 the current trace snapshot.
15668 (@value{GDBP}) @b{trace 444}
15669 (@value{GDBP}) @b{actions}
15670 Enter actions for tracepoint #2, one per line:
15671 > collect $regs, $locals, $args, gdb_long_test
15674 (@value{GDBP}) @b{tstart}
15676 (@value{GDBP}) @b{tfind line 444}
15677 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15679 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15681 (@value{GDBP}) @b{tdump}
15682 Data collected at tracepoint 2, trace frame 1:
15683 d0 0xc4aa0085 -995491707
15687 d4 0x71aea3d 119204413
15690 d7 0x380035 3670069
15691 a0 0x19e24a 1696330
15692 a1 0x3000668 50333288
15694 a3 0x322000 3284992
15695 a4 0x3000698 50333336
15696 a5 0x1ad3cc 1758156
15697 fp 0x30bf3c 0x30bf3c
15698 sp 0x30bf34 0x30bf34
15700 pc 0x20b2c8 0x20b2c8
15704 p = 0x20e5b4 "gdb-test"
15711 gdb_long_test = 17 '\021'
15716 @code{tdump} works by scanning the tracepoint's current collection
15717 actions and printing the value of each expression listed. So
15718 @code{tdump} can fail, if after a run, you change the tracepoint's
15719 actions to mention variables that were not collected during the run.
15721 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15722 uses the collected value of @code{$pc} to distinguish between trace
15723 frames that were collected at the tracepoint hit, and frames that were
15724 collected while stepping. This allows it to correctly choose whether
15725 to display the basic list of collections, or the collections from the
15726 body of the while-stepping loop. However, if @code{$pc} was not collected,
15727 then @code{tdump} will always attempt to dump using the basic collection
15728 list, and may fail if a while-stepping frame does not include all the
15729 same data that is collected at the tracepoint hit.
15730 @c This is getting pretty arcane, example would be good.
15732 @node save tracepoints
15733 @subsection @code{save tracepoints @var{filename}}
15734 @kindex save tracepoints
15735 @kindex save-tracepoints
15736 @cindex save tracepoints for future sessions
15738 This command saves all current tracepoint definitions together with
15739 their actions and passcounts, into a file @file{@var{filename}}
15740 suitable for use in a later debugging session. To read the saved
15741 tracepoint definitions, use the @code{source} command (@pxref{Command
15742 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15743 alias for @w{@code{save tracepoints}}
15745 @node Tracepoint Variables
15746 @section Convenience Variables for Tracepoints
15747 @cindex tracepoint variables
15748 @cindex convenience variables for tracepoints
15751 @vindex $trace_frame
15752 @item (int) $trace_frame
15753 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15754 snapshot is selected.
15756 @vindex $tracepoint
15757 @item (int) $tracepoint
15758 The tracepoint for the current trace snapshot.
15760 @vindex $trace_line
15761 @item (int) $trace_line
15762 The line number for the current trace snapshot.
15764 @vindex $trace_file
15765 @item (char []) $trace_file
15766 The source file for the current trace snapshot.
15768 @vindex $trace_func
15769 @item (char []) $trace_func
15770 The name of the function containing @code{$tracepoint}.
15773 Note: @code{$trace_file} is not suitable for use in @code{printf},
15774 use @code{output} instead.
15776 Here's a simple example of using these convenience variables for
15777 stepping through all the trace snapshots and printing some of their
15778 data. Note that these are not the same as trace state variables,
15779 which are managed by the target.
15782 (@value{GDBP}) @b{tfind start}
15784 (@value{GDBP}) @b{while $trace_frame != -1}
15785 > output $trace_file
15786 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15792 @section Using Trace Files
15793 @cindex trace files
15795 In some situations, the target running a trace experiment may no
15796 longer be available; perhaps it crashed, or the hardware was needed
15797 for a different activity. To handle these cases, you can arrange to
15798 dump the trace data into a file, and later use that file as a source
15799 of trace data, via the @code{target tfile} command.
15804 @item tsave [ -r ] @var{filename}
15805 @itemx tsave [-ctf] @var{dirname}
15806 Save the trace data to @var{filename}. By default, this command
15807 assumes that @var{filename} refers to the host filesystem, so if
15808 necessary @value{GDBN} will copy raw trace data up from the target and
15809 then save it. If the target supports it, you can also supply the
15810 optional argument @code{-r} (``remote'') to direct the target to save
15811 the data directly into @var{filename} in its own filesystem, which may be
15812 more efficient if the trace buffer is very large. (Note, however, that
15813 @code{target tfile} can only read from files accessible to the host.)
15814 By default, this command will save trace frame in tfile format.
15815 You can supply the optional argument @code{-ctf} to save data in CTF
15816 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15817 that can be shared by multiple debugging and tracing tools. Please go to
15818 @indicateurl{http://www.efficios.com/ctf} to get more information.
15820 @kindex target tfile
15824 @item target tfile @var{filename}
15825 @itemx target ctf @var{dirname}
15826 Use the file named @var{filename} or directory named @var{dirname} as
15827 a source of trace data. Commands that examine data work as they do with
15828 a live target, but it is not possible to run any new trace experiments.
15829 @code{tstatus} will report the state of the trace run at the moment
15830 the data was saved, as well as the current trace frame you are examining.
15831 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15835 (@value{GDBP}) target ctf ctf.ctf
15836 (@value{GDBP}) tfind
15837 Found trace frame 0, tracepoint 2
15838 39 ++a; /* set tracepoint 1 here */
15839 (@value{GDBP}) tdump
15840 Data collected at tracepoint 2, trace frame 0:
15844 c = @{"123", "456", "789", "123", "456", "789"@}
15845 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15853 @chapter Debugging Programs That Use Overlays
15856 If your program is too large to fit completely in your target system's
15857 memory, you can sometimes use @dfn{overlays} to work around this
15858 problem. @value{GDBN} provides some support for debugging programs that
15862 * How Overlays Work:: A general explanation of overlays.
15863 * Overlay Commands:: Managing overlays in @value{GDBN}.
15864 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15865 mapped by asking the inferior.
15866 * Overlay Sample Program:: A sample program using overlays.
15869 @node How Overlays Work
15870 @section How Overlays Work
15871 @cindex mapped overlays
15872 @cindex unmapped overlays
15873 @cindex load address, overlay's
15874 @cindex mapped address
15875 @cindex overlay area
15877 Suppose you have a computer whose instruction address space is only 64
15878 kilobytes long, but which has much more memory which can be accessed by
15879 other means: special instructions, segment registers, or memory
15880 management hardware, for example. Suppose further that you want to
15881 adapt a program which is larger than 64 kilobytes to run on this system.
15883 One solution is to identify modules of your program which are relatively
15884 independent, and need not call each other directly; call these modules
15885 @dfn{overlays}. Separate the overlays from the main program, and place
15886 their machine code in the larger memory. Place your main program in
15887 instruction memory, but leave at least enough space there to hold the
15888 largest overlay as well.
15890 Now, to call a function located in an overlay, you must first copy that
15891 overlay's machine code from the large memory into the space set aside
15892 for it in the instruction memory, and then jump to its entry point
15895 @c NB: In the below the mapped area's size is greater or equal to the
15896 @c size of all overlays. This is intentional to remind the developer
15897 @c that overlays don't necessarily need to be the same size.
15901 Data Instruction Larger
15902 Address Space Address Space Address Space
15903 +-----------+ +-----------+ +-----------+
15905 +-----------+ +-----------+ +-----------+<-- overlay 1
15906 | program | | main | .----| overlay 1 | load address
15907 | variables | | program | | +-----------+
15908 | and heap | | | | | |
15909 +-----------+ | | | +-----------+<-- overlay 2
15910 | | +-----------+ | | | load address
15911 +-----------+ | | | .-| overlay 2 |
15913 mapped --->+-----------+ | | +-----------+
15914 address | | | | | |
15915 | overlay | <-' | | |
15916 | area | <---' +-----------+<-- overlay 3
15917 | | <---. | | load address
15918 +-----------+ `--| overlay 3 |
15925 @anchor{A code overlay}A code overlay
15929 The diagram (@pxref{A code overlay}) shows a system with separate data
15930 and instruction address spaces. To map an overlay, the program copies
15931 its code from the larger address space to the instruction address space.
15932 Since the overlays shown here all use the same mapped address, only one
15933 may be mapped at a time. For a system with a single address space for
15934 data and instructions, the diagram would be similar, except that the
15935 program variables and heap would share an address space with the main
15936 program and the overlay area.
15938 An overlay loaded into instruction memory and ready for use is called a
15939 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15940 instruction memory. An overlay not present (or only partially present)
15941 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15942 is its address in the larger memory. The mapped address is also called
15943 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15944 called the @dfn{load memory address}, or @dfn{LMA}.
15946 Unfortunately, overlays are not a completely transparent way to adapt a
15947 program to limited instruction memory. They introduce a new set of
15948 global constraints you must keep in mind as you design your program:
15953 Before calling or returning to a function in an overlay, your program
15954 must make sure that overlay is actually mapped. Otherwise, the call or
15955 return will transfer control to the right address, but in the wrong
15956 overlay, and your program will probably crash.
15959 If the process of mapping an overlay is expensive on your system, you
15960 will need to choose your overlays carefully to minimize their effect on
15961 your program's performance.
15964 The executable file you load onto your system must contain each
15965 overlay's instructions, appearing at the overlay's load address, not its
15966 mapped address. However, each overlay's instructions must be relocated
15967 and its symbols defined as if the overlay were at its mapped address.
15968 You can use GNU linker scripts to specify different load and relocation
15969 addresses for pieces of your program; see @ref{Overlay Description,,,
15970 ld.info, Using ld: the GNU linker}.
15973 The procedure for loading executable files onto your system must be able
15974 to load their contents into the larger address space as well as the
15975 instruction and data spaces.
15979 The overlay system described above is rather simple, and could be
15980 improved in many ways:
15985 If your system has suitable bank switch registers or memory management
15986 hardware, you could use those facilities to make an overlay's load area
15987 contents simply appear at their mapped address in instruction space.
15988 This would probably be faster than copying the overlay to its mapped
15989 area in the usual way.
15992 If your overlays are small enough, you could set aside more than one
15993 overlay area, and have more than one overlay mapped at a time.
15996 You can use overlays to manage data, as well as instructions. In
15997 general, data overlays are even less transparent to your design than
15998 code overlays: whereas code overlays only require care when you call or
15999 return to functions, data overlays require care every time you access
16000 the data. Also, if you change the contents of a data overlay, you
16001 must copy its contents back out to its load address before you can copy a
16002 different data overlay into the same mapped area.
16007 @node Overlay Commands
16008 @section Overlay Commands
16010 To use @value{GDBN}'s overlay support, each overlay in your program must
16011 correspond to a separate section of the executable file. The section's
16012 virtual memory address and load memory address must be the overlay's
16013 mapped and load addresses. Identifying overlays with sections allows
16014 @value{GDBN} to determine the appropriate address of a function or
16015 variable, depending on whether the overlay is mapped or not.
16017 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16018 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16023 Disable @value{GDBN}'s overlay support. When overlay support is
16024 disabled, @value{GDBN} assumes that all functions and variables are
16025 always present at their mapped addresses. By default, @value{GDBN}'s
16026 overlay support is disabled.
16028 @item overlay manual
16029 @cindex manual overlay debugging
16030 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16031 relies on you to tell it which overlays are mapped, and which are not,
16032 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16033 commands described below.
16035 @item overlay map-overlay @var{overlay}
16036 @itemx overlay map @var{overlay}
16037 @cindex map an overlay
16038 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16039 be the name of the object file section containing the overlay. When an
16040 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16041 functions and variables at their mapped addresses. @value{GDBN} assumes
16042 that any other overlays whose mapped ranges overlap that of
16043 @var{overlay} are now unmapped.
16045 @item overlay unmap-overlay @var{overlay}
16046 @itemx overlay unmap @var{overlay}
16047 @cindex unmap an overlay
16048 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16049 must be the name of the object file section containing the overlay.
16050 When an overlay is unmapped, @value{GDBN} assumes it can find the
16051 overlay's functions and variables at their load addresses.
16054 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16055 consults a data structure the overlay manager maintains in the inferior
16056 to see which overlays are mapped. For details, see @ref{Automatic
16057 Overlay Debugging}.
16059 @item overlay load-target
16060 @itemx overlay load
16061 @cindex reloading the overlay table
16062 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16063 re-reads the table @value{GDBN} automatically each time the inferior
16064 stops, so this command should only be necessary if you have changed the
16065 overlay mapping yourself using @value{GDBN}. This command is only
16066 useful when using automatic overlay debugging.
16068 @item overlay list-overlays
16069 @itemx overlay list
16070 @cindex listing mapped overlays
16071 Display a list of the overlays currently mapped, along with their mapped
16072 addresses, load addresses, and sizes.
16076 Normally, when @value{GDBN} prints a code address, it includes the name
16077 of the function the address falls in:
16080 (@value{GDBP}) print main
16081 $3 = @{int ()@} 0x11a0 <main>
16084 When overlay debugging is enabled, @value{GDBN} recognizes code in
16085 unmapped overlays, and prints the names of unmapped functions with
16086 asterisks around them. For example, if @code{foo} is a function in an
16087 unmapped overlay, @value{GDBN} prints it this way:
16090 (@value{GDBP}) overlay list
16091 No sections are mapped.
16092 (@value{GDBP}) print foo
16093 $5 = @{int (int)@} 0x100000 <*foo*>
16096 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16100 (@value{GDBP}) overlay list
16101 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16102 mapped at 0x1016 - 0x104a
16103 (@value{GDBP}) print foo
16104 $6 = @{int (int)@} 0x1016 <foo>
16107 When overlay debugging is enabled, @value{GDBN} can find the correct
16108 address for functions and variables in an overlay, whether or not the
16109 overlay is mapped. This allows most @value{GDBN} commands, like
16110 @code{break} and @code{disassemble}, to work normally, even on unmapped
16111 code. However, @value{GDBN}'s breakpoint support has some limitations:
16115 @cindex breakpoints in overlays
16116 @cindex overlays, setting breakpoints in
16117 You can set breakpoints in functions in unmapped overlays, as long as
16118 @value{GDBN} can write to the overlay at its load address.
16120 @value{GDBN} can not set hardware or simulator-based breakpoints in
16121 unmapped overlays. However, if you set a breakpoint at the end of your
16122 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16123 you are using manual overlay management), @value{GDBN} will re-set its
16124 breakpoints properly.
16128 @node Automatic Overlay Debugging
16129 @section Automatic Overlay Debugging
16130 @cindex automatic overlay debugging
16132 @value{GDBN} can automatically track which overlays are mapped and which
16133 are not, given some simple co-operation from the overlay manager in the
16134 inferior. If you enable automatic overlay debugging with the
16135 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16136 looks in the inferior's memory for certain variables describing the
16137 current state of the overlays.
16139 Here are the variables your overlay manager must define to support
16140 @value{GDBN}'s automatic overlay debugging:
16144 @item @code{_ovly_table}:
16145 This variable must be an array of the following structures:
16150 /* The overlay's mapped address. */
16153 /* The size of the overlay, in bytes. */
16154 unsigned long size;
16156 /* The overlay's load address. */
16159 /* Non-zero if the overlay is currently mapped;
16161 unsigned long mapped;
16165 @item @code{_novlys}:
16166 This variable must be a four-byte signed integer, holding the total
16167 number of elements in @code{_ovly_table}.
16171 To decide whether a particular overlay is mapped or not, @value{GDBN}
16172 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16173 @code{lma} members equal the VMA and LMA of the overlay's section in the
16174 executable file. When @value{GDBN} finds a matching entry, it consults
16175 the entry's @code{mapped} member to determine whether the overlay is
16178 In addition, your overlay manager may define a function called
16179 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16180 will silently set a breakpoint there. If the overlay manager then
16181 calls this function whenever it has changed the overlay table, this
16182 will enable @value{GDBN} to accurately keep track of which overlays
16183 are in program memory, and update any breakpoints that may be set
16184 in overlays. This will allow breakpoints to work even if the
16185 overlays are kept in ROM or other non-writable memory while they
16186 are not being executed.
16188 @node Overlay Sample Program
16189 @section Overlay Sample Program
16190 @cindex overlay example program
16192 When linking a program which uses overlays, you must place the overlays
16193 at their load addresses, while relocating them to run at their mapped
16194 addresses. To do this, you must write a linker script (@pxref{Overlay
16195 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16196 since linker scripts are specific to a particular host system, target
16197 architecture, and target memory layout, this manual cannot provide
16198 portable sample code demonstrating @value{GDBN}'s overlay support.
16200 However, the @value{GDBN} source distribution does contain an overlaid
16201 program, with linker scripts for a few systems, as part of its test
16202 suite. The program consists of the following files from
16203 @file{gdb/testsuite/gdb.base}:
16207 The main program file.
16209 A simple overlay manager, used by @file{overlays.c}.
16214 Overlay modules, loaded and used by @file{overlays.c}.
16217 Linker scripts for linking the test program on the @code{d10v-elf}
16218 and @code{m32r-elf} targets.
16221 You can build the test program using the @code{d10v-elf} GCC
16222 cross-compiler like this:
16225 $ d10v-elf-gcc -g -c overlays.c
16226 $ d10v-elf-gcc -g -c ovlymgr.c
16227 $ d10v-elf-gcc -g -c foo.c
16228 $ d10v-elf-gcc -g -c bar.c
16229 $ d10v-elf-gcc -g -c baz.c
16230 $ d10v-elf-gcc -g -c grbx.c
16231 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16232 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16235 The build process is identical for any other architecture, except that
16236 you must substitute the appropriate compiler and linker script for the
16237 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16241 @chapter Using @value{GDBN} with Different Languages
16244 Although programming languages generally have common aspects, they are
16245 rarely expressed in the same manner. For instance, in ANSI C,
16246 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16247 Modula-2, it is accomplished by @code{p^}. Values can also be
16248 represented (and displayed) differently. Hex numbers in C appear as
16249 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16251 @cindex working language
16252 Language-specific information is built into @value{GDBN} for some languages,
16253 allowing you to express operations like the above in your program's
16254 native language, and allowing @value{GDBN} to output values in a manner
16255 consistent with the syntax of your program's native language. The
16256 language you use to build expressions is called the @dfn{working
16260 * Setting:: Switching between source languages
16261 * Show:: Displaying the language
16262 * Checks:: Type and range checks
16263 * Supported Languages:: Supported languages
16264 * Unsupported Languages:: Unsupported languages
16268 @section Switching Between Source Languages
16270 There are two ways to control the working language---either have @value{GDBN}
16271 set it automatically, or select it manually yourself. You can use the
16272 @code{set language} command for either purpose. On startup, @value{GDBN}
16273 defaults to setting the language automatically. The working language is
16274 used to determine how expressions you type are interpreted, how values
16277 In addition to the working language, every source file that
16278 @value{GDBN} knows about has its own working language. For some object
16279 file formats, the compiler might indicate which language a particular
16280 source file is in. However, most of the time @value{GDBN} infers the
16281 language from the name of the file. The language of a source file
16282 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16283 show each frame appropriately for its own language. There is no way to
16284 set the language of a source file from within @value{GDBN}, but you can
16285 set the language associated with a filename extension. @xref{Show, ,
16286 Displaying the Language}.
16288 This is most commonly a problem when you use a program, such
16289 as @code{cfront} or @code{f2c}, that generates C but is written in
16290 another language. In that case, make the
16291 program use @code{#line} directives in its C output; that way
16292 @value{GDBN} will know the correct language of the source code of the original
16293 program, and will display that source code, not the generated C code.
16296 * Filenames:: Filename extensions and languages.
16297 * Manually:: Setting the working language manually
16298 * Automatically:: Having @value{GDBN} infer the source language
16302 @subsection List of Filename Extensions and Languages
16304 If a source file name ends in one of the following extensions, then
16305 @value{GDBN} infers that its language is the one indicated.
16323 C@t{++} source file
16329 Objective-C source file
16333 Fortran source file
16336 Modula-2 source file
16340 Assembler source file. This actually behaves almost like C, but
16341 @value{GDBN} does not skip over function prologues when stepping.
16344 In addition, you may set the language associated with a filename
16345 extension. @xref{Show, , Displaying the Language}.
16348 @subsection Setting the Working Language
16350 If you allow @value{GDBN} to set the language automatically,
16351 expressions are interpreted the same way in your debugging session and
16354 @kindex set language
16355 If you wish, you may set the language manually. To do this, issue the
16356 command @samp{set language @var{lang}}, where @var{lang} is the name of
16357 a language, such as
16358 @code{c} or @code{modula-2}.
16359 For a list of the supported languages, type @samp{set language}.
16361 Setting the language manually prevents @value{GDBN} from updating the working
16362 language automatically. This can lead to confusion if you try
16363 to debug a program when the working language is not the same as the
16364 source language, when an expression is acceptable to both
16365 languages---but means different things. For instance, if the current
16366 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16374 might not have the effect you intended. In C, this means to add
16375 @code{b} and @code{c} and place the result in @code{a}. The result
16376 printed would be the value of @code{a}. In Modula-2, this means to compare
16377 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16379 @node Automatically
16380 @subsection Having @value{GDBN} Infer the Source Language
16382 To have @value{GDBN} set the working language automatically, use
16383 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16384 then infers the working language. That is, when your program stops in a
16385 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16386 working language to the language recorded for the function in that
16387 frame. If the language for a frame is unknown (that is, if the function
16388 or block corresponding to the frame was defined in a source file that
16389 does not have a recognized extension), the current working language is
16390 not changed, and @value{GDBN} issues a warning.
16392 This may not seem necessary for most programs, which are written
16393 entirely in one source language. However, program modules and libraries
16394 written in one source language can be used by a main program written in
16395 a different source language. Using @samp{set language auto} in this
16396 case frees you from having to set the working language manually.
16399 @section Displaying the Language
16401 The following commands help you find out which language is the
16402 working language, and also what language source files were written in.
16405 @item show language
16406 @anchor{show language}
16407 @kindex show language
16408 Display the current working language. This is the
16409 language you can use with commands such as @code{print} to
16410 build and compute expressions that may involve variables in your program.
16413 @kindex info frame@r{, show the source language}
16414 Display the source language for this frame. This language becomes the
16415 working language if you use an identifier from this frame.
16416 @xref{Frame Info, ,Information about a Frame}, to identify the other
16417 information listed here.
16420 @kindex info source@r{, show the source language}
16421 Display the source language of this source file.
16422 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16423 information listed here.
16426 In unusual circumstances, you may have source files with extensions
16427 not in the standard list. You can then set the extension associated
16428 with a language explicitly:
16431 @item set extension-language @var{ext} @var{language}
16432 @kindex set extension-language
16433 Tell @value{GDBN} that source files with extension @var{ext} are to be
16434 assumed as written in the source language @var{language}.
16436 @item info extensions
16437 @kindex info extensions
16438 List all the filename extensions and the associated languages.
16442 @section Type and Range Checking
16444 Some languages are designed to guard you against making seemingly common
16445 errors through a series of compile- and run-time checks. These include
16446 checking the type of arguments to functions and operators and making
16447 sure mathematical overflows are caught at run time. Checks such as
16448 these help to ensure a program's correctness once it has been compiled
16449 by eliminating type mismatches and providing active checks for range
16450 errors when your program is running.
16452 By default @value{GDBN} checks for these errors according to the
16453 rules of the current source language. Although @value{GDBN} does not check
16454 the statements in your program, it can check expressions entered directly
16455 into @value{GDBN} for evaluation via the @code{print} command, for example.
16458 * Type Checking:: An overview of type checking
16459 * Range Checking:: An overview of range checking
16462 @cindex type checking
16463 @cindex checks, type
16464 @node Type Checking
16465 @subsection An Overview of Type Checking
16467 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16468 arguments to operators and functions have to be of the correct type,
16469 otherwise an error occurs. These checks prevent type mismatch
16470 errors from ever causing any run-time problems. For example,
16473 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16475 (@value{GDBP}) print obj.my_method (0)
16478 (@value{GDBP}) print obj.my_method (0x1234)
16479 Cannot resolve method klass::my_method to any overloaded instance
16482 The second example fails because in C@t{++} the integer constant
16483 @samp{0x1234} is not type-compatible with the pointer parameter type.
16485 For the expressions you use in @value{GDBN} commands, you can tell
16486 @value{GDBN} to not enforce strict type checking or
16487 to treat any mismatches as errors and abandon the expression;
16488 When type checking is disabled, @value{GDBN} successfully evaluates
16489 expressions like the second example above.
16491 Even if type checking is off, there may be other reasons
16492 related to type that prevent @value{GDBN} from evaluating an expression.
16493 For instance, @value{GDBN} does not know how to add an @code{int} and
16494 a @code{struct foo}. These particular type errors have nothing to do
16495 with the language in use and usually arise from expressions which make
16496 little sense to evaluate anyway.
16498 @value{GDBN} provides some additional commands for controlling type checking:
16500 @kindex set check type
16501 @kindex show check type
16503 @item set check type on
16504 @itemx set check type off
16505 Set strict type checking on or off. If any type mismatches occur in
16506 evaluating an expression while type checking is on, @value{GDBN} prints a
16507 message and aborts evaluation of the expression.
16509 @item show check type
16510 Show the current setting of type checking and whether @value{GDBN}
16511 is enforcing strict type checking rules.
16514 @cindex range checking
16515 @cindex checks, range
16516 @node Range Checking
16517 @subsection An Overview of Range Checking
16519 In some languages (such as Modula-2), it is an error to exceed the
16520 bounds of a type; this is enforced with run-time checks. Such range
16521 checking is meant to ensure program correctness by making sure
16522 computations do not overflow, or indices on an array element access do
16523 not exceed the bounds of the array.
16525 For expressions you use in @value{GDBN} commands, you can tell
16526 @value{GDBN} to treat range errors in one of three ways: ignore them,
16527 always treat them as errors and abandon the expression, or issue
16528 warnings but evaluate the expression anyway.
16530 A range error can result from numerical overflow, from exceeding an
16531 array index bound, or when you type a constant that is not a member
16532 of any type. Some languages, however, do not treat overflows as an
16533 error. In many implementations of C, mathematical overflow causes the
16534 result to ``wrap around'' to lower values---for example, if @var{m} is
16535 the largest integer value, and @var{s} is the smallest, then
16538 @var{m} + 1 @result{} @var{s}
16541 This, too, is specific to individual languages, and in some cases
16542 specific to individual compilers or machines. @xref{Supported Languages, ,
16543 Supported Languages}, for further details on specific languages.
16545 @value{GDBN} provides some additional commands for controlling the range checker:
16547 @kindex set check range
16548 @kindex show check range
16550 @item set check range auto
16551 Set range checking on or off based on the current working language.
16552 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16555 @item set check range on
16556 @itemx set check range off
16557 Set range checking on or off, overriding the default setting for the
16558 current working language. A warning is issued if the setting does not
16559 match the language default. If a range error occurs and range checking is on,
16560 then a message is printed and evaluation of the expression is aborted.
16562 @item set check range warn
16563 Output messages when the @value{GDBN} range checker detects a range error,
16564 but attempt to evaluate the expression anyway. Evaluating the
16565 expression may still be impossible for other reasons, such as accessing
16566 memory that the process does not own (a typical example from many Unix
16569 @item show check range
16570 Show the current setting of the range checker, and whether or not it is
16571 being set automatically by @value{GDBN}.
16574 @node Supported Languages
16575 @section Supported Languages
16577 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16578 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16579 @c This is false ...
16580 Some @value{GDBN} features may be used in expressions regardless of the
16581 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16582 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16583 ,Expressions}) can be used with the constructs of any supported
16586 The following sections detail to what degree each source language is
16587 supported by @value{GDBN}. These sections are not meant to be language
16588 tutorials or references, but serve only as a reference guide to what the
16589 @value{GDBN} expression parser accepts, and what input and output
16590 formats should look like for different languages. There are many good
16591 books written on each of these languages; please look to these for a
16592 language reference or tutorial.
16595 * C:: C and C@t{++}
16598 * Objective-C:: Objective-C
16599 * OpenCL C:: OpenCL C
16600 * Fortran:: Fortran
16603 * Modula-2:: Modula-2
16608 @subsection C and C@t{++}
16610 @cindex C and C@t{++}
16611 @cindex expressions in C or C@t{++}
16613 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16614 to both languages. Whenever this is the case, we discuss those languages
16618 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16619 @cindex @sc{gnu} C@t{++}
16620 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16621 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16622 effectively, you must compile your C@t{++} programs with a supported
16623 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16624 compiler (@code{aCC}).
16627 * C Operators:: C and C@t{++} operators
16628 * C Constants:: C and C@t{++} constants
16629 * C Plus Plus Expressions:: C@t{++} expressions
16630 * C Defaults:: Default settings for C and C@t{++}
16631 * C Checks:: C and C@t{++} type and range checks
16632 * Debugging C:: @value{GDBN} and C
16633 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16634 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16638 @subsubsection C and C@t{++} Operators
16640 @cindex C and C@t{++} operators
16642 Operators must be defined on values of specific types. For instance,
16643 @code{+} is defined on numbers, but not on structures. Operators are
16644 often defined on groups of types.
16646 For the purposes of C and C@t{++}, the following definitions hold:
16651 @emph{Integral types} include @code{int} with any of its storage-class
16652 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16655 @emph{Floating-point types} include @code{float}, @code{double}, and
16656 @code{long double} (if supported by the target platform).
16659 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16662 @emph{Scalar types} include all of the above.
16667 The following operators are supported. They are listed here
16668 in order of increasing precedence:
16672 The comma or sequencing operator. Expressions in a comma-separated list
16673 are evaluated from left to right, with the result of the entire
16674 expression being the last expression evaluated.
16677 Assignment. The value of an assignment expression is the value
16678 assigned. Defined on scalar types.
16681 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16682 and translated to @w{@code{@var{a} = @var{a op b}}}.
16683 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16684 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16685 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16688 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16689 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16690 should be of an integral type.
16693 Logical @sc{or}. Defined on integral types.
16696 Logical @sc{and}. Defined on integral types.
16699 Bitwise @sc{or}. Defined on integral types.
16702 Bitwise exclusive-@sc{or}. Defined on integral types.
16705 Bitwise @sc{and}. Defined on integral types.
16708 Equality and inequality. Defined on scalar types. The value of these
16709 expressions is 0 for false and non-zero for true.
16711 @item <@r{, }>@r{, }<=@r{, }>=
16712 Less than, greater than, less than or equal, greater than or equal.
16713 Defined on scalar types. The value of these expressions is 0 for false
16714 and non-zero for true.
16717 left shift, and right shift. Defined on integral types.
16720 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16723 Addition and subtraction. Defined on integral types, floating-point types and
16726 @item *@r{, }/@r{, }%
16727 Multiplication, division, and modulus. Multiplication and division are
16728 defined on integral and floating-point types. Modulus is defined on
16732 Increment and decrement. When appearing before a variable, the
16733 operation is performed before the variable is used in an expression;
16734 when appearing after it, the variable's value is used before the
16735 operation takes place.
16738 Pointer dereferencing. Defined on pointer types. Same precedence as
16742 Address operator. Defined on variables. Same precedence as @code{++}.
16744 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16745 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16746 to examine the address
16747 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16751 Negative. Defined on integral and floating-point types. Same
16752 precedence as @code{++}.
16755 Logical negation. Defined on integral types. Same precedence as
16759 Bitwise complement operator. Defined on integral types. Same precedence as
16764 Structure member, and pointer-to-structure member. For convenience,
16765 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16766 pointer based on the stored type information.
16767 Defined on @code{struct} and @code{union} data.
16770 Dereferences of pointers to members.
16773 Array indexing. @code{@var{a}[@var{i}]} is defined as
16774 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16777 Function parameter list. Same precedence as @code{->}.
16780 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16781 and @code{class} types.
16784 Doubled colons also represent the @value{GDBN} scope operator
16785 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16789 If an operator is redefined in the user code, @value{GDBN} usually
16790 attempts to invoke the redefined version instead of using the operator's
16791 predefined meaning.
16794 @subsubsection C and C@t{++} Constants
16796 @cindex C and C@t{++} constants
16798 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16803 Integer constants are a sequence of digits. Octal constants are
16804 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16805 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16806 @samp{l}, specifying that the constant should be treated as a
16810 Floating point constants are a sequence of digits, followed by a decimal
16811 point, followed by a sequence of digits, and optionally followed by an
16812 exponent. An exponent is of the form:
16813 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16814 sequence of digits. The @samp{+} is optional for positive exponents.
16815 A floating-point constant may also end with a letter @samp{f} or
16816 @samp{F}, specifying that the constant should be treated as being of
16817 the @code{float} (as opposed to the default @code{double}) type; or with
16818 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16822 Enumerated constants consist of enumerated identifiers, or their
16823 integral equivalents.
16826 Character constants are a single character surrounded by single quotes
16827 (@code{'}), or a number---the ordinal value of the corresponding character
16828 (usually its @sc{ascii} value). Within quotes, the single character may
16829 be represented by a letter or by @dfn{escape sequences}, which are of
16830 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16831 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16832 @samp{@var{x}} is a predefined special character---for example,
16833 @samp{\n} for newline.
16835 Wide character constants can be written by prefixing a character
16836 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16837 form of @samp{x}. The target wide character set is used when
16838 computing the value of this constant (@pxref{Character Sets}).
16841 String constants are a sequence of character constants surrounded by
16842 double quotes (@code{"}). Any valid character constant (as described
16843 above) may appear. Double quotes within the string must be preceded by
16844 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16847 Wide string constants can be written by prefixing a string constant
16848 with @samp{L}, as in C. The target wide character set is used when
16849 computing the value of this constant (@pxref{Character Sets}).
16852 Pointer constants are an integral value. You can also write pointers
16853 to constants using the C operator @samp{&}.
16856 Array constants are comma-separated lists surrounded by braces @samp{@{}
16857 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16858 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16859 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16862 @node C Plus Plus Expressions
16863 @subsubsection C@t{++} Expressions
16865 @cindex expressions in C@t{++}
16866 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16868 @cindex debugging C@t{++} programs
16869 @cindex C@t{++} compilers
16870 @cindex debug formats and C@t{++}
16871 @cindex @value{NGCC} and C@t{++}
16873 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16874 the proper compiler and the proper debug format. Currently,
16875 @value{GDBN} works best when debugging C@t{++} code that is compiled
16876 with the most recent version of @value{NGCC} possible. The DWARF
16877 debugging format is preferred; @value{NGCC} defaults to this on most
16878 popular platforms. Other compilers and/or debug formats are likely to
16879 work badly or not at all when using @value{GDBN} to debug C@t{++}
16880 code. @xref{Compilation}.
16885 @cindex member functions
16887 Member function calls are allowed; you can use expressions like
16890 count = aml->GetOriginal(x, y)
16893 @vindex this@r{, inside C@t{++} member functions}
16894 @cindex namespace in C@t{++}
16896 While a member function is active (in the selected stack frame), your
16897 expressions have the same namespace available as the member function;
16898 that is, @value{GDBN} allows implicit references to the class instance
16899 pointer @code{this} following the same rules as C@t{++}. @code{using}
16900 declarations in the current scope are also respected by @value{GDBN}.
16902 @cindex call overloaded functions
16903 @cindex overloaded functions, calling
16904 @cindex type conversions in C@t{++}
16906 You can call overloaded functions; @value{GDBN} resolves the function
16907 call to the right definition, with some restrictions. @value{GDBN} does not
16908 perform overload resolution involving user-defined type conversions,
16909 calls to constructors, or instantiations of templates that do not exist
16910 in the program. It also cannot handle ellipsis argument lists or
16913 It does perform integral conversions and promotions, floating-point
16914 promotions, arithmetic conversions, pointer conversions, conversions of
16915 class objects to base classes, and standard conversions such as those of
16916 functions or arrays to pointers; it requires an exact match on the
16917 number of function arguments.
16919 Overload resolution is always performed, unless you have specified
16920 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16921 ,@value{GDBN} Features for C@t{++}}.
16923 You must specify @code{set overload-resolution off} in order to use an
16924 explicit function signature to call an overloaded function, as in
16926 p 'foo(char,int)'('x', 13)
16929 The @value{GDBN} command-completion facility can simplify this;
16930 see @ref{Completion, ,Command Completion}.
16932 @cindex reference declarations
16934 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16935 references; you can use them in expressions just as you do in C@t{++}
16936 source---they are automatically dereferenced.
16938 In the parameter list shown when @value{GDBN} displays a frame, the values of
16939 reference variables are not displayed (unlike other variables); this
16940 avoids clutter, since references are often used for large structures.
16941 The @emph{address} of a reference variable is always shown, unless
16942 you have specified @samp{set print address off}.
16945 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16946 expressions can use it just as expressions in your program do. Since
16947 one scope may be defined in another, you can use @code{::} repeatedly if
16948 necessary, for example in an expression like
16949 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16950 resolving name scope by reference to source files, in both C and C@t{++}
16951 debugging (@pxref{Variables, ,Program Variables}).
16954 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16959 @subsubsection C and C@t{++} Defaults
16961 @cindex C and C@t{++} defaults
16963 If you allow @value{GDBN} to set range checking automatically, it
16964 defaults to @code{off} whenever the working language changes to
16965 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16966 selects the working language.
16968 If you allow @value{GDBN} to set the language automatically, it
16969 recognizes source files whose names end with @file{.c}, @file{.C}, or
16970 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16971 these files, it sets the working language to C or C@t{++}.
16972 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16973 for further details.
16976 @subsubsection C and C@t{++} Type and Range Checks
16978 @cindex C and C@t{++} checks
16980 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16981 checking is used. However, if you turn type checking off, @value{GDBN}
16982 will allow certain non-standard conversions, such as promoting integer
16983 constants to pointers.
16985 Range checking, if turned on, is done on mathematical operations. Array
16986 indices are not checked, since they are often used to index a pointer
16987 that is not itself an array.
16990 @subsubsection @value{GDBN} and C
16992 The @code{set print union} and @code{show print union} commands apply to
16993 the @code{union} type. When set to @samp{on}, any @code{union} that is
16994 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16995 appears as @samp{@{...@}}.
16997 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16998 with pointers and a memory allocation function. @xref{Expressions,
17001 @node Debugging C Plus Plus
17002 @subsubsection @value{GDBN} Features for C@t{++}
17004 @cindex commands for C@t{++}
17006 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
17007 designed specifically for use with C@t{++}. Here is a summary:
17010 @cindex break in overloaded functions
17011 @item @r{breakpoint menus}
17012 When you want a breakpoint in a function whose name is overloaded,
17013 @value{GDBN} has the capability to display a menu of possible breakpoint
17014 locations to help you specify which function definition you want.
17015 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17017 @cindex overloading in C@t{++}
17018 @item rbreak @var{regex}
17019 Setting breakpoints using regular expressions is helpful for setting
17020 breakpoints on overloaded functions that are not members of any special
17022 @xref{Set Breaks, ,Setting Breakpoints}.
17024 @cindex C@t{++} exception handling
17026 @itemx catch rethrow
17028 Debug C@t{++} exception handling using these commands. @xref{Set
17029 Catchpoints, , Setting Catchpoints}.
17031 @cindex inheritance
17032 @item ptype @var{typename}
17033 Print inheritance relationships as well as other information for type
17035 @xref{Symbols, ,Examining the Symbol Table}.
17037 @item info vtbl @var{expression}.
17038 The @code{info vtbl} command can be used to display the virtual
17039 method tables of the object computed by @var{expression}. This shows
17040 one entry per virtual table; there may be multiple virtual tables when
17041 multiple inheritance is in use.
17043 @cindex C@t{++} demangling
17044 @item demangle @var{name}
17045 Demangle @var{name}.
17046 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17048 @cindex C@t{++} symbol display
17049 @item set print demangle
17050 @itemx show print demangle
17051 @itemx set print asm-demangle
17052 @itemx show print asm-demangle
17053 Control whether C@t{++} symbols display in their source form, both when
17054 displaying code as C@t{++} source and when displaying disassemblies.
17055 @xref{Print Settings, ,Print Settings}.
17057 @item set print object
17058 @itemx show print object
17059 Choose whether to print derived (actual) or declared types of objects.
17060 @xref{Print Settings, ,Print Settings}.
17062 @item set print vtbl
17063 @itemx show print vtbl
17064 Control the format for printing virtual function tables.
17065 @xref{Print Settings, ,Print Settings}.
17066 (The @code{vtbl} commands do not work on programs compiled with the HP
17067 ANSI C@t{++} compiler (@code{aCC}).)
17069 @kindex set overload-resolution
17070 @cindex overloaded functions, overload resolution
17071 @item set overload-resolution on
17072 Enable overload resolution for C@t{++} expression evaluation. The default
17073 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17074 and searches for a function whose signature matches the argument types,
17075 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17076 Expressions, ,C@t{++} Expressions}, for details).
17077 If it cannot find a match, it emits a message.
17079 @item set overload-resolution off
17080 Disable overload resolution for C@t{++} expression evaluation. For
17081 overloaded functions that are not class member functions, @value{GDBN}
17082 chooses the first function of the specified name that it finds in the
17083 symbol table, whether or not its arguments are of the correct type. For
17084 overloaded functions that are class member functions, @value{GDBN}
17085 searches for a function whose signature @emph{exactly} matches the
17088 @kindex show overload-resolution
17089 @item show overload-resolution
17090 Show the current setting of overload resolution.
17092 @item @r{Overloaded symbol names}
17093 You can specify a particular definition of an overloaded symbol, using
17094 the same notation that is used to declare such symbols in C@t{++}: type
17095 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17096 also use the @value{GDBN} command-line word completion facilities to list the
17097 available choices, or to finish the type list for you.
17098 @xref{Completion,, Command Completion}, for details on how to do this.
17100 @item @r{Breakpoints in template functions}
17102 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17103 template parameter lists when it encounters a symbol which includes a
17104 C@t{++} template. This permits setting breakpoints on families of template functions
17105 or functions whose parameters include template types.
17107 The @kbd{-qualified} flag may be used to override this behavior, causing
17108 @value{GDBN} to search for a specific function or type.
17110 The @value{GDBN} command-line word completion facility also understands
17111 template parameters and may be used to list available choices or finish
17112 template parameter lists for you. @xref{Completion,, Command Completion}, for
17113 details on how to do this.
17115 @item @r{Breakpoints in functions with ABI tags}
17117 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17118 correspond to changes in the ABI of a type, function, or variable that
17119 would not otherwise be reflected in a mangled name. See
17120 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17123 The ABI tags are visible in C@t{++} demangled names. For example, a
17124 function that returns a std::string:
17127 std::string function(int);
17131 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17132 tag, and @value{GDBN} displays the symbol like this:
17135 function[abi:cxx11](int)
17138 You can set a breakpoint on such functions simply as if they had no
17142 (gdb) b function(int)
17143 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17144 (gdb) info breakpoints
17145 Num Type Disp Enb Address What
17146 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17150 On the rare occasion you need to disambiguate between different ABI
17151 tags, you can do so by simply including the ABI tag in the function
17155 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17159 @node Decimal Floating Point
17160 @subsubsection Decimal Floating Point format
17161 @cindex decimal floating point format
17163 @value{GDBN} can examine, set and perform computations with numbers in
17164 decimal floating point format, which in the C language correspond to the
17165 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17166 specified by the extension to support decimal floating-point arithmetic.
17168 There are two encodings in use, depending on the architecture: BID (Binary
17169 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17170 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17173 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17174 to manipulate decimal floating point numbers, it is not possible to convert
17175 (using a cast, for example) integers wider than 32-bit to decimal float.
17177 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17178 point computations, error checking in decimal float operations ignores
17179 underflow, overflow and divide by zero exceptions.
17181 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17182 to inspect @code{_Decimal128} values stored in floating point registers.
17183 See @ref{PowerPC,,PowerPC} for more details.
17189 @value{GDBN} can be used to debug programs written in D and compiled with
17190 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17191 specific feature --- dynamic arrays.
17196 @cindex Go (programming language)
17197 @value{GDBN} can be used to debug programs written in Go and compiled with
17198 @file{gccgo} or @file{6g} compilers.
17200 Here is a summary of the Go-specific features and restrictions:
17203 @cindex current Go package
17204 @item The current Go package
17205 The name of the current package does not need to be specified when
17206 specifying global variables and functions.
17208 For example, given the program:
17212 var myglob = "Shall we?"
17218 When stopped inside @code{main} either of these work:
17222 (gdb) p main.myglob
17225 @cindex builtin Go types
17226 @item Builtin Go types
17227 The @code{string} type is recognized by @value{GDBN} and is printed
17230 @cindex builtin Go functions
17231 @item Builtin Go functions
17232 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17233 function and handles it internally.
17235 @cindex restrictions on Go expressions
17236 @item Restrictions on Go expressions
17237 All Go operators are supported except @code{&^}.
17238 The Go @code{_} ``blank identifier'' is not supported.
17239 Automatic dereferencing of pointers is not supported.
17243 @subsection Objective-C
17245 @cindex Objective-C
17246 This section provides information about some commands and command
17247 options that are useful for debugging Objective-C code. See also
17248 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17249 few more commands specific to Objective-C support.
17252 * Method Names in Commands::
17253 * The Print Command with Objective-C::
17256 @node Method Names in Commands
17257 @subsubsection Method Names in Commands
17259 The following commands have been extended to accept Objective-C method
17260 names as line specifications:
17262 @kindex clear@r{, and Objective-C}
17263 @kindex break@r{, and Objective-C}
17264 @kindex info line@r{, and Objective-C}
17265 @kindex jump@r{, and Objective-C}
17266 @kindex list@r{, and Objective-C}
17270 @item @code{info line}
17275 A fully qualified Objective-C method name is specified as
17278 -[@var{Class} @var{methodName}]
17281 where the minus sign is used to indicate an instance method and a
17282 plus sign (not shown) is used to indicate a class method. The class
17283 name @var{Class} and method name @var{methodName} are enclosed in
17284 brackets, similar to the way messages are specified in Objective-C
17285 source code. For example, to set a breakpoint at the @code{create}
17286 instance method of class @code{Fruit} in the program currently being
17290 break -[Fruit create]
17293 To list ten program lines around the @code{initialize} class method,
17297 list +[NSText initialize]
17300 In the current version of @value{GDBN}, the plus or minus sign is
17301 required. In future versions of @value{GDBN}, the plus or minus
17302 sign will be optional, but you can use it to narrow the search. It
17303 is also possible to specify just a method name:
17309 You must specify the complete method name, including any colons. If
17310 your program's source files contain more than one @code{create} method,
17311 you'll be presented with a numbered list of classes that implement that
17312 method. Indicate your choice by number, or type @samp{0} to exit if
17315 As another example, to clear a breakpoint established at the
17316 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17319 clear -[NSWindow makeKeyAndOrderFront:]
17322 @node The Print Command with Objective-C
17323 @subsubsection The Print Command With Objective-C
17324 @cindex Objective-C, print objects
17325 @kindex print-object
17326 @kindex po @r{(@code{print-object})}
17328 The print command has also been extended to accept methods. For example:
17331 print -[@var{object} hash]
17334 @cindex print an Objective-C object description
17335 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17337 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17338 and print the result. Also, an additional command has been added,
17339 @code{print-object} or @code{po} for short, which is meant to print
17340 the description of an object. However, this command may only work
17341 with certain Objective-C libraries that have a particular hook
17342 function, @code{_NSPrintForDebugger}, defined.
17345 @subsection OpenCL C
17348 This section provides information about @value{GDBN}s OpenCL C support.
17351 * OpenCL C Datatypes::
17352 * OpenCL C Expressions::
17353 * OpenCL C Operators::
17356 @node OpenCL C Datatypes
17357 @subsubsection OpenCL C Datatypes
17359 @cindex OpenCL C Datatypes
17360 @value{GDBN} supports the builtin scalar and vector datatypes specified
17361 by OpenCL 1.1. In addition the half- and double-precision floating point
17362 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17363 extensions are also known to @value{GDBN}.
17365 @node OpenCL C Expressions
17366 @subsubsection OpenCL C Expressions
17368 @cindex OpenCL C Expressions
17369 @value{GDBN} supports accesses to vector components including the access as
17370 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17371 supported by @value{GDBN} can be used as well.
17373 @node OpenCL C Operators
17374 @subsubsection OpenCL C Operators
17376 @cindex OpenCL C Operators
17377 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17381 @subsection Fortran
17382 @cindex Fortran-specific support in @value{GDBN}
17384 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17385 all Fortran language features are available yet.
17387 @cindex trailing underscore, in Fortran symbols
17388 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17389 among them) append an underscore to the names of variables and
17390 functions. When you debug programs compiled by those compilers, you
17391 will need to refer to variables and functions with a trailing
17394 @cindex Fortran Defaults
17395 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17396 default uses case-insensitive matching for Fortran symbols. You can
17397 change that with the @samp{set case-insensitive} command, see
17398 @ref{Symbols}, for the details.
17401 * Fortran Types:: Fortran builtin types
17402 * Fortran Operators:: Fortran operators and expressions
17403 * Fortran Intrinsics:: Fortran intrinsic functions
17404 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17407 @node Fortran Types
17408 @subsubsection Fortran Types
17410 @cindex Fortran Types
17412 In Fortran the primitive data-types have an associated @code{KIND} type
17413 parameter, written as @samp{@var{type}*@var{kindparam}},
17414 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17415 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17416 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17417 The kind of a type can be retrieved by using the intrinsic function
17418 @code{KIND}, see @ref{Fortran Intrinsics}.
17420 Generally, the actual implementation of the @code{KIND} type parameter is
17421 compiler specific. In @value{GDBN} the kind parameter is implemented in
17422 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17423 kind parameter for a given @var{type} specifies its size in memory --- a
17424 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17425 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17426 type for which the kind of the type does not specify its entire size, but
17427 the size of each of the two @code{Real}'s it is composed of. A
17428 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17431 For every type there is also a default kind associated with it, e.g.@
17432 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17433 table below for default types). The default types are the same as in @sc{gnu}
17434 compilers but note, that the @sc{gnu} default types can actually be changed by
17435 compiler flags such as @option{-fdefault-integer-8} and
17436 @option{-fdefault-real-8}.
17438 Not every kind parameter is valid for every type and in @value{GDBN} the
17439 following type kinds are available.
17443 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17444 @code{Integer} = @code{Integer*4}.
17447 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17448 @code{Logical} = @code{Logical*4}.
17451 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17454 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17459 @node Fortran Operators
17460 @subsubsection Fortran Operators and Expressions
17462 @cindex Fortran operators and expressions
17464 Operators must be defined on values of specific types. For instance,
17465 @code{+} is defined on numbers, but not on characters or other non-
17466 arithmetic types. Operators are often defined on groups of types.
17470 The exponentiation operator. It raises the first operand to the power
17474 The range operator. Normally used in the form of array(low:high) to
17475 represent a section of array.
17478 The access component operator. Normally used to access elements in derived
17479 types. Also suitable for unions. As unions aren't part of regular Fortran,
17480 this can only happen when accessing a register that uses a gdbarch-defined
17483 The scope operator. Normally used to access variables in modules or
17484 to set breakpoints on subroutines nested in modules or in other
17485 subroutines (internal subroutines).
17488 @node Fortran Intrinsics
17489 @subsubsection Fortran Intrinsics
17491 @cindex Fortran Intrinsics
17493 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17494 an incomplete subset of those procedures and their overloads. Some of these
17495 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17499 Computes the absolute value of its argument @var{a}. Currently not supported
17500 for @code{Complex} arguments.
17502 @item ALLOCATE(@var{array})
17503 Returns whether @var{array} is allocated or not.
17505 @item ASSOCIATED(@var{pointer} [, @var{target}])
17506 Returns the association status of the pointer @var{pointer} or, if @var{target}
17507 is present, whether @var{pointer} is associated with the target @var{target}.
17509 @item CEILING(@var{a} [, @var{kind}])
17510 Computes the least integer greater than or equal to @var{a}. The optional
17511 parameter @var{kind} specifies the kind of the return type
17512 @code{Integer(@var{kind})}.
17514 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17515 Returns a complex number where @var{x} is converted to the real component. If
17516 @var{y} is present it is converted to the imaginary component. If @var{y} is
17517 not present then the imaginary component is set to @code{0.0} except if @var{x}
17518 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17519 the kind of the return type @code{Complex(@var{kind})}.
17521 @item FLOOR(@var{a} [, @var{kind}])
17522 Computes the greatest integer less than or equal to @var{a}. The optional
17523 parameter @var{kind} specifies the kind of the return type
17524 @code{Integer(@var{kind})}.
17526 @item KIND(@var{a})
17527 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17529 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17530 Returns the lower bounds of an @var{array}, or a single lower bound along the
17531 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17532 the kind of the return type @code{Integer(@var{kind})}.
17535 Returns the address of @var{x} as an @code{Integer}.
17537 @item MOD(@var{a}, @var{p})
17538 Computes the remainder of the division of @var{a} by @var{p}.
17540 @item MODULO(@var{a}, @var{p})
17541 Computes the @var{a} modulo @var{p}.
17543 @item RANK(@var{a})
17544 Returns the rank of a scalar or array (scalars have rank @code{0}).
17546 @item SHAPE(@var{a})
17547 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17549 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17550 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17551 total number of elements in @var{array} if @var{dim} is absent. The optional
17552 parameter @var{kind} specifies the kind of the return type
17553 @code{Integer(@var{kind})}.
17555 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17556 Returns the upper bounds of an @var{array}, or a single upper bound along the
17557 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17558 the kind of the return type @code{Integer(@var{kind})}.
17562 @node Special Fortran Commands
17563 @subsubsection Special Fortran Commands
17565 @cindex Special Fortran commands
17567 @value{GDBN} has some commands to support Fortran-specific features,
17568 such as displaying common blocks.
17571 @cindex @code{COMMON} blocks, Fortran
17572 @kindex info common
17573 @item info common @r{[}@var{common-name}@r{]}
17574 This command prints the values contained in the Fortran @code{COMMON}
17575 block whose name is @var{common-name}. With no argument, the names of
17576 all @code{COMMON} blocks visible at the current program location are
17578 @cindex arrays slices (Fortran)
17579 @kindex set fortran repack-array-slices
17580 @kindex show fortran repack-array-slices
17581 @item set fortran repack-array-slices [on|off]
17582 @item show fortran repack-array-slices
17583 When taking a slice from an array, a Fortran compiler can choose to
17584 either produce an array descriptor that describes the slice in place,
17585 or it may repack the slice, copying the elements of the slice into a
17586 new region of memory.
17588 When this setting is on, then @value{GDBN} will also repack array
17589 slices in some situations. When this setting is off, then
17590 @value{GDBN} will create array descriptors for slices that reference
17591 the original data in place.
17593 @value{GDBN} will never repack an array slice if the data for the
17594 slice is contiguous within the original array.
17596 @value{GDBN} will always repack string slices if the data for the
17597 slice is non-contiguous within the original string as @value{GDBN}
17598 does not support printing non-contiguous strings.
17600 The default for this setting is @code{off}.
17606 @cindex Pascal support in @value{GDBN}, limitations
17607 Debugging Pascal programs which use sets, subranges, file variables, or
17608 nested functions does not currently work. @value{GDBN} does not support
17609 entering expressions, printing values, or similar features using Pascal
17612 The Pascal-specific command @code{set print pascal_static-members}
17613 controls whether static members of Pascal objects are displayed.
17614 @xref{Print Settings, pascal_static-members}.
17619 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17620 Programming Language}. Type- and value-printing, and expression
17621 parsing, are reasonably complete. However, there are a few
17622 peculiarities and holes to be aware of.
17626 Linespecs (@pxref{Location Specifications}) are never relative to the
17627 current crate. Instead, they act as if there were a global namespace
17628 of crates, somewhat similar to the way @code{extern crate} behaves.
17630 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17631 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17632 to set a breakpoint in a function named @samp{f} in a crate named
17635 As a consequence of this approach, linespecs also cannot refer to
17636 items using @samp{self::} or @samp{super::}.
17639 Because @value{GDBN} implements Rust name-lookup semantics in
17640 expressions, it will sometimes prepend the current crate to a name.
17641 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17642 @samp{K}, then @code{print ::x::y} will try to find the symbol
17645 However, since it is useful to be able to refer to other crates when
17646 debugging, @value{GDBN} provides the @code{extern} extension to
17647 circumvent this. To use the extension, just put @code{extern} before
17648 a path expression to refer to the otherwise unavailable ``global''
17651 In the above example, if you wanted to refer to the symbol @samp{y} in
17652 the crate @samp{x}, you would use @code{print extern x::y}.
17655 The Rust expression evaluator does not support ``statement-like''
17656 expressions such as @code{if} or @code{match}, or lambda expressions.
17659 Tuple expressions are not implemented.
17662 The Rust expression evaluator does not currently implement the
17663 @code{Drop} trait. Objects that may be created by the evaluator will
17664 never be destroyed.
17667 @value{GDBN} does not implement type inference for generics. In order
17668 to call generic functions or otherwise refer to generic items, you
17669 will have to specify the type parameters manually.
17672 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17673 cases this does not cause any problems. However, in an expression
17674 context, completing a generic function name will give syntactically
17675 invalid results. This happens because Rust requires the @samp{::}
17676 operator between the function name and its generic arguments. For
17677 example, @value{GDBN} might provide a completion like
17678 @code{crate::f<u32>}, where the parser would require
17679 @code{crate::f::<u32>}.
17682 As of this writing, the Rust compiler (version 1.8) has a few holes in
17683 the debugging information it generates. These holes prevent certain
17684 features from being implemented by @value{GDBN}:
17688 Method calls cannot be made via traits.
17691 Operator overloading is not implemented.
17694 When debugging in a monomorphized function, you cannot use the generic
17698 The type @code{Self} is not available.
17701 @code{use} statements are not available, so some names may not be
17702 available in the crate.
17707 @subsection Modula-2
17709 @cindex Modula-2, @value{GDBN} support
17711 The extensions made to @value{GDBN} to support Modula-2 only support
17712 output from the @sc{gnu} Modula-2 compiler (which is currently being
17713 developed). Other Modula-2 compilers are not currently supported, and
17714 attempting to debug executables produced by them is most likely
17715 to give an error as @value{GDBN} reads in the executable's symbol
17718 @cindex expressions in Modula-2
17720 * M2 Operators:: Built-in operators
17721 * Built-In Func/Proc:: Built-in functions and procedures
17722 * M2 Constants:: Modula-2 constants
17723 * M2 Types:: Modula-2 types
17724 * M2 Defaults:: Default settings for Modula-2
17725 * Deviations:: Deviations from standard Modula-2
17726 * M2 Checks:: Modula-2 type and range checks
17727 * M2 Scope:: The scope operators @code{::} and @code{.}
17728 * GDB/M2:: @value{GDBN} and Modula-2
17732 @subsubsection Operators
17733 @cindex Modula-2 operators
17735 Operators must be defined on values of specific types. For instance,
17736 @code{+} is defined on numbers, but not on structures. Operators are
17737 often defined on groups of types. For the purposes of Modula-2, the
17738 following definitions hold:
17743 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17747 @emph{Character types} consist of @code{CHAR} and its subranges.
17750 @emph{Floating-point types} consist of @code{REAL}.
17753 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17757 @emph{Scalar types} consist of all of the above.
17760 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17763 @emph{Boolean types} consist of @code{BOOLEAN}.
17767 The following operators are supported, and appear in order of
17768 increasing precedence:
17772 Function argument or array index separator.
17775 Assignment. The value of @var{var} @code{:=} @var{value} is
17779 Less than, greater than on integral, floating-point, or enumerated
17783 Less than or equal to, greater than or equal to
17784 on integral, floating-point and enumerated types, or set inclusion on
17785 set types. Same precedence as @code{<}.
17787 @item =@r{, }<>@r{, }#
17788 Equality and two ways of expressing inequality, valid on scalar types.
17789 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17790 available for inequality, since @code{#} conflicts with the script
17794 Set membership. Defined on set types and the types of their members.
17795 Same precedence as @code{<}.
17798 Boolean disjunction. Defined on boolean types.
17801 Boolean conjunction. Defined on boolean types.
17804 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17807 Addition and subtraction on integral and floating-point types, or union
17808 and difference on set types.
17811 Multiplication on integral and floating-point types, or set intersection
17815 Division on floating-point types, or symmetric set difference on set
17816 types. Same precedence as @code{*}.
17819 Integer division and remainder. Defined on integral types. Same
17820 precedence as @code{*}.
17823 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17826 Pointer dereferencing. Defined on pointer types.
17829 Boolean negation. Defined on boolean types. Same precedence as
17833 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17834 precedence as @code{^}.
17837 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17840 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17844 @value{GDBN} and Modula-2 scope operators.
17848 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17849 treats the use of the operator @code{IN}, or the use of operators
17850 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17851 @code{<=}, and @code{>=} on sets as an error.
17855 @node Built-In Func/Proc
17856 @subsubsection Built-in Functions and Procedures
17857 @cindex Modula-2 built-ins
17859 Modula-2 also makes available several built-in procedures and functions.
17860 In describing these, the following metavariables are used:
17865 represents an @code{ARRAY} variable.
17868 represents a @code{CHAR} constant or variable.
17871 represents a variable or constant of integral type.
17874 represents an identifier that belongs to a set. Generally used in the
17875 same function with the metavariable @var{s}. The type of @var{s} should
17876 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17879 represents a variable or constant of integral or floating-point type.
17882 represents a variable or constant of floating-point type.
17888 represents a variable.
17891 represents a variable or constant of one of many types. See the
17892 explanation of the function for details.
17895 All Modula-2 built-in procedures also return a result, described below.
17899 Returns the absolute value of @var{n}.
17902 If @var{c} is a lower case letter, it returns its upper case
17903 equivalent, otherwise it returns its argument.
17906 Returns the character whose ordinal value is @var{i}.
17909 Decrements the value in the variable @var{v} by one. Returns the new value.
17911 @item DEC(@var{v},@var{i})
17912 Decrements the value in the variable @var{v} by @var{i}. Returns the
17915 @item EXCL(@var{m},@var{s})
17916 Removes the element @var{m} from the set @var{s}. Returns the new
17919 @item FLOAT(@var{i})
17920 Returns the floating point equivalent of the integer @var{i}.
17922 @item HIGH(@var{a})
17923 Returns the index of the last member of @var{a}.
17926 Increments the value in the variable @var{v} by one. Returns the new value.
17928 @item INC(@var{v},@var{i})
17929 Increments the value in the variable @var{v} by @var{i}. Returns the
17932 @item INCL(@var{m},@var{s})
17933 Adds the element @var{m} to the set @var{s} if it is not already
17934 there. Returns the new set.
17937 Returns the maximum value of the type @var{t}.
17940 Returns the minimum value of the type @var{t}.
17943 Returns boolean TRUE if @var{i} is an odd number.
17946 Returns the ordinal value of its argument. For example, the ordinal
17947 value of a character is its @sc{ascii} value (on machines supporting
17948 the @sc{ascii} character set). The argument @var{x} must be of an
17949 ordered type, which include integral, character and enumerated types.
17951 @item SIZE(@var{x})
17952 Returns the size of its argument. The argument @var{x} can be a
17953 variable or a type.
17955 @item TRUNC(@var{r})
17956 Returns the integral part of @var{r}.
17958 @item TSIZE(@var{x})
17959 Returns the size of its argument. The argument @var{x} can be a
17960 variable or a type.
17962 @item VAL(@var{t},@var{i})
17963 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17967 @emph{Warning:} Sets and their operations are not yet supported, so
17968 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17972 @cindex Modula-2 constants
17974 @subsubsection Constants
17976 @value{GDBN} allows you to express the constants of Modula-2 in the following
17982 Integer constants are simply a sequence of digits. When used in an
17983 expression, a constant is interpreted to be type-compatible with the
17984 rest of the expression. Hexadecimal integers are specified by a
17985 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17988 Floating point constants appear as a sequence of digits, followed by a
17989 decimal point and another sequence of digits. An optional exponent can
17990 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17991 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17992 digits of the floating point constant must be valid decimal (base 10)
17996 Character constants consist of a single character enclosed by a pair of
17997 like quotes, either single (@code{'}) or double (@code{"}). They may
17998 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17999 followed by a @samp{C}.
18002 String constants consist of a sequence of characters enclosed by a
18003 pair of like quotes, either single (@code{'}) or double (@code{"}).
18004 Escape sequences in the style of C are also allowed. @xref{C
18005 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
18009 Enumerated constants consist of an enumerated identifier.
18012 Boolean constants consist of the identifiers @code{TRUE} and
18016 Pointer constants consist of integral values only.
18019 Set constants are not yet supported.
18023 @subsubsection Modula-2 Types
18024 @cindex Modula-2 types
18026 Currently @value{GDBN} can print the following data types in Modula-2
18027 syntax: array types, record types, set types, pointer types, procedure
18028 types, enumerated types, subrange types and base types. You can also
18029 print the contents of variables declared using these type.
18030 This section gives a number of simple source code examples together with
18031 sample @value{GDBN} sessions.
18033 The first example contains the following section of code:
18042 and you can request @value{GDBN} to interrogate the type and value of
18043 @code{r} and @code{s}.
18046 (@value{GDBP}) print s
18048 (@value{GDBP}) ptype s
18050 (@value{GDBP}) print r
18052 (@value{GDBP}) ptype r
18057 Likewise if your source code declares @code{s} as:
18061 s: SET ['A'..'Z'] ;
18065 then you may query the type of @code{s} by:
18068 (@value{GDBP}) ptype s
18069 type = SET ['A'..'Z']
18073 Note that at present you cannot interactively manipulate set
18074 expressions using the debugger.
18076 The following example shows how you might declare an array in Modula-2
18077 and how you can interact with @value{GDBN} to print its type and contents:
18081 s: ARRAY [-10..10] OF CHAR ;
18085 (@value{GDBP}) ptype s
18086 ARRAY [-10..10] OF CHAR
18089 Note that the array handling is not yet complete and although the type
18090 is printed correctly, expression handling still assumes that all
18091 arrays have a lower bound of zero and not @code{-10} as in the example
18094 Here are some more type related Modula-2 examples:
18098 colour = (blue, red, yellow, green) ;
18099 t = [blue..yellow] ;
18107 The @value{GDBN} interaction shows how you can query the data type
18108 and value of a variable.
18111 (@value{GDBP}) print s
18113 (@value{GDBP}) ptype t
18114 type = [blue..yellow]
18118 In this example a Modula-2 array is declared and its contents
18119 displayed. Observe that the contents are written in the same way as
18120 their @code{C} counterparts.
18124 s: ARRAY [1..5] OF CARDINAL ;
18130 (@value{GDBP}) print s
18131 $1 = @{1, 0, 0, 0, 0@}
18132 (@value{GDBP}) ptype s
18133 type = ARRAY [1..5] OF CARDINAL
18136 The Modula-2 language interface to @value{GDBN} also understands
18137 pointer types as shown in this example:
18141 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18148 and you can request that @value{GDBN} describes the type of @code{s}.
18151 (@value{GDBP}) ptype s
18152 type = POINTER TO ARRAY [1..5] OF CARDINAL
18155 @value{GDBN} handles compound types as we can see in this example.
18156 Here we combine array types, record types, pointer types and subrange
18167 myarray = ARRAY myrange OF CARDINAL ;
18168 myrange = [-2..2] ;
18170 s: POINTER TO ARRAY myrange OF foo ;
18174 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18178 (@value{GDBP}) ptype s
18179 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18182 f3 : ARRAY [-2..2] OF CARDINAL;
18187 @subsubsection Modula-2 Defaults
18188 @cindex Modula-2 defaults
18190 If type and range checking are set automatically by @value{GDBN}, they
18191 both default to @code{on} whenever the working language changes to
18192 Modula-2. This happens regardless of whether you or @value{GDBN}
18193 selected the working language.
18195 If you allow @value{GDBN} to set the language automatically, then entering
18196 code compiled from a file whose name ends with @file{.mod} sets the
18197 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18198 Infer the Source Language}, for further details.
18201 @subsubsection Deviations from Standard Modula-2
18202 @cindex Modula-2, deviations from
18204 A few changes have been made to make Modula-2 programs easier to debug.
18205 This is done primarily via loosening its type strictness:
18209 Unlike in standard Modula-2, pointer constants can be formed by
18210 integers. This allows you to modify pointer variables during
18211 debugging. (In standard Modula-2, the actual address contained in a
18212 pointer variable is hidden from you; it can only be modified
18213 through direct assignment to another pointer variable or expression that
18214 returned a pointer.)
18217 C escape sequences can be used in strings and characters to represent
18218 non-printable characters. @value{GDBN} prints out strings with these
18219 escape sequences embedded. Single non-printable characters are
18220 printed using the @samp{CHR(@var{nnn})} format.
18223 The assignment operator (@code{:=}) returns the value of its right-hand
18227 All built-in procedures both modify @emph{and} return their argument.
18231 @subsubsection Modula-2 Type and Range Checks
18232 @cindex Modula-2 checks
18235 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18238 @c FIXME remove warning when type/range checks added
18240 @value{GDBN} considers two Modula-2 variables type equivalent if:
18244 They are of types that have been declared equivalent via a @code{TYPE
18245 @var{t1} = @var{t2}} statement
18248 They have been declared on the same line. (Note: This is true of the
18249 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18252 As long as type checking is enabled, any attempt to combine variables
18253 whose types are not equivalent is an error.
18255 Range checking is done on all mathematical operations, assignment, array
18256 index bounds, and all built-in functions and procedures.
18259 @subsubsection The Scope Operators @code{::} and @code{.}
18261 @cindex @code{.}, Modula-2 scope operator
18262 @cindex colon, doubled as scope operator
18264 @vindex colon-colon@r{, in Modula-2}
18265 @c Info cannot handle :: but TeX can.
18268 @vindex ::@r{, in Modula-2}
18271 There are a few subtle differences between the Modula-2 scope operator
18272 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18277 @var{module} . @var{id}
18278 @var{scope} :: @var{id}
18282 where @var{scope} is the name of a module or a procedure,
18283 @var{module} the name of a module, and @var{id} is any declared
18284 identifier within your program, except another module.
18286 Using the @code{::} operator makes @value{GDBN} search the scope
18287 specified by @var{scope} for the identifier @var{id}. If it is not
18288 found in the specified scope, then @value{GDBN} searches all scopes
18289 enclosing the one specified by @var{scope}.
18291 Using the @code{.} operator makes @value{GDBN} search the current scope for
18292 the identifier specified by @var{id} that was imported from the
18293 definition module specified by @var{module}. With this operator, it is
18294 an error if the identifier @var{id} was not imported from definition
18295 module @var{module}, or if @var{id} is not an identifier in
18299 @subsubsection @value{GDBN} and Modula-2
18301 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18302 Five subcommands of @code{set print} and @code{show print} apply
18303 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18304 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18305 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18306 analogue in Modula-2.
18308 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18309 with any language, is not useful with Modula-2. Its
18310 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18311 created in Modula-2 as they can in C or C@t{++}. However, because an
18312 address can be specified by an integral constant, the construct
18313 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18315 @cindex @code{#} in Modula-2
18316 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18317 interpreted as the beginning of a comment. Use @code{<>} instead.
18323 The extensions made to @value{GDBN} for Ada only support
18324 output from the @sc{gnu} Ada (GNAT) compiler.
18325 Other Ada compilers are not currently supported, and
18326 attempting to debug executables produced by them is most likely
18330 @cindex expressions in Ada
18332 * Ada Mode Intro:: General remarks on the Ada syntax
18333 and semantics supported by Ada mode
18335 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18336 * Additions to Ada:: Extensions of the Ada expression syntax.
18337 * Overloading support for Ada:: Support for expressions involving overloaded
18339 * Stopping Before Main Program:: Debugging the program during elaboration.
18340 * Ada Exceptions:: Ada Exceptions
18341 * Ada Tasks:: Listing and setting breakpoints in tasks.
18342 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18343 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18345 * Ada Source Character Set:: Character set of Ada source files.
18346 * Ada Glitches:: Known peculiarities of Ada mode.
18349 @node Ada Mode Intro
18350 @subsubsection Introduction
18351 @cindex Ada mode, general
18353 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18354 syntax, with some extensions.
18355 The philosophy behind the design of this subset is
18359 That @value{GDBN} should provide basic literals and access to operations for
18360 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18361 leaving more sophisticated computations to subprograms written into the
18362 program (which therefore may be called from @value{GDBN}).
18365 That type safety and strict adherence to Ada language restrictions
18366 are not particularly important to the @value{GDBN} user.
18369 That brevity is important to the @value{GDBN} user.
18372 Thus, for brevity, the debugger acts as if all names declared in
18373 user-written packages are directly visible, even if they are not visible
18374 according to Ada rules, thus making it unnecessary to fully qualify most
18375 names with their packages, regardless of context. Where this causes
18376 ambiguity, @value{GDBN} asks the user's intent.
18378 The debugger will start in Ada mode if it detects an Ada main program.
18379 As for other languages, it will enter Ada mode when stopped in a program that
18380 was translated from an Ada source file.
18382 While in Ada mode, you may use `@t{--}' for comments. This is useful
18383 mostly for documenting command files. The standard @value{GDBN} comment
18384 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18385 middle (to allow based literals).
18387 @node Omissions from Ada
18388 @subsubsection Omissions from Ada
18389 @cindex Ada, omissions from
18391 Here are the notable omissions from the subset:
18395 Only a subset of the attributes are supported:
18399 @t{'First}, @t{'Last}, and @t{'Length}
18400 on array objects (not on types and subtypes).
18403 @t{'Min} and @t{'Max}.
18406 @t{'Pos} and @t{'Val}.
18412 @t{'Range} on array objects (not subtypes), but only as the right
18413 operand of the membership (@code{in}) operator.
18416 @t{'Access}, @t{'Unchecked_Access}, and
18417 @t{'Unrestricted_Access} (a GNAT extension).
18424 The names in @code{Characters.Latin_1} are not available.
18427 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18428 equality of representations. They will generally work correctly
18429 for strings and arrays whose elements have integer or enumeration types.
18430 They may not work correctly for arrays whose element
18431 types have user-defined equality, for arrays of real values
18432 (in particular, IEEE-conformant floating point, because of negative
18433 zeroes and NaNs), and for arrays whose elements contain unused bits with
18434 indeterminate values.
18437 The other component-by-component array operations (@code{and}, @code{or},
18438 @code{xor}, @code{not}, and relational tests other than equality)
18439 are not implemented.
18442 @cindex array aggregates (Ada)
18443 @cindex record aggregates (Ada)
18444 @cindex aggregates (Ada)
18445 There is limited support for array and record aggregates. They are
18446 permitted only on the right sides of assignments, as in these examples:
18449 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18450 (@value{GDBP}) set An_Array := (1, others => 0)
18451 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18452 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18453 (@value{GDBP}) set A_Record := (1, "Peter", True);
18454 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18458 discriminant's value by assigning an aggregate has an
18459 undefined effect if that discriminant is used within the record.
18460 However, you can first modify discriminants by directly assigning to
18461 them (which normally would not be allowed in Ada), and then performing an
18462 aggregate assignment. For example, given a variable @code{A_Rec}
18463 declared to have a type such as:
18466 type Rec (Len : Small_Integer := 0) is record
18468 Vals : IntArray (1 .. Len);
18472 you can assign a value with a different size of @code{Vals} with two
18476 (@value{GDBP}) set A_Rec.Len := 4
18477 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18480 As this example also illustrates, @value{GDBN} is very loose about the usual
18481 rules concerning aggregates. You may leave out some of the
18482 components of an array or record aggregate (such as the @code{Len}
18483 component in the assignment to @code{A_Rec} above); they will retain their
18484 original values upon assignment. You may freely use dynamic values as
18485 indices in component associations. You may even use overlapping or
18486 redundant component associations, although which component values are
18487 assigned in such cases is not defined.
18490 Calls to dispatching subprograms are not implemented.
18493 The overloading algorithm is much more limited (i.e., less selective)
18494 than that of real Ada. It makes only limited use of the context in
18495 which a subexpression appears to resolve its meaning, and it is much
18496 looser in its rules for allowing type matches. As a result, some
18497 function calls will be ambiguous, and the user will be asked to choose
18498 the proper resolution.
18501 The @code{new} operator is not implemented.
18504 Entry calls are not implemented.
18507 Aside from printing, arithmetic operations on the native VAX floating-point
18508 formats are not supported.
18511 It is not possible to slice a packed array.
18514 The names @code{True} and @code{False}, when not part of a qualified name,
18515 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18517 Should your program
18518 redefine these names in a package or procedure (at best a dubious practice),
18519 you will have to use fully qualified names to access their new definitions.
18522 Based real literals are not implemented.
18525 @node Additions to Ada
18526 @subsubsection Additions to Ada
18527 @cindex Ada, deviations from
18529 As it does for other languages, @value{GDBN} makes certain generic
18530 extensions to Ada (@pxref{Expressions}):
18534 If the expression @var{E} is a variable residing in memory (typically
18535 a local variable or array element) and @var{N} is a positive integer,
18536 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18537 @var{N}-1 adjacent variables following it in memory as an array. In
18538 Ada, this operator is generally not necessary, since its prime use is
18539 in displaying parts of an array, and slicing will usually do this in
18540 Ada. However, there are occasional uses when debugging programs in
18541 which certain debugging information has been optimized away.
18544 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18545 appears in function or file @var{B}.'' When @var{B} is a file name,
18546 you must typically surround it in single quotes.
18549 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18550 @var{type} that appears at address @var{addr}.''
18553 A name starting with @samp{$} is a convenience variable
18554 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18557 In addition, @value{GDBN} provides a few other shortcuts and outright
18558 additions specific to Ada:
18562 The assignment statement is allowed as an expression, returning
18563 its right-hand operand as its value. Thus, you may enter
18566 (@value{GDBP}) set x := y + 3
18567 (@value{GDBP}) print A(tmp := y + 1)
18571 The semicolon is allowed as an ``operator,'' returning as its value
18572 the value of its right-hand operand.
18573 This allows, for example,
18574 complex conditional breaks:
18577 (@value{GDBP}) break f
18578 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18582 An extension to based literals can be used to specify the exact byte
18583 contents of a floating-point literal. After the base, you can use
18584 from zero to two @samp{l} characters, followed by an @samp{f}. The
18585 number of @samp{l} characters controls the width of the resulting real
18586 constant: zero means @code{Float} is used, one means
18587 @code{Long_Float}, and two means @code{Long_Long_Float}.
18590 (@value{GDBP}) print 16f#41b80000#
18595 Rather than use catenation and symbolic character names to introduce special
18596 characters into strings, one may instead use a special bracket notation,
18597 which is also used to print strings. A sequence of characters of the form
18598 @samp{["@var{XX}"]} within a string or character literal denotes the
18599 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18600 sequence of characters @samp{["""]} also denotes a single quotation mark
18601 in strings. For example,
18603 "One line.["0a"]Next line.["0a"]"
18606 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18610 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18611 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18615 (@value{GDBP}) print 'max(x, y)
18619 When printing arrays, @value{GDBN} uses positional notation when the
18620 array has a lower bound of 1, and uses a modified named notation otherwise.
18621 For example, a one-dimensional array of three integers with a lower bound
18622 of 3 might print as
18629 That is, in contrast to valid Ada, only the first component has a @code{=>}
18633 You may abbreviate attributes in expressions with any unique,
18634 multi-character subsequence of
18635 their names (an exact match gets preference).
18636 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18637 in place of @t{a'length}.
18640 @cindex quoting Ada internal identifiers
18641 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18642 to lower case. The GNAT compiler uses upper-case characters for
18643 some of its internal identifiers, which are normally of no interest to users.
18644 For the rare occasions when you actually have to look at them,
18645 enclose them in angle brackets to avoid the lower-case mapping.
18648 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18652 Printing an object of class-wide type or dereferencing an
18653 access-to-class-wide value will display all the components of the object's
18654 specific type (as indicated by its run-time tag). Likewise, component
18655 selection on such a value will operate on the specific type of the
18660 @node Overloading support for Ada
18661 @subsubsection Overloading support for Ada
18662 @cindex overloading, Ada
18664 The debugger supports limited overloading. Given a subprogram call in which
18665 the function symbol has multiple definitions, it will use the number of
18666 actual parameters and some information about their types to attempt to narrow
18667 the set of definitions. It also makes very limited use of context, preferring
18668 procedures to functions in the context of the @code{call} command, and
18669 functions to procedures elsewhere.
18671 If, after narrowing, the set of matching definitions still contains more than
18672 one definition, @value{GDBN} will display a menu to query which one it should
18676 (@value{GDBP}) print f(1)
18677 Multiple matches for f
18679 [1] foo.f (integer) return boolean at foo.adb:23
18680 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18684 In this case, just select one menu entry either to cancel expression evaluation
18685 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18686 instance (type the corresponding number and press @key{RET}).
18688 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18693 @kindex set ada print-signatures
18694 @item set ada print-signatures
18695 Control whether parameter types and return types are displayed in overloads
18696 selection menus. It is @code{on} by default.
18697 @xref{Overloading support for Ada}.
18699 @kindex show ada print-signatures
18700 @item show ada print-signatures
18701 Show the current setting for displaying parameter types and return types in
18702 overloads selection menu.
18703 @xref{Overloading support for Ada}.
18707 @node Stopping Before Main Program
18708 @subsubsection Stopping at the Very Beginning
18710 @cindex breakpointing Ada elaboration code
18711 It is sometimes necessary to debug the program during elaboration, and
18712 before reaching the main procedure.
18713 As defined in the Ada Reference
18714 Manual, the elaboration code is invoked from a procedure called
18715 @code{adainit}. To run your program up to the beginning of
18716 elaboration, simply use the following two commands:
18717 @code{tbreak adainit} and @code{run}.
18719 @node Ada Exceptions
18720 @subsubsection Ada Exceptions
18722 A command is provided to list all Ada exceptions:
18725 @kindex info exceptions
18726 @item info exceptions
18727 @itemx info exceptions @var{regexp}
18728 The @code{info exceptions} command allows you to list all Ada exceptions
18729 defined within the program being debugged, as well as their addresses.
18730 With a regular expression, @var{regexp}, as argument, only those exceptions
18731 whose names match @var{regexp} are listed.
18734 Below is a small example, showing how the command can be used, first
18735 without argument, and next with a regular expression passed as an
18739 (@value{GDBP}) info exceptions
18740 All defined Ada exceptions:
18741 constraint_error: 0x613da0
18742 program_error: 0x613d20
18743 storage_error: 0x613ce0
18744 tasking_error: 0x613ca0
18745 const.aint_global_e: 0x613b00
18746 (@value{GDBP}) info exceptions const.aint
18747 All Ada exceptions matching regular expression "const.aint":
18748 constraint_error: 0x613da0
18749 const.aint_global_e: 0x613b00
18752 It is also possible to ask @value{GDBN} to stop your program's execution
18753 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18756 @subsubsection Extensions for Ada Tasks
18757 @cindex Ada, tasking
18759 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18760 @value{GDBN} provides the following task-related commands:
18765 This command shows a list of current Ada tasks, as in the following example:
18772 (@value{GDBP}) info tasks
18773 ID TID P-ID Pri State Name
18774 1 8088000 0 15 Child Activation Wait main_task
18775 2 80a4000 1 15 Accept Statement b
18776 3 809a800 1 15 Child Activation Wait a
18777 * 4 80ae800 3 15 Runnable c
18782 In this listing, the asterisk before the last task indicates it to be the
18783 task currently being inspected.
18787 Represents @value{GDBN}'s internal task number.
18793 The parent's task ID (@value{GDBN}'s internal task number).
18796 The base priority of the task.
18799 Current state of the task.
18803 The task has been created but has not been activated. It cannot be
18807 The task is not blocked for any reason known to Ada. (It may be waiting
18808 for a mutex, though.) It is conceptually "executing" in normal mode.
18811 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18812 that were waiting on terminate alternatives have been awakened and have
18813 terminated themselves.
18815 @item Child Activation Wait
18816 The task is waiting for created tasks to complete activation.
18818 @item Accept Statement
18819 The task is waiting on an accept or selective wait statement.
18821 @item Waiting on entry call
18822 The task is waiting on an entry call.
18824 @item Async Select Wait
18825 The task is waiting to start the abortable part of an asynchronous
18829 The task is waiting on a select statement with only a delay
18832 @item Child Termination Wait
18833 The task is sleeping having completed a master within itself, and is
18834 waiting for the tasks dependent on that master to become terminated or
18835 waiting on a terminate Phase.
18837 @item Wait Child in Term Alt
18838 The task is sleeping waiting for tasks on terminate alternatives to
18839 finish terminating.
18841 @item Accepting RV with @var{taskno}
18842 The task is accepting a rendez-vous with the task @var{taskno}.
18846 Name of the task in the program.
18850 @kindex info task @var{taskno}
18851 @item info task @var{taskno}
18852 This command shows detailed informations on the specified task, as in
18853 the following example:
18858 (@value{GDBP}) info tasks
18859 ID TID P-ID Pri State Name
18860 1 8077880 0 15 Child Activation Wait main_task
18861 * 2 807c468 1 15 Runnable task_1
18862 (@value{GDBP}) info task 2
18863 Ada Task: 0x807c468
18867 Parent: 1 ("main_task")
18873 @kindex task@r{ (Ada)}
18874 @cindex current Ada task ID
18875 This command prints the ID and name of the current task.
18881 (@value{GDBP}) info tasks
18882 ID TID P-ID Pri State Name
18883 1 8077870 0 15 Child Activation Wait main_task
18884 * 2 807c458 1 15 Runnable some_task
18885 (@value{GDBP}) task
18886 [Current task is 2 "some_task"]
18889 @item task @var{taskno}
18890 @cindex Ada task switching
18891 This command is like the @code{thread @var{thread-id}}
18892 command (@pxref{Threads}). It switches the context of debugging
18893 from the current task to the given task.
18899 (@value{GDBP}) info tasks
18900 ID TID P-ID Pri State Name
18901 1 8077870 0 15 Child Activation Wait main_task
18902 * 2 807c458 1 15 Runnable some_task
18903 (@value{GDBP}) task 1
18904 [Switching to task 1 "main_task"]
18905 #0 0x8067726 in pthread_cond_wait ()
18907 #0 0x8067726 in pthread_cond_wait ()
18908 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18909 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18910 #3 0x806153e in system.tasking.stages.activate_tasks ()
18911 #4 0x804aacc in un () at un.adb:5
18914 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18915 The @code{task apply} command is the Ada tasking analogue of
18916 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18917 named @var{command} to one or more tasks. Specify the tasks that you
18918 want affected using a list of task IDs, or specify @code{all} to apply
18921 The @var{flag} arguments control what output to produce and how to
18922 handle errors raised when applying @var{command} to a task.
18923 @var{flag} must start with a @code{-} directly followed by one letter
18924 in @code{qcs}. If several flags are provided, they must be given
18925 individually, such as @code{-c -q}.
18927 By default, @value{GDBN} displays some task information before the
18928 output produced by @var{command}, and an error raised during the
18929 execution of a @var{command} will abort @code{task apply}. The
18930 following flags can be used to fine-tune this behavior:
18934 The flag @code{-c}, which stands for @samp{continue}, causes any
18935 errors in @var{command} to be displayed, and the execution of
18936 @code{task apply} then continues.
18938 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18939 or empty output produced by a @var{command} to be silently ignored.
18940 That is, the execution continues, but the task information and errors
18943 The flag @code{-q} (@samp{quiet}) disables printing the task
18947 Flags @code{-c} and @code{-s} cannot be used together.
18949 @item break @var{locspec} task @var{taskno}
18950 @itemx break @var{locspec} task @var{taskno} if @dots{}
18951 @cindex breakpoints and tasks, in Ada
18952 @cindex task breakpoints, in Ada
18953 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18954 These commands are like the @code{break @dots{} thread @dots{}}
18955 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
18956 the various forms of @var{locspec}.
18958 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18959 to specify that you only want @value{GDBN} to stop the program when a
18960 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18961 numeric task identifiers assigned by @value{GDBN}, shown in the first
18962 column of the @samp{info tasks} display.
18964 If you do not specify @samp{task @var{taskno}} when you set a
18965 breakpoint, the breakpoint applies to @emph{all} tasks of your
18968 You can use the @code{task} qualifier on conditional breakpoints as
18969 well; in this case, place @samp{task @var{taskno}} before the
18970 breakpoint condition (before the @code{if}).
18978 (@value{GDBP}) info tasks
18979 ID TID P-ID Pri State Name
18980 1 140022020 0 15 Child Activation Wait main_task
18981 2 140045060 1 15 Accept/Select Wait t2
18982 3 140044840 1 15 Runnable t1
18983 * 4 140056040 1 15 Runnable t3
18984 (@value{GDBP}) b 15 task 2
18985 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18986 (@value{GDBP}) cont
18991 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18993 (@value{GDBP}) info tasks
18994 ID TID P-ID Pri State Name
18995 1 140022020 0 15 Child Activation Wait main_task
18996 * 2 140045060 1 15 Runnable t2
18997 3 140044840 1 15 Runnable t1
18998 4 140056040 1 15 Delay Sleep t3
19002 @node Ada Tasks and Core Files
19003 @subsubsection Tasking Support when Debugging Core Files
19004 @cindex Ada tasking and core file debugging
19006 When inspecting a core file, as opposed to debugging a live program,
19007 tasking support may be limited or even unavailable, depending on
19008 the platform being used.
19009 For instance, on x86-linux, the list of tasks is available, but task
19010 switching is not supported.
19012 On certain platforms, the debugger needs to perform some
19013 memory writes in order to provide Ada tasking support. When inspecting
19014 a core file, this means that the core file must be opened with read-write
19015 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19016 Under these circumstances, you should make a backup copy of the core
19017 file before inspecting it with @value{GDBN}.
19019 @node Ravenscar Profile
19020 @subsubsection Tasking Support when using the Ravenscar Profile
19021 @cindex Ravenscar Profile
19023 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19024 specifically designed for systems with safety-critical real-time
19028 @kindex set ravenscar task-switching on
19029 @cindex task switching with program using Ravenscar Profile
19030 @item set ravenscar task-switching on
19031 Allows task switching when debugging a program that uses the Ravenscar
19032 Profile. This is the default.
19034 @kindex set ravenscar task-switching off
19035 @item set ravenscar task-switching off
19036 Turn off task switching when debugging a program that uses the Ravenscar
19037 Profile. This is mostly intended to disable the code that adds support
19038 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19039 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19040 To be effective, this command should be run before the program is started.
19042 @kindex show ravenscar task-switching
19043 @item show ravenscar task-switching
19044 Show whether it is possible to switch from task to task in a program
19045 using the Ravenscar Profile.
19049 @cindex Ravenscar thread
19050 When Ravenscar task-switching is enabled, Ravenscar tasks are
19051 announced by @value{GDBN} as if they were threads:
19055 [New Ravenscar Thread 0x2b8f0]
19058 Both Ravenscar tasks and the underlying CPU threads will show up in
19059 the output of @code{info threads}:
19064 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19065 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19066 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19067 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19068 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19069 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19072 One known limitation of the Ravenscar support in @value{GDBN} is that
19073 it isn't currently possible to single-step through the runtime
19074 initialization sequence. If you need to debug this code, you should
19075 use @code{set ravenscar task-switching off}.
19077 @node Ada Source Character Set
19078 @subsubsection Ada Source Character Set
19079 @cindex Ada, source character set
19081 The GNAT compiler supports a number of character sets for source
19082 files. @xref{Character Set Control, , Character Set Control,
19083 gnat_ugn}. @value{GDBN} includes support for this as well.
19086 @item set ada source-charset @var{charset}
19087 @kindex set ada source-charset
19088 Set the source character set for Ada. The character set must be
19089 supported by GNAT. Because this setting affects the decoding of
19090 symbols coming from the debug information in your program, the setting
19091 should be set as early as possible. The default is @code{ISO-8859-1},
19092 because that is also GNAT's default.
19094 @item show ada source-charset
19095 @kindex show ada source-charset
19096 Show the current source character set for Ada.
19100 @subsubsection Known Peculiarities of Ada Mode
19101 @cindex Ada, problems
19103 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19104 we know of several problems with and limitations of Ada mode in
19106 some of which will be fixed with planned future releases of the debugger
19107 and the GNU Ada compiler.
19111 Static constants that the compiler chooses not to materialize as objects in
19112 storage are invisible to the debugger.
19115 Named parameter associations in function argument lists are ignored (the
19116 argument lists are treated as positional).
19119 Many useful library packages are currently invisible to the debugger.
19122 Fixed-point arithmetic, conversions, input, and output is carried out using
19123 floating-point arithmetic, and may give results that only approximate those on
19127 The GNAT compiler never generates the prefix @code{Standard} for any of
19128 the standard symbols defined by the Ada language. @value{GDBN} knows about
19129 this: it will strip the prefix from names when you use it, and will never
19130 look for a name you have so qualified among local symbols, nor match against
19131 symbols in other packages or subprograms. If you have
19132 defined entities anywhere in your program other than parameters and
19133 local variables whose simple names match names in @code{Standard},
19134 GNAT's lack of qualification here can cause confusion. When this happens,
19135 you can usually resolve the confusion
19136 by qualifying the problematic names with package
19137 @code{Standard} explicitly.
19140 Older versions of the compiler sometimes generate erroneous debugging
19141 information, resulting in the debugger incorrectly printing the value
19142 of affected entities. In some cases, the debugger is able to work
19143 around an issue automatically. In other cases, the debugger is able
19144 to work around the issue, but the work-around has to be specifically
19147 @kindex set ada trust-PAD-over-XVS
19148 @kindex show ada trust-PAD-over-XVS
19151 @item set ada trust-PAD-over-XVS on
19152 Configure GDB to strictly follow the GNAT encoding when computing the
19153 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19154 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19155 a complete description of the encoding used by the GNAT compiler).
19156 This is the default.
19158 @item set ada trust-PAD-over-XVS off
19159 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19160 sometimes prints the wrong value for certain entities, changing @code{ada
19161 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19162 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19163 @code{off}, but this incurs a slight performance penalty, so it is
19164 recommended to leave this setting to @code{on} unless necessary.
19168 @cindex GNAT descriptive types
19169 @cindex GNAT encoding
19170 Internally, the debugger also relies on the compiler following a number
19171 of conventions known as the @samp{GNAT Encoding}, all documented in
19172 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19173 how the debugging information should be generated for certain types.
19174 In particular, this convention makes use of @dfn{descriptive types},
19175 which are artificial types generated purely to help the debugger.
19177 These encodings were defined at a time when the debugging information
19178 format used was not powerful enough to describe some of the more complex
19179 types available in Ada. Since DWARF allows us to express nearly all
19180 Ada features, the long-term goal is to slowly replace these descriptive
19181 types by their pure DWARF equivalent. To facilitate that transition,
19182 a new maintenance option is available to force the debugger to ignore
19183 those descriptive types. It allows the user to quickly evaluate how
19184 well @value{GDBN} works without them.
19188 @kindex maint ada set ignore-descriptive-types
19189 @item maintenance ada set ignore-descriptive-types [on|off]
19190 Control whether the debugger should ignore descriptive types.
19191 The default is not to ignore descriptives types (@code{off}).
19193 @kindex maint ada show ignore-descriptive-types
19194 @item maintenance ada show ignore-descriptive-types
19195 Show if descriptive types are ignored by @value{GDBN}.
19199 @node Unsupported Languages
19200 @section Unsupported Languages
19202 @cindex unsupported languages
19203 @cindex minimal language
19204 In addition to the other fully-supported programming languages,
19205 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19206 It does not represent a real programming language, but provides a set
19207 of capabilities close to what the C or assembly languages provide.
19208 This should allow most simple operations to be performed while debugging
19209 an application that uses a language currently not supported by @value{GDBN}.
19211 If the language is set to @code{auto}, @value{GDBN} will automatically
19212 select this language if the current frame corresponds to an unsupported
19216 @chapter Examining the Symbol Table
19218 The commands described in this chapter allow you to inquire about the
19219 symbols (names of variables, functions and types) defined in your
19220 program. This information is inherent in the text of your program and
19221 does not change as your program executes. @value{GDBN} finds it in your
19222 program's symbol table, in the file indicated when you started @value{GDBN}
19223 (@pxref{File Options, ,Choosing Files}), or by one of the
19224 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19226 @cindex symbol names
19227 @cindex names of symbols
19228 @cindex quoting names
19229 @anchor{quoting names}
19230 Occasionally, you may need to refer to symbols that contain unusual
19231 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19232 most frequent case is in referring to static variables in other
19233 source files (@pxref{Variables,,Program Variables}). File names
19234 are recorded in object files as debugging symbols, but @value{GDBN} would
19235 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19236 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19237 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19244 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19247 @cindex case-insensitive symbol names
19248 @cindex case sensitivity in symbol names
19249 @kindex set case-sensitive
19250 @item set case-sensitive on
19251 @itemx set case-sensitive off
19252 @itemx set case-sensitive auto
19253 Normally, when @value{GDBN} looks up symbols, it matches their names
19254 with case sensitivity determined by the current source language.
19255 Occasionally, you may wish to control that. The command @code{set
19256 case-sensitive} lets you do that by specifying @code{on} for
19257 case-sensitive matches or @code{off} for case-insensitive ones. If
19258 you specify @code{auto}, case sensitivity is reset to the default
19259 suitable for the source language. The default is case-sensitive
19260 matches for all languages except for Fortran, for which the default is
19261 case-insensitive matches.
19263 @kindex show case-sensitive
19264 @item show case-sensitive
19265 This command shows the current setting of case sensitivity for symbols
19268 @kindex set print type methods
19269 @item set print type methods
19270 @itemx set print type methods on
19271 @itemx set print type methods off
19272 Normally, when @value{GDBN} prints a class, it displays any methods
19273 declared in that class. You can control this behavior either by
19274 passing the appropriate flag to @code{ptype}, or using @command{set
19275 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19276 display the methods; this is the default. Specifying @code{off} will
19277 cause @value{GDBN} to omit the methods.
19279 @kindex show print type methods
19280 @item show print type methods
19281 This command shows the current setting of method display when printing
19284 @kindex set print type nested-type-limit
19285 @item set print type nested-type-limit @var{limit}
19286 @itemx set print type nested-type-limit unlimited
19287 Set the limit of displayed nested types that the type printer will
19288 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19289 nested definitions. By default, the type printer will not show any nested
19290 types defined in classes.
19292 @kindex show print type nested-type-limit
19293 @item show print type nested-type-limit
19294 This command shows the current display limit of nested types when
19297 @kindex set print type typedefs
19298 @item set print type typedefs
19299 @itemx set print type typedefs on
19300 @itemx set print type typedefs off
19302 Normally, when @value{GDBN} prints a class, it displays any typedefs
19303 defined in that class. You can control this behavior either by
19304 passing the appropriate flag to @code{ptype}, or using @command{set
19305 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19306 display the typedef definitions; this is the default. Specifying
19307 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19308 Note that this controls whether the typedef definition itself is
19309 printed, not whether typedef names are substituted when printing other
19312 @kindex show print type typedefs
19313 @item show print type typedefs
19314 This command shows the current setting of typedef display when
19317 @kindex set print type hex
19318 @item set print type hex
19319 @itemx set print type hex on
19320 @itemx set print type hex off
19322 When @value{GDBN} prints sizes and offsets of struct members, it can use
19323 either the decimal or hexadecimal notation. You can select one or the
19324 other either by passing the appropriate flag to @code{ptype}, or by using
19325 the @command{set print type hex} command.
19327 @kindex show print type hex
19328 @item show print type hex
19329 This command shows whether the sizes and offsets of struct members are
19330 printed in decimal or hexadecimal notation.
19332 @kindex info address
19333 @cindex address of a symbol
19334 @item info address @var{symbol}
19335 Describe where the data for @var{symbol} is stored. For a register
19336 variable, this says which register it is kept in. For a non-register
19337 local variable, this prints the stack-frame offset at which the variable
19340 Note the contrast with @samp{print &@var{symbol}}, which does not work
19341 at all for a register variable, and for a stack local variable prints
19342 the exact address of the current instantiation of the variable.
19344 @kindex info symbol
19345 @cindex symbol from address
19346 @cindex closest symbol and offset for an address
19347 @item info symbol @var{addr}
19348 Print the name of a symbol which is stored at the address @var{addr}.
19349 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19350 nearest symbol and an offset from it:
19353 (@value{GDBP}) info symbol 0x54320
19354 _initialize_vx + 396 in section .text
19358 This is the opposite of the @code{info address} command. You can use
19359 it to find out the name of a variable or a function given its address.
19361 For dynamically linked executables, the name of executable or shared
19362 library containing the symbol is also printed:
19365 (@value{GDBP}) info symbol 0x400225
19366 _start + 5 in section .text of /tmp/a.out
19367 (@value{GDBP}) info symbol 0x2aaaac2811cf
19368 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19373 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19374 Demangle @var{name}.
19375 If @var{language} is provided it is the name of the language to demangle
19376 @var{name} in. Otherwise @var{name} is demangled in the current language.
19378 The @samp{--} option specifies the end of options,
19379 and is useful when @var{name} begins with a dash.
19381 The parameter @code{demangle-style} specifies how to interpret the kind
19382 of mangling used. @xref{Print Settings}.
19385 @item whatis[/@var{flags}] [@var{arg}]
19386 Print the data type of @var{arg}, which can be either an expression
19387 or a name of a data type. With no argument, print the data type of
19388 @code{$}, the last value in the value history.
19390 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19391 is not actually evaluated, and any side-effecting operations (such as
19392 assignments or function calls) inside it do not take place.
19394 If @var{arg} is a variable or an expression, @code{whatis} prints its
19395 literal type as it is used in the source code. If the type was
19396 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19397 the data type underlying the @code{typedef}. If the type of the
19398 variable or the expression is a compound data type, such as
19399 @code{struct} or @code{class}, @code{whatis} never prints their
19400 fields or methods. It just prints the @code{struct}/@code{class}
19401 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19402 such a compound data type, use @code{ptype}.
19404 If @var{arg} is a type name that was defined using @code{typedef},
19405 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19406 Unrolling means that @code{whatis} will show the underlying type used
19407 in the @code{typedef} declaration of @var{arg}. However, if that
19408 underlying type is also a @code{typedef}, @code{whatis} will not
19411 For C code, the type names may also have the form @samp{class
19412 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19413 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19415 @var{flags} can be used to modify how the type is displayed.
19416 Available flags are:
19420 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19421 parameters and typedefs defined in a class when printing the class'
19422 members. The @code{/r} flag disables this.
19425 Do not print methods defined in the class.
19428 Print methods defined in the class. This is the default, but the flag
19429 exists in case you change the default with @command{set print type methods}.
19432 Do not print typedefs defined in the class. Note that this controls
19433 whether the typedef definition itself is printed, not whether typedef
19434 names are substituted when printing other types.
19437 Print typedefs defined in the class. This is the default, but the flag
19438 exists in case you change the default with @command{set print type typedefs}.
19441 Print the offsets and sizes of fields in a struct, similar to what the
19442 @command{pahole} tool does. This option implies the @code{/tm} flags.
19445 Use hexadecimal notation when printing offsets and sizes of fields in a
19449 Use decimal notation when printing offsets and sizes of fields in a
19452 For example, given the following declarations:
19488 Issuing a @kbd{ptype /o struct tuv} command would print:
19491 (@value{GDBP}) ptype /o struct tuv
19492 /* offset | size */ type = struct tuv @{
19493 /* 0 | 4 */ int a1;
19494 /* XXX 4-byte hole */
19495 /* 8 | 8 */ char *a2;
19496 /* 16 | 4 */ int a3;
19498 /* total size (bytes): 24 */
19502 Notice the format of the first column of comments. There, you can
19503 find two parts separated by the @samp{|} character: the @emph{offset},
19504 which indicates where the field is located inside the struct, in
19505 bytes, and the @emph{size} of the field. Another interesting line is
19506 the marker of a @emph{hole} in the struct, indicating that it may be
19507 possible to pack the struct and make it use less space by reorganizing
19510 It is also possible to print offsets inside an union:
19513 (@value{GDBP}) ptype /o union qwe
19514 /* offset | size */ type = union qwe @{
19515 /* 24 */ struct tuv @{
19516 /* 0 | 4 */ int a1;
19517 /* XXX 4-byte hole */
19518 /* 8 | 8 */ char *a2;
19519 /* 16 | 4 */ int a3;
19521 /* total size (bytes): 24 */
19523 /* 40 */ struct xyz @{
19524 /* 0 | 4 */ int f1;
19525 /* 4 | 1 */ char f2;
19526 /* XXX 3-byte hole */
19527 /* 8 | 8 */ void *f3;
19528 /* 16 | 24 */ struct tuv @{
19529 /* 16 | 4 */ int a1;
19530 /* XXX 4-byte hole */
19531 /* 24 | 8 */ char *a2;
19532 /* 32 | 4 */ int a3;
19534 /* total size (bytes): 24 */
19537 /* total size (bytes): 40 */
19540 /* total size (bytes): 40 */
19544 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19545 same space (because we are dealing with an union), the offset is not
19546 printed for them. However, you can still examine the offset of each
19547 of these structures' fields.
19549 Another useful scenario is printing the offsets of a struct containing
19553 (@value{GDBP}) ptype /o struct tyu
19554 /* offset | size */ type = struct tyu @{
19555 /* 0:31 | 4 */ int a1 : 1;
19556 /* 0:28 | 4 */ int a2 : 3;
19557 /* 0: 5 | 4 */ int a3 : 23;
19558 /* 3: 3 | 1 */ signed char a4 : 2;
19559 /* XXX 3-bit hole */
19560 /* XXX 4-byte hole */
19561 /* 8 | 8 */ int64_t a5;
19562 /* 16: 0 | 4 */ int a6 : 5;
19563 /* 16: 5 | 8 */ int64_t a7 : 3;
19564 /* XXX 7-byte padding */
19566 /* total size (bytes): 24 */
19570 Note how the offset information is now extended to also include the
19571 first bit of the bitfield.
19575 @item ptype[/@var{flags}] [@var{arg}]
19576 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19577 detailed description of the type, instead of just the name of the type.
19578 @xref{Expressions, ,Expressions}.
19580 Contrary to @code{whatis}, @code{ptype} always unrolls any
19581 @code{typedef}s in its argument declaration, whether the argument is
19582 a variable, expression, or a data type. This means that @code{ptype}
19583 of a variable or an expression will not print literally its type as
19584 present in the source code---use @code{whatis} for that. @code{typedef}s at
19585 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19586 fields, methods and inner @code{class typedef}s of @code{struct}s,
19587 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19589 For example, for this variable declaration:
19592 typedef double real_t;
19593 struct complex @{ real_t real; double imag; @};
19594 typedef struct complex complex_t;
19596 real_t *real_pointer_var;
19600 the two commands give this output:
19604 (@value{GDBP}) whatis var
19606 (@value{GDBP}) ptype var
19607 type = struct complex @{
19611 (@value{GDBP}) whatis complex_t
19612 type = struct complex
19613 (@value{GDBP}) whatis struct complex
19614 type = struct complex
19615 (@value{GDBP}) ptype struct complex
19616 type = struct complex @{
19620 (@value{GDBP}) whatis real_pointer_var
19622 (@value{GDBP}) ptype real_pointer_var
19628 As with @code{whatis}, using @code{ptype} without an argument refers to
19629 the type of @code{$}, the last value in the value history.
19631 @cindex incomplete type
19632 Sometimes, programs use opaque data types or incomplete specifications
19633 of complex data structure. If the debug information included in the
19634 program does not allow @value{GDBN} to display a full declaration of
19635 the data type, it will say @samp{<incomplete type>}. For example,
19636 given these declarations:
19640 struct foo *fooptr;
19644 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19647 (@value{GDBP}) ptype foo
19648 $1 = <incomplete type>
19652 ``Incomplete type'' is C terminology for data types that are not
19653 completely specified.
19655 @cindex unknown type
19656 Othertimes, information about a variable's type is completely absent
19657 from the debug information included in the program. This most often
19658 happens when the program or library where the variable is defined
19659 includes no debug information at all. @value{GDBN} knows the variable
19660 exists from inspecting the linker/loader symbol table (e.g., the ELF
19661 dynamic symbol table), but such symbols do not contain type
19662 information. Inspecting the type of a (global) variable for which
19663 @value{GDBN} has no type information shows:
19666 (@value{GDBP}) ptype var
19667 type = <data variable, no debug info>
19670 @xref{Variables, no debug info variables}, for how to print the values
19674 @item info types [-q] [@var{regexp}]
19675 Print a brief description of all types whose names match the regular
19676 expression @var{regexp} (or all types in your program, if you supply
19677 no argument). Each complete typename is matched as though it were a
19678 complete line; thus, @samp{i type value} gives information on all
19679 types in your program whose names include the string @code{value}, but
19680 @samp{i type ^value$} gives information only on types whose complete
19681 name is @code{value}.
19683 In programs using different languages, @value{GDBN} chooses the syntax
19684 to print the type description according to the
19685 @samp{set language} value: using @samp{set language auto}
19686 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19687 language of the type, other values mean to use
19688 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19690 This command differs from @code{ptype} in two ways: first, like
19691 @code{whatis}, it does not print a detailed description; second, it
19692 lists all source files and line numbers where a type is defined.
19694 The output from @samp{into types} is proceeded with a header line
19695 describing what types are being listed. The optional flag @samp{-q},
19696 which stands for @samp{quiet}, disables printing this header
19699 @kindex info type-printers
19700 @item info type-printers
19701 Versions of @value{GDBN} that ship with Python scripting enabled may
19702 have ``type printers'' available. When using @command{ptype} or
19703 @command{whatis}, these printers are consulted when the name of a type
19704 is needed. @xref{Type Printing API}, for more information on writing
19707 @code{info type-printers} displays all the available type printers.
19709 @kindex enable type-printer
19710 @kindex disable type-printer
19711 @item enable type-printer @var{name}@dots{}
19712 @item disable type-printer @var{name}@dots{}
19713 These commands can be used to enable or disable type printers.
19716 @cindex local variables
19717 @item info scope @var{locspec}
19718 List all the variables local to the lexical scope of the code location
19719 that results from resolving @var{locspec}. @xref{Location
19720 Specifications}, for details about supported forms of @var{locspec}.
19724 (@value{GDBP}) @b{info scope command_line_handler}
19725 Scope for command_line_handler:
19726 Symbol rl is an argument at stack/frame offset 8, length 4.
19727 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19728 Symbol linelength is in static storage at address 0x150a1c, length 4.
19729 Symbol p is a local variable in register $esi, length 4.
19730 Symbol p1 is a local variable in register $ebx, length 4.
19731 Symbol nline is a local variable in register $edx, length 4.
19732 Symbol repeat is a local variable at frame offset -8, length 4.
19736 This command is especially useful for determining what data to collect
19737 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19740 @kindex info source
19742 Show information about the current source file---that is, the source file for
19743 the function containing the current point of execution:
19746 the name of the source file, and the directory containing it,
19748 the directory it was compiled in,
19750 its length, in lines,
19752 which programming language it is written in,
19754 if the debug information provides it, the program that compiled the file
19755 (which may include, e.g., the compiler version and command line arguments),
19757 whether the executable includes debugging information for that file, and
19758 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19760 whether the debugging information includes information about
19761 preprocessor macros.
19765 @kindex info sources
19766 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19769 With no options @samp{info sources} prints the names of all source
19770 files in your program for which there is debugging information. The
19771 source files are presented based on a list of object files
19772 (executables and libraries) currently loaded into @value{GDBN}. For
19773 each object file all of the associated source files are listed.
19775 Each source file will only be printed once for each object file, but a
19776 single source file can be repeated in the output if it is part of
19777 multiple object files.
19779 If the optional @var{regexp} is provided, then only source files that
19780 match the regular expression will be printed. The matching is
19781 case-sensitive, except on operating systems that have case-insensitive
19782 filesystem (e.g., MS-Windows). @samp{--} can be used before
19783 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19784 command option (e.g. if @var{regexp} starts with @samp{-}).
19786 By default, the @var{regexp} is used to match anywhere in the
19787 filename. If @code{-dirname}, only files having a dirname matching
19788 @var{regexp} are shown. If @code{-basename}, only files having a
19789 basename matching @var{regexp} are shown.
19791 It is possible that an object file may be printed in the list with no
19792 associated source files. This can happen when either no source files
19793 match @var{regexp}, or, the object file was compiled without debug
19794 information and so @value{GDBN} is unable to find any source file
19797 @kindex info functions
19798 @item info functions [-q] [-n]
19799 Print the names and data types of all defined functions.
19800 Similarly to @samp{info types}, this command groups its output by source
19801 files and annotates each function definition with its source line
19804 In programs using different languages, @value{GDBN} chooses the syntax
19805 to print the function name and type according to the
19806 @samp{set language} value: using @samp{set language auto}
19807 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19808 language of the function, other values mean to use
19809 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19811 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19812 results. A non-debugging symbol is a symbol that comes from the
19813 executable's symbol table, not from the debug information (for
19814 example, DWARF) associated with the executable.
19816 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19817 printing header information and messages explaining why no functions
19820 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19821 Like @samp{info functions}, but only print the names and data types
19822 of the functions selected with the provided regexp(s).
19824 If @var{regexp} is provided, print only the functions whose names
19825 match the regular expression @var{regexp}.
19826 Thus, @samp{info fun step} finds all functions whose
19827 names include @code{step}; @samp{info fun ^step} finds those whose names
19828 start with @code{step}. If a function name contains characters that
19829 conflict with the regular expression language (e.g.@:
19830 @samp{operator*()}), they may be quoted with a backslash.
19832 If @var{type_regexp} is provided, print only the functions whose
19833 types, as printed by the @code{whatis} command, match
19834 the regular expression @var{type_regexp}.
19835 If @var{type_regexp} contains space(s), it should be enclosed in
19836 quote characters. If needed, use backslash to escape the meaning
19837 of special characters or quotes.
19838 Thus, @samp{info fun -t '^int ('} finds the functions that return
19839 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19840 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19841 finds the functions whose names start with @code{step} and that return
19844 If both @var{regexp} and @var{type_regexp} are provided, a function
19845 is printed only if its name matches @var{regexp} and its type matches
19849 @kindex info variables
19850 @item info variables [-q] [-n]
19851 Print the names and data types of all variables that are defined
19852 outside of functions (i.e.@: excluding local variables).
19853 The printed variables are grouped by source files and annotated with
19854 their respective source line numbers.
19856 In programs using different languages, @value{GDBN} chooses the syntax
19857 to print the variable name and type according to the
19858 @samp{set language} value: using @samp{set language auto}
19859 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19860 language of the variable, other values mean to use
19861 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19863 The @samp{-n} flag excludes non-debugging symbols from the results.
19865 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19866 printing header information and messages explaining why no variables
19869 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19870 Like @kbd{info variables}, but only print the variables selected
19871 with the provided regexp(s).
19873 If @var{regexp} is provided, print only the variables whose names
19874 match the regular expression @var{regexp}.
19876 If @var{type_regexp} is provided, print only the variables whose
19877 types, as printed by the @code{whatis} command, match
19878 the regular expression @var{type_regexp}.
19879 If @var{type_regexp} contains space(s), it should be enclosed in
19880 quote characters. If needed, use backslash to escape the meaning
19881 of special characters or quotes.
19883 If both @var{regexp} and @var{type_regexp} are provided, an argument
19884 is printed only if its name matches @var{regexp} and its type matches
19887 @kindex info modules
19889 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19890 List all Fortran modules in the program, or all modules matching the
19891 optional regular expression @var{regexp}.
19893 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19894 printing header information and messages explaining why no modules
19897 @kindex info module
19898 @cindex Fortran modules, information about
19899 @cindex functions and variables by Fortran module
19900 @cindex module functions and variables
19901 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19902 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19903 List all functions or variables within all Fortran modules. The set
19904 of functions or variables listed can be limited by providing some or
19905 all of the optional regular expressions. If @var{module-regexp} is
19906 provided, then only Fortran modules matching @var{module-regexp} will
19907 be searched. Only functions or variables whose type matches the
19908 optional regular expression @var{type-regexp} will be listed. And
19909 only functions or variables whose name matches the optional regular
19910 expression @var{regexp} will be listed.
19912 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19913 printing header information and messages explaining why no functions
19914 or variables have been printed.
19916 @kindex info classes
19917 @cindex Objective-C, classes and selectors
19919 @itemx info classes @var{regexp}
19920 Display all Objective-C classes in your program, or
19921 (with the @var{regexp} argument) all those matching a particular regular
19924 @kindex info selectors
19925 @item info selectors
19926 @itemx info selectors @var{regexp}
19927 Display all Objective-C selectors in your program, or
19928 (with the @var{regexp} argument) all those matching a particular regular
19932 This was never implemented.
19933 @kindex info methods
19935 @itemx info methods @var{regexp}
19936 The @code{info methods} command permits the user to examine all defined
19937 methods within C@t{++} program, or (with the @var{regexp} argument) a
19938 specific set of methods found in the various C@t{++} classes. Many
19939 C@t{++} classes provide a large number of methods. Thus, the output
19940 from the @code{ptype} command can be overwhelming and hard to use. The
19941 @code{info-methods} command filters the methods, printing only those
19942 which match the regular-expression @var{regexp}.
19945 @cindex opaque data types
19946 @kindex set opaque-type-resolution
19947 @item set opaque-type-resolution on
19948 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19949 declared as a pointer to a @code{struct}, @code{class}, or
19950 @code{union}---for example, @code{struct MyType *}---that is used in one
19951 source file although the full declaration of @code{struct MyType} is in
19952 another source file. The default is on.
19954 A change in the setting of this subcommand will not take effect until
19955 the next time symbols for a file are loaded.
19957 @item set opaque-type-resolution off
19958 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19959 is printed as follows:
19961 @{<no data fields>@}
19964 @kindex show opaque-type-resolution
19965 @item show opaque-type-resolution
19966 Show whether opaque types are resolved or not.
19968 @kindex set print symbol-loading
19969 @cindex print messages when symbols are loaded
19970 @item set print symbol-loading
19971 @itemx set print symbol-loading full
19972 @itemx set print symbol-loading brief
19973 @itemx set print symbol-loading off
19974 The @code{set print symbol-loading} command allows you to control the
19975 printing of messages when @value{GDBN} loads symbol information.
19976 By default a message is printed for the executable and one for each
19977 shared library, and normally this is what you want. However, when
19978 debugging apps with large numbers of shared libraries these messages
19980 When set to @code{brief} a message is printed for each executable,
19981 and when @value{GDBN} loads a collection of shared libraries at once
19982 it will only print one message regardless of the number of shared
19983 libraries. When set to @code{off} no messages are printed.
19985 @kindex show print symbol-loading
19986 @item show print symbol-loading
19987 Show whether messages will be printed when a @value{GDBN} command
19988 entered from the keyboard causes symbol information to be loaded.
19990 @kindex maint print symbols
19991 @cindex symbol dump
19992 @kindex maint print psymbols
19993 @cindex partial symbol dump
19994 @kindex maint print msymbols
19995 @cindex minimal symbol dump
19996 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19997 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19998 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19999 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20000 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20001 Write a dump of debugging symbol data into the file @var{filename} or
20002 the terminal if @var{filename} is unspecified.
20003 If @code{-objfile @var{objfile}} is specified, only dump symbols for
20005 If @code{-pc @var{address}} is specified, only dump symbols for the file
20006 with code at that address. Note that @var{address} may be a symbol like
20008 If @code{-source @var{source}} is specified, only dump symbols for that
20011 These commands are used to debug the @value{GDBN} symbol-reading code.
20012 These commands do not modify internal @value{GDBN} state, therefore
20013 @samp{maint print symbols} will only print symbols for already expanded symbol
20015 You can use the command @code{info sources} to find out which files these are.
20016 If you use @samp{maint print psymbols} instead, the dump shows information
20017 about symbols that @value{GDBN} only knows partially---that is, symbols
20018 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20019 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20022 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20023 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20025 @kindex maint info symtabs
20026 @kindex maint info psymtabs
20027 @cindex listing @value{GDBN}'s internal symbol tables
20028 @cindex symbol tables, listing @value{GDBN}'s internal
20029 @cindex full symbol tables, listing @value{GDBN}'s internal
20030 @cindex partial symbol tables, listing @value{GDBN}'s internal
20031 @item maint info symtabs @r{[} @var{regexp} @r{]}
20032 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20034 List the @code{struct symtab} or @code{struct partial_symtab}
20035 structures whose names match @var{regexp}. If @var{regexp} is not
20036 given, list them all. The output includes expressions which you can
20037 copy into a @value{GDBN} debugging this one to examine a particular
20038 structure in more detail. For example:
20041 (@value{GDBP}) maint info psymtabs dwarf2read
20042 @{ objfile /home/gnu/build/gdb/gdb
20043 ((struct objfile *) 0x82e69d0)
20044 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20045 ((struct partial_symtab *) 0x8474b10)
20048 text addresses 0x814d3c8 -- 0x8158074
20049 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20050 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20051 dependencies (none)
20054 (@value{GDBP}) maint info symtabs
20058 We see that there is one partial symbol table whose filename contains
20059 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20060 and we see that @value{GDBN} has not read in any symtabs yet at all.
20061 If we set a breakpoint on a function, that will cause @value{GDBN} to
20062 read the symtab for the compilation unit containing that function:
20065 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20066 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20068 (@value{GDBP}) maint info symtabs
20069 @{ objfile /home/gnu/build/gdb/gdb
20070 ((struct objfile *) 0x82e69d0)
20071 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20072 ((struct symtab *) 0x86c1f38)
20075 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20076 linetable ((struct linetable *) 0x8370fa0)
20077 debugformat DWARF 2
20083 @kindex maint info line-table
20084 @cindex listing @value{GDBN}'s internal line tables
20085 @cindex line tables, listing @value{GDBN}'s internal
20086 @item maint info line-table @r{[} @var{regexp} @r{]}
20088 List the @code{struct linetable} from all @code{struct symtab}
20089 instances whose name matches @var{regexp}. If @var{regexp} is not
20090 given, list the @code{struct linetable} from all @code{struct symtab}.
20094 (@value{GDBP}) maint info line-table
20095 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20096 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20097 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20098 linetable: ((struct linetable *) 0x62100012b760):
20099 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
20100 0 3 0x0000000000401110 Y
20101 1 4 0x0000000000401114 Y Y
20102 2 9 0x0000000000401120 Y
20103 3 10 0x0000000000401124 Y Y
20104 4 10 0x0000000000401129
20105 5 15 0x0000000000401130 Y
20106 6 16 0x0000000000401134 Y Y
20107 7 16 0x0000000000401139
20108 8 21 0x0000000000401140 Y
20109 9 22 0x000000000040114f Y Y
20110 10 22 0x0000000000401154
20111 11 END 0x000000000040115a Y
20114 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20115 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20116 indicates that a given address is an adequate place to set a breakpoint at the
20117 first instruction following a function prologue.
20119 @kindex maint set symbol-cache-size
20120 @cindex symbol cache size
20121 @item maint set symbol-cache-size @var{size}
20122 Set the size of the symbol cache to @var{size}.
20123 The default size is intended to be good enough for debugging
20124 most applications. This option exists to allow for experimenting
20125 with different sizes.
20127 @kindex maint show symbol-cache-size
20128 @item maint show symbol-cache-size
20129 Show the size of the symbol cache.
20131 @kindex maint print symbol-cache
20132 @cindex symbol cache, printing its contents
20133 @item maint print symbol-cache
20134 Print the contents of the symbol cache.
20135 This is useful when debugging symbol cache issues.
20137 @kindex maint print symbol-cache-statistics
20138 @cindex symbol cache, printing usage statistics
20139 @item maint print symbol-cache-statistics
20140 Print symbol cache usage statistics.
20141 This helps determine how well the cache is being utilized.
20143 @kindex maint flush symbol-cache
20144 @kindex maint flush-symbol-cache
20145 @cindex symbol cache, flushing
20146 @item maint flush symbol-cache
20147 @itemx maint flush-symbol-cache
20148 Flush the contents of the symbol cache, all entries are removed. This
20149 command is useful when debugging the symbol cache. It is also useful
20150 when collecting performance data. The command @code{maint
20151 flush-symbol-cache} is deprecated in favor of @code{maint flush
20154 @kindex maint set ignore-prologue-end-flag
20155 @cindex prologue-end
20156 @item maint set ignore-prologue-end-flag [on|off]
20157 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20158 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20159 to place breakpoints past the end of a function prologue. When @samp{on},
20160 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20163 @kindex maint show ignore-prologue-end-flag
20164 @item maint show ignore-prologue-end-flag
20165 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20170 @chapter Altering Execution
20172 Once you think you have found an error in your program, you might want to
20173 find out for certain whether correcting the apparent error would lead to
20174 correct results in the rest of the run. You can find the answer by
20175 experiment, using the @value{GDBN} features for altering execution of the
20178 For example, you can store new values into variables or memory
20179 locations, give your program a signal, restart it at a different
20180 address, or even return prematurely from a function.
20183 * Assignment:: Assignment to variables
20184 * Jumping:: Continuing at a different address
20185 * Signaling:: Giving your program a signal
20186 * Returning:: Returning from a function
20187 * Calling:: Calling your program's functions
20188 * Patching:: Patching your program
20189 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20193 @section Assignment to Variables
20196 @cindex setting variables
20197 To alter the value of a variable, evaluate an assignment expression.
20198 @xref{Expressions, ,Expressions}. For example,
20205 stores the value 4 into the variable @code{x}, and then prints the
20206 value of the assignment expression (which is 4).
20207 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20208 information on operators in supported languages.
20210 @kindex set variable
20211 @cindex variables, setting
20212 If you are not interested in seeing the value of the assignment, use the
20213 @code{set} command instead of the @code{print} command. @code{set} is
20214 really the same as @code{print} except that the expression's value is
20215 not printed and is not put in the value history (@pxref{Value History,
20216 ,Value History}). The expression is evaluated only for its effects.
20218 If the beginning of the argument string of the @code{set} command
20219 appears identical to a @code{set} subcommand, use the @code{set
20220 variable} command instead of just @code{set}. This command is identical
20221 to @code{set} except for its lack of subcommands. For example, if your
20222 program has a variable @code{width}, you get an error if you try to set
20223 a new value with just @samp{set width=13}, because @value{GDBN} has the
20224 command @code{set width}:
20227 (@value{GDBP}) whatis width
20229 (@value{GDBP}) p width
20231 (@value{GDBP}) set width=47
20232 Invalid syntax in expression.
20236 The invalid expression, of course, is @samp{=47}. In
20237 order to actually set the program's variable @code{width}, use
20240 (@value{GDBP}) set var width=47
20243 Because the @code{set} command has many subcommands that can conflict
20244 with the names of program variables, it is a good idea to use the
20245 @code{set variable} command instead of just @code{set}. For example, if
20246 your program has a variable @code{g}, you run into problems if you try
20247 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20248 the command @code{set gnutarget}, abbreviated @code{set g}:
20252 (@value{GDBP}) whatis g
20256 (@value{GDBP}) set g=4
20260 The program being debugged has been started already.
20261 Start it from the beginning? (y or n) y
20262 Starting program: /home/smith/cc_progs/a.out
20263 "/home/smith/cc_progs/a.out": can't open to read symbols:
20264 Invalid bfd target.
20265 (@value{GDBP}) show g
20266 The current BFD target is "=4".
20271 The program variable @code{g} did not change, and you silently set the
20272 @code{gnutarget} to an invalid value. In order to set the variable
20276 (@value{GDBP}) set var g=4
20279 @value{GDBN} allows more implicit conversions in assignments than C; you can
20280 freely store an integer value into a pointer variable or vice versa,
20281 and you can convert any structure to any other structure that is the
20282 same length or shorter.
20283 @comment FIXME: how do structs align/pad in these conversions?
20284 @comment /doc@cygnus.com 18dec1990
20286 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20287 construct to generate a value of specified type at a specified address
20288 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20289 to memory location @code{0x83040} as an integer (which implies a certain size
20290 and representation in memory), and
20293 set @{int@}0x83040 = 4
20297 stores the value 4 into that memory location.
20300 @section Continuing at a Different Address
20302 Ordinarily, when you continue your program, you do so at the place where
20303 it stopped, with the @code{continue} command. You can instead continue at
20304 an address of your own choosing, with the following commands:
20308 @kindex j @r{(@code{jump})}
20309 @item jump @var{locspec}
20310 @itemx j @var{locspec}
20311 Resume execution at the address of the code location that results from
20312 resolving @var{locspec}.
20313 @xref{Location Specifications}, for a description of the different
20314 forms of @var{locspec}. If @var{locspec} resolves to more than one
20315 address, the command aborts before jumping.
20316 Execution stops again immediately if there is a breakpoint there. It
20317 is common practice to use the @code{tbreak} command in conjunction
20318 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20320 The @code{jump} command does not change the current stack frame, or
20321 the stack pointer, or the contents of any memory location or any
20322 register other than the program counter. If @var{locspec} resolves to
20323 an address in a different function from the one currently executing, the
20324 results may be bizarre if the two functions expect different patterns
20325 of arguments or of local variables. For this reason, the @code{jump}
20326 command requests confirmation if the jump address is not in the
20327 function currently executing. However, even bizarre results are
20328 predictable if you are well acquainted with the machine-language code
20332 On many systems, you can get much the same effect as the @code{jump}
20333 command by storing a new value into the register @code{$pc}. The
20334 difference is that this does not start your program running; it only
20335 changes the address of where it @emph{will} run when you continue. For
20343 makes the next @code{continue} command or stepping command execute at
20344 address @code{0x485}, rather than at the address where your program stopped.
20345 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20347 The most common occasion to use the @code{jump} command is to back
20348 up---perhaps with more breakpoints set---over a portion of a program
20349 that has already executed, in order to examine its execution in more
20354 @section Giving your Program a Signal
20355 @cindex deliver a signal to a program
20359 @item signal @var{signal}
20360 Resume execution where your program is stopped, but immediately give it the
20361 signal @var{signal}. The @var{signal} can be the name or the number of a
20362 signal. For example, on many systems @code{signal 2} and @code{signal
20363 SIGINT} are both ways of sending an interrupt signal.
20365 Alternatively, if @var{signal} is zero, continue execution without
20366 giving a signal. This is useful when your program stopped on account of
20367 a signal and would ordinarily see the signal when resumed with the
20368 @code{continue} command; @samp{signal 0} causes it to resume without a
20371 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20372 delivered to the currently selected thread, not the thread that last
20373 reported a stop. This includes the situation where a thread was
20374 stopped due to a signal. So if you want to continue execution
20375 suppressing the signal that stopped a thread, you should select that
20376 same thread before issuing the @samp{signal 0} command. If you issue
20377 the @samp{signal 0} command with another thread as the selected one,
20378 @value{GDBN} detects that and asks for confirmation.
20380 Invoking the @code{signal} command is not the same as invoking the
20381 @code{kill} utility from the shell. Sending a signal with @code{kill}
20382 causes @value{GDBN} to decide what to do with the signal depending on
20383 the signal handling tables (@pxref{Signals}). The @code{signal} command
20384 passes the signal directly to your program.
20386 @code{signal} does not repeat when you press @key{RET} a second time
20387 after executing the command.
20389 @kindex queue-signal
20390 @item queue-signal @var{signal}
20391 Queue @var{signal} to be delivered immediately to the current thread
20392 when execution of the thread resumes. The @var{signal} can be the name or
20393 the number of a signal. For example, on many systems @code{signal 2} and
20394 @code{signal SIGINT} are both ways of sending an interrupt signal.
20395 The handling of the signal must be set to pass the signal to the program,
20396 otherwise @value{GDBN} will report an error.
20397 You can control the handling of signals from @value{GDBN} with the
20398 @code{handle} command (@pxref{Signals}).
20400 Alternatively, if @var{signal} is zero, any currently queued signal
20401 for the current thread is discarded and when execution resumes no signal
20402 will be delivered. This is useful when your program stopped on account
20403 of a signal and would ordinarily see the signal when resumed with the
20404 @code{continue} command.
20406 This command differs from the @code{signal} command in that the signal
20407 is just queued, execution is not resumed. And @code{queue-signal} cannot
20408 be used to pass a signal whose handling state has been set to @code{nopass}
20413 @xref{stepping into signal handlers}, for information on how stepping
20414 commands behave when the thread has a signal queued.
20417 @section Returning from a Function
20420 @cindex returning from a function
20423 @itemx return @var{expression}
20424 You can cancel execution of a function call with the @code{return}
20425 command. If you give an
20426 @var{expression} argument, its value is used as the function's return
20430 When you use @code{return}, @value{GDBN} discards the selected stack frame
20431 (and all frames within it). You can think of this as making the
20432 discarded frame return prematurely. If you wish to specify a value to
20433 be returned, give that value as the argument to @code{return}.
20435 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20436 Frame}), and any other frames inside of it, leaving its caller as the
20437 innermost remaining frame. That frame becomes selected. The
20438 specified value is stored in the registers used for returning values
20441 The @code{return} command does not resume execution; it leaves the
20442 program stopped in the state that would exist if the function had just
20443 returned. In contrast, the @code{finish} command (@pxref{Continuing
20444 and Stepping, ,Continuing and Stepping}) resumes execution until the
20445 selected stack frame returns naturally.
20447 @value{GDBN} needs to know how the @var{expression} argument should be set for
20448 the inferior. The concrete registers assignment depends on the OS ABI and the
20449 type being returned by the selected stack frame. For example it is common for
20450 OS ABI to return floating point values in FPU registers while integer values in
20451 CPU registers. Still some ABIs return even floating point values in CPU
20452 registers. Larger integer widths (such as @code{long long int}) also have
20453 specific placement rules. @value{GDBN} already knows the OS ABI from its
20454 current target so it needs to find out also the type being returned to make the
20455 assignment into the right register(s).
20457 Normally, the selected stack frame has debug info. @value{GDBN} will always
20458 use the debug info instead of the implicit type of @var{expression} when the
20459 debug info is available. For example, if you type @kbd{return -1}, and the
20460 function in the current stack frame is declared to return a @code{long long
20461 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20462 into a @code{long long int}:
20465 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20467 (@value{GDBP}) return -1
20468 Make func return now? (y or n) y
20469 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20470 43 printf ("result=%lld\n", func ());
20474 However, if the selected stack frame does not have a debug info, e.g., if the
20475 function was compiled without debug info, @value{GDBN} has to find out the type
20476 to return from user. Specifying a different type by mistake may set the value
20477 in different inferior registers than the caller code expects. For example,
20478 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20479 of a @code{long long int} result for a debug info less function (on 32-bit
20480 architectures). Therefore the user is required to specify the return type by
20481 an appropriate cast explicitly:
20484 Breakpoint 2, 0x0040050b in func ()
20485 (@value{GDBP}) return -1
20486 Return value type not available for selected stack frame.
20487 Please use an explicit cast of the value to return.
20488 (@value{GDBP}) return (long long int) -1
20489 Make selected stack frame return now? (y or n) y
20490 #0 0x00400526 in main ()
20495 @section Calling Program Functions
20498 @cindex calling functions
20499 @cindex inferior functions, calling
20500 @item print @var{expr}
20501 Evaluate the expression @var{expr} and display the resulting value.
20502 The expression may include calls to functions in the program being
20506 @item call @var{expr}
20507 Evaluate the expression @var{expr} without displaying @code{void}
20510 You can use this variant of the @code{print} command if you want to
20511 execute a function from your program that does not return anything
20512 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20513 with @code{void} returned values that @value{GDBN} will otherwise
20514 print. If the result is not void, it is printed and saved in the
20518 It is possible for the function you call via the @code{print} or
20519 @code{call} command to generate a signal (e.g., if there's a bug in
20520 the function, or if you passed it incorrect arguments). What happens
20521 in that case is controlled by the @code{set unwindonsignal} command.
20523 Similarly, with a C@t{++} program it is possible for the function you
20524 call via the @code{print} or @code{call} command to generate an
20525 exception that is not handled due to the constraints of the dummy
20526 frame. In this case, any exception that is raised in the frame, but has
20527 an out-of-frame exception handler will not be found. GDB builds a
20528 dummy-frame for the inferior function call, and the unwinder cannot
20529 seek for exception handlers outside of this dummy-frame. What happens
20530 in that case is controlled by the
20531 @code{set unwind-on-terminating-exception} command.
20534 @item set unwindonsignal
20535 @kindex set unwindonsignal
20536 @cindex unwind stack in called functions
20537 @cindex call dummy stack unwinding
20538 Set unwinding of the stack if a signal is received while in a function
20539 that @value{GDBN} called in the program being debugged. If set to on,
20540 @value{GDBN} unwinds the stack it created for the call and restores
20541 the context to what it was before the call. If set to off (the
20542 default), @value{GDBN} stops in the frame where the signal was
20545 @item show unwindonsignal
20546 @kindex show unwindonsignal
20547 Show the current setting of stack unwinding in the functions called by
20550 @item set unwind-on-terminating-exception
20551 @kindex set unwind-on-terminating-exception
20552 @cindex unwind stack in called functions with unhandled exceptions
20553 @cindex call dummy stack unwinding on unhandled exception.
20554 Set unwinding of the stack if a C@t{++} exception is raised, but left
20555 unhandled while in a function that @value{GDBN} called in the program being
20556 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20557 it created for the call and restores the context to what it was before
20558 the call. If set to off, @value{GDBN} the exception is delivered to
20559 the default C@t{++} exception handler and the inferior terminated.
20561 @item show unwind-on-terminating-exception
20562 @kindex show unwind-on-terminating-exception
20563 Show the current setting of stack unwinding in the functions called by
20566 @item set may-call-functions
20567 @kindex set may-call-functions
20568 @cindex disabling calling functions in the program
20569 @cindex calling functions in the program, disabling
20570 Set permission to call functions in the program.
20571 This controls whether @value{GDBN} will attempt to call functions in
20572 the program, such as with expressions in the @code{print} command. It
20573 defaults to @code{on}.
20575 To call a function in the program, @value{GDBN} has to temporarily
20576 modify the state of the inferior. This has potentially undesired side
20577 effects. Also, having @value{GDBN} call nested functions is likely to
20578 be erroneous and may even crash the program being debugged. You can
20579 avoid such hazards by forbidding @value{GDBN} from calling functions
20580 in the program being debugged. If calling functions in the program
20581 is forbidden, GDB will throw an error when a command (such as printing
20582 an expression) starts a function call in the program.
20584 @item show may-call-functions
20585 @kindex show may-call-functions
20586 Show permission to call functions in the program.
20590 @subsection Calling functions with no debug info
20592 @cindex no debug info functions
20593 Sometimes, a function you wish to call is missing debug information.
20594 In such case, @value{GDBN} does not know the type of the function,
20595 including the types of the function's parameters. To avoid calling
20596 the inferior function incorrectly, which could result in the called
20597 function functioning erroneously and even crash, @value{GDBN} refuses
20598 to call the function unless you tell it the type of the function.
20600 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20601 to do that. The simplest is to cast the call to the function's
20602 declared return type. For example:
20605 (@value{GDBP}) p getenv ("PATH")
20606 'getenv' has unknown return type; cast the call to its declared return type
20607 (@value{GDBP}) p (char *) getenv ("PATH")
20608 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20611 Casting the return type of a no-debug function is equivalent to
20612 casting the function to a pointer to a prototyped function that has a
20613 prototype that matches the types of the passed-in arguments, and
20614 calling that. I.e., the call above is equivalent to:
20617 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20621 and given this prototyped C or C++ function with float parameters:
20624 float multiply (float v1, float v2) @{ return v1 * v2; @}
20628 these calls are equivalent:
20631 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20632 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20635 If the function you wish to call is declared as unprototyped (i.e.@:
20636 old K&R style), you must use the cast-to-function-pointer syntax, so
20637 that @value{GDBN} knows that it needs to apply default argument
20638 promotions (promote float arguments to double). @xref{ABI, float
20639 promotion}. For example, given this unprototyped C function with
20640 float parameters, and no debug info:
20644 multiply_noproto (v1, v2)
20652 you call it like this:
20655 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20659 @section Patching Programs
20661 @cindex patching binaries
20662 @cindex writing into executables
20663 @cindex writing into corefiles
20665 By default, @value{GDBN} opens the file containing your program's
20666 executable code (or the corefile) read-only. This prevents accidental
20667 alterations to machine code; but it also prevents you from intentionally
20668 patching your program's binary.
20670 If you'd like to be able to patch the binary, you can specify that
20671 explicitly with the @code{set write} command. For example, you might
20672 want to turn on internal debugging flags, or even to make emergency
20678 @itemx set write off
20679 If you specify @samp{set write on}, @value{GDBN} opens executable and
20680 core files for both reading and writing; if you specify @kbd{set write
20681 off} (the default), @value{GDBN} opens them read-only.
20683 If you have already loaded a file, you must load it again (using the
20684 @code{exec-file} or @code{core-file} command) after changing @code{set
20685 write}, for your new setting to take effect.
20689 Display whether executable files and core files are opened for writing
20690 as well as reading.
20693 @node Compiling and Injecting Code
20694 @section Compiling and injecting code in @value{GDBN}
20695 @cindex injecting code
20696 @cindex writing into executables
20697 @cindex compiling code
20699 @value{GDBN} supports on-demand compilation and code injection into
20700 programs running under @value{GDBN}. GCC 5.0 or higher built with
20701 @file{libcc1.so} must be installed for this functionality to be enabled.
20702 This functionality is implemented with the following commands.
20705 @kindex compile code
20706 @item compile code @var{source-code}
20707 @itemx compile code -raw @var{--} @var{source-code}
20708 Compile @var{source-code} with the compiler language found as the current
20709 language in @value{GDBN} (@pxref{Languages}). If compilation and
20710 injection is not supported with the current language specified in
20711 @value{GDBN}, or the compiler does not support this feature, an error
20712 message will be printed. If @var{source-code} compiles and links
20713 successfully, @value{GDBN} will load the object-code emitted,
20714 and execute it within the context of the currently selected inferior.
20715 It is important to note that the compiled code is executed immediately.
20716 After execution, the compiled code is removed from @value{GDBN} and any
20717 new types or variables you have defined will be deleted.
20719 The command allows you to specify @var{source-code} in two ways.
20720 The simplest method is to provide a single line of code to the command.
20724 compile code printf ("hello world\n");
20727 If you specify options on the command line as well as source code, they
20728 may conflict. The @samp{--} delimiter can be used to separate options
20729 from actual source code. E.g.:
20732 compile code -r -- printf ("hello world\n");
20735 Alternatively you can enter source code as multiple lines of text. To
20736 enter this mode, invoke the @samp{compile code} command without any text
20737 following the command. This will start the multiple-line editor and
20738 allow you to type as many lines of source code as required. When you
20739 have completed typing, enter @samp{end} on its own line to exit the
20744 >printf ("hello\n");
20745 >printf ("world\n");
20749 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20750 provided @var{source-code} in a callable scope. In this case, you must
20751 specify the entry point of the code by defining a function named
20752 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20753 inferior. Using @samp{-raw} option may be needed for example when
20754 @var{source-code} requires @samp{#include} lines which may conflict with
20755 inferior symbols otherwise.
20757 @kindex compile file
20758 @item compile file @var{filename}
20759 @itemx compile file -raw @var{filename}
20760 Like @code{compile code}, but take the source code from @var{filename}.
20763 compile file /home/user/example.c
20768 @item compile print [[@var{options}] --] @var{expr}
20769 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20770 Compile and execute @var{expr} with the compiler language found as the
20771 current language in @value{GDBN} (@pxref{Languages}). By default the
20772 value of @var{expr} is printed in a format appropriate to its data type;
20773 you can choose a different format by specifying @samp{/@var{f}}, where
20774 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20775 Formats}. The @code{compile print} command accepts the same options
20776 as the @code{print} command; see @ref{print options}.
20778 @item compile print [[@var{options}] --]
20779 @itemx compile print [[@var{options}] --] /@var{f}
20780 @cindex reprint the last value
20781 Alternatively you can enter the expression (source code producing it) as
20782 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20783 command without any text following the command. This will start the
20784 multiple-line editor.
20788 The process of compiling and injecting the code can be inspected using:
20791 @anchor{set debug compile}
20792 @item set debug compile
20793 @cindex compile command debugging info
20794 Turns on or off display of @value{GDBN} process of compiling and
20795 injecting the code. The default is off.
20797 @item show debug compile
20798 Displays the current state of displaying @value{GDBN} process of
20799 compiling and injecting the code.
20801 @anchor{set debug compile-cplus-types}
20802 @item set debug compile-cplus-types
20803 @cindex compile C@t{++} type conversion
20804 Turns on or off the display of C@t{++} type conversion debugging information.
20805 The default is off.
20807 @item show debug compile-cplus-types
20808 Displays the current state of displaying debugging information for
20809 C@t{++} type conversion.
20812 @subsection Compilation options for the @code{compile} command
20814 @value{GDBN} needs to specify the right compilation options for the code
20815 to be injected, in part to make its ABI compatible with the inferior
20816 and in part to make the injected code compatible with @value{GDBN}'s
20820 The options used, in increasing precedence:
20823 @item target architecture and OS options (@code{gdbarch})
20824 These options depend on target processor type and target operating
20825 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20826 (@code{-m64}) compilation option.
20828 @item compilation options recorded in the target
20829 @value{NGCC} (since version 4.7) stores the options used for compilation
20830 into @code{DW_AT_producer} part of DWARF debugging information according
20831 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20832 explicitly specify @code{-g} during inferior compilation otherwise
20833 @value{NGCC} produces no DWARF. This feature is only relevant for
20834 platforms where @code{-g} produces DWARF by default, otherwise one may
20835 try to enforce DWARF by using @code{-gdwarf-4}.
20837 @item compilation options set by @code{set compile-args}
20841 You can override compilation options using the following command:
20844 @item set compile-args
20845 @cindex compile command options override
20846 Set compilation options used for compiling and injecting code with the
20847 @code{compile} commands. These options override any conflicting ones
20848 from the target architecture and/or options stored during inferior
20851 @item show compile-args
20852 Displays the current state of compilation options override.
20853 This does not show all the options actually used during compilation,
20854 use @ref{set debug compile} for that.
20857 @subsection Caveats when using the @code{compile} command
20859 There are a few caveats to keep in mind when using the @code{compile}
20860 command. As the caveats are different per language, the table below
20861 highlights specific issues on a per language basis.
20864 @item C code examples and caveats
20865 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20866 attempt to compile the source code with a @samp{C} compiler. The source
20867 code provided to the @code{compile} command will have much the same
20868 access to variables and types as it normally would if it were part of
20869 the program currently being debugged in @value{GDBN}.
20871 Below is a sample program that forms the basis of the examples that
20872 follow. This program has been compiled and loaded into @value{GDBN},
20873 much like any other normal debugging session.
20876 void function1 (void)
20879 printf ("function 1\n");
20882 void function2 (void)
20897 For the purposes of the examples in this section, the program above has
20898 been compiled, loaded into @value{GDBN}, stopped at the function
20899 @code{main}, and @value{GDBN} is awaiting input from the user.
20901 To access variables and types for any program in @value{GDBN}, the
20902 program must be compiled and packaged with debug information. The
20903 @code{compile} command is not an exception to this rule. Without debug
20904 information, you can still use the @code{compile} command, but you will
20905 be very limited in what variables and types you can access.
20907 So with that in mind, the example above has been compiled with debug
20908 information enabled. The @code{compile} command will have access to
20909 all variables and types (except those that may have been optimized
20910 out). Currently, as @value{GDBN} has stopped the program in the
20911 @code{main} function, the @code{compile} command would have access to
20912 the variable @code{k}. You could invoke the @code{compile} command
20913 and type some source code to set the value of @code{k}. You can also
20914 read it, or do anything with that variable you would normally do in
20915 @code{C}. Be aware that changes to inferior variables in the
20916 @code{compile} command are persistent. In the following example:
20919 compile code k = 3;
20923 the variable @code{k} is now 3. It will retain that value until
20924 something else in the example program changes it, or another
20925 @code{compile} command changes it.
20927 Normal scope and access rules apply to source code compiled and
20928 injected by the @code{compile} command. In the example, the variables
20929 @code{j} and @code{k} are not accessible yet, because the program is
20930 currently stopped in the @code{main} function, where these variables
20931 are not in scope. Therefore, the following command
20934 compile code j = 3;
20938 will result in a compilation error message.
20940 Once the program is continued, execution will bring these variables in
20941 scope, and they will become accessible; then the code you specify via
20942 the @code{compile} command will be able to access them.
20944 You can create variables and types with the @code{compile} command as
20945 part of your source code. Variables and types that are created as part
20946 of the @code{compile} command are not visible to the rest of the program for
20947 the duration of its run. This example is valid:
20950 compile code int ff = 5; printf ("ff is %d\n", ff);
20953 However, if you were to type the following into @value{GDBN} after that
20954 command has completed:
20957 compile code printf ("ff is %d\n'', ff);
20961 a compiler error would be raised as the variable @code{ff} no longer
20962 exists. Object code generated and injected by the @code{compile}
20963 command is removed when its execution ends. Caution is advised
20964 when assigning to program variables values of variables created by the
20965 code submitted to the @code{compile} command. This example is valid:
20968 compile code int ff = 5; k = ff;
20971 The value of the variable @code{ff} is assigned to @code{k}. The variable
20972 @code{k} does not require the existence of @code{ff} to maintain the value
20973 it has been assigned. However, pointers require particular care in
20974 assignment. If the source code compiled with the @code{compile} command
20975 changed the address of a pointer in the example program, perhaps to a
20976 variable created in the @code{compile} command, that pointer would point
20977 to an invalid location when the command exits. The following example
20978 would likely cause issues with your debugged program:
20981 compile code int ff = 5; p = &ff;
20984 In this example, @code{p} would point to @code{ff} when the
20985 @code{compile} command is executing the source code provided to it.
20986 However, as variables in the (example) program persist with their
20987 assigned values, the variable @code{p} would point to an invalid
20988 location when the command exists. A general rule should be followed
20989 in that you should either assign @code{NULL} to any assigned pointers,
20990 or restore a valid location to the pointer before the command exits.
20992 Similar caution must be exercised with any structs, unions, and typedefs
20993 defined in @code{compile} command. Types defined in the @code{compile}
20994 command will no longer be available in the next @code{compile} command.
20995 Therefore, if you cast a variable to a type defined in the
20996 @code{compile} command, care must be taken to ensure that any future
20997 need to resolve the type can be achieved.
21000 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
21001 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
21002 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
21003 Compilation failed.
21004 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
21008 Variables that have been optimized away by the compiler are not
21009 accessible to the code submitted to the @code{compile} command.
21010 Access to those variables will generate a compiler error which @value{GDBN}
21011 will print to the console.
21014 @subsection Compiler search for the @code{compile} command
21016 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21017 which may not be obvious for remote targets of different architecture
21018 than where @value{GDBN} is running. Environment variable @env{PATH} on
21019 @value{GDBN} host is searched for @value{NGCC} binary matching the
21020 target architecture and operating system. This search can be overriden
21021 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21022 taken from shell that executed @value{GDBN}, it is not the value set by
21023 @value{GDBN} command @code{set environment}). @xref{Environment}.
21026 Specifically @env{PATH} is searched for binaries matching regular expression
21027 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21028 debugged. @var{arch} is processor name --- multiarch is supported, so for
21029 example both @code{i386} and @code{x86_64} targets look for pattern
21030 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21031 for pattern @code{s390x?}. @var{os} is currently supported only for
21032 pattern @code{linux(-gnu)?}.
21034 On Posix hosts the compiler driver @value{GDBN} needs to find also
21035 shared library @file{libcc1.so} from the compiler. It is searched in
21036 default shared library search path (overridable with usual environment
21037 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21038 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21039 according to the installation of the found compiler --- as possibly
21040 specified by the @code{set compile-gcc} command.
21043 @item set compile-gcc
21044 @cindex compile command driver filename override
21045 Set compilation command used for compiling and injecting code with the
21046 @code{compile} commands. If this option is not set (it is set to
21047 an empty string), the search described above will occur --- that is the
21050 @item show compile-gcc
21051 Displays the current compile command @value{NGCC} driver filename.
21052 If set, it is the main command @command{gcc}, found usually for example
21053 under name @file{x86_64-linux-gnu-gcc}.
21057 @chapter @value{GDBN} Files
21059 @value{GDBN} needs to know the file name of the program to be debugged,
21060 both in order to read its symbol table and in order to start your
21061 program. To debug a core dump of a previous run, you must also tell
21062 @value{GDBN} the name of the core dump file.
21065 * Files:: Commands to specify files
21066 * File Caching:: Information about @value{GDBN}'s file caching
21067 * Separate Debug Files:: Debugging information in separate files
21068 * MiniDebugInfo:: Debugging information in a special section
21069 * Index Files:: Index files speed up GDB
21070 * Symbol Errors:: Errors reading symbol files
21071 * Data Files:: GDB data files
21075 @section Commands to Specify Files
21077 @cindex symbol table
21078 @cindex core dump file
21080 You may want to specify executable and core dump file names. The usual
21081 way to do this is at start-up time, using the arguments to
21082 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21083 Out of @value{GDBN}}).
21085 Occasionally it is necessary to change to a different file during a
21086 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21087 specify a file you want to use. Or you are debugging a remote target
21088 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21089 Program}). In these situations the @value{GDBN} commands to specify
21090 new files are useful.
21093 @cindex executable file
21095 @item file @var{filename}
21096 Use @var{filename} as the program to be debugged. It is read for its
21097 symbols and for the contents of pure memory. It is also the program
21098 executed when you use the @code{run} command. If you do not specify a
21099 directory and the file is not found in the @value{GDBN} working directory,
21100 @value{GDBN} uses the environment variable @env{PATH} as a list of
21101 directories to search, just as the shell does when looking for a program
21102 to run. You can change the value of this variable, for both @value{GDBN}
21103 and your program, using the @code{path} command.
21105 @cindex unlinked object files
21106 @cindex patching object files
21107 You can load unlinked object @file{.o} files into @value{GDBN} using
21108 the @code{file} command. You will not be able to ``run'' an object
21109 file, but you can disassemble functions and inspect variables. Also,
21110 if the underlying BFD functionality supports it, you could use
21111 @kbd{gdb -write} to patch object files using this technique. Note
21112 that @value{GDBN} can neither interpret nor modify relocations in this
21113 case, so branches and some initialized variables will appear to go to
21114 the wrong place. But this feature is still handy from time to time.
21117 @code{file} with no argument makes @value{GDBN} discard any information it
21118 has on both executable file and the symbol table.
21121 @item exec-file @r{[} @var{filename} @r{]}
21122 Specify that the program to be run (but not the symbol table) is found
21123 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21124 if necessary to locate your program. Omitting @var{filename} means to
21125 discard information on the executable file.
21127 @kindex symbol-file
21128 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21129 Read symbol table information from file @var{filename}. @env{PATH} is
21130 searched when necessary. Use the @code{file} command to get both symbol
21131 table and program to run from the same file.
21133 If an optional @var{offset} is specified, it is added to the start
21134 address of each section in the symbol file. This is useful if the
21135 program is relocated at runtime, such as the Linux kernel with kASLR
21138 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21139 program's symbol table.
21141 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21142 some breakpoints and auto-display expressions. This is because they may
21143 contain pointers to the internal data recording symbols and data types,
21144 which are part of the old symbol table data being discarded inside
21147 @code{symbol-file} does not repeat if you press @key{RET} again after
21150 When @value{GDBN} is configured for a particular environment, it
21151 understands debugging information in whatever format is the standard
21152 generated for that environment; you may use either a @sc{gnu} compiler, or
21153 other compilers that adhere to the local conventions.
21154 Best results are usually obtained from @sc{gnu} compilers; for example,
21155 using @code{@value{NGCC}} you can generate debugging information for
21158 For most kinds of object files, with the exception of old SVR3 systems
21159 using COFF, the @code{symbol-file} command does not normally read the
21160 symbol table in full right away. Instead, it scans the symbol table
21161 quickly to find which source files and which symbols are present. The
21162 details are read later, one source file at a time, as they are needed.
21164 The purpose of this two-stage reading strategy is to make @value{GDBN}
21165 start up faster. For the most part, it is invisible except for
21166 occasional pauses while the symbol table details for a particular source
21167 file are being read. (The @code{set verbose} command can turn these
21168 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21169 Warnings and Messages}.)
21171 We have not implemented the two-stage strategy for COFF yet. When the
21172 symbol table is stored in COFF format, @code{symbol-file} reads the
21173 symbol table data in full right away. Note that ``stabs-in-COFF''
21174 still does the two-stage strategy, since the debug info is actually
21178 @cindex reading symbols immediately
21179 @cindex symbols, reading immediately
21180 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21181 @itemx file @r{[} -readnow @r{]} @var{filename}
21182 You can override the @value{GDBN} two-stage strategy for reading symbol
21183 tables by using the @samp{-readnow} option with any of the commands that
21184 load symbol table information, if you want to be sure @value{GDBN} has the
21185 entire symbol table available.
21187 @cindex @code{-readnever}, option for symbol-file command
21188 @cindex never read symbols
21189 @cindex symbols, never read
21190 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21191 @itemx file @r{[} -readnever @r{]} @var{filename}
21192 You can instruct @value{GDBN} to never read the symbolic information
21193 contained in @var{filename} by using the @samp{-readnever} option.
21194 @xref{--readnever}.
21196 @c FIXME: for now no mention of directories, since this seems to be in
21197 @c flux. 13mar1992 status is that in theory GDB would look either in
21198 @c current dir or in same dir as myprog; but issues like competing
21199 @c GDB's, or clutter in system dirs, mean that in practice right now
21200 @c only current dir is used. FFish says maybe a special GDB hierarchy
21201 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21205 @item core-file @r{[}@var{filename}@r{]}
21207 Specify the whereabouts of a core dump file to be used as the ``contents
21208 of memory''. Traditionally, core files contain only some parts of the
21209 address space of the process that generated them; @value{GDBN} can access the
21210 executable file itself for other parts.
21212 @code{core-file} with no argument specifies that no core file is
21215 Note that the core file is ignored when your program is actually running
21216 under @value{GDBN}. So, if you have been running your program and you
21217 wish to debug a core file instead, you must kill the subprocess in which
21218 the program is running. To do this, use the @code{kill} command
21219 (@pxref{Kill Process, ,Killing the Child Process}).
21221 @kindex add-symbol-file
21222 @cindex dynamic linking
21223 @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{]}
21224 The @code{add-symbol-file} command reads additional symbol table
21225 information from the file @var{filename}. You would use this command
21226 when @var{filename} has been dynamically loaded (by some other means)
21227 into the program that is running. The @var{textaddress} parameter gives
21228 the memory address at which the file's text section has been loaded.
21229 You can additionally specify the base address of other sections using
21230 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21231 If a section is omitted, @value{GDBN} will use its default addresses
21232 as found in @var{filename}. Any @var{address} or @var{textaddress}
21233 can be given as an expression.
21235 If an optional @var{offset} is specified, it is added to the start
21236 address of each section, except those for which the address was
21237 specified explicitly.
21239 The symbol table of the file @var{filename} is added to the symbol table
21240 originally read with the @code{symbol-file} command. You can use the
21241 @code{add-symbol-file} command any number of times; the new symbol data
21242 thus read is kept in addition to the old.
21244 Changes can be reverted using the command @code{remove-symbol-file}.
21246 @cindex relocatable object files, reading symbols from
21247 @cindex object files, relocatable, reading symbols from
21248 @cindex reading symbols from relocatable object files
21249 @cindex symbols, reading from relocatable object files
21250 @cindex @file{.o} files, reading symbols from
21251 Although @var{filename} is typically a shared library file, an
21252 executable file, or some other object file which has been fully
21253 relocated for loading into a process, you can also load symbolic
21254 information from relocatable @file{.o} files, as long as:
21258 the file's symbolic information refers only to linker symbols defined in
21259 that file, not to symbols defined by other object files,
21261 every section the file's symbolic information refers to has actually
21262 been loaded into the inferior, as it appears in the file, and
21264 you can determine the address at which every section was loaded, and
21265 provide these to the @code{add-symbol-file} command.
21269 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21270 relocatable files into an already running program; such systems
21271 typically make the requirements above easy to meet. However, it's
21272 important to recognize that many native systems use complex link
21273 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21274 assembly, for example) that make the requirements difficult to meet. In
21275 general, one cannot assume that using @code{add-symbol-file} to read a
21276 relocatable object file's symbolic information will have the same effect
21277 as linking the relocatable object file into the program in the normal
21280 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21282 @kindex remove-symbol-file
21283 @item remove-symbol-file @var{filename}
21284 @item remove-symbol-file -a @var{address}
21285 Remove a symbol file added via the @code{add-symbol-file} command. The
21286 file to remove can be identified by its @var{filename} or by an @var{address}
21287 that lies within the boundaries of this symbol file in memory. Example:
21290 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21291 add symbol table from file "/home/user/gdb/mylib.so" at
21292 .text_addr = 0x7ffff7ff9480
21294 Reading symbols from /home/user/gdb/mylib.so...
21295 (gdb) remove-symbol-file -a 0x7ffff7ff9480
21296 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21301 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21303 @kindex add-symbol-file-from-memory
21304 @cindex @code{syscall DSO}
21305 @cindex load symbols from memory
21306 @item add-symbol-file-from-memory @var{address}
21307 Load symbols from the given @var{address} in a dynamically loaded
21308 object file whose image is mapped directly into the inferior's memory.
21309 For example, the Linux kernel maps a @code{syscall DSO} into each
21310 process's address space; this DSO provides kernel-specific code for
21311 some system calls. The argument can be any expression whose
21312 evaluation yields the address of the file's shared object file header.
21313 For this command to work, you must have used @code{symbol-file} or
21314 @code{exec-file} commands in advance.
21317 @item section @var{section} @var{addr}
21318 The @code{section} command changes the base address of the named
21319 @var{section} of the exec file to @var{addr}. This can be used if the
21320 exec file does not contain section addresses, (such as in the
21321 @code{a.out} format), or when the addresses specified in the file
21322 itself are wrong. Each section must be changed separately. The
21323 @code{info files} command, described below, lists all the sections and
21327 @kindex info target
21330 @code{info files} and @code{info target} are synonymous; both print the
21331 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21332 including the names of the executable and core dump files currently in
21333 use by @value{GDBN}, and the files from which symbols were loaded. The
21334 command @code{help target} lists all possible targets rather than
21337 @kindex maint info sections
21338 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21339 Another command that can give you extra information about program sections
21340 is @code{maint info sections}. In addition to the section information
21341 displayed by @code{info files}, this command displays the flags and file
21342 offset of each section in the executable and core dump files.
21344 When @samp{-all-objects} is passed then sections from all loaded object
21345 files, including shared libraries, are printed.
21347 The optional @var{filter-list} is a space separated list of filter
21348 keywords. Sections that match any one of the filter criteria will be
21349 printed. There are two types of filter:
21352 @item @var{section-name}
21353 Display information about any section named @var{section-name}.
21354 @item @var{section-flag}
21355 Display information for any section with @var{section-flag}. The
21356 section flags that @value{GDBN} currently knows about are:
21359 Section will have space allocated in the process when loaded.
21360 Set for all sections except those containing debug information.
21362 Section will be loaded from the file into the child process memory.
21363 Set for pre-initialized code and data, clear for @code{.bss} sections.
21365 Section needs to be relocated before loading.
21367 Section cannot be modified by the child process.
21369 Section contains executable code only.
21371 Section contains data only (no executable code).
21373 Section will reside in ROM.
21375 Section contains data for constructor/destructor lists.
21377 Section is not empty.
21379 An instruction to the linker to not output the section.
21380 @item COFF_SHARED_LIBRARY
21381 A notification to the linker that the section contains
21382 COFF shared library information.
21384 Section contains common symbols.
21388 @kindex maint info target-sections
21389 @item maint info target-sections
21390 This command prints @value{GDBN}'s internal section table. For each
21391 target @value{GDBN} maintains a table containing the allocatable
21392 sections from all currently mapped objects, along with information
21393 about where the section is mapped.
21395 @kindex set trust-readonly-sections
21396 @cindex read-only sections
21397 @item set trust-readonly-sections on
21398 Tell @value{GDBN} that readonly sections in your object file
21399 really are read-only (i.e.@: that their contents will not change).
21400 In that case, @value{GDBN} can fetch values from these sections
21401 out of the object file, rather than from the target program.
21402 For some targets (notably embedded ones), this can be a significant
21403 enhancement to debugging performance.
21405 The default is off.
21407 @item set trust-readonly-sections off
21408 Tell @value{GDBN} not to trust readonly sections. This means that
21409 the contents of the section might change while the program is running,
21410 and must therefore be fetched from the target when needed.
21412 @item show trust-readonly-sections
21413 Show the current setting of trusting readonly sections.
21416 All file-specifying commands allow both absolute and relative file names
21417 as arguments. @value{GDBN} always converts the file name to an absolute file
21418 name and remembers it that way.
21420 @cindex shared libraries
21421 @anchor{Shared Libraries}
21422 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21423 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21424 DSBT (TIC6X) shared libraries.
21426 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21427 shared libraries. @xref{Expat}.
21429 @value{GDBN} automatically loads symbol definitions from shared libraries
21430 when you use the @code{run} command, or when you examine a core file.
21431 (Before you issue the @code{run} command, @value{GDBN} does not understand
21432 references to a function in a shared library, however---unless you are
21433 debugging a core file).
21435 @c FIXME: some @value{GDBN} release may permit some refs to undef
21436 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21437 @c FIXME...lib; check this from time to time when updating manual
21439 There are times, however, when you may wish to not automatically load
21440 symbol definitions from shared libraries, such as when they are
21441 particularly large or there are many of them.
21443 To control the automatic loading of shared library symbols, use the
21447 @kindex set auto-solib-add
21448 @item set auto-solib-add @var{mode}
21449 If @var{mode} is @code{on}, symbols from all shared object libraries
21450 will be loaded automatically when the inferior begins execution, you
21451 attach to an independently started inferior, or when the dynamic linker
21452 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21453 is @code{off}, symbols must be loaded manually, using the
21454 @code{sharedlibrary} command. The default value is @code{on}.
21456 @cindex memory used for symbol tables
21457 If your program uses lots of shared libraries with debug info that
21458 takes large amounts of memory, you can decrease the @value{GDBN}
21459 memory footprint by preventing it from automatically loading the
21460 symbols from shared libraries. To that end, type @kbd{set
21461 auto-solib-add off} before running the inferior, then load each
21462 library whose debug symbols you do need with @kbd{sharedlibrary
21463 @var{regexp}}, where @var{regexp} is a regular expression that matches
21464 the libraries whose symbols you want to be loaded.
21466 @kindex show auto-solib-add
21467 @item show auto-solib-add
21468 Display the current autoloading mode.
21471 @cindex load shared library
21472 To explicitly load shared library symbols, use the @code{sharedlibrary}
21476 @kindex info sharedlibrary
21478 @item info share @var{regex}
21479 @itemx info sharedlibrary @var{regex}
21480 Print the names of the shared libraries which are currently loaded
21481 that match @var{regex}. If @var{regex} is omitted then print
21482 all shared libraries that are loaded.
21485 @item info dll @var{regex}
21486 This is an alias of @code{info sharedlibrary}.
21488 @kindex sharedlibrary
21490 @item sharedlibrary @var{regex}
21491 @itemx share @var{regex}
21492 Load shared object library symbols for files matching a
21493 Unix regular expression.
21494 As with files loaded automatically, it only loads shared libraries
21495 required by your program for a core file or after typing @code{run}. If
21496 @var{regex} is omitted all shared libraries required by your program are
21499 @item nosharedlibrary
21500 @kindex nosharedlibrary
21501 @cindex unload symbols from shared libraries
21502 Unload all shared object library symbols. This discards all symbols
21503 that have been loaded from all shared libraries. Symbols from shared
21504 libraries that were loaded by explicit user requests are not
21508 Sometimes you may wish that @value{GDBN} stops and gives you control
21509 when any of shared library events happen. The best way to do this is
21510 to use @code{catch load} and @code{catch unload} (@pxref{Set
21513 @value{GDBN} also supports the @code{set stop-on-solib-events}
21514 command for this. This command exists for historical reasons. It is
21515 less useful than setting a catchpoint, because it does not allow for
21516 conditions or commands as a catchpoint does.
21519 @item set stop-on-solib-events
21520 @kindex set stop-on-solib-events
21521 This command controls whether @value{GDBN} should give you control
21522 when the dynamic linker notifies it about some shared library event.
21523 The most common event of interest is loading or unloading of a new
21526 @item show stop-on-solib-events
21527 @kindex show stop-on-solib-events
21528 Show whether @value{GDBN} stops and gives you control when shared
21529 library events happen.
21532 Shared libraries are also supported in many cross or remote debugging
21533 configurations. @value{GDBN} needs to have access to the target's libraries;
21534 this can be accomplished either by providing copies of the libraries
21535 on the host system, or by asking @value{GDBN} to automatically retrieve the
21536 libraries from the target. If copies of the target libraries are
21537 provided, they need to be the same as the target libraries, although the
21538 copies on the target can be stripped as long as the copies on the host are
21541 @cindex where to look for shared libraries
21542 For remote debugging, you need to tell @value{GDBN} where the target
21543 libraries are, so that it can load the correct copies---otherwise, it
21544 may try to load the host's libraries. @value{GDBN} has two variables
21545 to specify the search directories for target libraries.
21548 @cindex prefix for executable and shared library file names
21549 @cindex system root, alternate
21550 @kindex set solib-absolute-prefix
21551 @kindex set sysroot
21552 @item set sysroot @var{path}
21553 Use @var{path} as the system root for the program being debugged. Any
21554 absolute shared library paths will be prefixed with @var{path}; many
21555 runtime loaders store the absolute paths to the shared library in the
21556 target program's memory. When starting processes remotely, and when
21557 attaching to already-running processes (local or remote), their
21558 executable filenames will be prefixed with @var{path} if reported to
21559 @value{GDBN} as absolute by the operating system. If you use
21560 @code{set sysroot} to find executables and shared libraries, they need
21561 to be laid out in the same way that they are on the target, with
21562 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21565 If @var{path} starts with the sequence @file{target:} and the target
21566 system is remote then @value{GDBN} will retrieve the target binaries
21567 from the remote system. This is only supported when using a remote
21568 target that supports the @code{remote get} command (@pxref{File
21569 Transfer,,Sending files to a remote system}). The part of @var{path}
21570 following the initial @file{target:} (if present) is used as system
21571 root prefix on the remote file system. If @var{path} starts with the
21572 sequence @file{remote:} this is converted to the sequence
21573 @file{target:} by @code{set sysroot}@footnote{Historically the
21574 functionality to retrieve binaries from the remote system was
21575 provided by prefixing @var{path} with @file{remote:}}. If you want
21576 to specify a local system root using a directory that happens to be
21577 named @file{target:} or @file{remote:}, you need to use some
21578 equivalent variant of the name like @file{./target:}.
21580 For targets with an MS-DOS based filesystem, such as MS-Windows,
21581 @value{GDBN} tries prefixing a few variants of the target
21582 absolute file name with @var{path}. But first, on Unix hosts,
21583 @value{GDBN} converts all backslash directory separators into forward
21584 slashes, because the backslash is not a directory separator on Unix:
21587 c:\foo\bar.dll @result{} c:/foo/bar.dll
21590 Then, @value{GDBN} attempts prefixing the target file name with
21591 @var{path}, and looks for the resulting file name in the host file
21595 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21598 If that does not find the binary, @value{GDBN} tries removing
21599 the @samp{:} character from the drive spec, both for convenience, and,
21600 for the case of the host file system not supporting file names with
21604 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21607 This makes it possible to have a system root that mirrors a target
21608 with more than one drive. E.g., you may want to setup your local
21609 copies of the target system shared libraries like so (note @samp{c} vs
21613 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21614 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21615 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21619 and point the system root at @file{/path/to/sysroot}, so that
21620 @value{GDBN} can find the correct copies of both
21621 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21623 If that still does not find the binary, @value{GDBN} tries
21624 removing the whole drive spec from the target file name:
21627 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21630 This last lookup makes it possible to not care about the drive name,
21631 if you don't want or need to.
21633 The @code{set solib-absolute-prefix} command is an alias for @code{set
21636 @cindex default system root
21637 @cindex @samp{--with-sysroot}
21638 You can set the default system root by using the configure-time
21639 @samp{--with-sysroot} option. If the system root is inside
21640 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21641 @samp{--exec-prefix}), then the default system root will be updated
21642 automatically if the installed @value{GDBN} is moved to a new
21645 @kindex show sysroot
21647 Display the current executable and shared library prefix.
21649 @kindex set solib-search-path
21650 @item set solib-search-path @var{path}
21651 If this variable is set, @var{path} is a colon-separated list of
21652 directories to search for shared libraries. @samp{solib-search-path}
21653 is used after @samp{sysroot} fails to locate the library, or if the
21654 path to the library is relative instead of absolute. If you want to
21655 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21656 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21657 finding your host's libraries. @samp{sysroot} is preferred; setting
21658 it to a nonexistent directory may interfere with automatic loading
21659 of shared library symbols.
21661 @kindex show solib-search-path
21662 @item show solib-search-path
21663 Display the current shared library search path.
21665 @cindex DOS file-name semantics of file names.
21666 @kindex set target-file-system-kind (unix|dos-based|auto)
21667 @kindex show target-file-system-kind
21668 @item set target-file-system-kind @var{kind}
21669 Set assumed file system kind for target reported file names.
21671 Shared library file names as reported by the target system may not
21672 make sense as is on the system @value{GDBN} is running on. For
21673 example, when remote debugging a target that has MS-DOS based file
21674 system semantics, from a Unix host, the target may be reporting to
21675 @value{GDBN} a list of loaded shared libraries with file names such as
21676 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21677 drive letters, so the @samp{c:\} prefix is not normally understood as
21678 indicating an absolute file name, and neither is the backslash
21679 normally considered a directory separator character. In that case,
21680 the native file system would interpret this whole absolute file name
21681 as a relative file name with no directory components. This would make
21682 it impossible to point @value{GDBN} at a copy of the remote target's
21683 shared libraries on the host using @code{set sysroot}, and impractical
21684 with @code{set solib-search-path}. Setting
21685 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21686 to interpret such file names similarly to how the target would, and to
21687 map them to file names valid on @value{GDBN}'s native file system
21688 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21689 to one of the supported file system kinds. In that case, @value{GDBN}
21690 tries to determine the appropriate file system variant based on the
21691 current target's operating system (@pxref{ABI, ,Configuring the
21692 Current ABI}). The supported file system settings are:
21696 Instruct @value{GDBN} to assume the target file system is of Unix
21697 kind. Only file names starting the forward slash (@samp{/}) character
21698 are considered absolute, and the directory separator character is also
21702 Instruct @value{GDBN} to assume the target file system is DOS based.
21703 File names starting with either a forward slash, or a drive letter
21704 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21705 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21706 considered directory separators.
21709 Instruct @value{GDBN} to use the file system kind associated with the
21710 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21711 This is the default.
21715 @cindex file name canonicalization
21716 @cindex base name differences
21717 When processing file names provided by the user, @value{GDBN}
21718 frequently needs to compare them to the file names recorded in the
21719 program's debug info. Normally, @value{GDBN} compares just the
21720 @dfn{base names} of the files as strings, which is reasonably fast
21721 even for very large programs. (The base name of a file is the last
21722 portion of its name, after stripping all the leading directories.)
21723 This shortcut in comparison is based upon the assumption that files
21724 cannot have more than one base name. This is usually true, but
21725 references to files that use symlinks or similar filesystem
21726 facilities violate that assumption. If your program records files
21727 using such facilities, or if you provide file names to @value{GDBN}
21728 using symlinks etc., you can set @code{basenames-may-differ} to
21729 @code{true} to instruct @value{GDBN} to completely canonicalize each
21730 pair of file names it needs to compare. This will make file-name
21731 comparisons accurate, but at a price of a significant slowdown.
21734 @item set basenames-may-differ
21735 @kindex set basenames-may-differ
21736 Set whether a source file may have multiple base names.
21738 @item show basenames-may-differ
21739 @kindex show basenames-may-differ
21740 Show whether a source file may have multiple base names.
21744 @section File Caching
21745 @cindex caching of opened files
21746 @cindex caching of bfd objects
21748 To speed up file loading, and reduce memory usage, @value{GDBN} will
21749 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21750 BFD, bfd, The Binary File Descriptor Library}. The following commands
21751 allow visibility and control of the caching behavior.
21754 @kindex maint info bfds
21755 @item maint info bfds
21756 This prints information about each @code{bfd} object that is known to
21759 @kindex maint set bfd-sharing
21760 @kindex maint show bfd-sharing
21761 @kindex bfd caching
21762 @item maint set bfd-sharing
21763 @item maint show bfd-sharing
21764 Control whether @code{bfd} objects can be shared. When sharing is
21765 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21766 than reopening the same file. Turning sharing off does not cause
21767 already shared @code{bfd} objects to be unshared, but all future files
21768 that are opened will create a new @code{bfd} object. Similarly,
21769 re-enabling sharing does not cause multiple existing @code{bfd}
21770 objects to be collapsed into a single shared @code{bfd} object.
21772 @kindex set debug bfd-cache @var{level}
21773 @kindex bfd caching
21774 @item set debug bfd-cache @var{level}
21775 Turns on debugging of the bfd cache, setting the level to @var{level}.
21777 @kindex show debug bfd-cache
21778 @kindex bfd caching
21779 @item show debug bfd-cache
21780 Show the current debugging level of the bfd cache.
21783 @node Separate Debug Files
21784 @section Debugging Information in Separate Files
21785 @cindex separate debugging information files
21786 @cindex debugging information in separate files
21787 @cindex @file{.debug} subdirectories
21788 @cindex debugging information directory, global
21789 @cindex global debugging information directories
21790 @cindex build ID, and separate debugging files
21791 @cindex @file{.build-id} directory
21793 @value{GDBN} allows you to put a program's debugging information in a
21794 file separate from the executable itself, in a way that allows
21795 @value{GDBN} to find and load the debugging information automatically.
21796 Since debugging information can be very large---sometimes larger
21797 than the executable code itself---some systems distribute debugging
21798 information for their executables in separate files, which users can
21799 install only when they need to debug a problem.
21801 @value{GDBN} supports two ways of specifying the separate debug info
21806 The executable contains a @dfn{debug link} that specifies the name of
21807 the separate debug info file. The separate debug file's name is
21808 usually @file{@var{executable}.debug}, where @var{executable} is the
21809 name of the corresponding executable file without leading directories
21810 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21811 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21812 checksum for the debug file, which @value{GDBN} uses to validate that
21813 the executable and the debug file came from the same build.
21817 The executable contains a @dfn{build ID}, a unique bit string that is
21818 also present in the corresponding debug info file. (This is supported
21819 only on some operating systems, when using the ELF or PE file formats
21820 for binary files and the @sc{gnu} Binutils.) For more details about
21821 this feature, see the description of the @option{--build-id}
21822 command-line option in @ref{Options, , Command Line Options, ld,
21823 The GNU Linker}. The debug info file's name is not specified
21824 explicitly by the build ID, but can be computed from the build ID, see
21828 Depending on the way the debug info file is specified, @value{GDBN}
21829 uses two different methods of looking for the debug file:
21833 For the ``debug link'' method, @value{GDBN} looks up the named file in
21834 the directory of the executable file, then in a subdirectory of that
21835 directory named @file{.debug}, and finally under each one of the
21836 global debug directories, in a subdirectory whose name is identical to
21837 the leading directories of the executable's absolute file name. (On
21838 MS-Windows/MS-DOS, the drive letter of the executable's leading
21839 directories is converted to a one-letter subdirectory, i.e.@:
21840 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21841 filesystems disallow colons in file names.)
21844 For the ``build ID'' method, @value{GDBN} looks in the
21845 @file{.build-id} subdirectory of each one of the global debug directories for
21846 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21847 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21848 are the rest of the bit string. (Real build ID strings are 32 or more
21849 hex characters, not 10.) @value{GDBN} can automatically query
21850 @code{debuginfod} servers using build IDs in order to download separate debug
21851 files that cannot be found locally. For more information see @ref{Debuginfod}.
21854 So, for example, suppose you ask @value{GDBN} to debug
21855 @file{/usr/bin/ls}, which has a debug link that specifies the
21856 file @file{ls.debug}, and a build ID whose value in hex is
21857 @code{abcdef1234}. If the list of the global debug directories includes
21858 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21859 debug information files, in the indicated order:
21863 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21865 @file{/usr/bin/ls.debug}
21867 @file{/usr/bin/.debug/ls.debug}
21869 @file{/usr/lib/debug/usr/bin/ls.debug}.
21872 If the debug file still has not been found and @code{debuginfod}
21873 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21874 file from @code{debuginfod} servers.
21876 @anchor{debug-file-directory}
21877 Global debugging info directories default to what is set by @value{GDBN}
21878 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21879 you can also set the global debugging info directories, and view the list
21880 @value{GDBN} is currently using.
21884 @kindex set debug-file-directory
21885 @item set debug-file-directory @var{directories}
21886 Set the directories which @value{GDBN} searches for separate debugging
21887 information files to @var{directory}. Multiple path components can be set
21888 concatenating them by a path separator.
21890 @kindex show debug-file-directory
21891 @item show debug-file-directory
21892 Show the directories @value{GDBN} searches for separate debugging
21897 @cindex @code{.gnu_debuglink} sections
21898 @cindex debug link sections
21899 A debug link is a special section of the executable file named
21900 @code{.gnu_debuglink}. The section must contain:
21904 A filename, with any leading directory components removed, followed by
21907 zero to three bytes of padding, as needed to reach the next four-byte
21908 boundary within the section, and
21910 a four-byte CRC checksum, stored in the same endianness used for the
21911 executable file itself. The checksum is computed on the debugging
21912 information file's full contents by the function given below, passing
21913 zero as the @var{crc} argument.
21916 Any executable file format can carry a debug link, as long as it can
21917 contain a section named @code{.gnu_debuglink} with the contents
21920 @cindex @code{.note.gnu.build-id} sections
21921 @cindex build ID sections
21922 The build ID is a special section in the executable file (and in other
21923 ELF binary files that @value{GDBN} may consider). This section is
21924 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21925 It contains unique identification for the built files---the ID remains
21926 the same across multiple builds of the same build tree. The default
21927 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21928 content for the build ID string. The same section with an identical
21929 value is present in the original built binary with symbols, in its
21930 stripped variant, and in the separate debugging information file.
21932 The debugging information file itself should be an ordinary
21933 executable, containing a full set of linker symbols, sections, and
21934 debugging information. The sections of the debugging information file
21935 should have the same names, addresses, and sizes as the original file,
21936 but they need not contain any data---much like a @code{.bss} section
21937 in an ordinary executable.
21939 The @sc{gnu} binary utilities (Binutils) package includes the
21940 @samp{objcopy} utility that can produce
21941 the separated executable / debugging information file pairs using the
21942 following commands:
21945 @kbd{objcopy --only-keep-debug foo foo.debug}
21950 These commands remove the debugging
21951 information from the executable file @file{foo} and place it in the file
21952 @file{foo.debug}. You can use the first, second or both methods to link the
21957 The debug link method needs the following additional command to also leave
21958 behind a debug link in @file{foo}:
21961 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21964 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21965 a version of the @code{strip} command such that the command @kbd{strip foo -f
21966 foo.debug} has the same functionality as the two @code{objcopy} commands and
21967 the @code{ln -s} command above, together.
21970 Build ID gets embedded into the main executable using @code{ld --build-id} or
21971 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21972 compatibility fixes for debug files separation are present in @sc{gnu} binary
21973 utilities (Binutils) package since version 2.18.
21978 @cindex CRC algorithm definition
21979 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21980 IEEE 802.3 using the polynomial:
21982 @c TexInfo requires naked braces for multi-digit exponents for Tex
21983 @c output, but this causes HTML output to barf. HTML has to be set using
21984 @c raw commands. So we end up having to specify this equation in 2
21989 <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>
21990 + <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
21996 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21997 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
22001 The function is computed byte at a time, taking the least
22002 significant bit of each byte first. The initial pattern
22003 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
22004 the final result is inverted to ensure trailing zeros also affect the
22007 @emph{Note:} This is the same CRC polynomial as used in handling the
22008 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
22009 However in the case of the Remote Serial Protocol, the CRC is computed
22010 @emph{most} significant bit first, and the result is not inverted, so
22011 trailing zeros have no effect on the CRC value.
22013 To complete the description, we show below the code of the function
22014 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22015 initially supplied @code{crc} argument means that an initial call to
22016 this function passing in zero will start computing the CRC using
22019 @kindex gnu_debuglink_crc32
22022 gnu_debuglink_crc32 (unsigned long crc,
22023 unsigned char *buf, size_t len)
22025 static const unsigned long crc32_table[256] =
22027 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22028 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22029 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22030 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22031 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22032 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22033 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22034 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22035 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22036 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22037 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22038 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22039 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22040 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22041 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22042 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22043 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22044 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22045 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22046 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22047 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22048 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22049 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22050 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22051 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22052 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22053 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22054 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22055 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22056 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22057 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22058 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22059 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22060 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22061 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22062 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22063 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22064 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22065 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22066 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22067 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22068 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22069 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22070 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22071 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22072 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22073 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22074 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22075 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22076 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22077 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22080 unsigned char *end;
22082 crc = ~crc & 0xffffffff;
22083 for (end = buf + len; buf < end; ++buf)
22084 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22085 return ~crc & 0xffffffff;
22090 This computation does not apply to the ``build ID'' method.
22092 @node MiniDebugInfo
22093 @section Debugging information in a special section
22094 @cindex separate debug sections
22095 @cindex @samp{.gnu_debugdata} section
22097 Some systems ship pre-built executables and libraries that have a
22098 special @samp{.gnu_debugdata} section. This feature is called
22099 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22100 is used to supply extra symbols for backtraces.
22102 The intent of this section is to provide extra minimal debugging
22103 information for use in simple backtraces. It is not intended to be a
22104 replacement for full separate debugging information (@pxref{Separate
22105 Debug Files}). The example below shows the intended use; however,
22106 @value{GDBN} does not currently put restrictions on what sort of
22107 debugging information might be included in the section.
22109 @value{GDBN} has support for this extension. If the section exists,
22110 then it is used provided that no other source of debugging information
22111 can be found, and that @value{GDBN} was configured with LZMA support.
22113 This section can be easily created using @command{objcopy} and other
22114 standard utilities:
22117 # Extract the dynamic symbols from the main binary, there is no need
22118 # to also have these in the normal symbol table.
22119 nm -D @var{binary} --format=posix --defined-only \
22120 | awk '@{ print $1 @}' | sort > dynsyms
22122 # Extract all the text (i.e. function) symbols from the debuginfo.
22123 # (Note that we actually also accept "D" symbols, for the benefit
22124 # of platforms like PowerPC64 that use function descriptors.)
22125 nm @var{binary} --format=posix --defined-only \
22126 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22129 # Keep all the function symbols not already in the dynamic symbol
22131 comm -13 dynsyms funcsyms > keep_symbols
22133 # Separate full debug info into debug binary.
22134 objcopy --only-keep-debug @var{binary} debug
22136 # Copy the full debuginfo, keeping only a minimal set of symbols and
22137 # removing some unnecessary sections.
22138 objcopy -S --remove-section .gdb_index --remove-section .comment \
22139 --keep-symbols=keep_symbols debug mini_debuginfo
22141 # Drop the full debug info from the original binary.
22142 strip --strip-all -R .comment @var{binary}
22144 # Inject the compressed data into the .gnu_debugdata section of the
22147 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22151 @section Index Files Speed Up @value{GDBN}
22152 @cindex index files
22153 @cindex @samp{.gdb_index} section
22155 When @value{GDBN} finds a symbol file, it scans the symbols in the
22156 file in order to construct an internal symbol table. This lets most
22157 @value{GDBN} operations work quickly---at the cost of a delay early
22158 on. For large programs, this delay can be quite lengthy, so
22159 @value{GDBN} provides a way to build an index, which speeds up
22162 For convenience, @value{GDBN} comes with a program,
22163 @command{gdb-add-index}, which can be used to add the index to a
22164 symbol file. It takes the symbol file as its only argument:
22167 $ gdb-add-index symfile
22170 @xref{gdb-add-index}.
22172 It is also possible to do the work manually. Here is what
22173 @command{gdb-add-index} does behind the curtains.
22175 The index is stored as a section in the symbol file. @value{GDBN} can
22176 write the index to a file, then you can put it into the symbol file
22177 using @command{objcopy}.
22179 To create an index file, use the @code{save gdb-index} command:
22182 @item save gdb-index [-dwarf-5] @var{directory}
22183 @kindex save gdb-index
22184 Create index files for all symbol files currently known by
22185 @value{GDBN}. For each known @var{symbol-file}, this command by
22186 default creates it produces a single file
22187 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22188 the @option{-dwarf-5} option, it produces 2 files:
22189 @file{@var{symbol-file}.debug_names} and
22190 @file{@var{symbol-file}.debug_str}. The files are created in the
22191 given @var{directory}.
22194 Once you have created an index file you can merge it into your symbol
22195 file, here named @file{symfile}, using @command{objcopy}:
22198 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22199 --set-section-flags .gdb_index=readonly symfile symfile
22202 Or for @code{-dwarf-5}:
22205 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22206 $ cat symfile.debug_str >>symfile.debug_str.new
22207 $ objcopy --add-section .debug_names=symfile.gdb-index \
22208 --set-section-flags .debug_names=readonly \
22209 --update-section .debug_str=symfile.debug_str.new symfile symfile
22212 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22213 sections that have been deprecated. Usually they are deprecated because
22214 they are missing a new feature or have performance issues.
22215 To tell @value{GDBN} to use a deprecated index section anyway
22216 specify @code{set use-deprecated-index-sections on}.
22217 The default is @code{off}.
22218 This can speed up startup, but may result in some functionality being lost.
22219 @xref{Index Section Format}.
22221 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22222 must be done before gdb reads the file. The following will not work:
22225 $ gdb -ex "set use-deprecated-index-sections on" <program>
22228 Instead you must do, for example,
22231 $ gdb -iex "set use-deprecated-index-sections on" <program>
22234 Indices only work when using DWARF debugging information, not stabs.
22236 @subsection Automatic symbol index cache
22238 @cindex automatic symbol index cache
22239 It is possible for @value{GDBN} to automatically save a copy of this index in a
22240 cache on disk and retrieve it from there when loading the same binary in the
22241 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22242 The following commands can be used to tweak the behavior of the index cache.
22246 @kindex set index-cache
22247 @item set index-cache enabled on
22248 @itemx set index-cache enabled off
22249 Enable or disable the use of the symbol index cache.
22251 @item set index-cache directory @var{directory}
22252 @kindex show index-cache
22253 @itemx show index-cache directory
22254 Set/show the directory where index files will be saved.
22256 The default value for this directory depends on the host platform. On
22257 most systems, the index is cached in the @file{gdb} subdirectory of
22258 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22259 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22260 of your home directory. However, on some systems, the default may
22261 differ according to local convention.
22263 There is no limit on the disk space used by index cache. It is perfectly safe
22264 to delete the content of that directory to free up disk space.
22266 @item show index-cache stats
22267 Print the number of cache hits and misses since the launch of @value{GDBN}.
22271 @node Symbol Errors
22272 @section Errors Reading Symbol Files
22274 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22275 such as symbol types it does not recognize, or known bugs in compiler
22276 output. By default, @value{GDBN} does not notify you of such problems, since
22277 they are relatively common and primarily of interest to people
22278 debugging compilers. If you are interested in seeing information
22279 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22280 only one message about each such type of problem, no matter how many
22281 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22282 to see how many times the problems occur, with the @code{set
22283 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22286 The messages currently printed, and their meanings, include:
22289 @item inner block not inside outer block in @var{symbol}
22291 The symbol information shows where symbol scopes begin and end
22292 (such as at the start of a function or a block of statements). This
22293 error indicates that an inner scope block is not fully contained
22294 in its outer scope blocks.
22296 @value{GDBN} circumvents the problem by treating the inner block as if it had
22297 the same scope as the outer block. In the error message, @var{symbol}
22298 may be shown as ``@code{(don't know)}'' if the outer block is not a
22301 @item block at @var{address} out of order
22303 The symbol information for symbol scope blocks should occur in
22304 order of increasing addresses. This error indicates that it does not
22307 @value{GDBN} does not circumvent this problem, and has trouble
22308 locating symbols in the source file whose symbols it is reading. (You
22309 can often determine what source file is affected by specifying
22310 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22313 @item bad block start address patched
22315 The symbol information for a symbol scope block has a start address
22316 smaller than the address of the preceding source line. This is known
22317 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22319 @value{GDBN} circumvents the problem by treating the symbol scope block as
22320 starting on the previous source line.
22322 @item bad string table offset in symbol @var{n}
22325 Symbol number @var{n} contains a pointer into the string table which is
22326 larger than the size of the string table.
22328 @value{GDBN} circumvents the problem by considering the symbol to have the
22329 name @code{foo}, which may cause other problems if many symbols end up
22332 @item unknown symbol type @code{0x@var{nn}}
22334 The symbol information contains new data types that @value{GDBN} does
22335 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22336 uncomprehended information, in hexadecimal.
22338 @value{GDBN} circumvents the error by ignoring this symbol information.
22339 This usually allows you to debug your program, though certain symbols
22340 are not accessible. If you encounter such a problem and feel like
22341 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22342 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22343 and examine @code{*bufp} to see the symbol.
22345 @item stub type has NULL name
22347 @value{GDBN} could not find the full definition for a struct or class.
22349 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22350 The symbol information for a C@t{++} member function is missing some
22351 information that recent versions of the compiler should have output for
22354 @item info mismatch between compiler and debugger
22356 @value{GDBN} could not parse a type specification output by the compiler.
22361 @section GDB Data Files
22363 @cindex prefix for data files
22364 @value{GDBN} will sometimes read an auxiliary data file. These files
22365 are kept in a directory known as the @dfn{data directory}.
22367 You can set the data directory's name, and view the name @value{GDBN}
22368 is currently using.
22371 @kindex set data-directory
22372 @item set data-directory @var{directory}
22373 Set the directory which @value{GDBN} searches for auxiliary data files
22374 to @var{directory}.
22376 @kindex show data-directory
22377 @item show data-directory
22378 Show the directory @value{GDBN} searches for auxiliary data files.
22381 @cindex default data directory
22382 @cindex @samp{--with-gdb-datadir}
22383 You can set the default data directory by using the configure-time
22384 @samp{--with-gdb-datadir} option. If the data directory is inside
22385 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22386 @samp{--exec-prefix}), then the default data directory will be updated
22387 automatically if the installed @value{GDBN} is moved to a new
22390 The data directory may also be specified with the
22391 @code{--data-directory} command line option.
22392 @xref{Mode Options}.
22395 @chapter Specifying a Debugging Target
22397 @cindex debugging target
22398 A @dfn{target} is the execution environment occupied by your program.
22400 Often, @value{GDBN} runs in the same host environment as your program;
22401 in that case, the debugging target is specified as a side effect when
22402 you use the @code{file} or @code{core} commands. When you need more
22403 flexibility---for example, running @value{GDBN} on a physically separate
22404 host, or controlling a standalone system over a serial port or a
22405 realtime system over a TCP/IP connection---you can use the @code{target}
22406 command to specify one of the target types configured for @value{GDBN}
22407 (@pxref{Target Commands, ,Commands for Managing Targets}).
22409 @cindex target architecture
22410 It is possible to build @value{GDBN} for several different @dfn{target
22411 architectures}. When @value{GDBN} is built like that, you can choose
22412 one of the available architectures with the @kbd{set architecture}
22416 @kindex set architecture
22417 @kindex show architecture
22418 @item set architecture @var{arch}
22419 This command sets the current target architecture to @var{arch}. The
22420 value of @var{arch} can be @code{"auto"}, in addition to one of the
22421 supported architectures.
22423 @item show architecture
22424 Show the current target architecture.
22426 @item set processor
22428 @kindex set processor
22429 @kindex show processor
22430 These are alias commands for, respectively, @code{set architecture}
22431 and @code{show architecture}.
22435 * Active Targets:: Active targets
22436 * Target Commands:: Commands for managing targets
22437 * Byte Order:: Choosing target byte order
22440 @node Active Targets
22441 @section Active Targets
22443 @cindex stacking targets
22444 @cindex active targets
22445 @cindex multiple targets
22447 There are multiple classes of targets such as: processes, executable files or
22448 recording sessions. Core files belong to the process class, making core file
22449 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22450 on multiple active targets, one in each class. This allows you to (for
22451 example) start a process and inspect its activity, while still having access to
22452 the executable file after the process finishes. Or if you start process
22453 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22454 presented a virtual layer of the recording target, while the process target
22455 remains stopped at the chronologically last point of the process execution.
22457 Use the @code{core-file} and @code{exec-file} commands to select a new core
22458 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22459 specify as a target a process that is already running, use the @code{attach}
22460 command (@pxref{Attach, ,Debugging an Already-running Process}).
22462 @node Target Commands
22463 @section Commands for Managing Targets
22466 @item target @var{type} @var{parameters}
22467 Connects the @value{GDBN} host environment to a target machine or
22468 process. A target is typically a protocol for talking to debugging
22469 facilities. You use the argument @var{type} to specify the type or
22470 protocol of the target machine.
22472 Further @var{parameters} are interpreted by the target protocol, but
22473 typically include things like device names or host names to connect
22474 with, process numbers, and baud rates.
22476 The @code{target} command does not repeat if you press @key{RET} again
22477 after executing the command.
22479 @kindex help target
22481 Displays the names of all targets available. To display targets
22482 currently selected, use either @code{info target} or @code{info files}
22483 (@pxref{Files, ,Commands to Specify Files}).
22485 @item help target @var{name}
22486 Describe a particular target, including any parameters necessary to
22489 @kindex set gnutarget
22490 @item set gnutarget @var{args}
22491 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22492 knows whether it is reading an @dfn{executable},
22493 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22494 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22495 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22498 @emph{Warning:} To specify a file format with @code{set gnutarget},
22499 you must know the actual BFD name.
22503 @xref{Files, , Commands to Specify Files}.
22505 @kindex show gnutarget
22506 @item show gnutarget
22507 Use the @code{show gnutarget} command to display what file format
22508 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22509 @value{GDBN} will determine the file format for each file automatically,
22510 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22513 @cindex common targets
22514 Here are some common targets (available, or not, depending on the GDB
22519 @item target exec @var{program}
22520 @cindex executable file target
22521 An executable file. @samp{target exec @var{program}} is the same as
22522 @samp{exec-file @var{program}}.
22524 @item target core @var{filename}
22525 @cindex core dump file target
22526 A core dump file. @samp{target core @var{filename}} is the same as
22527 @samp{core-file @var{filename}}.
22529 @item target remote @var{medium}
22530 @cindex remote target
22531 A remote system connected to @value{GDBN} via a serial line or network
22532 connection. This command tells @value{GDBN} to use its own remote
22533 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22535 For example, if you have a board connected to @file{/dev/ttya} on the
22536 machine running @value{GDBN}, you could say:
22539 target remote /dev/ttya
22542 @code{target remote} supports the @code{load} command. This is only
22543 useful if you have some other way of getting the stub to the target
22544 system, and you can put it somewhere in memory where it won't get
22545 clobbered by the download.
22547 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22548 @cindex built-in simulator target
22549 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22557 works; however, you cannot assume that a specific memory map, device
22558 drivers, or even basic I/O is available, although some simulators do
22559 provide these. For info about any processor-specific simulator details,
22560 see the appropriate section in @ref{Embedded Processors, ,Embedded
22563 @item target native
22564 @cindex native target
22565 Setup for local/native process debugging. Useful to make the
22566 @code{run} command spawn native processes (likewise @code{attach},
22567 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22568 (@pxref{set auto-connect-native-target}).
22572 Different targets are available on different configurations of @value{GDBN};
22573 your configuration may have more or fewer targets.
22575 Many remote targets require you to download the executable's code once
22576 you've successfully established a connection. You may wish to control
22577 various aspects of this process.
22582 @kindex set hash@r{, for remote monitors}
22583 @cindex hash mark while downloading
22584 This command controls whether a hash mark @samp{#} is displayed while
22585 downloading a file to the remote monitor. If on, a hash mark is
22586 displayed after each S-record is successfully downloaded to the
22590 @kindex show hash@r{, for remote monitors}
22591 Show the current status of displaying the hash mark.
22593 @item set debug monitor
22594 @kindex set debug monitor
22595 @cindex display remote monitor communications
22596 Enable or disable display of communications messages between
22597 @value{GDBN} and the remote monitor.
22599 @item show debug monitor
22600 @kindex show debug monitor
22601 Show the current status of displaying communications between
22602 @value{GDBN} and the remote monitor.
22607 @kindex load @var{filename} @var{offset}
22608 @item load @var{filename} @var{offset}
22610 Depending on what remote debugging facilities are configured into
22611 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22612 is meant to make @var{filename} (an executable) available for debugging
22613 on the remote system---by downloading, or dynamic linking, for example.
22614 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22615 the @code{add-symbol-file} command.
22617 If your @value{GDBN} does not have a @code{load} command, attempting to
22618 execute it gets the error message ``@code{You can't do that when your
22619 target is @dots{}}''
22621 The file is loaded at whatever address is specified in the executable.
22622 For some object file formats, you can specify the load address when you
22623 link the program; for other formats, like a.out, the object file format
22624 specifies a fixed address.
22625 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22627 It is also possible to tell @value{GDBN} to load the executable file at a
22628 specific offset described by the optional argument @var{offset}. When
22629 @var{offset} is provided, @var{filename} must also be provided.
22631 Depending on the remote side capabilities, @value{GDBN} may be able to
22632 load programs into flash memory.
22634 @code{load} does not repeat if you press @key{RET} again after using it.
22639 @kindex flash-erase
22641 @anchor{flash-erase}
22643 Erases all known flash memory regions on the target.
22648 @section Choosing Target Byte Order
22650 @cindex choosing target byte order
22651 @cindex target byte order
22653 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22654 offer the ability to run either big-endian or little-endian byte
22655 orders. Usually the executable or symbol will include a bit to
22656 designate the endian-ness, and you will not need to worry about
22657 which to use. However, you may still find it useful to adjust
22658 @value{GDBN}'s idea of processor endian-ness manually.
22662 @item set endian big
22663 Instruct @value{GDBN} to assume the target is big-endian.
22665 @item set endian little
22666 Instruct @value{GDBN} to assume the target is little-endian.
22668 @item set endian auto
22669 Instruct @value{GDBN} to use the byte order associated with the
22673 Display @value{GDBN}'s current idea of the target byte order.
22677 If the @code{set endian auto} mode is in effect and no executable has
22678 been selected, then the endianness used is the last one chosen either
22679 by one of the @code{set endian big} and @code{set endian little}
22680 commands or by inferring from the last executable used. If no
22681 endianness has been previously chosen, then the default for this mode
22682 is inferred from the target @value{GDBN} has been built for, and is
22683 @code{little} if the name of the target CPU has an @code{el} suffix
22684 and @code{big} otherwise.
22686 Note that these commands merely adjust interpretation of symbolic
22687 data on the host, and that they have absolutely no effect on the
22691 @node Remote Debugging
22692 @chapter Debugging Remote Programs
22693 @cindex remote debugging
22695 If you are trying to debug a program running on a machine that cannot run
22696 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22697 For example, you might use remote debugging on an operating system kernel,
22698 or on a small system which does not have a general purpose operating system
22699 powerful enough to run a full-featured debugger.
22701 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22702 to make this work with particular debugging targets. In addition,
22703 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22704 but not specific to any particular target system) which you can use if you
22705 write the remote stubs---the code that runs on the remote system to
22706 communicate with @value{GDBN}.
22708 Other remote targets may be available in your
22709 configuration of @value{GDBN}; use @code{help target} to list them.
22712 * Connecting:: Connecting to a remote target
22713 * File Transfer:: Sending files to a remote system
22714 * Server:: Using the gdbserver program
22715 * Remote Configuration:: Remote configuration
22716 * Remote Stub:: Implementing a remote stub
22720 @section Connecting to a Remote Target
22721 @cindex remote debugging, connecting
22722 @cindex @code{gdbserver}, connecting
22723 @cindex remote debugging, types of connections
22724 @cindex @code{gdbserver}, types of connections
22725 @cindex @code{gdbserver}, @code{target remote} mode
22726 @cindex @code{gdbserver}, @code{target extended-remote} mode
22728 This section describes how to connect to a remote target, including the
22729 types of connections and their differences, how to set up executable and
22730 symbol files on the host and target, and the commands used for
22731 connecting to and disconnecting from the remote target.
22733 @subsection Types of Remote Connections
22735 @value{GDBN} supports two types of remote connections, @code{target remote}
22736 mode and @code{target extended-remote} mode. Note that many remote targets
22737 support only @code{target remote} mode. There are several major
22738 differences between the two types of connections, enumerated here:
22742 @cindex remote debugging, detach and program exit
22743 @item Result of detach or program exit
22744 @strong{With target remote mode:} When the debugged program exits or you
22745 detach from it, @value{GDBN} disconnects from the target. When using
22746 @code{gdbserver}, @code{gdbserver} will exit.
22748 @strong{With target extended-remote mode:} When the debugged program exits or
22749 you detach from it, @value{GDBN} remains connected to the target, even
22750 though no program is running. You can rerun the program, attach to a
22751 running program, or use @code{monitor} commands specific to the target.
22753 When using @code{gdbserver} in this case, it does not exit unless it was
22754 invoked using the @option{--once} option. If the @option{--once} option
22755 was not used, you can ask @code{gdbserver} to exit using the
22756 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22758 @item Specifying the program to debug
22759 For both connection types you use the @code{file} command to specify the
22760 program on the host system. If you are using @code{gdbserver} there are
22761 some differences in how to specify the location of the program on the
22764 @strong{With target remote mode:} You must either specify the program to debug
22765 on the @code{gdbserver} command line or use the @option{--attach} option
22766 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22768 @cindex @option{--multi}, @code{gdbserver} option
22769 @strong{With target extended-remote mode:} You may specify the program to debug
22770 on the @code{gdbserver} command line, or you can load the program or attach
22771 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22773 @anchor{--multi Option in Types of Remote Connnections}
22774 You can start @code{gdbserver} without supplying an initial command to run
22775 or process ID to attach. To do this, use the @option{--multi} command line
22776 option. Then you can connect using @code{target extended-remote} and start
22777 the program you want to debug (see below for details on using the
22778 @code{run} command in this scenario). Note that the conditions under which
22779 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22780 (@code{target remote} or @code{target extended-remote}). The
22781 @option{--multi} option to @code{gdbserver} has no influence on that.
22783 @item The @code{run} command
22784 @strong{With target remote mode:} The @code{run} command is not
22785 supported. Once a connection has been established, you can use all
22786 the usual @value{GDBN} commands to examine and change data. The
22787 remote program is already running, so you can use commands like
22788 @kbd{step} and @kbd{continue}.
22790 @strong{With target extended-remote mode:} The @code{run} command is
22791 supported. The @code{run} command uses the value set by
22792 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22793 the program to run. Command line arguments are supported, except for
22794 wildcard expansion and I/O redirection (@pxref{Arguments}).
22796 If you specify the program to debug on the command line, then the
22797 @code{run} command is not required to start execution, and you can
22798 resume using commands like @kbd{step} and @kbd{continue} as with
22799 @code{target remote} mode.
22801 @anchor{Attaching in Types of Remote Connections}
22803 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22804 not supported. To attach to a running program using @code{gdbserver}, you
22805 must use the @option{--attach} option (@pxref{Running gdbserver}).
22807 @strong{With target extended-remote mode:} To attach to a running program,
22808 you may use the @code{attach} command after the connection has been
22809 established. If you are using @code{gdbserver}, you may also invoke
22810 @code{gdbserver} using the @option{--attach} option
22811 (@pxref{Running gdbserver}).
22813 Some remote targets allow @value{GDBN} to determine the executable file running
22814 in the process the debugger is attaching to. In such a case, @value{GDBN}
22815 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22816 between the executable file name running in the process and the name of the
22817 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22821 @anchor{Host and target files}
22822 @subsection Host and Target Files
22823 @cindex remote debugging, symbol files
22824 @cindex symbol files, remote debugging
22826 @value{GDBN}, running on the host, needs access to symbol and debugging
22827 information for your program running on the target. This requires
22828 access to an unstripped copy of your program, and possibly any associated
22829 symbol files. Note that this section applies equally to both @code{target
22830 remote} mode and @code{target extended-remote} mode.
22832 Some remote targets (@pxref{qXfer executable filename read}, and
22833 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22834 the same connection used to communicate with @value{GDBN}. With such a
22835 target, if the remote program is unstripped, the only command you need is
22836 @code{target remote} (or @code{target extended-remote}).
22838 If the remote program is stripped, or the target does not support remote
22839 program file access, start up @value{GDBN} using the name of the local
22840 unstripped copy of your program as the first argument, or use the
22841 @code{file} command. Use @code{set sysroot} to specify the location (on
22842 the host) of target libraries (unless your @value{GDBN} was compiled with
22843 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22844 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22847 The symbol file and target libraries must exactly match the executable
22848 and libraries on the target, with one exception: the files on the host
22849 system should not be stripped, even if the files on the target system
22850 are. Mismatched or missing files will lead to confusing results
22851 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22852 files may also prevent @code{gdbserver} from debugging multi-threaded
22855 @subsection Remote Connection Commands
22856 @cindex remote connection commands
22857 @value{GDBN} can communicate with the target over a serial line, a
22858 local Unix domain socket, or
22859 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22860 each case, @value{GDBN} uses the same protocol for debugging your
22861 program; only the medium carrying the debugging packets varies. The
22862 @code{target remote} and @code{target extended-remote} commands
22863 establish a connection to the target. Both commands accept the same
22864 arguments, which indicate the medium to use:
22868 @item target remote @var{serial-device}
22869 @itemx target extended-remote @var{serial-device}
22870 @cindex serial line, @code{target remote}
22871 Use @var{serial-device} to communicate with the target. For example,
22872 to use a serial line connected to the device named @file{/dev/ttyb}:
22875 target remote /dev/ttyb
22878 If you're using a serial line, you may want to give @value{GDBN} the
22879 @samp{--baud} option, or use the @code{set serial baud} command
22880 (@pxref{Remote Configuration, set serial baud}) before the
22881 @code{target} command.
22883 @item target remote @var{local-socket}
22884 @itemx target extended-remote @var{local-socket}
22885 @cindex local socket, @code{target remote}
22886 @cindex Unix domain socket
22887 Use @var{local-socket} to communicate with the target. For example,
22888 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22891 target remote /tmp/gdb-socket0
22894 Note that this command has the same form as the command to connect
22895 to a serial line. @value{GDBN} will automatically determine which
22896 kind of file you have specified and will make the appropriate kind
22898 This feature is not available if the host system does not support
22899 Unix domain sockets.
22901 @item target remote @code{@var{host}:@var{port}}
22902 @itemx target remote @code{[@var{host}]:@var{port}}
22903 @itemx target remote @code{tcp:@var{host}:@var{port}}
22904 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22905 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22906 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22907 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22908 @itemx target extended-remote @code{@var{host}:@var{port}}
22909 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22910 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22911 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22912 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22913 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22914 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22915 @cindex @acronym{TCP} port, @code{target remote}
22916 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22917 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22918 address, or a numeric @acronym{IPv6} address (with or without the
22919 square brackets to separate the address from the port); @var{port}
22920 must be a decimal number. The @var{host} could be the target machine
22921 itself, if it is directly connected to the net, or it might be a
22922 terminal server which in turn has a serial line to the target.
22924 For example, to connect to port 2828 on a terminal server named
22928 target remote manyfarms:2828
22931 To connect to port 2828 on a terminal server whose address is
22932 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22933 square bracket syntax:
22936 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22940 or explicitly specify the @acronym{IPv6} protocol:
22943 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22946 This last example may be confusing to the reader, because there is no
22947 visible separation between the hostname and the port number.
22948 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22949 using square brackets for clarity. However, it is important to
22950 mention that for @value{GDBN} there is no ambiguity: the number after
22951 the last colon is considered to be the port number.
22953 If your remote target is actually running on the same machine as your
22954 debugger session (e.g.@: a simulator for your target running on the
22955 same host), you can omit the hostname. For example, to connect to
22956 port 1234 on your local machine:
22959 target remote :1234
22963 Note that the colon is still required here.
22965 @item target remote @code{udp:@var{host}:@var{port}}
22966 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22967 @itemx target remote @code{udp4:@var{host}:@var{port}}
22968 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22969 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22970 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22971 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22972 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22973 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22974 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22975 @cindex @acronym{UDP} port, @code{target remote}
22976 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22977 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22980 target remote udp:manyfarms:2828
22983 When using a @acronym{UDP} connection for remote debugging, you should
22984 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22985 can silently drop packets on busy or unreliable networks, which will
22986 cause havoc with your debugging session.
22988 @item target remote | @var{command}
22989 @itemx target extended-remote | @var{command}
22990 @cindex pipe, @code{target remote} to
22991 Run @var{command} in the background and communicate with it using a
22992 pipe. The @var{command} is a shell command, to be parsed and expanded
22993 by the system's command shell, @code{/bin/sh}; it should expect remote
22994 protocol packets on its standard input, and send replies on its
22995 standard output. You could use this to run a stand-alone simulator
22996 that speaks the remote debugging protocol, to make net connections
22997 using programs like @code{ssh}, or for other similar tricks.
22999 If @var{command} closes its standard output (perhaps by exiting),
23000 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
23001 program has already exited, this will have no effect.)
23005 @cindex interrupting remote programs
23006 @cindex remote programs, interrupting
23007 Whenever @value{GDBN} is waiting for the remote program, if you type the
23008 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
23009 program. This may or may not succeed, depending in part on the hardware
23010 and the serial drivers the remote system uses. If you type the
23011 interrupt character once again, @value{GDBN} displays this prompt:
23014 Interrupted while waiting for the program.
23015 Give up (and stop debugging it)? (y or n)
23018 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23019 the remote debugging session. (If you decide you want to try again later,
23020 you can use @kbd{target remote} again to connect once more.) If you type
23021 @kbd{n}, @value{GDBN} goes back to waiting.
23023 In @code{target extended-remote} mode, typing @kbd{n} will leave
23024 @value{GDBN} connected to the target.
23027 @kindex detach (remote)
23029 When you have finished debugging the remote program, you can use the
23030 @code{detach} command to release it from @value{GDBN} control.
23031 Detaching from the target normally resumes its execution, but the results
23032 will depend on your particular remote stub. After the @code{detach}
23033 command in @code{target remote} mode, @value{GDBN} is free to connect to
23034 another target. In @code{target extended-remote} mode, @value{GDBN} is
23035 still connected to the target.
23039 The @code{disconnect} command closes the connection to the target, and
23040 the target is generally not resumed. It will wait for @value{GDBN}
23041 (this instance or another one) to connect and continue debugging. After
23042 the @code{disconnect} command, @value{GDBN} is again free to connect to
23045 @cindex send command to remote monitor
23046 @cindex extend @value{GDBN} for remote targets
23047 @cindex add new commands for external monitor
23049 @item monitor @var{cmd}
23050 This command allows you to send arbitrary commands directly to the
23051 remote monitor. Since @value{GDBN} doesn't care about the commands it
23052 sends like this, this command is the way to extend @value{GDBN}---you
23053 can add new commands that only the external monitor will understand
23057 @node File Transfer
23058 @section Sending files to a remote system
23059 @cindex remote target, file transfer
23060 @cindex file transfer
23061 @cindex sending files to remote systems
23063 Some remote targets offer the ability to transfer files over the same
23064 connection used to communicate with @value{GDBN}. This is convenient
23065 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23066 running @code{gdbserver} over a network interface. For other targets,
23067 e.g.@: embedded devices with only a single serial port, this may be
23068 the only way to upload or download files.
23070 Not all remote targets support these commands.
23074 @item remote put @var{hostfile} @var{targetfile}
23075 Copy file @var{hostfile} from the host system (the machine running
23076 @value{GDBN}) to @var{targetfile} on the target system.
23079 @item remote get @var{targetfile} @var{hostfile}
23080 Copy file @var{targetfile} from the target system to @var{hostfile}
23081 on the host system.
23083 @kindex remote delete
23084 @item remote delete @var{targetfile}
23085 Delete @var{targetfile} from the target system.
23090 @section Using the @code{gdbserver} Program
23093 @cindex remote connection without stubs
23094 @code{gdbserver} is a control program for Unix-like systems, which
23095 allows you to connect your program with a remote @value{GDBN} via
23096 @code{target remote} or @code{target extended-remote}---but without
23097 linking in the usual debugging stub.
23099 @code{gdbserver} is not a complete replacement for the debugging stubs,
23100 because it requires essentially the same operating-system facilities
23101 that @value{GDBN} itself does. In fact, a system that can run
23102 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23103 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23104 because it is a much smaller program than @value{GDBN} itself. It is
23105 also easier to port than all of @value{GDBN}, so you may be able to get
23106 started more quickly on a new system by using @code{gdbserver}.
23107 Finally, if you develop code for real-time systems, you may find that
23108 the tradeoffs involved in real-time operation make it more convenient to
23109 do as much development work as possible on another system, for example
23110 by cross-compiling. You can use @code{gdbserver} to make a similar
23111 choice for debugging.
23113 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23114 or a TCP connection, using the standard @value{GDBN} remote serial
23118 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23119 Do not run @code{gdbserver} connected to any public network; a
23120 @value{GDBN} connection to @code{gdbserver} provides access to the
23121 target system with the same privileges as the user running
23125 @anchor{Running gdbserver}
23126 @subsection Running @code{gdbserver}
23127 @cindex arguments, to @code{gdbserver}
23128 @cindex @code{gdbserver}, command-line arguments
23130 Run @code{gdbserver} on the target system. You need a copy of the
23131 program you want to debug, including any libraries it requires.
23132 @code{gdbserver} does not need your program's symbol table, so you can
23133 strip the program if necessary to save space. @value{GDBN} on the host
23134 system does all the symbol handling.
23136 To use the server, you must tell it how to communicate with @value{GDBN};
23137 the name of your program; and the arguments for your program. The usual
23141 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23144 @var{comm} is either a device name (to use a serial line), or a TCP
23145 hostname and portnumber, or @code{-} or @code{stdio} to use
23146 stdin/stdout of @code{gdbserver}.
23147 For example, to debug Emacs with the argument
23148 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23152 target> gdbserver /dev/com1 emacs foo.txt
23155 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23158 To use a TCP connection instead of a serial line:
23161 target> gdbserver host:2345 emacs foo.txt
23164 The only difference from the previous example is the first argument,
23165 specifying that you are communicating with the host @value{GDBN} via
23166 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23167 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23168 (Currently, the @samp{host} part is ignored.) You can choose any number
23169 you want for the port number as long as it does not conflict with any
23170 TCP ports already in use on the target system (for example, @code{23} is
23171 reserved for @code{telnet}).@footnote{If you choose a port number that
23172 conflicts with another service, @code{gdbserver} prints an error message
23173 and exits.} You must use the same port number with the host @value{GDBN}
23174 @code{target remote} command.
23176 The @code{stdio} connection is useful when starting @code{gdbserver}
23180 (gdb) target remote | ssh -T hostname gdbserver - hello
23183 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23184 and we don't want escape-character handling. Ssh does this by default when
23185 a command is provided, the flag is provided to make it explicit.
23186 You could elide it if you want to.
23188 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23189 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23190 display through a pipe connected to gdbserver.
23191 Both @code{stdout} and @code{stderr} use the same pipe.
23193 @anchor{Attaching to a program}
23194 @subsubsection Attaching to a Running Program
23195 @cindex attach to a program, @code{gdbserver}
23196 @cindex @option{--attach}, @code{gdbserver} option
23198 On some targets, @code{gdbserver} can also attach to running programs.
23199 This is accomplished via the @code{--attach} argument. The syntax is:
23202 target> gdbserver --attach @var{comm} @var{pid}
23205 @var{pid} is the process ID of a currently running process. It isn't
23206 necessary to point @code{gdbserver} at a binary for the running process.
23208 In @code{target extended-remote} mode, you can also attach using the
23209 @value{GDBN} attach command
23210 (@pxref{Attaching in Types of Remote Connections}).
23213 You can debug processes by name instead of process ID if your target has the
23214 @code{pidof} utility:
23217 target> gdbserver --attach @var{comm} `pidof @var{program}`
23220 In case more than one copy of @var{program} is running, or @var{program}
23221 has multiple threads, most versions of @code{pidof} support the
23222 @code{-s} option to only return the first process ID.
23224 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23226 This section applies only when @code{gdbserver} is run to listen on a TCP
23229 @code{gdbserver} normally terminates after all of its debugged processes have
23230 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23231 extended-remote}, @code{gdbserver} stays running even with no processes left.
23232 @value{GDBN} normally terminates the spawned debugged process on its exit,
23233 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23234 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23235 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23236 stays running even in the @kbd{target remote} mode.
23238 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23239 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23240 completeness, at most one @value{GDBN} can be connected at a time.
23242 @cindex @option{--once}, @code{gdbserver} option
23243 By default, @code{gdbserver} keeps the listening TCP port open, so that
23244 subsequent connections are possible. However, if you start @code{gdbserver}
23245 with the @option{--once} option, it will stop listening for any further
23246 connection attempts after connecting to the first @value{GDBN} session. This
23247 means no further connections to @code{gdbserver} will be possible after the
23248 first one. It also means @code{gdbserver} will terminate after the first
23249 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23250 connections and even in the @kbd{target extended-remote} mode. The
23251 @option{--once} option allows reusing the same port number for connecting to
23252 multiple instances of @code{gdbserver} running on the same host, since each
23253 instance closes its port after the first connection.
23255 @anchor{Other Command-Line Arguments for gdbserver}
23256 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23258 You can use the @option{--multi} option to start @code{gdbserver} without
23259 specifying a program to debug or a process to attach to. Then you can
23260 attach in @code{target extended-remote} mode and run or attach to a
23261 program. For more information,
23262 @pxref{--multi Option in Types of Remote Connnections}.
23264 @cindex @option{--debug}, @code{gdbserver} option
23265 The @option{--debug} option tells @code{gdbserver} to display extra
23266 status information about the debugging process.
23267 @cindex @option{--remote-debug}, @code{gdbserver} option
23268 The @option{--remote-debug} option tells @code{gdbserver} to display
23269 remote protocol debug output.
23270 @cindex @option{--debug-file}, @code{gdbserver} option
23271 @cindex @code{gdbserver}, send all debug output to a single file
23272 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23273 write any debug output to the given @var{filename}. These options are intended
23274 for @code{gdbserver} development and for bug reports to the developers.
23276 @cindex @option{--debug-format}, @code{gdbserver} option
23277 The @option{--debug-format=option1[,option2,...]} option tells
23278 @code{gdbserver} to include additional information in each output.
23279 Possible options are:
23283 Turn off all extra information in debugging output.
23285 Turn on all extra information in debugging output.
23287 Include a timestamp in each line of debugging output.
23290 Options are processed in order. Thus, for example, if @option{none}
23291 appears last then no additional information is added to debugging output.
23293 @cindex @option{--wrapper}, @code{gdbserver} option
23294 The @option{--wrapper} option specifies a wrapper to launch programs
23295 for debugging. The option should be followed by the name of the
23296 wrapper, then any command-line arguments to pass to the wrapper, then
23297 @kbd{--} indicating the end of the wrapper arguments.
23299 @code{gdbserver} runs the specified wrapper program with a combined
23300 command line including the wrapper arguments, then the name of the
23301 program to debug, then any arguments to the program. The wrapper
23302 runs until it executes your program, and then @value{GDBN} gains control.
23304 You can use any program that eventually calls @code{execve} with
23305 its arguments as a wrapper. Several standard Unix utilities do
23306 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23307 with @code{exec "$@@"} will also work.
23309 For example, you can use @code{env} to pass an environment variable to
23310 the debugged program, without setting the variable in @code{gdbserver}'s
23314 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23317 @cindex @option{--selftest}
23318 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23321 $ gdbserver --selftest
23322 Ran 2 unit tests, 0 failed
23325 These tests are disabled in release.
23326 @subsection Connecting to @code{gdbserver}
23328 The basic procedure for connecting to the remote target is:
23332 Run @value{GDBN} on the host system.
23335 Make sure you have the necessary symbol files
23336 (@pxref{Host and target files}).
23337 Load symbols for your application using the @code{file} command before you
23338 connect. Use @code{set sysroot} to locate target libraries (unless your
23339 @value{GDBN} was compiled with the correct sysroot using
23340 @code{--with-sysroot}).
23343 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23344 For TCP connections, you must start up @code{gdbserver} prior to using
23345 the @code{target} command. Otherwise you may get an error whose
23346 text depends on the host system, but which usually looks something like
23347 @samp{Connection refused}. Don't use the @code{load}
23348 command in @value{GDBN} when using @code{target remote} mode, since the
23349 program is already on the target.
23353 @anchor{Monitor Commands for gdbserver}
23354 @subsection Monitor Commands for @code{gdbserver}
23355 @cindex monitor commands, for @code{gdbserver}
23357 During a @value{GDBN} session using @code{gdbserver}, you can use the
23358 @code{monitor} command to send special requests to @code{gdbserver}.
23359 Here are the available commands.
23363 List the available monitor commands.
23365 @item monitor set debug 0
23366 @itemx monitor set debug 1
23367 Disable or enable general debugging messages.
23369 @item monitor set remote-debug 0
23370 @itemx monitor set remote-debug 1
23371 Disable or enable specific debugging messages associated with the remote
23372 protocol (@pxref{Remote Protocol}).
23374 @item monitor set debug-file filename
23375 @itemx monitor set debug-file
23376 Send any debug output to the given file, or to stderr.
23378 @item monitor set debug-format option1@r{[},option2,...@r{]}
23379 Specify additional text to add to debugging messages.
23380 Possible options are:
23384 Turn off all extra information in debugging output.
23386 Turn on all extra information in debugging output.
23388 Include a timestamp in each line of debugging output.
23391 Options are processed in order. Thus, for example, if @option{none}
23392 appears last then no additional information is added to debugging output.
23394 @item monitor set libthread-db-search-path [PATH]
23395 @cindex gdbserver, search path for @code{libthread_db}
23396 When this command is issued, @var{path} is a colon-separated list of
23397 directories to search for @code{libthread_db} (@pxref{Threads,,set
23398 libthread-db-search-path}). If you omit @var{path},
23399 @samp{libthread-db-search-path} will be reset to its default value.
23401 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23402 not supported in @code{gdbserver}.
23405 Tell gdbserver to exit immediately. This command should be followed by
23406 @code{disconnect} to close the debugging session. @code{gdbserver} will
23407 detach from any attached processes and kill any processes it created.
23408 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23409 of a multi-process mode debug session.
23413 @subsection Tracepoints support in @code{gdbserver}
23414 @cindex tracepoints support in @code{gdbserver}
23416 On some targets, @code{gdbserver} supports tracepoints, fast
23417 tracepoints and static tracepoints.
23419 For fast or static tracepoints to work, a special library called the
23420 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23421 This library is built and distributed as an integral part of
23422 @code{gdbserver}. In addition, support for static tracepoints
23423 requires building the in-process agent library with static tracepoints
23424 support. At present, the UST (LTTng Userspace Tracer,
23425 @url{http://lttng.org/ust}) tracing engine is supported. This support
23426 is automatically available if UST development headers are found in the
23427 standard include path when @code{gdbserver} is built, or if
23428 @code{gdbserver} was explicitly configured using @option{--with-ust}
23429 to point at such headers. You can explicitly disable the support
23430 using @option{--with-ust=no}.
23432 There are several ways to load the in-process agent in your program:
23435 @item Specifying it as dependency at link time
23437 You can link your program dynamically with the in-process agent
23438 library. On most systems, this is accomplished by adding
23439 @code{-linproctrace} to the link command.
23441 @item Using the system's preloading mechanisms
23443 You can force loading the in-process agent at startup time by using
23444 your system's support for preloading shared libraries. Many Unixes
23445 support the concept of preloading user defined libraries. In most
23446 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23447 in the environment. See also the description of @code{gdbserver}'s
23448 @option{--wrapper} command line option.
23450 @item Using @value{GDBN} to force loading the agent at run time
23452 On some systems, you can force the inferior to load a shared library,
23453 by calling a dynamic loader function in the inferior that takes care
23454 of dynamically looking up and loading a shared library. On most Unix
23455 systems, the function is @code{dlopen}. You'll use the @code{call}
23456 command for that. For example:
23459 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23462 Note that on most Unix systems, for the @code{dlopen} function to be
23463 available, the program needs to be linked with @code{-ldl}.
23466 On systems that have a userspace dynamic loader, like most Unix
23467 systems, when you connect to @code{gdbserver} using @code{target
23468 remote}, you'll find that the program is stopped at the dynamic
23469 loader's entry point, and no shared library has been loaded in the
23470 program's address space yet, including the in-process agent. In that
23471 case, before being able to use any of the fast or static tracepoints
23472 features, you need to let the loader run and load the shared
23473 libraries. The simplest way to do that is to run the program to the
23474 main procedure. E.g., if debugging a C or C@t{++} program, start
23475 @code{gdbserver} like so:
23478 $ gdbserver :9999 myprogram
23481 Start GDB and connect to @code{gdbserver} like so, and run to main:
23485 (@value{GDBP}) target remote myhost:9999
23486 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23487 (@value{GDBP}) b main
23488 (@value{GDBP}) continue
23491 The in-process tracing agent library should now be loaded into the
23492 process; you can confirm it with the @code{info sharedlibrary}
23493 command, which will list @file{libinproctrace.so} as loaded in the
23494 process. You are now ready to install fast tracepoints, list static
23495 tracepoint markers, probe static tracepoints markers, and start
23498 @node Remote Configuration
23499 @section Remote Configuration
23502 @kindex show remote
23503 This section documents the configuration options available when
23504 debugging remote programs. For the options related to the File I/O
23505 extensions of the remote protocol, see @ref{system,
23506 system-call-allowed}.
23509 @item set remoteaddresssize @var{bits}
23510 @cindex address size for remote targets
23511 @cindex bits in remote address
23512 Set the maximum size of address in a memory packet to the specified
23513 number of bits. @value{GDBN} will mask off the address bits above
23514 that number, when it passes addresses to the remote target. The
23515 default value is the number of bits in the target's address.
23517 @item show remoteaddresssize
23518 Show the current value of remote address size in bits.
23520 @item set serial baud @var{n}
23521 @cindex baud rate for remote targets
23522 Set the baud rate for the remote serial I/O to @var{n} baud. The
23523 value is used to set the speed of the serial port used for debugging
23526 @item show serial baud
23527 Show the current speed of the remote connection.
23529 @item set serial parity @var{parity}
23530 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23531 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23533 @item show serial parity
23534 Show the current parity of the serial port.
23536 @item set remotebreak
23537 @cindex interrupt remote programs
23538 @cindex BREAK signal instead of Ctrl-C
23539 @anchor{set remotebreak}
23540 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23541 when you type @kbd{Ctrl-c} to interrupt the program running
23542 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23543 character instead. The default is off, since most remote systems
23544 expect to see @samp{Ctrl-C} as the interrupt signal.
23546 @item show remotebreak
23547 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23548 interrupt the remote program.
23550 @item set remoteflow on
23551 @itemx set remoteflow off
23552 @kindex set remoteflow
23553 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23554 on the serial port used to communicate to the remote target.
23556 @item show remoteflow
23557 @kindex show remoteflow
23558 Show the current setting of hardware flow control.
23560 @item set remotelogbase @var{base}
23561 Set the base (a.k.a.@: radix) of logging serial protocol
23562 communications to @var{base}. Supported values of @var{base} are:
23563 @code{ascii}, @code{octal}, and @code{hex}. The default is
23566 @item show remotelogbase
23567 Show the current setting of the radix for logging remote serial
23570 @item set remotelogfile @var{file}
23571 @cindex record serial communications on file
23572 Record remote serial communications on the named @var{file}. The
23573 default is not to record at all.
23575 @item show remotelogfile
23576 Show the current setting of the file name on which to record the
23577 serial communications.
23579 @item set remotetimeout @var{num}
23580 @cindex timeout for serial communications
23581 @cindex remote timeout
23582 Set the timeout limit to wait for the remote target to respond to
23583 @var{num} seconds. The default is 2 seconds.
23585 @item show remotetimeout
23586 Show the current number of seconds to wait for the remote target
23589 @cindex limit hardware breakpoints and watchpoints
23590 @cindex remote target, limit break- and watchpoints
23591 @anchor{set remote hardware-watchpoint-limit}
23592 @anchor{set remote hardware-breakpoint-limit}
23593 @item set remote hardware-watchpoint-limit @var{limit}
23594 @itemx set remote hardware-breakpoint-limit @var{limit}
23595 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23596 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23597 watchpoints or breakpoints, and @code{unlimited} for unlimited
23598 watchpoints or breakpoints.
23600 @item show remote hardware-watchpoint-limit
23601 @itemx show remote hardware-breakpoint-limit
23602 Show the current limit for the number of hardware watchpoints or
23603 breakpoints that @value{GDBN} can use.
23605 @cindex limit hardware watchpoints length
23606 @cindex remote target, limit watchpoints length
23607 @anchor{set remote hardware-watchpoint-length-limit}
23608 @item set remote hardware-watchpoint-length-limit @var{limit}
23609 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23610 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23611 hardware watchpoints and @code{unlimited} allows watchpoints of any
23614 @item show remote hardware-watchpoint-length-limit
23615 Show the current limit (in bytes) of the maximum length of
23616 a remote hardware watchpoint.
23618 @item set remote exec-file @var{filename}
23619 @itemx show remote exec-file
23620 @anchor{set remote exec-file}
23621 @cindex executable file, for remote target
23622 Select the file used for @code{run} with @code{target
23623 extended-remote}. This should be set to a filename valid on the
23624 target system. If it is not set, the target will use a default
23625 filename (e.g.@: the last program run).
23627 @item set remote interrupt-sequence
23628 @cindex interrupt remote programs
23629 @cindex select Ctrl-C, BREAK or BREAK-g
23630 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23631 @samp{BREAK-g} as the
23632 sequence to the remote target in order to interrupt the execution.
23633 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23634 is high level of serial line for some certain time.
23635 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23636 It is @code{BREAK} signal followed by character @code{g}.
23638 @item show remote interrupt-sequence
23639 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23640 is sent by @value{GDBN} to interrupt the remote program.
23641 @code{BREAK-g} is BREAK signal followed by @code{g} and
23642 also known as Magic SysRq g.
23644 @item set remote interrupt-on-connect
23645 @cindex send interrupt-sequence on start
23646 Specify whether interrupt-sequence is sent to remote target when
23647 @value{GDBN} connects to it. This is mostly needed when you debug
23648 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23649 which is known as Magic SysRq g in order to connect @value{GDBN}.
23651 @item show remote interrupt-on-connect
23652 Show whether interrupt-sequence is sent
23653 to remote target when @value{GDBN} connects to it.
23657 @item set tcp auto-retry on
23658 @cindex auto-retry, for remote TCP target
23659 Enable auto-retry for remote TCP connections. This is useful if the remote
23660 debugging agent is launched in parallel with @value{GDBN}; there is a race
23661 condition because the agent may not become ready to accept the connection
23662 before @value{GDBN} attempts to connect. When auto-retry is
23663 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23664 to establish the connection using the timeout specified by
23665 @code{set tcp connect-timeout}.
23667 @item set tcp auto-retry off
23668 Do not auto-retry failed TCP connections.
23670 @item show tcp auto-retry
23671 Show the current auto-retry setting.
23673 @item set tcp connect-timeout @var{seconds}
23674 @itemx set tcp connect-timeout unlimited
23675 @cindex connection timeout, for remote TCP target
23676 @cindex timeout, for remote target connection
23677 Set the timeout for establishing a TCP connection to the remote target to
23678 @var{seconds}. The timeout affects both polling to retry failed connections
23679 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23680 that are merely slow to complete, and represents an approximate cumulative
23681 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23682 @value{GDBN} will keep attempting to establish a connection forever,
23683 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23685 @item show tcp connect-timeout
23686 Show the current connection timeout setting.
23689 @cindex remote packets, enabling and disabling
23690 The @value{GDBN} remote protocol autodetects the packets supported by
23691 your debugging stub. If you need to override the autodetection, you
23692 can use these commands to enable or disable individual packets. Each
23693 packet can be set to @samp{on} (the remote target supports this
23694 packet), @samp{off} (the remote target does not support this packet),
23695 or @samp{auto} (detect remote target support for this packet). They
23696 all default to @samp{auto}. For more information about each packet,
23697 see @ref{Remote Protocol}.
23699 During normal use, you should not have to use any of these commands.
23700 If you do, that may be a bug in your remote debugging stub, or a bug
23701 in @value{GDBN}. You may want to report the problem to the
23702 @value{GDBN} developers.
23704 For each packet @var{name}, the command to enable or disable the
23705 packet is @code{set remote @var{name}-packet}. The available settings
23708 @multitable @columnfractions 0.28 0.32 0.25
23711 @tab Related Features
23713 @item @code{fetch-register}
23715 @tab @code{info registers}
23717 @item @code{set-register}
23721 @item @code{binary-download}
23723 @tab @code{load}, @code{set}
23725 @item @code{read-aux-vector}
23726 @tab @code{qXfer:auxv:read}
23727 @tab @code{info auxv}
23729 @item @code{symbol-lookup}
23730 @tab @code{qSymbol}
23731 @tab Detecting multiple threads
23733 @item @code{attach}
23734 @tab @code{vAttach}
23737 @item @code{verbose-resume}
23739 @tab Stepping or resuming multiple threads
23745 @item @code{software-breakpoint}
23749 @item @code{hardware-breakpoint}
23753 @item @code{write-watchpoint}
23757 @item @code{read-watchpoint}
23761 @item @code{access-watchpoint}
23765 @item @code{pid-to-exec-file}
23766 @tab @code{qXfer:exec-file:read}
23767 @tab @code{attach}, @code{run}
23769 @item @code{target-features}
23770 @tab @code{qXfer:features:read}
23771 @tab @code{set architecture}
23773 @item @code{library-info}
23774 @tab @code{qXfer:libraries:read}
23775 @tab @code{info sharedlibrary}
23777 @item @code{memory-map}
23778 @tab @code{qXfer:memory-map:read}
23779 @tab @code{info mem}
23781 @item @code{read-sdata-object}
23782 @tab @code{qXfer:sdata:read}
23783 @tab @code{print $_sdata}
23785 @item @code{read-siginfo-object}
23786 @tab @code{qXfer:siginfo:read}
23787 @tab @code{print $_siginfo}
23789 @item @code{write-siginfo-object}
23790 @tab @code{qXfer:siginfo:write}
23791 @tab @code{set $_siginfo}
23793 @item @code{threads}
23794 @tab @code{qXfer:threads:read}
23795 @tab @code{info threads}
23797 @item @code{get-thread-local-@*storage-address}
23798 @tab @code{qGetTLSAddr}
23799 @tab Displaying @code{__thread} variables
23801 @item @code{get-thread-information-block-address}
23802 @tab @code{qGetTIBAddr}
23803 @tab Display MS-Windows Thread Information Block.
23805 @item @code{search-memory}
23806 @tab @code{qSearch:memory}
23809 @item @code{supported-packets}
23810 @tab @code{qSupported}
23811 @tab Remote communications parameters
23813 @item @code{catch-syscalls}
23814 @tab @code{QCatchSyscalls}
23815 @tab @code{catch syscall}
23817 @item @code{pass-signals}
23818 @tab @code{QPassSignals}
23819 @tab @code{handle @var{signal}}
23821 @item @code{program-signals}
23822 @tab @code{QProgramSignals}
23823 @tab @code{handle @var{signal}}
23825 @item @code{hostio-close-packet}
23826 @tab @code{vFile:close}
23827 @tab @code{remote get}, @code{remote put}
23829 @item @code{hostio-open-packet}
23830 @tab @code{vFile:open}
23831 @tab @code{remote get}, @code{remote put}
23833 @item @code{hostio-pread-packet}
23834 @tab @code{vFile:pread}
23835 @tab @code{remote get}, @code{remote put}
23837 @item @code{hostio-pwrite-packet}
23838 @tab @code{vFile:pwrite}
23839 @tab @code{remote get}, @code{remote put}
23841 @item @code{hostio-unlink-packet}
23842 @tab @code{vFile:unlink}
23843 @tab @code{remote delete}
23845 @item @code{hostio-readlink-packet}
23846 @tab @code{vFile:readlink}
23849 @item @code{hostio-fstat-packet}
23850 @tab @code{vFile:fstat}
23853 @item @code{hostio-setfs-packet}
23854 @tab @code{vFile:setfs}
23857 @item @code{noack-packet}
23858 @tab @code{QStartNoAckMode}
23859 @tab Packet acknowledgment
23861 @item @code{osdata}
23862 @tab @code{qXfer:osdata:read}
23863 @tab @code{info os}
23865 @item @code{query-attached}
23866 @tab @code{qAttached}
23867 @tab Querying remote process attach state.
23869 @item @code{trace-buffer-size}
23870 @tab @code{QTBuffer:size}
23871 @tab @code{set trace-buffer-size}
23873 @item @code{trace-status}
23874 @tab @code{qTStatus}
23875 @tab @code{tstatus}
23877 @item @code{traceframe-info}
23878 @tab @code{qXfer:traceframe-info:read}
23879 @tab Traceframe info
23881 @item @code{install-in-trace}
23882 @tab @code{InstallInTrace}
23883 @tab Install tracepoint in tracing
23885 @item @code{disable-randomization}
23886 @tab @code{QDisableRandomization}
23887 @tab @code{set disable-randomization}
23889 @item @code{startup-with-shell}
23890 @tab @code{QStartupWithShell}
23891 @tab @code{set startup-with-shell}
23893 @item @code{environment-hex-encoded}
23894 @tab @code{QEnvironmentHexEncoded}
23895 @tab @code{set environment}
23897 @item @code{environment-unset}
23898 @tab @code{QEnvironmentUnset}
23899 @tab @code{unset environment}
23901 @item @code{environment-reset}
23902 @tab @code{QEnvironmentReset}
23903 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23905 @item @code{set-working-dir}
23906 @tab @code{QSetWorkingDir}
23907 @tab @code{set cwd}
23909 @item @code{conditional-breakpoints-packet}
23910 @tab @code{Z0 and Z1}
23911 @tab @code{Support for target-side breakpoint condition evaluation}
23913 @item @code{multiprocess-extensions}
23914 @tab @code{multiprocess extensions}
23915 @tab Debug multiple processes and remote process PID awareness
23917 @item @code{swbreak-feature}
23918 @tab @code{swbreak stop reason}
23921 @item @code{hwbreak-feature}
23922 @tab @code{hwbreak stop reason}
23925 @item @code{fork-event-feature}
23926 @tab @code{fork stop reason}
23929 @item @code{vfork-event-feature}
23930 @tab @code{vfork stop reason}
23933 @item @code{exec-event-feature}
23934 @tab @code{exec stop reason}
23937 @item @code{thread-events}
23938 @tab @code{QThreadEvents}
23939 @tab Tracking thread lifetime.
23941 @item @code{no-resumed-stop-reply}
23942 @tab @code{no resumed thread left stop reply}
23943 @tab Tracking thread lifetime.
23948 @section Implementing a Remote Stub
23950 @cindex debugging stub, example
23951 @cindex remote stub, example
23952 @cindex stub example, remote debugging
23953 The stub files provided with @value{GDBN} implement the target side of the
23954 communication protocol, and the @value{GDBN} side is implemented in the
23955 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23956 these subroutines to communicate, and ignore the details. (If you're
23957 implementing your own stub file, you can still ignore the details: start
23958 with one of the existing stub files. @file{sparc-stub.c} is the best
23959 organized, and therefore the easiest to read.)
23961 @cindex remote serial debugging, overview
23962 To debug a program running on another machine (the debugging
23963 @dfn{target} machine), you must first arrange for all the usual
23964 prerequisites for the program to run by itself. For example, for a C
23969 A startup routine to set up the C runtime environment; these usually
23970 have a name like @file{crt0}. The startup routine may be supplied by
23971 your hardware supplier, or you may have to write your own.
23974 A C subroutine library to support your program's
23975 subroutine calls, notably managing input and output.
23978 A way of getting your program to the other machine---for example, a
23979 download program. These are often supplied by the hardware
23980 manufacturer, but you may have to write your own from hardware
23984 The next step is to arrange for your program to use a serial port to
23985 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23986 machine). In general terms, the scheme looks like this:
23990 @value{GDBN} already understands how to use this protocol; when everything
23991 else is set up, you can simply use the @samp{target remote} command
23992 (@pxref{Targets,,Specifying a Debugging Target}).
23994 @item On the target,
23995 you must link with your program a few special-purpose subroutines that
23996 implement the @value{GDBN} remote serial protocol. The file containing these
23997 subroutines is called a @dfn{debugging stub}.
23999 On certain remote targets, you can use an auxiliary program
24000 @code{gdbserver} instead of linking a stub into your program.
24001 @xref{Server,,Using the @code{gdbserver} Program}, for details.
24004 The debugging stub is specific to the architecture of the remote
24005 machine; for example, use @file{sparc-stub.c} to debug programs on
24008 @cindex remote serial stub list
24009 These working remote stubs are distributed with @value{GDBN}:
24014 @cindex @file{i386-stub.c}
24017 For Intel 386 and compatible architectures.
24020 @cindex @file{m68k-stub.c}
24021 @cindex Motorola 680x0
24023 For Motorola 680x0 architectures.
24026 @cindex @file{sh-stub.c}
24029 For Renesas SH architectures.
24032 @cindex @file{sparc-stub.c}
24034 For @sc{sparc} architectures.
24036 @item sparcl-stub.c
24037 @cindex @file{sparcl-stub.c}
24040 For Fujitsu @sc{sparclite} architectures.
24044 The @file{README} file in the @value{GDBN} distribution may list other
24045 recently added stubs.
24048 * Stub Contents:: What the stub can do for you
24049 * Bootstrapping:: What you must do for the stub
24050 * Debug Session:: Putting it all together
24053 @node Stub Contents
24054 @subsection What the Stub Can Do for You
24056 @cindex remote serial stub
24057 The debugging stub for your architecture supplies these three
24061 @item set_debug_traps
24062 @findex set_debug_traps
24063 @cindex remote serial stub, initialization
24064 This routine arranges for @code{handle_exception} to run when your
24065 program stops. You must call this subroutine explicitly in your
24066 program's startup code.
24068 @item handle_exception
24069 @findex handle_exception
24070 @cindex remote serial stub, main routine
24071 This is the central workhorse, but your program never calls it
24072 explicitly---the setup code arranges for @code{handle_exception} to
24073 run when a trap is triggered.
24075 @code{handle_exception} takes control when your program stops during
24076 execution (for example, on a breakpoint), and mediates communications
24077 with @value{GDBN} on the host machine. This is where the communications
24078 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24079 representative on the target machine. It begins by sending summary
24080 information on the state of your program, then continues to execute,
24081 retrieving and transmitting any information @value{GDBN} needs, until you
24082 execute a @value{GDBN} command that makes your program resume; at that point,
24083 @code{handle_exception} returns control to your own code on the target
24087 @cindex @code{breakpoint} subroutine, remote
24088 Use this auxiliary subroutine to make your program contain a
24089 breakpoint. Depending on the particular situation, this may be the only
24090 way for @value{GDBN} to get control. For instance, if your target
24091 machine has some sort of interrupt button, you won't need to call this;
24092 pressing the interrupt button transfers control to
24093 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24094 simply receiving characters on the serial port may also trigger a trap;
24095 again, in that situation, you don't need to call @code{breakpoint} from
24096 your own program---simply running @samp{target remote} from the host
24097 @value{GDBN} session gets control.
24099 Call @code{breakpoint} if none of these is true, or if you simply want
24100 to make certain your program stops at a predetermined point for the
24101 start of your debugging session.
24104 @node Bootstrapping
24105 @subsection What You Must Do for the Stub
24107 @cindex remote stub, support routines
24108 The debugging stubs that come with @value{GDBN} are set up for a particular
24109 chip architecture, but they have no information about the rest of your
24110 debugging target machine.
24112 First of all you need to tell the stub how to communicate with the
24116 @item int getDebugChar()
24117 @findex getDebugChar
24118 Write this subroutine to read a single character from the serial port.
24119 It may be identical to @code{getchar} for your target system; a
24120 different name is used to allow you to distinguish the two if you wish.
24122 @item void putDebugChar(int)
24123 @findex putDebugChar
24124 Write this subroutine to write a single character to the serial port.
24125 It may be identical to @code{putchar} for your target system; a
24126 different name is used to allow you to distinguish the two if you wish.
24129 @cindex control C, and remote debugging
24130 @cindex interrupting remote targets
24131 If you want @value{GDBN} to be able to stop your program while it is
24132 running, you need to use an interrupt-driven serial driver, and arrange
24133 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24134 character). That is the character which @value{GDBN} uses to tell the
24135 remote system to stop.
24137 Getting the debugging target to return the proper status to @value{GDBN}
24138 probably requires changes to the standard stub; one quick and dirty way
24139 is to just execute a breakpoint instruction (the ``dirty'' part is that
24140 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24142 Other routines you need to supply are:
24145 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24146 @findex exceptionHandler
24147 Write this function to install @var{exception_address} in the exception
24148 handling tables. You need to do this because the stub does not have any
24149 way of knowing what the exception handling tables on your target system
24150 are like (for example, the processor's table might be in @sc{rom},
24151 containing entries which point to a table in @sc{ram}).
24152 The @var{exception_number} specifies the exception which should be changed;
24153 its meaning is architecture-dependent (for example, different numbers
24154 might represent divide by zero, misaligned access, etc). When this
24155 exception occurs, control should be transferred directly to
24156 @var{exception_address}, and the processor state (stack, registers,
24157 and so on) should be just as it is when a processor exception occurs. So if
24158 you want to use a jump instruction to reach @var{exception_address}, it
24159 should be a simple jump, not a jump to subroutine.
24161 For the 386, @var{exception_address} should be installed as an interrupt
24162 gate so that interrupts are masked while the handler runs. The gate
24163 should be at privilege level 0 (the most privileged level). The
24164 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24165 help from @code{exceptionHandler}.
24167 @item void flush_i_cache()
24168 @findex flush_i_cache
24169 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24170 instruction cache, if any, on your target machine. If there is no
24171 instruction cache, this subroutine may be a no-op.
24173 On target machines that have instruction caches, @value{GDBN} requires this
24174 function to make certain that the state of your program is stable.
24178 You must also make sure this library routine is available:
24181 @item void *memset(void *, int, int)
24183 This is the standard library function @code{memset} that sets an area of
24184 memory to a known value. If you have one of the free versions of
24185 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24186 either obtain it from your hardware manufacturer, or write your own.
24189 If you do not use the GNU C compiler, you may need other standard
24190 library subroutines as well; this varies from one stub to another,
24191 but in general the stubs are likely to use any of the common library
24192 subroutines which @code{@value{NGCC}} generates as inline code.
24195 @node Debug Session
24196 @subsection Putting it All Together
24198 @cindex remote serial debugging summary
24199 In summary, when your program is ready to debug, you must follow these
24204 Make sure you have defined the supporting low-level routines
24205 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24207 @code{getDebugChar}, @code{putDebugChar},
24208 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24212 Insert these lines in your program's startup code, before the main
24213 procedure is called:
24220 On some machines, when a breakpoint trap is raised, the hardware
24221 automatically makes the PC point to the instruction after the
24222 breakpoint. If your machine doesn't do that, you may need to adjust
24223 @code{handle_exception} to arrange for it to return to the instruction
24224 after the breakpoint on this first invocation, so that your program
24225 doesn't keep hitting the initial breakpoint instead of making
24229 For the 680x0 stub only, you need to provide a variable called
24230 @code{exceptionHook}. Normally you just use:
24233 void (*exceptionHook)() = 0;
24237 but if before calling @code{set_debug_traps}, you set it to point to a
24238 function in your program, that function is called when
24239 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24240 error). The function indicated by @code{exceptionHook} is called with
24241 one parameter: an @code{int} which is the exception number.
24244 Compile and link together: your program, the @value{GDBN} debugging stub for
24245 your target architecture, and the supporting subroutines.
24248 Make sure you have a serial connection between your target machine and
24249 the @value{GDBN} host, and identify the serial port on the host.
24252 @c The "remote" target now provides a `load' command, so we should
24253 @c document that. FIXME.
24254 Download your program to your target machine (or get it there by
24255 whatever means the manufacturer provides), and start it.
24258 Start @value{GDBN} on the host, and connect to the target
24259 (@pxref{Connecting,,Connecting to a Remote Target}).
24263 @node Configurations
24264 @chapter Configuration-Specific Information
24266 While nearly all @value{GDBN} commands are available for all native and
24267 cross versions of the debugger, there are some exceptions. This chapter
24268 describes things that are only available in certain configurations.
24270 There are three major categories of configurations: native
24271 configurations, where the host and target are the same, embedded
24272 operating system configurations, which are usually the same for several
24273 different processor architectures, and bare embedded processors, which
24274 are quite different from each other.
24279 * Embedded Processors::
24286 This section describes details specific to particular native
24290 * BSD libkvm Interface:: Debugging BSD kernel memory images
24291 * Process Information:: Process information
24292 * DJGPP Native:: Features specific to the DJGPP port
24293 * Cygwin Native:: Features specific to the Cygwin port
24294 * Hurd Native:: Features specific to @sc{gnu} Hurd
24295 * Darwin:: Features specific to Darwin
24296 * FreeBSD:: Features specific to FreeBSD
24299 @node BSD libkvm Interface
24300 @subsection BSD libkvm Interface
24303 @cindex kernel memory image
24304 @cindex kernel crash dump
24306 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24307 interface that provides a uniform interface for accessing kernel virtual
24308 memory images, including live systems and crash dumps. @value{GDBN}
24309 uses this interface to allow you to debug live kernels and kernel crash
24310 dumps on many native BSD configurations. This is implemented as a
24311 special @code{kvm} debugging target. For debugging a live system, load
24312 the currently running kernel into @value{GDBN} and connect to the
24316 (@value{GDBP}) @b{target kvm}
24319 For debugging crash dumps, provide the file name of the crash dump as an
24323 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24326 Once connected to the @code{kvm} target, the following commands are
24332 Set current context from the @dfn{Process Control Block} (PCB) address.
24335 Set current context from proc address. This command isn't available on
24336 modern FreeBSD systems.
24339 @node Process Information
24340 @subsection Process Information
24342 @cindex examine process image
24343 @cindex process info via @file{/proc}
24345 Some operating systems provide interfaces to fetch additional
24346 information about running processes beyond memory and per-thread
24347 register state. If @value{GDBN} is configured for an operating system
24348 with a supported interface, the command @code{info proc} is available
24349 to report information about the process running your program, or about
24350 any process running on your system.
24352 One supported interface is a facility called @samp{/proc} that can be
24353 used to examine the image of a running process using file-system
24354 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24357 On FreeBSD and NetBSD systems, system control nodes are used to query
24358 process information.
24360 In addition, some systems may provide additional process information
24361 in core files. Note that a core file may include a subset of the
24362 information available from a live process. Process information is
24363 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24370 @itemx info proc @var{process-id}
24371 Summarize available information about a process. If a
24372 process ID is specified by @var{process-id}, display information about
24373 that process; otherwise display information about the program being
24374 debugged. The summary includes the debugged process ID, the command
24375 line used to invoke it, its current working directory, and its
24376 executable file's absolute file name.
24378 On some systems, @var{process-id} can be of the form
24379 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24380 within a process. If the optional @var{pid} part is missing, it means
24381 a thread from the process being debugged (the leading @samp{/} still
24382 needs to be present, or else @value{GDBN} will interpret the number as
24383 a process ID rather than a thread ID).
24385 @item info proc cmdline
24386 @cindex info proc cmdline
24387 Show the original command line of the process. This command is
24388 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24390 @item info proc cwd
24391 @cindex info proc cwd
24392 Show the current working directory of the process. This command is
24393 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24395 @item info proc exe
24396 @cindex info proc exe
24397 Show the name of executable of the process. This command is supported
24398 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24400 @item info proc files
24401 @cindex info proc files
24402 Show the file descriptors open by the process. For each open file
24403 descriptor, @value{GDBN} shows its number, type (file, directory,
24404 character device, socket), file pointer offset, and the name of the
24405 resource open on the descriptor. The resource name can be a file name
24406 (for files, directories, and devices) or a protocol followed by socket
24407 address (for network connections). This command is supported on
24410 This example shows the open file descriptors for a process using a
24411 tty for standard input and output as well as two network sockets:
24414 (gdb) info proc files 22136
24418 FD Type Offset Flags Name
24419 text file - r-------- /usr/bin/ssh
24420 ctty chr - rw------- /dev/pts/20
24421 cwd dir - r-------- /usr/home/john
24422 root dir - r-------- /
24423 0 chr 0x32933a4 rw------- /dev/pts/20
24424 1 chr 0x32933a4 rw------- /dev/pts/20
24425 2 chr 0x32933a4 rw------- /dev/pts/20
24426 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24427 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24430 @item info proc mappings
24431 @cindex memory address space mappings
24432 Report the memory address space ranges accessible in a process. On
24433 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24434 on whether the process has read, write, or execute access rights to each
24435 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24436 includes the object file which is mapped to that range.
24438 @item info proc stat
24439 @itemx info proc status
24440 @cindex process detailed status information
24441 Show additional process-related information, including the user ID and
24442 group ID; virtual memory usage; the signals that are pending, blocked,
24443 and ignored; its TTY; its consumption of system and user time; its
24444 stack size; its @samp{nice} value; etc. These commands are supported
24445 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24447 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24448 information (type @kbd{man 5 proc} from your shell prompt).
24450 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24451 @code{info proc status}.
24453 @item info proc all
24454 Show all the information about the process described under all of the
24455 above @code{info proc} subcommands.
24458 @comment These sub-options of 'info proc' were not included when
24459 @comment procfs.c was re-written. Keep their descriptions around
24460 @comment against the day when someone finds the time to put them back in.
24461 @kindex info proc times
24462 @item info proc times
24463 Starting time, user CPU time, and system CPU time for your program and
24466 @kindex info proc id
24468 Report on the process IDs related to your program: its own process ID,
24469 the ID of its parent, the process group ID, and the session ID.
24472 @item set procfs-trace
24473 @kindex set procfs-trace
24474 @cindex @code{procfs} API calls
24475 This command enables and disables tracing of @code{procfs} API calls.
24477 @item show procfs-trace
24478 @kindex show procfs-trace
24479 Show the current state of @code{procfs} API call tracing.
24481 @item set procfs-file @var{file}
24482 @kindex set procfs-file
24483 Tell @value{GDBN} to write @code{procfs} API trace to the named
24484 @var{file}. @value{GDBN} appends the trace info to the previous
24485 contents of the file. The default is to display the trace on the
24488 @item show procfs-file
24489 @kindex show procfs-file
24490 Show the file to which @code{procfs} API trace is written.
24492 @item proc-trace-entry
24493 @itemx proc-trace-exit
24494 @itemx proc-untrace-entry
24495 @itemx proc-untrace-exit
24496 @kindex proc-trace-entry
24497 @kindex proc-trace-exit
24498 @kindex proc-untrace-entry
24499 @kindex proc-untrace-exit
24500 These commands enable and disable tracing of entries into and exits
24501 from the @code{syscall} interface.
24504 @kindex info pidlist
24505 @cindex process list, QNX Neutrino
24506 For QNX Neutrino only, this command displays the list of all the
24507 processes and all the threads within each process.
24510 @kindex info meminfo
24511 @cindex mapinfo list, QNX Neutrino
24512 For QNX Neutrino only, this command displays the list of all mapinfos.
24516 @subsection Features for Debugging @sc{djgpp} Programs
24517 @cindex @sc{djgpp} debugging
24518 @cindex native @sc{djgpp} debugging
24519 @cindex MS-DOS-specific commands
24522 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24523 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24524 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24525 top of real-mode DOS systems and their emulations.
24527 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24528 defines a few commands specific to the @sc{djgpp} port. This
24529 subsection describes those commands.
24534 This is a prefix of @sc{djgpp}-specific commands which print
24535 information about the target system and important OS structures.
24538 @cindex MS-DOS system info
24539 @cindex free memory information (MS-DOS)
24540 @item info dos sysinfo
24541 This command displays assorted information about the underlying
24542 platform: the CPU type and features, the OS version and flavor, the
24543 DPMI version, and the available conventional and DPMI memory.
24548 @cindex segment descriptor tables
24549 @cindex descriptor tables display
24551 @itemx info dos ldt
24552 @itemx info dos idt
24553 These 3 commands display entries from, respectively, Global, Local,
24554 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24555 tables are data structures which store a descriptor for each segment
24556 that is currently in use. The segment's selector is an index into a
24557 descriptor table; the table entry for that index holds the
24558 descriptor's base address and limit, and its attributes and access
24561 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24562 segment (used for both data and the stack), and a DOS segment (which
24563 allows access to DOS/BIOS data structures and absolute addresses in
24564 conventional memory). However, the DPMI host will usually define
24565 additional segments in order to support the DPMI environment.
24567 @cindex garbled pointers
24568 These commands allow to display entries from the descriptor tables.
24569 Without an argument, all entries from the specified table are
24570 displayed. An argument, which should be an integer expression, means
24571 display a single entry whose index is given by the argument. For
24572 example, here's a convenient way to display information about the
24573 debugged program's data segment:
24576 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24577 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24581 This comes in handy when you want to see whether a pointer is outside
24582 the data segment's limit (i.e.@: @dfn{garbled}).
24584 @cindex page tables display (MS-DOS)
24586 @itemx info dos pte
24587 These two commands display entries from, respectively, the Page
24588 Directory and the Page Tables. Page Directories and Page Tables are
24589 data structures which control how virtual memory addresses are mapped
24590 into physical addresses. A Page Table includes an entry for every
24591 page of memory that is mapped into the program's address space; there
24592 may be several Page Tables, each one holding up to 4096 entries. A
24593 Page Directory has up to 4096 entries, one each for every Page Table
24594 that is currently in use.
24596 Without an argument, @kbd{info dos pde} displays the entire Page
24597 Directory, and @kbd{info dos pte} displays all the entries in all of
24598 the Page Tables. An argument, an integer expression, given to the
24599 @kbd{info dos pde} command means display only that entry from the Page
24600 Directory table. An argument given to the @kbd{info dos pte} command
24601 means display entries from a single Page Table, the one pointed to by
24602 the specified entry in the Page Directory.
24604 @cindex direct memory access (DMA) on MS-DOS
24605 These commands are useful when your program uses @dfn{DMA} (Direct
24606 Memory Access), which needs physical addresses to program the DMA
24609 These commands are supported only with some DPMI servers.
24611 @cindex physical address from linear address
24612 @item info dos address-pte @var{addr}
24613 This command displays the Page Table entry for a specified linear
24614 address. The argument @var{addr} is a linear address which should
24615 already have the appropriate segment's base address added to it,
24616 because this command accepts addresses which may belong to @emph{any}
24617 segment. For example, here's how to display the Page Table entry for
24618 the page where a variable @code{i} is stored:
24621 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24622 @exdent @code{Page Table entry for address 0x11a00d30:}
24623 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24627 This says that @code{i} is stored at offset @code{0xd30} from the page
24628 whose physical base address is @code{0x02698000}, and shows all the
24629 attributes of that page.
24631 Note that you must cast the addresses of variables to a @code{char *},
24632 since otherwise the value of @code{__djgpp_base_address}, the base
24633 address of all variables and functions in a @sc{djgpp} program, will
24634 be added using the rules of C pointer arithmetics: if @code{i} is
24635 declared an @code{int}, @value{GDBN} will add 4 times the value of
24636 @code{__djgpp_base_address} to the address of @code{i}.
24638 Here's another example, it displays the Page Table entry for the
24642 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24643 @exdent @code{Page Table entry for address 0x29110:}
24644 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24648 (The @code{+ 3} offset is because the transfer buffer's address is the
24649 3rd member of the @code{_go32_info_block} structure.) The output
24650 clearly shows that this DPMI server maps the addresses in conventional
24651 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24652 linear (@code{0x29110}) addresses are identical.
24654 This command is supported only with some DPMI servers.
24657 @cindex DOS serial data link, remote debugging
24658 In addition to native debugging, the DJGPP port supports remote
24659 debugging via a serial data link. The following commands are specific
24660 to remote serial debugging in the DJGPP port of @value{GDBN}.
24663 @kindex set com1base
24664 @kindex set com1irq
24665 @kindex set com2base
24666 @kindex set com2irq
24667 @kindex set com3base
24668 @kindex set com3irq
24669 @kindex set com4base
24670 @kindex set com4irq
24671 @item set com1base @var{addr}
24672 This command sets the base I/O port address of the @file{COM1} serial
24675 @item set com1irq @var{irq}
24676 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24677 for the @file{COM1} serial port.
24679 There are similar commands @samp{set com2base}, @samp{set com3irq},
24680 etc.@: for setting the port address and the @code{IRQ} lines for the
24683 @kindex show com1base
24684 @kindex show com1irq
24685 @kindex show com2base
24686 @kindex show com2irq
24687 @kindex show com3base
24688 @kindex show com3irq
24689 @kindex show com4base
24690 @kindex show com4irq
24691 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24692 display the current settings of the base address and the @code{IRQ}
24693 lines used by the COM ports.
24696 @kindex info serial
24697 @cindex DOS serial port status
24698 This command prints the status of the 4 DOS serial ports. For each
24699 port, it prints whether it's active or not, its I/O base address and
24700 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24701 counts of various errors encountered so far.
24705 @node Cygwin Native
24706 @subsection Features for Debugging MS Windows PE Executables
24707 @cindex MS Windows debugging
24708 @cindex native Cygwin debugging
24709 @cindex Cygwin-specific commands
24711 @value{GDBN} supports native debugging of MS Windows programs, including
24712 DLLs with and without symbolic debugging information.
24714 @cindex Ctrl-BREAK, MS-Windows
24715 @cindex interrupt debuggee on MS-Windows
24716 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24717 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24718 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24719 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24720 sequence, which can be used to interrupt the debuggee even if it
24723 There are various additional Cygwin-specific commands, described in
24724 this section. Working with DLLs that have no debugging symbols is
24725 described in @ref{Non-debug DLL Symbols}.
24730 This is a prefix of MS Windows-specific commands which print
24731 information about the target system and important OS structures.
24733 @item info w32 selector
24734 This command displays information returned by
24735 the Win32 API @code{GetThreadSelectorEntry} function.
24736 It takes an optional argument that is evaluated to
24737 a long value to give the information about this given selector.
24738 Without argument, this command displays information
24739 about the six segment registers.
24741 @item info w32 thread-information-block
24742 This command displays thread specific information stored in the
24743 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24744 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24746 @kindex signal-event
24747 @item signal-event @var{id}
24748 This command signals an event with user-provided @var{id}. Used to resume
24749 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24751 To use it, create or edit the following keys in
24752 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24753 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24754 (for x86_64 versions):
24758 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24759 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24760 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24762 The first @code{%ld} will be replaced by the process ID of the
24763 crashing process, the second @code{%ld} will be replaced by the ID of
24764 the event that blocks the crashing process, waiting for @value{GDBN}
24768 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24769 make the system run debugger specified by the Debugger key
24770 automatically, @code{0} will cause a dialog box with ``OK'' and
24771 ``Cancel'' buttons to appear, which allows the user to either
24772 terminate the crashing process (OK) or debug it (Cancel).
24775 @kindex set cygwin-exceptions
24776 @cindex debugging the Cygwin DLL
24777 @cindex Cygwin DLL, debugging
24778 @item set cygwin-exceptions @var{mode}
24779 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24780 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24781 @value{GDBN} will delay recognition of exceptions, and may ignore some
24782 exceptions which seem to be caused by internal Cygwin DLL
24783 ``bookkeeping''. This option is meant primarily for debugging the
24784 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24785 @value{GDBN} users with false @code{SIGSEGV} signals.
24787 @kindex show cygwin-exceptions
24788 @item show cygwin-exceptions
24789 Displays whether @value{GDBN} will break on exceptions that happen
24790 inside the Cygwin DLL itself.
24792 @kindex set new-console
24793 @item set new-console @var{mode}
24794 If @var{mode} is @code{on} the debuggee will
24795 be started in a new console on next start.
24796 If @var{mode} is @code{off}, the debuggee will
24797 be started in the same console as the debugger.
24799 @kindex show new-console
24800 @item show new-console
24801 Displays whether a new console is used
24802 when the debuggee is started.
24804 @kindex set new-group
24805 @item set new-group @var{mode}
24806 This boolean value controls whether the debuggee should
24807 start a new group or stay in the same group as the debugger.
24808 This affects the way the Windows OS handles
24811 @kindex show new-group
24812 @item show new-group
24813 Displays current value of new-group boolean.
24815 @kindex set debugevents
24816 @item set debugevents
24817 This boolean value adds debug output concerning kernel events related
24818 to the debuggee seen by the debugger. This includes events that
24819 signal thread and process creation and exit, DLL loading and
24820 unloading, console interrupts, and debugging messages produced by the
24821 Windows @code{OutputDebugString} API call.
24823 @kindex set debugexec
24824 @item set debugexec
24825 This boolean value adds debug output concerning execute events
24826 (such as resume thread) seen by the debugger.
24828 @kindex set debugexceptions
24829 @item set debugexceptions
24830 This boolean value adds debug output concerning exceptions in the
24831 debuggee seen by the debugger.
24833 @kindex set debugmemory
24834 @item set debugmemory
24835 This boolean value adds debug output concerning debuggee memory reads
24836 and writes by the debugger.
24840 This boolean values specifies whether the debuggee is called
24841 via a shell or directly (default value is on).
24845 Displays if the debuggee will be started with a shell.
24850 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24853 @node Non-debug DLL Symbols
24854 @subsubsection Support for DLLs without Debugging Symbols
24855 @cindex DLLs with no debugging symbols
24856 @cindex Minimal symbols and DLLs
24858 Very often on windows, some of the DLLs that your program relies on do
24859 not include symbolic debugging information (for example,
24860 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24861 symbols in a DLL, it relies on the minimal amount of symbolic
24862 information contained in the DLL's export table. This section
24863 describes working with such symbols, known internally to @value{GDBN} as
24864 ``minimal symbols''.
24866 Note that before the debugged program has started execution, no DLLs
24867 will have been loaded. The easiest way around this problem is simply to
24868 start the program --- either by setting a breakpoint or letting the
24869 program run once to completion.
24871 @subsubsection DLL Name Prefixes
24873 In keeping with the naming conventions used by the Microsoft debugging
24874 tools, DLL export symbols are made available with a prefix based on the
24875 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24876 also entered into the symbol table, so @code{CreateFileA} is often
24877 sufficient. In some cases there will be name clashes within a program
24878 (particularly if the executable itself includes full debugging symbols)
24879 necessitating the use of the fully qualified name when referring to the
24880 contents of the DLL. Use single-quotes around the name to avoid the
24881 exclamation mark (``!'') being interpreted as a language operator.
24883 Note that the internal name of the DLL may be all upper-case, even
24884 though the file name of the DLL is lower-case, or vice-versa. Since
24885 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24886 some confusion. If in doubt, try the @code{info functions} and
24887 @code{info variables} commands or even @code{maint print msymbols}
24888 (@pxref{Symbols}). Here's an example:
24891 (@value{GDBP}) info function CreateFileA
24892 All functions matching regular expression "CreateFileA":
24894 Non-debugging symbols:
24895 0x77e885f4 CreateFileA
24896 0x77e885f4 KERNEL32!CreateFileA
24900 (@value{GDBP}) info function !
24901 All functions matching regular expression "!":
24903 Non-debugging symbols:
24904 0x6100114c cygwin1!__assert
24905 0x61004034 cygwin1!_dll_crt0@@0
24906 0x61004240 cygwin1!dll_crt0(per_process *)
24910 @subsubsection Working with Minimal Symbols
24912 Symbols extracted from a DLL's export table do not contain very much
24913 type information. All that @value{GDBN} can do is guess whether a symbol
24914 refers to a function or variable depending on the linker section that
24915 contains the symbol. Also note that the actual contents of the memory
24916 contained in a DLL are not available unless the program is running. This
24917 means that you cannot examine the contents of a variable or disassemble
24918 a function within a DLL without a running program.
24920 Variables are generally treated as pointers and dereferenced
24921 automatically. For this reason, it is often necessary to prefix a
24922 variable name with the address-of operator (``&'') and provide explicit
24923 type information in the command. Here's an example of the type of
24927 (@value{GDBP}) print 'cygwin1!__argv'
24928 'cygwin1!__argv' has unknown type; cast it to its declared type
24932 (@value{GDBP}) x 'cygwin1!__argv'
24933 'cygwin1!__argv' has unknown type; cast it to its declared type
24936 And two possible solutions:
24939 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24940 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24944 (@value{GDBP}) x/2x &'cygwin1!__argv'
24945 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24946 (@value{GDBP}) x/x 0x10021608
24947 0x10021608: 0x0022fd98
24948 (@value{GDBP}) x/s 0x0022fd98
24949 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24952 Setting a break point within a DLL is possible even before the program
24953 starts execution. However, under these circumstances, @value{GDBN} can't
24954 examine the initial instructions of the function in order to skip the
24955 function's frame set-up code. You can work around this by using ``*&''
24956 to set the breakpoint at a raw memory address:
24959 (@value{GDBP}) break *&'python22!PyOS_Readline'
24960 Breakpoint 1 at 0x1e04eff0
24963 The author of these extensions is not entirely convinced that setting a
24964 break point within a shared DLL like @file{kernel32.dll} is completely
24968 @subsection Commands Specific to @sc{gnu} Hurd Systems
24969 @cindex @sc{gnu} Hurd debugging
24971 This subsection describes @value{GDBN} commands specific to the
24972 @sc{gnu} Hurd native debugging.
24977 @kindex set signals@r{, Hurd command}
24978 @kindex set sigs@r{, Hurd command}
24979 This command toggles the state of inferior signal interception by
24980 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24981 affected by this command. @code{sigs} is a shorthand alias for
24986 @kindex show signals@r{, Hurd command}
24987 @kindex show sigs@r{, Hurd command}
24988 Show the current state of intercepting inferior's signals.
24990 @item set signal-thread
24991 @itemx set sigthread
24992 @kindex set signal-thread
24993 @kindex set sigthread
24994 This command tells @value{GDBN} which thread is the @code{libc} signal
24995 thread. That thread is run when a signal is delivered to a running
24996 process. @code{set sigthread} is the shorthand alias of @code{set
24999 @item show signal-thread
25000 @itemx show sigthread
25001 @kindex show signal-thread
25002 @kindex show sigthread
25003 These two commands show which thread will run when the inferior is
25004 delivered a signal.
25007 @kindex set stopped@r{, Hurd command}
25008 This commands tells @value{GDBN} that the inferior process is stopped,
25009 as with the @code{SIGSTOP} signal. The stopped process can be
25010 continued by delivering a signal to it.
25013 @kindex show stopped@r{, Hurd command}
25014 This command shows whether @value{GDBN} thinks the debuggee is
25017 @item set exceptions
25018 @kindex set exceptions@r{, Hurd command}
25019 Use this command to turn off trapping of exceptions in the inferior.
25020 When exception trapping is off, neither breakpoints nor
25021 single-stepping will work. To restore the default, set exception
25024 @item show exceptions
25025 @kindex show exceptions@r{, Hurd command}
25026 Show the current state of trapping exceptions in the inferior.
25028 @item set task pause
25029 @kindex set task@r{, Hurd commands}
25030 @cindex task attributes (@sc{gnu} Hurd)
25031 @cindex pause current task (@sc{gnu} Hurd)
25032 This command toggles task suspension when @value{GDBN} has control.
25033 Setting it to on takes effect immediately, and the task is suspended
25034 whenever @value{GDBN} gets control. Setting it to off will take
25035 effect the next time the inferior is continued. If this option is set
25036 to off, you can use @code{set thread default pause on} or @code{set
25037 thread pause on} (see below) to pause individual threads.
25039 @item show task pause
25040 @kindex show task@r{, Hurd commands}
25041 Show the current state of task suspension.
25043 @item set task detach-suspend-count
25044 @cindex task suspend count
25045 @cindex detach from task, @sc{gnu} Hurd
25046 This command sets the suspend count the task will be left with when
25047 @value{GDBN} detaches from it.
25049 @item show task detach-suspend-count
25050 Show the suspend count the task will be left with when detaching.
25052 @item set task exception-port
25053 @itemx set task excp
25054 @cindex task exception port, @sc{gnu} Hurd
25055 This command sets the task exception port to which @value{GDBN} will
25056 forward exceptions. The argument should be the value of the @dfn{send
25057 rights} of the task. @code{set task excp} is a shorthand alias.
25059 @item set noninvasive
25060 @cindex noninvasive task options
25061 This command switches @value{GDBN} to a mode that is the least
25062 invasive as far as interfering with the inferior is concerned. This
25063 is the same as using @code{set task pause}, @code{set exceptions}, and
25064 @code{set signals} to values opposite to the defaults.
25066 @item info send-rights
25067 @itemx info receive-rights
25068 @itemx info port-rights
25069 @itemx info port-sets
25070 @itemx info dead-names
25073 @cindex send rights, @sc{gnu} Hurd
25074 @cindex receive rights, @sc{gnu} Hurd
25075 @cindex port rights, @sc{gnu} Hurd
25076 @cindex port sets, @sc{gnu} Hurd
25077 @cindex dead names, @sc{gnu} Hurd
25078 These commands display information about, respectively, send rights,
25079 receive rights, port rights, port sets, and dead names of a task.
25080 There are also shorthand aliases: @code{info ports} for @code{info
25081 port-rights} and @code{info psets} for @code{info port-sets}.
25083 @item set thread pause
25084 @kindex set thread@r{, Hurd command}
25085 @cindex thread properties, @sc{gnu} Hurd
25086 @cindex pause current thread (@sc{gnu} Hurd)
25087 This command toggles current thread suspension when @value{GDBN} has
25088 control. Setting it to on takes effect immediately, and the current
25089 thread is suspended whenever @value{GDBN} gets control. Setting it to
25090 off will take effect the next time the inferior is continued.
25091 Normally, this command has no effect, since when @value{GDBN} has
25092 control, the whole task is suspended. However, if you used @code{set
25093 task pause off} (see above), this command comes in handy to suspend
25094 only the current thread.
25096 @item show thread pause
25097 @kindex show thread@r{, Hurd command}
25098 This command shows the state of current thread suspension.
25100 @item set thread run
25101 This command sets whether the current thread is allowed to run.
25103 @item show thread run
25104 Show whether the current thread is allowed to run.
25106 @item set thread detach-suspend-count
25107 @cindex thread suspend count, @sc{gnu} Hurd
25108 @cindex detach from thread, @sc{gnu} Hurd
25109 This command sets the suspend count @value{GDBN} will leave on a
25110 thread when detaching. This number is relative to the suspend count
25111 found by @value{GDBN} when it notices the thread; use @code{set thread
25112 takeover-suspend-count} to force it to an absolute value.
25114 @item show thread detach-suspend-count
25115 Show the suspend count @value{GDBN} will leave on the thread when
25118 @item set thread exception-port
25119 @itemx set thread excp
25120 Set the thread exception port to which to forward exceptions. This
25121 overrides the port set by @code{set task exception-port} (see above).
25122 @code{set thread excp} is the shorthand alias.
25124 @item set thread takeover-suspend-count
25125 Normally, @value{GDBN}'s thread suspend counts are relative to the
25126 value @value{GDBN} finds when it notices each thread. This command
25127 changes the suspend counts to be absolute instead.
25129 @item set thread default
25130 @itemx show thread default
25131 @cindex thread default settings, @sc{gnu} Hurd
25132 Each of the above @code{set thread} commands has a @code{set thread
25133 default} counterpart (e.g., @code{set thread default pause}, @code{set
25134 thread default exception-port}, etc.). The @code{thread default}
25135 variety of commands sets the default thread properties for all
25136 threads; you can then change the properties of individual threads with
25137 the non-default commands.
25144 @value{GDBN} provides the following commands specific to the Darwin target:
25147 @item set debug darwin @var{num}
25148 @kindex set debug darwin
25149 When set to a non zero value, enables debugging messages specific to
25150 the Darwin support. Higher values produce more verbose output.
25152 @item show debug darwin
25153 @kindex show debug darwin
25154 Show the current state of Darwin messages.
25156 @item set debug mach-o @var{num}
25157 @kindex set debug mach-o
25158 When set to a non zero value, enables debugging messages while
25159 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25160 file format used on Darwin for object and executable files.) Higher
25161 values produce more verbose output. This is a command to diagnose
25162 problems internal to @value{GDBN} and should not be needed in normal
25165 @item show debug mach-o
25166 @kindex show debug mach-o
25167 Show the current state of Mach-O file messages.
25169 @item set mach-exceptions on
25170 @itemx set mach-exceptions off
25171 @kindex set mach-exceptions
25172 On Darwin, faults are first reported as a Mach exception and are then
25173 mapped to a Posix signal. Use this command to turn on trapping of
25174 Mach exceptions in the inferior. This might be sometimes useful to
25175 better understand the cause of a fault. The default is off.
25177 @item show mach-exceptions
25178 @kindex show mach-exceptions
25179 Show the current state of exceptions trapping.
25183 @subsection FreeBSD
25186 When the ABI of a system call is changed in the FreeBSD kernel, this
25187 is implemented by leaving a compatibility system call using the old
25188 ABI at the existing number and allocating a new system call number for
25189 the version using the new ABI. As a convenience, when a system call
25190 is caught by name (@pxref{catch syscall}), compatibility system calls
25193 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25194 system call and catching the @code{kevent} system call by name catches
25198 (@value{GDBP}) catch syscall kevent
25199 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25205 @section Embedded Operating Systems
25207 This section describes configurations involving the debugging of
25208 embedded operating systems that are available for several different
25211 @value{GDBN} includes the ability to debug programs running on
25212 various real-time operating systems.
25214 @node Embedded Processors
25215 @section Embedded Processors
25217 This section goes into details specific to particular embedded
25220 @cindex send command to simulator
25221 Whenever a specific embedded processor has a simulator, @value{GDBN}
25222 allows to send an arbitrary command to the simulator.
25225 @item sim @var{command}
25226 @kindex sim@r{, a command}
25227 Send an arbitrary @var{command} string to the simulator. Consult the
25228 documentation for the specific simulator in use for information about
25229 acceptable commands.
25234 * ARC:: Synopsys ARC
25237 * M68K:: Motorola M68K
25238 * MicroBlaze:: Xilinx MicroBlaze
25239 * MIPS Embedded:: MIPS Embedded
25240 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25241 * PowerPC Embedded:: PowerPC Embedded
25244 * Super-H:: Renesas Super-H
25248 @subsection Synopsys ARC
25249 @cindex Synopsys ARC
25250 @cindex ARC specific commands
25256 @value{GDBN} provides the following ARC-specific commands:
25259 @item set debug arc
25260 @kindex set debug arc
25261 Control the level of ARC specific debug messages. Use 0 for no messages (the
25262 default), 1 for debug messages, and 2 for even more debug messages.
25264 @item show debug arc
25265 @kindex show debug arc
25266 Show the level of ARC specific debugging in operation.
25268 @item maint print arc arc-instruction @var{address}
25269 @kindex maint print arc arc-instruction
25270 Print internal disassembler information about instruction at a given address.
25277 @value{GDBN} provides the following ARM-specific commands:
25280 @item set arm disassembler
25282 This commands selects from a list of disassembly styles. The
25283 @code{"std"} style is the standard style.
25285 @item show arm disassembler
25287 Show the current disassembly style.
25289 @item set arm apcs32
25290 @cindex ARM 32-bit mode
25291 This command toggles ARM operation mode between 32-bit and 26-bit.
25293 @item show arm apcs32
25294 Display the current usage of the ARM 32-bit mode.
25296 @item set arm fpu @var{fputype}
25297 This command sets the ARM floating-point unit (FPU) type. The
25298 argument @var{fputype} can be one of these:
25302 Determine the FPU type by querying the OS ABI.
25304 Software FPU, with mixed-endian doubles on little-endian ARM
25307 GCC-compiled FPA co-processor.
25309 Software FPU with pure-endian doubles.
25315 Show the current type of the FPU.
25318 This command forces @value{GDBN} to use the specified ABI.
25321 Show the currently used ABI.
25323 @item set arm fallback-mode (arm|thumb|auto)
25324 @value{GDBN} uses the symbol table, when available, to determine
25325 whether instructions are ARM or Thumb. This command controls
25326 @value{GDBN}'s default behavior when the symbol table is not
25327 available. The default is @samp{auto}, which causes @value{GDBN} to
25328 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25331 @item show arm fallback-mode
25332 Show the current fallback instruction mode.
25334 @item set arm force-mode (arm|thumb|auto)
25335 This command overrides use of the symbol table to determine whether
25336 instructions are ARM or Thumb. The default is @samp{auto}, which
25337 causes @value{GDBN} to use the symbol table and then the setting
25338 of @samp{set arm fallback-mode}.
25340 @item show arm force-mode
25341 Show the current forced instruction mode.
25343 @item set arm unwind-secure-frames
25344 This command enables unwinding from Non-secure to Secure mode on
25345 Cortex-M with Security extension.
25346 This can trigger security exceptions when unwinding the exception
25348 It is enabled by default.
25350 @item show arm unwind-secure-frames
25351 Show whether unwinding from Non-secure to Secure mode is enabled.
25353 @item set debug arm
25354 Toggle whether to display ARM-specific debugging messages from the ARM
25355 target support subsystem.
25357 @item show debug arm
25358 Show whether ARM-specific debugging messages are enabled.
25362 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25363 The @value{GDBN} ARM simulator accepts the following optional arguments.
25366 @item --swi-support=@var{type}
25367 Tell the simulator which SWI interfaces to support. The argument
25368 @var{type} may be a comma separated list of the following values.
25369 The default value is @code{all}.
25385 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25386 The @value{GDBN} BPF simulator accepts the following optional arguments.
25389 @item --skb-data-offset=@var{offset}
25390 Tell the simulator the offset, measured in bytes, of the
25391 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25392 This offset is used by some BPF specific-purpose load/store
25393 instructions. Defaults to 0.
25400 The Motorola m68k configuration includes ColdFire support.
25403 @subsection MicroBlaze
25404 @cindex Xilinx MicroBlaze
25405 @cindex XMD, Xilinx Microprocessor Debugger
25407 The MicroBlaze is a soft-core processor supported on various Xilinx
25408 FPGAs, such as Spartan or Virtex series. Boards with these processors
25409 usually have JTAG ports which connect to a host system running the Xilinx
25410 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25411 This host system is used to download the configuration bitstream to
25412 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25413 communicates with the target board using the JTAG interface and
25414 presents a @code{gdbserver} interface to the board. By default
25415 @code{xmd} uses port @code{1234}. (While it is possible to change
25416 this default port, it requires the use of undocumented @code{xmd}
25417 commands. Contact Xilinx support if you need to do this.)
25419 Use these GDB commands to connect to the MicroBlaze target processor.
25422 @item target remote :1234
25423 Use this command to connect to the target if you are running @value{GDBN}
25424 on the same system as @code{xmd}.
25426 @item target remote @var{xmd-host}:1234
25427 Use this command to connect to the target if it is connected to @code{xmd}
25428 running on a different system named @var{xmd-host}.
25431 Use this command to download a program to the MicroBlaze target.
25433 @item set debug microblaze @var{n}
25434 Enable MicroBlaze-specific debugging messages if non-zero.
25436 @item show debug microblaze @var{n}
25437 Show MicroBlaze-specific debugging level.
25440 @node MIPS Embedded
25441 @subsection @acronym{MIPS} Embedded
25444 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25447 @item set mipsfpu double
25448 @itemx set mipsfpu single
25449 @itemx set mipsfpu none
25450 @itemx set mipsfpu auto
25451 @itemx show mipsfpu
25452 @kindex set mipsfpu
25453 @kindex show mipsfpu
25454 @cindex @acronym{MIPS} remote floating point
25455 @cindex floating point, @acronym{MIPS} remote
25456 If your target board does not support the @acronym{MIPS} floating point
25457 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25458 need this, you may wish to put the command in your @value{GDBN} init
25459 file). This tells @value{GDBN} how to find the return value of
25460 functions which return floating point values. It also allows
25461 @value{GDBN} to avoid saving the floating point registers when calling
25462 functions on the board. If you are using a floating point coprocessor
25463 with only single precision floating point support, as on the @sc{r4650}
25464 processor, use the command @samp{set mipsfpu single}. The default
25465 double precision floating point coprocessor may be selected using
25466 @samp{set mipsfpu double}.
25468 In previous versions the only choices were double precision or no
25469 floating point, so @samp{set mipsfpu on} will select double precision
25470 and @samp{set mipsfpu off} will select no floating point.
25472 As usual, you can inquire about the @code{mipsfpu} variable with
25473 @samp{show mipsfpu}.
25476 @node OpenRISC 1000
25477 @subsection OpenRISC 1000
25478 @cindex OpenRISC 1000
25481 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25482 mainly provided as a soft-core which can run on Xilinx, Altera and other
25485 @value{GDBN} for OpenRISC supports the below commands when connecting to
25493 Runs the builtin CPU simulator which can run very basic
25494 programs but does not support most hardware functions like MMU.
25495 For more complex use cases the user is advised to run an external
25496 target, and connect using @samp{target remote}.
25498 Example: @code{target sim}
25500 @item set debug or1k
25501 Toggle whether to display OpenRISC-specific debugging messages from the
25502 OpenRISC target support subsystem.
25504 @item show debug or1k
25505 Show whether OpenRISC-specific debugging messages are enabled.
25508 @node PowerPC Embedded
25509 @subsection PowerPC Embedded
25511 @cindex DVC register
25512 @value{GDBN} supports using the DVC (Data Value Compare) register to
25513 implement in hardware simple hardware watchpoint conditions of the form:
25516 (@value{GDBP}) watch @var{address|variable} \
25517 if @var{address|variable} == @var{constant expression}
25520 The DVC register will be automatically used when @value{GDBN} detects
25521 such pattern in a condition expression, and the created watchpoint uses one
25522 debug register (either the @code{exact-watchpoints} option is on and the
25523 variable is scalar, or the variable has a length of one byte). This feature
25524 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25527 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25528 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25529 in which case watchpoints using only one debug register are created when
25530 watching variables of scalar types.
25532 You can create an artificial array to watch an arbitrary memory
25533 region using one of the following commands (@pxref{Expressions}):
25536 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25537 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25540 PowerPC embedded processors support masked watchpoints. See the discussion
25541 about the @code{mask} argument in @ref{Set Watchpoints}.
25543 @cindex ranged breakpoint
25544 PowerPC embedded processors support hardware accelerated
25545 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25546 the inferior whenever it executes an instruction at any address within
25547 the range it was set at. To set a ranged breakpoint in @value{GDBN},
25548 use the @code{break-range} command.
25550 @value{GDBN} provides the following PowerPC-specific commands:
25553 @kindex break-range
25554 @item break-range @var{start-locspec}, @var{end-locspec}
25555 Set a breakpoint for an address range given by @var{start-locspec} and
25556 @var{end-locspec}, which are location specs. @xref{Location
25557 Specifications}, for a list of all the possible forms of location
25558 specs. @value{GDBN} resolves both @var{start-locspec} and
25559 @var{end-locspec}, and uses the addresses of the resolved code
25560 locations as start and end addresses of the range to break at. The
25561 breakpoint will stop execution of the inferior whenever it executes an
25562 instruction at any address between the start and end addresses,
25563 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
25564 to multiple code locations in the program, then the command aborts
25565 with an error without creating a breakpoint.
25567 @kindex set powerpc
25568 @item set powerpc soft-float
25569 @itemx show powerpc soft-float
25570 Force @value{GDBN} to use (or not use) a software floating point calling
25571 convention. By default, @value{GDBN} selects the calling convention based
25572 on the selected architecture and the provided executable file.
25574 @item set powerpc vector-abi
25575 @itemx show powerpc vector-abi
25576 Force @value{GDBN} to use the specified calling convention for vector
25577 arguments and return values. The valid options are @samp{auto};
25578 @samp{generic}, to avoid vector registers even if they are present;
25579 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25580 registers. By default, @value{GDBN} selects the calling convention
25581 based on the selected architecture and the provided executable file.
25583 @item set powerpc exact-watchpoints
25584 @itemx show powerpc exact-watchpoints
25585 Allow @value{GDBN} to use only one debug register when watching a variable
25586 of scalar type, thus assuming that the variable is accessed through the
25587 address of its first byte.
25592 @subsection Atmel AVR
25595 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25596 following AVR-specific commands:
25599 @item info io_registers
25600 @kindex info io_registers@r{, AVR}
25601 @cindex I/O registers (Atmel AVR)
25602 This command displays information about the AVR I/O registers. For
25603 each register, @value{GDBN} prints its number and value.
25610 When configured for debugging CRIS, @value{GDBN} provides the
25611 following CRIS-specific commands:
25614 @item set cris-version @var{ver}
25615 @cindex CRIS version
25616 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25617 The CRIS version affects register names and sizes. This command is useful in
25618 case autodetection of the CRIS version fails.
25620 @item show cris-version
25621 Show the current CRIS version.
25623 @item set cris-dwarf2-cfi
25624 @cindex DWARF-2 CFI and CRIS
25625 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25626 Change to @samp{off} when using @code{gcc-cris} whose version is below
25629 @item show cris-dwarf2-cfi
25630 Show the current state of using DWARF-2 CFI.
25632 @item set cris-mode @var{mode}
25634 Set the current CRIS mode to @var{mode}. It should only be changed when
25635 debugging in guru mode, in which case it should be set to
25636 @samp{guru} (the default is @samp{normal}).
25638 @item show cris-mode
25639 Show the current CRIS mode.
25643 @subsection Renesas Super-H
25646 For the Renesas Super-H processor, @value{GDBN} provides these
25650 @item set sh calling-convention @var{convention}
25651 @kindex set sh calling-convention
25652 Set the calling-convention used when calling functions from @value{GDBN}.
25653 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25654 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25655 convention. If the DWARF-2 information of the called function specifies
25656 that the function follows the Renesas calling convention, the function
25657 is called using the Renesas calling convention. If the calling convention
25658 is set to @samp{renesas}, the Renesas calling convention is always used,
25659 regardless of the DWARF-2 information. This can be used to override the
25660 default of @samp{gcc} if debug information is missing, or the compiler
25661 does not emit the DWARF-2 calling convention entry for a function.
25663 @item show sh calling-convention
25664 @kindex show sh calling-convention
25665 Show the current calling convention setting.
25670 @node Architectures
25671 @section Architectures
25673 This section describes characteristics of architectures that affect
25674 all uses of @value{GDBN} with the architecture, both native and cross.
25681 * HPPA:: HP PA architecture
25689 @subsection AArch64
25690 @cindex AArch64 support
25692 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25693 following special commands:
25696 @item set debug aarch64
25697 @kindex set debug aarch64
25698 This command determines whether AArch64 architecture-specific debugging
25699 messages are to be displayed.
25701 @item show debug aarch64
25702 Show whether AArch64 debugging messages are displayed.
25706 @subsubsection AArch64 SVE.
25707 @cindex AArch64 SVE.
25709 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25710 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25711 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25712 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25713 @code{$vg} will be provided. This is the vector granule for the current thread
25714 and represents the number of 64-bit chunks in an SVE @code{z} register.
25716 If the vector length changes, then the @code{$vg} register will be updated,
25717 but the lengths of the @code{z} and @code{p} registers will not change. This
25718 is a known limitation of @value{GDBN} and does not affect the execution of the
25721 @subsubsection AArch64 Pointer Authentication.
25722 @cindex AArch64 Pointer Authentication.
25723 @anchor{AArch64 PAC}
25725 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25726 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25727 register @code{$lr} is pointing to an PAC function its value will be masked.
25728 When GDB prints a backtrace, any addresses that required unmasking will be
25729 postfixed with the marker [PAC]. When using the MI, this is printed as part
25730 of the @code{addr_flags} field.
25732 @subsubsection AArch64 Memory Tagging Extension.
25733 @cindex AArch64 Memory Tagging Extension.
25735 When @value{GDBN} is debugging the AArch64 architecture, the program is
25736 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25737 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25738 available for inspection and editing of logical and allocation tags.
25739 @xref{Memory Tagging}.
25741 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25742 signals are generated as a result of memory tag failures.
25744 If the tag violation is synchronous, the following will be shown:
25747 Program received signal SIGSEGV, Segmentation fault
25748 Memory tag violation while accessing address 0x0500fffff7ff8000
25753 If the tag violation is asynchronous, the fault address is not available.
25754 In this case @value{GDBN} will show the following:
25757 Program received signal SIGSEGV, Segmentation fault
25758 Memory tag violation
25759 Fault address unavailable.
25762 A special register, @code{tag_ctl}, is made available through the
25763 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25764 options that can be controlled at runtime and emulates the @code{prctl}
25765 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25766 documentation in the Linux kernel.
25769 @subsection x86 Architecture-specific Issues
25772 @item set struct-convention @var{mode}
25773 @kindex set struct-convention
25774 @cindex struct return convention
25775 @cindex struct/union returned in registers
25776 Set the convention used by the inferior to return @code{struct}s and
25777 @code{union}s from functions to @var{mode}. Possible values of
25778 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25779 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25780 are returned on the stack, while @code{"reg"} means that a
25781 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25782 be returned in a register.
25784 @item show struct-convention
25785 @kindex show struct-convention
25786 Show the current setting of the convention to return @code{struct}s
25791 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25792 @cindex Intel Memory Protection Extensions (MPX).
25794 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25795 @footnote{The register named with capital letters represent the architecture
25796 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25797 which are the lower bound and upper bound. Bounds are effective addresses or
25798 memory locations. The upper bounds are architecturally represented in 1's
25799 complement form. A bound having lower bound = 0, and upper bound = 0
25800 (1's complement of all bits set) will allow access to the entire address space.
25802 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25803 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25804 display the upper bound performing the complement of one operation on the
25805 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25806 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25807 can also be noted that the upper bounds are inclusive.
25809 As an example, assume that the register BND0 holds bounds for a pointer having
25810 access allowed for the range between 0x32 and 0x71. The values present on
25811 bnd0raw and bnd registers are presented as follows:
25814 bnd0raw = @{0x32, 0xffffffff8e@}
25815 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25818 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25819 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25820 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25821 Python, the display includes the memory size, in bits, accessible to
25824 Bounds can also be stored in bounds tables, which are stored in
25825 application memory. These tables store bounds for pointers by specifying
25826 the bounds pointer's value along with its bounds. Evaluating and changing
25827 bounds located in bound tables is therefore interesting while investigating
25828 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25831 @item show mpx bound @var{pointer}
25832 @kindex show mpx bound
25833 Display bounds of the given @var{pointer}.
25835 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25836 @kindex set mpx bound
25837 Set the bounds of a pointer in the bound table.
25838 This command takes three parameters: @var{pointer} is the pointers
25839 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25840 for lower and upper bounds respectively.
25843 When you call an inferior function on an Intel MPX enabled program,
25844 GDB sets the inferior's bound registers to the init (disabled) state
25845 before calling the function. As a consequence, bounds checks for the
25846 pointer arguments passed to the function will always pass.
25848 This is necessary because when you call an inferior function, the
25849 program is usually in the middle of the execution of other function.
25850 Since at that point bound registers are in an arbitrary state, not
25851 clearing them would lead to random bound violations in the called
25854 You can still examine the influence of the bound registers on the
25855 execution of the called function by stopping the execution of the
25856 called function at its prologue, setting bound registers, and
25857 continuing the execution. For example:
25861 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25862 $ print upper (a, b, c, d, 1)
25863 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25865 @{lbound = 0x0, ubound = ffffffff@} : size -1
25868 At this last step the value of bnd0 can be changed for investigation of bound
25869 violations caused along the execution of the call. In order to know how to
25870 set the bound registers or bound table for the call consult the ABI.
25875 See the following section.
25878 @subsection @acronym{MIPS}
25880 @cindex stack on Alpha
25881 @cindex stack on @acronym{MIPS}
25882 @cindex Alpha stack
25883 @cindex @acronym{MIPS} stack
25884 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25885 sometimes requires @value{GDBN} to search backward in the object code to
25886 find the beginning of a function.
25888 @cindex response time, @acronym{MIPS} debugging
25889 To improve response time (especially for embedded applications, where
25890 @value{GDBN} may be restricted to a slow serial line for this search)
25891 you may want to limit the size of this search, using one of these
25895 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25896 @item set heuristic-fence-post @var{limit}
25897 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25898 search for the beginning of a function. A value of @var{0} (the
25899 default) means there is no limit. However, except for @var{0}, the
25900 larger the limit the more bytes @code{heuristic-fence-post} must search
25901 and therefore the longer it takes to run. You should only need to use
25902 this command when debugging a stripped executable.
25904 @item show heuristic-fence-post
25905 Display the current limit.
25909 These commands are available @emph{only} when @value{GDBN} is configured
25910 for debugging programs on Alpha or @acronym{MIPS} processors.
25912 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25916 @item set mips abi @var{arg}
25917 @kindex set mips abi
25918 @cindex set ABI for @acronym{MIPS}
25919 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25920 values of @var{arg} are:
25924 The default ABI associated with the current binary (this is the
25934 @item show mips abi
25935 @kindex show mips abi
25936 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25938 @item set mips compression @var{arg}
25939 @kindex set mips compression
25940 @cindex code compression, @acronym{MIPS}
25941 Tell @value{GDBN} which @acronym{MIPS} compressed
25942 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25943 inferior. @value{GDBN} uses this for code disassembly and other
25944 internal interpretation purposes. This setting is only referred to
25945 when no executable has been associated with the debugging session or
25946 the executable does not provide information about the encoding it uses.
25947 Otherwise this setting is automatically updated from information
25948 provided by the executable.
25950 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25951 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25952 executables containing @acronym{MIPS16} code frequently are not
25953 identified as such.
25955 This setting is ``sticky''; that is, it retains its value across
25956 debugging sessions until reset either explicitly with this command or
25957 implicitly from an executable.
25959 The compiler and/or assembler typically add symbol table annotations to
25960 identify functions compiled for the @acronym{MIPS16} or
25961 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25962 are present, @value{GDBN} uses them in preference to the global
25963 compressed @acronym{ISA} encoding setting.
25965 @item show mips compression
25966 @kindex show mips compression
25967 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25968 @value{GDBN} to debug the inferior.
25971 @itemx show mipsfpu
25972 @xref{MIPS Embedded, set mipsfpu}.
25974 @item set mips mask-address @var{arg}
25975 @kindex set mips mask-address
25976 @cindex @acronym{MIPS} addresses, masking
25977 This command determines whether the most-significant 32 bits of 64-bit
25978 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25979 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25980 setting, which lets @value{GDBN} determine the correct value.
25982 @item show mips mask-address
25983 @kindex show mips mask-address
25984 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25987 @item set remote-mips64-transfers-32bit-regs
25988 @kindex set remote-mips64-transfers-32bit-regs
25989 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25990 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25991 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25992 and 64 bits for other registers, set this option to @samp{on}.
25994 @item show remote-mips64-transfers-32bit-regs
25995 @kindex show remote-mips64-transfers-32bit-regs
25996 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25998 @item set debug mips
25999 @kindex set debug mips
26000 This command turns on and off debugging messages for the @acronym{MIPS}-specific
26001 target code in @value{GDBN}.
26003 @item show debug mips
26004 @kindex show debug mips
26005 Show the current setting of @acronym{MIPS} debugging messages.
26011 @cindex HPPA support
26013 When @value{GDBN} is debugging the HP PA architecture, it provides the
26014 following special commands:
26017 @item set debug hppa
26018 @kindex set debug hppa
26019 This command determines whether HPPA architecture-specific debugging
26020 messages are to be displayed.
26022 @item show debug hppa
26023 Show whether HPPA debugging messages are displayed.
26025 @item maint print unwind @var{address}
26026 @kindex maint print unwind@r{, HPPA}
26027 This command displays the contents of the unwind table entry at the
26028 given @var{address}.
26034 @subsection PowerPC
26035 @cindex PowerPC architecture
26037 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26038 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26039 numbers stored in the floating point registers. These values must be stored
26040 in two consecutive registers, always starting at an even register like
26041 @code{f0} or @code{f2}.
26043 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26044 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26045 @code{f2} and @code{f3} for @code{$dl1} and so on.
26047 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26048 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26051 @subsection Nios II
26052 @cindex Nios II architecture
26054 When @value{GDBN} is debugging the Nios II architecture,
26055 it provides the following special commands:
26059 @item set debug nios2
26060 @kindex set debug nios2
26061 This command turns on and off debugging messages for the Nios II
26062 target code in @value{GDBN}.
26064 @item show debug nios2
26065 @kindex show debug nios2
26066 Show the current setting of Nios II debugging messages.
26070 @subsection Sparc64
26071 @cindex Sparc64 support
26072 @cindex Application Data Integrity
26073 @subsubsection ADI Support
26075 The M7 processor supports an Application Data Integrity (ADI) feature that
26076 detects invalid data accesses. When software allocates memory and enables
26077 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26078 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26079 the 4-bit version in every cacheline of that data. Hardware saves the latter
26080 in spare bits in the cache and memory hierarchy. On each load and store,
26081 the processor compares the upper 4 VA (virtual address) bits to the
26082 cacheline's version. If there is a mismatch, the processor generates a
26083 version mismatch trap which can be either precise or disrupting. The trap
26084 is an error condition which the kernel delivers to the process as a SIGSEGV
26087 Note that only 64-bit applications can use ADI and need to be built with
26090 Values of the ADI version tags, which are in granularity of a
26091 cacheline (64 bytes), can be viewed or modified.
26095 @kindex adi examine
26096 @item adi (examine | x) [ / @var{n} ] @var{addr}
26098 The @code{adi examine} command displays the value of one ADI version tag per
26101 @var{n} is a decimal integer specifying the number in bytes; the default
26102 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26103 block size, to display.
26105 @var{addr} is the address in user address space where you want @value{GDBN}
26106 to begin displaying the ADI version tags.
26108 Below is an example of displaying ADI versions of variable "shmaddr".
26111 (@value{GDBP}) adi x/100 shmaddr
26112 0xfff800010002c000: 0 0
26116 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26118 The @code{adi assign} command is used to assign new ADI version tag
26121 @var{n} is a decimal integer specifying the number in bytes;
26122 the default is 1. It specifies how much ADI version information, at the
26123 ratio of 1:ADI block size, to modify.
26125 @var{addr} is the address in user address space where you want @value{GDBN}
26126 to begin modifying the ADI version tags.
26128 @var{tag} is the new ADI version tag.
26130 For example, do the following to modify then verify ADI versions of
26131 variable "shmaddr":
26134 (@value{GDBP}) adi a/100 shmaddr = 7
26135 (@value{GDBP}) adi x/100 shmaddr
26136 0xfff800010002c000: 7 7
26143 @cindex S12Z support
26145 When @value{GDBN} is debugging the S12Z architecture,
26146 it provides the following special command:
26149 @item maint info bdccsr
26150 @kindex maint info bdccsr@r{, S12Z}
26151 This command displays the current value of the microprocessor's
26156 @node Controlling GDB
26157 @chapter Controlling @value{GDBN}
26159 You can alter the way @value{GDBN} interacts with you by using the
26160 @code{set} command. For commands controlling how @value{GDBN} displays
26161 data, see @ref{Print Settings, ,Print Settings}. Other settings are
26166 * Editing:: Command editing
26167 * Command History:: Command history
26168 * Screen Size:: Screen size
26169 * Output Styling:: Output styling
26170 * Numbers:: Numbers
26171 * ABI:: Configuring the current ABI
26172 * Auto-loading:: Automatically loading associated files
26173 * Messages/Warnings:: Optional warnings and messages
26174 * Debugging Output:: Optional messages about internal happenings
26175 * Other Misc Settings:: Other Miscellaneous Settings
26183 @value{GDBN} indicates its readiness to read a command by printing a string
26184 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
26185 can change the prompt string with the @code{set prompt} command. For
26186 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
26187 the prompt in one of the @value{GDBN} sessions so that you can always tell
26188 which one you are talking to.
26190 @emph{Note:} @code{set prompt} does not add a space for you after the
26191 prompt you set. This allows you to set a prompt which ends in a space
26192 or a prompt that does not.
26196 @item set prompt @var{newprompt}
26197 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
26199 @kindex show prompt
26201 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
26204 Versions of @value{GDBN} that ship with Python scripting enabled have
26205 prompt extensions. The commands for interacting with these extensions
26209 @kindex set extended-prompt
26210 @item set extended-prompt @var{prompt}
26211 Set an extended prompt that allows for substitutions.
26212 @xref{gdb.prompt}, for a list of escape sequences that can be used for
26213 substitution. Any escape sequences specified as part of the prompt
26214 string are replaced with the corresponding strings each time the prompt
26220 set extended-prompt Current working directory: \w (gdb)
26223 Note that when an extended-prompt is set, it takes control of the
26224 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26226 @kindex show extended-prompt
26227 @item show extended-prompt
26228 Prints the extended prompt. Any escape sequences specified as part of
26229 the prompt string with @code{set extended-prompt}, are replaced with the
26230 corresponding strings each time the prompt is displayed.
26234 @section Command Editing
26236 @cindex command line editing
26238 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26239 @sc{gnu} library provides consistent behavior for programs which provide a
26240 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26241 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26242 substitution, and a storage and recall of command history across
26243 debugging sessions.
26245 You may control the behavior of command line editing in @value{GDBN} with the
26246 command @code{set}.
26249 @kindex set editing
26252 @itemx set editing on
26253 Enable command line editing (enabled by default).
26255 @item set editing off
26256 Disable command line editing.
26258 @kindex show editing
26260 Show whether command line editing is enabled.
26263 @ifset SYSTEM_READLINE
26264 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26266 @ifclear SYSTEM_READLINE
26267 @xref{Command Line Editing},
26269 for more details about the Readline
26270 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26271 encouraged to read that chapter.
26273 @cindex Readline application name
26274 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26275 is useful for conditions in @file{.inputrc}.
26277 @cindex operate-and-get-next
26278 @value{GDBN} defines a bindable Readline command,
26279 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26280 This command accepts the current line for execution and fetches the
26281 next line relative to the current line from the history for editing.
26282 Any argument is ignored.
26284 @node Command History
26285 @section Command History
26286 @cindex command history
26288 @value{GDBN} can keep track of the commands you type during your
26289 debugging sessions, so that you can be certain of precisely what
26290 happened. Use these commands to manage the @value{GDBN} command
26293 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26294 package, to provide the history facility.
26295 @ifset SYSTEM_READLINE
26296 @xref{Using History Interactively, , , history, GNU History Library},
26298 @ifclear SYSTEM_READLINE
26299 @xref{Using History Interactively},
26301 for the detailed description of the History library.
26303 To issue a command to @value{GDBN} without affecting certain aspects of
26304 the state which is seen by users, prefix it with @samp{server }
26305 (@pxref{Server Prefix}). This
26306 means that this command will not affect the command history, nor will it
26307 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26308 pressed on a line by itself.
26310 @cindex @code{server}, command prefix
26311 The server prefix does not affect the recording of values into the value
26312 history; to print a value without recording it into the value history,
26313 use the @code{output} command instead of the @code{print} command.
26315 Here is the description of @value{GDBN} commands related to command
26319 @cindex history substitution
26320 @cindex history file
26321 @kindex set history filename
26322 @cindex @env{GDBHISTFILE}, environment variable
26323 @item set history filename @r{[}@var{fname}@r{]}
26324 Set the name of the @value{GDBN} command history file to @var{fname}.
26325 This is the file where @value{GDBN} reads an initial command history
26326 list, and where it writes the command history from this session when it
26327 exits. You can access this list through history expansion or through
26328 the history command editing characters listed below. This file defaults
26329 to the value of the environment variable @env{GDBHISTFILE}, or to
26330 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26333 The @env{GDBHISTFILE} environment variable is read after processing
26334 any @value{GDBN} initialization files (@pxref{Startup}) and after
26335 processing any commands passed using command line options (for
26336 example, @code{-ex}).
26338 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26339 is the empty string then @value{GDBN} will neither try to load an
26340 existing history file, nor will it try to save the history on exit.
26342 @cindex save command history
26343 @kindex set history save
26344 @item set history save
26345 @itemx set history save on
26346 Record command history in a file, whose name may be specified with the
26347 @code{set history filename} command. By default, this option is
26348 disabled. The command history will be recorded when @value{GDBN}
26349 exits. If @code{set history filename} is set to the empty string then
26350 history saving is disabled, even when @code{set history save} is
26353 @item set history save off
26354 Don't record the command history into the file specified by @code{set
26355 history filename} when @value{GDBN} exits.
26357 @cindex history size
26358 @kindex set history size
26359 @cindex @env{GDBHISTSIZE}, environment variable
26360 @item set history size @var{size}
26361 @itemx set history size unlimited
26362 Set the number of commands which @value{GDBN} keeps in its history list.
26363 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26364 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26365 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26366 either a negative number or the empty string, then the number of commands
26367 @value{GDBN} keeps in the history list is unlimited.
26369 The @env{GDBHISTSIZE} environment variable is read after processing
26370 any @value{GDBN} initialization files (@pxref{Startup}) and after
26371 processing any commands passed using command line options (for
26372 example, @code{-ex}).
26374 @cindex remove duplicate history
26375 @kindex set history remove-duplicates
26376 @item set history remove-duplicates @var{count}
26377 @itemx set history remove-duplicates unlimited
26378 Control the removal of duplicate history entries in the command history list.
26379 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26380 history entries and remove the first entry that is a duplicate of the current
26381 entry being added to the command history list. If @var{count} is
26382 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26383 removal of duplicate history entries is disabled.
26385 Only history entries added during the current session are considered for
26386 removal. This option is set to 0 by default.
26390 History expansion assigns special meaning to the character @kbd{!}.
26391 @ifset SYSTEM_READLINE
26392 @xref{Event Designators, , , history, GNU History Library},
26394 @ifclear SYSTEM_READLINE
26395 @xref{Event Designators},
26399 @cindex history expansion, turn on/off
26400 Since @kbd{!} is also the logical not operator in C, history expansion
26401 is off by default. If you decide to enable history expansion with the
26402 @code{set history expansion on} command, you may sometimes need to
26403 follow @kbd{!} (when it is used as logical not, in an expression) with
26404 a space or a tab to prevent it from being expanded. The readline
26405 history facilities do not attempt substitution on the strings
26406 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26408 The commands to control history expansion are:
26411 @item set history expansion on
26412 @itemx set history expansion
26413 @kindex set history expansion
26414 Enable history expansion. History expansion is off by default.
26416 @item set history expansion off
26417 Disable history expansion.
26420 @kindex show history
26422 @itemx show history filename
26423 @itemx show history save
26424 @itemx show history size
26425 @itemx show history expansion
26426 These commands display the state of the @value{GDBN} history parameters.
26427 @code{show history} by itself displays all four states.
26432 @kindex show commands
26433 @cindex show last commands
26434 @cindex display command history
26435 @item show commands
26436 Display the last ten commands in the command history.
26438 @item show commands @var{n}
26439 Print ten commands centered on command number @var{n}.
26441 @item show commands +
26442 Print ten commands just after the commands last printed.
26446 @section Screen Size
26447 @cindex size of screen
26448 @cindex screen size
26451 @cindex pauses in output
26453 Certain commands to @value{GDBN} may produce large amounts of
26454 information output to the screen. To help you read all of it,
26455 @value{GDBN} pauses and asks you for input at the end of each page of
26456 output. Type @key{RET} when you want to see one more page of output,
26457 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26458 without paging for the rest of the current command. Also, the screen
26459 width setting determines when to wrap lines of output. Depending on
26460 what is being printed, @value{GDBN} tries to break the line at a
26461 readable place, rather than simply letting it overflow onto the
26464 Normally @value{GDBN} knows the size of the screen from the terminal
26465 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26466 together with the value of the @env{TERM} environment variable and the
26467 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26468 you can override it with the @code{set height} and @code{set
26475 @kindex show height
26476 @item set height @var{lpp}
26477 @itemx set height unlimited
26479 @itemx set width @var{cpl}
26480 @itemx set width unlimited
26482 These @code{set} commands specify a screen height of @var{lpp} lines and
26483 a screen width of @var{cpl} characters. The associated @code{show}
26484 commands display the current settings.
26486 If you specify a height of either @code{unlimited} or zero lines,
26487 @value{GDBN} does not pause during output no matter how long the
26488 output is. This is useful if output is to a file or to an editor
26491 Likewise, you can specify @samp{set width unlimited} or @samp{set
26492 width 0} to prevent @value{GDBN} from wrapping its output.
26494 @item set pagination on
26495 @itemx set pagination off
26496 @kindex set pagination
26497 Turn the output pagination on or off; the default is on. Turning
26498 pagination off is the alternative to @code{set height unlimited}. Note that
26499 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26500 Options, -batch}) also automatically disables pagination.
26502 @item show pagination
26503 @kindex show pagination
26504 Show the current pagination mode.
26507 @node Output Styling
26508 @section Output Styling
26514 @value{GDBN} can style its output on a capable terminal. This is
26515 enabled by default on most systems, but disabled by default when in
26516 batch mode (@pxref{Mode Options}). Various style settings are available;
26517 and styles can also be disabled entirely.
26520 @item set style enabled @samp{on|off}
26521 Enable or disable all styling. The default is host-dependent, with
26522 most hosts defaulting to @samp{on}.
26524 @item show style enabled
26525 Show the current state of styling.
26527 @item set style sources @samp{on|off}
26528 Enable or disable source code styling. This affects whether source
26529 code, such as the output of the @code{list} command, is styled. The
26530 default is @samp{on}. Note that source styling only works if styling
26531 in general is enabled, and if a source highlighting library is
26532 available to @value{GDBN}.
26534 There are two ways that highlighting can be done. First, if
26535 @value{GDBN} was linked with the GNU Source Highlight library, then it
26536 is used. Otherwise, if @value{GDBN} was configured with Python
26537 scripting support, and if the Python Pygments package is available,
26538 then it will be used.
26540 @item show style sources
26541 Show the current state of source code styling.
26543 @anchor{style_disassembler_enabled}
26544 @item set style disassembler enabled @samp{on|off}
26545 Enable or disable disassembler styling. This affects whether
26546 disassembler output, such as the output of the @code{disassemble}
26547 command, is styled. Disassembler styling only works if styling in
26548 general is enabled (with @code{set style enabled on}), and if a source
26549 highlighting library is available to @value{GDBN}.
26551 The two source highlighting libraries that @value{GDBN} could use to
26552 style disassembler output are; @value{GDBN}'s builtin disassembler, or
26553 the Python Pygments package.
26555 @value{GDBN}'s first choice will be to use the builtin disassembler
26556 for styling, this usually provides better results, being able to style
26557 different types of instruction operands differently. However, the
26558 builtin disassembler is not able to style all architectures.
26560 For architectures that the builtin disassembler is unable to style,
26561 @value{GDBN} will fall back to use the Python Pygments package where
26562 possible. In order to use the Python Pygments package, @value{GDBN}
26563 must be built with Python support, and the Pygments package must be
26566 If neither of these options are available then @value{GDBN} will
26567 produce unstyled disassembler output, even when this setting is
26570 To discover if the current architecture supports styling using the
26571 builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
26572 show libopcodes-styling enabled}}.
26574 @item show style disassembler enabled
26575 Show the current state of disassembler styling.
26579 Subcommands of @code{set style} control specific forms of styling.
26580 These subcommands all follow the same pattern: each style-able object
26581 can be styled with a foreground color, a background color, and an
26584 For example, the style of file names can be controlled using the
26585 @code{set style filename} group of commands:
26588 @item set style filename background @var{color}
26589 Set the background to @var{color}. Valid colors are @samp{none}
26590 (meaning the terminal's default color), @samp{black}, @samp{red},
26591 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26594 @item set style filename foreground @var{color}
26595 Set the foreground to @var{color}. Valid colors are @samp{none}
26596 (meaning the terminal's default color), @samp{black}, @samp{red},
26597 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26600 @item set style filename intensity @var{value}
26601 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26602 (the default), @samp{bold}, and @samp{dim}.
26605 The @code{show style} command and its subcommands are styling
26606 a style name in their output using its own style.
26607 So, use @command{show style} to see the complete list of styles,
26608 their characteristics and the visual aspect of each style.
26610 The style-able objects are:
26613 Control the styling of file names and URLs. By default, this style's
26614 foreground color is green.
26617 Control the styling of function names. These are managed with the
26618 @code{set style function} family of commands. By default, this
26619 style's foreground color is yellow.
26621 This style is also used for symbol names in styled disassembler output
26622 if @value{GDBN} is using its builtin disassembler library for styling
26623 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26627 Control the styling of variable names. These are managed with the
26628 @code{set style variable} family of commands. By default, this style's
26629 foreground color is cyan.
26632 Control the styling of addresses. These are managed with the
26633 @code{set style address} family of commands. By default, this style's
26634 foreground color is blue.
26636 This style is also used for addresses in styled disassembler output
26637 if @value{GDBN} is using its builtin disassembler library for styling
26638 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26642 Control the styling of @value{GDBN}'s version number text. By
26643 default, this style's foreground color is magenta and it has bold
26644 intensity. The version number is displayed in two places, the output
26645 of @command{show version}, and when @value{GDBN} starts up.
26647 In order to control how @value{GDBN} styles the version number at
26648 startup, add the @code{set style version} family of commands to the
26649 early initialization command file (@pxref{Initialization
26653 Control the styling of titles. These are managed with the
26654 @code{set style title} family of commands. By default, this style's
26655 intensity is bold. Commands are using the title style to improve
26656 the readability of large output. For example, the commands
26657 @command{apropos} and @command{help} are using the title style
26658 for the command names.
26661 Control the styling of highlightings. These are managed with the
26662 @code{set style highlight} family of commands. By default, this style's
26663 foreground color is red. Commands are using the highlight style to draw
26664 the user attention to some specific parts of their output. For example,
26665 the command @command{apropos -v REGEXP} uses the highlight style to
26666 mark the documentation parts matching @var{regexp}.
26669 Control the styling of data annotations added by @value{GDBN} to data
26670 it displays. By default, this style's intensity is dim. Metadata
26671 annotations include the @samp{repeats @var{n} times} annotation for
26672 suppressed display of repeated array elements (@pxref{Print Settings}),
26673 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
26674 for errors and @samp{<optimized-out>} annotations for optimized-out
26675 values in displaying stack frame information in backtraces
26676 (@pxref{Backtrace}), etc.
26679 Control the styling of the TUI border. Note that, unlike other
26680 styling options, only the color of the border can be controlled via
26681 @code{set style}. This was done for compatibility reasons, as TUI
26682 controls to set the border's intensity predated the addition of
26683 general styling to @value{GDBN}. @xref{TUI Configuration}.
26685 @item tui-active-border
26686 Control the styling of the active TUI border; that is, the TUI window
26687 that has the focus.
26689 @item disassembler comment
26690 Control the styling of comments in the disassembler output. These are
26691 managed with the @code{set style disassembler comment} family of
26692 commands. This style is only used when @value{GDBN} is styling using
26693 its builtin disassembler library
26694 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26695 enabled}}). By default, this style's intensity is dim, and its
26696 foreground color is white.
26698 @item disassembler immediate
26699 Control the styling of numeric operands in the disassembler output.
26700 These are managed with the @code{set style disassembler immediate}
26701 family of commands. This style is not used for instruction operands
26702 that represent addresses, in that case the @samp{disassembler address}
26703 style is used. This style is only used when @value{GDBN} is styling
26704 using its builtin disassembler library. By default, this style's
26705 foreground color is blue.
26707 @item disassembler address
26708 Control the styling of address operands in the disassembler output.
26709 This is an alias for the @samp{address} style.
26711 @item disassembler symbol
26712 Control the styling of symbol names in the disassembler output. This
26713 is an alias for the @samp{function} style.
26715 @item disassembler mnemonic
26716 Control the styling of instruction mnemonics in the disassembler
26717 output. These are managed with the @code{set style disassembler
26718 mnemonic} family of commands. This style is also used for assembler
26719 directives, e.g.@: @code{.byte}, @code{.word}, etc. This style is
26720 only used when @value{GDBN} is styling using its builtin disassembler
26721 library. By default, this style's foreground color is green.
26723 @item disassembler register
26724 Control the styling of register operands in the disassembler output.
26725 These are managed with the @code{set style disassembler register}
26726 family of commands. This style is only used when @value{GDBN} is
26727 styling using its builtin disassembler library. By default, this style's
26728 foreground color is red.
26734 @cindex number representation
26735 @cindex entering numbers
26737 You can always enter numbers in octal, decimal, or hexadecimal in
26738 @value{GDBN} by the usual conventions: octal numbers begin with
26739 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26740 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26741 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26742 10; likewise, the default display for numbers---when no particular
26743 format is specified---is base 10. You can change the default base for
26744 both input and output with the commands described below.
26747 @kindex set input-radix
26748 @item set input-radix @var{base}
26749 Set the default base for numeric input. Supported choices
26750 for @var{base} are decimal 8, 10, or 16. The base must itself be
26751 specified either unambiguously or using the current input radix; for
26755 set input-radix 012
26756 set input-radix 10.
26757 set input-radix 0xa
26761 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26762 leaves the input radix unchanged, no matter what it was, since
26763 @samp{10}, being without any leading or trailing signs of its base, is
26764 interpreted in the current radix. Thus, if the current radix is 16,
26765 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26768 @kindex set output-radix
26769 @item set output-radix @var{base}
26770 Set the default base for numeric display. Supported choices
26771 for @var{base} are decimal 8, 10, or 16. The base must itself be
26772 specified either unambiguously or using the current input radix.
26774 @kindex show input-radix
26775 @item show input-radix
26776 Display the current default base for numeric input.
26778 @kindex show output-radix
26779 @item show output-radix
26780 Display the current default base for numeric display.
26782 @item set radix @r{[}@var{base}@r{]}
26786 These commands set and show the default base for both input and output
26787 of numbers. @code{set radix} sets the radix of input and output to
26788 the same base; without an argument, it resets the radix back to its
26789 default value of 10.
26794 @section Configuring the Current ABI
26796 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26797 application automatically. However, sometimes you need to override its
26798 conclusions. Use these commands to manage @value{GDBN}'s view of the
26804 @cindex Newlib OS ABI and its influence on the longjmp handling
26806 One @value{GDBN} configuration can debug binaries for multiple operating
26807 system targets, either via remote debugging or native emulation.
26808 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26809 but you can override its conclusion using the @code{set osabi} command.
26810 One example where this is useful is in debugging of binaries which use
26811 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26812 not have the same identifying marks that the standard C library for your
26815 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26816 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26817 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26818 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26822 Show the OS ABI currently in use.
26825 With no argument, show the list of registered available OS ABI's.
26827 @item set osabi @var{abi}
26828 Set the current OS ABI to @var{abi}.
26831 @cindex float promotion
26833 Generally, the way that an argument of type @code{float} is passed to a
26834 function depends on whether the function is prototyped. For a prototyped
26835 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26836 according to the architecture's convention for @code{float}. For unprototyped
26837 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26838 @code{double} and then passed.
26840 Unfortunately, some forms of debug information do not reliably indicate whether
26841 a function is prototyped. If @value{GDBN} calls a function that is not marked
26842 as prototyped, it consults @kbd{set coerce-float-to-double}.
26845 @kindex set coerce-float-to-double
26846 @item set coerce-float-to-double
26847 @itemx set coerce-float-to-double on
26848 Arguments of type @code{float} will be promoted to @code{double} when passed
26849 to an unprototyped function. This is the default setting.
26851 @item set coerce-float-to-double off
26852 Arguments of type @code{float} will be passed directly to unprototyped
26855 @kindex show coerce-float-to-double
26856 @item show coerce-float-to-double
26857 Show the current setting of promoting @code{float} to @code{double}.
26861 @kindex show cp-abi
26862 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26863 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26864 used to build your application. @value{GDBN} only fully supports
26865 programs with a single C@t{++} ABI; if your program contains code using
26866 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26867 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26868 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26869 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26870 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26871 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26876 Show the C@t{++} ABI currently in use.
26879 With no argument, show the list of supported C@t{++} ABI's.
26881 @item set cp-abi @var{abi}
26882 @itemx set cp-abi auto
26883 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26887 @section Automatically loading associated files
26888 @cindex auto-loading
26890 @value{GDBN} sometimes reads files with commands and settings automatically,
26891 without being explicitly told so by the user. We call this feature
26892 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26893 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26894 results or introduce security risks (e.g., if the file comes from untrusted
26897 There are various kinds of files @value{GDBN} can automatically load.
26898 In addition to these files, @value{GDBN} supports auto-loading code written
26899 in various extension languages. @xref{Auto-loading extensions}.
26901 Note that loading of these associated files (including the local @file{.gdbinit}
26902 file) requires accordingly configured @code{auto-load safe-path}
26903 (@pxref{Auto-loading safe path}).
26905 For these reasons, @value{GDBN} includes commands and options to let you
26906 control when to auto-load files and which files should be auto-loaded.
26909 @anchor{set auto-load off}
26910 @kindex set auto-load off
26911 @item set auto-load off
26912 Globally disable loading of all auto-loaded files.
26913 You may want to use this command with the @samp{-iex} option
26914 (@pxref{Option -init-eval-command}) such as:
26916 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26919 Be aware that system init file (@pxref{System-wide configuration})
26920 and init files from your home directory (@pxref{Home Directory Init File})
26921 still get read (as they come from generally trusted directories).
26922 To prevent @value{GDBN} from auto-loading even those init files, use the
26923 @option{-nx} option (@pxref{Mode Options}), in addition to
26924 @code{set auto-load no}.
26926 @anchor{show auto-load}
26927 @kindex show auto-load
26928 @item show auto-load
26929 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26933 (gdb) show auto-load
26934 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26935 libthread-db: Auto-loading of inferior specific libthread_db is on.
26936 local-gdbinit: Auto-loading of .gdbinit script from current directory
26938 python-scripts: Auto-loading of Python scripts is on.
26939 safe-path: List of directories from which it is safe to auto-load files
26940 is $debugdir:$datadir/auto-load.
26941 scripts-directory: List of directories from which to load auto-loaded scripts
26942 is $debugdir:$datadir/auto-load.
26945 @anchor{info auto-load}
26946 @kindex info auto-load
26947 @item info auto-load
26948 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26952 (gdb) info auto-load
26955 Yes /home/user/gdb/gdb-gdb.gdb
26956 libthread-db: No auto-loaded libthread-db.
26957 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26961 Yes /home/user/gdb/gdb-gdb.py
26965 These are @value{GDBN} control commands for the auto-loading:
26967 @multitable @columnfractions .5 .5
26968 @item @xref{set auto-load off}.
26969 @tab Disable auto-loading globally.
26970 @item @xref{show auto-load}.
26971 @tab Show setting of all kinds of files.
26972 @item @xref{info auto-load}.
26973 @tab Show state of all kinds of files.
26974 @item @xref{set auto-load gdb-scripts}.
26975 @tab Control for @value{GDBN} command scripts.
26976 @item @xref{show auto-load gdb-scripts}.
26977 @tab Show setting of @value{GDBN} command scripts.
26978 @item @xref{info auto-load gdb-scripts}.
26979 @tab Show state of @value{GDBN} command scripts.
26980 @item @xref{set auto-load python-scripts}.
26981 @tab Control for @value{GDBN} Python scripts.
26982 @item @xref{show auto-load python-scripts}.
26983 @tab Show setting of @value{GDBN} Python scripts.
26984 @item @xref{info auto-load python-scripts}.
26985 @tab Show state of @value{GDBN} Python scripts.
26986 @item @xref{set auto-load guile-scripts}.
26987 @tab Control for @value{GDBN} Guile scripts.
26988 @item @xref{show auto-load guile-scripts}.
26989 @tab Show setting of @value{GDBN} Guile scripts.
26990 @item @xref{info auto-load guile-scripts}.
26991 @tab Show state of @value{GDBN} Guile scripts.
26992 @item @xref{set auto-load scripts-directory}.
26993 @tab Control for @value{GDBN} auto-loaded scripts location.
26994 @item @xref{show auto-load scripts-directory}.
26995 @tab Show @value{GDBN} auto-loaded scripts location.
26996 @item @xref{add-auto-load-scripts-directory}.
26997 @tab Add directory for auto-loaded scripts location list.
26998 @item @xref{set auto-load local-gdbinit}.
26999 @tab Control for init file in the current directory.
27000 @item @xref{show auto-load local-gdbinit}.
27001 @tab Show setting of init file in the current directory.
27002 @item @xref{info auto-load local-gdbinit}.
27003 @tab Show state of init file in the current directory.
27004 @item @xref{set auto-load libthread-db}.
27005 @tab Control for thread debugging library.
27006 @item @xref{show auto-load libthread-db}.
27007 @tab Show setting of thread debugging library.
27008 @item @xref{info auto-load libthread-db}.
27009 @tab Show state of thread debugging library.
27010 @item @xref{set auto-load safe-path}.
27011 @tab Control directories trusted for automatic loading.
27012 @item @xref{show auto-load safe-path}.
27013 @tab Show directories trusted for automatic loading.
27014 @item @xref{add-auto-load-safe-path}.
27015 @tab Add directory trusted for automatic loading.
27019 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
27020 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
27022 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
27023 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
27026 @node Init File in the Current Directory
27027 @subsection Automatically loading init file in the current directory
27028 @cindex auto-loading init file in the current directory
27030 By default, @value{GDBN} reads and executes the canned sequences of commands
27031 from init file (if any) in the current working directory,
27032 see @ref{Init File in the Current Directory during Startup}.
27034 Note that loading of this local @file{.gdbinit} file also requires accordingly
27035 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27038 @anchor{set auto-load local-gdbinit}
27039 @kindex set auto-load local-gdbinit
27040 @item set auto-load local-gdbinit [on|off]
27041 Enable or disable the auto-loading of canned sequences of commands
27042 (@pxref{Sequences}) found in init file in the current directory.
27044 @anchor{show auto-load local-gdbinit}
27045 @kindex show auto-load local-gdbinit
27046 @item show auto-load local-gdbinit
27047 Show whether auto-loading of canned sequences of commands from init file in the
27048 current directory is enabled or disabled.
27050 @anchor{info auto-load local-gdbinit}
27051 @kindex info auto-load local-gdbinit
27052 @item info auto-load local-gdbinit
27053 Print whether canned sequences of commands from init file in the
27054 current directory have been auto-loaded.
27057 @node libthread_db.so.1 file
27058 @subsection Automatically loading thread debugging library
27059 @cindex auto-loading libthread_db.so.1
27061 This feature is currently present only on @sc{gnu}/Linux native hosts.
27063 @value{GDBN} reads in some cases thread debugging library from places specific
27064 to the inferior (@pxref{set libthread-db-search-path}).
27066 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
27067 without checking this @samp{set auto-load libthread-db} switch as system
27068 libraries have to be trusted in general. In all other cases of
27069 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
27070 auto-load libthread-db} is enabled before trying to open such thread debugging
27073 Note that loading of this debugging library also requires accordingly configured
27074 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27077 @anchor{set auto-load libthread-db}
27078 @kindex set auto-load libthread-db
27079 @item set auto-load libthread-db [on|off]
27080 Enable or disable the auto-loading of inferior specific thread debugging library.
27082 @anchor{show auto-load libthread-db}
27083 @kindex show auto-load libthread-db
27084 @item show auto-load libthread-db
27085 Show whether auto-loading of inferior specific thread debugging library is
27086 enabled or disabled.
27088 @anchor{info auto-load libthread-db}
27089 @kindex info auto-load libthread-db
27090 @item info auto-load libthread-db
27091 Print the list of all loaded inferior specific thread debugging libraries and
27092 for each such library print list of inferior @var{pid}s using it.
27095 @node Auto-loading safe path
27096 @subsection Security restriction for auto-loading
27097 @cindex auto-loading safe-path
27099 As the files of inferior can come from untrusted source (such as submitted by
27100 an application user) @value{GDBN} does not always load any files automatically.
27101 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
27102 directories trusted for loading files not explicitly requested by user.
27103 Each directory can also be a shell wildcard pattern.
27105 If the path is not set properly you will see a warning and the file will not
27110 Reading symbols from /home/user/gdb/gdb...
27111 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
27112 declined by your `auto-load safe-path' set
27113 to "$debugdir:$datadir/auto-load".
27114 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
27115 declined by your `auto-load safe-path' set
27116 to "$debugdir:$datadir/auto-load".
27120 To instruct @value{GDBN} to go ahead and use the init files anyway,
27121 invoke @value{GDBN} like this:
27124 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
27127 The list of trusted directories is controlled by the following commands:
27130 @anchor{set auto-load safe-path}
27131 @kindex set auto-load safe-path
27132 @item set auto-load safe-path @r{[}@var{directories}@r{]}
27133 Set the list of directories (and their subdirectories) trusted for automatic
27134 loading and execution of scripts. You can also enter a specific trusted file.
27135 Each directory can also be a shell wildcard pattern; wildcards do not match
27136 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
27137 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
27138 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
27139 its default value as specified during @value{GDBN} compilation.
27141 The list of directories uses path separator (@samp{:} on GNU and Unix
27142 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27143 to the @env{PATH} environment variable.
27145 @anchor{show auto-load safe-path}
27146 @kindex show auto-load safe-path
27147 @item show auto-load safe-path
27148 Show the list of directories trusted for automatic loading and execution of
27151 @anchor{add-auto-load-safe-path}
27152 @kindex add-auto-load-safe-path
27153 @item add-auto-load-safe-path
27154 Add an entry (or list of entries) to the list of directories trusted for
27155 automatic loading and execution of scripts. Multiple entries may be delimited
27156 by the host platform path separator in use.
27159 This variable defaults to what @code{--with-auto-load-dir} has been configured
27160 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
27161 substitution applies the same as for @ref{set auto-load scripts-directory}.
27162 The default @code{set auto-load safe-path} value can be also overriden by
27163 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
27165 Setting this variable to @file{/} disables this security protection,
27166 corresponding @value{GDBN} configuration option is
27167 @option{--without-auto-load-safe-path}.
27168 This variable is supposed to be set to the system directories writable by the
27169 system superuser only. Users can add their source directories in init files in
27170 their home directories (@pxref{Home Directory Init File}). See also deprecated
27171 init file in the current directory
27172 (@pxref{Init File in the Current Directory during Startup}).
27174 To force @value{GDBN} to load the files it declined to load in the previous
27175 example, you could use one of the following ways:
27178 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
27179 Specify this trusted directory (or a file) as additional component of the list.
27180 You have to specify also any existing directories displayed by
27181 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
27183 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
27184 Specify this directory as in the previous case but just for a single
27185 @value{GDBN} session.
27187 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
27188 Disable auto-loading safety for a single @value{GDBN} session.
27189 This assumes all the files you debug during this @value{GDBN} session will come
27190 from trusted sources.
27192 @item @kbd{./configure --without-auto-load-safe-path}
27193 During compilation of @value{GDBN} you may disable any auto-loading safety.
27194 This assumes all the files you will ever debug with this @value{GDBN} come from
27198 On the other hand you can also explicitly forbid automatic files loading which
27199 also suppresses any such warning messages:
27202 @item @kbd{gdb -iex "set auto-load no" @dots{}}
27203 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
27205 @item @file{~/.gdbinit}: @samp{set auto-load no}
27206 Disable auto-loading globally for the user
27207 (@pxref{Home Directory Init File}). While it is improbable, you could also
27208 use system init file instead (@pxref{System-wide configuration}).
27211 This setting applies to the file names as entered by user. If no entry matches
27212 @value{GDBN} tries as a last resort to also resolve all the file names into
27213 their canonical form (typically resolving symbolic links) and compare the
27214 entries again. @value{GDBN} already canonicalizes most of the filenames on its
27215 own before starting the comparison so a canonical form of directories is
27216 recommended to be entered.
27218 @node Auto-loading verbose mode
27219 @subsection Displaying files tried for auto-load
27220 @cindex auto-loading verbose mode
27222 For better visibility of all the file locations where you can place scripts to
27223 be auto-loaded with inferior --- or to protect yourself against accidental
27224 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
27225 all the files attempted to be loaded. Both existing and non-existing files may
27228 For example the list of directories from which it is safe to auto-load files
27229 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
27230 may not be too obvious while setting it up.
27233 (gdb) set debug auto-load on
27234 (gdb) file ~/src/t/true
27235 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
27236 for objfile "/tmp/true".
27237 auto-load: Updating directories of "/usr:/opt".
27238 auto-load: Using directory "/usr".
27239 auto-load: Using directory "/opt".
27240 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
27241 by your `auto-load safe-path' set to "/usr:/opt".
27245 @anchor{set debug auto-load}
27246 @kindex set debug auto-load
27247 @item set debug auto-load [on|off]
27248 Set whether to print the filenames attempted to be auto-loaded.
27250 @anchor{show debug auto-load}
27251 @kindex show debug auto-load
27252 @item show debug auto-load
27253 Show whether printing of the filenames attempted to be auto-loaded is turned
27257 @node Messages/Warnings
27258 @section Optional Warnings and Messages
27260 @cindex verbose operation
27261 @cindex optional warnings
27262 By default, @value{GDBN} is silent about its inner workings. If you are
27263 running on a slow machine, you may want to use the @code{set verbose}
27264 command. This makes @value{GDBN} tell you when it does a lengthy
27265 internal operation, so you will not think it has crashed.
27267 Currently, the messages controlled by @code{set verbose} are those
27268 which announce that the symbol table for a source file is being read;
27269 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
27272 @kindex set verbose
27273 @item set verbose on
27274 Enables @value{GDBN} output of certain informational messages.
27276 @item set verbose off
27277 Disables @value{GDBN} output of certain informational messages.
27279 @kindex show verbose
27281 Displays whether @code{set verbose} is on or off.
27284 By default, if @value{GDBN} encounters bugs in the symbol table of an
27285 object file, it is silent; but if you are debugging a compiler, you may
27286 find this information useful (@pxref{Symbol Errors, ,Errors Reading
27291 @kindex set complaints
27292 @item set complaints @var{limit}
27293 Permits @value{GDBN} to output @var{limit} complaints about each type of
27294 unusual symbols before becoming silent about the problem. Set
27295 @var{limit} to zero to suppress all complaints; set it to a large number
27296 to prevent complaints from being suppressed.
27298 @kindex show complaints
27299 @item show complaints
27300 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27304 @anchor{confirmation requests}
27305 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27306 lot of stupid questions to confirm certain commands. For example, if
27307 you try to run a program which is already running:
27311 The program being debugged has been started already.
27312 Start it from the beginning? (y or n)
27315 If you are willing to unflinchingly face the consequences of your own
27316 commands, you can disable this ``feature'':
27320 @kindex set confirm
27322 @cindex confirmation
27323 @cindex stupid questions
27324 @item set confirm off
27325 Disables confirmation requests. Note that running @value{GDBN} with
27326 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27327 automatically disables confirmation requests.
27329 @item set confirm on
27330 Enables confirmation requests (the default).
27332 @kindex show confirm
27334 Displays state of confirmation requests.
27338 @cindex command tracing
27339 If you need to debug user-defined commands or sourced files you may find it
27340 useful to enable @dfn{command tracing}. In this mode each command will be
27341 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27342 quantity denoting the call depth of each command.
27345 @kindex set trace-commands
27346 @cindex command scripts, debugging
27347 @item set trace-commands on
27348 Enable command tracing.
27349 @item set trace-commands off
27350 Disable command tracing.
27351 @item show trace-commands
27352 Display the current state of command tracing.
27355 @node Debugging Output
27356 @section Optional Messages about Internal Happenings
27357 @cindex optional debugging messages
27359 @value{GDBN} has commands that enable optional debugging messages from
27360 various @value{GDBN} subsystems; normally these commands are of
27361 interest to @value{GDBN} maintainers, or when reporting a bug. This
27362 section documents those commands.
27365 @kindex set exec-done-display
27366 @item set exec-done-display
27367 Turns on or off the notification of asynchronous commands'
27368 completion. When on, @value{GDBN} will print a message when an
27369 asynchronous command finishes its execution. The default is off.
27370 @kindex show exec-done-display
27371 @item show exec-done-display
27372 Displays the current setting of asynchronous command completion
27376 @cindex ARM AArch64
27377 @item set debug aarch64
27378 Turns on or off display of debugging messages related to ARM AArch64.
27379 The default is off.
27381 @item show debug aarch64
27382 Displays the current state of displaying debugging messages related to
27385 @cindex gdbarch debugging info
27386 @cindex architecture debugging info
27387 @item set debug arch
27388 Turns on or off display of gdbarch debugging info. The default is off
27389 @item show debug arch
27390 Displays the current state of displaying gdbarch debugging info.
27392 @item set debug aix-solib
27393 @cindex AIX shared library debugging
27394 Control display of debugging messages from the AIX shared library
27395 support module. The default is off.
27396 @item show debug aix-solib
27397 Show the current state of displaying AIX shared library debugging messages.
27399 @item set debug aix-thread
27400 @cindex AIX threads
27401 Display debugging messages about inner workings of the AIX thread
27403 @item show debug aix-thread
27404 Show the current state of AIX thread debugging info display.
27406 @item set debug check-physname
27408 Check the results of the ``physname'' computation. When reading DWARF
27409 debugging information for C@t{++}, @value{GDBN} attempts to compute
27410 each entity's name. @value{GDBN} can do this computation in two
27411 different ways, depending on exactly what information is present.
27412 When enabled, this setting causes @value{GDBN} to compute the names
27413 both ways and display any discrepancies.
27414 @item show debug check-physname
27415 Show the current state of ``physname'' checking.
27417 @item set debug coff-pe-read
27418 @cindex COFF/PE exported symbols
27419 Control display of debugging messages related to reading of COFF/PE
27420 exported symbols. The default is off.
27421 @item show debug coff-pe-read
27422 Displays the current state of displaying debugging messages related to
27423 reading of COFF/PE exported symbols.
27425 @item set debug dwarf-die
27427 Dump DWARF DIEs after they are read in.
27428 The value is the number of nesting levels to print.
27429 A value of zero turns off the display.
27430 @item show debug dwarf-die
27431 Show the current state of DWARF DIE debugging.
27433 @item set debug dwarf-line
27434 @cindex DWARF Line Tables
27435 Turns on or off display of debugging messages related to reading
27436 DWARF line tables. The default is 0 (off).
27437 A value of 1 provides basic information.
27438 A value greater than 1 provides more verbose information.
27439 @item show debug dwarf-line
27440 Show the current state of DWARF line table debugging.
27442 @item set debug dwarf-read
27443 @cindex DWARF Reading
27444 Turns on or off display of debugging messages related to reading
27445 DWARF debug info. The default is 0 (off).
27446 A value of 1 provides basic information.
27447 A value greater than 1 provides more verbose information.
27448 @item show debug dwarf-read
27449 Show the current state of DWARF reader debugging.
27451 @item set debug displaced
27452 @cindex displaced stepping debugging info
27453 Turns on or off display of @value{GDBN} debugging info for the
27454 displaced stepping support. The default is off.
27455 @item show debug displaced
27456 Displays the current state of displaying @value{GDBN} debugging info
27457 related to displaced stepping.
27459 @item set debug event
27460 @cindex event debugging info
27461 Turns on or off display of @value{GDBN} event debugging info. The
27463 @item show debug event
27464 Displays the current state of displaying @value{GDBN} event debugging
27467 @item set debug event-loop
27468 @cindex event-loop debugging
27469 Controls output of debugging info about the event loop. The possible
27470 values are @samp{off}, @samp{all} (shows all debugging info) and
27471 @samp{all-except-ui} (shows all debugging info except those about
27472 UI-related events).
27473 @item show debug event-loop
27474 Shows the current state of displaying debugging info about the event
27477 @item set debug expression
27478 @cindex expression debugging info
27479 Turns on or off display of debugging info about @value{GDBN}
27480 expression parsing. The default is off.
27481 @item show debug expression
27482 Displays the current state of displaying debugging info about
27483 @value{GDBN} expression parsing.
27485 @item set debug fbsd-lwp
27486 @cindex FreeBSD LWP debug messages
27487 Turns on or off debugging messages from the FreeBSD LWP debug support.
27488 @item show debug fbsd-lwp
27489 Show the current state of FreeBSD LWP debugging messages.
27491 @item set debug fbsd-nat
27492 @cindex FreeBSD native target debug messages
27493 Turns on or off debugging messages from the FreeBSD native target.
27494 @item show debug fbsd-nat
27495 Show the current state of FreeBSD native target debugging messages.
27497 @item set debug fortran-array-slicing
27498 @cindex fortran array slicing debugging info
27499 Turns on or off display of @value{GDBN} Fortran array slicing
27500 debugging info. The default is off.
27502 @item show debug fortran-array-slicing
27503 Displays the current state of displaying @value{GDBN} Fortran array
27504 slicing debugging info.
27506 @item set debug frame
27507 @cindex frame debugging info
27508 Turns on or off display of @value{GDBN} frame debugging info. The
27510 @item show debug frame
27511 Displays the current state of displaying @value{GDBN} frame debugging
27514 @item set debug gnu-nat
27515 @cindex @sc{gnu}/Hurd debug messages
27516 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27517 @item show debug gnu-nat
27518 Show the current state of @sc{gnu}/Hurd debugging messages.
27520 @item set debug infrun
27521 @cindex inferior debugging info
27522 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27523 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27524 for implementing operations such as single-stepping the inferior.
27525 @item show debug infrun
27526 Displays the current state of @value{GDBN} inferior debugging.
27528 @item set debug jit
27529 @cindex just-in-time compilation, debugging messages
27530 Turn on or off debugging messages from JIT debug support.
27531 @item show debug jit
27532 Displays the current state of @value{GDBN} JIT debugging.
27534 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27535 @cindex @sc{gnu}/Linux native target debug messages
27536 @cindex Linux native targets
27537 Turn on or off debugging messages from the Linux native target debug support.
27538 @item show debug linux-nat
27539 Show the current state of Linux native target debugging messages.
27541 @item set debug linux-namespaces
27542 @cindex @sc{gnu}/Linux namespaces debug messages
27543 Turn on or off debugging messages from the Linux namespaces debug support.
27544 @item show debug linux-namespaces
27545 Show the current state of Linux namespaces debugging messages.
27547 @item set debug mach-o
27548 @cindex Mach-O symbols processing
27549 Control display of debugging messages related to Mach-O symbols
27550 processing. The default is off.
27551 @item show debug mach-o
27552 Displays the current state of displaying debugging messages related to
27553 reading of COFF/PE exported symbols.
27555 @item set debug notification
27556 @cindex remote async notification debugging info
27557 Turn on or off debugging messages about remote async notification.
27558 The default is off.
27559 @item show debug notification
27560 Displays the current state of remote async notification debugging messages.
27562 @item set debug observer
27563 @cindex observer debugging info
27564 Turns on or off display of @value{GDBN} observer debugging. This
27565 includes info such as the notification of observable events.
27566 @item show debug observer
27567 Displays the current state of observer debugging.
27569 @item set debug overload
27570 @cindex C@t{++} overload debugging info
27571 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27572 info. This includes info such as ranking of functions, etc. The default
27574 @item show debug overload
27575 Displays the current state of displaying @value{GDBN} C@t{++} overload
27578 @cindex expression parser, debugging info
27579 @cindex debug expression parser
27580 @item set debug parser
27581 Turns on or off the display of expression parser debugging output.
27582 Internally, this sets the @code{yydebug} variable in the expression
27583 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27584 details. The default is off.
27585 @item show debug parser
27586 Show the current state of expression parser debugging.
27588 @cindex packets, reporting on stdout
27589 @cindex serial connections, debugging
27590 @cindex debug remote protocol
27591 @cindex remote protocol debugging
27592 @cindex display remote packets
27593 @item set debug remote
27594 Turns on or off display of reports on all packets sent back and forth across
27595 the serial line to the remote machine. The info is printed on the
27596 @value{GDBN} standard output stream. The default is off.
27597 @item show debug remote
27598 Displays the state of display of remote packets.
27600 @item set debug remote-packet-max-chars
27601 Sets the maximum number of characters to display for each remote packet when
27602 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27603 displaying lengthy remote packets and polluting the console.
27605 The default value is @code{512}, which means @value{GDBN} will truncate each
27606 remote packet after 512 bytes.
27608 Setting this option to @code{unlimited} will disable truncation and will output
27609 the full length of the remote packets.
27610 @item show debug remote-packet-max-chars
27611 Displays the number of bytes to output for remote packet debugging.
27613 @item set debug separate-debug-file
27614 Turns on or off display of debug output about separate debug file search.
27615 @item show debug separate-debug-file
27616 Displays the state of separate debug file search debug output.
27618 @item set debug serial
27619 Turns on or off display of @value{GDBN} serial debugging info. The
27621 @item show debug serial
27622 Displays the current state of displaying @value{GDBN} serial debugging
27625 @item set debug solib-frv
27626 @cindex FR-V shared-library debugging
27627 Turn on or off debugging messages for FR-V shared-library code.
27628 @item show debug solib-frv
27629 Display the current state of FR-V shared-library code debugging
27632 @item set debug symbol-lookup
27633 @cindex symbol lookup
27634 Turns on or off display of debugging messages related to symbol lookup.
27635 The default is 0 (off).
27636 A value of 1 provides basic information.
27637 A value greater than 1 provides more verbose information.
27638 @item show debug symbol-lookup
27639 Show the current state of symbol lookup debugging messages.
27641 @item set debug symfile
27642 @cindex symbol file functions
27643 Turns on or off display of debugging messages related to symbol file functions.
27644 The default is off. @xref{Files}.
27645 @item show debug symfile
27646 Show the current state of symbol file debugging messages.
27648 @item set debug symtab-create
27649 @cindex symbol table creation
27650 Turns on or off display of debugging messages related to symbol table creation.
27651 The default is 0 (off).
27652 A value of 1 provides basic information.
27653 A value greater than 1 provides more verbose information.
27654 @item show debug symtab-create
27655 Show the current state of symbol table creation debugging.
27657 @item set debug target
27658 @cindex target debugging info
27659 Turns on or off display of @value{GDBN} target debugging info. This info
27660 includes what is going on at the target level of GDB, as it happens. The
27661 default is 0. Set it to 1 to track events, and to 2 to also track the
27662 value of large memory transfers.
27663 @item show debug target
27664 Displays the current state of displaying @value{GDBN} target debugging
27667 @item set debug timestamp
27668 @cindex timestamping debugging info
27669 Turns on or off display of timestamps with @value{GDBN} debugging info.
27670 When enabled, seconds and microseconds are displayed before each debugging
27672 @item show debug timestamp
27673 Displays the current state of displaying timestamps with @value{GDBN}
27676 @item set debug varobj
27677 @cindex variable object debugging info
27678 Turns on or off display of @value{GDBN} variable object debugging
27679 info. The default is off.
27680 @item show debug varobj
27681 Displays the current state of displaying @value{GDBN} variable object
27684 @item set debug xml
27685 @cindex XML parser debugging
27686 Turn on or off debugging messages for built-in XML parsers.
27687 @item show debug xml
27688 Displays the current state of XML debugging messages.
27691 @node Other Misc Settings
27692 @section Other Miscellaneous Settings
27693 @cindex miscellaneous settings
27696 @kindex set interactive-mode
27697 @item set interactive-mode
27698 If @code{on}, forces @value{GDBN} to assume that GDB was started
27699 in a terminal. In practice, this means that @value{GDBN} should wait
27700 for the user to answer queries generated by commands entered at
27701 the command prompt. If @code{off}, forces @value{GDBN} to operate
27702 in the opposite mode, and it uses the default answers to all queries.
27703 If @code{auto} (the default), @value{GDBN} tries to determine whether
27704 its standard input is a terminal, and works in interactive-mode if it
27705 is, non-interactively otherwise.
27707 In the vast majority of cases, the debugger should be able to guess
27708 correctly which mode should be used. But this setting can be useful
27709 in certain specific cases, such as running a MinGW @value{GDBN}
27710 inside a cygwin window.
27712 @kindex show interactive-mode
27713 @item show interactive-mode
27714 Displays whether the debugger is operating in interactive mode or not.
27718 @kindex set suppress-cli-notifications
27719 @item set suppress-cli-notifications
27720 If @code{on}, command-line-interface (CLI) notifications that are
27721 printed by @value{GDBN} are suppressed. If @code{off}, the
27722 notifications are printed as usual. The default value is @code{off}.
27723 CLI notifications occur when you change the selected context or when
27724 the program being debugged stops, as detailed below.
27727 @item User-selected context changes:
27728 When you change the selected context (i.e.@: the current inferior,
27729 thread and/or the frame), @value{GDBN} prints information about the
27730 new context. For example, the default behavior is below:
27734 [Switching to inferior 1 [process 634] (/tmp/test)]
27735 [Switching to thread 1 (process 634)]
27736 #0 main () at test.c:3
27741 When the notifications are suppressed, the new context is not printed:
27744 (gdb) set suppress-cli-notifications on
27749 @item The program being debugged stops:
27750 When the program you are debugging stops (e.g.@: because of hitting a
27751 breakpoint, completing source-stepping, an interrupt, etc.),
27752 @value{GDBN} prints information about the stop event. For example,
27753 below is a breakpoint hit:
27756 (gdb) break test.c:3
27757 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27761 Breakpoint 2, main () at test.c:3
27766 When the notifications are suppressed, the output becomes:
27769 (gdb) break test.c:3
27770 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27771 (gdb) set suppress-cli-notifications on
27777 Suppressing CLI notifications may be useful in scripts to obtain a
27778 reduced output from a list of commands.
27781 @kindex show suppress-cli-notifications
27782 @item show suppress-cli-notifications
27783 Displays whether printing CLI notifications is suppressed or not.
27786 @node Extending GDB
27787 @chapter Extending @value{GDBN}
27788 @cindex extending GDB
27790 @value{GDBN} provides several mechanisms for extension.
27791 @value{GDBN} also provides the ability to automatically load
27792 extensions when it reads a file for debugging. This allows the
27793 user to automatically customize @value{GDBN} for the program
27796 To facilitate the use of extension languages, @value{GDBN} is capable
27797 of evaluating the contents of a file. When doing so, @value{GDBN}
27798 can recognize which extension language is being used by looking at
27799 the filename extension. Files with an unrecognized filename extension
27800 are always treated as a @value{GDBN} Command Files.
27801 @xref{Command Files,, Command files}.
27803 You can control how @value{GDBN} evaluates these files with the following
27807 @kindex set script-extension
27808 @kindex show script-extension
27809 @item set script-extension off
27810 All scripts are always evaluated as @value{GDBN} Command Files.
27812 @item set script-extension soft
27813 The debugger determines the scripting language based on filename
27814 extension. If this scripting language is supported, @value{GDBN}
27815 evaluates the script using that language. Otherwise, it evaluates
27816 the file as a @value{GDBN} Command File.
27818 @item set script-extension strict
27819 The debugger determines the scripting language based on filename
27820 extension, and evaluates the script using that language. If the
27821 language is not supported, then the evaluation fails.
27823 @item show script-extension
27824 Display the current value of the @code{script-extension} option.
27828 @ifset SYSTEM_GDBINIT_DIR
27829 This setting is not used for files in the system-wide gdbinit directory.
27830 Files in that directory must have an extension matching their language,
27831 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27832 commands. @xref{Startup}.
27836 * Sequences:: Canned Sequences of @value{GDBN} Commands
27837 * Aliases:: Command Aliases
27838 * Python:: Extending @value{GDBN} using Python
27839 * Guile:: Extending @value{GDBN} using Guile
27840 * Auto-loading extensions:: Automatically loading extensions
27841 * Multiple Extension Languages:: Working with multiple extension languages
27845 @section Canned Sequences of Commands
27847 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27848 Command Lists}), @value{GDBN} provides two ways to store sequences of
27849 commands for execution as a unit: user-defined commands and command
27853 * Define:: How to define your own commands
27854 * Hooks:: Hooks for user-defined commands
27855 * Command Files:: How to write scripts of commands to be stored in a file
27856 * Output:: Commands for controlled output
27857 * Auto-loading sequences:: Controlling auto-loaded command files
27861 @subsection User-defined Commands
27863 @cindex user-defined command
27864 @cindex arguments, to user-defined commands
27865 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27866 which you assign a new name as a command. This is done with the
27867 @code{define} command. User commands may accept an unlimited number of arguments
27868 separated by whitespace. Arguments are accessed within the user command
27869 via @code{$arg0@dots{}$argN}. A trivial example:
27873 print $arg0 + $arg1 + $arg2
27878 To execute the command use:
27885 This defines the command @code{adder}, which prints the sum of
27886 its three arguments. Note the arguments are text substitutions, so they may
27887 reference variables, use complex expressions, or even perform inferior
27890 @cindex argument count in user-defined commands
27891 @cindex how many arguments (user-defined commands)
27892 In addition, @code{$argc} may be used to find out how many arguments have
27898 print $arg0 + $arg1
27901 print $arg0 + $arg1 + $arg2
27906 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27907 to process a variable number of arguments:
27914 eval "set $sum = $sum + $arg%d", $i
27924 @item define @var{commandname}
27925 Define a command named @var{commandname}. If there is already a command
27926 by that name, you are asked to confirm that you want to redefine it.
27927 The argument @var{commandname} may be a bare command name consisting of letters,
27928 numbers, dashes, dots, and underscores. It may also start with any
27929 predefined or user-defined prefix command.
27930 For example, @samp{define target my-target} creates
27931 a user-defined @samp{target my-target} command.
27933 The definition of the command is made up of other @value{GDBN} command lines,
27934 which are given following the @code{define} command. The end of these
27935 commands is marked by a line containing @code{end}.
27938 @kindex end@r{ (user-defined commands)}
27939 @item document @var{commandname}
27940 Document the user-defined command @var{commandname}, so that it can be
27941 accessed by @code{help}. The command @var{commandname} must already be
27942 defined. This command reads lines of documentation just as @code{define}
27943 reads the lines of the command definition, ending with @code{end}.
27944 After the @code{document} command is finished, @code{help} on command
27945 @var{commandname} displays the documentation you have written.
27947 You may use the @code{document} command again to change the
27948 documentation of a command. Redefining the command with @code{define}
27949 does not change the documentation.
27951 @kindex define-prefix
27952 @item define-prefix @var{commandname}
27953 Define or mark the command @var{commandname} as a user-defined prefix
27954 command. Once marked, @var{commandname} can be used as prefix command
27955 by the @code{define} command.
27956 Note that @code{define-prefix} can be used with a not yet defined
27957 @var{commandname}. In such a case, @var{commandname} is defined as
27958 an empty user-defined command.
27959 In case you redefine a command that was marked as a user-defined
27960 prefix command, the subcommands of the redefined command are kept
27961 (and @value{GDBN} indicates so to the user).
27965 (gdb) define-prefix abc
27966 (gdb) define-prefix abc def
27967 (gdb) define abc def
27968 Type commands for definition of "abc def".
27969 End with a line saying just "end".
27970 >echo command initial def\n
27972 (gdb) define abc def ghi
27973 Type commands for definition of "abc def ghi".
27974 End with a line saying just "end".
27975 >echo command ghi\n
27977 (gdb) define abc def
27978 Keeping subcommands of prefix command "def".
27979 Redefine command "def"? (y or n) y
27980 Type commands for definition of "abc def".
27981 End with a line saying just "end".
27982 >echo command def\n
27991 @kindex dont-repeat
27992 @cindex don't repeat command
27994 Used inside a user-defined command, this tells @value{GDBN} that this
27995 command should not be repeated when the user hits @key{RET}
27996 (@pxref{Command Syntax, repeat last command}).
27998 @kindex help user-defined
27999 @item help user-defined
28000 List all user-defined commands and all python commands defined in class
28001 COMMAND_USER. The first line of the documentation or docstring is
28006 @itemx show user @var{commandname}
28007 Display the @value{GDBN} commands used to define @var{commandname} (but
28008 not its documentation). If no @var{commandname} is given, display the
28009 definitions for all user-defined commands.
28010 This does not work for user-defined python commands.
28012 @cindex infinite recursion in user-defined commands
28013 @kindex show max-user-call-depth
28014 @kindex set max-user-call-depth
28015 @item show max-user-call-depth
28016 @itemx set max-user-call-depth
28017 The value of @code{max-user-call-depth} controls how many recursion
28018 levels are allowed in user-defined commands before @value{GDBN} suspects an
28019 infinite recursion and aborts the command.
28020 This does not apply to user-defined python commands.
28023 In addition to the above commands, user-defined commands frequently
28024 use control flow commands, described in @ref{Command Files}.
28026 When user-defined commands are executed, the
28027 commands of the definition are not printed. An error in any command
28028 stops execution of the user-defined command.
28030 If used interactively, commands that would ask for confirmation proceed
28031 without asking when used inside a user-defined command. Many @value{GDBN}
28032 commands that normally print messages to say what they are doing omit the
28033 messages when used in a user-defined command.
28036 @subsection User-defined Command Hooks
28037 @cindex command hooks
28038 @cindex hooks, for commands
28039 @cindex hooks, pre-command
28042 You may define @dfn{hooks}, which are a special kind of user-defined
28043 command. Whenever you run the command @samp{foo}, if the user-defined
28044 command @samp{hook-foo} exists, it is executed (with no arguments)
28045 before that command.
28047 @cindex hooks, post-command
28049 A hook may also be defined which is run after the command you executed.
28050 Whenever you run the command @samp{foo}, if the user-defined command
28051 @samp{hookpost-foo} exists, it is executed (with no arguments) after
28052 that command. Post-execution hooks may exist simultaneously with
28053 pre-execution hooks, for the same command.
28055 It is valid for a hook to call the command which it hooks. If this
28056 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
28058 @c It would be nice if hookpost could be passed a parameter indicating
28059 @c if the command it hooks executed properly or not. FIXME!
28061 @kindex stop@r{, a pseudo-command}
28062 In addition, a pseudo-command, @samp{stop} exists. Defining
28063 (@samp{hook-stop}) makes the associated commands execute every time
28064 execution stops in your program: before breakpoint commands are run,
28065 displays are printed, or the stack frame is printed.
28067 For example, to ignore @code{SIGALRM} signals while
28068 single-stepping, but treat them normally during normal execution,
28073 handle SIGALRM nopass
28077 handle SIGALRM pass
28080 define hook-continue
28081 handle SIGALRM pass
28085 As a further example, to hook at the beginning and end of the @code{echo}
28086 command, and to add extra text to the beginning and end of the message,
28094 define hookpost-echo
28098 (@value{GDBP}) echo Hello World
28099 <<<---Hello World--->>>
28104 You can define a hook for any single-word command in @value{GDBN}, but
28105 not for command aliases; you should define a hook for the basic command
28106 name, e.g.@: @code{backtrace} rather than @code{bt}.
28107 @c FIXME! So how does Joe User discover whether a command is an alias
28109 You can hook a multi-word command by adding @code{hook-} or
28110 @code{hookpost-} to the last word of the command, e.g.@:
28111 @samp{define target hook-remote} to add a hook to @samp{target remote}.
28113 If an error occurs during the execution of your hook, execution of
28114 @value{GDBN} commands stops and @value{GDBN} issues a prompt
28115 (before the command that you actually typed had a chance to run).
28117 If you try to define a hook which does not match any known command, you
28118 get a warning from the @code{define} command.
28120 @node Command Files
28121 @subsection Command Files
28123 @cindex command files
28124 @cindex scripting commands
28125 A command file for @value{GDBN} is a text file made of lines that are
28126 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
28127 also be included. An empty line in a command file does nothing; it
28128 does not mean to repeat the last command, as it would from the
28131 You can request the execution of a command file with the @code{source}
28132 command. Note that the @code{source} command is also used to evaluate
28133 scripts that are not Command Files. The exact behavior can be configured
28134 using the @code{script-extension} setting.
28135 @xref{Extending GDB,, Extending GDB}.
28139 @cindex execute commands from a file
28140 @item source [-s] [-v] @var{filename}
28141 Execute the command file @var{filename}.
28144 The lines in a command file are generally executed sequentially,
28145 unless the order of execution is changed by one of the
28146 @emph{flow-control commands} described below. The commands are not
28147 printed as they are executed. An error in any command terminates
28148 execution of the command file and control is returned to the console.
28150 @value{GDBN} first searches for @var{filename} in the current directory.
28151 If the file is not found there, and @var{filename} does not specify a
28152 directory, then @value{GDBN} also looks for the file on the source search path
28153 (specified with the @samp{directory} command);
28154 except that @file{$cdir} is not searched because the compilation directory
28155 is not relevant to scripts.
28157 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
28158 on the search path even if @var{filename} specifies a directory.
28159 The search is done by appending @var{filename} to each element of the
28160 search path. So, for example, if @var{filename} is @file{mylib/myscript}
28161 and the search path contains @file{/home/user} then @value{GDBN} will
28162 look for the script @file{/home/user/mylib/myscript}.
28163 The search is also done if @var{filename} is an absolute path.
28164 For example, if @var{filename} is @file{/tmp/myscript} and
28165 the search path contains @file{/home/user} then @value{GDBN} will
28166 look for the script @file{/home/user/tmp/myscript}.
28167 For DOS-like systems, if @var{filename} contains a drive specification,
28168 it is stripped before concatenation. For example, if @var{filename} is
28169 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
28170 will look for the script @file{c:/tmp/myscript}.
28172 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
28173 each command as it is executed. The option must be given before
28174 @var{filename}, and is interpreted as part of the filename anywhere else.
28176 Commands that would ask for confirmation if used interactively proceed
28177 without asking when used in a command file. Many @value{GDBN} commands that
28178 normally print messages to say what they are doing omit the messages
28179 when called from command files.
28181 @value{GDBN} also accepts command input from standard input. In this
28182 mode, normal output goes to standard output and error output goes to
28183 standard error. Errors in a command file supplied on standard input do
28184 not terminate execution of the command file---execution continues with
28188 gdb < cmds > log 2>&1
28191 (The syntax above will vary depending on the shell used.) This example
28192 will execute commands from the file @file{cmds}. All output and errors
28193 would be directed to @file{log}.
28195 Since commands stored on command files tend to be more general than
28196 commands typed interactively, they frequently need to deal with
28197 complicated situations, such as different or unexpected values of
28198 variables and symbols, changes in how the program being debugged is
28199 built, etc. @value{GDBN} provides a set of flow-control commands to
28200 deal with these complexities. Using these commands, you can write
28201 complex scripts that loop over data structures, execute commands
28202 conditionally, etc.
28209 This command allows to include in your script conditionally executed
28210 commands. The @code{if} command takes a single argument, which is an
28211 expression to evaluate. It is followed by a series of commands that
28212 are executed only if the expression is true (its value is nonzero).
28213 There can then optionally be an @code{else} line, followed by a series
28214 of commands that are only executed if the expression was false. The
28215 end of the list is marked by a line containing @code{end}.
28219 This command allows to write loops. Its syntax is similar to
28220 @code{if}: the command takes a single argument, which is an expression
28221 to evaluate, and must be followed by the commands to execute, one per
28222 line, terminated by an @code{end}. These commands are called the
28223 @dfn{body} of the loop. The commands in the body of @code{while} are
28224 executed repeatedly as long as the expression evaluates to true.
28228 This command exits the @code{while} loop in whose body it is included.
28229 Execution of the script continues after that @code{while}s @code{end}
28232 @kindex loop_continue
28233 @item loop_continue
28234 This command skips the execution of the rest of the body of commands
28235 in the @code{while} loop in whose body it is included. Execution
28236 branches to the beginning of the @code{while} loop, where it evaluates
28237 the controlling expression.
28239 @kindex end@r{ (if/else/while commands)}
28241 Terminate the block of commands that are the body of @code{if},
28242 @code{else}, or @code{while} flow-control commands.
28247 @subsection Commands for Controlled Output
28249 During the execution of a command file or a user-defined command, normal
28250 @value{GDBN} output is suppressed; the only output that appears is what is
28251 explicitly printed by the commands in the definition. This section
28252 describes three commands useful for generating exactly the output you
28257 @item echo @var{text}
28258 @c I do not consider backslash-space a standard C escape sequence
28259 @c because it is not in ANSI.
28260 Print @var{text}. Nonprinting characters can be included in
28261 @var{text} using C escape sequences, such as @samp{\n} to print a
28262 newline. @strong{No newline is printed unless you specify one.}
28263 In addition to the standard C escape sequences, a backslash followed
28264 by a space stands for a space. This is useful for displaying a
28265 string with spaces at the beginning or the end, since leading and
28266 trailing spaces are otherwise trimmed from all arguments.
28267 To print @samp{@w{ }and foo =@w{ }}, use the command
28268 @samp{echo \@w{ }and foo = \@w{ }}.
28270 A backslash at the end of @var{text} can be used, as in C, to continue
28271 the command onto subsequent lines. For example,
28274 echo This is some text\n\
28275 which is continued\n\
28276 onto several lines.\n
28279 produces the same output as
28282 echo This is some text\n
28283 echo which is continued\n
28284 echo onto several lines.\n
28288 @item output @var{expression}
28289 Print the value of @var{expression} and nothing but that value: no
28290 newlines, no @samp{$@var{nn} = }. The value is not entered in the
28291 value history either. @xref{Expressions, ,Expressions}, for more information
28294 @item output/@var{fmt} @var{expression}
28295 Print the value of @var{expression} in format @var{fmt}. You can use
28296 the same formats as for @code{print}. @xref{Output Formats,,Output
28297 Formats}, for more information.
28300 @item printf @var{template}, @var{expressions}@dots{}
28301 Print the values of one or more @var{expressions} under the control of
28302 the string @var{template}. To print several values, make
28303 @var{expressions} be a comma-separated list of individual expressions,
28304 which may be either numbers or pointers. Their values are printed as
28305 specified by @var{template}, exactly as a C program would do by
28306 executing the code below:
28309 printf (@var{template}, @var{expressions}@dots{});
28312 As in @code{C} @code{printf}, ordinary characters in @var{template}
28313 are printed verbatim, while @dfn{conversion specification} introduced
28314 by the @samp{%} character cause subsequent @var{expressions} to be
28315 evaluated, their values converted and formatted according to type and
28316 style information encoded in the conversion specifications, and then
28319 For example, you can print two values in hex like this:
28322 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28325 @code{printf} supports all the standard @code{C} conversion
28326 specifications, including the flags and modifiers between the @samp{%}
28327 character and the conversion letter, with the following exceptions:
28331 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28334 The modifier @samp{*} is not supported for specifying precision or
28338 The @samp{'} flag (for separation of digits into groups according to
28339 @code{LC_NUMERIC'}) is not supported.
28342 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28346 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28349 The conversion letters @samp{a} and @samp{A} are not supported.
28353 Note that the @samp{ll} type modifier is supported only if the
28354 underlying @code{C} implementation used to build @value{GDBN} supports
28355 the @code{long long int} type, and the @samp{L} type modifier is
28356 supported only if @code{long double} type is available.
28358 As in @code{C}, @code{printf} supports simple backslash-escape
28359 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28360 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28361 single character. Octal and hexadecimal escape sequences are not
28364 Additionally, @code{printf} supports conversion specifications for DFP
28365 (@dfn{Decimal Floating Point}) types using the following length modifiers
28366 together with a floating point specifier.
28371 @samp{H} for printing @code{Decimal32} types.
28374 @samp{D} for printing @code{Decimal64} types.
28377 @samp{DD} for printing @code{Decimal128} types.
28380 If the underlying @code{C} implementation used to build @value{GDBN} has
28381 support for the three length modifiers for DFP types, other modifiers
28382 such as width and precision will also be available for @value{GDBN} to use.
28384 In case there is no such @code{C} support, no additional modifiers will be
28385 available and the value will be printed in the standard way.
28387 Here's an example of printing DFP types using the above conversion letters:
28389 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28394 @item eval @var{template}, @var{expressions}@dots{}
28395 Convert the values of one or more @var{expressions} under the control of
28396 the string @var{template} to a command line, and call it.
28400 @node Auto-loading sequences
28401 @subsection Controlling auto-loading native @value{GDBN} scripts
28402 @cindex native script auto-loading
28404 When a new object file is read (for example, due to the @code{file}
28405 command, or because the inferior has loaded a shared library),
28406 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28407 @xref{Auto-loading extensions}.
28409 Auto-loading can be enabled or disabled,
28410 and the list of auto-loaded scripts can be printed.
28413 @anchor{set auto-load gdb-scripts}
28414 @kindex set auto-load gdb-scripts
28415 @item set auto-load gdb-scripts [on|off]
28416 Enable or disable the auto-loading of canned sequences of commands scripts.
28418 @anchor{show auto-load gdb-scripts}
28419 @kindex show auto-load gdb-scripts
28420 @item show auto-load gdb-scripts
28421 Show whether auto-loading of canned sequences of commands scripts is enabled or
28424 @anchor{info auto-load gdb-scripts}
28425 @kindex info auto-load gdb-scripts
28426 @cindex print list of auto-loaded canned sequences of commands scripts
28427 @item info auto-load gdb-scripts [@var{regexp}]
28428 Print the list of all canned sequences of commands scripts that @value{GDBN}
28432 If @var{regexp} is supplied only canned sequences of commands scripts with
28433 matching names are printed.
28436 @section Command Aliases
28437 @cindex aliases for commands
28439 Aliases allow you to define alternate spellings for existing commands.
28440 For example, if a new @value{GDBN} command defined in Python
28441 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28442 version of it that involves less typing.
28444 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28445 of the @samp{step} command even though it is otherwise an ambiguous
28446 abbreviation of other commands like @samp{set} and @samp{show}.
28448 Aliases are also used to provide shortened or more common versions
28449 of multi-word commands. For example, @value{GDBN} provides the
28450 @samp{tty} alias of the @samp{set inferior-tty} command.
28452 You can define a new alias with the @samp{alias} command.
28457 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28461 @var{alias} specifies the name of the new alias. Each word of
28462 @var{alias} must consist of letters, numbers, dashes and underscores.
28464 @var{command} specifies the name of an existing command
28465 that is being aliased.
28467 @var{command} can also be the name of an existing alias. In this
28468 case, @var{command} cannot be an alias that has default arguments.
28470 The @samp{-a} option specifies that the new alias is an abbreviation
28471 of the command. Abbreviations are not used in command completion.
28473 The @samp{--} option specifies the end of options,
28474 and is useful when @var{alias} begins with a dash.
28476 You can specify @var{default-args} for your alias. These
28477 @var{default-args} will be automatically added before the alias
28478 arguments typed explicitly on the command line.
28480 For example, the below defines an alias @code{btfullall} that shows all local
28481 variables and all frame arguments:
28483 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28486 For more information about @var{default-args}, see @ref{Command
28487 aliases default args, ,Default Arguments}.
28489 Here is a simple example showing how to make an abbreviation of a
28490 command so that there is less to type. Suppose you were tired of
28491 typing @samp{disas}, the current shortest unambiguous abbreviation of
28492 the @samp{disassemble} command and you wanted an even shorter version
28493 named @samp{di}. The following will accomplish this.
28496 (gdb) alias -a di = disas
28499 Note that aliases are different from user-defined commands. With a
28500 user-defined command, you also need to write documentation for it with
28501 the @samp{document} command. An alias automatically picks up the
28502 documentation of the existing command.
28504 Here is an example where we make @samp{elms} an abbreviation of
28505 @samp{elements} in the @samp{set print elements} command.
28506 This is to show that you can make an abbreviation of any part
28510 (gdb) alias -a set print elms = set print elements
28511 (gdb) alias -a show print elms = show print elements
28512 (gdb) set p elms 200
28514 Limit on string chars or array elements to print is 200.
28517 Note that if you are defining an alias of a @samp{set} command,
28518 and you want to have an alias for the corresponding @samp{show}
28519 command, then you need to define the latter separately.
28521 Unambiguously abbreviated commands are allowed in @var{command} and
28522 @var{alias}, just as they are normally.
28525 (gdb) alias -a set pr elms = set p ele
28528 Finally, here is an example showing the creation of a one word
28529 alias for a more complex command.
28530 This creates alias @samp{spe} of the command @samp{set print elements}.
28533 (gdb) alias spe = set print elements
28538 * Command aliases default args:: Default arguments for aliases
28541 @node Command aliases default args
28542 @subsection Default Arguments
28543 @cindex aliases for commands, default arguments
28545 You can tell @value{GDBN} to always prepend some default arguments to
28546 the list of arguments provided explicitly by the user when using a
28547 user-defined alias.
28549 If you repeatedly use the same arguments or options for a command, you
28550 can define an alias for this command and tell @value{GDBN} to
28551 automatically prepend these arguments or options to the list of
28552 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28553 could easily accept default arguments for pre-defined commands and aliases,
28554 but it was deemed this would be confusing, and so is not allowed.}.
28556 For example, if you often use the command @code{thread apply all}
28557 specifying to work on the threads in ascending order and to continue in case it
28558 encounters an error, you can tell @value{GDBN} to automatically preprend
28559 the @code{-ascending} and @code{-c} options by using:
28562 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28565 Once you have defined this alias with its default args, any time you type
28566 the @code{thread apply asc-all} followed by @code{some arguments},
28567 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28569 To have even less to type, you can also define a one word alias:
28571 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28574 As usual, unambiguous abbreviations can be used for @var{alias}
28575 and @var{default-args}.
28577 The different aliases of a command do not share their default args.
28578 For example, you define a new alias @code{bt_ALL} showing all possible
28579 information and another alias @code{bt_SMALL} showing very limited information
28582 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28583 -past-main -past-entry -full
28584 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28585 -past-main off -past-entry off
28588 (For more on using the @code{alias} command, see @ref{Aliases}.)
28590 Default args are not limited to the arguments and options of @var{command},
28591 but can specify nested commands if @var{command} accepts such a nested command
28593 For example, the below defines @code{faalocalsoftype} that lists the
28594 frames having locals of a certain type, together with the matching
28597 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28598 (@value{GDBP}) faalocalsoftype int
28599 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28604 This is also very useful to define an alias for a set of nested @code{with}
28605 commands to have a particular combination of temporary settings. For example,
28606 the below defines the alias @code{pp10} that pretty prints an expression
28607 argument, with a maximum of 10 elements if the expression is a string or
28610 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28612 This defines the alias @code{pp10} as being a sequence of 3 commands.
28613 The first part @code{with print pretty --} temporarily activates the setting
28614 @code{set print pretty}, then launches the command that follows the separator
28616 The command following the first part is also a @code{with} command that
28617 temporarily changes the setting @code{set print elements} to 10, then
28618 launches the command that follows the second separator @code{--}.
28619 The third part @code{print} is the command the @code{pp10} alias will launch,
28620 using the temporary values of the settings and the arguments explicitly given
28622 For more information about the @code{with} command usage,
28623 see @ref{Command Settings}.
28625 @c Python docs live in a separate file.
28626 @include python.texi
28628 @c Guile docs live in a separate file.
28629 @include guile.texi
28631 @node Auto-loading extensions
28632 @section Auto-loading extensions
28633 @cindex auto-loading extensions
28635 @value{GDBN} provides two mechanisms for automatically loading
28636 extensions when a new object file is read (for example, due to the
28637 @code{file} command, or because the inferior has loaded a shared
28638 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28639 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28640 @code{.debug_gdb_scripts} section of modern file formats like ELF
28641 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28642 section}). For a discussion of the differences between these two
28643 approaches see @ref{Which flavor to choose?}.
28645 The auto-loading feature is useful for supplying application-specific
28646 debugging commands and features.
28648 Auto-loading can be enabled or disabled,
28649 and the list of auto-loaded scripts can be printed.
28650 See the @samp{auto-loading} section of each extension language
28651 for more information.
28652 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28653 For Python files see @ref{Python Auto-loading}.
28655 Note that loading of this script file also requires accordingly configured
28656 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28659 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28660 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28661 * Which flavor to choose?:: Choosing between these approaches
28664 @node objfile-gdbdotext file
28665 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28666 @cindex @file{@var{objfile}-gdb.gdb}
28667 @cindex @file{@var{objfile}-gdb.py}
28668 @cindex @file{@var{objfile}-gdb.scm}
28670 When a new object file is read, @value{GDBN} looks for a file named
28671 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28672 where @var{objfile} is the object file's name and
28673 where @var{ext} is the file extension for the extension language:
28676 @item @file{@var{objfile}-gdb.gdb}
28677 GDB's own command language
28678 @item @file{@var{objfile}-gdb.py}
28680 @item @file{@var{objfile}-gdb.scm}
28684 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28685 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28686 components, and appending the @file{-gdb.@var{ext}} suffix.
28687 If this file exists and is readable, @value{GDBN} will evaluate it as a
28688 script in the specified extension language.
28690 If this file does not exist, then @value{GDBN} will look for
28691 @var{script-name} file in all of the directories as specified below.
28692 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28693 directories is converted to a one-letter subdirectory, i.e.@:
28694 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28695 filesystems disallow colons in file names.)
28697 Note that loading of these files requires an accordingly configured
28698 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28700 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28701 scripts normally according to its @file{.exe} filename. But if no scripts are
28702 found @value{GDBN} also tries script filenames matching the object file without
28703 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28704 is attempted on any platform. This makes the script filenames compatible
28705 between Unix and MS-Windows hosts.
28708 @anchor{set auto-load scripts-directory}
28709 @kindex set auto-load scripts-directory
28710 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28711 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28712 may be delimited by the host platform path separator in use
28713 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28715 Each entry here needs to be covered also by the security setting
28716 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28718 @anchor{with-auto-load-dir}
28719 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28720 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28721 configuration option @option{--with-auto-load-dir}.
28723 Any reference to @file{$debugdir} will get replaced by
28724 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28725 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28726 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28727 @file{$datadir} must be placed as a directory component --- either alone or
28728 delimited by @file{/} or @file{\} directory separators, depending on the host
28731 The list of directories uses path separator (@samp{:} on GNU and Unix
28732 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28733 to the @env{PATH} environment variable.
28735 @anchor{show auto-load scripts-directory}
28736 @kindex show auto-load scripts-directory
28737 @item show auto-load scripts-directory
28738 Show @value{GDBN} auto-loaded scripts location.
28740 @anchor{add-auto-load-scripts-directory}
28741 @kindex add-auto-load-scripts-directory
28742 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28743 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28744 Multiple entries may be delimited by the host platform path separator in use.
28747 @value{GDBN} does not track which files it has already auto-loaded this way.
28748 @value{GDBN} will load the associated script every time the corresponding
28749 @var{objfile} is opened.
28750 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28751 is evaluated more than once.
28753 @node dotdebug_gdb_scripts section
28754 @subsection The @code{.debug_gdb_scripts} section
28755 @cindex @code{.debug_gdb_scripts} section
28757 For systems using file formats like ELF and COFF,
28758 when @value{GDBN} loads a new object file
28759 it will look for a special section named @code{.debug_gdb_scripts}.
28760 If this section exists, its contents is a list of null-terminated entries
28761 specifying scripts to load. Each entry begins with a non-null prefix byte that
28762 specifies the kind of entry, typically the extension language and whether the
28763 script is in a file or inlined in @code{.debug_gdb_scripts}.
28765 The following entries are supported:
28768 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28769 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28770 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28771 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28774 @subsubsection Script File Entries
28776 If the entry specifies a file, @value{GDBN} will look for the file first
28777 in the current directory and then along the source search path
28778 (@pxref{Source Path, ,Specifying Source Directories}),
28779 except that @file{$cdir} is not searched, since the compilation
28780 directory is not relevant to scripts.
28782 File entries can be placed in section @code{.debug_gdb_scripts} with,
28783 for example, this GCC macro for Python scripts.
28786 /* Note: The "MS" section flags are to remove duplicates. */
28787 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28789 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28790 .byte 1 /* Python */\n\
28791 .asciz \"" script_name "\"\n\
28797 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28798 Then one can reference the macro in a header or source file like this:
28801 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28804 The script name may include directories if desired.
28806 Note that loading of this script file also requires accordingly configured
28807 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28809 If the macro invocation is put in a header, any application or library
28810 using this header will get a reference to the specified script,
28811 and with the use of @code{"MS"} attributes on the section, the linker
28812 will remove duplicates.
28814 @subsubsection Script Text Entries
28816 Script text entries allow to put the executable script in the entry
28817 itself instead of loading it from a file.
28818 The first line of the entry, everything after the prefix byte and up to
28819 the first newline (@code{0xa}) character, is the script name, and must not
28820 contain any kind of space character, e.g., spaces or tabs.
28821 The rest of the entry, up to the trailing null byte, is the script to
28822 execute in the specified language. The name needs to be unique among
28823 all script names, as @value{GDBN} executes each script only once based
28826 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28830 #include "symcat.h"
28831 #include "gdb/section-scripts.h"
28833 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28834 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28835 ".ascii \"gdb.inlined-script\\n\"\n"
28836 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28837 ".ascii \" def __init__ (self):\\n\"\n"
28838 ".ascii \" super (test_cmd, self).__init__ ("
28839 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28840 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28841 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28842 ".ascii \"test_cmd ()\\n\"\n"
28848 Loading of inlined scripts requires a properly configured
28849 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28850 The path to specify in @code{auto-load safe-path} is the path of the file
28851 containing the @code{.debug_gdb_scripts} section.
28853 @node Which flavor to choose?
28854 @subsection Which flavor to choose?
28856 Given the multiple ways of auto-loading extensions, it might not always
28857 be clear which one to choose. This section provides some guidance.
28860 Benefits of the @file{-gdb.@var{ext}} way:
28864 Can be used with file formats that don't support multiple sections.
28867 Ease of finding scripts for public libraries.
28869 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28870 in the source search path.
28871 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28872 isn't a source directory in which to find the script.
28875 Doesn't require source code additions.
28879 Benefits of the @code{.debug_gdb_scripts} way:
28883 Works with static linking.
28885 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28886 trigger their loading. When an application is statically linked the only
28887 objfile available is the executable, and it is cumbersome to attach all the
28888 scripts from all the input libraries to the executable's
28889 @file{-gdb.@var{ext}} script.
28892 Works with classes that are entirely inlined.
28894 Some classes can be entirely inlined, and thus there may not be an associated
28895 shared library to attach a @file{-gdb.@var{ext}} script to.
28898 Scripts needn't be copied out of the source tree.
28900 In some circumstances, apps can be built out of large collections of internal
28901 libraries, and the build infrastructure necessary to install the
28902 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28903 cumbersome. It may be easier to specify the scripts in the
28904 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28905 top of the source tree to the source search path.
28908 @node Multiple Extension Languages
28909 @section Multiple Extension Languages
28911 The Guile and Python extension languages do not share any state,
28912 and generally do not interfere with each other.
28913 There are some things to be aware of, however.
28915 @subsection Python comes first
28917 Python was @value{GDBN}'s first extension language, and to avoid breaking
28918 existing behaviour Python comes first. This is generally solved by the
28919 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28920 extension languages, and when it makes a call to an extension language,
28921 (say to pretty-print a value), it tries each in turn until an extension
28922 language indicates it has performed the request (e.g., has returned the
28923 pretty-printed form of a value).
28924 This extends to errors while performing such requests: If an error happens
28925 while, for example, trying to pretty-print an object then the error is
28926 reported and any following extension languages are not tried.
28929 @chapter Command Interpreters
28930 @cindex command interpreters
28932 @value{GDBN} supports multiple command interpreters, and some command
28933 infrastructure to allow users or user interface writers to switch
28934 between interpreters or run commands in other interpreters.
28936 @value{GDBN} currently supports two command interpreters, the console
28937 interpreter (sometimes called the command-line interpreter or @sc{cli})
28938 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28939 describes both of these interfaces in great detail.
28941 By default, @value{GDBN} will start with the console interpreter.
28942 However, the user may choose to start @value{GDBN} with another
28943 interpreter by specifying the @option{-i} or @option{--interpreter}
28944 startup options. Defined interpreters include:
28948 @cindex console interpreter
28949 The traditional console or command-line interpreter. This is the most often
28950 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28951 @value{GDBN} will use this interpreter.
28954 @cindex mi interpreter
28955 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28956 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28957 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28961 @cindex mi3 interpreter
28962 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28965 @cindex mi2 interpreter
28966 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28969 @cindex mi1 interpreter
28970 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28974 @cindex invoke another interpreter
28976 @kindex interpreter-exec
28977 You may execute commands in any interpreter from the current
28978 interpreter using the appropriate command. If you are running the
28979 console interpreter, simply use the @code{interpreter-exec} command:
28982 interpreter-exec mi "-data-list-register-names"
28985 @sc{gdb/mi} has a similar command, although it is only available in versions of
28986 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28988 Note that @code{interpreter-exec} only changes the interpreter for the
28989 duration of the specified command. It does not change the interpreter
28992 @cindex start a new independent interpreter
28994 Although you may only choose a single interpreter at startup, it is
28995 possible to run an independent interpreter on a specified input/output
28996 device (usually a tty).
28998 For example, consider a debugger GUI or IDE that wants to provide a
28999 @value{GDBN} console view. It may do so by embedding a terminal
29000 emulator widget in its GUI, starting @value{GDBN} in the traditional
29001 command-line mode with stdin/stdout/stderr redirected to that
29002 terminal, and then creating an MI interpreter running on a specified
29003 input/output device. The console interpreter created by @value{GDBN}
29004 at startup handles commands the user types in the terminal widget,
29005 while the GUI controls and synchronizes state with @value{GDBN} using
29006 the separate MI interpreter.
29008 To start a new secondary @dfn{user interface} running MI, use the
29009 @code{new-ui} command:
29012 @cindex new user interface
29014 new-ui @var{interpreter} @var{tty}
29017 The @var{interpreter} parameter specifies the interpreter to run.
29018 This accepts the same values as the @code{interpreter-exec} command.
29019 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
29020 @var{tty} parameter specifies the name of the bidirectional file the
29021 interpreter uses for input/output, usually the name of a
29022 pseudoterminal slave on Unix systems. For example:
29025 (@value{GDBP}) new-ui mi /dev/pts/9
29029 runs an MI interpreter on @file{/dev/pts/9}.
29032 @chapter @value{GDBN} Text User Interface
29034 @cindex Text User Interface
29036 The @value{GDBN} Text User Interface (TUI) is a terminal
29037 interface which uses the @code{curses} library to show the source
29038 file, the assembly output, the program registers and @value{GDBN}
29039 commands in separate text windows. The TUI mode is supported only
29040 on platforms where a suitable version of the @code{curses} library
29043 The TUI mode is enabled by default when you invoke @value{GDBN} as
29044 @samp{@value{GDBP} -tui}.
29045 You can also switch in and out of TUI mode while @value{GDBN} runs by
29046 using various TUI commands and key bindings, such as @command{tui
29047 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
29048 @ref{TUI Keys, ,TUI Key Bindings}.
29051 * TUI Overview:: TUI overview
29052 * TUI Keys:: TUI key bindings
29053 * TUI Single Key Mode:: TUI single key mode
29054 * TUI Mouse Support:: TUI mouse support
29055 * TUI Commands:: TUI-specific commands
29056 * TUI Configuration:: TUI configuration variables
29060 @section TUI Overview
29062 In TUI mode, @value{GDBN} can display several text windows:
29066 This window is the @value{GDBN} command window with the @value{GDBN}
29067 prompt and the @value{GDBN} output. The @value{GDBN} input is still
29068 managed using readline.
29071 The source window shows the source file of the program. The current
29072 line and active breakpoints are displayed in this window.
29075 The assembly window shows the disassembly output of the program.
29078 This window shows the processor registers. Registers are highlighted
29079 when their values change.
29082 The source and assembly windows show the current program position
29083 by highlighting the current line and marking it with a @samp{>} marker.
29084 Breakpoints are indicated with two markers. The first marker
29085 indicates the breakpoint type:
29089 Breakpoint which was hit at least once.
29092 Breakpoint which was never hit.
29095 Hardware breakpoint which was hit at least once.
29098 Hardware breakpoint which was never hit.
29101 The second marker indicates whether the breakpoint is enabled or not:
29105 Breakpoint is enabled.
29108 Breakpoint is disabled.
29111 The source, assembly and register windows are updated when the current
29112 thread changes, when the frame changes, or when the program counter
29115 These windows are not all visible at the same time. The command
29116 window is always visible. The others can be arranged in several
29127 source and assembly,
29130 source and registers, or
29133 assembly and registers.
29136 These are the standard layouts, but other layouts can be defined.
29138 A status line above the command window shows the following information:
29142 Indicates the current @value{GDBN} target.
29143 (@pxref{Targets, ,Specifying a Debugging Target}).
29146 Gives the current process or thread number.
29147 When no process is being debugged, this field is set to @code{No process}.
29150 Gives the current function name for the selected frame.
29151 The name is demangled if demangling is turned on (@pxref{Print Settings}).
29152 When there is no symbol corresponding to the current program counter,
29153 the string @code{??} is displayed.
29156 Indicates the current line number for the selected frame.
29157 When the current line number is not known, the string @code{??} is displayed.
29160 Indicates the current program counter address.
29164 @section TUI Key Bindings
29165 @cindex TUI key bindings
29167 The TUI installs several key bindings in the readline keymaps
29168 @ifset SYSTEM_READLINE
29169 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
29171 @ifclear SYSTEM_READLINE
29172 (@pxref{Command Line Editing}).
29174 The following key bindings are installed for both TUI mode and the
29175 @value{GDBN} standard mode.
29184 Enter or leave the TUI mode. When leaving the TUI mode,
29185 the curses window management stops and @value{GDBN} operates using
29186 its standard mode, writing on the terminal directly. When reentering
29187 the TUI mode, control is given back to the curses windows.
29188 The screen is then refreshed.
29190 This key binding uses the bindable Readline function
29191 @code{tui-switch-mode}.
29195 Use a TUI layout with only one window. The layout will
29196 either be @samp{source} or @samp{assembly}. When the TUI mode
29197 is not active, it will switch to the TUI mode.
29199 Think of this key binding as the Emacs @kbd{C-x 1} binding.
29201 This key binding uses the bindable Readline function
29202 @code{tui-delete-other-windows}.
29206 Use a TUI layout with at least two windows. When the current
29207 layout already has two windows, the next layout with two windows is used.
29208 When a new layout is chosen, one window will always be common to the
29209 previous layout and the new one.
29211 Think of it as the Emacs @kbd{C-x 2} binding.
29213 This key binding uses the bindable Readline function
29214 @code{tui-change-windows}.
29218 Change the active window. The TUI associates several key bindings
29219 (like scrolling and arrow keys) with the active window. This command
29220 gives the focus to the next TUI window.
29222 Think of it as the Emacs @kbd{C-x o} binding.
29224 This key binding uses the bindable Readline function
29225 @code{tui-other-window}.
29229 Switch in and out of the TUI SingleKey mode that binds single
29230 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
29232 This key binding uses the bindable Readline function
29233 @code{next-keymap}.
29236 The following key bindings only work in the TUI mode:
29241 Scroll the active window one page up.
29245 Scroll the active window one page down.
29249 Scroll the active window one line up.
29253 Scroll the active window one line down.
29257 Scroll the active window one column left.
29261 Scroll the active window one column right.
29265 Refresh the screen.
29268 Because the arrow keys scroll the active window in the TUI mode, they
29269 are not available for their normal use by readline unless the command
29270 window has the focus. When another window is active, you must use
29271 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
29272 and @kbd{C-f} to control the command window.
29274 @node TUI Single Key Mode
29275 @section TUI Single Key Mode
29276 @cindex TUI single key mode
29278 The TUI also provides a @dfn{SingleKey} mode, which binds several
29279 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
29280 switch into this mode, where the following key bindings are used:
29283 @kindex c @r{(SingleKey TUI key)}
29287 @kindex d @r{(SingleKey TUI key)}
29291 @kindex f @r{(SingleKey TUI key)}
29295 @kindex n @r{(SingleKey TUI key)}
29299 @kindex o @r{(SingleKey TUI key)}
29301 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29303 @kindex q @r{(SingleKey TUI key)}
29305 exit the SingleKey mode.
29307 @kindex r @r{(SingleKey TUI key)}
29311 @kindex s @r{(SingleKey TUI key)}
29315 @kindex i @r{(SingleKey TUI key)}
29317 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29319 @kindex u @r{(SingleKey TUI key)}
29323 @kindex v @r{(SingleKey TUI key)}
29327 @kindex w @r{(SingleKey TUI key)}
29332 Other keys temporarily switch to the @value{GDBN} command prompt.
29333 The key that was pressed is inserted in the editing buffer so that
29334 it is possible to type most @value{GDBN} commands without interaction
29335 with the TUI SingleKey mode. Once the command is entered the TUI
29336 SingleKey mode is restored. The only way to permanently leave
29337 this mode is by typing @kbd{q} or @kbd{C-x s}.
29339 @cindex SingleKey keymap name
29340 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29341 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29342 @file{.inputrc} to add additional bindings to this keymap.
29344 @node TUI Mouse Support
29345 @section TUI Mouse Support
29346 @cindex TUI mouse support
29348 If the curses library supports the mouse, the TUI supports mouse
29351 The mouse wheel scrolls the appropriate window under the mouse cursor.
29353 The TUI itself does not directly support copying/pasting with the
29354 mouse. However, on Unix terminals, you can typically press and hold
29355 the @key{SHIFT} key on your keyboard to temporarily bypass
29356 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29357 functionality (commonly, click-drag-release or double-click to select
29358 text, middle-click to paste). This copy/paste works with the
29359 terminal's selection buffer, as opposed to the TUI's buffer.
29362 @section TUI-specific Commands
29363 @cindex TUI commands
29365 The TUI has specific commands to control the text windows.
29366 These commands are always available, even when @value{GDBN} is not in
29367 the TUI mode. When @value{GDBN} is in the standard mode, most
29368 of these commands will automatically switch to the TUI mode.
29370 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29371 terminal, or @value{GDBN} has been started with the machine interface
29372 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29373 these commands will fail with an error, because it would not be
29374 possible or desirable to enable curses window management.
29379 Activate TUI mode. The last active TUI window layout will be used if
29380 TUI mode has previously been used in the current debugging session,
29381 otherwise a default layout is used.
29384 @kindex tui disable
29385 Disable TUI mode, returning to the console interpreter.
29387 @anchor{info_win_command}
29390 List the names and sizes of all currently displayed windows.
29392 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29393 @kindex tui new-layout
29394 Create a new TUI layout. The new layout will be named @var{name}, and
29395 can be accessed using the @code{layout} command (see below).
29397 Each @var{window} parameter is either the name of a window to display,
29398 or a window description. The windows will be displayed from top to
29399 bottom in the order listed.
29401 The names of the windows are the same as the ones given to the
29402 @code{focus} command (see below); additional, the @code{status}
29403 window can be specified. Note that, because it is of fixed height,
29404 the weight assigned to the status window is of no importance. It is
29405 conventional to use @samp{0} here.
29407 A window description looks a bit like an invocation of @code{tui
29408 new-layout}, and is of the form
29409 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29411 This specifies a sub-layout. If @code{-horizontal} is given, the
29412 windows in this description will be arranged side-by-side, rather than
29415 Each @var{weight} is an integer. It is the weight of this window
29416 relative to all the other windows in the layout. These numbers are
29417 used to calculate how much of the screen is given to each window.
29422 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29425 Here, the new layout is called @samp{example}. It shows the source
29426 and register windows, followed by the status window, and then finally
29427 the command window. The non-status windows all have the same weight,
29428 so the terminal will be split into three roughly equal sections.
29430 Here is a more complex example, showing a horizontal layout:
29433 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29436 This will result in side-by-side source and assembly windows; with the
29437 status and command window being beneath these, filling the entire
29438 width of the terminal. Because they have weight 2, the source and
29439 assembly windows will be twice the height of the command window.
29443 @item tui layout @var{name}
29444 @itemx layout @var{name}
29445 Changes which TUI windows are displayed. The @var{name} parameter
29446 controls which layout is shown. It can be either one of the built-in
29447 layout names, or the name of a layout defined by the user using
29448 @code{tui new-layout}.
29450 The built-in layouts are as follows:
29454 Display the next layout.
29457 Display the previous layout.
29460 Display the source and command windows.
29463 Display the assembly and command windows.
29466 Display the source, assembly, and command windows.
29469 When in @code{src} layout display the register, source, and command
29470 windows. When in @code{asm} or @code{split} layout display the
29471 register, assembler, and command windows.
29475 @item tui focus @var{name}
29476 @itemx focus @var{name}
29477 Changes which TUI window is currently active for scrolling. The
29478 @var{name} parameter can be any of the following:
29482 Make the next window active for scrolling.
29485 Make the previous window active for scrolling.
29488 Make the source window active for scrolling.
29491 Make the assembly window active for scrolling.
29494 Make the register window active for scrolling.
29497 Make the command window active for scrolling.
29500 @kindex tui refresh
29504 Refresh the screen. This is similar to typing @kbd{C-L}.
29506 @item tui reg @var{group}
29508 Changes the register group displayed in the tui register window to
29509 @var{group}. If the register window is not currently displayed this
29510 command will cause the register window to be displayed. The list of
29511 register groups, as well as their order is target specific. The
29512 following groups are available on most targets:
29515 Repeatedly selecting this group will cause the display to cycle
29516 through all of the available register groups.
29519 Repeatedly selecting this group will cause the display to cycle
29520 through all of the available register groups in the reverse order to
29524 Display the general registers.
29526 Display the floating point registers.
29528 Display the system registers.
29530 Display the vector registers.
29532 Display all registers.
29537 Update the source window and the current execution point.
29539 @kindex tui window height
29541 @item tui window height @var{name} +@var{count}
29542 @itemx tui window height @var{name} -@var{count}
29543 @itemx winheight @var{name} +@var{count}
29544 @itemx winheight @var{name} -@var{count}
29545 Change the height of the window @var{name} by @var{count} lines.
29546 Positive counts increase the height, while negative counts decrease
29547 it. The @var{name} parameter can be the name of any currently visible
29548 window. The names of the currently visible windows can be discovered
29549 using @kbd{info win} (@pxref{info_win_command,,info win}).
29551 The set of currently visible windows must always fill the terminal,
29552 and so, it is only possible to resize on window if there are other
29553 visible windows that can either give or receive the extra terminal
29556 @kindex tui window width
29558 @item tui window width @var{name} +@var{count}
29559 @itemx tui window width @var{name} -@var{count}
29560 @itemx winwidth @var{name} +@var{count}
29561 @itemx winwidth @var{name} -@var{count}
29562 Change the width of the window @var{name} by @var{count} columns.
29563 Positive counts increase the width, while negative counts decrease it.
29564 The @var{name} parameter can be the name of any currently visible
29565 window. The names of the currently visible windows can be discovered
29566 using @code{info win} (@pxref{info_win_command,,info win}).
29568 The set of currently visible windows must always fill the terminal,
29569 and so, it is only possible to resize on window if there are other
29570 visible windows that can either give or receive the extra terminal
29574 @node TUI Configuration
29575 @section TUI Configuration Variables
29576 @cindex TUI configuration variables
29578 Several configuration variables control the appearance of TUI windows.
29581 @item set tui border-kind @var{kind}
29582 @kindex set tui border-kind
29583 Select the border appearance for the source, assembly and register windows.
29584 The possible values are the following:
29587 Use a space character to draw the border.
29590 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29593 Use the Alternate Character Set to draw the border. The border is
29594 drawn using character line graphics if the terminal supports them.
29597 @item set tui border-mode @var{mode}
29598 @kindex set tui border-mode
29599 @itemx set tui active-border-mode @var{mode}
29600 @kindex set tui active-border-mode
29601 Select the display attributes for the borders of the inactive windows
29602 or the active window. The @var{mode} can be one of the following:
29605 Use normal attributes to display the border.
29611 Use reverse video mode.
29614 Use half bright mode.
29616 @item half-standout
29617 Use half bright and standout mode.
29620 Use extra bright or bold mode.
29622 @item bold-standout
29623 Use extra bright or bold and standout mode.
29626 @item set tui tab-width @var{nchars}
29627 @kindex set tui tab-width
29629 Set the width of tab stops to be @var{nchars} characters. This
29630 setting affects the display of TAB characters in the source and
29633 @item set tui compact-source @r{[}on@r{|}off@r{]}
29634 @kindex set tui compact-source
29635 Set whether the TUI source window is displayed in ``compact'' form.
29636 The default display uses more space for line numbers and starts the
29637 source text at the next tab stop; the compact display uses only as
29638 much space as is needed for the line numbers in the current file, and
29639 only a single space to separate the line numbers from the source.
29641 @kindex set debug tui
29642 @item set debug tui @r{[}on|off@r{]}
29643 Turn on or off display of @value{GDBN} internal debug messages relating
29646 @kindex show debug tui
29647 @item show debug tui
29648 Show the current status of displaying @value{GDBN} internal debug
29649 messages relating to the TUI.
29653 Note that the colors of the TUI borders can be controlled using the
29654 appropriate @code{set style} commands. @xref{Output Styling}.
29657 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29660 @cindex @sc{gnu} Emacs
29661 A special interface allows you to use @sc{gnu} Emacs to view (and
29662 edit) the source files for the program you are debugging with
29665 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29666 executable file you want to debug as an argument. This command starts
29667 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29668 created Emacs buffer.
29669 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29671 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29676 All ``terminal'' input and output goes through an Emacs buffer, called
29679 This applies both to @value{GDBN} commands and their output, and to the input
29680 and output done by the program you are debugging.
29682 This is useful because it means that you can copy the text of previous
29683 commands and input them again; you can even use parts of the output
29686 All the facilities of Emacs' Shell mode are available for interacting
29687 with your program. In particular, you can send signals the usual
29688 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29692 @value{GDBN} displays source code through Emacs.
29694 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29695 source file for that frame and puts an arrow (@samp{=>}) at the
29696 left margin of the current line. Emacs uses a separate buffer for
29697 source display, and splits the screen to show both your @value{GDBN} session
29700 Explicit @value{GDBN} @code{list} or search commands still produce output as
29701 usual, but you probably have no reason to use them from Emacs.
29704 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29705 a graphical mode, enabled by default, which provides further buffers
29706 that can control the execution and describe the state of your program.
29707 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29709 If you specify an absolute file name when prompted for the @kbd{M-x
29710 gdb} argument, then Emacs sets your current working directory to where
29711 your program resides. If you only specify the file name, then Emacs
29712 sets your current working directory to the directory associated
29713 with the previous buffer. In this case, @value{GDBN} may find your
29714 program by searching your environment's @env{PATH} variable, but on
29715 some operating systems it might not find the source. So, although the
29716 @value{GDBN} input and output session proceeds normally, the auxiliary
29717 buffer does not display the current source and line of execution.
29719 The initial working directory of @value{GDBN} is printed on the top
29720 line of the GUD buffer and this serves as a default for the commands
29721 that specify files for @value{GDBN} to operate on. @xref{Files,
29722 ,Commands to Specify Files}.
29724 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29725 need to call @value{GDBN} by a different name (for example, if you
29726 keep several configurations around, with different names) you can
29727 customize the Emacs variable @code{gud-gdb-command-name} to run the
29730 In the GUD buffer, you can use these special Emacs commands in
29731 addition to the standard Shell mode commands:
29735 Describe the features of Emacs' GUD Mode.
29738 Execute to another source line, like the @value{GDBN} @code{step} command; also
29739 update the display window to show the current file and location.
29742 Execute to next source line in this function, skipping all function
29743 calls, like the @value{GDBN} @code{next} command. Then update the display window
29744 to show the current file and location.
29747 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29748 display window accordingly.
29751 Execute until exit from the selected stack frame, like the @value{GDBN}
29752 @code{finish} command.
29755 Continue execution of your program, like the @value{GDBN} @code{continue}
29759 Go up the number of frames indicated by the numeric argument
29760 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29761 like the @value{GDBN} @code{up} command.
29764 Go down the number of frames indicated by the numeric argument, like the
29765 @value{GDBN} @code{down} command.
29768 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29769 tells @value{GDBN} to set a breakpoint on the source line point is on.
29771 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29772 separate frame which shows a backtrace when the GUD buffer is current.
29773 Move point to any frame in the stack and type @key{RET} to make it
29774 become the current frame and display the associated source in the
29775 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29776 selected frame become the current one. In graphical mode, the
29777 speedbar displays watch expressions.
29779 If you accidentally delete the source-display buffer, an easy way to get
29780 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29781 request a frame display; when you run under Emacs, this recreates
29782 the source buffer if necessary to show you the context of the current
29785 The source files displayed in Emacs are in ordinary Emacs buffers
29786 which are visiting the source files in the usual way. You can edit
29787 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29788 communicates with Emacs in terms of line numbers. If you add or
29789 delete lines from the text, the line numbers that @value{GDBN} knows cease
29790 to correspond properly with the code.
29792 A more detailed description of Emacs' interaction with @value{GDBN} is
29793 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29797 @chapter The @sc{gdb/mi} Interface
29799 @unnumberedsec Function and Purpose
29801 @cindex @sc{gdb/mi}, its purpose
29802 @sc{gdb/mi} is a line based machine oriented text interface to
29803 @value{GDBN} and is activated by specifying using the
29804 @option{--interpreter} command line option (@pxref{Mode Options}). It
29805 is specifically intended to support the development of systems which
29806 use the debugger as just one small component of a larger system.
29808 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29809 in the form of a reference manual.
29811 Note that @sc{gdb/mi} is still under construction, so some of the
29812 features described below are incomplete and subject to change
29813 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29815 @unnumberedsec Notation and Terminology
29817 @cindex notational conventions, for @sc{gdb/mi}
29818 This chapter uses the following notation:
29822 @code{|} separates two alternatives.
29825 @code{[ @var{something} ]} indicates that @var{something} is optional:
29826 it may or may not be given.
29829 @code{( @var{group} )*} means that @var{group} inside the parentheses
29830 may repeat zero or more times.
29833 @code{( @var{group} )+} means that @var{group} inside the parentheses
29834 may repeat one or more times.
29837 @code{"@var{string}"} means a literal @var{string}.
29841 @heading Dependencies
29845 * GDB/MI General Design::
29846 * GDB/MI Command Syntax::
29847 * GDB/MI Compatibility with CLI::
29848 * GDB/MI Development and Front Ends::
29849 * GDB/MI Output Records::
29850 * GDB/MI Simple Examples::
29851 * GDB/MI Command Description Format::
29852 * GDB/MI Breakpoint Commands::
29853 * GDB/MI Catchpoint Commands::
29854 * GDB/MI Program Context::
29855 * GDB/MI Thread Commands::
29856 * GDB/MI Ada Tasking Commands::
29857 * GDB/MI Program Execution::
29858 * GDB/MI Stack Manipulation::
29859 * GDB/MI Variable Objects::
29860 * GDB/MI Data Manipulation::
29861 * GDB/MI Tracepoint Commands::
29862 * GDB/MI Symbol Query::
29863 * GDB/MI File Commands::
29865 * GDB/MI Kod Commands::
29866 * GDB/MI Memory Overlay Commands::
29867 * GDB/MI Signal Handling Commands::
29869 * GDB/MI Target Manipulation::
29870 * GDB/MI File Transfer Commands::
29871 * GDB/MI Ada Exceptions Commands::
29872 * GDB/MI Support Commands::
29873 * GDB/MI Miscellaneous Commands::
29876 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29877 @node GDB/MI General Design
29878 @section @sc{gdb/mi} General Design
29879 @cindex GDB/MI General Design
29881 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29882 parts---commands sent to @value{GDBN}, responses to those commands
29883 and notifications. Each command results in exactly one response,
29884 indicating either successful completion of the command, or an error.
29885 For the commands that do not resume the target, the response contains the
29886 requested information. For the commands that resume the target, the
29887 response only indicates whether the target was successfully resumed.
29888 Notifications is the mechanism for reporting changes in the state of the
29889 target, or in @value{GDBN} state, that cannot conveniently be associated with
29890 a command and reported as part of that command response.
29892 The important examples of notifications are:
29896 Exec notifications. These are used to report changes in
29897 target state---when a target is resumed, or stopped. It would not
29898 be feasible to include this information in response of resuming
29899 commands, because one resume commands can result in multiple events in
29900 different threads. Also, quite some time may pass before any event
29901 happens in the target, while a frontend needs to know whether the resuming
29902 command itself was successfully executed.
29905 Console output, and status notifications. Console output
29906 notifications are used to report output of CLI commands, as well as
29907 diagnostics for other commands. Status notifications are used to
29908 report the progress of a long-running operation. Naturally, including
29909 this information in command response would mean no output is produced
29910 until the command is finished, which is undesirable.
29913 General notifications. Commands may have various side effects on
29914 the @value{GDBN} or target state beyond their official purpose. For example,
29915 a command may change the selected thread. Although such changes can
29916 be included in command response, using notification allows for more
29917 orthogonal frontend design.
29921 There's no guarantee that whenever an MI command reports an error,
29922 @value{GDBN} or the target are in any specific state, and especially,
29923 the state is not reverted to the state before the MI command was
29924 processed. Therefore, whenever an MI command results in an error,
29925 we recommend that the frontend refreshes all the information shown in
29926 the user interface.
29930 * Context management::
29931 * Asynchronous and non-stop modes::
29935 @node Context management
29936 @subsection Context management
29938 @subsubsection Threads and Frames
29940 In most cases when @value{GDBN} accesses the target, this access is
29941 done in context of a specific thread and frame (@pxref{Frames}).
29942 Often, even when accessing global data, the target requires that a thread
29943 be specified. The CLI interface maintains the selected thread and frame,
29944 and supplies them to target on each command. This is convenient,
29945 because a command line user would not want to specify that information
29946 explicitly on each command, and because user interacts with
29947 @value{GDBN} via a single terminal, so no confusion is possible as
29948 to what thread and frame are the current ones.
29950 In the case of MI, the concept of selected thread and frame is less
29951 useful. First, a frontend can easily remember this information
29952 itself. Second, a graphical frontend can have more than one window,
29953 each one used for debugging a different thread, and the frontend might
29954 want to access additional threads for internal purposes. This
29955 increases the risk that by relying on implicitly selected thread, the
29956 frontend may be operating on a wrong one. Therefore, each MI command
29957 should explicitly specify which thread and frame to operate on. To
29958 make it possible, each MI command accepts the @samp{--thread} and
29959 @samp{--frame} options, the value to each is @value{GDBN} global
29960 identifier for thread and frame to operate on.
29962 Usually, each top-level window in a frontend allows the user to select
29963 a thread and a frame, and remembers the user selection for further
29964 operations. However, in some cases @value{GDBN} may suggest that the
29965 current thread or frame be changed. For example, when stopping on a
29966 breakpoint it is reasonable to switch to the thread where breakpoint is
29967 hit. For another example, if the user issues the CLI @samp{thread} or
29968 @samp{frame} commands via the frontend, it is desirable to change the
29969 frontend's selection to the one specified by user. @value{GDBN}
29970 communicates the suggestion to change current thread and frame using the
29971 @samp{=thread-selected} notification.
29973 Note that historically, MI shares the selected thread with CLI, so
29974 frontends used the @code{-thread-select} to execute commands in the
29975 right context. However, getting this to work right is cumbersome. The
29976 simplest way is for frontend to emit @code{-thread-select} command
29977 before every command. This doubles the number of commands that need
29978 to be sent. The alternative approach is to suppress @code{-thread-select}
29979 if the selected thread in @value{GDBN} is supposed to be identical to the
29980 thread the frontend wants to operate on. However, getting this
29981 optimization right can be tricky. In particular, if the frontend
29982 sends several commands to @value{GDBN}, and one of the commands changes the
29983 selected thread, then the behaviour of subsequent commands will
29984 change. So, a frontend should either wait for response from such
29985 problematic commands, or explicitly add @code{-thread-select} for
29986 all subsequent commands. No frontend is known to do this exactly
29987 right, so it is suggested to just always pass the @samp{--thread} and
29988 @samp{--frame} options.
29990 @subsubsection Language
29992 The execution of several commands depends on which language is selected.
29993 By default, the current language (@pxref{show language}) is used.
29994 But for commands known to be language-sensitive, it is recommended
29995 to use the @samp{--language} option. This option takes one argument,
29996 which is the name of the language to use while executing the command.
30000 -data-evaluate-expression --language c "sizeof (void*)"
30005 The valid language names are the same names accepted by the
30006 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
30007 @samp{local} or @samp{unknown}.
30009 @node Asynchronous and non-stop modes
30010 @subsection Asynchronous command execution and non-stop mode
30012 On some targets, @value{GDBN} is capable of processing MI commands
30013 even while the target is running. This is called @dfn{asynchronous
30014 command execution} (@pxref{Background Execution}). The frontend may
30015 specify a preference for asynchronous execution using the
30016 @code{-gdb-set mi-async 1} command, which should be emitted before
30017 either running the executable or attaching to the target. After the
30018 frontend has started the executable or attached to the target, it can
30019 find if asynchronous execution is enabled using the
30020 @code{-list-target-features} command.
30023 @cindex foreground execution
30024 @cindex background execution
30025 @cindex asynchronous execution
30026 @cindex execution, foreground, background and asynchronous
30027 @kindex set mi-async
30028 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
30029 Set whether MI is in asynchronous mode.
30031 When @code{off}, which is the default, MI execution commands (e.g.,
30032 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
30033 for the program to stop before processing further commands.
30035 When @code{on}, MI execution commands are background execution
30036 commands (e.g., @code{-exec-continue} becomes the equivalent of the
30037 @code{c&} CLI command), and so @value{GDBN} is capable of processing
30038 MI commands even while the target is running.
30040 @kindex show mi-async
30041 @item -gdb-show mi-async
30042 Show whether MI asynchronous mode is enabled.
30045 Note: In @value{GDBN} version 7.7 and earlier, this option was called
30046 @code{target-async} instead of @code{mi-async}, and it had the effect
30047 of both putting MI in asynchronous mode and making CLI background
30048 commands possible. CLI background commands are now always possible
30049 ``out of the box'' if the target supports them. The old spelling is
30050 kept as a deprecated alias for backwards compatibility.
30052 Even if @value{GDBN} can accept a command while target is running,
30053 many commands that access the target do not work when the target is
30054 running. Therefore, asynchronous command execution is most useful
30055 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
30056 it is possible to examine the state of one thread, while other threads
30059 When a given thread is running, MI commands that try to access the
30060 target in the context of that thread may not work, or may work only on
30061 some targets. In particular, commands that try to operate on thread's
30062 stack will not work, on any target. Commands that read memory, or
30063 modify breakpoints, may work or not work, depending on the target. Note
30064 that even commands that operate on global state, such as @code{print},
30065 @code{set}, and breakpoint commands, still access the target in the
30066 context of a specific thread, so frontend should try to find a
30067 stopped thread and perform the operation on that thread (using the
30068 @samp{--thread} option).
30070 Which commands will work in the context of a running thread is
30071 highly target dependent. However, the two commands
30072 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
30073 to find the state of a thread, will always work.
30075 @node Thread groups
30076 @subsection Thread groups
30077 @value{GDBN} may be used to debug several processes at the same time.
30078 On some platforms, @value{GDBN} may support debugging of several
30079 hardware systems, each one having several cores with several different
30080 processes running on each core. This section describes the MI
30081 mechanism to support such debugging scenarios.
30083 The key observation is that regardless of the structure of the
30084 target, MI can have a global list of threads, because most commands that
30085 accept the @samp{--thread} option do not need to know what process that
30086 thread belongs to. Therefore, it is not necessary to introduce
30087 neither additional @samp{--process} option, nor an notion of the
30088 current process in the MI interface. The only strictly new feature
30089 that is required is the ability to find how the threads are grouped
30092 To allow the user to discover such grouping, and to support arbitrary
30093 hierarchy of machines/cores/processes, MI introduces the concept of a
30094 @dfn{thread group}. Thread group is a collection of threads and other
30095 thread groups. A thread group always has a string identifier, a type,
30096 and may have additional attributes specific to the type. A new
30097 command, @code{-list-thread-groups}, returns the list of top-level
30098 thread groups, which correspond to processes that @value{GDBN} is
30099 debugging at the moment. By passing an identifier of a thread group
30100 to the @code{-list-thread-groups} command, it is possible to obtain
30101 the members of specific thread group.
30103 To allow the user to easily discover processes, and other objects, he
30104 wishes to debug, a concept of @dfn{available thread group} is
30105 introduced. Available thread group is an thread group that
30106 @value{GDBN} is not debugging, but that can be attached to, using the
30107 @code{-target-attach} command. The list of available top-level thread
30108 groups can be obtained using @samp{-list-thread-groups --available}.
30109 In general, the content of a thread group may be only retrieved only
30110 after attaching to that thread group.
30112 Thread groups are related to inferiors (@pxref{Inferiors Connections and
30113 Programs}). Each inferior corresponds to a thread group of a special
30114 type @samp{process}, and some additional operations are permitted on
30115 such thread groups.
30117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30118 @node GDB/MI Command Syntax
30119 @section @sc{gdb/mi} Command Syntax
30122 * GDB/MI Input Syntax::
30123 * GDB/MI Output Syntax::
30126 @node GDB/MI Input Syntax
30127 @subsection @sc{gdb/mi} Input Syntax
30129 @cindex input syntax for @sc{gdb/mi}
30130 @cindex @sc{gdb/mi}, input syntax
30132 @item @var{command} @expansion{}
30133 @code{@var{cli-command} | @var{mi-command}}
30135 @item @var{cli-command} @expansion{}
30136 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
30137 @var{cli-command} is any existing @value{GDBN} CLI command.
30139 @item @var{mi-command} @expansion{}
30140 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
30141 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
30143 @item @var{token} @expansion{}
30144 "any sequence of digits"
30146 @item @var{option} @expansion{}
30147 @code{"-" @var{parameter} [ " " @var{parameter} ]}
30149 @item @var{parameter} @expansion{}
30150 @code{@var{non-blank-sequence} | @var{c-string}}
30152 @item @var{operation} @expansion{}
30153 @emph{any of the operations described in this chapter}
30155 @item @var{non-blank-sequence} @expansion{}
30156 @emph{anything, provided it doesn't contain special characters such as
30157 "-", @var{nl}, """ and of course " "}
30159 @item @var{c-string} @expansion{}
30160 @code{""" @var{seven-bit-iso-c-string-content} """}
30162 @item @var{nl} @expansion{}
30171 The CLI commands are still handled by the @sc{mi} interpreter; their
30172 output is described below.
30175 The @code{@var{token}}, when present, is passed back when the command
30179 Some @sc{mi} commands accept optional arguments as part of the parameter
30180 list. Each option is identified by a leading @samp{-} (dash) and may be
30181 followed by an optional argument parameter. Options occur first in the
30182 parameter list and can be delimited from normal parameters using
30183 @samp{--} (this is useful when some parameters begin with a dash).
30190 We want easy access to the existing CLI syntax (for debugging).
30193 We want it to be easy to spot a @sc{mi} operation.
30196 @node GDB/MI Output Syntax
30197 @subsection @sc{gdb/mi} Output Syntax
30199 @cindex output syntax of @sc{gdb/mi}
30200 @cindex @sc{gdb/mi}, output syntax
30201 The output from @sc{gdb/mi} consists of zero or more out-of-band records
30202 followed, optionally, by a single result record. This result record
30203 is for the most recent command. The sequence of output records is
30204 terminated by @samp{(gdb)}.
30206 If an input command was prefixed with a @code{@var{token}} then the
30207 corresponding output for that command will also be prefixed by that same
30211 @item @var{output} @expansion{}
30212 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
30214 @item @var{result-record} @expansion{}
30215 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
30217 @item @var{out-of-band-record} @expansion{}
30218 @code{@var{async-record} | @var{stream-record}}
30220 @item @var{async-record} @expansion{}
30221 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
30223 @item @var{exec-async-output} @expansion{}
30224 @code{[ @var{token} ] "*" @var{async-output nl}}
30226 @item @var{status-async-output} @expansion{}
30227 @code{[ @var{token} ] "+" @var{async-output nl}}
30229 @item @var{notify-async-output} @expansion{}
30230 @code{[ @var{token} ] "=" @var{async-output nl}}
30232 @item @var{async-output} @expansion{}
30233 @code{@var{async-class} ( "," @var{result} )*}
30235 @item @var{result-class} @expansion{}
30236 @code{"done" | "running" | "connected" | "error" | "exit"}
30238 @item @var{async-class} @expansion{}
30239 @code{"stopped" | @var{others}} (where @var{others} will be added
30240 depending on the needs---this is still in development).
30242 @item @var{result} @expansion{}
30243 @code{ @var{variable} "=" @var{value}}
30245 @item @var{variable} @expansion{}
30246 @code{ @var{string} }
30248 @item @var{value} @expansion{}
30249 @code{ @var{const} | @var{tuple} | @var{list} }
30251 @item @var{const} @expansion{}
30252 @code{@var{c-string}}
30254 @item @var{tuple} @expansion{}
30255 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
30257 @item @var{list} @expansion{}
30258 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
30259 @var{result} ( "," @var{result} )* "]" }
30261 @item @var{stream-record} @expansion{}
30262 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
30264 @item @var{console-stream-output} @expansion{}
30265 @code{"~" @var{c-string nl}}
30267 @item @var{target-stream-output} @expansion{}
30268 @code{"@@" @var{c-string nl}}
30270 @item @var{log-stream-output} @expansion{}
30271 @code{"&" @var{c-string nl}}
30273 @item @var{nl} @expansion{}
30276 @item @var{token} @expansion{}
30277 @emph{any sequence of digits}.
30285 All output sequences end in a single line containing a period.
30288 The @code{@var{token}} is from the corresponding request. Note that
30289 for all async output, while the token is allowed by the grammar and
30290 may be output by future versions of @value{GDBN} for select async
30291 output messages, it is generally omitted. Frontends should treat
30292 all async output as reporting general changes in the state of the
30293 target and there should be no need to associate async output to any
30297 @cindex status output in @sc{gdb/mi}
30298 @var{status-async-output} contains on-going status information about the
30299 progress of a slow operation. It can be discarded. All status output is
30300 prefixed by @samp{+}.
30303 @cindex async output in @sc{gdb/mi}
30304 @var{exec-async-output} contains asynchronous state change on the target
30305 (stopped, started, disappeared). All async output is prefixed by
30309 @cindex notify output in @sc{gdb/mi}
30310 @var{notify-async-output} contains supplementary information that the
30311 client should handle (e.g., a new breakpoint information). All notify
30312 output is prefixed by @samp{=}.
30315 @cindex console output in @sc{gdb/mi}
30316 @var{console-stream-output} is output that should be displayed as is in the
30317 console. It is the textual response to a CLI command. All the console
30318 output is prefixed by @samp{~}.
30321 @cindex target output in @sc{gdb/mi}
30322 @var{target-stream-output} is the output produced by the target program.
30323 All the target output is prefixed by @samp{@@}.
30326 @cindex log output in @sc{gdb/mi}
30327 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30328 instance messages that should be displayed as part of an error log. All
30329 the log output is prefixed by @samp{&}.
30332 @cindex list output in @sc{gdb/mi}
30333 New @sc{gdb/mi} commands should only output @var{lists} containing
30339 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30340 details about the various output records.
30342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30343 @node GDB/MI Compatibility with CLI
30344 @section @sc{gdb/mi} Compatibility with CLI
30346 @cindex compatibility, @sc{gdb/mi} and CLI
30347 @cindex @sc{gdb/mi}, compatibility with CLI
30349 For the developers convenience CLI commands can be entered directly,
30350 but there may be some unexpected behaviour. For example, commands
30351 that query the user will behave as if the user replied yes, breakpoint
30352 command lists are not executed and some CLI commands, such as
30353 @code{if}, @code{when} and @code{define}, prompt for further input with
30354 @samp{>}, which is not valid MI output.
30356 This feature may be removed at some stage in the future and it is
30357 recommended that front ends use the @code{-interpreter-exec} command
30358 (@pxref{-interpreter-exec}).
30360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30361 @node GDB/MI Development and Front Ends
30362 @section @sc{gdb/mi} Development and Front Ends
30363 @cindex @sc{gdb/mi} development
30365 The application which takes the MI output and presents the state of the
30366 program being debugged to the user is called a @dfn{front end}.
30368 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30369 to the MI interface may break existing usage. This section describes how the
30370 protocol changes and how to request previous version of the protocol when it
30373 Some changes in MI need not break a carefully designed front end, and
30374 for these the MI version will remain unchanged. The following is a
30375 list of changes that may occur within one level, so front ends should
30376 parse MI output in a way that can handle them:
30380 New MI commands may be added.
30383 New fields may be added to the output of any MI command.
30386 The range of values for fields with specified values, e.g.,
30387 @code{in_scope} (@pxref{-var-update}) may be extended.
30389 @c The format of field's content e.g type prefix, may change so parse it
30390 @c at your own risk. Yes, in general?
30392 @c The order of fields may change? Shouldn't really matter but it might
30393 @c resolve inconsistencies.
30396 If the changes are likely to break front ends, the MI version level
30397 will be increased by one. The new versions of the MI protocol are not compatible
30398 with the old versions. Old versions of MI remain available, allowing front ends
30399 to keep using them until they are modified to use the latest MI version.
30401 Since @code{--interpreter=mi} always points to the latest MI version, it is
30402 recommended that front ends request a specific version of MI when launching
30403 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30404 interpreter with the MI version they expect.
30406 The following table gives a summary of the released versions of the MI
30407 interface: the version number, the version of GDB in which it first appeared
30408 and the breaking changes compared to the previous version.
30410 @multitable @columnfractions .1 .1 .8
30411 @headitem MI version @tab GDB version @tab Breaking changes
30428 The @code{-environment-pwd}, @code{-environment-directory} and
30429 @code{-environment-path} commands now returns values using the MI output
30430 syntax, rather than CLI output syntax.
30433 @code{-var-list-children}'s @code{children} result field is now a list, rather
30437 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30449 The output of information about multi-location breakpoints has changed in the
30450 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30451 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30452 The multiple locations are now placed in a @code{locations} field, whose value
30458 If your front end cannot yet migrate to a more recent version of the
30459 MI protocol, you can nevertheless selectively enable specific features
30460 available in those recent MI versions, using the following commands:
30464 @item -fix-multi-location-breakpoint-output
30465 Use the output for multi-location breakpoints which was introduced by
30466 MI 3, even when using MI versions 2 or 1. This command has no
30467 effect when using MI version 3 or later.
30471 The best way to avoid unexpected changes in MI that might break your front
30472 end is to make your project known to @value{GDBN} developers and
30473 follow development on @email{gdb@@sourceware.org} and
30474 @email{gdb-patches@@sourceware.org}.
30475 @cindex mailing lists
30477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30478 @node GDB/MI Output Records
30479 @section @sc{gdb/mi} Output Records
30482 * GDB/MI Result Records::
30483 * GDB/MI Stream Records::
30484 * GDB/MI Async Records::
30485 * GDB/MI Breakpoint Information::
30486 * GDB/MI Frame Information::
30487 * GDB/MI Thread Information::
30488 * GDB/MI Ada Exception Information::
30491 @node GDB/MI Result Records
30492 @subsection @sc{gdb/mi} Result Records
30494 @cindex result records in @sc{gdb/mi}
30495 @cindex @sc{gdb/mi}, result records
30496 In addition to a number of out-of-band notifications, the response to a
30497 @sc{gdb/mi} command includes one of the following result indications:
30501 @item "^done" [ "," @var{results} ]
30502 The synchronous operation was successful, @code{@var{results}} are the return
30507 This result record is equivalent to @samp{^done}. Historically, it
30508 was output instead of @samp{^done} if the command has resumed the
30509 target. This behaviour is maintained for backward compatibility, but
30510 all frontends should treat @samp{^done} and @samp{^running}
30511 identically and rely on the @samp{*running} output record to determine
30512 which threads are resumed.
30516 @value{GDBN} has connected to a remote target.
30518 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30520 The operation failed. The @code{msg=@var{c-string}} variable contains
30521 the corresponding error message.
30523 If present, the @code{code=@var{c-string}} variable provides an error
30524 code on which consumers can rely on to detect the corresponding
30525 error condition. At present, only one error code is defined:
30528 @item "undefined-command"
30529 Indicates that the command causing the error does not exist.
30534 @value{GDBN} has terminated.
30538 @node GDB/MI Stream Records
30539 @subsection @sc{gdb/mi} Stream Records
30541 @cindex @sc{gdb/mi}, stream records
30542 @cindex stream records in @sc{gdb/mi}
30543 @value{GDBN} internally maintains a number of output streams: the console, the
30544 target, and the log. The output intended for each of these streams is
30545 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30547 Each stream record begins with a unique @dfn{prefix character} which
30548 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30549 Syntax}). In addition to the prefix, each stream record contains a
30550 @code{@var{string-output}}. This is either raw text (with an implicit new
30551 line) or a quoted C string (which does not contain an implicit newline).
30554 @item "~" @var{string-output}
30555 The console output stream contains text that should be displayed in the
30556 CLI console window. It contains the textual responses to CLI commands.
30558 @item "@@" @var{string-output}
30559 The target output stream contains any textual output from the running
30560 target. This is only present when GDB's event loop is truly
30561 asynchronous, which is currently only the case for remote targets.
30563 @item "&" @var{string-output}
30564 The log stream contains debugging messages being produced by @value{GDBN}'s
30568 @node GDB/MI Async Records
30569 @subsection @sc{gdb/mi} Async Records
30571 @cindex async records in @sc{gdb/mi}
30572 @cindex @sc{gdb/mi}, async records
30573 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30574 additional changes that have occurred. Those changes can either be a
30575 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30576 target activity (e.g., target stopped).
30578 The following is the list of possible async records:
30582 @item *running,thread-id="@var{thread}"
30583 The target is now running. The @var{thread} field can be the global
30584 thread ID of the thread that is now running, and it can be
30585 @samp{all} if all threads are running. The frontend should assume
30586 that no interaction with a running thread is possible after this
30587 notification is produced. The frontend should not assume that this
30588 notification is output only once for any command. @value{GDBN} may
30589 emit this notification several times, either for different threads,
30590 because it cannot resume all threads together, or even for a single
30591 thread, if the thread must be stepped though some code before letting
30594 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30595 The target has stopped. The @var{reason} field can have one of the
30599 @item breakpoint-hit
30600 A breakpoint was reached.
30601 @item watchpoint-trigger
30602 A watchpoint was triggered.
30603 @item read-watchpoint-trigger
30604 A read watchpoint was triggered.
30605 @item access-watchpoint-trigger
30606 An access watchpoint was triggered.
30607 @item function-finished
30608 An -exec-finish or similar CLI command was accomplished.
30609 @item location-reached
30610 An -exec-until or similar CLI command was accomplished.
30611 @item watchpoint-scope
30612 A watchpoint has gone out of scope.
30613 @item end-stepping-range
30614 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30615 similar CLI command was accomplished.
30616 @item exited-signalled
30617 The inferior exited because of a signal.
30619 The inferior exited.
30620 @item exited-normally
30621 The inferior exited normally.
30622 @item signal-received
30623 A signal was received by the inferior.
30625 The inferior has stopped due to a library being loaded or unloaded.
30626 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30627 set or when a @code{catch load} or @code{catch unload} catchpoint is
30628 in use (@pxref{Set Catchpoints}).
30630 The inferior has forked. This is reported when @code{catch fork}
30631 (@pxref{Set Catchpoints}) has been used.
30633 The inferior has vforked. This is reported in when @code{catch vfork}
30634 (@pxref{Set Catchpoints}) has been used.
30635 @item syscall-entry
30636 The inferior entered a system call. This is reported when @code{catch
30637 syscall} (@pxref{Set Catchpoints}) has been used.
30638 @item syscall-return
30639 The inferior returned from a system call. This is reported when
30640 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30642 The inferior called @code{exec}. This is reported when @code{catch exec}
30643 (@pxref{Set Catchpoints}) has been used.
30646 The @var{id} field identifies the global thread ID of the thread
30647 that directly caused the stop -- for example by hitting a breakpoint.
30648 Depending on whether all-stop
30649 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30650 stop all threads, or only the thread that directly triggered the stop.
30651 If all threads are stopped, the @var{stopped} field will have the
30652 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30653 field will be a list of thread identifiers. Presently, this list will
30654 always include a single thread, but frontend should be prepared to see
30655 several threads in the list. The @var{core} field reports the
30656 processor core on which the stop event has happened. This field may be absent
30657 if such information is not available.
30659 @item =thread-group-added,id="@var{id}"
30660 @itemx =thread-group-removed,id="@var{id}"
30661 A thread group was either added or removed. The @var{id} field
30662 contains the @value{GDBN} identifier of the thread group. When a thread
30663 group is added, it generally might not be associated with a running
30664 process. When a thread group is removed, its id becomes invalid and
30665 cannot be used in any way.
30667 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30668 A thread group became associated with a running program,
30669 either because the program was just started or the thread group
30670 was attached to a program. The @var{id} field contains the
30671 @value{GDBN} identifier of the thread group. The @var{pid} field
30672 contains process identifier, specific to the operating system.
30674 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30675 A thread group is no longer associated with a running program,
30676 either because the program has exited, or because it was detached
30677 from. The @var{id} field contains the @value{GDBN} identifier of the
30678 thread group. The @var{code} field is the exit code of the inferior; it exists
30679 only when the inferior exited with some code.
30681 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30682 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30683 A thread either was created, or has exited. The @var{id} field
30684 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30685 field identifies the thread group this thread belongs to.
30687 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30688 Informs that the selected thread or frame were changed. This notification
30689 is not emitted as result of the @code{-thread-select} or
30690 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30691 that is not documented to change the selected thread and frame actually
30692 changes them. In particular, invoking, directly or indirectly
30693 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30694 will generate this notification. Changing the thread or frame from another
30695 user interface (see @ref{Interpreters}) will also generate this notification.
30697 The @var{frame} field is only present if the newly selected thread is
30698 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30700 We suggest that in response to this notification, front ends
30701 highlight the selected thread and cause subsequent commands to apply to
30704 @item =library-loaded,...
30705 Reports that a new library file was loaded by the program. This
30706 notification has 5 fields---@var{id}, @var{target-name},
30707 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30708 opaque identifier of the library. For remote debugging case,
30709 @var{target-name} and @var{host-name} fields give the name of the
30710 library file on the target, and on the host respectively. For native
30711 debugging, both those fields have the same value. The
30712 @var{symbols-loaded} field is emitted only for backward compatibility
30713 and should not be relied on to convey any useful information. The
30714 @var{thread-group} field, if present, specifies the id of the thread
30715 group in whose context the library was loaded. If the field is
30716 absent, it means the library was loaded in the context of all present
30717 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30720 @item =library-unloaded,...
30721 Reports that a library was unloaded by the program. This notification
30722 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30723 the same meaning as for the @code{=library-loaded} notification.
30724 The @var{thread-group} field, if present, specifies the id of the
30725 thread group in whose context the library was unloaded. If the field is
30726 absent, it means the library was unloaded in the context of all present
30729 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30730 @itemx =traceframe-changed,end
30731 Reports that the trace frame was changed and its new number is
30732 @var{tfnum}. The number of the tracepoint associated with this trace
30733 frame is @var{tpnum}.
30735 @item =tsv-created,name=@var{name},initial=@var{initial}
30736 Reports that the new trace state variable @var{name} is created with
30737 initial value @var{initial}.
30739 @item =tsv-deleted,name=@var{name}
30740 @itemx =tsv-deleted
30741 Reports that the trace state variable @var{name} is deleted or all
30742 trace state variables are deleted.
30744 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30745 Reports that the trace state variable @var{name} is modified with
30746 the initial value @var{initial}. The current value @var{current} of
30747 trace state variable is optional and is reported if the current
30748 value of trace state variable is known.
30750 @item =breakpoint-created,bkpt=@{...@}
30751 @itemx =breakpoint-modified,bkpt=@{...@}
30752 @itemx =breakpoint-deleted,id=@var{number}
30753 Reports that a breakpoint was created, modified, or deleted,
30754 respectively. Only user-visible breakpoints are reported to the MI
30757 The @var{bkpt} argument is of the same form as returned by the various
30758 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30759 @var{number} is the ordinal number of the breakpoint.
30761 Note that if a breakpoint is emitted in the result record of a
30762 command, then it will not also be emitted in an async record.
30764 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30765 @itemx =record-stopped,thread-group="@var{id}"
30766 Execution log recording was either started or stopped on an
30767 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30768 group corresponding to the affected inferior.
30770 The @var{method} field indicates the method used to record execution. If the
30771 method in use supports multiple recording formats, @var{format} will be present
30772 and contain the currently used format. @xref{Process Record and Replay},
30773 for existing method and format values.
30775 @item =cmd-param-changed,param=@var{param},value=@var{value}
30776 Reports that a parameter of the command @code{set @var{param}} is
30777 changed to @var{value}. In the multi-word @code{set} command,
30778 the @var{param} is the whole parameter list to @code{set} command.
30779 For example, In command @code{set check type on}, @var{param}
30780 is @code{check type} and @var{value} is @code{on}.
30782 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30783 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30784 written in an inferior. The @var{id} is the identifier of the
30785 thread group corresponding to the affected inferior. The optional
30786 @code{type="code"} part is reported if the memory written to holds
30790 @node GDB/MI Breakpoint Information
30791 @subsection @sc{gdb/mi} Breakpoint Information
30793 When @value{GDBN} reports information about a breakpoint, a
30794 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30799 The breakpoint number.
30802 The type of the breakpoint. For ordinary breakpoints this will be
30803 @samp{breakpoint}, but many values are possible.
30806 If the type of the breakpoint is @samp{catchpoint}, then this
30807 indicates the exact type of catchpoint.
30810 This is the breakpoint disposition---either @samp{del}, meaning that
30811 the breakpoint will be deleted at the next stop, or @samp{keep},
30812 meaning that the breakpoint will not be deleted.
30815 This indicates whether the breakpoint is enabled, in which case the
30816 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30817 Note that this is not the same as the field @code{enable}.
30820 The address of the breakpoint. This may be a hexidecimal number,
30821 giving the address; or the string @samp{<PENDING>}, for a pending
30822 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30823 multiple locations. This field will not be present if no address can
30824 be determined. For example, a watchpoint does not have an address.
30827 Optional field containing any flags related to the address. These flags are
30828 architecture-dependent; see @ref{Architectures} for their meaning for a
30832 If known, the function in which the breakpoint appears.
30833 If not known, this field is not present.
30836 The name of the source file which contains this function, if known.
30837 If not known, this field is not present.
30840 The full file name of the source file which contains this function, if
30841 known. If not known, this field is not present.
30844 The line number at which this breakpoint appears, if known.
30845 If not known, this field is not present.
30848 If the source file is not known, this field may be provided. If
30849 provided, this holds the address of the breakpoint, possibly followed
30853 If this breakpoint is pending, this field is present and holds the
30854 text used to set the breakpoint, as entered by the user.
30857 Where this breakpoint's condition is evaluated, either @samp{host} or
30861 If this is a thread-specific breakpoint, then this identifies the
30862 thread in which the breakpoint can trigger.
30865 If this breakpoint is restricted to a particular Ada task, then this
30866 field will hold the task identifier.
30869 If the breakpoint is conditional, this is the condition expression.
30872 The ignore count of the breakpoint.
30875 The enable count of the breakpoint.
30877 @item traceframe-usage
30880 @item static-tracepoint-marker-string-id
30881 For a static tracepoint, the name of the static tracepoint marker.
30884 For a masked watchpoint, this is the mask.
30887 A tracepoint's pass count.
30889 @item original-location
30890 The location of the breakpoint as originally specified by the user.
30891 This field is optional.
30894 The number of times the breakpoint has been hit.
30897 This field is only given for tracepoints. This is either @samp{y},
30898 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30902 Some extra data, the exact contents of which are type-dependent.
30905 This field is present if the breakpoint has multiple locations. It is also
30906 exceptionally present if the breakpoint is enabled and has a single, disabled
30909 The value is a list of locations. The format of a location is described below.
30913 A location in a multi-location breakpoint is represented as a tuple with the
30919 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30920 number of the parent breakpoint. The second digit is the number of the
30921 location within that breakpoint.
30924 There are three possible values, with the following meanings:
30927 The location is enabled.
30929 The location is disabled by the user.
30931 The location is disabled because the breakpoint condition is invalid
30936 The address of this location as an hexidecimal number.
30939 Optional field containing any flags related to the address. These flags are
30940 architecture-dependent; see @ref{Architectures} for their meaning for a
30944 If known, the function in which the location appears.
30945 If not known, this field is not present.
30948 The name of the source file which contains this location, if known.
30949 If not known, this field is not present.
30952 The full file name of the source file which contains this location, if
30953 known. If not known, this field is not present.
30956 The line number at which this location appears, if known.
30957 If not known, this field is not present.
30959 @item thread-groups
30960 The thread groups this location is in.
30964 For example, here is what the output of @code{-break-insert}
30965 (@pxref{GDB/MI Breakpoint Commands}) might be:
30968 -> -break-insert main
30969 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30970 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30971 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30976 @node GDB/MI Frame Information
30977 @subsection @sc{gdb/mi} Frame Information
30979 Response from many MI commands includes an information about stack
30980 frame. This information is a tuple that may have the following
30985 The level of the stack frame. The innermost frame has the level of
30986 zero. This field is always present.
30989 The name of the function corresponding to the frame. This field may
30990 be absent if @value{GDBN} is unable to determine the function name.
30993 The code address for the frame. This field is always present.
30996 Optional field containing any flags related to the address. These flags are
30997 architecture-dependent; see @ref{Architectures} for their meaning for a
31001 The name of the source files that correspond to the frame's code
31002 address. This field may be absent.
31005 The source line corresponding to the frames' code address. This field
31009 The name of the binary file (either executable or shared library) the
31010 corresponds to the frame's code address. This field may be absent.
31014 @node GDB/MI Thread Information
31015 @subsection @sc{gdb/mi} Thread Information
31017 Whenever @value{GDBN} has to report an information about a thread, it
31018 uses a tuple with the following fields. The fields are always present unless
31023 The global numeric id assigned to the thread by @value{GDBN}.
31026 The target-specific string identifying the thread.
31029 Additional information about the thread provided by the target.
31030 It is supposed to be human-readable and not interpreted by the
31031 frontend. This field is optional.
31034 The name of the thread. If the user specified a name using the
31035 @code{thread name} command, then this name is given. Otherwise, if
31036 @value{GDBN} can extract the thread name from the target, then that
31037 name is given. If @value{GDBN} cannot find the thread name, then this
31041 The execution state of the thread, either @samp{stopped} or @samp{running},
31042 depending on whether the thread is presently running.
31045 The stack frame currently executing in the thread. This field is only present
31046 if the thread is stopped. Its format is documented in
31047 @ref{GDB/MI Frame Information}.
31050 The value of this field is an integer number of the processor core the
31051 thread was last seen on. This field is optional.
31054 @node GDB/MI Ada Exception Information
31055 @subsection @sc{gdb/mi} Ada Exception Information
31057 Whenever a @code{*stopped} record is emitted because the program
31058 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
31059 @value{GDBN} provides the name of the exception that was raised via
31060 the @code{exception-name} field. Also, for exceptions that were raised
31061 with an exception message, @value{GDBN} provides that message via
31062 the @code{exception-message} field.
31064 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31065 @node GDB/MI Simple Examples
31066 @section Simple Examples of @sc{gdb/mi} Interaction
31067 @cindex @sc{gdb/mi}, simple examples
31069 This subsection presents several simple examples of interaction using
31070 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
31071 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
31072 the output received from @sc{gdb/mi}.
31074 Note the line breaks shown in the examples are here only for
31075 readability, they don't appear in the real output.
31077 @subheading Setting a Breakpoint
31079 Setting a breakpoint generates synchronous output which contains detailed
31080 information of the breakpoint.
31083 -> -break-insert main
31084 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31085 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31086 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31091 @subheading Program Execution
31093 Program execution generates asynchronous records and MI gives the
31094 reason that execution stopped.
31100 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31101 frame=@{addr="0x08048564",func="main",
31102 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
31103 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
31104 arch="i386:x86_64"@}
31109 <- *stopped,reason="exited-normally"
31113 @subheading Quitting @value{GDBN}
31115 Quitting @value{GDBN} just prints the result class @samp{^exit}.
31123 Please note that @samp{^exit} is printed immediately, but it might
31124 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
31125 performs necessary cleanups, including killing programs being debugged
31126 or disconnecting from debug hardware, so the frontend should wait till
31127 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
31128 fails to exit in reasonable time.
31130 @subheading A Bad Command
31132 Here's what happens if you pass a non-existent command:
31136 <- ^error,msg="Undefined MI command: rubbish"
31141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31142 @node GDB/MI Command Description Format
31143 @section @sc{gdb/mi} Command Description Format
31145 The remaining sections describe blocks of commands. Each block of
31146 commands is laid out in a fashion similar to this section.
31148 @subheading Motivation
31150 The motivation for this collection of commands.
31152 @subheading Introduction
31154 A brief introduction to this collection of commands as a whole.
31156 @subheading Commands
31158 For each command in the block, the following is described:
31160 @subsubheading Synopsis
31163 -command @var{args}@dots{}
31166 @subsubheading Result
31168 @subsubheading @value{GDBN} Command
31170 The corresponding @value{GDBN} CLI command(s), if any.
31172 @subsubheading Example
31174 Example(s) formatted for readability. Some of the described commands have
31175 not been implemented yet and these are labeled N.A.@: (not available).
31178 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31179 @node GDB/MI Breakpoint Commands
31180 @section @sc{gdb/mi} Breakpoint Commands
31182 @cindex breakpoint commands for @sc{gdb/mi}
31183 @cindex @sc{gdb/mi}, breakpoint commands
31184 This section documents @sc{gdb/mi} commands for manipulating
31187 @subheading The @code{-break-after} Command
31188 @findex -break-after
31190 @subsubheading Synopsis
31193 -break-after @var{number} @var{count}
31196 The breakpoint number @var{number} is not in effect until it has been
31197 hit @var{count} times. To see how this is reflected in the output of
31198 the @samp{-break-list} command, see the description of the
31199 @samp{-break-list} command below.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{ignore}.
31205 @subsubheading Example
31210 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31211 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31212 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31220 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31221 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31222 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31223 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31224 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31225 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31226 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31227 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31228 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31229 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
31234 @subheading The @code{-break-catch} Command
31235 @findex -break-catch
31238 @subheading The @code{-break-commands} Command
31239 @findex -break-commands
31241 @subsubheading Synopsis
31244 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
31247 Specifies the CLI commands that should be executed when breakpoint
31248 @var{number} is hit. The parameters @var{command1} to @var{commandN}
31249 are the commands. If no command is specified, any previously-set
31250 commands are cleared. @xref{Break Commands}. Typical use of this
31251 functionality is tracing a program, that is, printing of values of
31252 some variables whenever breakpoint is hit and then continuing.
31254 @subsubheading @value{GDBN} Command
31256 The corresponding @value{GDBN} command is @samp{commands}.
31258 @subsubheading Example
31263 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31264 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31265 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31268 -break-commands 1 "print v" "continue"
31273 @subheading The @code{-break-condition} Command
31274 @findex -break-condition
31276 @subsubheading Synopsis
31279 -break-condition [ --force ] @var{number} [ @var{expr} ]
31282 Breakpoint @var{number} will stop the program only if the condition in
31283 @var{expr} is true. The condition becomes part of the
31284 @samp{-break-list} output (see the description of the @samp{-break-list}
31285 command below). If the @samp{--force} flag is passed, the condition
31286 is forcibly defined even when it is invalid for all locations of
31287 breakpoint @var{number}. If the @var{expr} argument is omitted,
31288 breakpoint @var{number} becomes unconditional.
31290 @subsubheading @value{GDBN} Command
31292 The corresponding @value{GDBN} command is @samp{condition}.
31294 @subsubheading Example
31298 -break-condition 1 1
31302 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31303 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31304 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31305 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31306 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31307 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31308 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31309 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31310 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31311 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31315 @subheading The @code{-break-delete} Command
31316 @findex -break-delete
31318 @subsubheading Synopsis
31321 -break-delete ( @var{breakpoint} )+
31324 Delete the breakpoint(s) whose number(s) are specified in the argument
31325 list. This is obviously reflected in the breakpoint list.
31327 @subsubheading @value{GDBN} Command
31329 The corresponding @value{GDBN} command is @samp{delete}.
31331 @subsubheading Example
31339 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31340 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31341 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31342 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31343 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31344 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31345 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31350 @subheading The @code{-break-disable} Command
31351 @findex -break-disable
31353 @subsubheading Synopsis
31356 -break-disable ( @var{breakpoint} )+
31359 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31360 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31362 @subsubheading @value{GDBN} Command
31364 The corresponding @value{GDBN} command is @samp{disable}.
31366 @subsubheading Example
31374 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31375 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31376 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31377 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31378 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31379 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31380 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31381 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31382 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31383 line="5",thread-groups=["i1"],times="0"@}]@}
31387 @subheading The @code{-break-enable} Command
31388 @findex -break-enable
31390 @subsubheading Synopsis
31393 -break-enable ( @var{breakpoint} )+
31396 Enable (previously disabled) @var{breakpoint}(s).
31398 @subsubheading @value{GDBN} Command
31400 The corresponding @value{GDBN} command is @samp{enable}.
31402 @subsubheading Example
31410 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31411 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31412 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31413 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31414 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31415 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31416 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31417 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31418 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31419 line="5",thread-groups=["i1"],times="0"@}]@}
31423 @subheading The @code{-break-info} Command
31424 @findex -break-info
31426 @subsubheading Synopsis
31429 -break-info @var{breakpoint}
31433 Get information about a single breakpoint.
31435 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31436 Information}, for details on the format of each breakpoint in the
31439 @subsubheading @value{GDBN} Command
31441 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31443 @subsubheading Example
31446 @subheading The @code{-break-insert} Command
31447 @findex -break-insert
31448 @anchor{-break-insert}
31450 @subsubheading Synopsis
31453 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31454 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31455 [ -p @var{thread-id} ] [ @var{locspec} ]
31459 If specified, @var{locspec}, can be one of:
31462 @item linespec location
31463 A linespec location. @xref{Linespec Locations}.
31465 @item explicit location
31466 An explicit location. @sc{gdb/mi} explicit locations are
31467 analogous to the CLI's explicit locations using the option names
31468 listed below. @xref{Explicit Locations}.
31471 @item --source @var{filename}
31472 The source file name of the location. This option requires the use
31473 of either @samp{--function} or @samp{--line}.
31475 @item --function @var{function}
31476 The name of a function or method.
31478 @item --label @var{label}
31479 The name of a label.
31481 @item --line @var{lineoffset}
31482 An absolute or relative line offset from the start of the location.
31485 @item address location
31486 An address location, *@var{address}. @xref{Address Locations}.
31490 The possible optional parameters of this command are:
31494 Insert a temporary breakpoint.
31496 Insert a hardware breakpoint.
31498 If @var{locspec} cannot be resolved (for example if it
31499 refers to unknown files or functions), create a pending
31500 breakpoint. Without this flag, @value{GDBN} will report
31501 an error, and won't create a breakpoint, if @var{locspec}
31504 Create a disabled breakpoint.
31506 Create a tracepoint. @xref{Tracepoints}. When this parameter
31507 is used together with @samp{-h}, a fast tracepoint is created.
31508 @item -c @var{condition}
31509 Make the breakpoint conditional on @var{condition}.
31510 @item --force-condition
31511 Forcibly define the breakpoint even if the condition is invalid at
31512 all of the breakpoint locations.
31513 @item -i @var{ignore-count}
31514 Initialize the @var{ignore-count}.
31515 @item -p @var{thread-id}
31516 Restrict the breakpoint to the thread with the specified global
31519 This option makes @value{GDBN} interpret a function name specified as
31520 a complete fully-qualified name.
31523 @subsubheading Result
31525 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31526 resulting breakpoint.
31528 Note: this format is open to change.
31529 @c An out-of-band breakpoint instead of part of the result?
31531 @subsubheading @value{GDBN} Command
31533 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31534 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31536 @subsubheading Example
31541 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31542 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31545 -break-insert -t foo
31546 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31547 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31551 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31552 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31553 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31554 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31555 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31556 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31557 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31558 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31559 addr="0x0001072c", func="main",file="recursive2.c",
31560 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31562 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31563 addr="0x00010774",func="foo",file="recursive2.c",
31564 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31569 @subheading The @code{-dprintf-insert} Command
31570 @findex -dprintf-insert
31572 @subsubheading Synopsis
31575 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31576 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31577 [ -p @var{thread-id} ] [ @var{locspec} ] [ @var{format} ]
31582 If supplied, @var{locspec} and @code{--qualified} may be specified
31583 the same way as for the @code{-break-insert} command.
31584 @xref{-break-insert}.
31586 The possible optional parameters of this command are:
31590 Insert a temporary breakpoint.
31592 If @var{locspec} cannot be parsed (for example, if it
31593 refers to unknown files or functions), create a pending
31594 breakpoint. Without this flag, @value{GDBN} will report
31595 an error, and won't create a breakpoint, if @var{locspec}
31598 Create a disabled breakpoint.
31599 @item -c @var{condition}
31600 Make the breakpoint conditional on @var{condition}.
31601 @item --force-condition
31602 Forcibly define the breakpoint even if the condition is invalid at
31603 all of the breakpoint locations.
31604 @item -i @var{ignore-count}
31605 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31606 to @var{ignore-count}.
31607 @item -p @var{thread-id}
31608 Restrict the breakpoint to the thread with the specified global
31612 @subsubheading Result
31614 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31615 resulting breakpoint.
31617 @c An out-of-band breakpoint instead of part of the result?
31619 @subsubheading @value{GDBN} Command
31621 The corresponding @value{GDBN} command is @samp{dprintf}.
31623 @subsubheading Example
31627 4-dprintf-insert foo "At foo entry\n"
31628 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31629 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31630 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31631 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31632 original-location="foo"@}
31634 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31635 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31636 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31637 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31638 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31639 original-location="mi-dprintf.c:26"@}
31643 @subheading The @code{-break-list} Command
31644 @findex -break-list
31646 @subsubheading Synopsis
31652 Displays the list of inserted breakpoints, showing the following fields:
31656 number of the breakpoint
31658 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31660 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31663 is the breakpoint enabled or no: @samp{y} or @samp{n}
31665 memory location at which the breakpoint is set
31667 logical location of the breakpoint, expressed by function name, file
31669 @item Thread-groups
31670 list of thread groups to which this breakpoint applies
31672 number of times the breakpoint has been hit
31675 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31676 @code{body} field is an empty list.
31678 @subsubheading @value{GDBN} Command
31680 The corresponding @value{GDBN} command is @samp{info break}.
31682 @subsubheading Example
31687 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31688 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31689 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31690 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31691 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31692 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31693 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31694 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31695 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31697 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31698 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31699 line="13",thread-groups=["i1"],times="0"@}]@}
31703 Here's an example of the result when there are no breakpoints:
31708 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31709 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31710 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31711 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31712 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31713 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31714 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31719 @subheading The @code{-break-passcount} Command
31720 @findex -break-passcount
31722 @subsubheading Synopsis
31725 -break-passcount @var{tracepoint-number} @var{passcount}
31728 Set the passcount for tracepoint @var{tracepoint-number} to
31729 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31730 is not a tracepoint, error is emitted. This corresponds to CLI
31731 command @samp{passcount}.
31733 @subheading The @code{-break-watch} Command
31734 @findex -break-watch
31736 @subsubheading Synopsis
31739 -break-watch [ -a | -r ]
31742 Create a watchpoint. With the @samp{-a} option it will create an
31743 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31744 read from or on a write to the memory location. With the @samp{-r}
31745 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31746 trigger only when the memory location is accessed for reading. Without
31747 either of the options, the watchpoint created is a regular watchpoint,
31748 i.e., it will trigger when the memory location is accessed for writing.
31749 @xref{Set Watchpoints, , Setting Watchpoints}.
31751 Note that @samp{-break-list} will report a single list of watchpoints and
31752 breakpoints inserted.
31754 @subsubheading @value{GDBN} Command
31756 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31759 @subsubheading Example
31761 Setting a watchpoint on a variable in the @code{main} function:
31766 ^done,wpt=@{number="2",exp="x"@}
31771 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31772 value=@{old="-268439212",new="55"@},
31773 frame=@{func="main",args=[],file="recursive2.c",
31774 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31778 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31779 the program execution twice: first for the variable changing value, then
31780 for the watchpoint going out of scope.
31785 ^done,wpt=@{number="5",exp="C"@}
31790 *stopped,reason="watchpoint-trigger",
31791 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31792 frame=@{func="callee4",args=[],
31793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31795 arch="i386:x86_64"@}
31800 *stopped,reason="watchpoint-scope",wpnum="5",
31801 frame=@{func="callee3",args=[@{name="strarg",
31802 value="0x11940 \"A string argument.\""@}],
31803 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31804 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31805 arch="i386:x86_64"@}
31809 Listing breakpoints and watchpoints, at different points in the program
31810 execution. Note that once the watchpoint goes out of scope, it is
31816 ^done,wpt=@{number="2",exp="C"@}
31819 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31820 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31821 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31822 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31823 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31824 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31825 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31826 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31827 addr="0x00010734",func="callee4",
31828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31829 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31831 bkpt=@{number="2",type="watchpoint",disp="keep",
31832 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31837 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31838 value=@{old="-276895068",new="3"@},
31839 frame=@{func="callee4",args=[],
31840 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31841 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31842 arch="i386:x86_64"@}
31845 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31846 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31847 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31848 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31849 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31850 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31851 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31852 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31853 addr="0x00010734",func="callee4",
31854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31855 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31857 bkpt=@{number="2",type="watchpoint",disp="keep",
31858 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31862 ^done,reason="watchpoint-scope",wpnum="2",
31863 frame=@{func="callee3",args=[@{name="strarg",
31864 value="0x11940 \"A string argument.\""@}],
31865 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31866 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31867 arch="i386:x86_64"@}
31870 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31871 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31872 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31873 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31874 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31875 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31876 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31877 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31878 addr="0x00010734",func="callee4",
31879 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31880 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31881 thread-groups=["i1"],times="1"@}]@}
31886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31887 @node GDB/MI Catchpoint Commands
31888 @section @sc{gdb/mi} Catchpoint Commands
31890 This section documents @sc{gdb/mi} commands for manipulating
31894 * Shared Library GDB/MI Catchpoint Commands::
31895 * Ada Exception GDB/MI Catchpoint Commands::
31896 * C++ Exception GDB/MI Catchpoint Commands::
31899 @node Shared Library GDB/MI Catchpoint Commands
31900 @subsection Shared Library @sc{gdb/mi} Catchpoints
31902 @subheading The @code{-catch-load} Command
31903 @findex -catch-load
31905 @subsubheading Synopsis
31908 -catch-load [ -t ] [ -d ] @var{regexp}
31911 Add a catchpoint for library load events. If the @samp{-t} option is used,
31912 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31913 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31914 in a disabled state. The @samp{regexp} argument is a regular
31915 expression used to match the name of the loaded library.
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} command is @samp{catch load}.
31922 @subsubheading Example
31925 -catch-load -t foo.so
31926 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31927 what="load of library matching foo.so",catch-type="load",times="0"@}
31932 @subheading The @code{-catch-unload} Command
31933 @findex -catch-unload
31935 @subsubheading Synopsis
31938 -catch-unload [ -t ] [ -d ] @var{regexp}
31941 Add a catchpoint for library unload events. If the @samp{-t} option is
31942 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31943 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31944 created in a disabled state. The @samp{regexp} argument is a regular
31945 expression used to match the name of the unloaded library.
31947 @subsubheading @value{GDBN} Command
31949 The corresponding @value{GDBN} command is @samp{catch unload}.
31951 @subsubheading Example
31954 -catch-unload -d bar.so
31955 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31956 what="load of library matching bar.so",catch-type="unload",times="0"@}
31960 @node Ada Exception GDB/MI Catchpoint Commands
31961 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31963 The following @sc{gdb/mi} commands can be used to create catchpoints
31964 that stop the execution when Ada exceptions are being raised.
31966 @subheading The @code{-catch-assert} Command
31967 @findex -catch-assert
31969 @subsubheading Synopsis
31972 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31975 Add a catchpoint for failed Ada assertions.
31977 The possible optional parameters for this command are:
31980 @item -c @var{condition}
31981 Make the catchpoint conditional on @var{condition}.
31983 Create a disabled catchpoint.
31985 Create a temporary catchpoint.
31988 @subsubheading @value{GDBN} Command
31990 The corresponding @value{GDBN} command is @samp{catch assert}.
31992 @subsubheading Example
31996 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31997 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31998 thread-groups=["i1"],times="0",
31999 original-location="__gnat_debug_raise_assert_failure"@}
32003 @subheading The @code{-catch-exception} Command
32004 @findex -catch-exception
32006 @subsubheading Synopsis
32009 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32013 Add a catchpoint stopping when Ada exceptions are raised.
32014 By default, the command stops the program when any Ada exception
32015 gets raised. But it is also possible, by using some of the
32016 optional parameters described below, to create more selective
32019 The possible optional parameters for this command are:
32022 @item -c @var{condition}
32023 Make the catchpoint conditional on @var{condition}.
32025 Create a disabled catchpoint.
32026 @item -e @var{exception-name}
32027 Only stop when @var{exception-name} is raised. This option cannot
32028 be used combined with @samp{-u}.
32030 Create a temporary catchpoint.
32032 Stop only when an unhandled exception gets raised. This option
32033 cannot be used combined with @samp{-e}.
32036 @subsubheading @value{GDBN} Command
32038 The corresponding @value{GDBN} commands are @samp{catch exception}
32039 and @samp{catch exception unhandled}.
32041 @subsubheading Example
32044 -catch-exception -e Program_Error
32045 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32046 enabled="y",addr="0x0000000000404874",
32047 what="`Program_Error' Ada exception", thread-groups=["i1"],
32048 times="0",original-location="__gnat_debug_raise_exception"@}
32052 @subheading The @code{-catch-handlers} Command
32053 @findex -catch-handlers
32055 @subsubheading Synopsis
32058 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32062 Add a catchpoint stopping when Ada exceptions are handled.
32063 By default, the command stops the program when any Ada exception
32064 gets handled. But it is also possible, by using some of the
32065 optional parameters described below, to create more selective
32068 The possible optional parameters for this command are:
32071 @item -c @var{condition}
32072 Make the catchpoint conditional on @var{condition}.
32074 Create a disabled catchpoint.
32075 @item -e @var{exception-name}
32076 Only stop when @var{exception-name} is handled.
32078 Create a temporary catchpoint.
32081 @subsubheading @value{GDBN} Command
32083 The corresponding @value{GDBN} command is @samp{catch handlers}.
32085 @subsubheading Example
32088 -catch-handlers -e Constraint_Error
32089 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32090 enabled="y",addr="0x0000000000402f68",
32091 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
32092 times="0",original-location="__gnat_begin_handler"@}
32096 @node C++ Exception GDB/MI Catchpoint Commands
32097 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
32099 The following @sc{gdb/mi} commands can be used to create catchpoints
32100 that stop the execution when C@t{++} exceptions are being throw, rethrown,
32103 @subheading The @code{-catch-throw} Command
32104 @findex -catch-throw
32106 @subsubheading Synopsis
32109 -catch-throw [ -t ] [ -r @var{regexp}]
32112 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
32113 given, then only exceptions whose type matches the regular expression
32116 If @samp{-t} is given, then the catchpoint is enabled only for one
32117 stop, the catchpoint is automatically deleted after stopping once for
32120 @subsubheading @value{GDBN} Command
32122 The corresponding @value{GDBN} commands are @samp{catch throw}
32123 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
32125 @subsubheading Example
32128 -catch-throw -r exception_type
32129 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32130 what="exception throw",catch-type="throw",
32131 thread-groups=["i1"],
32132 regexp="exception_type",times="0"@}
32138 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
32139 in __cxa_throw () from /lib64/libstdc++.so.6\n"
32140 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32141 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
32142 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32143 thread-id="1",stopped-threads="all",core="6"
32147 @subheading The @code{-catch-rethrow} Command
32148 @findex -catch-rethrow
32150 @subsubheading Synopsis
32153 -catch-rethrow [ -t ] [ -r @var{regexp}]
32156 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
32157 then only exceptions whose type matches the regular expression will be
32160 If @samp{-t} is given, then the catchpoint is enabled only for one
32161 stop, the catchpoint is automatically deleted after the first event is
32164 @subsubheading @value{GDBN} Command
32166 The corresponding @value{GDBN} commands are @samp{catch rethrow}
32167 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
32169 @subsubheading Example
32172 -catch-rethrow -r exception_type
32173 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32174 what="exception rethrow",catch-type="rethrow",
32175 thread-groups=["i1"],
32176 regexp="exception_type",times="0"@}
32182 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
32183 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
32184 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32185 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
32186 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32187 thread-id="1",stopped-threads="all",core="6"
32191 @subheading The @code{-catch-catch} Command
32192 @findex -catch-catch
32194 @subsubheading Synopsis
32197 -catch-catch [ -t ] [ -r @var{regexp}]
32200 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
32201 is given, then only exceptions whose type matches the regular
32202 expression will be caught.
32204 If @samp{-t} is given, then the catchpoint is enabled only for one
32205 stop, the catchpoint is automatically deleted after the first event is
32208 @subsubheading @value{GDBN} Command
32210 The corresponding @value{GDBN} commands are @samp{catch catch}
32211 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
32213 @subsubheading Example
32216 -catch-catch -r exception_type
32217 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32218 what="exception catch",catch-type="catch",
32219 thread-groups=["i1"],
32220 regexp="exception_type",times="0"@}
32226 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
32227 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
32228 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32229 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
32230 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32231 thread-id="1",stopped-threads="all",core="6"
32235 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32236 @node GDB/MI Program Context
32237 @section @sc{gdb/mi} Program Context
32239 @subheading The @code{-exec-arguments} Command
32240 @findex -exec-arguments
32243 @subsubheading Synopsis
32246 -exec-arguments @var{args}
32249 Set the inferior program arguments, to be used in the next
32252 @subsubheading @value{GDBN} Command
32254 The corresponding @value{GDBN} command is @samp{set args}.
32256 @subsubheading Example
32260 -exec-arguments -v word
32267 @subheading The @code{-exec-show-arguments} Command
32268 @findex -exec-show-arguments
32270 @subsubheading Synopsis
32273 -exec-show-arguments
32276 Print the arguments of the program.
32278 @subsubheading @value{GDBN} Command
32280 The corresponding @value{GDBN} command is @samp{show args}.
32282 @subsubheading Example
32287 @subheading The @code{-environment-cd} Command
32288 @findex -environment-cd
32290 @subsubheading Synopsis
32293 -environment-cd @var{pathdir}
32296 Set @value{GDBN}'s working directory.
32298 @subsubheading @value{GDBN} Command
32300 The corresponding @value{GDBN} command is @samp{cd}.
32302 @subsubheading Example
32306 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32312 @subheading The @code{-environment-directory} Command
32313 @findex -environment-directory
32315 @subsubheading Synopsis
32318 -environment-directory [ -r ] [ @var{pathdir} ]+
32321 Add directories @var{pathdir} to beginning of search path for source files.
32322 If the @samp{-r} option is used, the search path is reset to the default
32323 search path. If directories @var{pathdir} are supplied in addition to the
32324 @samp{-r} option, the search path is first reset and then addition
32326 Multiple directories may be specified, separated by blanks. Specifying
32327 multiple directories in a single command
32328 results in the directories added to the beginning of the
32329 search path in the same order they were presented in the command.
32330 If blanks are needed as
32331 part of a directory name, double-quotes should be used around
32332 the name. In the command output, the path will show up separated
32333 by the system directory-separator character. The directory-separator
32334 character must not be used
32335 in any directory name.
32336 If no directories are specified, the current search path is displayed.
32338 @subsubheading @value{GDBN} Command
32340 The corresponding @value{GDBN} command is @samp{dir}.
32342 @subsubheading Example
32346 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32347 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32349 -environment-directory ""
32350 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32352 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32353 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32355 -environment-directory -r
32356 ^done,source-path="$cdir:$cwd"
32361 @subheading The @code{-environment-path} Command
32362 @findex -environment-path
32364 @subsubheading Synopsis
32367 -environment-path [ -r ] [ @var{pathdir} ]+
32370 Add directories @var{pathdir} to beginning of search path for object files.
32371 If the @samp{-r} option is used, the search path is reset to the original
32372 search path that existed at gdb start-up. If directories @var{pathdir} are
32373 supplied in addition to the
32374 @samp{-r} option, the search path is first reset and then addition
32376 Multiple directories may be specified, separated by blanks. Specifying
32377 multiple directories in a single command
32378 results in the directories added to the beginning of the
32379 search path in the same order they were presented in the command.
32380 If blanks are needed as
32381 part of a directory name, double-quotes should be used around
32382 the name. In the command output, the path will show up separated
32383 by the system directory-separator character. The directory-separator
32384 character must not be used
32385 in any directory name.
32386 If no directories are specified, the current path is displayed.
32389 @subsubheading @value{GDBN} Command
32391 The corresponding @value{GDBN} command is @samp{path}.
32393 @subsubheading Example
32398 ^done,path="/usr/bin"
32400 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32401 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32403 -environment-path -r /usr/local/bin
32404 ^done,path="/usr/local/bin:/usr/bin"
32409 @subheading The @code{-environment-pwd} Command
32410 @findex -environment-pwd
32412 @subsubheading Synopsis
32418 Show the current working directory.
32420 @subsubheading @value{GDBN} Command
32422 The corresponding @value{GDBN} command is @samp{pwd}.
32424 @subsubheading Example
32429 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32434 @node GDB/MI Thread Commands
32435 @section @sc{gdb/mi} Thread Commands
32438 @subheading The @code{-thread-info} Command
32439 @findex -thread-info
32441 @subsubheading Synopsis
32444 -thread-info [ @var{thread-id} ]
32447 Reports information about either a specific thread, if the
32448 @var{thread-id} parameter is present, or about all threads.
32449 @var{thread-id} is the thread's global thread ID. When printing
32450 information about all threads, also reports the global ID of the
32453 @subsubheading @value{GDBN} Command
32455 The @samp{info thread} command prints the same information
32458 @subsubheading Result
32460 The result contains the following attributes:
32464 A list of threads. The format of the elements of the list is described in
32465 @ref{GDB/MI Thread Information}.
32467 @item current-thread-id
32468 The global id of the currently selected thread. This field is omitted if there
32469 is no selected thread (for example, when the selected inferior is not running,
32470 and therefore has no threads) or if a @var{thread-id} argument was passed to
32475 @subsubheading Example
32480 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32481 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32482 args=[]@},state="running"@},
32483 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32484 frame=@{level="0",addr="0x0804891f",func="foo",
32485 args=[@{name="i",value="10"@}],
32486 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32487 state="running"@}],
32488 current-thread-id="1"
32492 @subheading The @code{-thread-list-ids} Command
32493 @findex -thread-list-ids
32495 @subsubheading Synopsis
32501 Produces a list of the currently known global @value{GDBN} thread ids.
32502 At the end of the list it also prints the total number of such
32505 This command is retained for historical reasons, the
32506 @code{-thread-info} command should be used instead.
32508 @subsubheading @value{GDBN} Command
32510 Part of @samp{info threads} supplies the same information.
32512 @subsubheading Example
32517 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32518 current-thread-id="1",number-of-threads="3"
32523 @subheading The @code{-thread-select} Command
32524 @findex -thread-select
32526 @subsubheading Synopsis
32529 -thread-select @var{thread-id}
32532 Make thread with global thread number @var{thread-id} the current
32533 thread. It prints the number of the new current thread, and the
32534 topmost frame for that thread.
32536 This command is deprecated in favor of explicitly using the
32537 @samp{--thread} option to each command.
32539 @subsubheading @value{GDBN} Command
32541 The corresponding @value{GDBN} command is @samp{thread}.
32543 @subsubheading Example
32550 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32551 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32555 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32556 number-of-threads="3"
32559 ^done,new-thread-id="3",
32560 frame=@{level="0",func="vprintf",
32561 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32562 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32567 @node GDB/MI Ada Tasking Commands
32568 @section @sc{gdb/mi} Ada Tasking Commands
32570 @subheading The @code{-ada-task-info} Command
32571 @findex -ada-task-info
32573 @subsubheading Synopsis
32576 -ada-task-info [ @var{task-id} ]
32579 Reports information about either a specific Ada task, if the
32580 @var{task-id} parameter is present, or about all Ada tasks.
32582 @subsubheading @value{GDBN} Command
32584 The @samp{info tasks} command prints the same information
32585 about all Ada tasks (@pxref{Ada Tasks}).
32587 @subsubheading Result
32589 The result is a table of Ada tasks. The following columns are
32590 defined for each Ada task:
32594 This field exists only for the current thread. It has the value @samp{*}.
32597 The identifier that @value{GDBN} uses to refer to the Ada task.
32600 The identifier that the target uses to refer to the Ada task.
32603 The global thread identifier of the thread corresponding to the Ada
32606 This field should always exist, as Ada tasks are always implemented
32607 on top of a thread. But if @value{GDBN} cannot find this corresponding
32608 thread for any reason, the field is omitted.
32611 This field exists only when the task was created by another task.
32612 In this case, it provides the ID of the parent task.
32615 The base priority of the task.
32618 The current state of the task. For a detailed description of the
32619 possible states, see @ref{Ada Tasks}.
32622 The name of the task.
32626 @subsubheading Example
32630 ^done,tasks=@{nr_rows="3",nr_cols="8",
32631 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32632 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32633 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32634 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32635 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32636 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32637 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32638 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32639 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32640 state="Child Termination Wait",name="main_task"@}]@}
32644 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32645 @node GDB/MI Program Execution
32646 @section @sc{gdb/mi} Program Execution
32648 These are the asynchronous commands which generate the out-of-band
32649 record @samp{*stopped}. Currently @value{GDBN} only really executes
32650 asynchronously with remote targets and this interaction is mimicked in
32653 @subheading The @code{-exec-continue} Command
32654 @findex -exec-continue
32656 @subsubheading Synopsis
32659 -exec-continue [--reverse] [--all|--thread-group N]
32662 Resumes the execution of the inferior program, which will continue
32663 to execute until it reaches a debugger stop event. If the
32664 @samp{--reverse} option is specified, execution resumes in reverse until
32665 it reaches a stop event. Stop events may include
32668 breakpoints or watchpoints
32670 signals or exceptions
32672 the end of the process (or its beginning under @samp{--reverse})
32674 the end or beginning of a replay log if one is being used.
32676 In all-stop mode (@pxref{All-Stop
32677 Mode}), may resume only one thread, or all threads, depending on the
32678 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32679 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32680 ignored in all-stop mode. If the @samp{--thread-group} options is
32681 specified, then all threads in that thread group are resumed.
32683 @subsubheading @value{GDBN} Command
32685 The corresponding @value{GDBN} corresponding is @samp{continue}.
32687 @subsubheading Example
32694 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32695 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32696 line="13",arch="i386:x86_64"@}
32701 @subheading The @code{-exec-finish} Command
32702 @findex -exec-finish
32704 @subsubheading Synopsis
32707 -exec-finish [--reverse]
32710 Resumes the execution of the inferior program until the current
32711 function is exited. Displays the results returned by the function.
32712 If the @samp{--reverse} option is specified, resumes the reverse
32713 execution of the inferior program until the point where current
32714 function was called.
32716 @subsubheading @value{GDBN} Command
32718 The corresponding @value{GDBN} command is @samp{finish}.
32720 @subsubheading Example
32722 Function returning @code{void}.
32729 *stopped,reason="function-finished",frame=@{func="main",args=[],
32730 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32734 Function returning other than @code{void}. The name of the internal
32735 @value{GDBN} variable storing the result is printed, together with the
32742 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32743 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32744 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32745 arch="i386:x86_64"@},
32746 gdb-result-var="$1",return-value="0"
32751 @subheading The @code{-exec-interrupt} Command
32752 @findex -exec-interrupt
32754 @subsubheading Synopsis
32757 -exec-interrupt [--all|--thread-group N]
32760 Interrupts the background execution of the target. Note how the token
32761 associated with the stop message is the one for the execution command
32762 that has been interrupted. The token for the interrupt itself only
32763 appears in the @samp{^done} output. If the user is trying to
32764 interrupt a non-running program, an error message will be printed.
32766 Note that when asynchronous execution is enabled, this command is
32767 asynchronous just like other execution commands. That is, first the
32768 @samp{^done} response will be printed, and the target stop will be
32769 reported after that using the @samp{*stopped} notification.
32771 In non-stop mode, only the context thread is interrupted by default.
32772 All threads (in all inferiors) will be interrupted if the
32773 @samp{--all} option is specified. If the @samp{--thread-group}
32774 option is specified, all threads in that group will be interrupted.
32776 @subsubheading @value{GDBN} Command
32778 The corresponding @value{GDBN} command is @samp{interrupt}.
32780 @subsubheading Example
32791 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32792 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32793 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32798 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32802 @subheading The @code{-exec-jump} Command
32805 @subsubheading Synopsis
32808 -exec-jump @var{locspec}
32811 Resumes execution of the inferior program at the address to
32812 which @var{locspec} resolves. @xref{Location Specifications},
32813 for a description of the different forms of @var{locspec}.
32815 @subsubheading @value{GDBN} Command
32817 The corresponding @value{GDBN} command is @samp{jump}.
32819 @subsubheading Example
32822 -exec-jump foo.c:10
32823 *running,thread-id="all"
32828 @subheading The @code{-exec-next} Command
32831 @subsubheading Synopsis
32834 -exec-next [--reverse]
32837 Resumes execution of the inferior program, stopping when the beginning
32838 of the next source line is reached.
32840 If the @samp{--reverse} option is specified, resumes reverse execution
32841 of the inferior program, stopping at the beginning of the previous
32842 source line. If you issue this command on the first line of a
32843 function, it will take you back to the caller of that function, to the
32844 source line where the function was called.
32847 @subsubheading @value{GDBN} Command
32849 The corresponding @value{GDBN} command is @samp{next}.
32851 @subsubheading Example
32857 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32862 @subheading The @code{-exec-next-instruction} Command
32863 @findex -exec-next-instruction
32865 @subsubheading Synopsis
32868 -exec-next-instruction [--reverse]
32871 Executes one machine instruction. If the instruction is a function
32872 call, continues until the function returns. If the program stops at an
32873 instruction in the middle of a source line, the address will be
32876 If the @samp{--reverse} option is specified, resumes reverse execution
32877 of the inferior program, stopping at the previous instruction. If the
32878 previously executed instruction was a return from another function,
32879 it will continue to execute in reverse until the call to that function
32880 (from the current stack frame) is reached.
32882 @subsubheading @value{GDBN} Command
32884 The corresponding @value{GDBN} command is @samp{nexti}.
32886 @subsubheading Example
32890 -exec-next-instruction
32894 *stopped,reason="end-stepping-range",
32895 addr="0x000100d4",line="5",file="hello.c"
32900 @subheading The @code{-exec-return} Command
32901 @findex -exec-return
32903 @subsubheading Synopsis
32909 Makes current function return immediately. Doesn't execute the inferior.
32910 Displays the new current frame.
32912 @subsubheading @value{GDBN} Command
32914 The corresponding @value{GDBN} command is @samp{return}.
32916 @subsubheading Example
32920 200-break-insert callee4
32921 200^done,bkpt=@{number="1",addr="0x00010734",
32922 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32927 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32928 frame=@{func="callee4",args=[],
32929 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32930 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32931 arch="i386:x86_64"@}
32937 111^done,frame=@{level="0",func="callee3",
32938 args=[@{name="strarg",
32939 value="0x11940 \"A string argument.\""@}],
32940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32941 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32942 arch="i386:x86_64"@}
32947 @subheading The @code{-exec-run} Command
32950 @subsubheading Synopsis
32953 -exec-run [ --all | --thread-group N ] [ --start ]
32956 Starts execution of the inferior from the beginning. The inferior
32957 executes until either a breakpoint is encountered or the program
32958 exits. In the latter case the output will include an exit code, if
32959 the program has exited exceptionally.
32961 When neither the @samp{--all} nor the @samp{--thread-group} option
32962 is specified, the current inferior is started. If the
32963 @samp{--thread-group} option is specified, it should refer to a thread
32964 group of type @samp{process}, and that thread group will be started.
32965 If the @samp{--all} option is specified, then all inferiors will be started.
32967 Using the @samp{--start} option instructs the debugger to stop
32968 the execution at the start of the inferior's main subprogram,
32969 following the same behavior as the @code{start} command
32970 (@pxref{Starting}).
32972 @subsubheading @value{GDBN} Command
32974 The corresponding @value{GDBN} command is @samp{run}.
32976 @subsubheading Examples
32981 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32986 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32987 frame=@{func="main",args=[],file="recursive2.c",
32988 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32993 Program exited normally:
33001 *stopped,reason="exited-normally"
33006 Program exited exceptionally:
33014 *stopped,reason="exited",exit-code="01"
33018 Another way the program can terminate is if it receives a signal such as
33019 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
33023 *stopped,reason="exited-signalled",signal-name="SIGINT",
33024 signal-meaning="Interrupt"
33028 @c @subheading -exec-signal
33031 @subheading The @code{-exec-step} Command
33034 @subsubheading Synopsis
33037 -exec-step [--reverse]
33040 Resumes execution of the inferior program, stopping when the beginning
33041 of the next source line is reached, if the next source line is not a
33042 function call. If it is, stop at the first instruction of the called
33043 function. If the @samp{--reverse} option is specified, resumes reverse
33044 execution of the inferior program, stopping at the beginning of the
33045 previously executed source line.
33047 @subsubheading @value{GDBN} Command
33049 The corresponding @value{GDBN} command is @samp{step}.
33051 @subsubheading Example
33053 Stepping into a function:
33059 *stopped,reason="end-stepping-range",
33060 frame=@{func="foo",args=[@{name="a",value="10"@},
33061 @{name="b",value="0"@}],file="recursive2.c",
33062 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
33072 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
33077 @subheading The @code{-exec-step-instruction} Command
33078 @findex -exec-step-instruction
33080 @subsubheading Synopsis
33083 -exec-step-instruction [--reverse]
33086 Resumes the inferior which executes one machine instruction. If the
33087 @samp{--reverse} option is specified, resumes reverse execution of the
33088 inferior program, stopping at the previously executed instruction.
33089 The output, once @value{GDBN} has stopped, will vary depending on
33090 whether we have stopped in the middle of a source line or not. In the
33091 former case, the address at which the program stopped will be printed
33094 @subsubheading @value{GDBN} Command
33096 The corresponding @value{GDBN} command is @samp{stepi}.
33098 @subsubheading Example
33102 -exec-step-instruction
33106 *stopped,reason="end-stepping-range",
33107 frame=@{func="foo",args=[],file="try.c",
33108 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33110 -exec-step-instruction
33114 *stopped,reason="end-stepping-range",
33115 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
33116 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33121 @subheading The @code{-exec-until} Command
33122 @findex -exec-until
33124 @subsubheading Synopsis
33127 -exec-until [ @var{locspec} ]
33130 Executes the inferior until it reaches the address to which
33131 @var{locspec} resolves. If there is no argument, the inferior
33132 executes until it reaches a source line greater than the current one.
33133 The reason for stopping in this case will be @samp{location-reached}.
33135 @subsubheading @value{GDBN} Command
33137 The corresponding @value{GDBN} command is @samp{until}.
33139 @subsubheading Example
33143 -exec-until recursive2.c:6
33147 *stopped,reason="location-reached",frame=@{func="main",args=[],
33148 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
33149 arch="i386:x86_64"@}
33154 @subheading -file-clear
33155 Is this going away????
33158 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33159 @node GDB/MI Stack Manipulation
33160 @section @sc{gdb/mi} Stack Manipulation Commands
33162 @subheading The @code{-enable-frame-filters} Command
33163 @findex -enable-frame-filters
33166 -enable-frame-filters
33169 @value{GDBN} allows Python-based frame filters to affect the output of
33170 the MI commands relating to stack traces. As there is no way to
33171 implement this in a fully backward-compatible way, a front end must
33172 request that this functionality be enabled.
33174 Once enabled, this feature cannot be disabled.
33176 Note that if Python support has not been compiled into @value{GDBN},
33177 this command will still succeed (and do nothing).
33179 @subheading The @code{-stack-info-frame} Command
33180 @findex -stack-info-frame
33182 @subsubheading Synopsis
33188 Get info on the selected frame.
33190 @subsubheading @value{GDBN} Command
33192 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
33193 (without arguments).
33195 @subsubheading Example
33200 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
33201 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33202 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33203 arch="i386:x86_64"@}
33207 @subheading The @code{-stack-info-depth} Command
33208 @findex -stack-info-depth
33210 @subsubheading Synopsis
33213 -stack-info-depth [ @var{max-depth} ]
33216 Return the depth of the stack. If the integer argument @var{max-depth}
33217 is specified, do not count beyond @var{max-depth} frames.
33219 @subsubheading @value{GDBN} Command
33221 There's no equivalent @value{GDBN} command.
33223 @subsubheading Example
33225 For a stack with frame levels 0 through 11:
33232 -stack-info-depth 4
33235 -stack-info-depth 12
33238 -stack-info-depth 11
33241 -stack-info-depth 13
33246 @anchor{-stack-list-arguments}
33247 @subheading The @code{-stack-list-arguments} Command
33248 @findex -stack-list-arguments
33250 @subsubheading Synopsis
33253 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33254 [ @var{low-frame} @var{high-frame} ]
33257 Display a list of the arguments for the frames between @var{low-frame}
33258 and @var{high-frame} (inclusive). If @var{low-frame} and
33259 @var{high-frame} are not provided, list the arguments for the whole
33260 call stack. If the two arguments are equal, show the single frame
33261 at the corresponding level. It is an error if @var{low-frame} is
33262 larger than the actual number of frames. On the other hand,
33263 @var{high-frame} may be larger than the actual number of frames, in
33264 which case only existing frames will be returned.
33266 If @var{print-values} is 0 or @code{--no-values}, print only the names of
33267 the variables; if it is 1 or @code{--all-values}, print also their
33268 values; and if it is 2 or @code{--simple-values}, print the name,
33269 type and value for simple data types, and the name and type for arrays,
33270 structures and unions. If the option @code{--no-frame-filters} is
33271 supplied, then Python frame filters will not be executed.
33273 If the @code{--skip-unavailable} option is specified, arguments that
33274 are not available are not listed. Partially available arguments
33275 are still displayed, however.
33277 Use of this command to obtain arguments in a single frame is
33278 deprecated in favor of the @samp{-stack-list-variables} command.
33280 @subsubheading @value{GDBN} Command
33282 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
33283 @samp{gdb_get_args} command which partially overlaps with the
33284 functionality of @samp{-stack-list-arguments}.
33286 @subsubheading Example
33293 frame=@{level="0",addr="0x00010734",func="callee4",
33294 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33295 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33296 arch="i386:x86_64"@},
33297 frame=@{level="1",addr="0x0001076c",func="callee3",
33298 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33299 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33300 arch="i386:x86_64"@},
33301 frame=@{level="2",addr="0x0001078c",func="callee2",
33302 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33303 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33304 arch="i386:x86_64"@},
33305 frame=@{level="3",addr="0x000107b4",func="callee1",
33306 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33307 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33308 arch="i386:x86_64"@},
33309 frame=@{level="4",addr="0x000107e0",func="main",
33310 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33311 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33312 arch="i386:x86_64"@}]
33314 -stack-list-arguments 0
33317 frame=@{level="0",args=[]@},
33318 frame=@{level="1",args=[name="strarg"]@},
33319 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33320 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33321 frame=@{level="4",args=[]@}]
33323 -stack-list-arguments 1
33326 frame=@{level="0",args=[]@},
33328 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33329 frame=@{level="2",args=[
33330 @{name="intarg",value="2"@},
33331 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33332 @{frame=@{level="3",args=[
33333 @{name="intarg",value="2"@},
33334 @{name="strarg",value="0x11940 \"A string argument.\""@},
33335 @{name="fltarg",value="3.5"@}]@},
33336 frame=@{level="4",args=[]@}]
33338 -stack-list-arguments 0 2 2
33339 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33341 -stack-list-arguments 1 2 2
33342 ^done,stack-args=[frame=@{level="2",
33343 args=[@{name="intarg",value="2"@},
33344 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33348 @c @subheading -stack-list-exception-handlers
33351 @anchor{-stack-list-frames}
33352 @subheading The @code{-stack-list-frames} Command
33353 @findex -stack-list-frames
33355 @subsubheading Synopsis
33358 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33361 List the frames currently on the stack. For each frame it displays the
33366 The frame number, 0 being the topmost frame, i.e., the innermost function.
33368 The @code{$pc} value for that frame.
33372 File name of the source file where the function lives.
33373 @item @var{fullname}
33374 The full file name of the source file where the function lives.
33376 Line number corresponding to the @code{$pc}.
33378 The shared library where this function is defined. This is only given
33379 if the frame's function is not known.
33381 Frame's architecture.
33384 If invoked without arguments, this command prints a backtrace for the
33385 whole stack. If given two integer arguments, it shows the frames whose
33386 levels are between the two arguments (inclusive). If the two arguments
33387 are equal, it shows the single frame at the corresponding level. It is
33388 an error if @var{low-frame} is larger than the actual number of
33389 frames. On the other hand, @var{high-frame} may be larger than the
33390 actual number of frames, in which case only existing frames will be
33391 returned. If the option @code{--no-frame-filters} is supplied, then
33392 Python frame filters will not be executed.
33394 @subsubheading @value{GDBN} Command
33396 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33398 @subsubheading Example
33400 Full stack backtrace:
33406 [frame=@{level="0",addr="0x0001076c",func="foo",
33407 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33408 arch="i386:x86_64"@},
33409 frame=@{level="1",addr="0x000107a4",func="foo",
33410 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33411 arch="i386:x86_64"@},
33412 frame=@{level="2",addr="0x000107a4",func="foo",
33413 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33414 arch="i386:x86_64"@},
33415 frame=@{level="3",addr="0x000107a4",func="foo",
33416 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33417 arch="i386:x86_64"@},
33418 frame=@{level="4",addr="0x000107a4",func="foo",
33419 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33420 arch="i386:x86_64"@},
33421 frame=@{level="5",addr="0x000107a4",func="foo",
33422 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33423 arch="i386:x86_64"@},
33424 frame=@{level="6",addr="0x000107a4",func="foo",
33425 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33426 arch="i386:x86_64"@},
33427 frame=@{level="7",addr="0x000107a4",func="foo",
33428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33429 arch="i386:x86_64"@},
33430 frame=@{level="8",addr="0x000107a4",func="foo",
33431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33432 arch="i386:x86_64"@},
33433 frame=@{level="9",addr="0x000107a4",func="foo",
33434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33435 arch="i386:x86_64"@},
33436 frame=@{level="10",addr="0x000107a4",func="foo",
33437 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33438 arch="i386:x86_64"@},
33439 frame=@{level="11",addr="0x00010738",func="main",
33440 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33441 arch="i386:x86_64"@}]
33445 Show frames between @var{low_frame} and @var{high_frame}:
33449 -stack-list-frames 3 5
33451 [frame=@{level="3",addr="0x000107a4",func="foo",
33452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33453 arch="i386:x86_64"@},
33454 frame=@{level="4",addr="0x000107a4",func="foo",
33455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33456 arch="i386:x86_64"@},
33457 frame=@{level="5",addr="0x000107a4",func="foo",
33458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33459 arch="i386:x86_64"@}]
33463 Show a single frame:
33467 -stack-list-frames 3 3
33469 [frame=@{level="3",addr="0x000107a4",func="foo",
33470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33471 arch="i386:x86_64"@}]
33476 @subheading The @code{-stack-list-locals} Command
33477 @findex -stack-list-locals
33478 @anchor{-stack-list-locals}
33480 @subsubheading Synopsis
33483 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33486 Display the local variable names for the selected frame. If
33487 @var{print-values} is 0 or @code{--no-values}, print only the names of
33488 the variables; if it is 1 or @code{--all-values}, print also their
33489 values; and if it is 2 or @code{--simple-values}, print the name,
33490 type and value for simple data types, and the name and type for arrays,
33491 structures and unions. In this last case, a frontend can immediately
33492 display the value of simple data types and create variable objects for
33493 other data types when the user wishes to explore their values in
33494 more detail. If the option @code{--no-frame-filters} is supplied, then
33495 Python frame filters will not be executed.
33497 If the @code{--skip-unavailable} option is specified, local variables
33498 that are not available are not listed. Partially available local
33499 variables are still displayed, however.
33501 This command is deprecated in favor of the
33502 @samp{-stack-list-variables} command.
33504 @subsubheading @value{GDBN} Command
33506 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33508 @subsubheading Example
33512 -stack-list-locals 0
33513 ^done,locals=[name="A",name="B",name="C"]
33515 -stack-list-locals --all-values
33516 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33517 @{name="C",value="@{1, 2, 3@}"@}]
33518 -stack-list-locals --simple-values
33519 ^done,locals=[@{name="A",type="int",value="1"@},
33520 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33524 @anchor{-stack-list-variables}
33525 @subheading The @code{-stack-list-variables} Command
33526 @findex -stack-list-variables
33528 @subsubheading Synopsis
33531 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33534 Display the names of local variables and function arguments for the selected frame. If
33535 @var{print-values} is 0 or @code{--no-values}, print only the names of
33536 the variables; if it is 1 or @code{--all-values}, print also their
33537 values; and if it is 2 or @code{--simple-values}, print the name,
33538 type and value for simple data types, and the name and type for arrays,
33539 structures and unions. If the option @code{--no-frame-filters} is
33540 supplied, then Python frame filters will not be executed.
33542 If the @code{--skip-unavailable} option is specified, local variables
33543 and arguments that are not available are not listed. Partially
33544 available arguments and local variables are still displayed, however.
33546 @subsubheading Example
33550 -stack-list-variables --thread 1 --frame 0 --all-values
33551 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33556 @subheading The @code{-stack-select-frame} Command
33557 @findex -stack-select-frame
33559 @subsubheading Synopsis
33562 -stack-select-frame @var{framenum}
33565 Change the selected frame. Select a different frame @var{framenum} on
33568 This command in deprecated in favor of passing the @samp{--frame}
33569 option to every command.
33571 @subsubheading @value{GDBN} Command
33573 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33574 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33576 @subsubheading Example
33580 -stack-select-frame 2
33585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33586 @node GDB/MI Variable Objects
33587 @section @sc{gdb/mi} Variable Objects
33591 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33593 For the implementation of a variable debugger window (locals, watched
33594 expressions, etc.), we are proposing the adaptation of the existing code
33595 used by @code{Insight}.
33597 The two main reasons for that are:
33601 It has been proven in practice (it is already on its second generation).
33604 It will shorten development time (needless to say how important it is
33608 The original interface was designed to be used by Tcl code, so it was
33609 slightly changed so it could be used through @sc{gdb/mi}. This section
33610 describes the @sc{gdb/mi} operations that will be available and gives some
33611 hints about their use.
33613 @emph{Note}: In addition to the set of operations described here, we
33614 expect the @sc{gui} implementation of a variable window to require, at
33615 least, the following operations:
33618 @item @code{-gdb-show} @code{output-radix}
33619 @item @code{-stack-list-arguments}
33620 @item @code{-stack-list-locals}
33621 @item @code{-stack-select-frame}
33626 @subheading Introduction to Variable Objects
33628 @cindex variable objects in @sc{gdb/mi}
33630 Variable objects are "object-oriented" MI interface for examining and
33631 changing values of expressions. Unlike some other MI interfaces that
33632 work with expressions, variable objects are specifically designed for
33633 simple and efficient presentation in the frontend. A variable object
33634 is identified by string name. When a variable object is created, the
33635 frontend specifies the expression for that variable object. The
33636 expression can be a simple variable, or it can be an arbitrary complex
33637 expression, and can even involve CPU registers. After creating a
33638 variable object, the frontend can invoke other variable object
33639 operations---for example to obtain or change the value of a variable
33640 object, or to change display format.
33642 Variable objects have hierarchical tree structure. Any variable object
33643 that corresponds to a composite type, such as structure in C, has
33644 a number of child variable objects, for example corresponding to each
33645 element of a structure. A child variable object can itself have
33646 children, recursively. Recursion ends when we reach
33647 leaf variable objects, which always have built-in types. Child variable
33648 objects are created only by explicit request, so if a frontend
33649 is not interested in the children of a particular variable object, no
33650 child will be created.
33652 For a leaf variable object it is possible to obtain its value as a
33653 string, or set the value from a string. String value can be also
33654 obtained for a non-leaf variable object, but it's generally a string
33655 that only indicates the type of the object, and does not list its
33656 contents. Assignment to a non-leaf variable object is not allowed.
33658 A frontend does not need to read the values of all variable objects each time
33659 the program stops. Instead, MI provides an update command that lists all
33660 variable objects whose values has changed since the last update
33661 operation. This considerably reduces the amount of data that must
33662 be transferred to the frontend. As noted above, children variable
33663 objects are created on demand, and only leaf variable objects have a
33664 real value. As result, gdb will read target memory only for leaf
33665 variables that frontend has created.
33667 The automatic update is not always desirable. For example, a frontend
33668 might want to keep a value of some expression for future reference,
33669 and never update it. For another example, fetching memory is
33670 relatively slow for embedded targets, so a frontend might want
33671 to disable automatic update for the variables that are either not
33672 visible on the screen, or ``closed''. This is possible using so
33673 called ``frozen variable objects''. Such variable objects are never
33674 implicitly updated.
33676 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33677 fixed variable object, the expression is parsed when the variable
33678 object is created, including associating identifiers to specific
33679 variables. The meaning of expression never changes. For a floating
33680 variable object the values of variables whose names appear in the
33681 expressions are re-evaluated every time in the context of the current
33682 frame. Consider this example:
33687 struct work_state state;
33694 If a fixed variable object for the @code{state} variable is created in
33695 this function, and we enter the recursive call, the variable
33696 object will report the value of @code{state} in the top-level
33697 @code{do_work} invocation. On the other hand, a floating variable
33698 object will report the value of @code{state} in the current frame.
33700 If an expression specified when creating a fixed variable object
33701 refers to a local variable, the variable object becomes bound to the
33702 thread and frame in which the variable object is created. When such
33703 variable object is updated, @value{GDBN} makes sure that the
33704 thread/frame combination the variable object is bound to still exists,
33705 and re-evaluates the variable object in context of that thread/frame.
33707 The following is the complete set of @sc{gdb/mi} operations defined to
33708 access this functionality:
33710 @multitable @columnfractions .4 .6
33711 @item @strong{Operation}
33712 @tab @strong{Description}
33714 @item @code{-enable-pretty-printing}
33715 @tab enable Python-based pretty-printing
33716 @item @code{-var-create}
33717 @tab create a variable object
33718 @item @code{-var-delete}
33719 @tab delete the variable object and/or its children
33720 @item @code{-var-set-format}
33721 @tab set the display format of this variable
33722 @item @code{-var-show-format}
33723 @tab show the display format of this variable
33724 @item @code{-var-info-num-children}
33725 @tab tells how many children this object has
33726 @item @code{-var-list-children}
33727 @tab return a list of the object's children
33728 @item @code{-var-info-type}
33729 @tab show the type of this variable object
33730 @item @code{-var-info-expression}
33731 @tab print parent-relative expression that this variable object represents
33732 @item @code{-var-info-path-expression}
33733 @tab print full expression that this variable object represents
33734 @item @code{-var-show-attributes}
33735 @tab is this variable editable? does it exist here?
33736 @item @code{-var-evaluate-expression}
33737 @tab get the value of this variable
33738 @item @code{-var-assign}
33739 @tab set the value of this variable
33740 @item @code{-var-update}
33741 @tab update the variable and its children
33742 @item @code{-var-set-frozen}
33743 @tab set frozenness attribute
33744 @item @code{-var-set-update-range}
33745 @tab set range of children to display on update
33748 In the next subsection we describe each operation in detail and suggest
33749 how it can be used.
33751 @subheading Description And Use of Operations on Variable Objects
33753 @subheading The @code{-enable-pretty-printing} Command
33754 @findex -enable-pretty-printing
33757 -enable-pretty-printing
33760 @value{GDBN} allows Python-based visualizers to affect the output of the
33761 MI variable object commands. However, because there was no way to
33762 implement this in a fully backward-compatible way, a front end must
33763 request that this functionality be enabled.
33765 Once enabled, this feature cannot be disabled.
33767 Note that if Python support has not been compiled into @value{GDBN},
33768 this command will still succeed (and do nothing).
33770 @subheading The @code{-var-create} Command
33771 @findex -var-create
33773 @subsubheading Synopsis
33776 -var-create @{@var{name} | "-"@}
33777 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33780 This operation creates a variable object, which allows the monitoring of
33781 a variable, the result of an expression, a memory cell or a CPU
33784 The @var{name} parameter is the string by which the object can be
33785 referenced. It must be unique. If @samp{-} is specified, the varobj
33786 system will generate a string ``varNNNNNN'' automatically. It will be
33787 unique provided that one does not specify @var{name} of that format.
33788 The command fails if a duplicate name is found.
33790 The frame under which the expression should be evaluated can be
33791 specified by @var{frame-addr}. A @samp{*} indicates that the current
33792 frame should be used. A @samp{@@} indicates that a floating variable
33793 object must be created.
33795 @var{expression} is any expression valid on the current language set (must not
33796 begin with a @samp{*}), or one of the following:
33800 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33803 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33806 @samp{$@var{regname}} --- a CPU register name
33809 @cindex dynamic varobj
33810 A varobj's contents may be provided by a Python-based pretty-printer. In this
33811 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33812 have slightly different semantics in some cases. If the
33813 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33814 will never create a dynamic varobj. This ensures backward
33815 compatibility for existing clients.
33817 @subsubheading Result
33819 This operation returns attributes of the newly-created varobj. These
33824 The name of the varobj.
33827 The number of children of the varobj. This number is not necessarily
33828 reliable for a dynamic varobj. Instead, you must examine the
33829 @samp{has_more} attribute.
33832 The varobj's scalar value. For a varobj whose type is some sort of
33833 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33834 will not be interesting.
33837 The varobj's type. This is a string representation of the type, as
33838 would be printed by the @value{GDBN} CLI. If @samp{print object}
33839 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33840 @emph{actual} (derived) type of the object is shown rather than the
33841 @emph{declared} one.
33844 If a variable object is bound to a specific thread, then this is the
33845 thread's global identifier.
33848 For a dynamic varobj, this indicates whether there appear to be any
33849 children available. For a non-dynamic varobj, this will be 0.
33852 This attribute will be present and have the value @samp{1} if the
33853 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33854 then this attribute will not be present.
33857 A dynamic varobj can supply a display hint to the front end. The
33858 value comes directly from the Python pretty-printer object's
33859 @code{display_hint} method. @xref{Pretty Printing API}.
33862 Typical output will look like this:
33865 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33866 has_more="@var{has_more}"
33870 @subheading The @code{-var-delete} Command
33871 @findex -var-delete
33873 @subsubheading Synopsis
33876 -var-delete [ -c ] @var{name}
33879 Deletes a previously created variable object and all of its children.
33880 With the @samp{-c} option, just deletes the children.
33882 Returns an error if the object @var{name} is not found.
33885 @subheading The @code{-var-set-format} Command
33886 @findex -var-set-format
33888 @subsubheading Synopsis
33891 -var-set-format @var{name} @var{format-spec}
33894 Sets the output format for the value of the object @var{name} to be
33897 @anchor{-var-set-format}
33898 The syntax for the @var{format-spec} is as follows:
33901 @var{format-spec} @expansion{}
33902 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33905 The natural format is the default format choosen automatically
33906 based on the variable type (like decimal for an @code{int}, hex
33907 for pointers, etc.).
33909 The zero-hexadecimal format has a representation similar to hexadecimal
33910 but with padding zeroes to the left of the value. For example, a 32-bit
33911 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33912 zero-hexadecimal format.
33914 For a variable with children, the format is set only on the
33915 variable itself, and the children are not affected.
33917 @subheading The @code{-var-show-format} Command
33918 @findex -var-show-format
33920 @subsubheading Synopsis
33923 -var-show-format @var{name}
33926 Returns the format used to display the value of the object @var{name}.
33929 @var{format} @expansion{}
33934 @subheading The @code{-var-info-num-children} Command
33935 @findex -var-info-num-children
33937 @subsubheading Synopsis
33940 -var-info-num-children @var{name}
33943 Returns the number of children of a variable object @var{name}:
33949 Note that this number is not completely reliable for a dynamic varobj.
33950 It will return the current number of children, but more children may
33954 @subheading The @code{-var-list-children} Command
33955 @findex -var-list-children
33957 @subsubheading Synopsis
33960 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33962 @anchor{-var-list-children}
33964 Return a list of the children of the specified variable object and
33965 create variable objects for them, if they do not already exist. With
33966 a single argument or if @var{print-values} has a value of 0 or
33967 @code{--no-values}, print only the names of the variables; if
33968 @var{print-values} is 1 or @code{--all-values}, also print their
33969 values; and if it is 2 or @code{--simple-values} print the name and
33970 value for simple data types and just the name for arrays, structures
33973 @var{from} and @var{to}, if specified, indicate the range of children
33974 to report. If @var{from} or @var{to} is less than zero, the range is
33975 reset and all children will be reported. Otherwise, children starting
33976 at @var{from} (zero-based) and up to and excluding @var{to} will be
33979 If a child range is requested, it will only affect the current call to
33980 @code{-var-list-children}, but not future calls to @code{-var-update}.
33981 For this, you must instead use @code{-var-set-update-range}. The
33982 intent of this approach is to enable a front end to implement any
33983 update approach it likes; for example, scrolling a view may cause the
33984 front end to request more children with @code{-var-list-children}, and
33985 then the front end could call @code{-var-set-update-range} with a
33986 different range to ensure that future updates are restricted to just
33989 For each child the following results are returned:
33994 Name of the variable object created for this child.
33997 The expression to be shown to the user by the front end to designate this child.
33998 For example this may be the name of a structure member.
34000 For a dynamic varobj, this value cannot be used to form an
34001 expression. There is no way to do this at all with a dynamic varobj.
34003 For C/C@t{++} structures there are several pseudo children returned to
34004 designate access qualifiers. For these pseudo children @var{exp} is
34005 @samp{public}, @samp{private}, or @samp{protected}. In this case the
34006 type and value are not present.
34008 A dynamic varobj will not report the access qualifying
34009 pseudo-children, regardless of the language. This information is not
34010 available at all with a dynamic varobj.
34013 Number of children this child has. For a dynamic varobj, this will be
34017 The type of the child. If @samp{print object}
34018 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34019 @emph{actual} (derived) type of the object is shown rather than the
34020 @emph{declared} one.
34023 If values were requested, this is the value.
34026 If this variable object is associated with a thread, this is the
34027 thread's global thread id. Otherwise this result is not present.
34030 If the variable object is frozen, this variable will be present with a value of 1.
34033 A dynamic varobj can supply a display hint to the front end. The
34034 value comes directly from the Python pretty-printer object's
34035 @code{display_hint} method. @xref{Pretty Printing API}.
34038 This attribute will be present and have the value @samp{1} if the
34039 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34040 then this attribute will not be present.
34044 The result may have its own attributes:
34048 A dynamic varobj can supply a display hint to the front end. The
34049 value comes directly from the Python pretty-printer object's
34050 @code{display_hint} method. @xref{Pretty Printing API}.
34053 This is an integer attribute which is nonzero if there are children
34054 remaining after the end of the selected range.
34057 @subsubheading Example
34061 -var-list-children n
34062 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34063 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
34065 -var-list-children --all-values n
34066 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34067 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
34071 @subheading The @code{-var-info-type} Command
34072 @findex -var-info-type
34074 @subsubheading Synopsis
34077 -var-info-type @var{name}
34080 Returns the type of the specified variable @var{name}. The type is
34081 returned as a string in the same format as it is output by the
34085 type=@var{typename}
34089 @subheading The @code{-var-info-expression} Command
34090 @findex -var-info-expression
34092 @subsubheading Synopsis
34095 -var-info-expression @var{name}
34098 Returns a string that is suitable for presenting this
34099 variable object in user interface. The string is generally
34100 not valid expression in the current language, and cannot be evaluated.
34102 For example, if @code{a} is an array, and variable object
34103 @code{A} was created for @code{a}, then we'll get this output:
34106 (gdb) -var-info-expression A.1
34107 ^done,lang="C",exp="1"
34111 Here, the value of @code{lang} is the language name, which can be
34112 found in @ref{Supported Languages}.
34114 Note that the output of the @code{-var-list-children} command also
34115 includes those expressions, so the @code{-var-info-expression} command
34118 @subheading The @code{-var-info-path-expression} Command
34119 @findex -var-info-path-expression
34121 @subsubheading Synopsis
34124 -var-info-path-expression @var{name}
34127 Returns an expression that can be evaluated in the current
34128 context and will yield the same value that a variable object has.
34129 Compare this with the @code{-var-info-expression} command, which
34130 result can be used only for UI presentation. Typical use of
34131 the @code{-var-info-path-expression} command is creating a
34132 watchpoint from a variable object.
34134 This command is currently not valid for children of a dynamic varobj,
34135 and will give an error when invoked on one.
34137 For example, suppose @code{C} is a C@t{++} class, derived from class
34138 @code{Base}, and that the @code{Base} class has a member called
34139 @code{m_size}. Assume a variable @code{c} is has the type of
34140 @code{C} and a variable object @code{C} was created for variable
34141 @code{c}. Then, we'll get this output:
34143 (gdb) -var-info-path-expression C.Base.public.m_size
34144 ^done,path_expr=((Base)c).m_size)
34147 @subheading The @code{-var-show-attributes} Command
34148 @findex -var-show-attributes
34150 @subsubheading Synopsis
34153 -var-show-attributes @var{name}
34156 List attributes of the specified variable object @var{name}:
34159 status=@var{attr} [ ( ,@var{attr} )* ]
34163 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
34165 @subheading The @code{-var-evaluate-expression} Command
34166 @findex -var-evaluate-expression
34168 @subsubheading Synopsis
34171 -var-evaluate-expression [-f @var{format-spec}] @var{name}
34174 Evaluates the expression that is represented by the specified variable
34175 object and returns its value as a string. The format of the string
34176 can be specified with the @samp{-f} option. The possible values of
34177 this option are the same as for @code{-var-set-format}
34178 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
34179 the current display format will be used. The current display format
34180 can be changed using the @code{-var-set-format} command.
34186 Note that one must invoke @code{-var-list-children} for a variable
34187 before the value of a child variable can be evaluated.
34189 @subheading The @code{-var-assign} Command
34190 @findex -var-assign
34192 @subsubheading Synopsis
34195 -var-assign @var{name} @var{expression}
34198 Assigns the value of @var{expression} to the variable object specified
34199 by @var{name}. The object must be @samp{editable}. If the variable's
34200 value is altered by the assign, the variable will show up in any
34201 subsequent @code{-var-update} list.
34203 @subsubheading Example
34211 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
34215 @subheading The @code{-var-update} Command
34216 @findex -var-update
34218 @subsubheading Synopsis
34221 -var-update [@var{print-values}] @{@var{name} | "*"@}
34224 Reevaluate the expressions corresponding to the variable object
34225 @var{name} and all its direct and indirect children, and return the
34226 list of variable objects whose values have changed; @var{name} must
34227 be a root variable object. Here, ``changed'' means that the result of
34228 @code{-var-evaluate-expression} before and after the
34229 @code{-var-update} is different. If @samp{*} is used as the variable
34230 object names, all existing variable objects are updated, except
34231 for frozen ones (@pxref{-var-set-frozen}). The option
34232 @var{print-values} determines whether both names and values, or just
34233 names are printed. The possible values of this option are the same
34234 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
34235 recommended to use the @samp{--all-values} option, to reduce the
34236 number of MI commands needed on each program stop.
34238 With the @samp{*} parameter, if a variable object is bound to a
34239 currently running thread, it will not be updated, without any
34242 If @code{-var-set-update-range} was previously used on a varobj, then
34243 only the selected range of children will be reported.
34245 @code{-var-update} reports all the changed varobjs in a tuple named
34248 Each item in the change list is itself a tuple holding:
34252 The name of the varobj.
34255 If values were requested for this update, then this field will be
34256 present and will hold the value of the varobj.
34259 @anchor{-var-update}
34260 This field is a string which may take one of three values:
34264 The variable object's current value is valid.
34267 The variable object does not currently hold a valid value but it may
34268 hold one in the future if its associated expression comes back into
34272 The variable object no longer holds a valid value.
34273 This can occur when the executable file being debugged has changed,
34274 either through recompilation or by using the @value{GDBN} @code{file}
34275 command. The front end should normally choose to delete these variable
34279 In the future new values may be added to this list so the front should
34280 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
34283 This is only present if the varobj is still valid. If the type
34284 changed, then this will be the string @samp{true}; otherwise it will
34287 When a varobj's type changes, its children are also likely to have
34288 become incorrect. Therefore, the varobj's children are automatically
34289 deleted when this attribute is @samp{true}. Also, the varobj's update
34290 range, when set using the @code{-var-set-update-range} command, is
34294 If the varobj's type changed, then this field will be present and will
34297 @item new_num_children
34298 For a dynamic varobj, if the number of children changed, or if the
34299 type changed, this will be the new number of children.
34301 The @samp{numchild} field in other varobj responses is generally not
34302 valid for a dynamic varobj -- it will show the number of children that
34303 @value{GDBN} knows about, but because dynamic varobjs lazily
34304 instantiate their children, this will not reflect the number of
34305 children which may be available.
34307 The @samp{new_num_children} attribute only reports changes to the
34308 number of children known by @value{GDBN}. This is the only way to
34309 detect whether an update has removed children (which necessarily can
34310 only happen at the end of the update range).
34313 The display hint, if any.
34316 This is an integer value, which will be 1 if there are more children
34317 available outside the varobj's update range.
34320 This attribute will be present and have the value @samp{1} if the
34321 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34322 then this attribute will not be present.
34325 If new children were added to a dynamic varobj within the selected
34326 update range (as set by @code{-var-set-update-range}), then they will
34327 be listed in this attribute.
34330 @subsubheading Example
34337 -var-update --all-values var1
34338 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34339 type_changed="false"@}]
34343 @subheading The @code{-var-set-frozen} Command
34344 @findex -var-set-frozen
34345 @anchor{-var-set-frozen}
34347 @subsubheading Synopsis
34350 -var-set-frozen @var{name} @var{flag}
34353 Set the frozenness flag on the variable object @var{name}. The
34354 @var{flag} parameter should be either @samp{1} to make the variable
34355 frozen or @samp{0} to make it unfrozen. If a variable object is
34356 frozen, then neither itself, nor any of its children, are
34357 implicitly updated by @code{-var-update} of
34358 a parent variable or by @code{-var-update *}. Only
34359 @code{-var-update} of the variable itself will update its value and
34360 values of its children. After a variable object is unfrozen, it is
34361 implicitly updated by all subsequent @code{-var-update} operations.
34362 Unfreezing a variable does not update it, only subsequent
34363 @code{-var-update} does.
34365 @subsubheading Example
34369 -var-set-frozen V 1
34374 @subheading The @code{-var-set-update-range} command
34375 @findex -var-set-update-range
34376 @anchor{-var-set-update-range}
34378 @subsubheading Synopsis
34381 -var-set-update-range @var{name} @var{from} @var{to}
34384 Set the range of children to be returned by future invocations of
34385 @code{-var-update}.
34387 @var{from} and @var{to} indicate the range of children to report. If
34388 @var{from} or @var{to} is less than zero, the range is reset and all
34389 children will be reported. Otherwise, children starting at @var{from}
34390 (zero-based) and up to and excluding @var{to} will be reported.
34392 @subsubheading Example
34396 -var-set-update-range V 1 2
34400 @subheading The @code{-var-set-visualizer} command
34401 @findex -var-set-visualizer
34402 @anchor{-var-set-visualizer}
34404 @subsubheading Synopsis
34407 -var-set-visualizer @var{name} @var{visualizer}
34410 Set a visualizer for the variable object @var{name}.
34412 @var{visualizer} is the visualizer to use. The special value
34413 @samp{None} means to disable any visualizer in use.
34415 If not @samp{None}, @var{visualizer} must be a Python expression.
34416 This expression must evaluate to a callable object which accepts a
34417 single argument. @value{GDBN} will call this object with the value of
34418 the varobj @var{name} as an argument (this is done so that the same
34419 Python pretty-printing code can be used for both the CLI and MI).
34420 When called, this object must return an object which conforms to the
34421 pretty-printing interface (@pxref{Pretty Printing API}).
34423 The pre-defined function @code{gdb.default_visualizer} may be used to
34424 select a visualizer by following the built-in process
34425 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34426 a varobj is created, and so ordinarily is not needed.
34428 This feature is only available if Python support is enabled. The MI
34429 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34430 can be used to check this.
34432 @subsubheading Example
34434 Resetting the visualizer:
34438 -var-set-visualizer V None
34442 Reselecting the default (type-based) visualizer:
34446 -var-set-visualizer V gdb.default_visualizer
34450 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34451 can be used to instantiate this class for a varobj:
34455 -var-set-visualizer V "lambda val: SomeClass()"
34459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34460 @node GDB/MI Data Manipulation
34461 @section @sc{gdb/mi} Data Manipulation
34463 @cindex data manipulation, in @sc{gdb/mi}
34464 @cindex @sc{gdb/mi}, data manipulation
34465 This section describes the @sc{gdb/mi} commands that manipulate data:
34466 examine memory and registers, evaluate expressions, etc.
34468 For details about what an addressable memory unit is,
34469 @pxref{addressable memory unit}.
34471 @c REMOVED FROM THE INTERFACE.
34472 @c @subheading -data-assign
34473 @c Change the value of a program variable. Plenty of side effects.
34474 @c @subsubheading GDB Command
34476 @c @subsubheading Example
34479 @subheading The @code{-data-disassemble} Command
34480 @findex -data-disassemble
34482 @subsubheading Synopsis
34486 [ -s @var{start-addr} -e @var{end-addr} ]
34487 | [ -a @var{addr} ]
34488 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34496 @item @var{start-addr}
34497 is the beginning address (or @code{$pc})
34498 @item @var{end-addr}
34501 is an address anywhere within (or the name of) the function to
34502 disassemble. If an address is specified, the whole function
34503 surrounding that address will be disassembled. If a name is
34504 specified, the whole function with that name will be disassembled.
34505 @item @var{filename}
34506 is the name of the file to disassemble
34507 @item @var{linenum}
34508 is the line number to disassemble around
34510 is the number of disassembly lines to be produced. If it is -1,
34511 the whole function will be disassembled, in case no @var{end-addr} is
34512 specified. If @var{end-addr} is specified as a non-zero value, and
34513 @var{lines} is lower than the number of disassembly lines between
34514 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34515 displayed; if @var{lines} is higher than the number of lines between
34516 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34521 @item 0 disassembly only
34522 @item 1 mixed source and disassembly (deprecated)
34523 @item 2 disassembly with raw opcodes
34524 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34525 @item 4 mixed source and disassembly
34526 @item 5 mixed source and disassembly with raw opcodes
34529 Modes 1 and 3 are deprecated. The output is ``source centric''
34530 which hasn't proved useful in practice.
34531 @xref{Machine Code}, for a discussion of the difference between
34532 @code{/m} and @code{/s} output of the @code{disassemble} command.
34535 @subsubheading Result
34537 The result of the @code{-data-disassemble} command will be a list named
34538 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34539 used with the @code{-data-disassemble} command.
34541 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34546 The address at which this instruction was disassembled.
34549 The name of the function this instruction is within.
34552 The decimal offset in bytes from the start of @samp{func-name}.
34555 The text disassembly for this @samp{address}.
34558 This field is only present for modes 2, 3 and 5. This contains the
34559 raw opcode bytes for the @samp{inst} field. The bytes are formatted
34560 as single bytes, in hex, in ascending address order, with a single
34561 space between each byte.
34565 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34566 @samp{src_and_asm_line}, each of which has the following fields:
34570 The line number within @samp{file}.
34573 The file name from the compilation unit. This might be an absolute
34574 file name or a relative file name depending on the compile command
34578 Absolute file name of @samp{file}. It is converted to a canonical form
34579 using the source file search path
34580 (@pxref{Source Path, ,Specifying Source Directories})
34581 and after resolving all the symbolic links.
34583 If the source file is not found this field will contain the path as
34584 present in the debug information.
34586 @item line_asm_insn
34587 This is a list of tuples containing the disassembly for @samp{line} in
34588 @samp{file}. The fields of each tuple are the same as for
34589 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34590 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34595 Note that whatever included in the @samp{inst} field, is not
34596 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34599 @subsubheading @value{GDBN} Command
34601 The corresponding @value{GDBN} command is @samp{disassemble}.
34603 @subsubheading Example
34605 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34609 -data-disassemble -s $pc -e "$pc + 20" -- 0
34612 @{address="0x000107c0",func-name="main",offset="4",
34613 inst="mov 2, %o0"@},
34614 @{address="0x000107c4",func-name="main",offset="8",
34615 inst="sethi %hi(0x11800), %o2"@},
34616 @{address="0x000107c8",func-name="main",offset="12",
34617 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34618 @{address="0x000107cc",func-name="main",offset="16",
34619 inst="sethi %hi(0x11800), %o2"@},
34620 @{address="0x000107d0",func-name="main",offset="20",
34621 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34625 Disassemble the whole @code{main} function. Line 32 is part of
34629 -data-disassemble -f basics.c -l 32 -- 0
34631 @{address="0x000107bc",func-name="main",offset="0",
34632 inst="save %sp, -112, %sp"@},
34633 @{address="0x000107c0",func-name="main",offset="4",
34634 inst="mov 2, %o0"@},
34635 @{address="0x000107c4",func-name="main",offset="8",
34636 inst="sethi %hi(0x11800), %o2"@},
34638 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34639 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34643 Disassemble 3 instructions from the start of @code{main}:
34647 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34649 @{address="0x000107bc",func-name="main",offset="0",
34650 inst="save %sp, -112, %sp"@},
34651 @{address="0x000107c0",func-name="main",offset="4",
34652 inst="mov 2, %o0"@},
34653 @{address="0x000107c4",func-name="main",offset="8",
34654 inst="sethi %hi(0x11800), %o2"@}]
34658 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34662 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34664 src_and_asm_line=@{line="31",
34665 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34666 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34667 line_asm_insn=[@{address="0x000107bc",
34668 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34669 src_and_asm_line=@{line="32",
34670 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34671 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34672 line_asm_insn=[@{address="0x000107c0",
34673 func-name="main",offset="4",inst="mov 2, %o0"@},
34674 @{address="0x000107c4",func-name="main",offset="8",
34675 inst="sethi %hi(0x11800), %o2"@}]@}]
34680 @subheading The @code{-data-evaluate-expression} Command
34681 @findex -data-evaluate-expression
34683 @subsubheading Synopsis
34686 -data-evaluate-expression @var{expr}
34689 Evaluate @var{expr} as an expression. The expression could contain an
34690 inferior function call. The function call will execute synchronously.
34691 If the expression contains spaces, it must be enclosed in double quotes.
34693 @subsubheading @value{GDBN} Command
34695 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34696 @samp{call}. In @code{gdbtk} only, there's a corresponding
34697 @samp{gdb_eval} command.
34699 @subsubheading Example
34701 In the following example, the numbers that precede the commands are the
34702 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34703 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34707 211-data-evaluate-expression A
34710 311-data-evaluate-expression &A
34711 311^done,value="0xefffeb7c"
34713 411-data-evaluate-expression A+3
34716 511-data-evaluate-expression "A + 3"
34722 @subheading The @code{-data-list-changed-registers} Command
34723 @findex -data-list-changed-registers
34725 @subsubheading Synopsis
34728 -data-list-changed-registers
34731 Display a list of the registers that have changed.
34733 @subsubheading @value{GDBN} Command
34735 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34736 has the corresponding command @samp{gdb_changed_register_list}.
34738 @subsubheading Example
34740 On a PPC MBX board:
34748 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34749 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34750 line="5",arch="powerpc"@}
34752 -data-list-changed-registers
34753 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34754 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34755 "24","25","26","27","28","30","31","64","65","66","67","69"]
34760 @subheading The @code{-data-list-register-names} Command
34761 @findex -data-list-register-names
34763 @subsubheading Synopsis
34766 -data-list-register-names [ ( @var{regno} )+ ]
34769 Show a list of register names for the current target. If no arguments
34770 are given, it shows a list of the names of all the registers. If
34771 integer numbers are given as arguments, it will print a list of the
34772 names of the registers corresponding to the arguments. To ensure
34773 consistency between a register name and its number, the output list may
34774 include empty register names.
34776 @subsubheading @value{GDBN} Command
34778 @value{GDBN} does not have a command which corresponds to
34779 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34780 corresponding command @samp{gdb_regnames}.
34782 @subsubheading Example
34784 For the PPC MBX board:
34787 -data-list-register-names
34788 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34789 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34790 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34791 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34792 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34793 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34794 "", "pc","ps","cr","lr","ctr","xer"]
34796 -data-list-register-names 1 2 3
34797 ^done,register-names=["r1","r2","r3"]
34801 @subheading The @code{-data-list-register-values} Command
34802 @findex -data-list-register-values
34804 @subsubheading Synopsis
34807 -data-list-register-values
34808 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34811 Display the registers' contents. The format according to which the
34812 registers' contents are to be returned is given by @var{fmt}, followed
34813 by an optional list of numbers specifying the registers to display. A
34814 missing list of numbers indicates that the contents of all the
34815 registers must be returned. The @code{--skip-unavailable} option
34816 indicates that only the available registers are to be returned.
34818 Allowed formats for @var{fmt} are:
34835 @subsubheading @value{GDBN} Command
34837 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34838 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34840 @subsubheading Example
34842 For a PPC MBX board (note: line breaks are for readability only, they
34843 don't appear in the actual output):
34847 -data-list-register-values r 64 65
34848 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34849 @{number="65",value="0x00029002"@}]
34851 -data-list-register-values x
34852 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34853 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34854 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34855 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34856 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34857 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34858 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34859 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34860 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34861 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34862 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34863 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34864 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34865 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34866 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34867 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34868 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34869 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34870 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34871 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34872 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34873 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34874 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34875 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34876 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34877 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34878 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34879 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34880 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34881 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34882 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34883 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34884 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34885 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34886 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34887 @{number="69",value="0x20002b03"@}]
34892 @subheading The @code{-data-read-memory} Command
34893 @findex -data-read-memory
34895 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34897 @subsubheading Synopsis
34900 -data-read-memory [ -o @var{byte-offset} ]
34901 @var{address} @var{word-format} @var{word-size}
34902 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34909 @item @var{address}
34910 An expression specifying the address of the first memory word to be
34911 read. Complex expressions containing embedded white space should be
34912 quoted using the C convention.
34914 @item @var{word-format}
34915 The format to be used to print the memory words. The notation is the
34916 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34919 @item @var{word-size}
34920 The size of each memory word in bytes.
34922 @item @var{nr-rows}
34923 The number of rows in the output table.
34925 @item @var{nr-cols}
34926 The number of columns in the output table.
34929 If present, indicates that each row should include an @sc{ascii} dump. The
34930 value of @var{aschar} is used as a padding character when a byte is not a
34931 member of the printable @sc{ascii} character set (printable @sc{ascii}
34932 characters are those whose code is between 32 and 126, inclusively).
34934 @item @var{byte-offset}
34935 An offset to add to the @var{address} before fetching memory.
34938 This command displays memory contents as a table of @var{nr-rows} by
34939 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34940 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34941 (returned as @samp{total-bytes}). Should less than the requested number
34942 of bytes be returned by the target, the missing words are identified
34943 using @samp{N/A}. The number of bytes read from the target is returned
34944 in @samp{nr-bytes} and the starting address used to read memory in
34947 The address of the next/previous row or page is available in
34948 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34951 @subsubheading @value{GDBN} Command
34953 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34954 @samp{gdb_get_mem} memory read command.
34956 @subsubheading Example
34958 Read six bytes of memory starting at @code{bytes+6} but then offset by
34959 @code{-6} bytes. Format as three rows of two columns. One byte per
34960 word. Display each word in hex.
34964 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34965 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34966 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34967 prev-page="0x0000138a",memory=[
34968 @{addr="0x00001390",data=["0x00","0x01"]@},
34969 @{addr="0x00001392",data=["0x02","0x03"]@},
34970 @{addr="0x00001394",data=["0x04","0x05"]@}]
34974 Read two bytes of memory starting at address @code{shorts + 64} and
34975 display as a single word formatted in decimal.
34979 5-data-read-memory shorts+64 d 2 1 1
34980 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34981 next-row="0x00001512",prev-row="0x0000150e",
34982 next-page="0x00001512",prev-page="0x0000150e",memory=[
34983 @{addr="0x00001510",data=["128"]@}]
34987 Read thirty two bytes of memory starting at @code{bytes+16} and format
34988 as eight rows of four columns. Include a string encoding with @samp{x}
34989 used as the non-printable character.
34993 4-data-read-memory bytes+16 x 1 8 4 x
34994 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34995 next-row="0x000013c0",prev-row="0x0000139c",
34996 next-page="0x000013c0",prev-page="0x00001380",memory=[
34997 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34998 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34999 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
35000 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
35001 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
35002 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
35003 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
35004 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
35008 @subheading The @code{-data-read-memory-bytes} Command
35009 @findex -data-read-memory-bytes
35011 @subsubheading Synopsis
35014 -data-read-memory-bytes [ -o @var{offset} ]
35015 @var{address} @var{count}
35022 @item @var{address}
35023 An expression specifying the address of the first addressable memory unit
35024 to be read. Complex expressions containing embedded white space should be
35025 quoted using the C convention.
35028 The number of addressable memory units to read. This should be an integer
35032 The offset relative to @var{address} at which to start reading. This
35033 should be an integer literal. This option is provided so that a frontend
35034 is not required to first evaluate address and then perform address
35035 arithmetics itself.
35039 This command attempts to read all accessible memory regions in the
35040 specified range. First, all regions marked as unreadable in the memory
35041 map (if one is defined) will be skipped. @xref{Memory Region
35042 Attributes}. Second, @value{GDBN} will attempt to read the remaining
35043 regions. For each one, if reading full region results in an errors,
35044 @value{GDBN} will try to read a subset of the region.
35046 In general, every single memory unit in the region may be readable or not,
35047 and the only way to read every readable unit is to try a read at
35048 every address, which is not practical. Therefore, @value{GDBN} will
35049 attempt to read all accessible memory units at either beginning or the end
35050 of the region, using a binary division scheme. This heuristic works
35051 well for reading across a memory map boundary. Note that if a region
35052 has a readable range that is neither at the beginning or the end,
35053 @value{GDBN} will not read it.
35055 The result record (@pxref{GDB/MI Result Records}) that is output of
35056 the command includes a field named @samp{memory} whose content is a
35057 list of tuples. Each tuple represent a successfully read memory block
35058 and has the following fields:
35062 The start address of the memory block, as hexadecimal literal.
35065 The end address of the memory block, as hexadecimal literal.
35068 The offset of the memory block, as hexadecimal literal, relative to
35069 the start address passed to @code{-data-read-memory-bytes}.
35072 The contents of the memory block, in hex.
35078 @subsubheading @value{GDBN} Command
35080 The corresponding @value{GDBN} command is @samp{x}.
35082 @subsubheading Example
35086 -data-read-memory-bytes &a 10
35087 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
35089 contents="01000000020000000300"@}]
35094 @subheading The @code{-data-write-memory-bytes} Command
35095 @findex -data-write-memory-bytes
35097 @subsubheading Synopsis
35100 -data-write-memory-bytes @var{address} @var{contents}
35101 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
35108 @item @var{address}
35109 An expression specifying the address of the first addressable memory unit
35110 to be written. Complex expressions containing embedded white space should
35111 be quoted using the C convention.
35113 @item @var{contents}
35114 The hex-encoded data to write. It is an error if @var{contents} does
35115 not represent an integral number of addressable memory units.
35118 Optional argument indicating the number of addressable memory units to be
35119 written. If @var{count} is greater than @var{contents}' length,
35120 @value{GDBN} will repeatedly write @var{contents} until it fills
35121 @var{count} memory units.
35125 @subsubheading @value{GDBN} Command
35127 There's no corresponding @value{GDBN} command.
35129 @subsubheading Example
35133 -data-write-memory-bytes &a "aabbccdd"
35140 -data-write-memory-bytes &a "aabbccdd" 16e
35145 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35146 @node GDB/MI Tracepoint Commands
35147 @section @sc{gdb/mi} Tracepoint Commands
35149 The commands defined in this section implement MI support for
35150 tracepoints. For detailed introduction, see @ref{Tracepoints}.
35152 @subheading The @code{-trace-find} Command
35153 @findex -trace-find
35155 @subsubheading Synopsis
35158 -trace-find @var{mode} [@var{parameters}@dots{}]
35161 Find a trace frame using criteria defined by @var{mode} and
35162 @var{parameters}. The following table lists permissible
35163 modes and their parameters. For details of operation, see @ref{tfind}.
35168 No parameters are required. Stops examining trace frames.
35171 An integer is required as parameter. Selects tracepoint frame with
35174 @item tracepoint-number
35175 An integer is required as parameter. Finds next
35176 trace frame that corresponds to tracepoint with the specified number.
35179 An address is required as parameter. Finds
35180 next trace frame that corresponds to any tracepoint at the specified
35183 @item pc-inside-range
35184 Two addresses are required as parameters. Finds next trace
35185 frame that corresponds to a tracepoint at an address inside the
35186 specified range. Both bounds are considered to be inside the range.
35188 @item pc-outside-range
35189 Two addresses are required as parameters. Finds
35190 next trace frame that corresponds to a tracepoint at an address outside
35191 the specified range. Both bounds are considered to be inside the range.
35194 Location specification is required as parameter. @xref{Location Specifications}.
35195 Finds next trace frame that corresponds to a tracepoint at
35196 the specified location.
35200 If @samp{none} was passed as @var{mode}, the response does not
35201 have fields. Otherwise, the response may have the following fields:
35205 This field has either @samp{0} or @samp{1} as the value, depending
35206 on whether a matching tracepoint was found.
35209 The index of the found traceframe. This field is present iff
35210 the @samp{found} field has value of @samp{1}.
35213 The index of the found tracepoint. This field is present iff
35214 the @samp{found} field has value of @samp{1}.
35217 The information about the frame corresponding to the found trace
35218 frame. This field is present only if a trace frame was found.
35219 @xref{GDB/MI Frame Information}, for description of this field.
35223 @subsubheading @value{GDBN} Command
35225 The corresponding @value{GDBN} command is @samp{tfind}.
35227 @subheading -trace-define-variable
35228 @findex -trace-define-variable
35230 @subsubheading Synopsis
35233 -trace-define-variable @var{name} [ @var{value} ]
35236 Create trace variable @var{name} if it does not exist. If
35237 @var{value} is specified, sets the initial value of the specified
35238 trace variable to that value. Note that the @var{name} should start
35239 with the @samp{$} character.
35241 @subsubheading @value{GDBN} Command
35243 The corresponding @value{GDBN} command is @samp{tvariable}.
35245 @subheading The @code{-trace-frame-collected} Command
35246 @findex -trace-frame-collected
35248 @subsubheading Synopsis
35251 -trace-frame-collected
35252 [--var-print-values @var{var_pval}]
35253 [--comp-print-values @var{comp_pval}]
35254 [--registers-format @var{regformat}]
35255 [--memory-contents]
35258 This command returns the set of collected objects, register names,
35259 trace state variable names, memory ranges and computed expressions
35260 that have been collected at a particular trace frame. The optional
35261 parameters to the command affect the output format in different ways.
35262 See the output description table below for more details.
35264 The reported names can be used in the normal manner to create
35265 varobjs and inspect the objects themselves. The items returned by
35266 this command are categorized so that it is clear which is a variable,
35267 which is a register, which is a trace state variable, which is a
35268 memory range and which is a computed expression.
35270 For instance, if the actions were
35272 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
35273 collect *(int*)0xaf02bef0@@40
35277 the object collected in its entirety would be @code{myVar}. The
35278 object @code{myArray} would be partially collected, because only the
35279 element at index @code{myIndex} would be collected. The remaining
35280 objects would be computed expressions.
35282 An example output would be:
35286 -trace-frame-collected
35288 explicit-variables=[@{name="myVar",value="1"@}],
35289 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
35290 @{name="myObj.field",value="0"@},
35291 @{name="myPtr->field",value="1"@},
35292 @{name="myCount + 2",value="3"@},
35293 @{name="$tvar1 + 1",value="43970027"@}],
35294 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35295 @{number="1",value="0x0"@},
35296 @{number="2",value="0x4"@},
35298 @{number="125",value="0x0"@}],
35299 tvars=[@{name="$tvar1",current="43970026"@}],
35300 memory=[@{address="0x0000000000602264",length="4"@},
35301 @{address="0x0000000000615bc0",length="4"@}]
35308 @item explicit-variables
35309 The set of objects that have been collected in their entirety (as
35310 opposed to collecting just a few elements of an array or a few struct
35311 members). For each object, its name and value are printed.
35312 The @code{--var-print-values} option affects how or whether the value
35313 field is output. If @var{var_pval} is 0, then print only the names;
35314 if it is 1, print also their values; and if it is 2, print the name,
35315 type and value for simple data types, and the name and type for
35316 arrays, structures and unions.
35318 @item computed-expressions
35319 The set of computed expressions that have been collected at the
35320 current trace frame. The @code{--comp-print-values} option affects
35321 this set like the @code{--var-print-values} option affects the
35322 @code{explicit-variables} set. See above.
35325 The registers that have been collected at the current trace frame.
35326 For each register collected, the name and current value are returned.
35327 The value is formatted according to the @code{--registers-format}
35328 option. See the @command{-data-list-register-values} command for a
35329 list of the allowed formats. The default is @samp{x}.
35332 The trace state variables that have been collected at the current
35333 trace frame. For each trace state variable collected, the name and
35334 current value are returned.
35337 The set of memory ranges that have been collected at the current trace
35338 frame. Its content is a list of tuples. Each tuple represents a
35339 collected memory range and has the following fields:
35343 The start address of the memory range, as hexadecimal literal.
35346 The length of the memory range, as decimal literal.
35349 The contents of the memory block, in hex. This field is only present
35350 if the @code{--memory-contents} option is specified.
35356 @subsubheading @value{GDBN} Command
35358 There is no corresponding @value{GDBN} command.
35360 @subsubheading Example
35362 @subheading -trace-list-variables
35363 @findex -trace-list-variables
35365 @subsubheading Synopsis
35368 -trace-list-variables
35371 Return a table of all defined trace variables. Each element of the
35372 table has the following fields:
35376 The name of the trace variable. This field is always present.
35379 The initial value. This is a 64-bit signed integer. This
35380 field is always present.
35383 The value the trace variable has at the moment. This is a 64-bit
35384 signed integer. This field is absent iff current value is
35385 not defined, for example if the trace was never run, or is
35390 @subsubheading @value{GDBN} Command
35392 The corresponding @value{GDBN} command is @samp{tvariables}.
35394 @subsubheading Example
35398 -trace-list-variables
35399 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35400 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35401 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35402 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35403 body=[variable=@{name="$trace_timestamp",initial="0"@}
35404 variable=@{name="$foo",initial="10",current="15"@}]@}
35408 @subheading -trace-save
35409 @findex -trace-save
35411 @subsubheading Synopsis
35414 -trace-save [ -r ] [ -ctf ] @var{filename}
35417 Saves the collected trace data to @var{filename}. Without the
35418 @samp{-r} option, the data is downloaded from the target and saved
35419 in a local file. With the @samp{-r} option the target is asked
35420 to perform the save.
35422 By default, this command will save the trace in the tfile format. You can
35423 supply the optional @samp{-ctf} argument to save it the CTF format. See
35424 @ref{Trace Files} for more information about CTF.
35426 @subsubheading @value{GDBN} Command
35428 The corresponding @value{GDBN} command is @samp{tsave}.
35431 @subheading -trace-start
35432 @findex -trace-start
35434 @subsubheading Synopsis
35440 Starts a tracing experiment. The result of this command does not
35443 @subsubheading @value{GDBN} Command
35445 The corresponding @value{GDBN} command is @samp{tstart}.
35447 @subheading -trace-status
35448 @findex -trace-status
35450 @subsubheading Synopsis
35456 Obtains the status of a tracing experiment. The result may include
35457 the following fields:
35462 May have a value of either @samp{0}, when no tracing operations are
35463 supported, @samp{1}, when all tracing operations are supported, or
35464 @samp{file} when examining trace file. In the latter case, examining
35465 of trace frame is possible but new tracing experiement cannot be
35466 started. This field is always present.
35469 May have a value of either @samp{0} or @samp{1} depending on whether
35470 tracing experiement is in progress on target. This field is present
35471 if @samp{supported} field is not @samp{0}.
35474 Report the reason why the tracing was stopped last time. This field
35475 may be absent iff tracing was never stopped on target yet. The
35476 value of @samp{request} means the tracing was stopped as result of
35477 the @code{-trace-stop} command. The value of @samp{overflow} means
35478 the tracing buffer is full. The value of @samp{disconnection} means
35479 tracing was automatically stopped when @value{GDBN} has disconnected.
35480 The value of @samp{passcount} means tracing was stopped when a
35481 tracepoint was passed a maximal number of times for that tracepoint.
35482 This field is present if @samp{supported} field is not @samp{0}.
35484 @item stopping-tracepoint
35485 The number of tracepoint whose passcount as exceeded. This field is
35486 present iff the @samp{stop-reason} field has the value of
35490 @itemx frames-created
35491 The @samp{frames} field is a count of the total number of trace frames
35492 in the trace buffer, while @samp{frames-created} is the total created
35493 during the run, including ones that were discarded, such as when a
35494 circular trace buffer filled up. Both fields are optional.
35498 These fields tell the current size of the tracing buffer and the
35499 remaining space. These fields are optional.
35502 The value of the circular trace buffer flag. @code{1} means that the
35503 trace buffer is circular and old trace frames will be discarded if
35504 necessary to make room, @code{0} means that the trace buffer is linear
35508 The value of the disconnected tracing flag. @code{1} means that
35509 tracing will continue after @value{GDBN} disconnects, @code{0} means
35510 that the trace run will stop.
35513 The filename of the trace file being examined. This field is
35514 optional, and only present when examining a trace file.
35518 @subsubheading @value{GDBN} Command
35520 The corresponding @value{GDBN} command is @samp{tstatus}.
35522 @subheading -trace-stop
35523 @findex -trace-stop
35525 @subsubheading Synopsis
35531 Stops a tracing experiment. The result of this command has the same
35532 fields as @code{-trace-status}, except that the @samp{supported} and
35533 @samp{running} fields are not output.
35535 @subsubheading @value{GDBN} Command
35537 The corresponding @value{GDBN} command is @samp{tstop}.
35540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35541 @node GDB/MI Symbol Query
35542 @section @sc{gdb/mi} Symbol Query Commands
35546 @subheading The @code{-symbol-info-address} Command
35547 @findex -symbol-info-address
35549 @subsubheading Synopsis
35552 -symbol-info-address @var{symbol}
35555 Describe where @var{symbol} is stored.
35557 @subsubheading @value{GDBN} Command
35559 The corresponding @value{GDBN} command is @samp{info address}.
35561 @subsubheading Example
35565 @subheading The @code{-symbol-info-file} Command
35566 @findex -symbol-info-file
35568 @subsubheading Synopsis
35574 Show the file for the symbol.
35576 @subsubheading @value{GDBN} Command
35578 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35579 @samp{gdb_find_file}.
35581 @subsubheading Example
35585 @subheading The @code{-symbol-info-functions} Command
35586 @findex -symbol-info-functions
35587 @anchor{-symbol-info-functions}
35589 @subsubheading Synopsis
35592 -symbol-info-functions [--include-nondebug]
35593 [--type @var{type_regexp}]
35594 [--name @var{name_regexp}]
35595 [--max-results @var{limit}]
35599 Return a list containing the names and types for all global functions
35600 taken from the debug information. The functions are grouped by source
35601 file, and shown with the line number on which each function is
35604 The @code{--include-nondebug} option causes the output to include
35605 code symbols from the symbol table.
35607 The options @code{--type} and @code{--name} allow the symbols returned
35608 to be filtered based on either the name of the function, or the type
35609 signature of the function.
35611 The option @code{--max-results} restricts the command to return no
35612 more than @var{limit} results. If exactly @var{limit} results are
35613 returned then there might be additional results available if a higher
35616 @subsubheading @value{GDBN} Command
35618 The corresponding @value{GDBN} command is @samp{info functions}.
35620 @subsubheading Example
35624 -symbol-info-functions
35627 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35628 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35629 symbols=[@{line="36", name="f4", type="void (int *)",
35630 description="void f4(int *);"@},
35631 @{line="42", name="main", type="int ()",
35632 description="int main();"@},
35633 @{line="30", name="f1", type="my_int_t (int, int)",
35634 description="static my_int_t f1(int, int);"@}]@},
35635 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35636 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35637 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35638 description="float f2(another_float_t);"@},
35639 @{line="39", name="f3", type="int (another_int_t)",
35640 description="int f3(another_int_t);"@},
35641 @{line="27", name="f1", type="another_float_t (int)",
35642 description="static another_float_t f1(int);"@}]@}]@}
35646 -symbol-info-functions --name f1
35649 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35650 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35651 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35652 description="static my_int_t f1(int, int);"@}]@},
35653 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35654 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35655 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35656 description="static another_float_t f1(int);"@}]@}]@}
35660 -symbol-info-functions --type void
35663 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35664 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35665 symbols=[@{line="36", name="f4", type="void (int *)",
35666 description="void f4(int *);"@}]@}]@}
35670 -symbol-info-functions --include-nondebug
35673 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35674 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35675 symbols=[@{line="36", name="f4", type="void (int *)",
35676 description="void f4(int *);"@},
35677 @{line="42", name="main", type="int ()",
35678 description="int main();"@},
35679 @{line="30", name="f1", type="my_int_t (int, int)",
35680 description="static my_int_t f1(int, int);"@}]@},
35681 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35682 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35683 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35684 description="float f2(another_float_t);"@},
35685 @{line="39", name="f3", type="int (another_int_t)",
35686 description="int f3(another_int_t);"@},
35687 @{line="27", name="f1", type="another_float_t (int)",
35688 description="static another_float_t f1(int);"@}]@}],
35690 [@{address="0x0000000000400398",name="_init"@},
35691 @{address="0x00000000004003b0",name="_start"@},
35697 @subheading The @code{-symbol-info-module-functions} Command
35698 @findex -symbol-info-module-functions
35699 @anchor{-symbol-info-module-functions}
35701 @subsubheading Synopsis
35704 -symbol-info-module-functions [--module @var{module_regexp}]
35705 [--name @var{name_regexp}]
35706 [--type @var{type_regexp}]
35710 Return a list containing the names of all known functions within all
35711 know Fortran modules. The functions are grouped by source file and
35712 containing module, and shown with the line number on which each
35713 function is defined.
35715 The option @code{--module} only returns results for modules matching
35716 @var{module_regexp}. The option @code{--name} only returns functions
35717 whose name matches @var{name_regexp}, and @code{--type} only returns
35718 functions whose type matches @var{type_regexp}.
35720 @subsubheading @value{GDBN} Command
35722 The corresponding @value{GDBN} command is @samp{info module functions}.
35724 @subsubheading Example
35729 -symbol-info-module-functions
35732 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35733 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35734 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35735 description="void mod1::check_all(void);"@}]@}]@},
35737 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35738 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35739 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35740 description="void mod2::check_var_i(void);"@}]@}]@},
35742 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35743 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35744 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35745 description="void mod3::check_all(void);"@},
35746 @{line="27",name="mod3::check_mod2",type="void (void)",
35747 description="void mod3::check_mod2(void);"@}]@}]@},
35748 @{module="modmany",
35749 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35750 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35751 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35752 description="void modmany::check_some(void);"@}]@}]@},
35754 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35755 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35756 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35757 description="void moduse::check_all(void);"@},
35758 @{line="49",name="moduse::check_var_x",type="void (void)",
35759 description="void moduse::check_var_x(void);"@}]@}]@}]
35763 @subheading The @code{-symbol-info-module-variables} Command
35764 @findex -symbol-info-module-variables
35765 @anchor{-symbol-info-module-variables}
35767 @subsubheading Synopsis
35770 -symbol-info-module-variables [--module @var{module_regexp}]
35771 [--name @var{name_regexp}]
35772 [--type @var{type_regexp}]
35776 Return a list containing the names of all known variables within all
35777 know Fortran modules. The variables are grouped by source file and
35778 containing module, and shown with the line number on which each
35779 variable is defined.
35781 The option @code{--module} only returns results for modules matching
35782 @var{module_regexp}. The option @code{--name} only returns variables
35783 whose name matches @var{name_regexp}, and @code{--type} only returns
35784 variables whose type matches @var{type_regexp}.
35786 @subsubheading @value{GDBN} Command
35788 The corresponding @value{GDBN} command is @samp{info module variables}.
35790 @subsubheading Example
35795 -symbol-info-module-variables
35798 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35799 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35800 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35801 description="integer(kind=4) mod1::var_const;"@},
35802 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35803 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35805 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35806 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35807 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35808 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35810 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35811 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35812 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35813 description="integer(kind=4) mod3::mod1;"@},
35814 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35815 description="integer(kind=4) mod3::mod2;"@},
35816 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35817 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35818 @{module="modmany",
35819 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35820 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35821 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35822 description="integer(kind=4) modmany::var_a;"@},
35823 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35824 description="integer(kind=4) modmany::var_b;"@},
35825 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35826 description="integer(kind=4) modmany::var_c;"@},
35827 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35828 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35830 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35831 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35832 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35833 description="integer(kind=4) moduse::var_x;"@},
35834 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35835 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35839 @subheading The @code{-symbol-info-modules} Command
35840 @findex -symbol-info-modules
35841 @anchor{-symbol-info-modules}
35843 @subsubheading Synopsis
35846 -symbol-info-modules [--name @var{name_regexp}]
35847 [--max-results @var{limit}]
35852 Return a list containing the names of all known Fortran modules. The
35853 modules are grouped by source file, and shown with the line number on
35854 which each modules is defined.
35856 The option @code{--name} allows the modules returned to be filtered
35857 based the name of the module.
35859 The option @code{--max-results} restricts the command to return no
35860 more than @var{limit} results. If exactly @var{limit} results are
35861 returned then there might be additional results available if a higher
35864 @subsubheading @value{GDBN} Command
35866 The corresponding @value{GDBN} command is @samp{info modules}.
35868 @subsubheading Example
35872 -symbol-info-modules
35875 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35876 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35877 symbols=[@{line="16",name="mod1"@},
35878 @{line="22",name="mod2"@}]@},
35879 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35880 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35881 symbols=[@{line="16",name="mod3"@},
35882 @{line="22",name="modmany"@},
35883 @{line="26",name="moduse"@}]@}]@}
35887 -symbol-info-modules --name mod[123]
35890 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35891 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35892 symbols=[@{line="16",name="mod1"@},
35893 @{line="22",name="mod2"@}]@},
35894 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35895 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35896 symbols=[@{line="16",name="mod3"@}]@}]@}
35900 @subheading The @code{-symbol-info-types} Command
35901 @findex -symbol-info-types
35902 @anchor{-symbol-info-types}
35904 @subsubheading Synopsis
35907 -symbol-info-types [--name @var{name_regexp}]
35908 [--max-results @var{limit}]
35913 Return a list of all defined types. The types are grouped by source
35914 file, and shown with the line number on which each user defined type
35915 is defined. Some base types are not defined in the source code but
35916 are added to the debug information by the compiler, for example
35917 @code{int}, @code{float}, etc.; these types do not have an associated
35920 The option @code{--name} allows the list of types returned to be
35923 The option @code{--max-results} restricts the command to return no
35924 more than @var{limit} results. If exactly @var{limit} results are
35925 returned then there might be additional results available if a higher
35928 @subsubheading @value{GDBN} Command
35930 The corresponding @value{GDBN} command is @samp{info types}.
35932 @subsubheading Example
35939 [@{filename="gdb.mi/mi-sym-info-1.c",
35940 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35941 symbols=[@{name="float"@},
35943 @{line="27",name="typedef int my_int_t;"@}]@},
35944 @{filename="gdb.mi/mi-sym-info-2.c",
35945 fullname="/project/gdb.mi/mi-sym-info-2.c",
35946 symbols=[@{line="24",name="typedef float another_float_t;"@},
35947 @{line="23",name="typedef int another_int_t;"@},
35949 @{name="int"@}]@}]@}
35953 -symbol-info-types --name _int_
35956 [@{filename="gdb.mi/mi-sym-info-1.c",
35957 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35958 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35959 @{filename="gdb.mi/mi-sym-info-2.c",
35960 fullname="/project/gdb.mi/mi-sym-info-2.c",
35961 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35965 @subheading The @code{-symbol-info-variables} Command
35966 @findex -symbol-info-variables
35967 @anchor{-symbol-info-variables}
35969 @subsubheading Synopsis
35972 -symbol-info-variables [--include-nondebug]
35973 [--type @var{type_regexp}]
35974 [--name @var{name_regexp}]
35975 [--max-results @var{limit}]
35980 Return a list containing the names and types for all global variables
35981 taken from the debug information. The variables are grouped by source
35982 file, and shown with the line number on which each variable is
35985 The @code{--include-nondebug} option causes the output to include
35986 data symbols from the symbol table.
35988 The options @code{--type} and @code{--name} allow the symbols returned
35989 to be filtered based on either the name of the variable, or the type
35992 The option @code{--max-results} restricts the command to return no
35993 more than @var{limit} results. If exactly @var{limit} results are
35994 returned then there might be additional results available if a higher
35997 @subsubheading @value{GDBN} Command
35999 The corresponding @value{GDBN} command is @samp{info variables}.
36001 @subsubheading Example
36005 -symbol-info-variables
36008 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36009 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36010 symbols=[@{line="25",name="global_f1",type="float",
36011 description="static float global_f1;"@},
36012 @{line="24",name="global_i1",type="int",
36013 description="static int global_i1;"@}]@},
36014 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36015 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36016 symbols=[@{line="21",name="global_f2",type="int",
36017 description="int global_f2;"@},
36018 @{line="20",name="global_i2",type="int",
36019 description="int global_i2;"@},
36020 @{line="19",name="global_f1",type="float",
36021 description="static float global_f1;"@},
36022 @{line="18",name="global_i1",type="int",
36023 description="static int global_i1;"@}]@}]@}
36027 -symbol-info-variables --name f1
36030 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36031 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36032 symbols=[@{line="25",name="global_f1",type="float",
36033 description="static float global_f1;"@}]@},
36034 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36035 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36036 symbols=[@{line="19",name="global_f1",type="float",
36037 description="static float global_f1;"@}]@}]@}
36041 -symbol-info-variables --type float
36044 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36045 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36046 symbols=[@{line="25",name="global_f1",type="float",
36047 description="static float global_f1;"@}]@},
36048 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36049 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36050 symbols=[@{line="19",name="global_f1",type="float",
36051 description="static float global_f1;"@}]@}]@}
36055 -symbol-info-variables --include-nondebug
36058 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36059 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36060 symbols=[@{line="25",name="global_f1",type="float",
36061 description="static float global_f1;"@},
36062 @{line="24",name="global_i1",type="int",
36063 description="static int global_i1;"@}]@},
36064 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36065 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36066 symbols=[@{line="21",name="global_f2",type="int",
36067 description="int global_f2;"@},
36068 @{line="20",name="global_i2",type="int",
36069 description="int global_i2;"@},
36070 @{line="19",name="global_f1",type="float",
36071 description="static float global_f1;"@},
36072 @{line="18",name="global_i1",type="int",
36073 description="static int global_i1;"@}]@}],
36075 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
36076 @{address="0x00000000004005d8",name="__dso_handle"@}
36083 @subheading The @code{-symbol-info-line} Command
36084 @findex -symbol-info-line
36086 @subsubheading Synopsis
36092 Show the core addresses of the code for a source line.
36094 @subsubheading @value{GDBN} Command
36096 The corresponding @value{GDBN} command is @samp{info line}.
36097 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
36099 @subsubheading Example
36103 @subheading The @code{-symbol-info-symbol} Command
36104 @findex -symbol-info-symbol
36106 @subsubheading Synopsis
36109 -symbol-info-symbol @var{addr}
36112 Describe what symbol is at location @var{addr}.
36114 @subsubheading @value{GDBN} Command
36116 The corresponding @value{GDBN} command is @samp{info symbol}.
36118 @subsubheading Example
36122 @subheading The @code{-symbol-list-functions} Command
36123 @findex -symbol-list-functions
36125 @subsubheading Synopsis
36128 -symbol-list-functions
36131 List the functions in the executable.
36133 @subsubheading @value{GDBN} Command
36135 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
36136 @samp{gdb_search} in @code{gdbtk}.
36138 @subsubheading Example
36143 @subheading The @code{-symbol-list-lines} Command
36144 @findex -symbol-list-lines
36146 @subsubheading Synopsis
36149 -symbol-list-lines @var{filename}
36152 Print the list of lines that contain code and their associated program
36153 addresses for the given source filename. The entries are sorted in
36154 ascending PC order.
36156 @subsubheading @value{GDBN} Command
36158 There is no corresponding @value{GDBN} command.
36160 @subsubheading Example
36163 -symbol-list-lines basics.c
36164 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
36170 @subheading The @code{-symbol-list-types} Command
36171 @findex -symbol-list-types
36173 @subsubheading Synopsis
36179 List all the type names.
36181 @subsubheading @value{GDBN} Command
36183 The corresponding commands are @samp{info types} in @value{GDBN},
36184 @samp{gdb_search} in @code{gdbtk}.
36186 @subsubheading Example
36190 @subheading The @code{-symbol-list-variables} Command
36191 @findex -symbol-list-variables
36193 @subsubheading Synopsis
36196 -symbol-list-variables
36199 List all the global and static variable names.
36201 @subsubheading @value{GDBN} Command
36203 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
36205 @subsubheading Example
36209 @subheading The @code{-symbol-locate} Command
36210 @findex -symbol-locate
36212 @subsubheading Synopsis
36218 @subsubheading @value{GDBN} Command
36220 @samp{gdb_loc} in @code{gdbtk}.
36222 @subsubheading Example
36226 @subheading The @code{-symbol-type} Command
36227 @findex -symbol-type
36229 @subsubheading Synopsis
36232 -symbol-type @var{variable}
36235 Show type of @var{variable}.
36237 @subsubheading @value{GDBN} Command
36239 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
36240 @samp{gdb_obj_variable}.
36242 @subsubheading Example
36247 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36248 @node GDB/MI File Commands
36249 @section @sc{gdb/mi} File Commands
36251 This section describes the GDB/MI commands to specify executable file names
36252 and to read in and obtain symbol table information.
36254 @subheading The @code{-file-exec-and-symbols} Command
36255 @findex -file-exec-and-symbols
36257 @subsubheading Synopsis
36260 -file-exec-and-symbols @var{file}
36263 Specify the executable file to be debugged. This file is the one from
36264 which the symbol table is also read. If no file is specified, the
36265 command clears the executable and symbol information. If breakpoints
36266 are set when using this command with no arguments, @value{GDBN} will produce
36267 error messages. Otherwise, no output is produced, except a completion
36270 @subsubheading @value{GDBN} Command
36272 The corresponding @value{GDBN} command is @samp{file}.
36274 @subsubheading Example
36278 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36284 @subheading The @code{-file-exec-file} Command
36285 @findex -file-exec-file
36287 @subsubheading Synopsis
36290 -file-exec-file @var{file}
36293 Specify the executable file to be debugged. Unlike
36294 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36295 from this file. If used without argument, @value{GDBN} clears the information
36296 about the executable file. No output is produced, except a completion
36299 @subsubheading @value{GDBN} Command
36301 The corresponding @value{GDBN} command is @samp{exec-file}.
36303 @subsubheading Example
36307 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36314 @subheading The @code{-file-list-exec-sections} Command
36315 @findex -file-list-exec-sections
36317 @subsubheading Synopsis
36320 -file-list-exec-sections
36323 List the sections of the current executable file.
36325 @subsubheading @value{GDBN} Command
36327 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36328 information as this command. @code{gdbtk} has a corresponding command
36329 @samp{gdb_load_info}.
36331 @subsubheading Example
36336 @subheading The @code{-file-list-exec-source-file} Command
36337 @findex -file-list-exec-source-file
36339 @subsubheading Synopsis
36342 -file-list-exec-source-file
36345 List the line number, the current source file, and the absolute path
36346 to the current source file for the current executable. The macro
36347 information field has a value of @samp{1} or @samp{0} depending on
36348 whether or not the file includes preprocessor macro information.
36350 @subsubheading @value{GDBN} Command
36352 The @value{GDBN} equivalent is @samp{info source}
36354 @subsubheading Example
36358 123-file-list-exec-source-file
36359 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36364 @subheading The @code{-file-list-exec-source-files} Command
36365 @kindex info sources
36366 @findex -file-list-exec-source-files
36368 @subsubheading Synopsis
36371 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36372 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36374 @r{[} @var{regexp} @r{]}
36377 This command returns information about the source files @value{GDBN}
36378 knows about, it will output both the filename and fullname (absolute
36379 file name) of a source file, though the fullname can be elided if this
36380 information is not known to @value{GDBN}.
36382 With no arguments this command returns a list of source files. Each
36383 source file is represented by a tuple with the fields; @var{file},
36384 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36385 display name for the file, while @var{fullname} is the absolute name
36386 of the file. The @var{fullname} field can be elided if the absolute
36387 name of the source file can't be computed. The field
36388 @var{debug-fully-read} will be a string, either @code{true} or
36389 @code{false}. When @code{true}, this indicates the full debug
36390 information for the compilation unit describing this file has been
36391 read in. When @code{false}, the full debug information has not yet
36392 been read in. While reading in the full debug information it is
36393 possible that @value{GDBN} could become aware of additional source
36396 The optional @var{regexp} can be used to filter the list of source
36397 files returned. The @var{regexp} will be matched against the full
36398 source file name. The matching is case-sensitive, except on operating
36399 systems that have case-insensitive filesystem (e.g.,
36400 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36401 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36402 @var{regexp} starts with @samp{-}).
36404 If @code{--dirname} is provided, then @var{regexp} is matched only
36405 against the directory name of each source file. If @code{--basename}
36406 is provided, then @var{regexp} is matched against the basename of each
36407 source file. Only one of @code{--dirname} or @code{--basename} may be
36408 given, and if either is given then @var{regexp} is required.
36410 If @code{--group-by-objfile} is used then the format of the results is
36411 changed. The results will now be a list of tuples, with each tuple
36412 representing an object file (executable or shared library) loaded into
36413 @value{GDBN}. The fields of these tuples are; @var{filename},
36414 @var{debug-info}, and @var{sources}. The @var{filename} is the
36415 absolute name of the object file, @var{debug-info} is a string with
36416 one of the following values:
36420 This object file has no debug information.
36421 @item partially-read
36422 This object file has debug information, but it is not fully read in
36423 yet. When it is read in later, GDB might become aware of additional
36426 This object file has debug information, and this information is fully
36427 read into GDB. The list of source files is complete.
36430 The @var{sources} is a list or tuples, with each tuple describing a
36431 single source file with the same fields as described previously. The
36432 @var{sources} list can be empty for object files that have no debug
36435 @subsubheading @value{GDBN} Command
36437 The @value{GDBN} equivalent is @samp{info sources}.
36438 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36440 @subsubheading Example
36443 -file-list-exec-source-files
36444 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36445 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36446 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36448 -file-list-exec-source-files
36449 ^done,files=[@{file="test.c",
36450 fullname="/tmp/info-sources/test.c",
36451 debug-fully-read="true"@},
36452 @{file="/usr/include/stdc-predef.h",
36453 fullname="/usr/include/stdc-predef.h",
36454 debug-fully-read="true"@},
36456 fullname="/tmp/info-sources/header.h",
36457 debug-fully-read="true"@},
36459 fullname="/tmp/info-sources/helper.c",
36460 debug-fully-read="true"@}]
36462 -file-list-exec-source-files -- \\.c
36463 ^done,files=[@{file="test.c",
36464 fullname="/tmp/info-sources/test.c",
36465 debug-fully-read="true"@},
36467 fullname="/tmp/info-sources/helper.c",
36468 debug-fully-read="true"@}]
36470 -file-list-exec-source-files --group-by-objfile
36471 ^done,files=[@{filename="/tmp/info-sources/test.x",
36472 debug-info="fully-read",
36473 sources=[@{file="test.c",
36474 fullname="/tmp/info-sources/test.c",
36475 debug-fully-read="true"@},
36476 @{file="/usr/include/stdc-predef.h",
36477 fullname="/usr/include/stdc-predef.h",
36478 debug-fully-read="true"@},
36480 fullname="/tmp/info-sources/header.h",
36481 debug-fully-read="true"@}]@},
36482 @{filename="/lib64/ld-linux-x86-64.so.2",
36485 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36488 @{filename="/tmp/info-sources/libhelper.so",
36489 debug-info="fully-read",
36490 sources=[@{file="helper.c",
36491 fullname="/tmp/info-sources/helper.c",
36492 debug-fully-read="true"@},
36493 @{file="/usr/include/stdc-predef.h",
36494 fullname="/usr/include/stdc-predef.h",
36495 debug-fully-read="true"@},
36497 fullname="/tmp/info-sources/header.h",
36498 debug-fully-read="true"@}]@},
36499 @{filename="/lib64/libc.so.6",
36504 @subheading The @code{-file-list-shared-libraries} Command
36505 @findex -file-list-shared-libraries
36507 @subsubheading Synopsis
36510 -file-list-shared-libraries [ @var{regexp} ]
36513 List the shared libraries in the program.
36514 With a regular expression @var{regexp}, only those libraries whose
36515 names match @var{regexp} are listed.
36517 @subsubheading @value{GDBN} Command
36519 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36520 have a similar meaning to the @code{=library-loaded} notification.
36521 The @code{ranges} field specifies the multiple segments belonging to this
36522 library. Each range has the following fields:
36526 The address defining the inclusive lower bound of the segment.
36528 The address defining the exclusive upper bound of the segment.
36531 @subsubheading Example
36534 -file-list-exec-source-files
36535 ^done,shared-libraries=[
36536 @{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"@}]@},
36537 @{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"@}]@}]
36543 @subheading The @code{-file-list-symbol-files} Command
36544 @findex -file-list-symbol-files
36546 @subsubheading Synopsis
36549 -file-list-symbol-files
36554 @subsubheading @value{GDBN} Command
36556 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36558 @subsubheading Example
36563 @subheading The @code{-file-symbol-file} Command
36564 @findex -file-symbol-file
36566 @subsubheading Synopsis
36569 -file-symbol-file @var{file}
36572 Read symbol table info from the specified @var{file} argument. When
36573 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36574 produced, except for a completion notification.
36576 @subsubheading @value{GDBN} Command
36578 The corresponding @value{GDBN} command is @samp{symbol-file}.
36580 @subsubheading Example
36584 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36590 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36591 @node GDB/MI Memory Overlay Commands
36592 @section @sc{gdb/mi} Memory Overlay Commands
36594 The memory overlay commands are not implemented.
36596 @c @subheading -overlay-auto
36598 @c @subheading -overlay-list-mapping-state
36600 @c @subheading -overlay-list-overlays
36602 @c @subheading -overlay-map
36604 @c @subheading -overlay-off
36606 @c @subheading -overlay-on
36608 @c @subheading -overlay-unmap
36610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36611 @node GDB/MI Signal Handling Commands
36612 @section @sc{gdb/mi} Signal Handling Commands
36614 Signal handling commands are not implemented.
36616 @c @subheading -signal-handle
36618 @c @subheading -signal-list-handle-actions
36620 @c @subheading -signal-list-signal-types
36624 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36625 @node GDB/MI Target Manipulation
36626 @section @sc{gdb/mi} Target Manipulation Commands
36629 @subheading The @code{-target-attach} Command
36630 @findex -target-attach
36632 @subsubheading Synopsis
36635 -target-attach @var{pid} | @var{gid} | @var{file}
36638 Attach to a process @var{pid} or a file @var{file} outside of
36639 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36640 group, the id previously returned by
36641 @samp{-list-thread-groups --available} must be used.
36643 @subsubheading @value{GDBN} Command
36645 The corresponding @value{GDBN} command is @samp{attach}.
36647 @subsubheading Example
36651 =thread-created,id="1"
36652 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36658 @subheading The @code{-target-compare-sections} Command
36659 @findex -target-compare-sections
36661 @subsubheading Synopsis
36664 -target-compare-sections [ @var{section} ]
36667 Compare data of section @var{section} on target to the exec file.
36668 Without the argument, all sections are compared.
36670 @subsubheading @value{GDBN} Command
36672 The @value{GDBN} equivalent is @samp{compare-sections}.
36674 @subsubheading Example
36679 @subheading The @code{-target-detach} Command
36680 @findex -target-detach
36682 @subsubheading Synopsis
36685 -target-detach [ @var{pid} | @var{gid} ]
36688 Detach from the remote target which normally resumes its execution.
36689 If either @var{pid} or @var{gid} is specified, detaches from either
36690 the specified process, or specified thread group. There's no output.
36692 @subsubheading @value{GDBN} Command
36694 The corresponding @value{GDBN} command is @samp{detach}.
36696 @subsubheading Example
36706 @subheading The @code{-target-disconnect} Command
36707 @findex -target-disconnect
36709 @subsubheading Synopsis
36715 Disconnect from the remote target. There's no output and the target is
36716 generally not resumed.
36718 @subsubheading @value{GDBN} Command
36720 The corresponding @value{GDBN} command is @samp{disconnect}.
36722 @subsubheading Example
36732 @subheading The @code{-target-download} Command
36733 @findex -target-download
36735 @subsubheading Synopsis
36741 Loads the executable onto the remote target.
36742 It prints out an update message every half second, which includes the fields:
36746 The name of the section.
36748 The size of what has been sent so far for that section.
36750 The size of the section.
36752 The total size of what was sent so far (the current and the previous sections).
36754 The size of the overall executable to download.
36758 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36759 @sc{gdb/mi} Output Syntax}).
36761 In addition, it prints the name and size of the sections, as they are
36762 downloaded. These messages include the following fields:
36766 The name of the section.
36768 The size of the section.
36770 The size of the overall executable to download.
36774 At the end, a summary is printed.
36776 @subsubheading @value{GDBN} Command
36778 The corresponding @value{GDBN} command is @samp{load}.
36780 @subsubheading Example
36782 Note: each status message appears on a single line. Here the messages
36783 have been broken down so that they can fit onto a page.
36788 +download,@{section=".text",section-size="6668",total-size="9880"@}
36789 +download,@{section=".text",section-sent="512",section-size="6668",
36790 total-sent="512",total-size="9880"@}
36791 +download,@{section=".text",section-sent="1024",section-size="6668",
36792 total-sent="1024",total-size="9880"@}
36793 +download,@{section=".text",section-sent="1536",section-size="6668",
36794 total-sent="1536",total-size="9880"@}
36795 +download,@{section=".text",section-sent="2048",section-size="6668",
36796 total-sent="2048",total-size="9880"@}
36797 +download,@{section=".text",section-sent="2560",section-size="6668",
36798 total-sent="2560",total-size="9880"@}
36799 +download,@{section=".text",section-sent="3072",section-size="6668",
36800 total-sent="3072",total-size="9880"@}
36801 +download,@{section=".text",section-sent="3584",section-size="6668",
36802 total-sent="3584",total-size="9880"@}
36803 +download,@{section=".text",section-sent="4096",section-size="6668",
36804 total-sent="4096",total-size="9880"@}
36805 +download,@{section=".text",section-sent="4608",section-size="6668",
36806 total-sent="4608",total-size="9880"@}
36807 +download,@{section=".text",section-sent="5120",section-size="6668",
36808 total-sent="5120",total-size="9880"@}
36809 +download,@{section=".text",section-sent="5632",section-size="6668",
36810 total-sent="5632",total-size="9880"@}
36811 +download,@{section=".text",section-sent="6144",section-size="6668",
36812 total-sent="6144",total-size="9880"@}
36813 +download,@{section=".text",section-sent="6656",section-size="6668",
36814 total-sent="6656",total-size="9880"@}
36815 +download,@{section=".init",section-size="28",total-size="9880"@}
36816 +download,@{section=".fini",section-size="28",total-size="9880"@}
36817 +download,@{section=".data",section-size="3156",total-size="9880"@}
36818 +download,@{section=".data",section-sent="512",section-size="3156",
36819 total-sent="7236",total-size="9880"@}
36820 +download,@{section=".data",section-sent="1024",section-size="3156",
36821 total-sent="7748",total-size="9880"@}
36822 +download,@{section=".data",section-sent="1536",section-size="3156",
36823 total-sent="8260",total-size="9880"@}
36824 +download,@{section=".data",section-sent="2048",section-size="3156",
36825 total-sent="8772",total-size="9880"@}
36826 +download,@{section=".data",section-sent="2560",section-size="3156",
36827 total-sent="9284",total-size="9880"@}
36828 +download,@{section=".data",section-sent="3072",section-size="3156",
36829 total-sent="9796",total-size="9880"@}
36830 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36837 @subheading The @code{-target-exec-status} Command
36838 @findex -target-exec-status
36840 @subsubheading Synopsis
36843 -target-exec-status
36846 Provide information on the state of the target (whether it is running or
36847 not, for instance).
36849 @subsubheading @value{GDBN} Command
36851 There's no equivalent @value{GDBN} command.
36853 @subsubheading Example
36857 @subheading The @code{-target-list-available-targets} Command
36858 @findex -target-list-available-targets
36860 @subsubheading Synopsis
36863 -target-list-available-targets
36866 List the possible targets to connect to.
36868 @subsubheading @value{GDBN} Command
36870 The corresponding @value{GDBN} command is @samp{help target}.
36872 @subsubheading Example
36876 @subheading The @code{-target-list-current-targets} Command
36877 @findex -target-list-current-targets
36879 @subsubheading Synopsis
36882 -target-list-current-targets
36885 Describe the current target.
36887 @subsubheading @value{GDBN} Command
36889 The corresponding information is printed by @samp{info file} (among
36892 @subsubheading Example
36896 @subheading The @code{-target-list-parameters} Command
36897 @findex -target-list-parameters
36899 @subsubheading Synopsis
36902 -target-list-parameters
36908 @subsubheading @value{GDBN} Command
36912 @subsubheading Example
36915 @subheading The @code{-target-flash-erase} Command
36916 @findex -target-flash-erase
36918 @subsubheading Synopsis
36921 -target-flash-erase
36924 Erases all known flash memory regions on the target.
36926 The corresponding @value{GDBN} command is @samp{flash-erase}.
36928 The output is a list of flash regions that have been erased, with starting
36929 addresses and memory region sizes.
36933 -target-flash-erase
36934 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36938 @subheading The @code{-target-select} Command
36939 @findex -target-select
36941 @subsubheading Synopsis
36944 -target-select @var{type} @var{parameters @dots{}}
36947 Connect @value{GDBN} to the remote target. This command takes two args:
36951 The type of target, for instance @samp{remote}, etc.
36952 @item @var{parameters}
36953 Device names, host names and the like. @xref{Target Commands, ,
36954 Commands for Managing Targets}, for more details.
36957 The output is a connection notification, followed by the address at
36958 which the target program is, in the following form:
36961 ^connected,addr="@var{address}",func="@var{function name}",
36962 args=[@var{arg list}]
36965 @subsubheading @value{GDBN} Command
36967 The corresponding @value{GDBN} command is @samp{target}.
36969 @subsubheading Example
36973 -target-select remote /dev/ttya
36974 ^connected,addr="0xfe00a300",func="??",args=[]
36978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36979 @node GDB/MI File Transfer Commands
36980 @section @sc{gdb/mi} File Transfer Commands
36983 @subheading The @code{-target-file-put} Command
36984 @findex -target-file-put
36986 @subsubheading Synopsis
36989 -target-file-put @var{hostfile} @var{targetfile}
36992 Copy file @var{hostfile} from the host system (the machine running
36993 @value{GDBN}) to @var{targetfile} on the target system.
36995 @subsubheading @value{GDBN} Command
36997 The corresponding @value{GDBN} command is @samp{remote put}.
36999 @subsubheading Example
37003 -target-file-put localfile remotefile
37009 @subheading The @code{-target-file-get} Command
37010 @findex -target-file-get
37012 @subsubheading Synopsis
37015 -target-file-get @var{targetfile} @var{hostfile}
37018 Copy file @var{targetfile} from the target system to @var{hostfile}
37019 on the host system.
37021 @subsubheading @value{GDBN} Command
37023 The corresponding @value{GDBN} command is @samp{remote get}.
37025 @subsubheading Example
37029 -target-file-get remotefile localfile
37035 @subheading The @code{-target-file-delete} Command
37036 @findex -target-file-delete
37038 @subsubheading Synopsis
37041 -target-file-delete @var{targetfile}
37044 Delete @var{targetfile} from the target system.
37046 @subsubheading @value{GDBN} Command
37048 The corresponding @value{GDBN} command is @samp{remote delete}.
37050 @subsubheading Example
37054 -target-file-delete remotefile
37060 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37061 @node GDB/MI Ada Exceptions Commands
37062 @section Ada Exceptions @sc{gdb/mi} Commands
37064 @subheading The @code{-info-ada-exceptions} Command
37065 @findex -info-ada-exceptions
37067 @subsubheading Synopsis
37070 -info-ada-exceptions [ @var{regexp}]
37073 List all Ada exceptions defined within the program being debugged.
37074 With a regular expression @var{regexp}, only those exceptions whose
37075 names match @var{regexp} are listed.
37077 @subsubheading @value{GDBN} Command
37079 The corresponding @value{GDBN} command is @samp{info exceptions}.
37081 @subsubheading Result
37083 The result is a table of Ada exceptions. The following columns are
37084 defined for each exception:
37088 The name of the exception.
37091 The address of the exception.
37095 @subsubheading Example
37098 -info-ada-exceptions aint
37099 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
37100 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
37101 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
37102 body=[@{name="constraint_error",address="0x0000000000613da0"@},
37103 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
37106 @subheading Catching Ada Exceptions
37108 The commands describing how to ask @value{GDBN} to stop when a program
37109 raises an exception are described at @ref{Ada Exception GDB/MI
37110 Catchpoint Commands}.
37113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37114 @node GDB/MI Support Commands
37115 @section @sc{gdb/mi} Support Commands
37117 Since new commands and features get regularly added to @sc{gdb/mi},
37118 some commands are available to help front-ends query the debugger
37119 about support for these capabilities. Similarly, it is also possible
37120 to query @value{GDBN} about target support of certain features.
37122 @subheading The @code{-info-gdb-mi-command} Command
37123 @cindex @code{-info-gdb-mi-command}
37124 @findex -info-gdb-mi-command
37126 @subsubheading Synopsis
37129 -info-gdb-mi-command @var{cmd_name}
37132 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
37134 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
37135 is technically not part of the command name (@pxref{GDB/MI Input
37136 Syntax}), and thus should be omitted in @var{cmd_name}. However,
37137 for ease of use, this command also accepts the form with the leading
37140 @subsubheading @value{GDBN} Command
37142 There is no corresponding @value{GDBN} command.
37144 @subsubheading Result
37146 The result is a tuple. There is currently only one field:
37150 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
37151 @code{"false"} otherwise.
37155 @subsubheading Example
37157 Here is an example where the @sc{gdb/mi} command does not exist:
37160 -info-gdb-mi-command unsupported-command
37161 ^done,command=@{exists="false"@}
37165 And here is an example where the @sc{gdb/mi} command is known
37169 -info-gdb-mi-command symbol-list-lines
37170 ^done,command=@{exists="true"@}
37173 @subheading The @code{-list-features} Command
37174 @findex -list-features
37175 @cindex supported @sc{gdb/mi} features, list
37177 Returns a list of particular features of the MI protocol that
37178 this version of gdb implements. A feature can be a command,
37179 or a new field in an output of some command, or even an
37180 important bugfix. While a frontend can sometimes detect presence
37181 of a feature at runtime, it is easier to perform detection at debugger
37184 The command returns a list of strings, with each string naming an
37185 available feature. Each returned string is just a name, it does not
37186 have any internal structure. The list of possible feature names
37192 (gdb) -list-features
37193 ^done,result=["feature1","feature2"]
37196 The current list of features is:
37199 @item frozen-varobjs
37200 Indicates support for the @code{-var-set-frozen} command, as well
37201 as possible presence of the @code{frozen} field in the output
37202 of @code{-varobj-create}.
37203 @item pending-breakpoints
37204 Indicates support for the @option{-f} option to the @code{-break-insert}
37207 Indicates Python scripting support, Python-based
37208 pretty-printing commands, and possible presence of the
37209 @samp{display_hint} field in the output of @code{-var-list-children}
37211 Indicates support for the @code{-thread-info} command.
37212 @item data-read-memory-bytes
37213 Indicates support for the @code{-data-read-memory-bytes} and the
37214 @code{-data-write-memory-bytes} commands.
37215 @item breakpoint-notifications
37216 Indicates that changes to breakpoints and breakpoints created via the
37217 CLI will be announced via async records.
37218 @item ada-task-info
37219 Indicates support for the @code{-ada-task-info} command.
37220 @item language-option
37221 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
37222 option (@pxref{Context management}).
37223 @item info-gdb-mi-command
37224 Indicates support for the @code{-info-gdb-mi-command} command.
37225 @item undefined-command-error-code
37226 Indicates support for the "undefined-command" error code in error result
37227 records, produced when trying to execute an undefined @sc{gdb/mi} command
37228 (@pxref{GDB/MI Result Records}).
37229 @item exec-run-start-option
37230 Indicates that the @code{-exec-run} command supports the @option{--start}
37231 option (@pxref{GDB/MI Program Execution}).
37232 @item data-disassemble-a-option
37233 Indicates that the @code{-data-disassemble} command supports the @option{-a}
37234 option (@pxref{GDB/MI Data Manipulation}).
37237 @subheading The @code{-list-target-features} Command
37238 @findex -list-target-features
37240 Returns a list of particular features that are supported by the
37241 target. Those features affect the permitted MI commands, but
37242 unlike the features reported by the @code{-list-features} command, the
37243 features depend on which target GDB is using at the moment. Whenever
37244 a target can change, due to commands such as @code{-target-select},
37245 @code{-target-attach} or @code{-exec-run}, the list of target features
37246 may change, and the frontend should obtain it again.
37250 (gdb) -list-target-features
37251 ^done,result=["async"]
37254 The current list of features is:
37258 Indicates that the target is capable of asynchronous command
37259 execution, which means that @value{GDBN} will accept further commands
37260 while the target is running.
37263 Indicates that the target is capable of reverse execution.
37264 @xref{Reverse Execution}, for more information.
37268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37269 @node GDB/MI Miscellaneous Commands
37270 @section Miscellaneous @sc{gdb/mi} Commands
37272 @c @subheading -gdb-complete
37274 @subheading The @code{-gdb-exit} Command
37277 @subsubheading Synopsis
37283 Exit @value{GDBN} immediately.
37285 @subsubheading @value{GDBN} Command
37287 Approximately corresponds to @samp{quit}.
37289 @subsubheading Example
37299 @subheading The @code{-exec-abort} Command
37300 @findex -exec-abort
37302 @subsubheading Synopsis
37308 Kill the inferior running program.
37310 @subsubheading @value{GDBN} Command
37312 The corresponding @value{GDBN} command is @samp{kill}.
37314 @subsubheading Example
37319 @subheading The @code{-gdb-set} Command
37322 @subsubheading Synopsis
37328 Set an internal @value{GDBN} variable.
37329 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37331 @subsubheading @value{GDBN} Command
37333 The corresponding @value{GDBN} command is @samp{set}.
37335 @subsubheading Example
37345 @subheading The @code{-gdb-show} Command
37348 @subsubheading Synopsis
37354 Show the current value of a @value{GDBN} variable.
37356 @subsubheading @value{GDBN} Command
37358 The corresponding @value{GDBN} command is @samp{show}.
37360 @subsubheading Example
37369 @c @subheading -gdb-source
37372 @subheading The @code{-gdb-version} Command
37373 @findex -gdb-version
37375 @subsubheading Synopsis
37381 Show version information for @value{GDBN}. Used mostly in testing.
37383 @subsubheading @value{GDBN} Command
37385 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37386 default shows this information when you start an interactive session.
37388 @subsubheading Example
37390 @c This example modifies the actual output from GDB to avoid overfull
37396 ~Copyright 2000 Free Software Foundation, Inc.
37397 ~GDB is free software, covered by the GNU General Public License, and
37398 ~you are welcome to change it and/or distribute copies of it under
37399 ~ certain conditions.
37400 ~Type "show copying" to see the conditions.
37401 ~There is absolutely no warranty for GDB. Type "show warranty" for
37403 ~This GDB was configured as
37404 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37409 @subheading The @code{-list-thread-groups} Command
37410 @findex -list-thread-groups
37412 @subheading Synopsis
37415 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37418 Lists thread groups (@pxref{Thread groups}). When a single thread
37419 group is passed as the argument, lists the children of that group.
37420 When several thread group are passed, lists information about those
37421 thread groups. Without any parameters, lists information about all
37422 top-level thread groups.
37424 Normally, thread groups that are being debugged are reported.
37425 With the @samp{--available} option, @value{GDBN} reports thread groups
37426 available on the target.
37428 The output of this command may have either a @samp{threads} result or
37429 a @samp{groups} result. The @samp{thread} result has a list of tuples
37430 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37431 Information}). The @samp{groups} result has a list of tuples as value,
37432 each tuple describing a thread group. If top-level groups are
37433 requested (that is, no parameter is passed), or when several groups
37434 are passed, the output always has a @samp{groups} result. The format
37435 of the @samp{group} result is described below.
37437 To reduce the number of roundtrips it's possible to list thread groups
37438 together with their children, by passing the @samp{--recurse} option
37439 and the recursion depth. Presently, only recursion depth of 1 is
37440 permitted. If this option is present, then every reported thread group
37441 will also include its children, either as @samp{group} or
37442 @samp{threads} field.
37444 In general, any combination of option and parameters is permitted, with
37445 the following caveats:
37449 When a single thread group is passed, the output will typically
37450 be the @samp{threads} result. Because threads may not contain
37451 anything, the @samp{recurse} option will be ignored.
37454 When the @samp{--available} option is passed, limited information may
37455 be available. In particular, the list of threads of a process might
37456 be inaccessible. Further, specifying specific thread groups might
37457 not give any performance advantage over listing all thread groups.
37458 The frontend should assume that @samp{-list-thread-groups --available}
37459 is always an expensive operation and cache the results.
37463 The @samp{groups} result is a list of tuples, where each tuple may
37464 have the following fields:
37468 Identifier of the thread group. This field is always present.
37469 The identifier is an opaque string; frontends should not try to
37470 convert it to an integer, even though it might look like one.
37473 The type of the thread group. At present, only @samp{process} is a
37477 The target-specific process identifier. This field is only present
37478 for thread groups of type @samp{process} and only if the process exists.
37481 The exit code of this group's last exited thread, formatted in octal.
37482 This field is only present for thread groups of type @samp{process} and
37483 only if the process is not running.
37486 The number of children this thread group has. This field may be
37487 absent for an available thread group.
37490 This field has a list of tuples as value, each tuple describing a
37491 thread. It may be present if the @samp{--recurse} option is
37492 specified, and it's actually possible to obtain the threads.
37495 This field is a list of integers, each identifying a core that one
37496 thread of the group is running on. This field may be absent if
37497 such information is not available.
37500 The name of the executable file that corresponds to this thread group.
37501 The field is only present for thread groups of type @samp{process},
37502 and only if there is a corresponding executable file.
37506 @subheading Example
37510 -list-thread-groups
37511 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37512 -list-thread-groups 17
37513 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37514 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37515 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37516 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37517 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37518 -list-thread-groups --available
37519 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37520 -list-thread-groups --available --recurse 1
37521 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37522 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37523 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37524 -list-thread-groups --available --recurse 1 17 18
37525 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37526 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37527 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37530 @subheading The @code{-info-os} Command
37533 @subsubheading Synopsis
37536 -info-os [ @var{type} ]
37539 If no argument is supplied, the command returns a table of available
37540 operating-system-specific information types. If one of these types is
37541 supplied as an argument @var{type}, then the command returns a table
37542 of data of that type.
37544 The types of information available depend on the target operating
37547 @subsubheading @value{GDBN} Command
37549 The corresponding @value{GDBN} command is @samp{info os}.
37551 @subsubheading Example
37553 When run on a @sc{gnu}/Linux system, the output will look something
37559 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37560 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37561 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37562 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37563 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37565 item=@{col0="files",col1="Listing of all file descriptors",
37566 col2="File descriptors"@},
37567 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37568 col2="Kernel modules"@},
37569 item=@{col0="msg",col1="Listing of all message queues",
37570 col2="Message queues"@},
37571 item=@{col0="processes",col1="Listing of all processes",
37572 col2="Processes"@},
37573 item=@{col0="procgroups",col1="Listing of all process groups",
37574 col2="Process groups"@},
37575 item=@{col0="semaphores",col1="Listing of all semaphores",
37576 col2="Semaphores"@},
37577 item=@{col0="shm",col1="Listing of all shared-memory regions",
37578 col2="Shared-memory regions"@},
37579 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37581 item=@{col0="threads",col1="Listing of all threads",
37585 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37586 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37587 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37588 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37589 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37590 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37591 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37592 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37594 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37595 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37599 (Note that the MI output here includes a @code{"Title"} column that
37600 does not appear in command-line @code{info os}; this column is useful
37601 for MI clients that want to enumerate the types of data, such as in a
37602 popup menu, but is needless clutter on the command line, and
37603 @code{info os} omits it.)
37605 @subheading The @code{-add-inferior} Command
37606 @findex -add-inferior
37608 @subheading Synopsis
37611 -add-inferior [ --no-connection ]
37614 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37615 inferior is not associated with any executable. Such association may
37616 be established with the @samp{-file-exec-and-symbols} command
37617 (@pxref{GDB/MI File Commands}).
37619 By default, the new inferior begins connected to the same target
37620 connection as the current inferior. For example, if the current
37621 inferior was connected to @code{gdbserver} with @code{target remote},
37622 then the new inferior will be connected to the same @code{gdbserver}
37623 instance. The @samp{--no-connection} option starts the new inferior
37624 with no connection yet. You can then for example use the
37625 @code{-target-select remote} command to connect to some other
37626 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37629 The command response always has a field, @var{inferior}, whose value
37630 is the identifier of the thread group corresponding to the new
37633 An additional section field, @var{connection}, is optional. This
37634 field will only exist if the new inferior has a target connection. If
37635 this field exists, then its value will be a tuple containing the
37640 The number of the connection used for the new inferior.
37643 The name of the connection type used for the new inferior.
37646 @subheading @value{GDBN} Command
37648 The corresponding @value{GDBN} command is @samp{add-inferior}
37649 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37651 @subheading Example
37656 ^done,inferior="i3"
37659 @subheading The @code{-interpreter-exec} Command
37660 @findex -interpreter-exec
37662 @subheading Synopsis
37665 -interpreter-exec @var{interpreter} @var{command}
37667 @anchor{-interpreter-exec}
37669 Execute the specified @var{command} in the given @var{interpreter}.
37671 @subheading @value{GDBN} Command
37673 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37675 @subheading Example
37679 -interpreter-exec console "break main"
37680 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37681 &"During symbol reading, bad structure-type format.\n"
37682 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37687 @subheading The @code{-inferior-tty-set} Command
37688 @findex -inferior-tty-set
37690 @subheading Synopsis
37693 -inferior-tty-set /dev/pts/1
37696 Set terminal for future runs of the program being debugged.
37698 @subheading @value{GDBN} Command
37700 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37702 @subheading Example
37706 -inferior-tty-set /dev/pts/1
37711 @subheading The @code{-inferior-tty-show} Command
37712 @findex -inferior-tty-show
37714 @subheading Synopsis
37720 Show terminal for future runs of program being debugged.
37722 @subheading @value{GDBN} Command
37724 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37726 @subheading Example
37730 -inferior-tty-set /dev/pts/1
37734 ^done,inferior_tty_terminal="/dev/pts/1"
37738 @subheading The @code{-enable-timings} Command
37739 @findex -enable-timings
37741 @subheading Synopsis
37744 -enable-timings [yes | no]
37747 Toggle the printing of the wallclock, user and system times for an MI
37748 command as a field in its output. This command is to help frontend
37749 developers optimize the performance of their code. No argument is
37750 equivalent to @samp{yes}.
37752 @subheading @value{GDBN} Command
37756 @subheading Example
37764 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37765 addr="0x080484ed",func="main",file="myprog.c",
37766 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37768 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37776 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37777 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37778 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37779 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37783 @subheading The @code{-complete} Command
37786 @subheading Synopsis
37789 -complete @var{command}
37792 Show a list of completions for partially typed CLI @var{command}.
37794 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37795 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37796 because @value{GDBN} is used remotely via a SSH connection.
37800 The result consists of two or three fields:
37804 This field contains the completed @var{command}. If @var{command}
37805 has no known completions, this field is omitted.
37808 This field contains a (possibly empty) array of matches. It is always present.
37810 @item max_completions_reached
37811 This field contains @code{1} if number of known completions is above
37812 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37813 @code{0}. It is always present.
37817 @subheading @value{GDBN} Command
37819 The corresponding @value{GDBN} command is @samp{complete}.
37821 @subheading Example
37826 ^done,completion="break",
37827 matches=["break","break-range"],
37828 max_completions_reached="0"
37831 ^done,completion="b ma",
37832 matches=["b madvise","b main"],max_completions_reached="0"
37834 -complete "b push_b"
37835 ^done,completion="b push_back(",
37837 "b A::push_back(void*)",
37838 "b std::string::push_back(char)",
37839 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37840 max_completions_reached="0"
37842 -complete "nonexist"
37843 ^done,matches=[],max_completions_reached="0"
37849 @chapter @value{GDBN} Annotations
37851 This chapter describes annotations in @value{GDBN}. Annotations were
37852 designed to interface @value{GDBN} to graphical user interfaces or other
37853 similar programs which want to interact with @value{GDBN} at a
37854 relatively high level.
37856 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37860 This is Edition @value{EDITION}, @value{DATE}.
37864 * Annotations Overview:: What annotations are; the general syntax.
37865 * Server Prefix:: Issuing a command without affecting user state.
37866 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37867 * Errors:: Annotations for error messages.
37868 * Invalidation:: Some annotations describe things now invalid.
37869 * Annotations for Running::
37870 Whether the program is running, how it stopped, etc.
37871 * Source Annotations:: Annotations describing source code.
37874 @node Annotations Overview
37875 @section What is an Annotation?
37876 @cindex annotations
37878 Annotations start with a newline character, two @samp{control-z}
37879 characters, and the name of the annotation. If there is no additional
37880 information associated with this annotation, the name of the annotation
37881 is followed immediately by a newline. If there is additional
37882 information, the name of the annotation is followed by a space, the
37883 additional information, and a newline. The additional information
37884 cannot contain newline characters.
37886 Any output not beginning with a newline and two @samp{control-z}
37887 characters denotes literal output from @value{GDBN}. Currently there is
37888 no need for @value{GDBN} to output a newline followed by two
37889 @samp{control-z} characters, but if there was such a need, the
37890 annotations could be extended with an @samp{escape} annotation which
37891 means those three characters as output.
37893 The annotation @var{level}, which is specified using the
37894 @option{--annotate} command line option (@pxref{Mode Options}), controls
37895 how much information @value{GDBN} prints together with its prompt,
37896 values of expressions, source lines, and other types of output. Level 0
37897 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37898 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37899 for programs that control @value{GDBN}, and level 2 annotations have
37900 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37901 Interface, annotate, GDB's Obsolete Annotations}).
37904 @kindex set annotate
37905 @item set annotate @var{level}
37906 The @value{GDBN} command @code{set annotate} sets the level of
37907 annotations to the specified @var{level}.
37909 @item show annotate
37910 @kindex show annotate
37911 Show the current annotation level.
37914 This chapter describes level 3 annotations.
37916 A simple example of starting up @value{GDBN} with annotations is:
37919 $ @kbd{gdb --annotate=3}
37921 Copyright 2003 Free Software Foundation, Inc.
37922 GDB is free software, covered by the GNU General Public License,
37923 and you are welcome to change it and/or distribute copies of it
37924 under certain conditions.
37925 Type "show copying" to see the conditions.
37926 There is absolutely no warranty for GDB. Type "show warranty"
37928 This GDB was configured as "i386-pc-linux-gnu"
37939 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37940 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37941 denotes a @samp{control-z} character) are annotations; the rest is
37942 output from @value{GDBN}.
37944 @node Server Prefix
37945 @section The Server Prefix
37946 @cindex server prefix
37948 If you prefix a command with @samp{server } then it will not affect
37949 the command history, nor will it affect @value{GDBN}'s notion of which
37950 command to repeat if @key{RET} is pressed on a line by itself. This
37951 means that commands can be run behind a user's back by a front-end in
37952 a transparent manner.
37954 The @code{server } prefix does not affect the recording of values into
37955 the value history; to print a value without recording it into the
37956 value history, use the @code{output} command instead of the
37957 @code{print} command.
37959 Using this prefix also disables confirmation requests
37960 (@pxref{confirmation requests}).
37963 @section Annotation for @value{GDBN} Input
37965 @cindex annotations for prompts
37966 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37967 to know when to send output, when the output from a given command is
37970 Different kinds of input each have a different @dfn{input type}. Each
37971 input type has three annotations: a @code{pre-} annotation, which
37972 denotes the beginning of any prompt which is being output, a plain
37973 annotation, which denotes the end of the prompt, and then a @code{post-}
37974 annotation which denotes the end of any echo which may (or may not) be
37975 associated with the input. For example, the @code{prompt} input type
37976 features the following annotations:
37984 The input types are
37987 @findex pre-prompt annotation
37988 @findex prompt annotation
37989 @findex post-prompt annotation
37991 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37993 @findex pre-commands annotation
37994 @findex commands annotation
37995 @findex post-commands annotation
37997 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37998 command. The annotations are repeated for each command which is input.
38000 @findex pre-overload-choice annotation
38001 @findex overload-choice annotation
38002 @findex post-overload-choice annotation
38003 @item overload-choice
38004 When @value{GDBN} wants the user to select between various overloaded functions.
38006 @findex pre-query annotation
38007 @findex query annotation
38008 @findex post-query annotation
38010 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
38012 @findex pre-prompt-for-continue annotation
38013 @findex prompt-for-continue annotation
38014 @findex post-prompt-for-continue annotation
38015 @item prompt-for-continue
38016 When @value{GDBN} is asking the user to press return to continue. Note: Don't
38017 expect this to work well; instead use @code{set height 0} to disable
38018 prompting. This is because the counting of lines is buggy in the
38019 presence of annotations.
38024 @cindex annotations for errors, warnings and interrupts
38026 @findex quit annotation
38031 This annotation occurs right before @value{GDBN} responds to an interrupt.
38033 @findex error annotation
38038 This annotation occurs right before @value{GDBN} responds to an error.
38040 Quit and error annotations indicate that any annotations which @value{GDBN} was
38041 in the middle of may end abruptly. For example, if a
38042 @code{value-history-begin} annotation is followed by a @code{error}, one
38043 cannot expect to receive the matching @code{value-history-end}. One
38044 cannot expect not to receive it either, however; an error annotation
38045 does not necessarily mean that @value{GDBN} is immediately returning all the way
38048 @findex error-begin annotation
38049 A quit or error annotation may be preceded by
38055 Any output between that and the quit or error annotation is the error
38058 Warning messages are not yet annotated.
38059 @c If we want to change that, need to fix warning(), type_error(),
38060 @c range_error(), and possibly other places.
38063 @section Invalidation Notices
38065 @cindex annotations for invalidation messages
38066 The following annotations say that certain pieces of state may have
38070 @findex frames-invalid annotation
38071 @item ^Z^Zframes-invalid
38073 The frames (for example, output from the @code{backtrace} command) may
38076 @findex breakpoints-invalid annotation
38077 @item ^Z^Zbreakpoints-invalid
38079 The breakpoints may have changed. For example, the user just added or
38080 deleted a breakpoint.
38083 @node Annotations for Running
38084 @section Running the Program
38085 @cindex annotations for running programs
38087 @findex starting annotation
38088 @findex stopping annotation
38089 When the program starts executing due to a @value{GDBN} command such as
38090 @code{step} or @code{continue},
38096 is output. When the program stops,
38102 is output. Before the @code{stopped} annotation, a variety of
38103 annotations describe how the program stopped.
38106 @findex exited annotation
38107 @item ^Z^Zexited @var{exit-status}
38108 The program exited, and @var{exit-status} is the exit status (zero for
38109 successful exit, otherwise nonzero).
38111 @findex signalled annotation
38112 @findex signal-name annotation
38113 @findex signal-name-end annotation
38114 @findex signal-string annotation
38115 @findex signal-string-end annotation
38116 @item ^Z^Zsignalled
38117 The program exited with a signal. After the @code{^Z^Zsignalled}, the
38118 annotation continues:
38124 ^Z^Zsignal-name-end
38128 ^Z^Zsignal-string-end
38133 where @var{name} is the name of the signal, such as @code{SIGILL} or
38134 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
38135 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
38136 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
38137 user's benefit and have no particular format.
38139 @findex signal annotation
38141 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
38142 just saying that the program received the signal, not that it was
38143 terminated with it.
38145 @findex breakpoint annotation
38146 @item ^Z^Zbreakpoint @var{number}
38147 The program hit breakpoint number @var{number}.
38149 @findex watchpoint annotation
38150 @item ^Z^Zwatchpoint @var{number}
38151 The program hit watchpoint number @var{number}.
38154 @node Source Annotations
38155 @section Displaying Source
38156 @cindex annotations for source display
38158 @findex source annotation
38159 The following annotation is used instead of displaying source code:
38162 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
38165 where @var{filename} is an absolute file name indicating which source
38166 file, @var{line} is the line number within that file (where 1 is the
38167 first line in the file), @var{character} is the character position
38168 within the file (where 0 is the first character in the file) (for most
38169 debug formats this will necessarily point to the beginning of a line),
38170 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
38171 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
38172 @var{addr} is the address in the target program associated with the
38173 source which is being displayed. The @var{addr} is in the form @samp{0x}
38174 followed by one or more lowercase hex digits (note that this does not
38175 depend on the language).
38177 @node JIT Interface
38178 @chapter JIT Compilation Interface
38179 @cindex just-in-time compilation
38180 @cindex JIT compilation interface
38182 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
38183 interface. A JIT compiler is a program or library that generates native
38184 executable code at runtime and executes it, usually in order to achieve good
38185 performance while maintaining platform independence.
38187 Programs that use JIT compilation are normally difficult to debug because
38188 portions of their code are generated at runtime, instead of being loaded from
38189 object files, which is where @value{GDBN} normally finds the program's symbols
38190 and debug information. In order to debug programs that use JIT compilation,
38191 @value{GDBN} has an interface that allows the program to register in-memory
38192 symbol files with @value{GDBN} at runtime.
38194 If you are using @value{GDBN} to debug a program that uses this interface, then
38195 it should work transparently so long as you have not stripped the binary. If
38196 you are developing a JIT compiler, then the interface is documented in the rest
38197 of this chapter. At this time, the only known client of this interface is the
38200 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
38201 JIT compiler communicates with @value{GDBN} by writing data into a global
38202 variable and calling a function at a well-known symbol. When @value{GDBN}
38203 attaches, it reads a linked list of symbol files from the global variable to
38204 find existing code, and puts a breakpoint in the function so that it can find
38205 out about additional code.
38208 * Declarations:: Relevant C struct declarations
38209 * Registering Code:: Steps to register code
38210 * Unregistering Code:: Steps to unregister code
38211 * Custom Debug Info:: Emit debug information in a custom format
38215 @section JIT Declarations
38217 These are the relevant struct declarations that a C program should include to
38218 implement the interface:
38228 struct jit_code_entry
38230 struct jit_code_entry *next_entry;
38231 struct jit_code_entry *prev_entry;
38232 const char *symfile_addr;
38233 uint64_t symfile_size;
38236 struct jit_descriptor
38239 /* This type should be jit_actions_t, but we use uint32_t
38240 to be explicit about the bitwidth. */
38241 uint32_t action_flag;
38242 struct jit_code_entry *relevant_entry;
38243 struct jit_code_entry *first_entry;
38246 /* GDB puts a breakpoint in this function. */
38247 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
38249 /* Make sure to specify the version statically, because the
38250 debugger may check the version before we can set it. */
38251 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
38254 If the JIT is multi-threaded, then it is important that the JIT synchronize any
38255 modifications to this global data properly, which can easily be done by putting
38256 a global mutex around modifications to these structures.
38258 @node Registering Code
38259 @section Registering Code
38261 To register code with @value{GDBN}, the JIT should follow this protocol:
38265 Generate an object file in memory with symbols and other desired debug
38266 information. The file must include the virtual addresses of the sections.
38269 Create a code entry for the file, which gives the start and size of the symbol
38273 Add it to the linked list in the JIT descriptor.
38276 Point the relevant_entry field of the descriptor at the entry.
38279 Set @code{action_flag} to @code{JIT_REGISTER} and call
38280 @code{__jit_debug_register_code}.
38283 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
38284 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
38285 new code. However, the linked list must still be maintained in order to allow
38286 @value{GDBN} to attach to a running process and still find the symbol files.
38288 @node Unregistering Code
38289 @section Unregistering Code
38291 If code is freed, then the JIT should use the following protocol:
38295 Remove the code entry corresponding to the code from the linked list.
38298 Point the @code{relevant_entry} field of the descriptor at the code entry.
38301 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38302 @code{__jit_debug_register_code}.
38305 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38306 and the JIT will leak the memory used for the associated symbol files.
38308 @node Custom Debug Info
38309 @section Custom Debug Info
38310 @cindex custom JIT debug info
38311 @cindex JIT debug info reader
38313 Generating debug information in platform-native file formats (like ELF
38314 or COFF) may be an overkill for JIT compilers; especially if all the
38315 debug info is used for is displaying a meaningful backtrace. The
38316 issue can be resolved by having the JIT writers decide on a debug info
38317 format and also provide a reader that parses the debug info generated
38318 by the JIT compiler. This section gives a brief overview on writing
38319 such a parser. More specific details can be found in the source file
38320 @file{gdb/jit-reader.in}, which is also installed as a header at
38321 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38323 The reader is implemented as a shared object (so this functionality is
38324 not available on platforms which don't allow loading shared objects at
38325 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38326 @code{jit-reader-unload} are provided, to be used to load and unload
38327 the readers from a preconfigured directory. Once loaded, the shared
38328 object is used the parse the debug information emitted by the JIT
38332 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38333 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38336 @node Using JIT Debug Info Readers
38337 @subsection Using JIT Debug Info Readers
38338 @kindex jit-reader-load
38339 @kindex jit-reader-unload
38341 Readers can be loaded and unloaded using the @code{jit-reader-load}
38342 and @code{jit-reader-unload} commands.
38345 @item jit-reader-load @var{reader}
38346 Load the JIT reader named @var{reader}, which is a shared
38347 object specified as either an absolute or a relative file name. In
38348 the latter case, @value{GDBN} will try to load the reader from a
38349 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38350 system (here @var{libdir} is the system library directory, often
38351 @file{/usr/local/lib}).
38353 Only one reader can be active at a time; trying to load a second
38354 reader when one is already loaded will result in @value{GDBN}
38355 reporting an error. A new JIT reader can be loaded by first unloading
38356 the current one using @code{jit-reader-unload} and then invoking
38357 @code{jit-reader-load}.
38359 @item jit-reader-unload
38360 Unload the currently loaded JIT reader.
38364 @node Writing JIT Debug Info Readers
38365 @subsection Writing JIT Debug Info Readers
38366 @cindex writing JIT debug info readers
38368 As mentioned, a reader is essentially a shared object conforming to a
38369 certain ABI. This ABI is described in @file{jit-reader.h}.
38371 @file{jit-reader.h} defines the structures, macros and functions
38372 required to write a reader. It is installed (along with
38373 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38374 the system include directory.
38376 Readers need to be released under a GPL compatible license. A reader
38377 can be declared as released under such a license by placing the macro
38378 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38380 The entry point for readers is the symbol @code{gdb_init_reader},
38381 which is expected to be a function with the prototype
38383 @findex gdb_init_reader
38385 extern struct gdb_reader_funcs *gdb_init_reader (void);
38388 @cindex @code{struct gdb_reader_funcs}
38390 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38391 functions. These functions are executed to read the debug info
38392 generated by the JIT compiler (@code{read}), to unwind stack frames
38393 (@code{unwind}) and to create canonical frame IDs
38394 (@code{get_frame_id}). It also has a callback that is called when the
38395 reader is being unloaded (@code{destroy}). The struct looks like this
38398 struct gdb_reader_funcs
38400 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38401 int reader_version;
38403 /* For use by the reader. */
38406 gdb_read_debug_info *read;
38407 gdb_unwind_frame *unwind;
38408 gdb_get_frame_id *get_frame_id;
38409 gdb_destroy_reader *destroy;
38413 @cindex @code{struct gdb_symbol_callbacks}
38414 @cindex @code{struct gdb_unwind_callbacks}
38416 The callbacks are provided with another set of callbacks by
38417 @value{GDBN} to do their job. For @code{read}, these callbacks are
38418 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38419 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38420 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38421 files and new symbol tables inside those object files. @code{struct
38422 gdb_unwind_callbacks} has callbacks to read registers off the current
38423 frame and to write out the values of the registers in the previous
38424 frame. Both have a callback (@code{target_read}) to read bytes off the
38425 target's address space.
38427 @node In-Process Agent
38428 @chapter In-Process Agent
38429 @cindex debugging agent
38430 The traditional debugging model is conceptually low-speed, but works fine,
38431 because most bugs can be reproduced in debugging-mode execution. However,
38432 as multi-core or many-core processors are becoming mainstream, and
38433 multi-threaded programs become more and more popular, there should be more
38434 and more bugs that only manifest themselves at normal-mode execution, for
38435 example, thread races, because debugger's interference with the program's
38436 timing may conceal the bugs. On the other hand, in some applications,
38437 it is not feasible for the debugger to interrupt the program's execution
38438 long enough for the developer to learn anything helpful about its behavior.
38439 If the program's correctness depends on its real-time behavior, delays
38440 introduced by a debugger might cause the program to fail, even when the
38441 code itself is correct. It is useful to be able to observe the program's
38442 behavior without interrupting it.
38444 Therefore, traditional debugging model is too intrusive to reproduce
38445 some bugs. In order to reduce the interference with the program, we can
38446 reduce the number of operations performed by debugger. The
38447 @dfn{In-Process Agent}, a shared library, is running within the same
38448 process with inferior, and is able to perform some debugging operations
38449 itself. As a result, debugger is only involved when necessary, and
38450 performance of debugging can be improved accordingly. Note that
38451 interference with program can be reduced but can't be removed completely,
38452 because the in-process agent will still stop or slow down the program.
38454 The in-process agent can interpret and execute Agent Expressions
38455 (@pxref{Agent Expressions}) during performing debugging operations. The
38456 agent expressions can be used for different purposes, such as collecting
38457 data in tracepoints, and condition evaluation in breakpoints.
38459 @anchor{Control Agent}
38460 You can control whether the in-process agent is used as an aid for
38461 debugging with the following commands:
38464 @kindex set agent on
38466 Causes the in-process agent to perform some operations on behalf of the
38467 debugger. Just which operations requested by the user will be done
38468 by the in-process agent depends on the its capabilities. For example,
38469 if you request to evaluate breakpoint conditions in the in-process agent,
38470 and the in-process agent has such capability as well, then breakpoint
38471 conditions will be evaluated in the in-process agent.
38473 @kindex set agent off
38474 @item set agent off
38475 Disables execution of debugging operations by the in-process agent. All
38476 of the operations will be performed by @value{GDBN}.
38480 Display the current setting of execution of debugging operations by
38481 the in-process agent.
38485 * In-Process Agent Protocol::
38488 @node In-Process Agent Protocol
38489 @section In-Process Agent Protocol
38490 @cindex in-process agent protocol
38492 The in-process agent is able to communicate with both @value{GDBN} and
38493 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38494 used for communications between @value{GDBN} or GDBserver and the IPA.
38495 In general, @value{GDBN} or GDBserver sends commands
38496 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38497 in-process agent replies back with the return result of the command, or
38498 some other information. The data sent to in-process agent is composed
38499 of primitive data types, such as 4-byte or 8-byte type, and composite
38500 types, which are called objects (@pxref{IPA Protocol Objects}).
38503 * IPA Protocol Objects::
38504 * IPA Protocol Commands::
38507 @node IPA Protocol Objects
38508 @subsection IPA Protocol Objects
38509 @cindex ipa protocol objects
38511 The commands sent to and results received from agent may contain some
38512 complex data types called @dfn{objects}.
38514 The in-process agent is running on the same machine with @value{GDBN}
38515 or GDBserver, so it doesn't have to handle as much differences between
38516 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38517 However, there are still some differences of two ends in two processes:
38521 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38522 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38524 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38525 GDBserver is compiled with one, and in-process agent is compiled with
38529 Here are the IPA Protocol Objects:
38533 agent expression object. It represents an agent expression
38534 (@pxref{Agent Expressions}).
38535 @anchor{agent expression object}
38537 tracepoint action object. It represents a tracepoint action
38538 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38539 memory, static trace data and to evaluate expression.
38540 @anchor{tracepoint action object}
38542 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38543 @anchor{tracepoint object}
38547 The following table describes important attributes of each IPA protocol
38550 @multitable @columnfractions .30 .20 .50
38551 @headitem Name @tab Size @tab Description
38552 @item @emph{agent expression object} @tab @tab
38553 @item length @tab 4 @tab length of bytes code
38554 @item byte code @tab @var{length} @tab contents of byte code
38555 @item @emph{tracepoint action for collecting memory} @tab @tab
38556 @item 'M' @tab 1 @tab type of tracepoint action
38557 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38558 address of the lowest byte to collect, otherwise @var{addr} is the offset
38559 of @var{basereg} for memory collecting.
38560 @item len @tab 8 @tab length of memory for collecting
38561 @item basereg @tab 4 @tab the register number containing the starting
38562 memory address for collecting.
38563 @item @emph{tracepoint action for collecting registers} @tab @tab
38564 @item 'R' @tab 1 @tab type of tracepoint action
38565 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38566 @item 'L' @tab 1 @tab type of tracepoint action
38567 @item @emph{tracepoint action for expression evaluation} @tab @tab
38568 @item 'X' @tab 1 @tab type of tracepoint action
38569 @item agent expression @tab length of @tab @ref{agent expression object}
38570 @item @emph{tracepoint object} @tab @tab
38571 @item number @tab 4 @tab number of tracepoint
38572 @item address @tab 8 @tab address of tracepoint inserted on
38573 @item type @tab 4 @tab type of tracepoint
38574 @item enabled @tab 1 @tab enable or disable of tracepoint
38575 @item step_count @tab 8 @tab step
38576 @item pass_count @tab 8 @tab pass
38577 @item numactions @tab 4 @tab number of tracepoint actions
38578 @item hit count @tab 8 @tab hit count
38579 @item trace frame usage @tab 8 @tab trace frame usage
38580 @item compiled_cond @tab 8 @tab compiled condition
38581 @item orig_size @tab 8 @tab orig size
38582 @item condition @tab 4 if condition is NULL otherwise length of
38583 @ref{agent expression object}
38584 @tab zero if condition is NULL, otherwise is
38585 @ref{agent expression object}
38586 @item actions @tab variable
38587 @tab numactions number of @ref{tracepoint action object}
38590 @node IPA Protocol Commands
38591 @subsection IPA Protocol Commands
38592 @cindex ipa protocol commands
38594 The spaces in each command are delimiters to ease reading this commands
38595 specification. They don't exist in real commands.
38599 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38600 Installs a new fast tracepoint described by @var{tracepoint_object}
38601 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38602 head of @dfn{jumppad}, which is used to jump to data collection routine
38607 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38608 @var{target_address} is address of tracepoint in the inferior.
38609 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38610 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38611 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38612 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38619 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38620 is about to kill inferiors.
38628 @item probe_marker_at:@var{address}
38629 Asks in-process agent to probe the marker at @var{address}.
38636 @item unprobe_marker_at:@var{address}
38637 Asks in-process agent to unprobe the marker at @var{address}.
38641 @chapter Reporting Bugs in @value{GDBN}
38642 @cindex bugs in @value{GDBN}
38643 @cindex reporting bugs in @value{GDBN}
38645 Your bug reports play an essential role in making @value{GDBN} reliable.
38647 Reporting a bug may help you by bringing a solution to your problem, or it
38648 may not. But in any case the principal function of a bug report is to help
38649 the entire community by making the next version of @value{GDBN} work better. Bug
38650 reports are your contribution to the maintenance of @value{GDBN}.
38652 In order for a bug report to serve its purpose, you must include the
38653 information that enables us to fix the bug.
38656 * Bug Criteria:: Have you found a bug?
38657 * Bug Reporting:: How to report bugs
38661 @section Have You Found a Bug?
38662 @cindex bug criteria
38664 If you are not sure whether you have found a bug, here are some guidelines:
38667 @cindex fatal signal
38668 @cindex debugger crash
38669 @cindex crash of debugger
38671 If the debugger gets a fatal signal, for any input whatever, that is a
38672 @value{GDBN} bug. Reliable debuggers never crash.
38674 @cindex error on valid input
38676 If @value{GDBN} produces an error message for valid input, that is a
38677 bug. (Note that if you're cross debugging, the problem may also be
38678 somewhere in the connection to the target.)
38680 @cindex invalid input
38682 If @value{GDBN} does not produce an error message for invalid input,
38683 that is a bug. However, you should note that your idea of
38684 ``invalid input'' might be our idea of ``an extension'' or ``support
38685 for traditional practice''.
38688 If you are an experienced user of debugging tools, your suggestions
38689 for improvement of @value{GDBN} are welcome in any case.
38692 @node Bug Reporting
38693 @section How to Report Bugs
38694 @cindex bug reports
38695 @cindex @value{GDBN} bugs, reporting
38697 A number of companies and individuals offer support for @sc{gnu} products.
38698 If you obtained @value{GDBN} from a support organization, we recommend you
38699 contact that organization first.
38701 You can find contact information for many support companies and
38702 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38704 @c should add a web page ref...
38707 @ifset BUGURL_DEFAULT
38708 In any event, we also recommend that you submit bug reports for
38709 @value{GDBN}. The preferred method is to submit them directly using
38710 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38711 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38714 @strong{Do not send bug reports to @samp{info-gdb}, or to
38715 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38716 not want to receive bug reports. Those that do have arranged to receive
38719 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38720 serves as a repeater. The mailing list and the newsgroup carry exactly
38721 the same messages. Often people think of posting bug reports to the
38722 newsgroup instead of mailing them. This appears to work, but it has one
38723 problem which can be crucial: a newsgroup posting often lacks a mail
38724 path back to the sender. Thus, if we need to ask for more information,
38725 we may be unable to reach you. For this reason, it is better to send
38726 bug reports to the mailing list.
38728 @ifclear BUGURL_DEFAULT
38729 In any event, we also recommend that you submit bug reports for
38730 @value{GDBN} to @value{BUGURL}.
38734 The fundamental principle of reporting bugs usefully is this:
38735 @strong{report all the facts}. If you are not sure whether to state a
38736 fact or leave it out, state it!
38738 Often people omit facts because they think they know what causes the
38739 problem and assume that some details do not matter. Thus, you might
38740 assume that the name of the variable you use in an example does not matter.
38741 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38742 stray memory reference which happens to fetch from the location where that
38743 name is stored in memory; perhaps, if the name were different, the contents
38744 of that location would fool the debugger into doing the right thing despite
38745 the bug. Play it safe and give a specific, complete example. That is the
38746 easiest thing for you to do, and the most helpful.
38748 Keep in mind that the purpose of a bug report is to enable us to fix the
38749 bug. It may be that the bug has been reported previously, but neither
38750 you nor we can know that unless your bug report is complete and
38753 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38754 bell?'' Those bug reports are useless, and we urge everyone to
38755 @emph{refuse to respond to them} except to chide the sender to report
38758 To enable us to fix the bug, you should include all these things:
38762 The version of @value{GDBN}. @value{GDBN} announces it if you start
38763 with no arguments; you can also print it at any time using @code{show
38766 Without this, we will not know whether there is any point in looking for
38767 the bug in the current version of @value{GDBN}.
38770 The type of machine you are using, and the operating system name and
38774 The details of the @value{GDBN} build-time configuration.
38775 @value{GDBN} shows these details if you invoke it with the
38776 @option{--configuration} command-line option, or if you type
38777 @code{show configuration} at @value{GDBN}'s prompt.
38780 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38781 ``@value{GCC}--2.8.1''.
38784 What compiler (and its version) was used to compile the program you are
38785 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38786 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38787 to get this information; for other compilers, see the documentation for
38791 The command arguments you gave the compiler to compile your example and
38792 observe the bug. For example, did you use @samp{-O}? To guarantee
38793 you will not omit something important, list them all. A copy of the
38794 Makefile (or the output from make) is sufficient.
38796 If we were to try to guess the arguments, we would probably guess wrong
38797 and then we might not encounter the bug.
38800 A complete input script, and all necessary source files, that will
38804 A description of what behavior you observe that you believe is
38805 incorrect. For example, ``It gets a fatal signal.''
38807 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38808 will certainly notice it. But if the bug is incorrect output, we might
38809 not notice unless it is glaringly wrong. You might as well not give us
38810 a chance to make a mistake.
38812 Even if the problem you experience is a fatal signal, you should still
38813 say so explicitly. Suppose something strange is going on, such as, your
38814 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38815 the C library on your system. (This has happened!) Your copy might
38816 crash and ours would not. If you told us to expect a crash, then when
38817 ours fails to crash, we would know that the bug was not happening for
38818 us. If you had not told us to expect a crash, then we would not be able
38819 to draw any conclusion from our observations.
38822 @cindex recording a session script
38823 To collect all this information, you can use a session recording program
38824 such as @command{script}, which is available on many Unix systems.
38825 Just run your @value{GDBN} session inside @command{script} and then
38826 include the @file{typescript} file with your bug report.
38828 Another way to record a @value{GDBN} session is to run @value{GDBN}
38829 inside Emacs and then save the entire buffer to a file.
38832 If you wish to suggest changes to the @value{GDBN} source, send us context
38833 diffs. If you even discuss something in the @value{GDBN} source, refer to
38834 it by context, not by line number.
38836 The line numbers in our development sources will not match those in your
38837 sources. Your line numbers would convey no useful information to us.
38841 Here are some things that are not necessary:
38845 A description of the envelope of the bug.
38847 Often people who encounter a bug spend a lot of time investigating
38848 which changes to the input file will make the bug go away and which
38849 changes will not affect it.
38851 This is often time consuming and not very useful, because the way we
38852 will find the bug is by running a single example under the debugger
38853 with breakpoints, not by pure deduction from a series of examples.
38854 We recommend that you save your time for something else.
38856 Of course, if you can find a simpler example to report @emph{instead}
38857 of the original one, that is a convenience for us. Errors in the
38858 output will be easier to spot, running under the debugger will take
38859 less time, and so on.
38861 However, simplification is not vital; if you do not want to do this,
38862 report the bug anyway and send us the entire test case you used.
38865 A patch for the bug.
38867 A patch for the bug does help us if it is a good one. But do not omit
38868 the necessary information, such as the test case, on the assumption that
38869 a patch is all we need. We might see problems with your patch and decide
38870 to fix the problem another way, or we might not understand it at all.
38872 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38873 construct an example that will make the program follow a certain path
38874 through the code. If you do not send us the example, we will not be able
38875 to construct one, so we will not be able to verify that the bug is fixed.
38877 And if we cannot understand what bug you are trying to fix, or why your
38878 patch should be an improvement, we will not install it. A test case will
38879 help us to understand.
38882 A guess about what the bug is or what it depends on.
38884 Such guesses are usually wrong. Even we cannot guess right about such
38885 things without first using the debugger to find the facts.
38888 @c The readline documentation is distributed with the readline code
38889 @c and consists of the two following files:
38892 @c Use -I with makeinfo to point to the appropriate directory,
38893 @c environment var TEXINPUTS with TeX.
38894 @ifclear SYSTEM_READLINE
38895 @include rluser.texi
38896 @include hsuser.texi
38900 @appendix In Memoriam
38902 The @value{GDBN} project mourns the loss of the following long-time
38907 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38908 to Free Software in general. Outside of @value{GDBN}, he was known in
38909 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38911 @item Michael Snyder
38912 Michael was one of the Global Maintainers of the @value{GDBN} project,
38913 with contributions recorded as early as 1996, until 2011. In addition
38914 to his day to day participation, he was a large driving force behind
38915 adding Reverse Debugging to @value{GDBN}.
38918 Beyond their technical contributions to the project, they were also
38919 enjoyable members of the Free Software Community. We will miss them.
38921 @node Formatting Documentation
38922 @appendix Formatting Documentation
38924 @cindex @value{GDBN} reference card
38925 @cindex reference card
38926 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38927 for printing with PostScript or Ghostscript, in the @file{gdb}
38928 subdirectory of the main source directory@footnote{In
38929 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38930 release.}. If you can use PostScript or Ghostscript with your printer,
38931 you can print the reference card immediately with @file{refcard.ps}.
38933 The release also includes the source for the reference card. You
38934 can format it, using @TeX{}, by typing:
38940 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38941 mode on US ``letter'' size paper;
38942 that is, on a sheet 11 inches wide by 8.5 inches
38943 high. You will need to specify this form of printing as an option to
38944 your @sc{dvi} output program.
38946 @cindex documentation
38948 All the documentation for @value{GDBN} comes as part of the machine-readable
38949 distribution. The documentation is written in Texinfo format, which is
38950 a documentation system that uses a single source file to produce both
38951 on-line information and a printed manual. You can use one of the Info
38952 formatting commands to create the on-line version of the documentation
38953 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38955 @value{GDBN} includes an already formatted copy of the on-line Info
38956 version of this manual in the @file{gdb} subdirectory. The main Info
38957 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38958 subordinate files matching @samp{gdb.info*} in the same directory. If
38959 necessary, you can print out these files, or read them with any editor;
38960 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38961 Emacs or the standalone @code{info} program, available as part of the
38962 @sc{gnu} Texinfo distribution.
38964 If you want to format these Info files yourself, you need one of the
38965 Info formatting programs, such as @code{texinfo-format-buffer} or
38968 If you have @code{makeinfo} installed, and are in the top level
38969 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38970 version @value{GDBVN}), you can make the Info file by typing:
38977 If you want to typeset and print copies of this manual, you need @TeX{},
38978 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38979 Texinfo definitions file.
38981 @TeX{} is a typesetting program; it does not print files directly, but
38982 produces output files called @sc{dvi} files. To print a typeset
38983 document, you need a program to print @sc{dvi} files. If your system
38984 has @TeX{} installed, chances are it has such a program. The precise
38985 command to use depends on your system; @kbd{lpr -d} is common; another
38986 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38987 require a file name without any extension or a @samp{.dvi} extension.
38989 @TeX{} also requires a macro definitions file called
38990 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38991 written in Texinfo format. On its own, @TeX{} cannot either read or
38992 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38993 and is located in the @file{gdb-@var{version-number}/texinfo}
38996 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38997 typeset and print this manual. First switch to the @file{gdb}
38998 subdirectory of the main source directory (for example, to
38999 @file{gdb-@value{GDBVN}/gdb}) and type:
39005 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
39007 @node Installing GDB
39008 @appendix Installing @value{GDBN}
39009 @cindex installation
39012 * Requirements:: Requirements for building @value{GDBN}
39013 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
39014 * Separate Objdir:: Compiling @value{GDBN} in another directory
39015 * Config Names:: Specifying names for hosts and targets
39016 * Configure Options:: Summary of options for configure
39017 * System-wide configuration:: Having a system-wide init file
39021 @section Requirements for Building @value{GDBN}
39022 @cindex building @value{GDBN}, requirements for
39024 Building @value{GDBN} requires various tools and packages to be available.
39025 Other packages will be used only if they are found.
39027 @heading Tools/Packages Necessary for Building @value{GDBN}
39029 @item C@t{++}11 compiler
39030 @value{GDBN} is written in C@t{++}11. It should be buildable with any
39031 recent C@t{++}11 compiler, e.g.@: GCC.
39034 @value{GDBN}'s build system relies on features only found in the GNU
39035 make program. Other variants of @code{make} will not work.
39037 @item GMP (The GNU Multiple Precision Arithmetic Library)
39038 @value{GDBN} now uses GMP to perform some of its arithmetics.
39039 This library may be included with your operating system distribution;
39040 if it is not, you can get the latest version from
39041 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
39042 you can use the @option{--with-libgmp-prefix} option to specify
39047 @heading Tools/Packages Optional for Building @value{GDBN}
39051 @value{GDBN} can use the Expat XML parsing library. This library may be
39052 included with your operating system distribution; if it is not, you
39053 can get the latest version from @url{http://expat.sourceforge.net}.
39054 The @file{configure} script will search for this library in several
39055 standard locations; if it is installed in an unusual path, you can
39056 use the @option{--with-libexpat-prefix} option to specify its location.
39062 Remote protocol memory maps (@pxref{Memory Map Format})
39064 Target descriptions (@pxref{Target Descriptions})
39066 Remote shared library lists (@xref{Library List Format},
39067 or alternatively @pxref{Library List Format for SVR4 Targets})
39069 MS-Windows shared libraries (@pxref{Shared Libraries})
39071 Traceframe info (@pxref{Traceframe Info Format})
39073 Branch trace (@pxref{Branch Trace Format},
39074 @pxref{Branch Trace Configuration Format})
39078 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
39079 default, @value{GDBN} will be compiled if the Guile libraries are
39080 installed and are found by @file{configure}. You can use the
39081 @code{--with-guile} option to request Guile, and pass either the Guile
39082 version number or the file name of the relevant @code{pkg-config}
39083 program to choose a particular version of Guile.
39086 @value{GDBN}'s features related to character sets (@pxref{Character
39087 Sets}) require a functioning @code{iconv} implementation. If you are
39088 on a GNU system, then this is provided by the GNU C Library. Some
39089 other systems also provide a working @code{iconv}.
39091 If @value{GDBN} is using the @code{iconv} program which is installed
39092 in a non-standard place, you will need to tell @value{GDBN} where to
39093 find it. This is done with @option{--with-iconv-bin} which specifies
39094 the directory that contains the @code{iconv} program. This program is
39095 run in order to make a list of the available character sets.
39097 On systems without @code{iconv}, you can install GNU Libiconv. If
39098 Libiconv is installed in a standard place, @value{GDBN} will
39099 automatically use it if it is needed. If you have previously
39100 installed Libiconv in a non-standard place, you can use the
39101 @option{--with-libiconv-prefix} option to @file{configure}.
39103 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
39104 arrange to build Libiconv if a directory named @file{libiconv} appears
39105 in the top-most source directory. If Libiconv is built this way, and
39106 if the operating system does not provide a suitable @code{iconv}
39107 implementation, then the just-built library will automatically be used
39108 by @value{GDBN}. One easy way to set this up is to download GNU
39109 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
39110 source tree, and then rename the directory holding the Libiconv source
39111 code to @samp{libiconv}.
39114 @value{GDBN} can support debugging sections that are compressed with
39115 the LZMA library. @xref{MiniDebugInfo}. If this library is not
39116 included with your operating system, you can find it in the xz package
39117 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
39118 the usual place, then the @file{configure} script will use it
39119 automatically. If it is installed in an unusual path, you can use the
39120 @option{--with-liblzma-prefix} option to specify its location.
39124 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
39125 library. This library may be included with your operating system
39126 distribution; if it is not, you can get the latest version from
39127 @url{http://www.mpfr.org}. The @file{configure} script will search
39128 for this library in several standard locations; if it is installed
39129 in an unusual path, you can use the @option{--with-libmpfr-prefix}
39130 option to specify its location.
39132 GNU MPFR is used to emulate target floating-point arithmetic during
39133 expression evaluation when the target uses different floating-point
39134 formats than the host. If GNU MPFR it is not available, @value{GDBN}
39135 will fall back to using host floating-point arithmetic.
39138 @value{GDBN} can be scripted using Python language. @xref{Python}.
39139 By default, @value{GDBN} will be compiled if the Python libraries are
39140 installed and are found by @file{configure}. You can use the
39141 @code{--with-python} option to request Python, and pass either the
39142 file name of the relevant @code{python} executable, or the name of the
39143 directory in which Python is installed, to choose a particular
39144 installation of Python.
39147 @cindex compressed debug sections
39148 @value{GDBN} will use the @samp{zlib} library, if available, to read
39149 compressed debug sections. Some linkers, such as GNU gold, are capable
39150 of producing binaries with compressed debug sections. If @value{GDBN}
39151 is compiled with @samp{zlib}, it will be able to read the debug
39152 information in such binaries.
39154 The @samp{zlib} library is likely included with your operating system
39155 distribution; if it is not, you can get the latest version from
39156 @url{http://zlib.net}.
39159 @node Running Configure
39160 @section Invoking the @value{GDBN} @file{configure} Script
39161 @cindex configuring @value{GDBN}
39162 @value{GDBN} comes with a @file{configure} script that automates the process
39163 of preparing @value{GDBN} for installation; you can then use @code{make} to
39164 build the @code{gdb} program.
39166 @c irrelevant in info file; it's as current as the code it lives with.
39167 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
39168 look at the @file{README} file in the sources; we may have improved the
39169 installation procedures since publishing this manual.}
39172 The @value{GDBN} distribution includes all the source code you need for
39173 @value{GDBN} in a single directory, whose name is usually composed by
39174 appending the version number to @samp{gdb}.
39176 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
39177 @file{gdb-@value{GDBVN}} directory. That directory contains:
39180 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
39181 script for configuring @value{GDBN} and all its supporting libraries
39183 @item gdb-@value{GDBVN}/gdb
39184 the source specific to @value{GDBN} itself
39186 @item gdb-@value{GDBVN}/bfd
39187 source for the Binary File Descriptor library
39189 @item gdb-@value{GDBVN}/include
39190 @sc{gnu} include files
39192 @item gdb-@value{GDBVN}/libiberty
39193 source for the @samp{-liberty} free software library
39195 @item gdb-@value{GDBVN}/opcodes
39196 source for the library of opcode tables and disassemblers
39198 @item gdb-@value{GDBVN}/readline
39199 source for the @sc{gnu} command-line interface
39202 There may be other subdirectories as well.
39204 The simplest way to configure and build @value{GDBN} is to run @file{configure}
39205 from the @file{gdb-@var{version-number}} source directory, which in
39206 this example is the @file{gdb-@value{GDBVN}} directory.
39208 First switch to the @file{gdb-@var{version-number}} source directory
39209 if you are not already in it; then run @file{configure}. Pass the
39210 identifier for the platform on which @value{GDBN} will run as an
39216 cd gdb-@value{GDBVN}
39221 Running @samp{configure} and then running @code{make} builds the
39222 included supporting libraries, then @code{gdb} itself. The configured
39223 source files, and the binaries, are left in the corresponding source
39227 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
39228 system does not recognize this automatically when you run a different
39229 shell, you may need to run @code{sh} on it explicitly:
39235 You should run the @file{configure} script from the top directory in the
39236 source tree, the @file{gdb-@var{version-number}} directory. If you run
39237 @file{configure} from one of the subdirectories, you will configure only
39238 that subdirectory. That is usually not what you want. In particular,
39239 if you run the first @file{configure} from the @file{gdb} subdirectory
39240 of the @file{gdb-@var{version-number}} directory, you will omit the
39241 configuration of @file{bfd}, @file{readline}, and other sibling
39242 directories of the @file{gdb} subdirectory. This leads to build errors
39243 about missing include files such as @file{bfd/bfd.h}.
39245 You can install @code{@value{GDBN}} anywhere. The best way to do this
39246 is to pass the @code{--prefix} option to @code{configure}, and then
39247 install it with @code{make install}.
39249 @node Separate Objdir
39250 @section Compiling @value{GDBN} in Another Directory
39252 If you want to run @value{GDBN} versions for several host or target machines,
39253 you need a different @code{gdb} compiled for each combination of
39254 host and target. @file{configure} is designed to make this easy by
39255 allowing you to generate each configuration in a separate subdirectory,
39256 rather than in the source directory. If your @code{make} program
39257 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
39258 @code{make} in each of these directories builds the @code{gdb}
39259 program specified there.
39261 To build @code{gdb} in a separate directory, run @file{configure}
39262 with the @samp{--srcdir} option to specify where to find the source.
39263 (You also need to specify a path to find @file{configure}
39264 itself from your working directory. If the path to @file{configure}
39265 would be the same as the argument to @samp{--srcdir}, you can leave out
39266 the @samp{--srcdir} option; it is assumed.)
39268 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
39269 separate directory for a Sun 4 like this:
39273 cd gdb-@value{GDBVN}
39276 ../gdb-@value{GDBVN}/configure
39281 When @file{configure} builds a configuration using a remote source
39282 directory, it creates a tree for the binaries with the same structure
39283 (and using the same names) as the tree under the source directory. In
39284 the example, you'd find the Sun 4 library @file{libiberty.a} in the
39285 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
39286 @file{gdb-sun4/gdb}.
39288 Make sure that your path to the @file{configure} script has just one
39289 instance of @file{gdb} in it. If your path to @file{configure} looks
39290 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
39291 one subdirectory of @value{GDBN}, not the whole package. This leads to
39292 build errors about missing include files such as @file{bfd/bfd.h}.
39294 One popular reason to build several @value{GDBN} configurations in separate
39295 directories is to configure @value{GDBN} for cross-compiling (where
39296 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39297 programs that run on another machine---the @dfn{target}).
39298 You specify a cross-debugging target by
39299 giving the @samp{--target=@var{target}} option to @file{configure}.
39301 When you run @code{make} to build a program or library, you must run
39302 it in a configured directory---whatever directory you were in when you
39303 called @file{configure} (or one of its subdirectories).
39305 The @code{Makefile} that @file{configure} generates in each source
39306 directory also runs recursively. If you type @code{make} in a source
39307 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39308 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39309 will build all the required libraries, and then build GDB.
39311 When you have multiple hosts or targets configured in separate
39312 directories, you can run @code{make} on them in parallel (for example,
39313 if they are NFS-mounted on each of the hosts); they will not interfere
39317 @section Specifying Names for Hosts and Targets
39319 The specifications used for hosts and targets in the @file{configure}
39320 script are based on a three-part naming scheme, but some short predefined
39321 aliases are also supported. The full naming scheme encodes three pieces
39322 of information in the following pattern:
39325 @var{architecture}-@var{vendor}-@var{os}
39328 For example, you can use the alias @code{sun4} as a @var{host} argument,
39329 or as the value for @var{target} in a @code{--target=@var{target}}
39330 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39332 The @file{configure} script accompanying @value{GDBN} does not provide
39333 any query facility to list all supported host and target names or
39334 aliases. @file{configure} calls the Bourne shell script
39335 @code{config.sub} to map abbreviations to full names; you can read the
39336 script, if you wish, or you can use it to test your guesses on
39337 abbreviations---for example:
39340 % sh config.sub i386-linux
39342 % sh config.sub alpha-linux
39343 alpha-unknown-linux-gnu
39344 % sh config.sub hp9k700
39346 % sh config.sub sun4
39347 sparc-sun-sunos4.1.1
39348 % sh config.sub sun3
39349 m68k-sun-sunos4.1.1
39350 % sh config.sub i986v
39351 Invalid configuration `i986v': machine `i986v' not recognized
39355 @code{config.sub} is also distributed in the @value{GDBN} source
39356 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39358 @node Configure Options
39359 @section @file{configure} Options
39361 Here is a summary of the @file{configure} options and arguments that
39362 are most often useful for building @value{GDBN}. @file{configure}
39363 also has several other options not listed here. @xref{Running
39364 configure Scripts,,,autoconf}, for a full
39365 explanation of @file{configure}.
39368 configure @r{[}--help@r{]}
39369 @r{[}--prefix=@var{dir}@r{]}
39370 @r{[}--exec-prefix=@var{dir}@r{]}
39371 @r{[}--srcdir=@var{dirname}@r{]}
39372 @r{[}--target=@var{target}@r{]}
39376 You may introduce options with a single @samp{-} rather than
39377 @samp{--} if you prefer; but you may abbreviate option names if you use
39382 Display a quick summary of how to invoke @file{configure}.
39384 @item --prefix=@var{dir}
39385 Configure the source to install programs and files under directory
39388 @item --exec-prefix=@var{dir}
39389 Configure the source to install programs under directory
39392 @c avoid splitting the warning from the explanation:
39394 @item --srcdir=@var{dirname}
39395 Use this option to make configurations in directories separate from the
39396 @value{GDBN} source directories. Among other things, you can use this to
39397 build (or maintain) several configurations simultaneously, in separate
39398 directories. @file{configure} writes configuration-specific files in
39399 the current directory, but arranges for them to use the source in the
39400 directory @var{dirname}. @file{configure} creates directories under
39401 the working directory in parallel to the source directories below
39404 @item --target=@var{target}
39405 Configure @value{GDBN} for cross-debugging programs running on the specified
39406 @var{target}. Without this option, @value{GDBN} is configured to debug
39407 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39409 There is no convenient way to generate a list of all available
39410 targets. Also see the @code{--enable-targets} option, below.
39413 There are many other options that are specific to @value{GDBN}. This
39414 lists just the most common ones; there are some very specialized
39415 options not described here.
39418 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39419 @itemx --enable-targets=all
39420 Configure @value{GDBN} for cross-debugging programs running on the
39421 specified list of targets. The special value @samp{all} configures
39422 @value{GDBN} for debugging programs running on any target it supports.
39424 @item --with-gdb-datadir=@var{path}
39425 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39426 here for certain supporting files or scripts. This defaults to the
39427 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39430 @item --with-relocated-sources=@var{dir}
39431 Sets up the default source path substitution rule so that directory
39432 names recorded in debug information will be automatically adjusted for
39433 any directory under @var{dir}. @var{dir} should be a subdirectory of
39434 @value{GDBN}'s configured prefix, the one mentioned in the
39435 @code{--prefix} or @code{--exec-prefix} options to configure. This
39436 option is useful if GDB is supposed to be moved to a different place
39439 @item --enable-64-bit-bfd
39440 Enable 64-bit support in BFD on 32-bit hosts.
39442 @item --disable-gdbmi
39443 Build @value{GDBN} without the GDB/MI machine interface
39447 Build @value{GDBN} with the text-mode full-screen user interface
39448 (TUI). Requires a curses library (ncurses and cursesX are also
39451 @item --with-curses
39452 Use the curses library instead of the termcap library, for text-mode
39453 terminal operations.
39455 @item --with-debuginfod
39456 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39457 library. Used to automatically fetch ELF, DWARF and source files from
39458 @code{debuginfod} servers using build IDs associated with any missing
39459 files. Enabled by default if @file{libdebuginfod} is installed and found
39460 at configure time. For more information regarding @code{debuginfod} see
39463 @item --with-libunwind-ia64
39464 Use the libunwind library for unwinding function call stack on ia64
39465 target platforms. See http://www.nongnu.org/libunwind/index.html for
39468 @item --with-system-readline
39469 Use the readline library installed on the host, rather than the
39470 library supplied as part of @value{GDBN}. Readline 7 or newer is
39471 required; this is enforced by the build system.
39473 @item --with-system-zlib
39474 Use the zlib library installed on the host, rather than the library
39475 supplied as part of @value{GDBN}.
39478 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39479 default if libexpat is installed and found at configure time.) This
39480 library is used to read XML files supplied with @value{GDBN}. If it
39481 is unavailable, some features, such as remote protocol memory maps,
39482 target descriptions, and shared library lists, that are based on XML
39483 files, will not be available in @value{GDBN}. If your host does not
39484 have libexpat installed, you can get the latest version from
39485 `http://expat.sourceforge.net'.
39487 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39489 Build @value{GDBN} with GNU libiconv, a character set encoding
39490 conversion library. This is not done by default, as on GNU systems
39491 the @code{iconv} that is built in to the C library is sufficient. If
39492 your host does not have a working @code{iconv}, you can get the latest
39493 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39495 @value{GDBN}'s build system also supports building GNU libiconv as
39496 part of the overall build. @xref{Requirements}.
39499 Build @value{GDBN} with LZMA, a compression library. (Done by default
39500 if liblzma is installed and found at configure time.) LZMA is used by
39501 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39502 platforms using the ELF object file format. If your host does not
39503 have liblzma installed, you can get the latest version from
39504 `https://tukaani.org/xz/'.
39507 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39508 floating-point computation with correct rounding. (Done by default if
39509 GNU MPFR is installed and found at configure time.) This library is
39510 used to emulate target floating-point arithmetic during expression
39511 evaluation when the target uses different floating-point formats than
39512 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39513 to using host floating-point arithmetic. If your host does not have
39514 GNU MPFR installed, you can get the latest version from
39515 `http://www.mpfr.org'.
39517 @item --with-python@r{[}=@var{python}@r{]}
39518 Build @value{GDBN} with Python scripting support. (Done by default if
39519 libpython is present and found at configure time.) Python makes
39520 @value{GDBN} scripting much more powerful than the restricted CLI
39521 scripting language. If your host does not have Python installed, you
39522 can find it on `http://www.python.org/download/'. The oldest version
39523 of Python supported by GDB is 2.6. The optional argument @var{python}
39524 is used to find the Python headers and libraries. It can be either
39525 the name of a Python executable, or the name of the directory in which
39526 Python is installed.
39528 @item --with-guile[=GUILE]'
39529 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39530 if libguile is present and found at configure time.) If your host
39531 does not have Guile installed, you can find it at
39532 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39533 can be a version number, which will cause @code{configure} to try to
39534 use that version of Guile; or the file name of a @code{pkg-config}
39535 executable, which will be queried to find the information needed to
39536 compile and link against Guile.
39538 @item --without-included-regex
39539 Don't use the regex library included with @value{GDBN} (as part of the
39540 libiberty library). This is the default on hosts with version 2 of
39543 @item --with-sysroot=@var{dir}
39544 Use @var{dir} as the default system root directory for libraries whose
39545 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39546 @var{dir} can be modified at run time by using the @command{set
39547 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39548 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39549 default system root will be automatically adjusted if and when
39550 @value{GDBN} is moved to a different location.
39552 @item --with-system-gdbinit=@var{file}
39553 Configure @value{GDBN} to automatically load a system-wide init file.
39554 @var{file} should be an absolute file name. If @var{file} is in a
39555 directory under the configured prefix, and @value{GDBN} is moved to
39556 another location after being built, the location of the system-wide
39557 init file will be adjusted accordingly.
39559 @item --with-system-gdbinit-dir=@var{directory}
39560 Configure @value{GDBN} to automatically load init files from a
39561 system-wide directory. @var{directory} should be an absolute directory
39562 name. If @var{directory} is in a directory under the configured
39563 prefix, and @value{GDBN} is moved to another location after being
39564 built, the location of the system-wide init directory will be
39565 adjusted accordingly.
39567 @item --enable-build-warnings
39568 When building the @value{GDBN} sources, ask the compiler to warn about
39569 any code which looks even vaguely suspicious. It passes many
39570 different warning flags, depending on the exact version of the
39571 compiler you are using.
39573 @item --enable-werror
39574 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39575 to the compiler, which will fail the compilation if the compiler
39576 outputs any warning messages.
39578 @item --enable-ubsan
39579 Enable the GCC undefined behavior sanitizer. This is disabled by
39580 default, but passing @code{--enable-ubsan=yes} or
39581 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39582 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39583 It has a performance cost, so if you are looking at @value{GDBN}'s
39584 performance, you should disable it. The undefined behavior sanitizer
39585 was first introduced in GCC 4.9.
39588 @node System-wide configuration
39589 @section System-wide configuration and settings
39590 @cindex system-wide init file
39592 @value{GDBN} can be configured to have a system-wide init file and a
39593 system-wide init file directory; this file and files in that directory
39594 (if they have a recognized file extension) will be read and executed at
39595 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39597 Here are the corresponding configure options:
39600 @item --with-system-gdbinit=@var{file}
39601 Specify that the default location of the system-wide init file is
39603 @item --with-system-gdbinit-dir=@var{directory}
39604 Specify that the default location of the system-wide init file directory
39605 is @var{directory}.
39608 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39609 they may be subject to relocation. Two possible cases:
39613 If the default location of this init file/directory contains @file{$prefix},
39614 it will be subject to relocation. Suppose that the configure options
39615 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39616 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39617 init file is looked for as @file{$install/etc/gdbinit} instead of
39618 @file{$prefix/etc/gdbinit}.
39621 By contrast, if the default location does not contain the prefix,
39622 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39623 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39624 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39625 wherever @value{GDBN} is installed.
39628 If the configured location of the system-wide init file (as given by the
39629 @option{--with-system-gdbinit} option at configure time) is in the
39630 data-directory (as specified by @option{--with-gdb-datadir} at configure
39631 time) or in one of its subdirectories, then @value{GDBN} will look for the
39632 system-wide init file in the directory specified by the
39633 @option{--data-directory} command-line option.
39634 Note that the system-wide init file is only read once, during @value{GDBN}
39635 initialization. If the data-directory is changed after @value{GDBN} has
39636 started with the @code{set data-directory} command, the file will not be
39639 This applies similarly to the system-wide directory specified in
39640 @option{--with-system-gdbinit-dir}.
39642 Any supported scripting language can be used for these init files, as long
39643 as the file extension matches the scripting language. To be interpreted
39644 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39648 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39651 @node System-wide Configuration Scripts
39652 @subsection Installed System-wide Configuration Scripts
39653 @cindex system-wide configuration scripts
39655 The @file{system-gdbinit} directory, located inside the data-directory
39656 (as specified by @option{--with-gdb-datadir} at configure time) contains
39657 a number of scripts which can be used as system-wide init files. To
39658 automatically source those scripts at startup, @value{GDBN} should be
39659 configured with @option{--with-system-gdbinit}. Otherwise, any user
39660 should be able to source them by hand as needed.
39662 The following scripts are currently available:
39665 @item @file{elinos.py}
39667 @cindex ELinOS system-wide configuration script
39668 This script is useful when debugging a program on an ELinOS target.
39669 It takes advantage of the environment variables defined in a standard
39670 ELinOS environment in order to determine the location of the system
39671 shared libraries, and then sets the @samp{solib-absolute-prefix}
39672 and @samp{solib-search-path} variables appropriately.
39674 @item @file{wrs-linux.py}
39675 @pindex wrs-linux.py
39676 @cindex Wind River Linux system-wide configuration script
39677 This script is useful when debugging a program on a target running
39678 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39679 the host-side sysroot used by the target system.
39683 @node Maintenance Commands
39684 @appendix Maintenance Commands
39685 @cindex maintenance commands
39686 @cindex internal commands
39688 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39689 includes a number of commands intended for @value{GDBN} developers,
39690 that are not documented elsewhere in this manual. These commands are
39691 provided here for reference. (For commands that turn on debugging
39692 messages, see @ref{Debugging Output}.)
39695 @kindex maint agent
39696 @kindex maint agent-eval
39697 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39698 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39699 Translate the given @var{expression} into remote agent bytecodes.
39700 This command is useful for debugging the Agent Expression mechanism
39701 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39702 expression useful for data collection, such as by tracepoints, while
39703 @samp{maint agent-eval} produces an expression that evaluates directly
39704 to a result. For instance, a collection expression for @code{globa +
39705 globb} will include bytecodes to record four bytes of memory at each
39706 of the addresses of @code{globa} and @code{globb}, while discarding
39707 the result of the addition, while an evaluation expression will do the
39708 addition and return the sum.
39709 If @code{-at} is given, generate remote agent bytecode for all the
39710 addresses to which @var{linespec} resolves (@pxref{Linespec
39712 If not, generate remote agent bytecode for current frame PC address.
39714 @kindex maint agent-printf
39715 @item maint agent-printf @var{format},@var{expr},...
39716 Translate the given format string and list of argument expressions
39717 into remote agent bytecodes and display them as a disassembled list.
39718 This command is useful for debugging the agent version of dynamic
39719 printf (@pxref{Dynamic Printf}).
39721 @kindex maint info breakpoints
39722 @item @anchor{maint info breakpoints}maint info breakpoints
39723 Using the same format as @samp{info breakpoints}, display both the
39724 breakpoints you've set explicitly, and those @value{GDBN} is using for
39725 internal purposes. Internal breakpoints are shown with negative
39726 breakpoint numbers. The type column identifies what kind of breakpoint
39731 Normal, explicitly set breakpoint.
39734 Normal, explicitly set watchpoint.
39737 Internal breakpoint, used to handle correctly stepping through
39738 @code{longjmp} calls.
39740 @item longjmp resume
39741 Internal breakpoint at the target of a @code{longjmp}.
39744 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39747 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39750 Shared library events.
39754 @kindex maint info btrace
39755 @item maint info btrace
39756 Pint information about raw branch tracing data.
39758 @kindex maint btrace packet-history
39759 @item maint btrace packet-history
39760 Print the raw branch trace packets that are used to compute the
39761 execution history for the @samp{record btrace} command. Both the
39762 information and the format in which it is printed depend on the btrace
39767 For the BTS recording format, print a list of blocks of sequential
39768 code. For each block, the following information is printed:
39772 Newer blocks have higher numbers. The oldest block has number zero.
39773 @item Lowest @samp{PC}
39774 @item Highest @samp{PC}
39778 For the Intel Processor Trace recording format, print a list of
39779 Intel Processor Trace packets. For each packet, the following
39780 information is printed:
39783 @item Packet number
39784 Newer packets have higher numbers. The oldest packet has number zero.
39786 The packet's offset in the trace stream.
39787 @item Packet opcode and payload
39791 @kindex maint btrace clear-packet-history
39792 @item maint btrace clear-packet-history
39793 Discards the cached packet history printed by the @samp{maint btrace
39794 packet-history} command. The history will be computed again when
39797 @kindex maint btrace clear
39798 @item maint btrace clear
39799 Discard the branch trace data. The data will be fetched anew and the
39800 branch trace will be recomputed when needed.
39802 This implicitly truncates the branch trace to a single branch trace
39803 buffer. When updating branch trace incrementally, the branch trace
39804 available to @value{GDBN} may be bigger than a single branch trace
39807 @kindex maint set btrace pt skip-pad
39808 @item maint set btrace pt skip-pad
39809 @kindex maint show btrace pt skip-pad
39810 @item maint show btrace pt skip-pad
39811 Control whether @value{GDBN} will skip PAD packets when computing the
39814 @kindex maint info jit
39815 @item maint info jit
39816 Print information about JIT code objects loaded in the current inferior.
39818 @anchor{maint info python-disassemblers}
39819 @kindex maint info python-disassemblers
39820 @item maint info python-disassemblers
39821 This command is defined within the @code{gdb.disassembler} Python
39822 module (@pxref{Disassembly In Python}), and will only be present after
39823 that module has been imported. To force the module to be imported do
39827 (@value{GDBP}) python import gdb.disassembler
39830 This command lists all the architectures for which a disassembler is
39831 currently registered, and the name of the disassembler. If a
39832 disassembler is registered for all architectures, then this is listed
39833 last against the @samp{GLOBAL} architecture.
39835 If one of the disassemblers would be selected for the architecture of
39836 the current inferior, then this disassembler will be marked.
39838 The following example shows a situation in which two disassemblers are
39839 registered, initially the @samp{i386} disassembler matches the current
39840 architecture, then the architecture is changed, now the @samp{GLOBAL}
39841 disassembler matches.
39845 (@value{GDBP}) show architecture
39846 The target architecture is set to "auto" (currently "i386").
39847 (@value{GDBP}) maint info python-disassemblers
39848 Architecture Disassember Name
39849 i386 Disassembler_1 (Matches current architecture)
39850 GLOBAL Disassembler_2
39853 (@value{GDBP}) set architecture arm
39854 The target architecture is set to "arm".
39855 (@value{GDBP}) maint info python-disassemblers
39857 Architecture Disassember Name
39858 i386 Disassembler_1
39859 GLOBAL Disassembler_2 (Matches current architecture)
39863 @kindex set displaced-stepping
39864 @kindex show displaced-stepping
39865 @cindex displaced stepping support
39866 @cindex out-of-line single-stepping
39867 @item set displaced-stepping
39868 @itemx show displaced-stepping
39869 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39870 if the target supports it. Displaced stepping is a way to single-step
39871 over breakpoints without removing them from the inferior, by executing
39872 an out-of-line copy of the instruction that was originally at the
39873 breakpoint location. It is also known as out-of-line single-stepping.
39876 @item set displaced-stepping on
39877 If the target architecture supports it, @value{GDBN} will use
39878 displaced stepping to step over breakpoints.
39880 @item set displaced-stepping off
39881 @value{GDBN} will not use displaced stepping to step over breakpoints,
39882 even if such is supported by the target architecture.
39884 @cindex non-stop mode, and @samp{set displaced-stepping}
39885 @item set displaced-stepping auto
39886 This is the default mode. @value{GDBN} will use displaced stepping
39887 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39888 architecture supports displaced stepping.
39891 @kindex maint check-psymtabs
39892 @item maint check-psymtabs
39893 Check the consistency of currently expanded psymtabs versus symtabs.
39894 Use this to check, for example, whether a symbol is in one but not the other.
39896 @kindex maint check-symtabs
39897 @item maint check-symtabs
39898 Check the consistency of currently expanded symtabs.
39900 @kindex maint expand-symtabs
39901 @item maint expand-symtabs [@var{regexp}]
39902 Expand symbol tables.
39903 If @var{regexp} is specified, only expand symbol tables for file
39904 names matching @var{regexp}.
39906 @kindex maint set catch-demangler-crashes
39907 @kindex maint show catch-demangler-crashes
39908 @cindex demangler crashes
39909 @item maint set catch-demangler-crashes [on|off]
39910 @itemx maint show catch-demangler-crashes
39911 Control whether @value{GDBN} should attempt to catch crashes in the
39912 symbol name demangler. The default is to attempt to catch crashes.
39913 If enabled, the first time a crash is caught, a core file is created,
39914 the offending symbol is displayed and the user is presented with the
39915 option to terminate the current session.
39917 @kindex maint cplus first_component
39918 @item maint cplus first_component @var{name}
39919 Print the first C@t{++} class/namespace component of @var{name}.
39921 @kindex maint cplus namespace
39922 @item maint cplus namespace
39923 Print the list of possible C@t{++} namespaces.
39925 @kindex maint deprecate
39926 @kindex maint undeprecate
39927 @cindex deprecated commands
39928 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39929 @itemx maint undeprecate @var{command}
39930 Deprecate or undeprecate the named @var{command}. Deprecated commands
39931 cause @value{GDBN} to issue a warning when you use them. The optional
39932 argument @var{replacement} says which newer command should be used in
39933 favor of the deprecated one; if it is given, @value{GDBN} will mention
39934 the replacement as part of the warning.
39936 @kindex maint dump-me
39937 @item maint dump-me
39938 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39939 Cause a fatal signal in the debugger and force it to dump its core.
39940 This is supported only on systems which support aborting a program
39941 with the @code{SIGQUIT} signal.
39943 @kindex maint internal-error
39944 @kindex maint internal-warning
39945 @kindex maint demangler-warning
39946 @cindex demangler crashes
39947 @item maint internal-error @r{[}@var{message-text}@r{]}
39948 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39949 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39951 Cause @value{GDBN} to call the internal function @code{internal_error},
39952 @code{internal_warning} or @code{demangler_warning} and hence behave
39953 as though an internal problem has been detected. In addition to
39954 reporting the internal problem, these functions give the user the
39955 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39956 and @code{internal_warning}) create a core file of the current
39957 @value{GDBN} session.
39959 These commands take an optional parameter @var{message-text} that is
39960 used as the text of the error or warning message.
39962 Here's an example of using @code{internal-error}:
39965 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39966 @dots{}/maint.c:121: internal-error: testing, 1, 2
39967 A problem internal to GDB has been detected. Further
39968 debugging may prove unreliable.
39969 Quit this debugging session? (y or n) @kbd{n}
39970 Create a core file? (y or n) @kbd{n}
39974 @cindex @value{GDBN} internal error
39975 @cindex internal errors, control of @value{GDBN} behavior
39976 @cindex demangler crashes
39978 @kindex maint set internal-error
39979 @kindex maint show internal-error
39980 @kindex maint set internal-warning
39981 @kindex maint show internal-warning
39982 @kindex maint set demangler-warning
39983 @kindex maint show demangler-warning
39984 @item maint set internal-error @var{action} [ask|yes|no]
39985 @itemx maint show internal-error @var{action}
39986 @itemx maint set internal-warning @var{action} [ask|yes|no]
39987 @itemx maint show internal-warning @var{action}
39988 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39989 @itemx maint show demangler-warning @var{action}
39990 When @value{GDBN} reports an internal problem (error or warning) it
39991 gives the user the opportunity to both quit @value{GDBN} and create a
39992 core file of the current @value{GDBN} session. These commands let you
39993 override the default behaviour for each particular @var{action},
39994 described in the table below.
39998 You can specify that @value{GDBN} should always (yes) or never (no)
39999 quit. The default is to ask the user what to do.
40002 You can specify that @value{GDBN} should always (yes) or never (no)
40003 create a core file. The default is to ask the user what to do. Note
40004 that there is no @code{corefile} option for @code{demangler-warning}:
40005 demangler warnings always create a core file and this cannot be
40009 @kindex maint set internal-error
40010 @kindex maint show internal-error
40011 @kindex maint set internal-warning
40012 @kindex maint show internal-warning
40013 @item maint set internal-error backtrace @r{[}on|off@r{]}
40014 @itemx maint show internal-error backtrace
40015 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
40016 @itemx maint show internal-warning backtrace
40017 When @value{GDBN} reports an internal problem (error or warning) it is
40018 possible to have a backtrace of @value{GDBN} printed to the standard
40019 error stream. This is @samp{on} by default for @code{internal-error}
40020 and @samp{off} by default for @code{internal-warning}.
40022 @anchor{maint packet}
40023 @kindex maint packet
40024 @item maint packet @var{text}
40025 If @value{GDBN} is talking to an inferior via the serial protocol,
40026 then this command sends the string @var{text} to the inferior, and
40027 displays the response packet. @value{GDBN} supplies the initial
40028 @samp{$} character, the terminating @samp{#} character, and the
40031 Any non-printable characters in the reply are printed as escaped hex,
40032 e.g. @samp{\x00}, @samp{\x01}, etc.
40034 @kindex maint print architecture
40035 @item maint print architecture @r{[}@var{file}@r{]}
40036 Print the entire architecture configuration. The optional argument
40037 @var{file} names the file where the output goes.
40039 @kindex maint print c-tdesc
40040 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
40041 Print the target description (@pxref{Target Descriptions}) as
40042 a C source file. By default, the target description is for the current
40043 target, but if the optional argument @var{file} is provided, that file
40044 is used to produce the description. The @var{file} should be an XML
40045 document, of the form described in @ref{Target Description Format}.
40046 The created source file is built into @value{GDBN} when @value{GDBN} is
40047 built again. This command is used by developers after they add or
40048 modify XML target descriptions.
40050 When the optional flag @samp{-single-feature} is provided then the
40051 target description being processed (either the default, or from
40052 @var{file}) must only contain a single feature. The source file
40053 produced is different in this case.
40055 @kindex maint print xml-tdesc
40056 @item maint print xml-tdesc @r{[}@var{file}@r{]}
40057 Print the target description (@pxref{Target Descriptions}) as an XML
40058 file. By default print the target description for the current target,
40059 but if the optional argument @var{file} is provided, then that file is
40060 read in by GDB and then used to produce the description. The
40061 @var{file} should be an XML document, of the form described in
40062 @ref{Target Description Format}.
40064 @kindex maint check xml-descriptions
40065 @item maint check xml-descriptions @var{dir}
40066 Check that the target descriptions dynamically created by @value{GDBN}
40067 equal the descriptions created from XML files found in @var{dir}.
40069 @anchor{maint check libthread-db}
40070 @kindex maint check libthread-db
40071 @item maint check libthread-db
40072 Run integrity checks on the current inferior's thread debugging
40073 library. This exercises all @code{libthread_db} functionality used by
40074 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
40075 @code{proc_service} functions provided by @value{GDBN} that
40076 @code{libthread_db} uses. Note that parts of the test may be skipped
40077 on some platforms when debugging core files.
40079 @kindex maint print core-file-backed-mappings
40080 @cindex memory address space mappings
40081 @item maint print core-file-backed-mappings
40082 Print the file-backed mappings which were loaded from a core file note.
40083 This output represents state internal to @value{GDBN} and should be
40084 similar to the mappings displayed by the @code{info proc mappings}
40087 @kindex maint print dummy-frames
40088 @item maint print dummy-frames
40089 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
40092 (@value{GDBP}) @kbd{b add}
40094 (@value{GDBP}) @kbd{print add(2,3)}
40095 Breakpoint 2, add (a=2, b=3) at @dots{}
40097 The program being debugged stopped while in a function called from GDB.
40099 (@value{GDBP}) @kbd{maint print dummy-frames}
40100 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
40104 Takes an optional file parameter.
40106 @kindex maint print registers
40107 @kindex maint print raw-registers
40108 @kindex maint print cooked-registers
40109 @kindex maint print register-groups
40110 @kindex maint print remote-registers
40111 @item maint print registers @r{[}@var{file}@r{]}
40112 @itemx maint print raw-registers @r{[}@var{file}@r{]}
40113 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
40114 @itemx maint print register-groups @r{[}@var{file}@r{]}
40115 @itemx maint print remote-registers @r{[}@var{file}@r{]}
40116 Print @value{GDBN}'s internal register data structures.
40118 The command @code{maint print raw-registers} includes the contents of
40119 the raw register cache; the command @code{maint print
40120 cooked-registers} includes the (cooked) value of all registers,
40121 including registers which aren't available on the target nor visible
40122 to user; the command @code{maint print register-groups} includes the
40123 groups that each register is a member of; and the command @code{maint
40124 print remote-registers} includes the remote target's register numbers
40125 and offsets in the `G' packets.
40127 These commands take an optional parameter, a file name to which to
40128 write the information.
40130 @kindex maint print reggroups
40131 @item maint print reggroups @r{[}@var{file}@r{]}
40132 Print @value{GDBN}'s internal register group data structures. The
40133 optional argument @var{file} tells to what file to write the
40136 The register groups info looks like this:
40139 (@value{GDBP}) @kbd{maint print reggroups}
40150 @kindex maint flush register-cache
40152 @cindex register cache, flushing
40153 @item maint flush register-cache
40155 Flush the contents of the register cache and as a consequence the
40156 frame cache. This command is useful when debugging issues related to
40157 register fetching, or frame unwinding. The command @code{flushregs}
40158 is deprecated in favor of @code{maint flush register-cache}.
40160 @kindex maint flush source-cache
40161 @cindex source code, caching
40162 @item maint flush source-cache
40163 Flush @value{GDBN}'s cache of source code file contents. After
40164 @value{GDBN} reads a source file, and optionally applies styling
40165 (@pxref{Output Styling}), the file contents are cached. This command
40166 clears that cache. The next time @value{GDBN} wants to show lines
40167 from a source file, the content will be re-read.
40169 This command is useful when debugging issues related to source code
40170 styling. After flushing the cache any source code displayed by
40171 @value{GDBN} will be re-read and re-styled.
40173 @kindex maint print objfiles
40174 @cindex info for known object files
40175 @item maint print objfiles @r{[}@var{regexp}@r{]}
40176 Print a dump of all known object files.
40177 If @var{regexp} is specified, only print object files whose names
40178 match @var{regexp}. For each object file, this command prints its name,
40179 address in memory, and all of its psymtabs and symtabs.
40181 @kindex maint print user-registers
40182 @cindex user registers
40183 @item maint print user-registers
40184 List all currently available @dfn{user registers}. User registers
40185 typically provide alternate names for actual hardware registers. They
40186 include the four ``standard'' registers @code{$fp}, @code{$pc},
40187 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
40188 registers can be used in expressions in the same way as the canonical
40189 register names, but only the latter are listed by the @code{info
40190 registers} and @code{maint print registers} commands.
40192 @kindex maint print section-scripts
40193 @cindex info for known .debug_gdb_scripts-loaded scripts
40194 @item maint print section-scripts [@var{regexp}]
40195 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
40196 If @var{regexp} is specified, only print scripts loaded by object files
40197 matching @var{regexp}.
40198 For each script, this command prints its name as specified in the objfile,
40199 and the full path if known.
40200 @xref{dotdebug_gdb_scripts section}.
40202 @kindex maint print statistics
40203 @cindex bcache statistics
40204 @item maint print statistics
40205 This command prints, for each object file in the program, various data
40206 about that object file followed by the byte cache (@dfn{bcache})
40207 statistics for the object file. The objfile data includes the number
40208 of minimal, partial, full, and stabs symbols, the number of types
40209 defined by the objfile, the number of as yet unexpanded psym tables,
40210 the number of line tables and string tables, and the amount of memory
40211 used by the various tables. The bcache statistics include the counts,
40212 sizes, and counts of duplicates of all and unique objects, max,
40213 average, and median entry size, total memory used and its overhead and
40214 savings, and various measures of the hash table size and chain
40217 @kindex maint print target-stack
40218 @cindex target stack description
40219 @item maint print target-stack
40220 A @dfn{target} is an interface between the debugger and a particular
40221 kind of file or process. Targets can be stacked in @dfn{strata},
40222 so that more than one target can potentially respond to a request.
40223 In particular, memory accesses will walk down the stack of targets
40224 until they find a target that is interested in handling that particular
40227 This command prints a short description of each layer that was pushed on
40228 the @dfn{target stack}, starting from the top layer down to the bottom one.
40230 @kindex maint print type
40231 @cindex type chain of a data type
40232 @item maint print type @var{expr}
40233 Print the type chain for a type specified by @var{expr}. The argument
40234 can be either a type name or a symbol. If it is a symbol, the type of
40235 that symbol is described. The type chain produced by this command is
40236 a recursive definition of the data type as stored in @value{GDBN}'s
40237 data structures, including its flags and contained types.
40239 @kindex maint selftest
40241 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
40242 Run any self tests that were compiled in to @value{GDBN}. This will
40243 print a message showing how many tests were run, and how many failed.
40244 If a @var{filter} is passed, only the tests with @var{filter} in their
40245 name will be ran. If @code{-verbose} is passed, the self tests can be
40248 @kindex maint set selftest verbose
40249 @kindex maint show selftest verbose
40251 @item maint set selftest verbose
40252 @item maint show selftest verbose
40253 Control whether self tests are run verbosely or not.
40255 @kindex maint info selftests
40257 @item maint info selftests
40258 List the selftests compiled in to @value{GDBN}.
40260 @kindex maint set dwarf always-disassemble
40261 @kindex maint show dwarf always-disassemble
40262 @item maint set dwarf always-disassemble
40263 @item maint show dwarf always-disassemble
40264 Control the behavior of @code{info address} when using DWARF debugging
40267 The default is @code{off}, which means that @value{GDBN} should try to
40268 describe a variable's location in an easily readable format. When
40269 @code{on}, @value{GDBN} will instead display the DWARF location
40270 expression in an assembly-like format. Note that some locations are
40271 too complex for @value{GDBN} to describe simply; in this case you will
40272 always see the disassembly form.
40274 Here is an example of the resulting disassembly:
40277 (gdb) info addr argc
40278 Symbol "argc" is a complex DWARF expression:
40282 For more information on these expressions, see
40283 @uref{http://www.dwarfstd.org/, the DWARF standard}.
40285 @kindex maint set dwarf max-cache-age
40286 @kindex maint show dwarf max-cache-age
40287 @item maint set dwarf max-cache-age
40288 @itemx maint show dwarf max-cache-age
40289 Control the DWARF compilation unit cache.
40291 @cindex DWARF compilation units cache
40292 In object files with inter-compilation-unit references, such as those
40293 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
40294 reader needs to frequently refer to previously read compilation units.
40295 This setting controls how long a compilation unit will remain in the
40296 cache if it is not referenced. A higher limit means that cached
40297 compilation units will be stored in memory longer, and more total
40298 memory will be used. Setting it to zero disables caching, which will
40299 slow down @value{GDBN} startup, but reduce memory consumption.
40301 @kindex maint set dwarf unwinders
40302 @kindex maint show dwarf unwinders
40303 @item maint set dwarf unwinders
40304 @itemx maint show dwarf unwinders
40305 Control use of the DWARF frame unwinders.
40307 @cindex DWARF frame unwinders
40308 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
40309 frame unwinders to build the backtrace. Many of these targets will
40310 also have a second mechanism for building the backtrace for use in
40311 cases where DWARF information is not available, this second mechanism
40312 is often an analysis of a function's prologue.
40314 In order to extend testing coverage of the second level stack
40315 unwinding mechanisms it is helpful to be able to disable the DWARF
40316 stack unwinders, this can be done with this switch.
40318 In normal use of @value{GDBN} disabling the DWARF unwinders is not
40319 advisable, there are cases that are better handled through DWARF than
40320 prologue analysis, and the debug experience is likely to be better
40321 with the DWARF frame unwinders enabled.
40323 If DWARF frame unwinders are not supported for a particular target
40324 architecture, then enabling this flag does not cause them to be used.
40326 @kindex maint set worker-threads
40327 @kindex maint show worker-threads
40328 @item maint set worker-threads
40329 @item maint show worker-threads
40330 Control the number of worker threads that may be used by @value{GDBN}.
40331 On capable hosts, @value{GDBN} may use multiple threads to speed up
40332 certain CPU-intensive operations, such as demangling symbol names.
40333 While the number of threads used by @value{GDBN} may vary, this
40334 command can be used to set an upper bound on this number. The default
40335 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
40336 number. Note that this only controls worker threads started by
40337 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
40340 @kindex maint set profile
40341 @kindex maint show profile
40342 @cindex profiling GDB
40343 @item maint set profile
40344 @itemx maint show profile
40345 Control profiling of @value{GDBN}.
40347 Profiling will be disabled until you use the @samp{maint set profile}
40348 command to enable it. When you enable profiling, the system will begin
40349 collecting timing and execution count data; when you disable profiling or
40350 exit @value{GDBN}, the results will be written to a log file. Remember that
40351 if you use profiling, @value{GDBN} will overwrite the profiling log file
40352 (often called @file{gmon.out}). If you have a record of important profiling
40353 data in a @file{gmon.out} file, be sure to move it to a safe location.
40355 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40356 compiled with the @samp{-pg} compiler option.
40358 @kindex maint set show-debug-regs
40359 @kindex maint show show-debug-regs
40360 @cindex hardware debug registers
40361 @item maint set show-debug-regs
40362 @itemx maint show show-debug-regs
40363 Control whether to show variables that mirror the hardware debug
40364 registers. Use @code{on} to enable, @code{off} to disable. If
40365 enabled, the debug registers values are shown when @value{GDBN} inserts or
40366 removes a hardware breakpoint or watchpoint, and when the inferior
40367 triggers a hardware-assisted breakpoint or watchpoint.
40369 @kindex maint set show-all-tib
40370 @kindex maint show show-all-tib
40371 @item maint set show-all-tib
40372 @itemx maint show show-all-tib
40373 Control whether to show all non zero areas within a 1k block starting
40374 at thread local base, when using the @samp{info w32 thread-information-block}
40377 @kindex maint set target-async
40378 @kindex maint show target-async
40379 @item maint set target-async
40380 @itemx maint show target-async
40381 This controls whether @value{GDBN} targets operate in synchronous or
40382 asynchronous mode (@pxref{Background Execution}). Normally the
40383 default is asynchronous, if it is available; but this can be changed
40384 to more easily debug problems occurring only in synchronous mode.
40386 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40387 @kindex maint show target-non-stop
40388 @item maint set target-non-stop
40389 @itemx maint show target-non-stop
40391 This controls whether @value{GDBN} targets always operate in non-stop
40392 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40393 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40394 if supported by the target.
40397 @item maint set target-non-stop auto
40398 This is the default mode. @value{GDBN} controls the target in
40399 non-stop mode if the target supports it.
40401 @item maint set target-non-stop on
40402 @value{GDBN} controls the target in non-stop mode even if the target
40403 does not indicate support.
40405 @item maint set target-non-stop off
40406 @value{GDBN} does not control the target in non-stop mode even if the
40407 target supports it.
40410 @kindex maint set tui-resize-message
40411 @kindex maint show tui-resize-message
40412 @item maint set tui-resize-message
40413 @item maint show tui-resize-message
40414 Control whether @value{GDBN} displays a message each time the terminal
40415 is resized when in TUI mode. The default is @code{off}, which means
40416 that @value{GDBN} is silent during resizes. When @code{on},
40417 @value{GDBN} will display a message after a resize is completed; the
40418 message will include a number indicating how many times the terminal
40419 has been resized. This setting is intended for use by the test suite,
40420 where it would otherwise be difficult to determine when a resize and
40421 refresh has been completed.
40423 @kindex maint set per-command
40424 @kindex maint show per-command
40425 @item maint set per-command
40426 @itemx maint show per-command
40427 @cindex resources used by commands
40429 @value{GDBN} can display the resources used by each command.
40430 This is useful in debugging performance problems.
40433 @item maint set per-command space [on|off]
40434 @itemx maint show per-command space
40435 Enable or disable the printing of the memory used by GDB for each command.
40436 If enabled, @value{GDBN} will display how much memory each command
40437 took, following the command's own output.
40438 This can also be requested by invoking @value{GDBN} with the
40439 @option{--statistics} command-line switch (@pxref{Mode Options}).
40441 @item maint set per-command time [on|off]
40442 @itemx maint show per-command time
40443 Enable or disable the printing of the execution time of @value{GDBN}
40445 If enabled, @value{GDBN} will display how much time it
40446 took to execute each command, following the command's own output.
40447 Both CPU time and wallclock time are printed.
40448 Printing both is useful when trying to determine whether the cost is
40449 CPU or, e.g., disk/network latency.
40450 Note that the CPU time printed is for @value{GDBN} only, it does not include
40451 the execution time of the inferior because there's no mechanism currently
40452 to compute how much time was spent by @value{GDBN} and how much time was
40453 spent by the program been debugged.
40454 This can also be requested by invoking @value{GDBN} with the
40455 @option{--statistics} command-line switch (@pxref{Mode Options}).
40457 @item maint set per-command symtab [on|off]
40458 @itemx maint show per-command symtab
40459 Enable or disable the printing of basic symbol table statistics
40461 If enabled, @value{GDBN} will display the following information:
40465 number of symbol tables
40467 number of primary symbol tables
40469 number of blocks in the blockvector
40473 @kindex maint set check-libthread-db
40474 @kindex maint show check-libthread-db
40475 @item maint set check-libthread-db [on|off]
40476 @itemx maint show check-libthread-db
40477 Control whether @value{GDBN} should run integrity checks on inferior
40478 specific thread debugging libraries as they are loaded. The default
40479 is not to perform such checks. If any check fails @value{GDBN} will
40480 unload the library and continue searching for a suitable candidate as
40481 described in @ref{set libthread-db-search-path}. For more information
40482 about the tests, see @ref{maint check libthread-db}.
40484 @kindex maint set gnu-source-highlight enabled
40485 @kindex maint show gnu-source-highlight enabled
40486 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40487 @itemx maint show gnu-source-highlight enabled
40488 Control whether @value{GDBN} should use the GNU Source Highlight
40489 library for applying styling to source code (@pxref{Output Styling}).
40490 This will be @samp{on} by default if the GNU Source Highlight library
40491 is available. If the GNU Source Highlight library is not available,
40492 then this will be @samp{off} by default, and attempting to change this
40493 value to @samp{on} will give an error.
40495 If the GNU Source Highlight library is not being used, then
40496 @value{GDBN} will use the Python Pygments package for source code
40497 styling, if it is available.
40499 This option is useful for debugging @value{GDBN}'s use of the Pygments
40500 library when @value{GDBN} is linked against the GNU Source Highlight
40503 @anchor{maint_libopcodes_styling}
40504 @kindex maint set libopcodes-styling enabled
40505 @kindex maint show libopcodes-styling enabled
40506 @item maint set libopcodes-styling enabled @r{[}on|off@r{]}
40507 @itemx maint show libopcodes-styling enabled
40508 Control whether @value{GDBN} should use its builtin disassembler
40509 (@file{libopcodes}) to style disassembler output (@pxref{Output
40510 Styling}). The builtin disassembler does not support styling for all
40513 When this option is @samp{off} the builtin disassembler will not be
40514 used for styling, @value{GDBN} will fall back to using the Python
40515 Pygments package if possible.
40517 Trying to set this option @samp{on} for an architecture that the
40518 builtin disassembler is unable to style will give an error, otherwise,
40519 the builtin disassembler will be used to style disassembler output.
40521 This option is @samp{on} by default for supported architectures.
40523 This option is useful for debugging @value{GDBN}'s use of the Pygments
40524 library when @value{GDBN} is built for an architecture that supports
40525 styling with the builtin disassembler
40526 @kindex maint space
40527 @cindex memory used by commands
40528 @item maint space @var{value}
40529 An alias for @code{maint set per-command space}.
40530 A non-zero value enables it, zero disables it.
40533 @cindex time of command execution
40534 @item maint time @var{value}
40535 An alias for @code{maint set per-command time}.
40536 A non-zero value enables it, zero disables it.
40538 @kindex maint translate-address
40539 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40540 Find the symbol stored at the location specified by the address
40541 @var{addr} and an optional section name @var{section}. If found,
40542 @value{GDBN} prints the name of the closest symbol and an offset from
40543 the symbol's location to the specified address. This is similar to
40544 the @code{info address} command (@pxref{Symbols}), except that this
40545 command also allows to find symbols in other sections.
40547 If section was not specified, the section in which the symbol was found
40548 is also printed. For dynamically linked executables, the name of
40549 executable or shared library containing the symbol is printed as well.
40551 @kindex maint test-options
40552 @item maint test-options require-delimiter
40553 @itemx maint test-options unknown-is-error
40554 @itemx maint test-options unknown-is-operand
40555 These commands are used by the testsuite to validate the command
40556 options framework. The @code{require-delimiter} variant requires a
40557 double-dash delimiter to indicate end of options. The
40558 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40559 @code{unknown-is-error} variant throws an error on unknown option,
40560 while @code{unknown-is-operand} treats unknown options as the start of
40561 the command's operands. When run, the commands output the result of
40562 the processed options. When completed, the commands store the
40563 internal result of completion in a variable exposed by the @code{maint
40564 show test-options-completion-result} command.
40566 @kindex maint show test-options-completion-result
40567 @item maint show test-options-completion-result
40568 Shows the result of completing the @code{maint test-options}
40569 subcommands. This is used by the testsuite to validate completion
40570 support in the command options framework.
40572 @kindex maint set test-settings
40573 @kindex maint show test-settings
40574 @item maint set test-settings @var{kind}
40575 @itemx maint show test-settings @var{kind}
40576 These are representative commands for each @var{kind} of setting type
40577 @value{GDBN} supports. They are used by the testsuite for exercising
40578 the settings infrastructure.
40580 @kindex maint set backtrace-on-fatal-signal
40581 @kindex maint show backtrace-on-fatal-signal
40582 @item maint set backtrace-on-fatal-signal [on|off]
40583 @itemx maint show backtrace-on-fatal-signal
40584 When this setting is @code{on}, if @value{GDBN} itself terminates with
40585 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40586 printed to the standard error stream. This backtrace can be used to
40587 help diagnose crashes within @value{GDBN} in situations where a user
40588 is unable to share a corefile with the @value{GDBN} developers.
40590 If the functionality to provide this backtrace is not available for
40591 the platform on which GDB is running then this feature will be
40592 @code{off} by default, and attempting to turn this feature on will
40595 For platforms that do support creating the backtrace this feature is
40596 @code{on} by default.
40599 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40600 Like the @code{with} command, but works with @code{maintenance set}
40601 variables. This is used by the testsuite to exercise the @code{with}
40602 command's infrastructure.
40606 The following command is useful for non-interactive invocations of
40607 @value{GDBN}, such as in the test suite.
40610 @item set watchdog @var{nsec}
40611 @kindex set watchdog
40612 @cindex watchdog timer
40613 @cindex timeout for commands
40614 Set the maximum number of seconds @value{GDBN} will wait for the
40615 target operation to finish. If this time expires, @value{GDBN}
40616 reports and error and the command is aborted.
40618 @item show watchdog
40619 Show the current setting of the target wait timeout.
40622 @node Remote Protocol
40623 @appendix @value{GDBN} Remote Serial Protocol
40628 * Stop Reply Packets::
40629 * General Query Packets::
40630 * Architecture-Specific Protocol Details::
40631 * Tracepoint Packets::
40632 * Host I/O Packets::
40634 * Notification Packets::
40635 * Remote Non-Stop::
40636 * Packet Acknowledgment::
40638 * File-I/O Remote Protocol Extension::
40639 * Library List Format::
40640 * Library List Format for SVR4 Targets::
40641 * Memory Map Format::
40642 * Thread List Format::
40643 * Traceframe Info Format::
40644 * Branch Trace Format::
40645 * Branch Trace Configuration Format::
40651 There may be occasions when you need to know something about the
40652 protocol---for example, if there is only one serial port to your target
40653 machine, you might want your program to do something special if it
40654 recognizes a packet meant for @value{GDBN}.
40656 In the examples below, @samp{->} and @samp{<-} are used to indicate
40657 transmitted and received data, respectively.
40659 @cindex protocol, @value{GDBN} remote serial
40660 @cindex serial protocol, @value{GDBN} remote
40661 @cindex remote serial protocol
40662 All @value{GDBN} commands and responses (other than acknowledgments
40663 and notifications, see @ref{Notification Packets}) are sent as a
40664 @var{packet}. A @var{packet} is introduced with the character
40665 @samp{$}, the actual @var{packet-data}, and the terminating character
40666 @samp{#} followed by a two-digit @var{checksum}:
40669 @code{$}@var{packet-data}@code{#}@var{checksum}
40673 @cindex checksum, for @value{GDBN} remote
40675 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40676 characters between the leading @samp{$} and the trailing @samp{#} (an
40677 eight bit unsigned checksum).
40679 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40680 specification also included an optional two-digit @var{sequence-id}:
40683 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40686 @cindex sequence-id, for @value{GDBN} remote
40688 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40689 has never output @var{sequence-id}s. Stubs that handle packets added
40690 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40692 When either the host or the target machine receives a packet, the first
40693 response expected is an acknowledgment: either @samp{+} (to indicate
40694 the package was received correctly) or @samp{-} (to request
40698 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40703 The @samp{+}/@samp{-} acknowledgments can be disabled
40704 once a connection is established.
40705 @xref{Packet Acknowledgment}, for details.
40707 The host (@value{GDBN}) sends @var{command}s, and the target (the
40708 debugging stub incorporated in your program) sends a @var{response}. In
40709 the case of step and continue @var{command}s, the response is only sent
40710 when the operation has completed, and the target has again stopped all
40711 threads in all attached processes. This is the default all-stop mode
40712 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40713 execution mode; see @ref{Remote Non-Stop}, for details.
40715 @var{packet-data} consists of a sequence of characters with the
40716 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40719 @cindex remote protocol, field separator
40720 Fields within the packet should be separated using @samp{,} @samp{;} or
40721 @samp{:}. Except where otherwise noted all numbers are represented in
40722 @sc{hex} with leading zeros suppressed.
40724 Implementors should note that prior to @value{GDBN} 5.0, the character
40725 @samp{:} could not appear as the third character in a packet (as it
40726 would potentially conflict with the @var{sequence-id}).
40728 @cindex remote protocol, binary data
40729 @anchor{Binary Data}
40730 Binary data in most packets is encoded either as two hexadecimal
40731 digits per byte of binary data. This allowed the traditional remote
40732 protocol to work over connections which were only seven-bit clean.
40733 Some packets designed more recently assume an eight-bit clean
40734 connection, and use a more efficient encoding to send and receive
40737 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40738 as an escape character. Any escaped byte is transmitted as the escape
40739 character followed by the original character XORed with @code{0x20}.
40740 For example, the byte @code{0x7d} would be transmitted as the two
40741 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40742 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40743 @samp{@}}) must always be escaped. Responses sent by the stub
40744 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40745 is not interpreted as the start of a run-length encoded sequence
40748 Response @var{data} can be run-length encoded to save space.
40749 Run-length encoding replaces runs of identical characters with one
40750 instance of the repeated character, followed by a @samp{*} and a
40751 repeat count. The repeat count is itself sent encoded, to avoid
40752 binary characters in @var{data}: a value of @var{n} is sent as
40753 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40754 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40755 code 32) for a repeat count of 3. (This is because run-length
40756 encoding starts to win for counts 3 or more.) Thus, for example,
40757 @samp{0* } is a run-length encoding of ``0000'': the space character
40758 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40761 The printable characters @samp{#} and @samp{$} or with a numeric value
40762 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40763 seven repeats (@samp{$}) can be expanded using a repeat count of only
40764 five (@samp{"}). For example, @samp{00000000} can be encoded as
40767 The error response returned for some packets includes a two character
40768 error number. That number is not well defined.
40770 @cindex empty response, for unsupported packets
40771 For any @var{command} not supported by the stub, an empty response
40772 (@samp{$#00}) should be returned. That way it is possible to extend the
40773 protocol. A newer @value{GDBN} can tell if a packet is supported based
40776 At a minimum, a stub is required to support the @samp{?} command to
40777 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40778 commands for register access, and the @samp{m} and @samp{M} commands
40779 for memory access. Stubs that only control single-threaded targets
40780 can implement run control with the @samp{c} (continue) command, and if
40781 the target architecture supports hardware-assisted single-stepping,
40782 the @samp{s} (step) command. Stubs that support multi-threading
40783 targets should support the @samp{vCont} command. All other commands
40789 The following table provides a complete list of all currently defined
40790 @var{command}s and their corresponding response @var{data}.
40791 @xref{File-I/O Remote Protocol Extension}, for details about the File
40792 I/O extension of the remote protocol.
40794 Each packet's description has a template showing the packet's overall
40795 syntax, followed by an explanation of the packet's meaning. We
40796 include spaces in some of the templates for clarity; these are not
40797 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40798 separate its components. For example, a template like @samp{foo
40799 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40800 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40801 @var{baz}. @value{GDBN} does not transmit a space character between the
40802 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40805 @cindex @var{thread-id}, in remote protocol
40806 @anchor{thread-id syntax}
40807 Several packets and replies include a @var{thread-id} field to identify
40808 a thread. Normally these are positive numbers with a target-specific
40809 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40810 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40813 In addition, the remote protocol supports a multiprocess feature in
40814 which the @var{thread-id} syntax is extended to optionally include both
40815 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40816 The @var{pid} (process) and @var{tid} (thread) components each have the
40817 format described above: a positive number with target-specific
40818 interpretation formatted as a big-endian hex string, literal @samp{-1}
40819 to indicate all processes or threads (respectively), or @samp{0} to
40820 indicate an arbitrary process or thread. Specifying just a process, as
40821 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40822 error to specify all processes but a specific thread, such as
40823 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40824 for those packets and replies explicitly documented to include a process
40825 ID, rather than a @var{thread-id}.
40827 The multiprocess @var{thread-id} syntax extensions are only used if both
40828 @value{GDBN} and the stub report support for the @samp{multiprocess}
40829 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40832 Note that all packet forms beginning with an upper- or lower-case
40833 letter, other than those described here, are reserved for future use.
40835 Here are the packet descriptions.
40840 @cindex @samp{!} packet
40841 @anchor{extended mode}
40842 Enable extended mode. In extended mode, the remote server is made
40843 persistent. The @samp{R} packet is used to restart the program being
40849 The remote target both supports and has enabled extended mode.
40853 @cindex @samp{?} packet
40855 This is sent when connection is first established to query the reason
40856 the target halted. The reply is the same as for step and continue.
40857 This packet has a special interpretation when the target is in
40858 non-stop mode; see @ref{Remote Non-Stop}.
40861 @xref{Stop Reply Packets}, for the reply specifications.
40863 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40864 @cindex @samp{A} packet
40865 Initialized @code{argv[]} array passed into program. @var{arglen}
40866 specifies the number of bytes in the hex encoded byte stream
40867 @var{arg}. See @code{gdbserver} for more details.
40872 The arguments were set.
40878 @cindex @samp{b} packet
40879 (Don't use this packet; its behavior is not well-defined.)
40880 Change the serial line speed to @var{baud}.
40882 JTC: @emph{When does the transport layer state change? When it's
40883 received, or after the ACK is transmitted. In either case, there are
40884 problems if the command or the acknowledgment packet is dropped.}
40886 Stan: @emph{If people really wanted to add something like this, and get
40887 it working for the first time, they ought to modify ser-unix.c to send
40888 some kind of out-of-band message to a specially-setup stub and have the
40889 switch happen "in between" packets, so that from remote protocol's point
40890 of view, nothing actually happened.}
40892 @item B @var{addr},@var{mode}
40893 @cindex @samp{B} packet
40894 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40895 breakpoint at @var{addr}.
40897 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40898 (@pxref{insert breakpoint or watchpoint packet}).
40900 @cindex @samp{bc} packet
40903 Backward continue. Execute the target system in reverse. No parameter.
40904 @xref{Reverse Execution}, for more information.
40907 @xref{Stop Reply Packets}, for the reply specifications.
40909 @cindex @samp{bs} packet
40912 Backward single step. Execute one instruction in reverse. No parameter.
40913 @xref{Reverse Execution}, for more information.
40916 @xref{Stop Reply Packets}, for the reply specifications.
40918 @item c @r{[}@var{addr}@r{]}
40919 @cindex @samp{c} packet
40920 Continue at @var{addr}, which is the address to resume. If @var{addr}
40921 is omitted, resume at current address.
40923 This packet is deprecated for multi-threading support. @xref{vCont
40927 @xref{Stop Reply Packets}, for the reply specifications.
40929 @item C @var{sig}@r{[};@var{addr}@r{]}
40930 @cindex @samp{C} packet
40931 Continue with signal @var{sig} (hex signal number). If
40932 @samp{;@var{addr}} is omitted, resume at same address.
40934 This packet is deprecated for multi-threading support. @xref{vCont
40938 @xref{Stop Reply Packets}, for the reply specifications.
40941 @cindex @samp{d} packet
40944 Don't use this packet; instead, define a general set packet
40945 (@pxref{General Query Packets}).
40949 @cindex @samp{D} packet
40950 The first form of the packet is used to detach @value{GDBN} from the
40951 remote system. It is sent to the remote target
40952 before @value{GDBN} disconnects via the @code{detach} command.
40954 The second form, including a process ID, is used when multiprocess
40955 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40956 detach only a specific process. The @var{pid} is specified as a
40957 big-endian hex string.
40967 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40968 @cindex @samp{F} packet
40969 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40970 This is part of the File-I/O protocol extension. @xref{File-I/O
40971 Remote Protocol Extension}, for the specification.
40974 @anchor{read registers packet}
40975 @cindex @samp{g} packet
40976 Read general registers.
40980 @item @var{XX@dots{}}
40981 Each byte of register data is described by two hex digits. The bytes
40982 with the register are transmitted in target byte order. The size of
40983 each register and their position within the @samp{g} packet are
40984 determined by the @value{GDBN} internal gdbarch functions
40985 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40987 When reading registers from a trace frame (@pxref{Analyze Collected
40988 Data,,Using the Collected Data}), the stub may also return a string of
40989 literal @samp{x}'s in place of the register data digits, to indicate
40990 that the corresponding register has not been collected, thus its value
40991 is unavailable. For example, for an architecture with 4 registers of
40992 4 bytes each, the following reply indicates to @value{GDBN} that
40993 registers 0 and 2 have not been collected, while registers 1 and 3
40994 have been collected, and both have zero value:
40998 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
41005 @item G @var{XX@dots{}}
41006 @cindex @samp{G} packet
41007 Write general registers. @xref{read registers packet}, for a
41008 description of the @var{XX@dots{}} data.
41018 @item H @var{op} @var{thread-id}
41019 @cindex @samp{H} packet
41020 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
41021 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
41022 should be @samp{c} for step and continue operations (note that this
41023 is deprecated, supporting the @samp{vCont} command is a better
41024 option), and @samp{g} for other operations. The thread designator
41025 @var{thread-id} has the format and interpretation described in
41026 @ref{thread-id syntax}.
41037 @c 'H': How restrictive (or permissive) is the thread model. If a
41038 @c thread is selected and stopped, are other threads allowed
41039 @c to continue to execute? As I mentioned above, I think the
41040 @c semantics of each command when a thread is selected must be
41041 @c described. For example:
41043 @c 'g': If the stub supports threads and a specific thread is
41044 @c selected, returns the register block from that thread;
41045 @c otherwise returns current registers.
41047 @c 'G' If the stub supports threads and a specific thread is
41048 @c selected, sets the registers of the register block of
41049 @c that thread; otherwise sets current registers.
41051 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
41052 @anchor{cycle step packet}
41053 @cindex @samp{i} packet
41054 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
41055 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
41056 step starting at that address.
41059 @cindex @samp{I} packet
41060 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
41064 @cindex @samp{k} packet
41067 The exact effect of this packet is not specified.
41069 For a bare-metal target, it may power cycle or reset the target
41070 system. For that reason, the @samp{k} packet has no reply.
41072 For a single-process target, it may kill that process if possible.
41074 A multiple-process target may choose to kill just one process, or all
41075 that are under @value{GDBN}'s control. For more precise control, use
41076 the vKill packet (@pxref{vKill packet}).
41078 If the target system immediately closes the connection in response to
41079 @samp{k}, @value{GDBN} does not consider the lack of packet
41080 acknowledgment to be an error, and assumes the kill was successful.
41082 If connected using @kbd{target extended-remote}, and the target does
41083 not close the connection in response to a kill request, @value{GDBN}
41084 probes the target state as if a new connection was opened
41085 (@pxref{? packet}).
41087 @item m @var{addr},@var{length}
41088 @cindex @samp{m} packet
41089 Read @var{length} addressable memory units starting at address @var{addr}
41090 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
41091 any particular boundary.
41093 The stub need not use any particular size or alignment when gathering
41094 data from memory for the response; even if @var{addr} is word-aligned
41095 and @var{length} is a multiple of the word size, the stub is free to
41096 use byte accesses, or not. For this reason, this packet may not be
41097 suitable for accessing memory-mapped I/O devices.
41098 @cindex alignment of remote memory accesses
41099 @cindex size of remote memory accesses
41100 @cindex memory, alignment and size of remote accesses
41104 @item @var{XX@dots{}}
41105 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
41106 The reply may contain fewer addressable memory units than requested if the
41107 server was able to read only part of the region of memory.
41112 @item M @var{addr},@var{length}:@var{XX@dots{}}
41113 @cindex @samp{M} packet
41114 Write @var{length} addressable memory units starting at address @var{addr}
41115 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
41116 byte is transmitted as a two-digit hexadecimal number.
41123 for an error (this includes the case where only part of the data was
41128 @cindex @samp{p} packet
41129 Read the value of register @var{n}; @var{n} is in hex.
41130 @xref{read registers packet}, for a description of how the returned
41131 register value is encoded.
41135 @item @var{XX@dots{}}
41136 the register's value
41140 Indicating an unrecognized @var{query}.
41143 @item P @var{n@dots{}}=@var{r@dots{}}
41144 @anchor{write register packet}
41145 @cindex @samp{P} packet
41146 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
41147 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
41148 digits for each byte in the register (target byte order).
41158 @item q @var{name} @var{params}@dots{}
41159 @itemx Q @var{name} @var{params}@dots{}
41160 @cindex @samp{q} packet
41161 @cindex @samp{Q} packet
41162 General query (@samp{q}) and set (@samp{Q}). These packets are
41163 described fully in @ref{General Query Packets}.
41166 @cindex @samp{r} packet
41167 Reset the entire system.
41169 Don't use this packet; use the @samp{R} packet instead.
41172 @cindex @samp{R} packet
41173 Restart the program being debugged. The @var{XX}, while needed, is ignored.
41174 This packet is only available in extended mode (@pxref{extended mode}).
41176 The @samp{R} packet has no reply.
41178 @item s @r{[}@var{addr}@r{]}
41179 @cindex @samp{s} packet
41180 Single step, resuming at @var{addr}. If
41181 @var{addr} is omitted, resume at same address.
41183 This packet is deprecated for multi-threading support. @xref{vCont
41187 @xref{Stop Reply Packets}, for the reply specifications.
41189 @item S @var{sig}@r{[};@var{addr}@r{]}
41190 @anchor{step with signal packet}
41191 @cindex @samp{S} packet
41192 Step with signal. This is analogous to the @samp{C} packet, but
41193 requests a single-step, rather than a normal resumption of execution.
41195 This packet is deprecated for multi-threading support. @xref{vCont
41199 @xref{Stop Reply Packets}, for the reply specifications.
41201 @item t @var{addr}:@var{PP},@var{MM}
41202 @cindex @samp{t} packet
41203 Search backwards starting at address @var{addr} for a match with pattern
41204 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
41205 There must be at least 3 digits in @var{addr}.
41207 @item T @var{thread-id}
41208 @cindex @samp{T} packet
41209 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
41214 thread is still alive
41220 Packets starting with @samp{v} are identified by a multi-letter name,
41221 up to the first @samp{;} or @samp{?} (or the end of the packet).
41223 @item vAttach;@var{pid}
41224 @cindex @samp{vAttach} packet
41225 Attach to a new process with the specified process ID @var{pid}.
41226 The process ID is a
41227 hexadecimal integer identifying the process. In all-stop mode, all
41228 threads in the attached process are stopped; in non-stop mode, it may be
41229 attached without being stopped if that is supported by the target.
41231 @c In non-stop mode, on a successful vAttach, the stub should set the
41232 @c current thread to a thread of the newly-attached process. After
41233 @c attaching, GDB queries for the attached process's thread ID with qC.
41234 @c Also note that, from a user perspective, whether or not the
41235 @c target is stopped on attach in non-stop mode depends on whether you
41236 @c use the foreground or background version of the attach command, not
41237 @c on what vAttach does; GDB does the right thing with respect to either
41238 @c stopping or restarting threads.
41240 This packet is only available in extended mode (@pxref{extended mode}).
41246 @item @r{Any stop packet}
41247 for success in all-stop mode (@pxref{Stop Reply Packets})
41249 for success in non-stop mode (@pxref{Remote Non-Stop})
41252 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
41253 @cindex @samp{vCont} packet
41254 @anchor{vCont packet}
41255 Resume the inferior, specifying different actions for each thread.
41257 For each inferior thread, the leftmost action with a matching
41258 @var{thread-id} is applied. Threads that don't match any action
41259 remain in their current state. Thread IDs are specified using the
41260 syntax described in @ref{thread-id syntax}. If multiprocess
41261 extensions (@pxref{multiprocess extensions}) are supported, actions
41262 can be specified to match all threads in a process by using the
41263 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
41264 @var{thread-id} matches all threads. Specifying no actions is an
41267 Currently supported actions are:
41273 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
41277 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
41280 @item r @var{start},@var{end}
41281 Step once, and then keep stepping as long as the thread stops at
41282 addresses between @var{start} (inclusive) and @var{end} (exclusive).
41283 The remote stub reports a stop reply when either the thread goes out
41284 of the range or is stopped due to an unrelated reason, such as hitting
41285 a breakpoint. @xref{range stepping}.
41287 If the range is empty (@var{start} == @var{end}), then the action
41288 becomes equivalent to the @samp{s} action. In other words,
41289 single-step once, and report the stop (even if the stepped instruction
41290 jumps to @var{start}).
41292 (A stop reply may be sent at any point even if the PC is still within
41293 the stepping range; for example, it is valid to implement this packet
41294 in a degenerate way as a single instruction step operation.)
41298 The optional argument @var{addr} normally associated with the
41299 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
41300 not supported in @samp{vCont}.
41302 The @samp{t} action is only relevant in non-stop mode
41303 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
41304 A stop reply should be generated for any affected thread not already stopped.
41305 When a thread is stopped by means of a @samp{t} action,
41306 the corresponding stop reply should indicate that the thread has stopped with
41307 signal @samp{0}, regardless of whether the target uses some other signal
41308 as an implementation detail.
41310 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
41311 @samp{r} actions for threads that are already running. Conversely,
41312 the server must ignore @samp{t} actions for threads that are already
41315 @emph{Note:} In non-stop mode, a thread is considered running until
41316 @value{GDBN} acknowledges an asynchronous stop notification for it with
41317 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
41319 The stub must support @samp{vCont} if it reports support for
41320 multiprocess extensions (@pxref{multiprocess extensions}).
41323 @xref{Stop Reply Packets}, for the reply specifications.
41326 @cindex @samp{vCont?} packet
41327 Request a list of actions supported by the @samp{vCont} packet.
41331 @item vCont@r{[};@var{action}@dots{}@r{]}
41332 The @samp{vCont} packet is supported. Each @var{action} is a supported
41333 command in the @samp{vCont} packet.
41335 The @samp{vCont} packet is not supported.
41338 @anchor{vCtrlC packet}
41340 @cindex @samp{vCtrlC} packet
41341 Interrupt remote target as if a control-C was pressed on the remote
41342 terminal. This is the equivalent to reacting to the @code{^C}
41343 (@samp{\003}, the control-C character) character in all-stop mode
41344 while the target is running, except this works in non-stop mode.
41345 @xref{interrupting remote targets}, for more info on the all-stop
41356 @item vFile:@var{operation}:@var{parameter}@dots{}
41357 @cindex @samp{vFile} packet
41358 Perform a file operation on the target system. For details,
41359 see @ref{Host I/O Packets}.
41361 @item vFlashErase:@var{addr},@var{length}
41362 @cindex @samp{vFlashErase} packet
41363 Direct the stub to erase @var{length} bytes of flash starting at
41364 @var{addr}. The region may enclose any number of flash blocks, but
41365 its start and end must fall on block boundaries, as indicated by the
41366 flash block size appearing in the memory map (@pxref{Memory Map
41367 Format}). @value{GDBN} groups flash memory programming operations
41368 together, and sends a @samp{vFlashDone} request after each group; the
41369 stub is allowed to delay erase operation until the @samp{vFlashDone}
41370 packet is received.
41380 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41381 @cindex @samp{vFlashWrite} packet
41382 Direct the stub to write data to flash address @var{addr}. The data
41383 is passed in binary form using the same encoding as for the @samp{X}
41384 packet (@pxref{Binary Data}). The memory ranges specified by
41385 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41386 not overlap, and must appear in order of increasing addresses
41387 (although @samp{vFlashErase} packets for higher addresses may already
41388 have been received; the ordering is guaranteed only between
41389 @samp{vFlashWrite} packets). If a packet writes to an address that was
41390 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41391 target-specific method, the results are unpredictable.
41399 for vFlashWrite addressing non-flash memory
41405 @cindex @samp{vFlashDone} packet
41406 Indicate to the stub that flash programming operation is finished.
41407 The stub is permitted to delay or batch the effects of a group of
41408 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41409 @samp{vFlashDone} packet is received. The contents of the affected
41410 regions of flash memory are unpredictable until the @samp{vFlashDone}
41411 request is completed.
41413 @item vKill;@var{pid}
41414 @cindex @samp{vKill} packet
41415 @anchor{vKill packet}
41416 Kill the process with the specified process ID @var{pid}, which is a
41417 hexadecimal integer identifying the process. This packet is used in
41418 preference to @samp{k} when multiprocess protocol extensions are
41419 supported; see @ref{multiprocess extensions}.
41429 @item vMustReplyEmpty
41430 @cindex @samp{vMustReplyEmpty} packet
41431 The correct reply to an unknown @samp{v} packet is to return the empty
41432 string, however, some older versions of @command{gdbserver} would
41433 incorrectly return @samp{OK} for unknown @samp{v} packets.
41435 The @samp{vMustReplyEmpty} is used as a feature test to check how
41436 @command{gdbserver} handles unknown packets, it is important that this
41437 packet be handled in the same way as other unknown @samp{v} packets.
41438 If this packet is handled differently to other unknown @samp{v}
41439 packets then it is possible that @value{GDBN} may run into problems in
41440 other areas, specifically around use of @samp{vFile:setfs:}.
41442 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41443 @cindex @samp{vRun} packet
41444 Run the program @var{filename}, passing it each @var{argument} on its
41445 command line. The file and arguments are hex-encoded strings. If
41446 @var{filename} is an empty string, the stub may use a default program
41447 (e.g.@: the last program run). The program is created in the stopped
41450 @c FIXME: What about non-stop mode?
41452 This packet is only available in extended mode (@pxref{extended mode}).
41458 @item @r{Any stop packet}
41459 for success (@pxref{Stop Reply Packets})
41463 @cindex @samp{vStopped} packet
41464 @xref{Notification Packets}.
41466 @item X @var{addr},@var{length}:@var{XX@dots{}}
41468 @cindex @samp{X} packet
41469 Write data to memory, where the data is transmitted in binary.
41470 Memory is specified by its address @var{addr} and number of addressable memory
41471 units @var{length} (@pxref{addressable memory unit});
41472 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41482 @item z @var{type},@var{addr},@var{kind}
41483 @itemx Z @var{type},@var{addr},@var{kind}
41484 @anchor{insert breakpoint or watchpoint packet}
41485 @cindex @samp{z} packet
41486 @cindex @samp{Z} packets
41487 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41488 watchpoint starting at address @var{address} of kind @var{kind}.
41490 Each breakpoint and watchpoint packet @var{type} is documented
41493 @emph{Implementation notes: A remote target shall return an empty string
41494 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41495 remote target shall support either both or neither of a given
41496 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41497 avoid potential problems with duplicate packets, the operations should
41498 be implemented in an idempotent way.}
41500 @item z0,@var{addr},@var{kind}
41501 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41502 @cindex @samp{z0} packet
41503 @cindex @samp{Z0} packet
41504 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41505 @var{addr} of type @var{kind}.
41507 A software breakpoint is implemented by replacing the instruction at
41508 @var{addr} with a software breakpoint or trap instruction. The
41509 @var{kind} is target-specific and typically indicates the size of the
41510 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41511 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41512 architectures have additional meanings for @var{kind}
41513 (@pxref{Architecture-Specific Protocol Details}); if no
41514 architecture-specific value is being used, it should be @samp{0}.
41515 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41516 conditional expressions in bytecode form that should be evaluated on
41517 the target's side. These are the conditions that should be taken into
41518 consideration when deciding if the breakpoint trigger should be
41519 reported back to @value{GDBN}.
41521 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41522 for how to best report a software breakpoint event to @value{GDBN}.
41524 The @var{cond_list} parameter is comprised of a series of expressions,
41525 concatenated without separators. Each expression has the following form:
41529 @item X @var{len},@var{expr}
41530 @var{len} is the length of the bytecode expression and @var{expr} is the
41531 actual conditional expression in bytecode form.
41535 The optional @var{cmd_list} parameter introduces commands that may be
41536 run on the target, rather than being reported back to @value{GDBN}.
41537 The parameter starts with a numeric flag @var{persist}; if the flag is
41538 nonzero, then the breakpoint may remain active and the commands
41539 continue to be run even when @value{GDBN} disconnects from the target.
41540 Following this flag is a series of expressions concatenated with no
41541 separators. Each expression has the following form:
41545 @item X @var{len},@var{expr}
41546 @var{len} is the length of the bytecode expression and @var{expr} is the
41547 actual commands expression in bytecode form.
41551 @emph{Implementation note: It is possible for a target to copy or move
41552 code that contains software breakpoints (e.g., when implementing
41553 overlays). The behavior of this packet, in the presence of such a
41554 target, is not defined.}
41566 @item z1,@var{addr},@var{kind}
41567 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41568 @cindex @samp{z1} packet
41569 @cindex @samp{Z1} packet
41570 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41571 address @var{addr}.
41573 A hardware breakpoint is implemented using a mechanism that is not
41574 dependent on being able to modify the target's memory. The
41575 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41576 same meaning as in @samp{Z0} packets.
41578 @emph{Implementation note: A hardware breakpoint is not affected by code
41591 @item z2,@var{addr},@var{kind}
41592 @itemx Z2,@var{addr},@var{kind}
41593 @cindex @samp{z2} packet
41594 @cindex @samp{Z2} packet
41595 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41596 The number of bytes to watch is specified by @var{kind}.
41608 @item z3,@var{addr},@var{kind}
41609 @itemx Z3,@var{addr},@var{kind}
41610 @cindex @samp{z3} packet
41611 @cindex @samp{Z3} packet
41612 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41613 The number of bytes to watch is specified by @var{kind}.
41625 @item z4,@var{addr},@var{kind}
41626 @itemx Z4,@var{addr},@var{kind}
41627 @cindex @samp{z4} packet
41628 @cindex @samp{Z4} packet
41629 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41630 The number of bytes to watch is specified by @var{kind}.
41644 @node Stop Reply Packets
41645 @section Stop Reply Packets
41646 @cindex stop reply packets
41648 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41649 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41650 receive any of the below as a reply. Except for @samp{?}
41651 and @samp{vStopped}, that reply is only returned
41652 when the target halts. In the below the exact meaning of @dfn{signal
41653 number} is defined by the header @file{include/gdb/signals.h} in the
41654 @value{GDBN} source code.
41656 In non-stop mode, the server will simply reply @samp{OK} to commands
41657 such as @samp{vCont}; any stop will be the subject of a future
41658 notification. @xref{Remote Non-Stop}.
41660 As in the description of request packets, we include spaces in the
41661 reply templates for clarity; these are not part of the reply packet's
41662 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41668 The program received signal number @var{AA} (a two-digit hexadecimal
41669 number). This is equivalent to a @samp{T} response with no
41670 @var{n}:@var{r} pairs.
41672 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41673 @cindex @samp{T} packet reply
41674 The program received signal number @var{AA} (a two-digit hexadecimal
41675 number). This is equivalent to an @samp{S} response, except that the
41676 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41677 and other information directly in the stop reply packet, reducing
41678 round-trip latency. Single-step and breakpoint traps are reported
41679 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41683 If @var{n} is a hexadecimal number, it is a register number, and the
41684 corresponding @var{r} gives that register's value. The data @var{r} is a
41685 series of bytes in target byte order, with each byte given by a
41686 two-digit hex number.
41689 If @var{n} is @samp{thread}, then @var{r} is the thread ID of
41690 the stopped thread, as specified in @ref{thread-id syntax}.
41693 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41694 the core on which the stop event was detected.
41697 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41698 specific event that stopped the target. The currently defined stop
41699 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41700 signal. At most one stop reason should be present.
41703 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41704 and go on to the next; this allows us to extend the protocol in the
41708 The currently defined stop reasons are:
41714 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41717 @item syscall_entry
41718 @itemx syscall_return
41719 The packet indicates a syscall entry or return, and @var{r} is the
41720 syscall number, in hex.
41722 @cindex shared library events, remote reply
41724 The packet indicates that the loaded libraries have changed.
41725 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41726 list of loaded libraries. The @var{r} part is ignored.
41728 @cindex replay log events, remote reply
41730 The packet indicates that the target cannot continue replaying
41731 logged execution events, because it has reached the end (or the
41732 beginning when executing backward) of the log. The value of @var{r}
41733 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41734 for more information.
41737 @anchor{swbreak stop reason}
41738 The packet indicates a software breakpoint instruction was executed,
41739 irrespective of whether it was @value{GDBN} that planted the
41740 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41741 part must be left empty.
41743 On some architectures, such as x86, at the architecture level, when a
41744 breakpoint instruction executes the program counter points at the
41745 breakpoint address plus an offset. On such targets, the stub is
41746 responsible for adjusting the PC to point back at the breakpoint
41749 This packet should not be sent by default; older @value{GDBN} versions
41750 did not support it. @value{GDBN} requests it, by supplying an
41751 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41752 remote stub must also supply the appropriate @samp{qSupported} feature
41753 indicating support.
41755 This packet is required for correct non-stop mode operation.
41758 The packet indicates the target stopped for a hardware breakpoint.
41759 The @var{r} part must be left empty.
41761 The same remarks about @samp{qSupported} and non-stop mode above
41764 @cindex fork events, remote reply
41766 The packet indicates that @code{fork} was called, and @var{r} is the
41767 thread ID of the new child process, as specified in @ref{thread-id
41768 syntax}. This packet is only applicable to targets that support fork
41771 This packet should not be sent by default; older @value{GDBN} versions
41772 did not support it. @value{GDBN} requests it, by supplying an
41773 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41774 remote stub must also supply the appropriate @samp{qSupported} feature
41775 indicating support.
41777 @cindex vfork events, remote reply
41779 The packet indicates that @code{vfork} was called, and @var{r} is the
41780 thread ID of the new child process, as specified in @ref{thread-id
41781 syntax}. This packet is only applicable to targets that support vfork
41784 This packet should not be sent by default; older @value{GDBN} versions
41785 did not support it. @value{GDBN} requests it, by supplying an
41786 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41787 remote stub must also supply the appropriate @samp{qSupported} feature
41788 indicating support.
41790 @cindex vforkdone events, remote reply
41792 The packet indicates that a child process created by a vfork
41793 has either called @code{exec} or terminated, so that the
41794 address spaces of the parent and child process are no longer
41795 shared. The @var{r} part is ignored. This packet is only
41796 applicable to targets that support vforkdone events.
41798 This packet should not be sent by default; older @value{GDBN} versions
41799 did not support it. @value{GDBN} requests it, by supplying an
41800 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41801 remote stub must also supply the appropriate @samp{qSupported} feature
41802 indicating support.
41804 @cindex exec events, remote reply
41806 The packet indicates that @code{execve} was called, and @var{r}
41807 is the absolute pathname of the file that was executed, in hex.
41808 This packet is only applicable to targets that support exec events.
41810 This packet should not be sent by default; older @value{GDBN} versions
41811 did not support it. @value{GDBN} requests it, by supplying an
41812 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41813 remote stub must also supply the appropriate @samp{qSupported} feature
41814 indicating support.
41816 @cindex thread create event, remote reply
41817 @anchor{thread create event}
41819 The packet indicates that the thread was just created. The new thread
41820 is stopped until @value{GDBN} sets it running with a resumption packet
41821 (@pxref{vCont packet}). This packet should not be sent by default;
41822 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41823 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41824 @var{r} part is ignored.
41829 @itemx W @var{AA} ; process:@var{pid}
41830 The process exited, and @var{AA} is the exit status. This is only
41831 applicable to certain targets.
41833 The second form of the response, including the process ID of the
41834 exited process, can be used only when @value{GDBN} has reported
41835 support for multiprocess protocol extensions; see @ref{multiprocess
41836 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41840 @itemx X @var{AA} ; process:@var{pid}
41841 The process terminated with signal @var{AA}.
41843 The second form of the response, including the process ID of the
41844 terminated process, can be used only when @value{GDBN} has reported
41845 support for multiprocess protocol extensions; see @ref{multiprocess
41846 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41849 @anchor{thread exit event}
41850 @cindex thread exit event, remote reply
41851 @item w @var{AA} ; @var{tid}
41853 The thread exited, and @var{AA} is the exit status. This response
41854 should not be sent by default; @value{GDBN} requests it with the
41855 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41856 @var{AA} is formatted as a big-endian hex string.
41859 There are no resumed threads left in the target. In other words, even
41860 though the process is alive, the last resumed thread has exited. For
41861 example, say the target process has two threads: thread 1 and thread
41862 2. The client leaves thread 1 stopped, and resumes thread 2, which
41863 subsequently exits. At this point, even though the process is still
41864 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41865 executing either. The @samp{N} stop reply thus informs the client
41866 that it can stop waiting for stop replies. This packet should not be
41867 sent by default; older @value{GDBN} versions did not support it.
41868 @value{GDBN} requests it, by supplying an appropriate
41869 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41870 also supply the appropriate @samp{qSupported} feature indicating
41873 @item O @var{XX}@dots{}
41874 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41875 written as the program's console output. This can happen at any time
41876 while the program is running and the debugger should continue to wait
41877 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41879 @item F @var{call-id},@var{parameter}@dots{}
41880 @var{call-id} is the identifier which says which host system call should
41881 be called. This is just the name of the function. Translation into the
41882 correct system call is only applicable as it's defined in @value{GDBN}.
41883 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41886 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41887 this very system call.
41889 The target replies with this packet when it expects @value{GDBN} to
41890 call a host system call on behalf of the target. @value{GDBN} replies
41891 with an appropriate @samp{F} packet and keeps up waiting for the next
41892 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41893 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41894 Protocol Extension}, for more details.
41898 @node General Query Packets
41899 @section General Query Packets
41900 @cindex remote query requests
41902 Packets starting with @samp{q} are @dfn{general query packets};
41903 packets starting with @samp{Q} are @dfn{general set packets}. General
41904 query and set packets are a semi-unified form for retrieving and
41905 sending information to and from the stub.
41907 The initial letter of a query or set packet is followed by a name
41908 indicating what sort of thing the packet applies to. For example,
41909 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41910 definitions with the stub. These packet names follow some
41915 The name must not contain commas, colons or semicolons.
41917 Most @value{GDBN} query and set packets have a leading upper case
41920 The names of custom vendor packets should use a company prefix, in
41921 lower case, followed by a period. For example, packets designed at
41922 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41923 foos) or @samp{Qacme.bar} (for setting bars).
41926 The name of a query or set packet should be separated from any
41927 parameters by a @samp{:}; the parameters themselves should be
41928 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41929 full packet name, and check for a separator or the end of the packet,
41930 in case two packet names share a common prefix. New packets should not begin
41931 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41932 packets predate these conventions, and have arguments without any terminator
41933 for the packet name; we suspect they are in widespread use in places that
41934 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41935 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41938 Like the descriptions of the other packets, each description here
41939 has a template showing the packet's overall syntax, followed by an
41940 explanation of the packet's meaning. We include spaces in some of the
41941 templates for clarity; these are not part of the packet's syntax. No
41942 @value{GDBN} packet uses spaces to separate its components.
41944 Here are the currently defined query and set packets:
41950 Turn on or off the agent as a helper to perform some debugging operations
41951 delegated from @value{GDBN} (@pxref{Control Agent}).
41953 @item QAllow:@var{op}:@var{val}@dots{}
41954 @cindex @samp{QAllow} packet
41955 Specify which operations @value{GDBN} expects to request of the
41956 target, as a semicolon-separated list of operation name and value
41957 pairs. Possible values for @var{op} include @samp{WriteReg},
41958 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41959 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41960 indicating that @value{GDBN} will not request the operation, or 1,
41961 indicating that it may. (The target can then use this to set up its
41962 own internals optimally, for instance if the debugger never expects to
41963 insert breakpoints, it may not need to install its own trap handler.)
41966 @cindex current thread, remote request
41967 @cindex @samp{qC} packet
41968 Return the current thread ID.
41972 @item QC @var{thread-id}
41973 Where @var{thread-id} is a thread ID as documented in
41974 @ref{thread-id syntax}.
41975 @item @r{(anything else)}
41976 Any other reply implies the old thread ID.
41979 @item qCRC:@var{addr},@var{length}
41980 @cindex CRC of memory block, remote request
41981 @cindex @samp{qCRC} packet
41982 @anchor{qCRC packet}
41983 Compute the CRC checksum of a block of memory using CRC-32 defined in
41984 IEEE 802.3. The CRC is computed byte at a time, taking the most
41985 significant bit of each byte first. The initial pattern code
41986 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41988 @emph{Note:} This is the same CRC used in validating separate debug
41989 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41990 Files}). However the algorithm is slightly different. When validating
41991 separate debug files, the CRC is computed taking the @emph{least}
41992 significant bit of each byte first, and the final result is inverted to
41993 detect trailing zeros.
41998 An error (such as memory fault)
41999 @item C @var{crc32}
42000 The specified memory region's checksum is @var{crc32}.
42003 @item QDisableRandomization:@var{value}
42004 @cindex disable address space randomization, remote request
42005 @cindex @samp{QDisableRandomization} packet
42006 Some target operating systems will randomize the virtual address space
42007 of the inferior process as a security feature, but provide a feature
42008 to disable such randomization, e.g.@: to allow for a more deterministic
42009 debugging experience. On such systems, this packet with a @var{value}
42010 of 1 directs the target to disable address space randomization for
42011 processes subsequently started via @samp{vRun} packets, while a packet
42012 with a @var{value} of 0 tells the target to enable address space
42015 This packet is only available in extended mode (@pxref{extended mode}).
42020 The request succeeded.
42023 An error occurred. The error number @var{nn} is given as hex digits.
42026 An empty reply indicates that @samp{QDisableRandomization} is not supported
42030 This packet is not probed by default; the remote stub must request it,
42031 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42032 This should only be done on targets that actually support disabling
42033 address space randomization.
42035 @item QStartupWithShell:@var{value}
42036 @cindex startup with shell, remote request
42037 @cindex @samp{QStartupWithShell} packet
42038 On UNIX-like targets, it is possible to start the inferior using a
42039 shell program. This is the default behavior on both @value{GDBN} and
42040 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
42041 used to inform @command{gdbserver} whether it should start the
42042 inferior using a shell or not.
42044 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
42045 to start the inferior. If @var{value} is @samp{1},
42046 @command{gdbserver} will use a shell to start the inferior. All other
42047 values are considered an error.
42049 This packet is only available in extended mode (@pxref{extended
42055 The request succeeded.
42058 An error occurred. The error number @var{nn} is given as hex digits.
42061 This packet is not probed by default; the remote stub must request it,
42062 by supplying an appropriate @samp{qSupported} response
42063 (@pxref{qSupported}). This should only be done on targets that
42064 actually support starting the inferior using a shell.
42066 Use of this packet is controlled by the @code{set startup-with-shell}
42067 command; @pxref{set startup-with-shell}.
42069 @item QEnvironmentHexEncoded:@var{hex-value}
42070 @anchor{QEnvironmentHexEncoded}
42071 @cindex set environment variable, remote request
42072 @cindex @samp{QEnvironmentHexEncoded} packet
42073 On UNIX-like targets, it is possible to set environment variables that
42074 will be passed to the inferior during the startup process. This
42075 packet is used to inform @command{gdbserver} of an environment
42076 variable that has been defined by the user on @value{GDBN} (@pxref{set
42079 The packet is composed by @var{hex-value}, an hex encoded
42080 representation of the @var{name=value} format representing an
42081 environment variable. The name of the environment variable is
42082 represented by @var{name}, and the value to be assigned to the
42083 environment variable is represented by @var{value}. If the variable
42084 has no value (i.e., the value is @code{null}), then @var{value} will
42087 This packet is only available in extended mode (@pxref{extended
42093 The request succeeded.
42096 This packet is not probed by default; the remote stub must request it,
42097 by supplying an appropriate @samp{qSupported} response
42098 (@pxref{qSupported}). This should only be done on targets that
42099 actually support passing environment variables to the starting
42102 This packet is related to the @code{set environment} command;
42103 @pxref{set environment}.
42105 @item QEnvironmentUnset:@var{hex-value}
42106 @anchor{QEnvironmentUnset}
42107 @cindex unset environment variable, remote request
42108 @cindex @samp{QEnvironmentUnset} packet
42109 On UNIX-like targets, it is possible to unset environment variables
42110 before starting the inferior in the remote target. This packet is
42111 used to inform @command{gdbserver} of an environment variable that has
42112 been unset by the user on @value{GDBN} (@pxref{unset environment}).
42114 The packet is composed by @var{hex-value}, an hex encoded
42115 representation of the name of the environment variable to be unset.
42117 This packet is only available in extended mode (@pxref{extended
42123 The request succeeded.
42126 This packet is not probed by default; the remote stub must request it,
42127 by supplying an appropriate @samp{qSupported} response
42128 (@pxref{qSupported}). This should only be done on targets that
42129 actually support passing environment variables to the starting
42132 This packet is related to the @code{unset environment} command;
42133 @pxref{unset environment}.
42135 @item QEnvironmentReset
42136 @anchor{QEnvironmentReset}
42137 @cindex reset environment, remote request
42138 @cindex @samp{QEnvironmentReset} packet
42139 On UNIX-like targets, this packet is used to reset the state of
42140 environment variables in the remote target before starting the
42141 inferior. In this context, reset means unsetting all environment
42142 variables that were previously set by the user (i.e., were not
42143 initially present in the environment). It is sent to
42144 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
42145 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
42146 (@pxref{QEnvironmentUnset}) packets.
42148 This packet is only available in extended mode (@pxref{extended
42154 The request succeeded.
42157 This packet is not probed by default; the remote stub must request it,
42158 by supplying an appropriate @samp{qSupported} response
42159 (@pxref{qSupported}). This should only be done on targets that
42160 actually support passing environment variables to the starting
42163 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
42164 @anchor{QSetWorkingDir packet}
42165 @cindex set working directory, remote request
42166 @cindex @samp{QSetWorkingDir} packet
42167 This packet is used to inform the remote server of the intended
42168 current working directory for programs that are going to be executed.
42170 The packet is composed by @var{directory}, an hex encoded
42171 representation of the directory that the remote inferior will use as
42172 its current working directory. If @var{directory} is an empty string,
42173 the remote server should reset the inferior's current working
42174 directory to its original, empty value.
42176 This packet is only available in extended mode (@pxref{extended
42182 The request succeeded.
42186 @itemx qsThreadInfo
42187 @cindex list active threads, remote request
42188 @cindex @samp{qfThreadInfo} packet
42189 @cindex @samp{qsThreadInfo} packet
42190 Obtain a list of all active thread IDs from the target (OS). Since there
42191 may be too many active threads to fit into one reply packet, this query
42192 works iteratively: it may require more than one query/reply sequence to
42193 obtain the entire list of threads. The first query of the sequence will
42194 be the @samp{qfThreadInfo} query; subsequent queries in the
42195 sequence will be the @samp{qsThreadInfo} query.
42197 NOTE: This packet replaces the @samp{qL} query (see below).
42201 @item m @var{thread-id}
42203 @item m @var{thread-id},@var{thread-id}@dots{}
42204 a comma-separated list of thread IDs
42206 (lower case letter @samp{L}) denotes end of list.
42209 In response to each query, the target will reply with a list of one or
42210 more thread IDs, separated by commas.
42211 @value{GDBN} will respond to each reply with a request for more thread
42212 ids (using the @samp{qs} form of the query), until the target responds
42213 with @samp{l} (lower-case ell, for @dfn{last}).
42214 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
42217 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
42218 initial connection with the remote target, and the very first thread ID
42219 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
42220 message. Therefore, the stub should ensure that the first thread ID in
42221 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
42223 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
42224 @cindex get thread-local storage address, remote request
42225 @cindex @samp{qGetTLSAddr} packet
42226 Fetch the address associated with thread local storage specified
42227 by @var{thread-id}, @var{offset}, and @var{lm}.
42229 @var{thread-id} is the thread ID associated with the
42230 thread for which to fetch the TLS address. @xref{thread-id syntax}.
42232 @var{offset} is the (big endian, hex encoded) offset associated with the
42233 thread local variable. (This offset is obtained from the debug
42234 information associated with the variable.)
42236 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
42237 load module associated with the thread local storage. For example,
42238 a @sc{gnu}/Linux system will pass the link map address of the shared
42239 object associated with the thread local storage under consideration.
42240 Other operating environments may choose to represent the load module
42241 differently, so the precise meaning of this parameter will vary.
42245 @item @var{XX}@dots{}
42246 Hex encoded (big endian) bytes representing the address of the thread
42247 local storage requested.
42250 An error occurred. The error number @var{nn} is given as hex digits.
42253 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
42256 @item qGetTIBAddr:@var{thread-id}
42257 @cindex get thread information block address
42258 @cindex @samp{qGetTIBAddr} packet
42259 Fetch address of the Windows OS specific Thread Information Block.
42261 @var{thread-id} is the thread ID associated with the thread.
42265 @item @var{XX}@dots{}
42266 Hex encoded (big endian) bytes representing the linear address of the
42267 thread information block.
42270 An error occured. This means that either the thread was not found, or the
42271 address could not be retrieved.
42274 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
42277 @item qL @var{startflag} @var{threadcount} @var{nextthread}
42278 Obtain thread information from RTOS. Where: @var{startflag} (one hex
42279 digit) is one to indicate the first query and zero to indicate a
42280 subsequent query; @var{threadcount} (two hex digits) is the maximum
42281 number of threads the response packet can contain; and @var{nextthread}
42282 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
42283 returned in the response as @var{argthread}.
42285 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
42289 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
42290 Where: @var{count} (two hex digits) is the number of threads being
42291 returned; @var{done} (one hex digit) is zero to indicate more threads
42292 and one indicates no further threads; @var{argthreadid} (eight hex
42293 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
42294 is a sequence of thread IDs, @var{threadid} (eight hex
42295 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
42298 @item qMemTags:@var{start address},@var{length}:@var{type}
42300 @cindex fetch memory tags
42301 @cindex @samp{qMemTags} packet
42302 Fetch memory tags of type @var{type} from the address range
42303 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42304 target is responsible for calculating how many tags will be returned, as this
42305 is architecture-specific.
42307 @var{start address} is the starting address of the memory range.
42309 @var{length} is the length, in bytes, of the memory range.
42311 @var{type} is the type of tag the request wants to fetch. The type is a signed
42316 @item @var{mxx}@dots{}
42317 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
42318 tags found in the requested memory range.
42321 An error occured. This means that fetching of memory tags failed for some
42325 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
42326 although this should not happen given @value{GDBN} will only send this packet
42327 if the stub has advertised support for memory tagging via @samp{qSupported}.
42330 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
42332 @cindex store memory tags
42333 @cindex @samp{QMemTags} packet
42334 Store memory tags of type @var{type} to the address range
42335 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42336 target is responsible for interpreting the type, the tag bytes and modifying
42337 the memory tag granules accordingly, given this is architecture-specific.
42339 The interpretation of how many tags (@var{nt}) should be written to how many
42340 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
42341 implementation-specific, but the following is suggested.
42343 If the number of memory tags, @var{nt}, is greater than or equal to the
42344 number of memory tag granules, @var{ng}, only @var{ng} tags will be
42347 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
42348 and the tag bytes will be used as a pattern that will get repeated until
42349 @var{ng} tags are stored.
42351 @var{start address} is the starting address of the memory range. The address
42352 does not have any restriction on alignment or size.
42354 @var{length} is the length, in bytes, of the memory range.
42356 @var{type} is the type of tag the request wants to fetch. The type is a signed
42359 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
42360 interpreted by the target. Each pair of hex digits is interpreted as a
42366 The request was successful and the memory tag granules were modified
42370 An error occured. This means that modifying the memory tag granules failed
42374 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42375 although this should not happen given @value{GDBN} will only send this packet
42376 if the stub has advertised support for memory tagging via @samp{qSupported}.
42380 @cindex section offsets, remote request
42381 @cindex @samp{qOffsets} packet
42382 Get section offsets that the target used when relocating the downloaded
42387 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42388 Relocate the @code{Text} section by @var{xxx} from its original address.
42389 Relocate the @code{Data} section by @var{yyy} from its original address.
42390 If the object file format provides segment information (e.g.@: @sc{elf}
42391 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42392 segments by the supplied offsets.
42394 @emph{Note: while a @code{Bss} offset may be included in the response,
42395 @value{GDBN} ignores this and instead applies the @code{Data} offset
42396 to the @code{Bss} section.}
42398 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42399 Relocate the first segment of the object file, which conventionally
42400 contains program code, to a starting address of @var{xxx}. If
42401 @samp{DataSeg} is specified, relocate the second segment, which
42402 conventionally contains modifiable data, to a starting address of
42403 @var{yyy}. @value{GDBN} will report an error if the object file
42404 does not contain segment information, or does not contain at least
42405 as many segments as mentioned in the reply. Extra segments are
42406 kept at fixed offsets relative to the last relocated segment.
42409 @item qP @var{mode} @var{thread-id}
42410 @cindex thread information, remote request
42411 @cindex @samp{qP} packet
42412 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42413 encoded 32 bit mode; @var{thread-id} is a thread ID
42414 (@pxref{thread-id syntax}).
42416 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42419 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42423 @cindex non-stop mode, remote request
42424 @cindex @samp{QNonStop} packet
42426 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42427 @xref{Remote Non-Stop}, for more information.
42432 The request succeeded.
42435 An error occurred. The error number @var{nn} is given as hex digits.
42438 An empty reply indicates that @samp{QNonStop} is not supported by
42442 This packet is not probed by default; the remote stub must request it,
42443 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42444 Use of this packet is controlled by the @code{set non-stop} command;
42445 @pxref{Non-Stop Mode}.
42447 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42448 @itemx QCatchSyscalls:0
42449 @cindex catch syscalls from inferior, remote request
42450 @cindex @samp{QCatchSyscalls} packet
42451 @anchor{QCatchSyscalls}
42452 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42453 catching syscalls from the inferior process.
42455 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42456 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42457 is listed, every system call should be reported.
42459 Note that if a syscall not in the list is reported, @value{GDBN} will
42460 still filter the event according to its own list from all corresponding
42461 @code{catch syscall} commands. However, it is more efficient to only
42462 report the requested syscalls.
42464 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42465 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42467 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42468 kept for the new process too. On targets where exec may affect syscall
42469 numbers, for example with exec between 32 and 64-bit processes, the
42470 client should send a new packet with the new syscall list.
42475 The request succeeded.
42478 An error occurred. @var{nn} are hex digits.
42481 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42485 Use of this packet is controlled by the @code{set remote catch-syscalls}
42486 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42487 This packet is not probed by default; the remote stub must request it,
42488 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42490 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42491 @cindex pass signals to inferior, remote request
42492 @cindex @samp{QPassSignals} packet
42493 @anchor{QPassSignals}
42494 Each listed @var{signal} should be passed directly to the inferior process.
42495 Signals are numbered identically to continue packets and stop replies
42496 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42497 strictly greater than the previous item. These signals do not need to stop
42498 the inferior, or be reported to @value{GDBN}. All other signals should be
42499 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42500 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42501 new list. This packet improves performance when using @samp{handle
42502 @var{signal} nostop noprint pass}.
42507 The request succeeded.
42510 An error occurred. The error number @var{nn} is given as hex digits.
42513 An empty reply indicates that @samp{QPassSignals} is not supported by
42517 Use of this packet is controlled by the @code{set remote pass-signals}
42518 command (@pxref{Remote Configuration, set remote pass-signals}).
42519 This packet is not probed by default; the remote stub must request it,
42520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42522 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42523 @cindex signals the inferior may see, remote request
42524 @cindex @samp{QProgramSignals} packet
42525 @anchor{QProgramSignals}
42526 Each listed @var{signal} may be delivered to the inferior process.
42527 Others should be silently discarded.
42529 In some cases, the remote stub may need to decide whether to deliver a
42530 signal to the program or not without @value{GDBN} involvement. One
42531 example of that is while detaching --- the program's threads may have
42532 stopped for signals that haven't yet had a chance of being reported to
42533 @value{GDBN}, and so the remote stub can use the signal list specified
42534 by this packet to know whether to deliver or ignore those pending
42537 This does not influence whether to deliver a signal as requested by a
42538 resumption packet (@pxref{vCont packet}).
42540 Signals are numbered identically to continue packets and stop replies
42541 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42542 strictly greater than the previous item. Multiple
42543 @samp{QProgramSignals} packets do not combine; any earlier
42544 @samp{QProgramSignals} list is completely replaced by the new list.
42549 The request succeeded.
42552 An error occurred. The error number @var{nn} is given as hex digits.
42555 An empty reply indicates that @samp{QProgramSignals} is not supported
42559 Use of this packet is controlled by the @code{set remote program-signals}
42560 command (@pxref{Remote Configuration, set remote program-signals}).
42561 This packet is not probed by default; the remote stub must request it,
42562 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42564 @anchor{QThreadEvents}
42565 @item QThreadEvents:1
42566 @itemx QThreadEvents:0
42567 @cindex thread create/exit events, remote request
42568 @cindex @samp{QThreadEvents} packet
42570 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42571 reporting of thread create and exit events. @xref{thread create
42572 event}, for the reply specifications. For example, this is used in
42573 non-stop mode when @value{GDBN} stops a set of threads and
42574 synchronously waits for the their corresponding stop replies. Without
42575 exit events, if one of the threads exits, @value{GDBN} would hang
42576 forever not knowing that it should no longer expect a stop for that
42577 same thread. @value{GDBN} does not enable this feature unless the
42578 stub reports that it supports it by including @samp{QThreadEvents+} in
42579 its @samp{qSupported} reply.
42584 The request succeeded.
42587 An error occurred. The error number @var{nn} is given as hex digits.
42590 An empty reply indicates that @samp{QThreadEvents} is not supported by
42594 Use of this packet is controlled by the @code{set remote thread-events}
42595 command (@pxref{Remote Configuration, set remote thread-events}).
42597 @item qRcmd,@var{command}
42598 @cindex execute remote command, remote request
42599 @cindex @samp{qRcmd} packet
42600 @var{command} (hex encoded) is passed to the local interpreter for
42601 execution. Invalid commands should be reported using the output
42602 string. Before the final result packet, the target may also respond
42603 with a number of intermediate @samp{O@var{output}} console output
42604 packets. @emph{Implementors should note that providing access to a
42605 stubs's interpreter may have security implications}.
42610 A command response with no output.
42612 A command response with the hex encoded output string @var{OUTPUT}.
42614 Indicate a badly formed request. The error number @var{NN} is given as
42617 An empty reply indicates that @samp{qRcmd} is not recognized.
42620 (Note that the @code{qRcmd} packet's name is separated from the
42621 command by a @samp{,}, not a @samp{:}, contrary to the naming
42622 conventions above. Please don't use this packet as a model for new
42625 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42626 @cindex searching memory, in remote debugging
42628 @cindex @samp{qSearch:memory} packet
42630 @cindex @samp{qSearch memory} packet
42631 @anchor{qSearch memory}
42632 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42633 Both @var{address} and @var{length} are encoded in hex;
42634 @var{search-pattern} is a sequence of bytes, also hex encoded.
42639 The pattern was not found.
42641 The pattern was found at @var{address}.
42643 A badly formed request or an error was encountered while searching memory.
42645 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42648 @item QStartNoAckMode
42649 @cindex @samp{QStartNoAckMode} packet
42650 @anchor{QStartNoAckMode}
42651 Request that the remote stub disable the normal @samp{+}/@samp{-}
42652 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42657 The stub has switched to no-acknowledgment mode.
42658 @value{GDBN} acknowledges this response,
42659 but neither the stub nor @value{GDBN} shall send or expect further
42660 @samp{+}/@samp{-} acknowledgments in the current connection.
42662 An empty reply indicates that the stub does not support no-acknowledgment mode.
42665 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42666 @cindex supported packets, remote query
42667 @cindex features of the remote protocol
42668 @cindex @samp{qSupported} packet
42669 @anchor{qSupported}
42670 Tell the remote stub about features supported by @value{GDBN}, and
42671 query the stub for features it supports. This packet allows
42672 @value{GDBN} and the remote stub to take advantage of each others'
42673 features. @samp{qSupported} also consolidates multiple feature probes
42674 at startup, to improve @value{GDBN} performance---a single larger
42675 packet performs better than multiple smaller probe packets on
42676 high-latency links. Some features may enable behavior which must not
42677 be on by default, e.g.@: because it would confuse older clients or
42678 stubs. Other features may describe packets which could be
42679 automatically probed for, but are not. These features must be
42680 reported before @value{GDBN} will use them. This ``default
42681 unsupported'' behavior is not appropriate for all packets, but it
42682 helps to keep the initial connection time under control with new
42683 versions of @value{GDBN} which support increasing numbers of packets.
42687 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42688 The stub supports or does not support each returned @var{stubfeature},
42689 depending on the form of each @var{stubfeature} (see below for the
42692 An empty reply indicates that @samp{qSupported} is not recognized,
42693 or that no features needed to be reported to @value{GDBN}.
42696 The allowed forms for each feature (either a @var{gdbfeature} in the
42697 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42701 @item @var{name}=@var{value}
42702 The remote protocol feature @var{name} is supported, and associated
42703 with the specified @var{value}. The format of @var{value} depends
42704 on the feature, but it must not include a semicolon.
42706 The remote protocol feature @var{name} is supported, and does not
42707 need an associated value.
42709 The remote protocol feature @var{name} is not supported.
42711 The remote protocol feature @var{name} may be supported, and
42712 @value{GDBN} should auto-detect support in some other way when it is
42713 needed. This form will not be used for @var{gdbfeature} notifications,
42714 but may be used for @var{stubfeature} responses.
42717 Whenever the stub receives a @samp{qSupported} request, the
42718 supplied set of @value{GDBN} features should override any previous
42719 request. This allows @value{GDBN} to put the stub in a known
42720 state, even if the stub had previously been communicating with
42721 a different version of @value{GDBN}.
42723 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42728 This feature indicates whether @value{GDBN} supports multiprocess
42729 extensions to the remote protocol. @value{GDBN} does not use such
42730 extensions unless the stub also reports that it supports them by
42731 including @samp{multiprocess+} in its @samp{qSupported} reply.
42732 @xref{multiprocess extensions}, for details.
42735 This feature indicates that @value{GDBN} supports the XML target
42736 description. If the stub sees @samp{xmlRegisters=} with target
42737 specific strings separated by a comma, it will report register
42741 This feature indicates whether @value{GDBN} supports the
42742 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42743 instruction reply packet}).
42746 This feature indicates whether @value{GDBN} supports the swbreak stop
42747 reason in stop replies. @xref{swbreak stop reason}, for details.
42750 This feature indicates whether @value{GDBN} supports the hwbreak stop
42751 reason in stop replies. @xref{swbreak stop reason}, for details.
42754 This feature indicates whether @value{GDBN} supports fork event
42755 extensions to the remote protocol. @value{GDBN} does not use such
42756 extensions unless the stub also reports that it supports them by
42757 including @samp{fork-events+} in its @samp{qSupported} reply.
42760 This feature indicates whether @value{GDBN} supports vfork event
42761 extensions to the remote protocol. @value{GDBN} does not use such
42762 extensions unless the stub also reports that it supports them by
42763 including @samp{vfork-events+} in its @samp{qSupported} reply.
42766 This feature indicates whether @value{GDBN} supports exec event
42767 extensions to the remote protocol. @value{GDBN} does not use such
42768 extensions unless the stub also reports that it supports them by
42769 including @samp{exec-events+} in its @samp{qSupported} reply.
42771 @item vContSupported
42772 This feature indicates whether @value{GDBN} wants to know the
42773 supported actions in the reply to @samp{vCont?} packet.
42776 Stubs should ignore any unknown values for
42777 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42778 packet supports receiving packets of unlimited length (earlier
42779 versions of @value{GDBN} may reject overly long responses). Additional values
42780 for @var{gdbfeature} may be defined in the future to let the stub take
42781 advantage of new features in @value{GDBN}, e.g.@: incompatible
42782 improvements in the remote protocol---the @samp{multiprocess} feature is
42783 an example of such a feature. The stub's reply should be independent
42784 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42785 describes all the features it supports, and then the stub replies with
42786 all the features it supports.
42788 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42789 responses, as long as each response uses one of the standard forms.
42791 Some features are flags. A stub which supports a flag feature
42792 should respond with a @samp{+} form response. Other features
42793 require values, and the stub should respond with an @samp{=}
42796 Each feature has a default value, which @value{GDBN} will use if
42797 @samp{qSupported} is not available or if the feature is not mentioned
42798 in the @samp{qSupported} response. The default values are fixed; a
42799 stub is free to omit any feature responses that match the defaults.
42801 Not all features can be probed, but for those which can, the probing
42802 mechanism is useful: in some cases, a stub's internal
42803 architecture may not allow the protocol layer to know some information
42804 about the underlying target in advance. This is especially common in
42805 stubs which may be configured for multiple targets.
42807 These are the currently defined stub features and their properties:
42809 @multitable @columnfractions 0.35 0.2 0.12 0.2
42810 @c NOTE: The first row should be @headitem, but we do not yet require
42811 @c a new enough version of Texinfo (4.7) to use @headitem.
42813 @tab Value Required
42817 @item @samp{PacketSize}
42822 @item @samp{qXfer:auxv:read}
42827 @item @samp{qXfer:btrace:read}
42832 @item @samp{qXfer:btrace-conf:read}
42837 @item @samp{qXfer:exec-file:read}
42842 @item @samp{qXfer:features:read}
42847 @item @samp{qXfer:libraries:read}
42852 @item @samp{qXfer:libraries-svr4:read}
42857 @item @samp{augmented-libraries-svr4-read}
42862 @item @samp{qXfer:memory-map:read}
42867 @item @samp{qXfer:sdata:read}
42872 @item @samp{qXfer:siginfo:read}
42877 @item @samp{qXfer:siginfo:write}
42882 @item @samp{qXfer:threads:read}
42887 @item @samp{qXfer:traceframe-info:read}
42892 @item @samp{qXfer:uib:read}
42897 @item @samp{qXfer:fdpic:read}
42902 @item @samp{Qbtrace:off}
42907 @item @samp{Qbtrace:bts}
42912 @item @samp{Qbtrace:pt}
42917 @item @samp{Qbtrace-conf:bts:size}
42922 @item @samp{Qbtrace-conf:pt:size}
42927 @item @samp{QNonStop}
42932 @item @samp{QCatchSyscalls}
42937 @item @samp{QPassSignals}
42942 @item @samp{QStartNoAckMode}
42947 @item @samp{multiprocess}
42952 @item @samp{ConditionalBreakpoints}
42957 @item @samp{ConditionalTracepoints}
42962 @item @samp{ReverseContinue}
42967 @item @samp{ReverseStep}
42972 @item @samp{TracepointSource}
42977 @item @samp{QAgent}
42982 @item @samp{QAllow}
42987 @item @samp{QDisableRandomization}
42992 @item @samp{EnableDisableTracepoints}
42997 @item @samp{QTBuffer:size}
43002 @item @samp{tracenz}
43007 @item @samp{BreakpointCommands}
43012 @item @samp{swbreak}
43017 @item @samp{hwbreak}
43022 @item @samp{fork-events}
43027 @item @samp{vfork-events}
43032 @item @samp{exec-events}
43037 @item @samp{QThreadEvents}
43042 @item @samp{no-resumed}
43047 @item @samp{memory-tagging}
43054 These are the currently defined stub features, in more detail:
43057 @cindex packet size, remote protocol
43058 @item PacketSize=@var{bytes}
43059 The remote stub can accept packets up to at least @var{bytes} in
43060 length. @value{GDBN} will send packets up to this size for bulk
43061 transfers, and will never send larger packets. This is a limit on the
43062 data characters in the packet, including the frame and checksum.
43063 There is no trailing NUL byte in a remote protocol packet; if the stub
43064 stores packets in a NUL-terminated format, it should allow an extra
43065 byte in its buffer for the NUL. If this stub feature is not supported,
43066 @value{GDBN} guesses based on the size of the @samp{g} packet response.
43068 @item qXfer:auxv:read
43069 The remote stub understands the @samp{qXfer:auxv:read} packet
43070 (@pxref{qXfer auxiliary vector read}).
43072 @item qXfer:btrace:read
43073 The remote stub understands the @samp{qXfer:btrace:read}
43074 packet (@pxref{qXfer btrace read}).
43076 @item qXfer:btrace-conf:read
43077 The remote stub understands the @samp{qXfer:btrace-conf:read}
43078 packet (@pxref{qXfer btrace-conf read}).
43080 @item qXfer:exec-file:read
43081 The remote stub understands the @samp{qXfer:exec-file:read} packet
43082 (@pxref{qXfer executable filename read}).
43084 @item qXfer:features:read
43085 The remote stub understands the @samp{qXfer:features:read} packet
43086 (@pxref{qXfer target description read}).
43088 @item qXfer:libraries:read
43089 The remote stub understands the @samp{qXfer:libraries:read} packet
43090 (@pxref{qXfer library list read}).
43092 @item qXfer:libraries-svr4:read
43093 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
43094 (@pxref{qXfer svr4 library list read}).
43096 @item augmented-libraries-svr4-read
43097 The remote stub understands the augmented form of the
43098 @samp{qXfer:libraries-svr4:read} packet
43099 (@pxref{qXfer svr4 library list read}).
43101 @item qXfer:memory-map:read
43102 The remote stub understands the @samp{qXfer:memory-map:read} packet
43103 (@pxref{qXfer memory map read}).
43105 @item qXfer:sdata:read
43106 The remote stub understands the @samp{qXfer:sdata:read} packet
43107 (@pxref{qXfer sdata read}).
43109 @item qXfer:siginfo:read
43110 The remote stub understands the @samp{qXfer:siginfo:read} packet
43111 (@pxref{qXfer siginfo read}).
43113 @item qXfer:siginfo:write
43114 The remote stub understands the @samp{qXfer:siginfo:write} packet
43115 (@pxref{qXfer siginfo write}).
43117 @item qXfer:threads:read
43118 The remote stub understands the @samp{qXfer:threads:read} packet
43119 (@pxref{qXfer threads read}).
43121 @item qXfer:traceframe-info:read
43122 The remote stub understands the @samp{qXfer:traceframe-info:read}
43123 packet (@pxref{qXfer traceframe info read}).
43125 @item qXfer:uib:read
43126 The remote stub understands the @samp{qXfer:uib:read}
43127 packet (@pxref{qXfer unwind info block}).
43129 @item qXfer:fdpic:read
43130 The remote stub understands the @samp{qXfer:fdpic:read}
43131 packet (@pxref{qXfer fdpic loadmap read}).
43134 The remote stub understands the @samp{QNonStop} packet
43135 (@pxref{QNonStop}).
43137 @item QCatchSyscalls
43138 The remote stub understands the @samp{QCatchSyscalls} packet
43139 (@pxref{QCatchSyscalls}).
43142 The remote stub understands the @samp{QPassSignals} packet
43143 (@pxref{QPassSignals}).
43145 @item QStartNoAckMode
43146 The remote stub understands the @samp{QStartNoAckMode} packet and
43147 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
43150 @anchor{multiprocess extensions}
43151 @cindex multiprocess extensions, in remote protocol
43152 The remote stub understands the multiprocess extensions to the remote
43153 protocol syntax. The multiprocess extensions affect the syntax of
43154 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
43155 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
43156 replies. Note that reporting this feature indicates support for the
43157 syntactic extensions only, not that the stub necessarily supports
43158 debugging of more than one process at a time. The stub must not use
43159 multiprocess extensions in packet replies unless @value{GDBN} has also
43160 indicated it supports them in its @samp{qSupported} request.
43162 @item qXfer:osdata:read
43163 The remote stub understands the @samp{qXfer:osdata:read} packet
43164 ((@pxref{qXfer osdata read}).
43166 @item ConditionalBreakpoints
43167 The target accepts and implements evaluation of conditional expressions
43168 defined for breakpoints. The target will only report breakpoint triggers
43169 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
43171 @item ConditionalTracepoints
43172 The remote stub accepts and implements conditional expressions defined
43173 for tracepoints (@pxref{Tracepoint Conditions}).
43175 @item ReverseContinue
43176 The remote stub accepts and implements the reverse continue packet
43180 The remote stub accepts and implements the reverse step packet
43183 @item TracepointSource
43184 The remote stub understands the @samp{QTDPsrc} packet that supplies
43185 the source form of tracepoint definitions.
43188 The remote stub understands the @samp{QAgent} packet.
43191 The remote stub understands the @samp{QAllow} packet.
43193 @item QDisableRandomization
43194 The remote stub understands the @samp{QDisableRandomization} packet.
43196 @item StaticTracepoint
43197 @cindex static tracepoints, in remote protocol
43198 The remote stub supports static tracepoints.
43200 @item InstallInTrace
43201 @anchor{install tracepoint in tracing}
43202 The remote stub supports installing tracepoint in tracing.
43204 @item EnableDisableTracepoints
43205 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
43206 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
43207 to be enabled and disabled while a trace experiment is running.
43209 @item QTBuffer:size
43210 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
43211 packet that allows to change the size of the trace buffer.
43214 @cindex string tracing, in remote protocol
43215 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
43216 See @ref{Bytecode Descriptions} for details about the bytecode.
43218 @item BreakpointCommands
43219 @cindex breakpoint commands, in remote protocol
43220 The remote stub supports running a breakpoint's command list itself,
43221 rather than reporting the hit to @value{GDBN}.
43224 The remote stub understands the @samp{Qbtrace:off} packet.
43227 The remote stub understands the @samp{Qbtrace:bts} packet.
43230 The remote stub understands the @samp{Qbtrace:pt} packet.
43232 @item Qbtrace-conf:bts:size
43233 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
43235 @item Qbtrace-conf:pt:size
43236 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
43239 The remote stub reports the @samp{swbreak} stop reason for memory
43243 The remote stub reports the @samp{hwbreak} stop reason for hardware
43247 The remote stub reports the @samp{fork} stop reason for fork events.
43250 The remote stub reports the @samp{vfork} stop reason for vfork events
43251 and vforkdone events.
43254 The remote stub reports the @samp{exec} stop reason for exec events.
43256 @item vContSupported
43257 The remote stub reports the supported actions in the reply to
43258 @samp{vCont?} packet.
43260 @item QThreadEvents
43261 The remote stub understands the @samp{QThreadEvents} packet.
43264 The remote stub reports the @samp{N} stop reply.
43267 @item memory-tagging
43268 The remote stub supports and implements the required memory tagging
43269 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
43270 @samp{QMemTags} (@pxref{QMemTags}) packets.
43272 For AArch64 GNU/Linux systems, this feature also requires access to the
43273 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
43274 This is done via the @samp{vFile} requests.
43279 @cindex symbol lookup, remote request
43280 @cindex @samp{qSymbol} packet
43281 Notify the target that @value{GDBN} is prepared to serve symbol lookup
43282 requests. Accept requests from the target for the values of symbols.
43287 The target does not need to look up any (more) symbols.
43288 @item qSymbol:@var{sym_name}
43289 The target requests the value of symbol @var{sym_name} (hex encoded).
43290 @value{GDBN} may provide the value by using the
43291 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
43295 @item qSymbol:@var{sym_value}:@var{sym_name}
43296 Set the value of @var{sym_name} to @var{sym_value}.
43298 @var{sym_name} (hex encoded) is the name of a symbol whose value the
43299 target has previously requested.
43301 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
43302 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
43308 The target does not need to look up any (more) symbols.
43309 @item qSymbol:@var{sym_name}
43310 The target requests the value of a new symbol @var{sym_name} (hex
43311 encoded). @value{GDBN} will continue to supply the values of symbols
43312 (if available), until the target ceases to request them.
43317 @itemx QTDisconnected
43324 @itemx qTMinFTPILen
43326 @xref{Tracepoint Packets}.
43328 @anchor{qThreadExtraInfo}
43329 @item qThreadExtraInfo,@var{thread-id}
43330 @cindex thread attributes info, remote request
43331 @cindex @samp{qThreadExtraInfo} packet
43332 Obtain from the target OS a printable string description of thread
43333 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
43334 for the forms of @var{thread-id}. This
43335 string may contain anything that the target OS thinks is interesting
43336 for @value{GDBN} to tell the user about the thread. The string is
43337 displayed in @value{GDBN}'s @code{info threads} display. Some
43338 examples of possible thread extra info strings are @samp{Runnable}, or
43339 @samp{Blocked on Mutex}.
43343 @item @var{XX}@dots{}
43344 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
43345 comprising the printable string containing the extra information about
43346 the thread's attributes.
43349 (Note that the @code{qThreadExtraInfo} packet's name is separated from
43350 the command by a @samp{,}, not a @samp{:}, contrary to the naming
43351 conventions above. Please don't use this packet as a model for new
43370 @xref{Tracepoint Packets}.
43372 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43373 @cindex read special object, remote request
43374 @cindex @samp{qXfer} packet
43375 @anchor{qXfer read}
43376 Read uninterpreted bytes from the target's special data area
43377 identified by the keyword @var{object}. Request @var{length} bytes
43378 starting at @var{offset} bytes into the data. The content and
43379 encoding of @var{annex} is specific to @var{object}; it can supply
43380 additional details about what data to access.
43385 Data @var{data} (@pxref{Binary Data}) has been read from the
43386 target. There may be more data at a higher address (although
43387 it is permitted to return @samp{m} even for the last valid
43388 block of data, as long as at least one byte of data was read).
43389 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43393 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43394 There is no more data to be read. It is possible for @var{data} to
43395 have fewer bytes than the @var{length} in the request.
43398 The @var{offset} in the request is at the end of the data.
43399 There is no more data to be read.
43402 The request was malformed, or @var{annex} was invalid.
43405 The offset was invalid, or there was an error encountered reading the data.
43406 The @var{nn} part is a hex-encoded @code{errno} value.
43409 An empty reply indicates the @var{object} string was not recognized by
43410 the stub, or that the object does not support reading.
43413 Here are the specific requests of this form defined so far. All the
43414 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43415 formats, listed above.
43418 @item qXfer:auxv:read::@var{offset},@var{length}
43419 @anchor{qXfer auxiliary vector read}
43420 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43421 auxiliary vector}. Note @var{annex} must be empty.
43423 This packet is not probed by default; the remote stub must request it,
43424 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43426 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43427 @anchor{qXfer btrace read}
43429 Return a description of the current branch trace.
43430 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43431 packet may have one of the following values:
43435 Returns all available branch trace.
43438 Returns all available branch trace if the branch trace changed since
43439 the last read request.
43442 Returns the new branch trace since the last read request. Adds a new
43443 block to the end of the trace that begins at zero and ends at the source
43444 location of the first branch in the trace buffer. This extra block is
43445 used to stitch traces together.
43447 If the trace buffer overflowed, returns an error indicating the overflow.
43450 This packet is not probed by default; the remote stub must request it
43451 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43453 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43454 @anchor{qXfer btrace-conf read}
43456 Return a description of the current branch trace configuration.
43457 @xref{Branch Trace Configuration Format}.
43459 This packet is not probed by default; the remote stub must request it
43460 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43462 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43463 @anchor{qXfer executable filename read}
43464 Return the full absolute name of the file that was executed to create
43465 a process running on the remote system. The annex specifies the
43466 numeric process ID of the process to query, encoded as a hexadecimal
43467 number. If the annex part is empty the remote stub should return the
43468 filename corresponding to the currently executing process.
43470 This packet is not probed by default; the remote stub must request it,
43471 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43473 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43474 @anchor{qXfer target description read}
43475 Access the @dfn{target description}. @xref{Target Descriptions}. The
43476 annex specifies which XML document to access. The main description is
43477 always loaded from the @samp{target.xml} annex.
43479 This packet is not probed by default; the remote stub must request it,
43480 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43482 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43483 @anchor{qXfer library list read}
43484 Access the target's list of loaded libraries. @xref{Library List Format}.
43485 The annex part of the generic @samp{qXfer} packet must be empty
43486 (@pxref{qXfer read}).
43488 Targets which maintain a list of libraries in the program's memory do
43489 not need to implement this packet; it is designed for platforms where
43490 the operating system manages the list of loaded libraries.
43492 This packet is not probed by default; the remote stub must request it,
43493 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43495 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43496 @anchor{qXfer svr4 library list read}
43497 Access the target's list of loaded libraries when the target is an SVR4
43498 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43499 of the generic @samp{qXfer} packet must be empty unless the remote
43500 stub indicated it supports the augmented form of this packet
43501 by supplying an appropriate @samp{qSupported} response
43502 (@pxref{qXfer read}, @ref{qSupported}).
43504 This packet is optional for better performance on SVR4 targets.
43505 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43507 This packet is not probed by default; the remote stub must request it,
43508 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43510 If the remote stub indicates it supports the augmented form of this
43511 packet then the annex part of the generic @samp{qXfer} packet may
43512 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43513 arguments. The currently supported arguments are:
43516 @item start=@var{address}
43517 A hexadecimal number specifying the address of the @samp{struct
43518 link_map} to start reading the library list from. If unset or zero
43519 then the first @samp{struct link_map} in the library list will be
43520 chosen as the starting point.
43522 @item prev=@var{address}
43523 A hexadecimal number specifying the address of the @samp{struct
43524 link_map} immediately preceding the @samp{struct link_map}
43525 specified by the @samp{start} argument. If unset or zero then
43526 the remote stub will expect that no @samp{struct link_map}
43527 exists prior to the starting point.
43531 Arguments that are not understood by the remote stub will be silently
43534 @item qXfer:memory-map:read::@var{offset},@var{length}
43535 @anchor{qXfer memory map read}
43536 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43537 annex part of the generic @samp{qXfer} packet must be empty
43538 (@pxref{qXfer read}).
43540 This packet is not probed by default; the remote stub must request it,
43541 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43543 @item qXfer:sdata:read::@var{offset},@var{length}
43544 @anchor{qXfer sdata read}
43546 Read contents of the extra collected static tracepoint marker
43547 information. The annex part of the generic @samp{qXfer} packet must
43548 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43551 This packet is not probed by default; the remote stub must request it,
43552 by supplying an appropriate @samp{qSupported} response
43553 (@pxref{qSupported}).
43555 @item qXfer:siginfo:read::@var{offset},@var{length}
43556 @anchor{qXfer siginfo read}
43557 Read contents of the extra signal information on the target
43558 system. The annex part of the generic @samp{qXfer} packet must be
43559 empty (@pxref{qXfer read}).
43561 This packet is not probed by default; the remote stub must request it,
43562 by supplying an appropriate @samp{qSupported} response
43563 (@pxref{qSupported}).
43565 @item qXfer:threads:read::@var{offset},@var{length}
43566 @anchor{qXfer threads read}
43567 Access the list of threads on target. @xref{Thread List Format}. The
43568 annex part of the generic @samp{qXfer} packet must be empty
43569 (@pxref{qXfer read}).
43571 This packet is not probed by default; the remote stub must request it,
43572 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43574 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43575 @anchor{qXfer traceframe info read}
43577 Return a description of the current traceframe's contents.
43578 @xref{Traceframe Info Format}. The annex part of the generic
43579 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43581 This packet is not probed by default; the remote stub must request it,
43582 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43584 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43585 @anchor{qXfer unwind info block}
43587 Return the unwind information block for @var{pc}. This packet is used
43588 on OpenVMS/ia64 to ask the kernel unwind information.
43590 This packet is not probed by default.
43592 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43593 @anchor{qXfer fdpic loadmap read}
43594 Read contents of @code{loadmap}s on the target system. The
43595 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43596 executable @code{loadmap} or interpreter @code{loadmap} to read.
43598 This packet is not probed by default; the remote stub must request it,
43599 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43601 @item qXfer:osdata:read::@var{offset},@var{length}
43602 @anchor{qXfer osdata read}
43603 Access the target's @dfn{operating system information}.
43604 @xref{Operating System Information}.
43608 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43609 @cindex write data into object, remote request
43610 @anchor{qXfer write}
43611 Write uninterpreted bytes into the target's special data area
43612 identified by the keyword @var{object}, starting at @var{offset} bytes
43613 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43614 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43615 is specific to @var{object}; it can supply additional details about what data
43621 @var{nn} (hex encoded) is the number of bytes written.
43622 This may be fewer bytes than supplied in the request.
43625 The request was malformed, or @var{annex} was invalid.
43628 The offset was invalid, or there was an error encountered writing the data.
43629 The @var{nn} part is a hex-encoded @code{errno} value.
43632 An empty reply indicates the @var{object} string was not
43633 recognized by the stub, or that the object does not support writing.
43636 Here are the specific requests of this form defined so far. All the
43637 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43638 formats, listed above.
43641 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43642 @anchor{qXfer siginfo write}
43643 Write @var{data} to the extra signal information on the target system.
43644 The annex part of the generic @samp{qXfer} packet must be
43645 empty (@pxref{qXfer write}).
43647 This packet is not probed by default; the remote stub must request it,
43648 by supplying an appropriate @samp{qSupported} response
43649 (@pxref{qSupported}).
43652 @item qXfer:@var{object}:@var{operation}:@dots{}
43653 Requests of this form may be added in the future. When a stub does
43654 not recognize the @var{object} keyword, or its support for
43655 @var{object} does not recognize the @var{operation} keyword, the stub
43656 must respond with an empty packet.
43658 @item qAttached:@var{pid}
43659 @cindex query attached, remote request
43660 @cindex @samp{qAttached} packet
43661 Return an indication of whether the remote server attached to an
43662 existing process or created a new process. When the multiprocess
43663 protocol extensions are supported (@pxref{multiprocess extensions}),
43664 @var{pid} is an integer in hexadecimal format identifying the target
43665 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43666 the query packet will be simplified as @samp{qAttached}.
43668 This query is used, for example, to know whether the remote process
43669 should be detached or killed when a @value{GDBN} session is ended with
43670 the @code{quit} command.
43675 The remote server attached to an existing process.
43677 The remote server created a new process.
43679 A badly formed request or an error was encountered.
43683 Enable branch tracing for the current thread using Branch Trace Store.
43688 Branch tracing has been enabled.
43690 A badly formed request or an error was encountered.
43694 Enable branch tracing for the current thread using Intel Processor Trace.
43699 Branch tracing has been enabled.
43701 A badly formed request or an error was encountered.
43705 Disable branch tracing for the current thread.
43710 Branch tracing has been disabled.
43712 A badly formed request or an error was encountered.
43715 @item Qbtrace-conf:bts:size=@var{value}
43716 Set the requested ring buffer size for new threads that use the
43717 btrace recording method in bts format.
43722 The ring buffer size has been set.
43724 A badly formed request or an error was encountered.
43727 @item Qbtrace-conf:pt:size=@var{value}
43728 Set the requested ring buffer size for new threads that use the
43729 btrace recording method in pt format.
43734 The ring buffer size has been set.
43736 A badly formed request or an error was encountered.
43741 @node Architecture-Specific Protocol Details
43742 @section Architecture-Specific Protocol Details
43744 This section describes how the remote protocol is applied to specific
43745 target architectures. Also see @ref{Standard Target Features}, for
43746 details of XML target descriptions for each architecture.
43749 * ARM-Specific Protocol Details::
43750 * MIPS-Specific Protocol Details::
43753 @node ARM-Specific Protocol Details
43754 @subsection @acronym{ARM}-specific Protocol Details
43757 * ARM Breakpoint Kinds::
43758 * ARM Memory Tag Types::
43761 @node ARM Breakpoint Kinds
43762 @subsubsection @acronym{ARM} Breakpoint Kinds
43763 @cindex breakpoint kinds, @acronym{ARM}
43765 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43770 16-bit Thumb mode breakpoint.
43773 32-bit Thumb mode (Thumb-2) breakpoint.
43776 32-bit @acronym{ARM} mode breakpoint.
43780 @node ARM Memory Tag Types
43781 @subsubsection @acronym{ARM} Memory Tag Types
43782 @cindex memory tag types, @acronym{ARM}
43784 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43797 @node MIPS-Specific Protocol Details
43798 @subsection @acronym{MIPS}-specific Protocol Details
43801 * MIPS Register packet Format::
43802 * MIPS Breakpoint Kinds::
43805 @node MIPS Register packet Format
43806 @subsubsection @acronym{MIPS} Register Packet Format
43807 @cindex register packet format, @acronym{MIPS}
43809 The following @code{g}/@code{G} packets have previously been defined.
43810 In the below, some thirty-two bit registers are transferred as
43811 sixty-four bits. Those registers should be zero/sign extended (which?)
43812 to fill the space allocated. Register bytes are transferred in target
43813 byte order. The two nibbles within a register byte are transferred
43814 most-significant -- least-significant.
43819 All registers are transferred as thirty-two bit quantities in the order:
43820 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43821 registers; fsr; fir; fp.
43824 All registers are transferred as sixty-four bit quantities (including
43825 thirty-two bit registers such as @code{sr}). The ordering is the same
43830 @node MIPS Breakpoint Kinds
43831 @subsubsection @acronym{MIPS} Breakpoint Kinds
43832 @cindex breakpoint kinds, @acronym{MIPS}
43834 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43839 16-bit @acronym{MIPS16} mode breakpoint.
43842 16-bit @acronym{microMIPS} mode breakpoint.
43845 32-bit standard @acronym{MIPS} mode breakpoint.
43848 32-bit @acronym{microMIPS} mode breakpoint.
43852 @node Tracepoint Packets
43853 @section Tracepoint Packets
43854 @cindex tracepoint packets
43855 @cindex packets, tracepoint
43857 Here we describe the packets @value{GDBN} uses to implement
43858 tracepoints (@pxref{Tracepoints}).
43862 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43863 @cindex @samp{QTDP} packet
43864 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43865 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43866 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43867 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43868 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43869 the number of bytes that the target should copy elsewhere to make room
43870 for the tracepoint. If an @samp{X} is present, it introduces a
43871 tracepoint condition, which consists of a hexadecimal length, followed
43872 by a comma and hex-encoded bytes, in a manner similar to action
43873 encodings as described below. If the trailing @samp{-} is present,
43874 further @samp{QTDP} packets will follow to specify this tracepoint's
43880 The packet was understood and carried out.
43882 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43884 The packet was not recognized.
43887 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43888 Define actions to be taken when a tracepoint is hit. The @var{n} and
43889 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43890 this tracepoint. This packet may only be sent immediately after
43891 another @samp{QTDP} packet that ended with a @samp{-}. If the
43892 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43893 specifying more actions for this tracepoint.
43895 In the series of action packets for a given tracepoint, at most one
43896 can have an @samp{S} before its first @var{action}. If such a packet
43897 is sent, it and the following packets define ``while-stepping''
43898 actions. Any prior packets define ordinary actions --- that is, those
43899 taken when the tracepoint is first hit. If no action packet has an
43900 @samp{S}, then all the packets in the series specify ordinary
43901 tracepoint actions.
43903 The @samp{@var{action}@dots{}} portion of the packet is a series of
43904 actions, concatenated without separators. Each action has one of the
43910 Collect the registers whose bits are set in @var{mask},
43911 a hexadecimal number whose @var{i}'th bit is set if register number
43912 @var{i} should be collected. (The least significant bit is numbered
43913 zero.) Note that @var{mask} may be any number of digits long; it may
43914 not fit in a 32-bit word.
43916 @item M @var{basereg},@var{offset},@var{len}
43917 Collect @var{len} bytes of memory starting at the address in register
43918 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43919 @samp{-1}, then the range has a fixed address: @var{offset} is the
43920 address of the lowest byte to collect. The @var{basereg},
43921 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43922 values (the @samp{-1} value for @var{basereg} is a special case).
43924 @item X @var{len},@var{expr}
43925 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43926 it directs. The agent expression @var{expr} is as described in
43927 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43928 two-digit hex number in the packet; @var{len} is the number of bytes
43929 in the expression (and thus one-half the number of hex digits in the
43934 Any number of actions may be packed together in a single @samp{QTDP}
43935 packet, as long as the packet does not exceed the maximum packet
43936 length (400 bytes, for many stubs). There may be only one @samp{R}
43937 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43938 actions. Any registers referred to by @samp{M} and @samp{X} actions
43939 must be collected by a preceding @samp{R} action. (The
43940 ``while-stepping'' actions are treated as if they were attached to a
43941 separate tracepoint, as far as these restrictions are concerned.)
43946 The packet was understood and carried out.
43948 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43950 The packet was not recognized.
43953 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43954 @cindex @samp{QTDPsrc} packet
43955 Specify a source string of tracepoint @var{n} at address @var{addr}.
43956 This is useful to get accurate reproduction of the tracepoints
43957 originally downloaded at the beginning of the trace run. The @var{type}
43958 is the name of the tracepoint part, such as @samp{cond} for the
43959 tracepoint's conditional expression (see below for a list of types), while
43960 @var{bytes} is the string, encoded in hexadecimal.
43962 @var{start} is the offset of the @var{bytes} within the overall source
43963 string, while @var{slen} is the total length of the source string.
43964 This is intended for handling source strings that are longer than will
43965 fit in a single packet.
43966 @c Add detailed example when this info is moved into a dedicated
43967 @c tracepoint descriptions section.
43969 The available string types are @samp{at} for the location,
43970 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43971 @value{GDBN} sends a separate packet for each command in the action
43972 list, in the same order in which the commands are stored in the list.
43974 The target does not need to do anything with source strings except
43975 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43978 Although this packet is optional, and @value{GDBN} will only send it
43979 if the target replies with @samp{TracepointSource} @xref{General
43980 Query Packets}, it makes both disconnected tracing and trace files
43981 much easier to use. Otherwise the user must be careful that the
43982 tracepoints in effect while looking at trace frames are identical to
43983 the ones in effect during the trace run; even a small discrepancy
43984 could cause @samp{tdump} not to work, or a particular trace frame not
43987 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43988 @cindex define trace state variable, remote request
43989 @cindex @samp{QTDV} packet
43990 Create a new trace state variable, number @var{n}, with an initial
43991 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43992 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43993 the option of not using this packet for initial values of zero; the
43994 target should simply create the trace state variables as they are
43995 mentioned in expressions. The value @var{builtin} should be 1 (one)
43996 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43997 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43998 @samp{qTsV} packet had it set. The contents of @var{name} is the
43999 hex-encoded name (without the leading @samp{$}) of the trace state
44002 @item QTFrame:@var{n}
44003 @cindex @samp{QTFrame} packet
44004 Select the @var{n}'th tracepoint frame from the buffer, and use the
44005 register and memory contents recorded there to answer subsequent
44006 request packets from @value{GDBN}.
44008 A successful reply from the stub indicates that the stub has found the
44009 requested frame. The response is a series of parts, concatenated
44010 without separators, describing the frame we selected. Each part has
44011 one of the following forms:
44015 The selected frame is number @var{n} in the trace frame buffer;
44016 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
44017 was no frame matching the criteria in the request packet.
44020 The selected trace frame records a hit of tracepoint number @var{t};
44021 @var{t} is a hexadecimal number.
44025 @item QTFrame:pc:@var{addr}
44026 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44027 currently selected frame whose PC is @var{addr};
44028 @var{addr} is a hexadecimal number.
44030 @item QTFrame:tdp:@var{t}
44031 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44032 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
44033 is a hexadecimal number.
44035 @item QTFrame:range:@var{start}:@var{end}
44036 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44037 currently selected frame whose PC is between @var{start} (inclusive)
44038 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
44041 @item QTFrame:outside:@var{start}:@var{end}
44042 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
44043 frame @emph{outside} the given range of addresses (exclusive).
44046 @cindex @samp{qTMinFTPILen} packet
44047 This packet requests the minimum length of instruction at which a fast
44048 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
44049 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
44050 it depends on the target system being able to create trampolines in
44051 the first 64K of memory, which might or might not be possible for that
44052 system. So the reply to this packet will be 4 if it is able to
44059 The minimum instruction length is currently unknown.
44061 The minimum instruction length is @var{length}, where @var{length}
44062 is a hexadecimal number greater or equal to 1. A reply
44063 of 1 means that a fast tracepoint may be placed on any instruction
44064 regardless of size.
44066 An error has occurred.
44068 An empty reply indicates that the request is not supported by the stub.
44072 @cindex @samp{QTStart} packet
44073 Begin the tracepoint experiment. Begin collecting data from
44074 tracepoint hits in the trace frame buffer. This packet supports the
44075 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
44076 instruction reply packet}).
44079 @cindex @samp{QTStop} packet
44080 End the tracepoint experiment. Stop collecting trace frames.
44082 @item QTEnable:@var{n}:@var{addr}
44084 @cindex @samp{QTEnable} packet
44085 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
44086 experiment. If the tracepoint was previously disabled, then collection
44087 of data from it will resume.
44089 @item QTDisable:@var{n}:@var{addr}
44091 @cindex @samp{QTDisable} packet
44092 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
44093 experiment. No more data will be collected from the tracepoint unless
44094 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
44097 @cindex @samp{QTinit} packet
44098 Clear the table of tracepoints, and empty the trace frame buffer.
44100 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
44101 @cindex @samp{QTro} packet
44102 Establish the given ranges of memory as ``transparent''. The stub
44103 will answer requests for these ranges from memory's current contents,
44104 if they were not collected as part of the tracepoint hit.
44106 @value{GDBN} uses this to mark read-only regions of memory, like those
44107 containing program code. Since these areas never change, they should
44108 still have the same contents they did when the tracepoint was hit, so
44109 there's no reason for the stub to refuse to provide their contents.
44111 @item QTDisconnected:@var{value}
44112 @cindex @samp{QTDisconnected} packet
44113 Set the choice to what to do with the tracing run when @value{GDBN}
44114 disconnects from the target. A @var{value} of 1 directs the target to
44115 continue the tracing run, while 0 tells the target to stop tracing if
44116 @value{GDBN} is no longer in the picture.
44119 @cindex @samp{qTStatus} packet
44120 Ask the stub if there is a trace experiment running right now.
44122 The reply has the form:
44126 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
44127 @var{running} is a single digit @code{1} if the trace is presently
44128 running, or @code{0} if not. It is followed by semicolon-separated
44129 optional fields that an agent may use to report additional status.
44133 If the trace is not running, the agent may report any of several
44134 explanations as one of the optional fields:
44139 No trace has been run yet.
44141 @item tstop[:@var{text}]:0
44142 The trace was stopped by a user-originated stop command. The optional
44143 @var{text} field is a user-supplied string supplied as part of the
44144 stop command (for instance, an explanation of why the trace was
44145 stopped manually). It is hex-encoded.
44148 The trace stopped because the trace buffer filled up.
44150 @item tdisconnected:0
44151 The trace stopped because @value{GDBN} disconnected from the target.
44153 @item tpasscount:@var{tpnum}
44154 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
44156 @item terror:@var{text}:@var{tpnum}
44157 The trace stopped because tracepoint @var{tpnum} had an error. The
44158 string @var{text} is available to describe the nature of the error
44159 (for instance, a divide by zero in the condition expression); it
44163 The trace stopped for some other reason.
44167 Additional optional fields supply statistical and other information.
44168 Although not required, they are extremely useful for users monitoring
44169 the progress of a trace run. If a trace has stopped, and these
44170 numbers are reported, they must reflect the state of the just-stopped
44175 @item tframes:@var{n}
44176 The number of trace frames in the buffer.
44178 @item tcreated:@var{n}
44179 The total number of trace frames created during the run. This may
44180 be larger than the trace frame count, if the buffer is circular.
44182 @item tsize:@var{n}
44183 The total size of the trace buffer, in bytes.
44185 @item tfree:@var{n}
44186 The number of bytes still unused in the buffer.
44188 @item circular:@var{n}
44189 The value of the circular trace buffer flag. @code{1} means that the
44190 trace buffer is circular and old trace frames will be discarded if
44191 necessary to make room, @code{0} means that the trace buffer is linear
44194 @item disconn:@var{n}
44195 The value of the disconnected tracing flag. @code{1} means that
44196 tracing will continue after @value{GDBN} disconnects, @code{0} means
44197 that the trace run will stop.
44201 @item qTP:@var{tp}:@var{addr}
44202 @cindex tracepoint status, remote request
44203 @cindex @samp{qTP} packet
44204 Ask the stub for the current state of tracepoint number @var{tp} at
44205 address @var{addr}.
44209 @item V@var{hits}:@var{usage}
44210 The tracepoint has been hit @var{hits} times so far during the trace
44211 run, and accounts for @var{usage} in the trace buffer. Note that
44212 @code{while-stepping} steps are not counted as separate hits, but the
44213 steps' space consumption is added into the usage number.
44217 @item qTV:@var{var}
44218 @cindex trace state variable value, remote request
44219 @cindex @samp{qTV} packet
44220 Ask the stub for the value of the trace state variable number @var{var}.
44225 The value of the variable is @var{value}. This will be the current
44226 value of the variable if the user is examining a running target, or a
44227 saved value if the variable was collected in the trace frame that the
44228 user is looking at. Note that multiple requests may result in
44229 different reply values, such as when requesting values while the
44230 program is running.
44233 The value of the variable is unknown. This would occur, for example,
44234 if the user is examining a trace frame in which the requested variable
44239 @cindex @samp{qTfP} packet
44241 @cindex @samp{qTsP} packet
44242 These packets request data about tracepoints that are being used by
44243 the target. @value{GDBN} sends @code{qTfP} to get the first piece
44244 of data, and multiple @code{qTsP} to get additional pieces. Replies
44245 to these packets generally take the form of the @code{QTDP} packets
44246 that define tracepoints. (FIXME add detailed syntax)
44249 @cindex @samp{qTfV} packet
44251 @cindex @samp{qTsV} packet
44252 These packets request data about trace state variables that are on the
44253 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
44254 and multiple @code{qTsV} to get additional variables. Replies to
44255 these packets follow the syntax of the @code{QTDV} packets that define
44256 trace state variables.
44262 @cindex @samp{qTfSTM} packet
44263 @cindex @samp{qTsSTM} packet
44264 These packets request data about static tracepoint markers that exist
44265 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
44266 first piece of data, and multiple @code{qTsSTM} to get additional
44267 pieces. Replies to these packets take the following form:
44271 @item m @var{address}:@var{id}:@var{extra}
44273 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
44274 a comma-separated list of markers
44276 (lower case letter @samp{L}) denotes end of list.
44278 An error occurred. The error number @var{nn} is given as hex digits.
44280 An empty reply indicates that the request is not supported by the
44284 The @var{address} is encoded in hex;
44285 @var{id} and @var{extra} are strings encoded in hex.
44287 In response to each query, the target will reply with a list of one or
44288 more markers, separated by commas. @value{GDBN} will respond to each
44289 reply with a request for more markers (using the @samp{qs} form of the
44290 query), until the target responds with @samp{l} (lower-case ell, for
44293 @item qTSTMat:@var{address}
44295 @cindex @samp{qTSTMat} packet
44296 This packets requests data about static tracepoint markers in the
44297 target program at @var{address}. Replies to this packet follow the
44298 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
44299 tracepoint markers.
44301 @item QTSave:@var{filename}
44302 @cindex @samp{QTSave} packet
44303 This packet directs the target to save trace data to the file name
44304 @var{filename} in the target's filesystem. The @var{filename} is encoded
44305 as a hex string; the interpretation of the file name (relative vs
44306 absolute, wild cards, etc) is up to the target.
44308 @item qTBuffer:@var{offset},@var{len}
44309 @cindex @samp{qTBuffer} packet
44310 Return up to @var{len} bytes of the current contents of trace buffer,
44311 starting at @var{offset}. The trace buffer is treated as if it were
44312 a contiguous collection of traceframes, as per the trace file format.
44313 The reply consists as many hex-encoded bytes as the target can deliver
44314 in a packet; it is not an error to return fewer than were asked for.
44315 A reply consisting of just @code{l} indicates that no bytes are
44318 @item QTBuffer:circular:@var{value}
44319 This packet directs the target to use a circular trace buffer if
44320 @var{value} is 1, or a linear buffer if the value is 0.
44322 @item QTBuffer:size:@var{size}
44323 @anchor{QTBuffer-size}
44324 @cindex @samp{QTBuffer size} packet
44325 This packet directs the target to make the trace buffer be of size
44326 @var{size} if possible. A value of @code{-1} tells the target to
44327 use whatever size it prefers.
44329 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
44330 @cindex @samp{QTNotes} packet
44331 This packet adds optional textual notes to the trace run. Allowable
44332 types include @code{user}, @code{notes}, and @code{tstop}, the
44333 @var{text} fields are arbitrary strings, hex-encoded.
44337 @subsection Relocate instruction reply packet
44338 When installing fast tracepoints in memory, the target may need to
44339 relocate the instruction currently at the tracepoint address to a
44340 different address in memory. For most instructions, a simple copy is
44341 enough, but, for example, call instructions that implicitly push the
44342 return address on the stack, and relative branches or other
44343 PC-relative instructions require offset adjustment, so that the effect
44344 of executing the instruction at a different address is the same as if
44345 it had executed in the original location.
44347 In response to several of the tracepoint packets, the target may also
44348 respond with a number of intermediate @samp{qRelocInsn} request
44349 packets before the final result packet, to have @value{GDBN} handle
44350 this relocation operation. If a packet supports this mechanism, its
44351 documentation will explicitly say so. See for example the above
44352 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
44353 format of the request is:
44356 @item qRelocInsn:@var{from};@var{to}
44358 This requests @value{GDBN} to copy instruction at address @var{from}
44359 to address @var{to}, possibly adjusted so that executing the
44360 instruction at @var{to} has the same effect as executing it at
44361 @var{from}. @value{GDBN} writes the adjusted instruction to target
44362 memory starting at @var{to}.
44367 @item qRelocInsn:@var{adjusted_size}
44368 Informs the stub the relocation is complete. The @var{adjusted_size} is
44369 the length in bytes of resulting relocated instruction sequence.
44371 A badly formed request was detected, or an error was encountered while
44372 relocating the instruction.
44375 @node Host I/O Packets
44376 @section Host I/O Packets
44377 @cindex Host I/O, remote protocol
44378 @cindex file transfer, remote protocol
44380 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44381 operations on the far side of a remote link. For example, Host I/O is
44382 used to upload and download files to a remote target with its own
44383 filesystem. Host I/O uses the same constant values and data structure
44384 layout as the target-initiated File-I/O protocol. However, the
44385 Host I/O packets are structured differently. The target-initiated
44386 protocol relies on target memory to store parameters and buffers.
44387 Host I/O requests are initiated by @value{GDBN}, and the
44388 target's memory is not involved. @xref{File-I/O Remote Protocol
44389 Extension}, for more details on the target-initiated protocol.
44391 The Host I/O request packets all encode a single operation along with
44392 its arguments. They have this format:
44396 @item vFile:@var{operation}: @var{parameter}@dots{}
44397 @var{operation} is the name of the particular request; the target
44398 should compare the entire packet name up to the second colon when checking
44399 for a supported operation. The format of @var{parameter} depends on
44400 the operation. Numbers are always passed in hexadecimal. Negative
44401 numbers have an explicit minus sign (i.e.@: two's complement is not
44402 used). Strings (e.g.@: filenames) are encoded as a series of
44403 hexadecimal bytes. The last argument to a system call may be a
44404 buffer of escaped binary data (@pxref{Binary Data}).
44408 The valid responses to Host I/O packets are:
44412 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44413 @var{result} is the integer value returned by this operation, usually
44414 non-negative for success and -1 for errors. If an error has occured,
44415 @var{errno} will be included in the result specifying a
44416 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44417 operations which return data, @var{attachment} supplies the data as a
44418 binary buffer. Binary buffers in response packets are escaped in the
44419 normal way (@pxref{Binary Data}). See the individual packet
44420 documentation for the interpretation of @var{result} and
44424 An empty response indicates that this operation is not recognized.
44428 These are the supported Host I/O operations:
44431 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44432 Open a file at @var{filename} and return a file descriptor for it, or
44433 return -1 if an error occurs. The @var{filename} is a string,
44434 @var{flags} is an integer indicating a mask of open flags
44435 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44436 of mode bits to use if the file is created (@pxref{mode_t Values}).
44437 @xref{open}, for details of the open flags and mode values.
44439 @item vFile:close: @var{fd}
44440 Close the open file corresponding to @var{fd} and return 0, or
44441 -1 if an error occurs.
44443 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44444 Read data from the open file corresponding to @var{fd}. Up to
44445 @var{count} bytes will be read from the file, starting at @var{offset}
44446 relative to the start of the file. The target may read fewer bytes;
44447 common reasons include packet size limits and an end-of-file
44448 condition. The number of bytes read is returned. Zero should only be
44449 returned for a successful read at the end of the file, or if
44450 @var{count} was zero.
44452 The data read should be returned as a binary attachment on success.
44453 If zero bytes were read, the response should include an empty binary
44454 attachment (i.e.@: a trailing semicolon). The return value is the
44455 number of target bytes read; the binary attachment may be longer if
44456 some characters were escaped.
44458 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44459 Write @var{data} (a binary buffer) to the open file corresponding
44460 to @var{fd}. Start the write at @var{offset} from the start of the
44461 file. Unlike many @code{write} system calls, there is no
44462 separate @var{count} argument; the length of @var{data} in the
44463 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44464 which may be shorter than the length of @var{data}, or -1 if an
44467 @item vFile:fstat: @var{fd}
44468 Get information about the open file corresponding to @var{fd}.
44469 On success the information is returned as a binary attachment
44470 and the return value is the size of this attachment in bytes.
44471 If an error occurs the return value is -1. The format of the
44472 returned binary attachment is as described in @ref{struct stat}.
44474 @item vFile:unlink: @var{filename}
44475 Delete the file at @var{filename} on the target. Return 0,
44476 or -1 if an error occurs. The @var{filename} is a string.
44478 @item vFile:readlink: @var{filename}
44479 Read value of symbolic link @var{filename} on the target. Return
44480 the number of bytes read, or -1 if an error occurs.
44482 The data read should be returned as a binary attachment on success.
44483 If zero bytes were read, the response should include an empty binary
44484 attachment (i.e.@: a trailing semicolon). The return value is the
44485 number of target bytes read; the binary attachment may be longer if
44486 some characters were escaped.
44488 @item vFile:setfs: @var{pid}
44489 Select the filesystem on which @code{vFile} operations with
44490 @var{filename} arguments will operate. This is required for
44491 @value{GDBN} to be able to access files on remote targets where
44492 the remote stub does not share a common filesystem with the
44495 If @var{pid} is nonzero, select the filesystem as seen by process
44496 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44497 the remote stub. Return 0 on success, or -1 if an error occurs.
44498 If @code{vFile:setfs:} indicates success, the selected filesystem
44499 remains selected until the next successful @code{vFile:setfs:}
44505 @section Interrupts
44506 @cindex interrupts (remote protocol)
44507 @anchor{interrupting remote targets}
44509 In all-stop mode, when a program on the remote target is running,
44510 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44511 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44512 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44514 The precise meaning of @code{BREAK} is defined by the transport
44515 mechanism and may, in fact, be undefined. @value{GDBN} does not
44516 currently define a @code{BREAK} mechanism for any of the network
44517 interfaces except for TCP, in which case @value{GDBN} sends the
44518 @code{telnet} BREAK sequence.
44520 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44521 transport mechanisms. It is represented by sending the single byte
44522 @code{0x03} without any of the usual packet overhead described in
44523 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44524 transmitted as part of a packet, it is considered to be packet data
44525 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44526 (@pxref{X packet}), used for binary downloads, may include an unescaped
44527 @code{0x03} as part of its packet.
44529 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44530 When Linux kernel receives this sequence from serial port,
44531 it stops execution and connects to gdb.
44533 In non-stop mode, because packet resumptions are asynchronous
44534 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44535 command to the remote stub, even when the target is running. For that
44536 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44537 packet}) with the usual packet framing instead of the single byte
44540 Stubs are not required to recognize these interrupt mechanisms and the
44541 precise meaning associated with receipt of the interrupt is
44542 implementation defined. If the target supports debugging of multiple
44543 threads and/or processes, it should attempt to interrupt all
44544 currently-executing threads and processes.
44545 If the stub is successful at interrupting the
44546 running program, it should send one of the stop
44547 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44548 of successfully stopping the program in all-stop mode, and a stop reply
44549 for each stopped thread in non-stop mode.
44550 Interrupts received while the
44551 program is stopped are queued and the program will be interrupted when
44552 it is resumed next time.
44554 @node Notification Packets
44555 @section Notification Packets
44556 @cindex notification packets
44557 @cindex packets, notification
44559 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44560 packets that require no acknowledgment. Both the GDB and the stub
44561 may send notifications (although the only notifications defined at
44562 present are sent by the stub). Notifications carry information
44563 without incurring the round-trip latency of an acknowledgment, and so
44564 are useful for low-impact communications where occasional packet loss
44567 A notification packet has the form @samp{% @var{data} #
44568 @var{checksum}}, where @var{data} is the content of the notification,
44569 and @var{checksum} is a checksum of @var{data}, computed and formatted
44570 as for ordinary @value{GDBN} packets. A notification's @var{data}
44571 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44572 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44573 to acknowledge the notification's receipt or to report its corruption.
44575 Every notification's @var{data} begins with a name, which contains no
44576 colon characters, followed by a colon character.
44578 Recipients should silently ignore corrupted notifications and
44579 notifications they do not understand. Recipients should restart
44580 timeout periods on receipt of a well-formed notification, whether or
44581 not they understand it.
44583 Senders should only send the notifications described here when this
44584 protocol description specifies that they are permitted. In the
44585 future, we may extend the protocol to permit existing notifications in
44586 new contexts; this rule helps older senders avoid confusing newer
44589 (Older versions of @value{GDBN} ignore bytes received until they see
44590 the @samp{$} byte that begins an ordinary packet, so new stubs may
44591 transmit notifications without fear of confusing older clients. There
44592 are no notifications defined for @value{GDBN} to send at the moment, but we
44593 assume that most older stubs would ignore them, as well.)
44595 Each notification is comprised of three parts:
44597 @item @var{name}:@var{event}
44598 The notification packet is sent by the side that initiates the
44599 exchange (currently, only the stub does that), with @var{event}
44600 carrying the specific information about the notification, and
44601 @var{name} specifying the name of the notification.
44603 The acknowledge sent by the other side, usually @value{GDBN}, to
44604 acknowledge the exchange and request the event.
44607 The purpose of an asynchronous notification mechanism is to report to
44608 @value{GDBN} that something interesting happened in the remote stub.
44610 The remote stub may send notification @var{name}:@var{event}
44611 at any time, but @value{GDBN} acknowledges the notification when
44612 appropriate. The notification event is pending before @value{GDBN}
44613 acknowledges. Only one notification at a time may be pending; if
44614 additional events occur before @value{GDBN} has acknowledged the
44615 previous notification, they must be queued by the stub for later
44616 synchronous transmission in response to @var{ack} packets from
44617 @value{GDBN}. Because the notification mechanism is unreliable,
44618 the stub is permitted to resend a notification if it believes
44619 @value{GDBN} may not have received it.
44621 Specifically, notifications may appear when @value{GDBN} is not
44622 otherwise reading input from the stub, or when @value{GDBN} is
44623 expecting to read a normal synchronous response or a
44624 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44625 Notification packets are distinct from any other communication from
44626 the stub so there is no ambiguity.
44628 After receiving a notification, @value{GDBN} shall acknowledge it by
44629 sending a @var{ack} packet as a regular, synchronous request to the
44630 stub. Such acknowledgment is not required to happen immediately, as
44631 @value{GDBN} is permitted to send other, unrelated packets to the
44632 stub first, which the stub should process normally.
44634 Upon receiving a @var{ack} packet, if the stub has other queued
44635 events to report to @value{GDBN}, it shall respond by sending a
44636 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44637 packet to solicit further responses; again, it is permitted to send
44638 other, unrelated packets as well which the stub should process
44641 If the stub receives a @var{ack} packet and there are no additional
44642 @var{event} to report, the stub shall return an @samp{OK} response.
44643 At this point, @value{GDBN} has finished processing a notification
44644 and the stub has completed sending any queued events. @value{GDBN}
44645 won't accept any new notifications until the final @samp{OK} is
44646 received . If further notification events occur, the stub shall send
44647 a new notification, @value{GDBN} shall accept the notification, and
44648 the process shall be repeated.
44650 The process of asynchronous notification can be illustrated by the
44653 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44656 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44658 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44663 The following notifications are defined:
44664 @multitable @columnfractions 0.12 0.12 0.38 0.38
44673 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44674 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44675 for information on how these notifications are acknowledged by
44677 @tab Report an asynchronous stop event in non-stop mode.
44681 @node Remote Non-Stop
44682 @section Remote Protocol Support for Non-Stop Mode
44684 @value{GDBN}'s remote protocol supports non-stop debugging of
44685 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44686 supports non-stop mode, it should report that to @value{GDBN} by including
44687 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44689 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44690 establishing a new connection with the stub. Entering non-stop mode
44691 does not alter the state of any currently-running threads, but targets
44692 must stop all threads in any already-attached processes when entering
44693 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44694 probe the target state after a mode change.
44696 In non-stop mode, when an attached process encounters an event that
44697 would otherwise be reported with a stop reply, it uses the
44698 asynchronous notification mechanism (@pxref{Notification Packets}) to
44699 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44700 in all processes are stopped when a stop reply is sent, in non-stop
44701 mode only the thread reporting the stop event is stopped. That is,
44702 when reporting a @samp{S} or @samp{T} response to indicate completion
44703 of a step operation, hitting a breakpoint, or a fault, only the
44704 affected thread is stopped; any other still-running threads continue
44705 to run. When reporting a @samp{W} or @samp{X} response, all running
44706 threads belonging to other attached processes continue to run.
44708 In non-stop mode, the target shall respond to the @samp{?} packet as
44709 follows. First, any incomplete stop reply notification/@samp{vStopped}
44710 sequence in progress is abandoned. The target must begin a new
44711 sequence reporting stop events for all stopped threads, whether or not
44712 it has previously reported those events to @value{GDBN}. The first
44713 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44714 subsequent stop replies are sent as responses to @samp{vStopped} packets
44715 using the mechanism described above. The target must not send
44716 asynchronous stop reply notifications until the sequence is complete.
44717 If all threads are running when the target receives the @samp{?} packet,
44718 or if the target is not attached to any process, it shall respond
44721 If the stub supports non-stop mode, it should also support the
44722 @samp{swbreak} stop reason if software breakpoints are supported, and
44723 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44724 (@pxref{swbreak stop reason}). This is because given the asynchronous
44725 nature of non-stop mode, between the time a thread hits a breakpoint
44726 and the time the event is finally processed by @value{GDBN}, the
44727 breakpoint may have already been removed from the target. Due to
44728 this, @value{GDBN} needs to be able to tell whether a trap stop was
44729 caused by a delayed breakpoint event, which should be ignored, as
44730 opposed to a random trap signal, which should be reported to the user.
44731 Note the @samp{swbreak} feature implies that the target is responsible
44732 for adjusting the PC when a software breakpoint triggers, if
44733 necessary, such as on the x86 architecture.
44735 @node Packet Acknowledgment
44736 @section Packet Acknowledgment
44738 @cindex acknowledgment, for @value{GDBN} remote
44739 @cindex packet acknowledgment, for @value{GDBN} remote
44740 By default, when either the host or the target machine receives a packet,
44741 the first response expected is an acknowledgment: either @samp{+} (to indicate
44742 the package was received correctly) or @samp{-} (to request retransmission).
44743 This mechanism allows the @value{GDBN} remote protocol to operate over
44744 unreliable transport mechanisms, such as a serial line.
44746 In cases where the transport mechanism is itself reliable (such as a pipe or
44747 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44748 It may be desirable to disable them in that case to reduce communication
44749 overhead, or for other reasons. This can be accomplished by means of the
44750 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44752 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44753 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44754 and response format still includes the normal checksum, as described in
44755 @ref{Overview}, but the checksum may be ignored by the receiver.
44757 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44758 no-acknowledgment mode, it should report that to @value{GDBN}
44759 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44760 @pxref{qSupported}.
44761 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44762 disabled via the @code{set remote noack-packet off} command
44763 (@pxref{Remote Configuration}),
44764 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44765 Only then may the stub actually turn off packet acknowledgments.
44766 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44767 response, which can be safely ignored by the stub.
44769 Note that @code{set remote noack-packet} command only affects negotiation
44770 between @value{GDBN} and the stub when subsequent connections are made;
44771 it does not affect the protocol acknowledgment state for any current
44773 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44774 new connection is established,
44775 there is also no protocol request to re-enable the acknowledgments
44776 for the current connection, once disabled.
44781 Example sequence of a target being re-started. Notice how the restart
44782 does not get any direct output:
44787 @emph{target restarts}
44790 <- @code{T001:1234123412341234}
44794 Example sequence of a target being stepped by a single instruction:
44797 -> @code{G1445@dots{}}
44802 <- @code{T001:1234123412341234}
44806 <- @code{1455@dots{}}
44810 @node File-I/O Remote Protocol Extension
44811 @section File-I/O Remote Protocol Extension
44812 @cindex File-I/O remote protocol extension
44815 * File-I/O Overview::
44816 * Protocol Basics::
44817 * The F Request Packet::
44818 * The F Reply Packet::
44819 * The Ctrl-C Message::
44821 * List of Supported Calls::
44822 * Protocol-specific Representation of Datatypes::
44824 * File-I/O Examples::
44827 @node File-I/O Overview
44828 @subsection File-I/O Overview
44829 @cindex file-i/o overview
44831 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44832 target to use the host's file system and console I/O to perform various
44833 system calls. System calls on the target system are translated into a
44834 remote protocol packet to the host system, which then performs the needed
44835 actions and returns a response packet to the target system.
44836 This simulates file system operations even on targets that lack file systems.
44838 The protocol is defined to be independent of both the host and target systems.
44839 It uses its own internal representation of datatypes and values. Both
44840 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44841 translating the system-dependent value representations into the internal
44842 protocol representations when data is transmitted.
44844 The communication is synchronous. A system call is possible only when
44845 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44846 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44847 the target is stopped to allow deterministic access to the target's
44848 memory. Therefore File-I/O is not interruptible by target signals. On
44849 the other hand, it is possible to interrupt File-I/O by a user interrupt
44850 (@samp{Ctrl-C}) within @value{GDBN}.
44852 The target's request to perform a host system call does not finish
44853 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44854 after finishing the system call, the target returns to continuing the
44855 previous activity (continue, step). No additional continue or step
44856 request from @value{GDBN} is required.
44859 (@value{GDBP}) continue
44860 <- target requests 'system call X'
44861 target is stopped, @value{GDBN} executes system call
44862 -> @value{GDBN} returns result
44863 ... target continues, @value{GDBN} returns to wait for the target
44864 <- target hits breakpoint and sends a Txx packet
44867 The protocol only supports I/O on the console and to regular files on
44868 the host file system. Character or block special devices, pipes,
44869 named pipes, sockets or any other communication method on the host
44870 system are not supported by this protocol.
44872 File I/O is not supported in non-stop mode.
44874 @node Protocol Basics
44875 @subsection Protocol Basics
44876 @cindex protocol basics, file-i/o
44878 The File-I/O protocol uses the @code{F} packet as the request as well
44879 as reply packet. Since a File-I/O system call can only occur when
44880 @value{GDBN} is waiting for a response from the continuing or stepping target,
44881 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44882 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44883 This @code{F} packet contains all information needed to allow @value{GDBN}
44884 to call the appropriate host system call:
44888 A unique identifier for the requested system call.
44891 All parameters to the system call. Pointers are given as addresses
44892 in the target memory address space. Pointers to strings are given as
44893 pointer/length pair. Numerical values are given as they are.
44894 Numerical control flags are given in a protocol-specific representation.
44898 At this point, @value{GDBN} has to perform the following actions.
44902 If the parameters include pointer values to data needed as input to a
44903 system call, @value{GDBN} requests this data from the target with a
44904 standard @code{m} packet request. This additional communication has to be
44905 expected by the target implementation and is handled as any other @code{m}
44909 @value{GDBN} translates all value from protocol representation to host
44910 representation as needed. Datatypes are coerced into the host types.
44913 @value{GDBN} calls the system call.
44916 It then coerces datatypes back to protocol representation.
44919 If the system call is expected to return data in buffer space specified
44920 by pointer parameters to the call, the data is transmitted to the
44921 target using a @code{M} or @code{X} packet. This packet has to be expected
44922 by the target implementation and is handled as any other @code{M} or @code{X}
44927 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44928 necessary information for the target to continue. This at least contains
44935 @code{errno}, if has been changed by the system call.
44942 After having done the needed type and value coercion, the target continues
44943 the latest continue or step action.
44945 @node The F Request Packet
44946 @subsection The @code{F} Request Packet
44947 @cindex file-i/o request packet
44948 @cindex @code{F} request packet
44950 The @code{F} request packet has the following format:
44953 @item F@var{call-id},@var{parameter@dots{}}
44955 @var{call-id} is the identifier to indicate the host system call to be called.
44956 This is just the name of the function.
44958 @var{parameter@dots{}} are the parameters to the system call.
44959 Parameters are hexadecimal integer values, either the actual values in case
44960 of scalar datatypes, pointers to target buffer space in case of compound
44961 datatypes and unspecified memory areas, or pointer/length pairs in case
44962 of string parameters. These are appended to the @var{call-id} as a
44963 comma-delimited list. All values are transmitted in ASCII
44964 string representation, pointer/length pairs separated by a slash.
44970 @node The F Reply Packet
44971 @subsection The @code{F} Reply Packet
44972 @cindex file-i/o reply packet
44973 @cindex @code{F} reply packet
44975 The @code{F} reply packet has the following format:
44979 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44981 @var{retcode} is the return code of the system call as hexadecimal value.
44983 @var{errno} is the @code{errno} set by the call, in protocol-specific
44985 This parameter can be omitted if the call was successful.
44987 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44988 case, @var{errno} must be sent as well, even if the call was successful.
44989 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44996 or, if the call was interrupted before the host call has been performed:
45003 assuming 4 is the protocol-specific representation of @code{EINTR}.
45008 @node The Ctrl-C Message
45009 @subsection The @samp{Ctrl-C} Message
45010 @cindex ctrl-c message, in file-i/o protocol
45012 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
45013 reply packet (@pxref{The F Reply Packet}),
45014 the target should behave as if it had
45015 gotten a break message. The meaning for the target is ``system call
45016 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
45017 (as with a break message) and return to @value{GDBN} with a @code{T02}
45020 It's important for the target to know in which
45021 state the system call was interrupted. There are two possible cases:
45025 The system call hasn't been performed on the host yet.
45028 The system call on the host has been finished.
45032 These two states can be distinguished by the target by the value of the
45033 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
45034 call hasn't been performed. This is equivalent to the @code{EINTR} handling
45035 on POSIX systems. In any other case, the target may presume that the
45036 system call has been finished --- successfully or not --- and should behave
45037 as if the break message arrived right after the system call.
45039 @value{GDBN} must behave reliably. If the system call has not been called
45040 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
45041 @code{errno} in the packet. If the system call on the host has been finished
45042 before the user requests a break, the full action must be finished by
45043 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
45044 The @code{F} packet may only be sent when either nothing has happened
45045 or the full action has been completed.
45048 @subsection Console I/O
45049 @cindex console i/o as part of file-i/o
45051 By default and if not explicitly closed by the target system, the file
45052 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
45053 on the @value{GDBN} console is handled as any other file output operation
45054 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
45055 by @value{GDBN} so that after the target read request from file descriptor
45056 0 all following typing is buffered until either one of the following
45061 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
45063 system call is treated as finished.
45066 The user presses @key{RET}. This is treated as end of input with a trailing
45070 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
45071 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
45075 If the user has typed more characters than fit in the buffer given to
45076 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
45077 either another @code{read(0, @dots{})} is requested by the target, or debugging
45078 is stopped at the user's request.
45081 @node List of Supported Calls
45082 @subsection List of Supported Calls
45083 @cindex list of supported file-i/o calls
45100 @unnumberedsubsubsec open
45101 @cindex open, file-i/o system call
45106 int open(const char *pathname, int flags);
45107 int open(const char *pathname, int flags, mode_t mode);
45111 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
45114 @var{flags} is the bitwise @code{OR} of the following values:
45118 If the file does not exist it will be created. The host
45119 rules apply as far as file ownership and time stamps
45123 When used with @code{O_CREAT}, if the file already exists it is
45124 an error and open() fails.
45127 If the file already exists and the open mode allows
45128 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
45129 truncated to zero length.
45132 The file is opened in append mode.
45135 The file is opened for reading only.
45138 The file is opened for writing only.
45141 The file is opened for reading and writing.
45145 Other bits are silently ignored.
45149 @var{mode} is the bitwise @code{OR} of the following values:
45153 User has read permission.
45156 User has write permission.
45159 Group has read permission.
45162 Group has write permission.
45165 Others have read permission.
45168 Others have write permission.
45172 Other bits are silently ignored.
45175 @item Return value:
45176 @code{open} returns the new file descriptor or -1 if an error
45183 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
45186 @var{pathname} refers to a directory.
45189 The requested access is not allowed.
45192 @var{pathname} was too long.
45195 A directory component in @var{pathname} does not exist.
45198 @var{pathname} refers to a device, pipe, named pipe or socket.
45201 @var{pathname} refers to a file on a read-only filesystem and
45202 write access was requested.
45205 @var{pathname} is an invalid pointer value.
45208 No space on device to create the file.
45211 The process already has the maximum number of files open.
45214 The limit on the total number of files open on the system
45218 The call was interrupted by the user.
45224 @unnumberedsubsubsec close
45225 @cindex close, file-i/o system call
45234 @samp{Fclose,@var{fd}}
45236 @item Return value:
45237 @code{close} returns zero on success, or -1 if an error occurred.
45243 @var{fd} isn't a valid open file descriptor.
45246 The call was interrupted by the user.
45252 @unnumberedsubsubsec read
45253 @cindex read, file-i/o system call
45258 int read(int fd, void *buf, unsigned int count);
45262 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
45264 @item Return value:
45265 On success, the number of bytes read is returned.
45266 Zero indicates end of file. If count is zero, read
45267 returns zero as well. On error, -1 is returned.
45273 @var{fd} is not a valid file descriptor or is not open for
45277 @var{bufptr} is an invalid pointer value.
45280 The call was interrupted by the user.
45286 @unnumberedsubsubsec write
45287 @cindex write, file-i/o system call
45292 int write(int fd, const void *buf, unsigned int count);
45296 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
45298 @item Return value:
45299 On success, the number of bytes written are returned.
45300 Zero indicates nothing was written. On error, -1
45307 @var{fd} is not a valid file descriptor or is not open for
45311 @var{bufptr} is an invalid pointer value.
45314 An attempt was made to write a file that exceeds the
45315 host-specific maximum file size allowed.
45318 No space on device to write the data.
45321 The call was interrupted by the user.
45327 @unnumberedsubsubsec lseek
45328 @cindex lseek, file-i/o system call
45333 long lseek (int fd, long offset, int flag);
45337 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
45339 @var{flag} is one of:
45343 The offset is set to @var{offset} bytes.
45346 The offset is set to its current location plus @var{offset}
45350 The offset is set to the size of the file plus @var{offset}
45354 @item Return value:
45355 On success, the resulting unsigned offset in bytes from
45356 the beginning of the file is returned. Otherwise, a
45357 value of -1 is returned.
45363 @var{fd} is not a valid open file descriptor.
45366 @var{fd} is associated with the @value{GDBN} console.
45369 @var{flag} is not a proper value.
45372 The call was interrupted by the user.
45378 @unnumberedsubsubsec rename
45379 @cindex rename, file-i/o system call
45384 int rename(const char *oldpath, const char *newpath);
45388 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45390 @item Return value:
45391 On success, zero is returned. On error, -1 is returned.
45397 @var{newpath} is an existing directory, but @var{oldpath} is not a
45401 @var{newpath} is a non-empty directory.
45404 @var{oldpath} or @var{newpath} is a directory that is in use by some
45408 An attempt was made to make a directory a subdirectory
45412 A component used as a directory in @var{oldpath} or new
45413 path is not a directory. Or @var{oldpath} is a directory
45414 and @var{newpath} exists but is not a directory.
45417 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45420 No access to the file or the path of the file.
45424 @var{oldpath} or @var{newpath} was too long.
45427 A directory component in @var{oldpath} or @var{newpath} does not exist.
45430 The file is on a read-only filesystem.
45433 The device containing the file has no room for the new
45437 The call was interrupted by the user.
45443 @unnumberedsubsubsec unlink
45444 @cindex unlink, file-i/o system call
45449 int unlink(const char *pathname);
45453 @samp{Funlink,@var{pathnameptr}/@var{len}}
45455 @item Return value:
45456 On success, zero is returned. On error, -1 is returned.
45462 No access to the file or the path of the file.
45465 The system does not allow unlinking of directories.
45468 The file @var{pathname} cannot be unlinked because it's
45469 being used by another process.
45472 @var{pathnameptr} is an invalid pointer value.
45475 @var{pathname} was too long.
45478 A directory component in @var{pathname} does not exist.
45481 A component of the path is not a directory.
45484 The file is on a read-only filesystem.
45487 The call was interrupted by the user.
45493 @unnumberedsubsubsec stat/fstat
45494 @cindex fstat, file-i/o system call
45495 @cindex stat, file-i/o system call
45500 int stat(const char *pathname, struct stat *buf);
45501 int fstat(int fd, struct stat *buf);
45505 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45506 @samp{Ffstat,@var{fd},@var{bufptr}}
45508 @item Return value:
45509 On success, zero is returned. On error, -1 is returned.
45515 @var{fd} is not a valid open file.
45518 A directory component in @var{pathname} does not exist or the
45519 path is an empty string.
45522 A component of the path is not a directory.
45525 @var{pathnameptr} is an invalid pointer value.
45528 No access to the file or the path of the file.
45531 @var{pathname} was too long.
45534 The call was interrupted by the user.
45540 @unnumberedsubsubsec gettimeofday
45541 @cindex gettimeofday, file-i/o system call
45546 int gettimeofday(struct timeval *tv, void *tz);
45550 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45552 @item Return value:
45553 On success, 0 is returned, -1 otherwise.
45559 @var{tz} is a non-NULL pointer.
45562 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45568 @unnumberedsubsubsec isatty
45569 @cindex isatty, file-i/o system call
45574 int isatty(int fd);
45578 @samp{Fisatty,@var{fd}}
45580 @item Return value:
45581 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45587 The call was interrupted by the user.
45592 Note that the @code{isatty} call is treated as a special case: it returns
45593 1 to the target if the file descriptor is attached
45594 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45595 would require implementing @code{ioctl} and would be more complex than
45600 @unnumberedsubsubsec system
45601 @cindex system, file-i/o system call
45606 int system(const char *command);
45610 @samp{Fsystem,@var{commandptr}/@var{len}}
45612 @item Return value:
45613 If @var{len} is zero, the return value indicates whether a shell is
45614 available. A zero return value indicates a shell is not available.
45615 For non-zero @var{len}, the value returned is -1 on error and the
45616 return status of the command otherwise. Only the exit status of the
45617 command is returned, which is extracted from the host's @code{system}
45618 return value by calling @code{WEXITSTATUS(retval)}. In case
45619 @file{/bin/sh} could not be executed, 127 is returned.
45625 The call was interrupted by the user.
45630 @value{GDBN} takes over the full task of calling the necessary host calls
45631 to perform the @code{system} call. The return value of @code{system} on
45632 the host is simplified before it's returned
45633 to the target. Any termination signal information from the child process
45634 is discarded, and the return value consists
45635 entirely of the exit status of the called command.
45637 Due to security concerns, the @code{system} call is by default refused
45638 by @value{GDBN}. The user has to allow this call explicitly with the
45639 @code{set remote system-call-allowed 1} command.
45642 @item set remote system-call-allowed
45643 @kindex set remote system-call-allowed
45644 Control whether to allow the @code{system} calls in the File I/O
45645 protocol for the remote target. The default is zero (disabled).
45647 @item show remote system-call-allowed
45648 @kindex show remote system-call-allowed
45649 Show whether the @code{system} calls are allowed in the File I/O
45653 @node Protocol-specific Representation of Datatypes
45654 @subsection Protocol-specific Representation of Datatypes
45655 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45658 * Integral Datatypes::
45660 * Memory Transfer::
45665 @node Integral Datatypes
45666 @unnumberedsubsubsec Integral Datatypes
45667 @cindex integral datatypes, in file-i/o protocol
45669 The integral datatypes used in the system calls are @code{int},
45670 @code{unsigned int}, @code{long}, @code{unsigned long},
45671 @code{mode_t}, and @code{time_t}.
45673 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45674 implemented as 32 bit values in this protocol.
45676 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45678 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45679 in @file{limits.h}) to allow range checking on host and target.
45681 @code{time_t} datatypes are defined as seconds since the Epoch.
45683 All integral datatypes transferred as part of a memory read or write of a
45684 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45687 @node Pointer Values
45688 @unnumberedsubsubsec Pointer Values
45689 @cindex pointer values, in file-i/o protocol
45691 Pointers to target data are transmitted as they are. An exception
45692 is made for pointers to buffers for which the length isn't
45693 transmitted as part of the function call, namely strings. Strings
45694 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45701 which is a pointer to data of length 18 bytes at position 0x1aaf.
45702 The length is defined as the full string length in bytes, including
45703 the trailing null byte. For example, the string @code{"hello world"}
45704 at address 0x123456 is transmitted as
45710 @node Memory Transfer
45711 @unnumberedsubsubsec Memory Transfer
45712 @cindex memory transfer, in file-i/o protocol
45714 Structured data which is transferred using a memory read or write (for
45715 example, a @code{struct stat}) is expected to be in a protocol-specific format
45716 with all scalar multibyte datatypes being big endian. Translation to
45717 this representation needs to be done both by the target before the @code{F}
45718 packet is sent, and by @value{GDBN} before
45719 it transfers memory to the target. Transferred pointers to structured
45720 data should point to the already-coerced data at any time.
45724 @unnumberedsubsubsec struct stat
45725 @cindex struct stat, in file-i/o protocol
45727 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45728 is defined as follows:
45732 unsigned int st_dev; /* device */
45733 unsigned int st_ino; /* inode */
45734 mode_t st_mode; /* protection */
45735 unsigned int st_nlink; /* number of hard links */
45736 unsigned int st_uid; /* user ID of owner */
45737 unsigned int st_gid; /* group ID of owner */
45738 unsigned int st_rdev; /* device type (if inode device) */
45739 unsigned long st_size; /* total size, in bytes */
45740 unsigned long st_blksize; /* blocksize for filesystem I/O */
45741 unsigned long st_blocks; /* number of blocks allocated */
45742 time_t st_atime; /* time of last access */
45743 time_t st_mtime; /* time of last modification */
45744 time_t st_ctime; /* time of last change */
45748 The integral datatypes conform to the definitions given in the
45749 appropriate section (see @ref{Integral Datatypes}, for details) so this
45750 structure is of size 64 bytes.
45752 The values of several fields have a restricted meaning and/or
45758 A value of 0 represents a file, 1 the console.
45761 No valid meaning for the target. Transmitted unchanged.
45764 Valid mode bits are described in @ref{Constants}. Any other
45765 bits have currently no meaning for the target.
45770 No valid meaning for the target. Transmitted unchanged.
45775 These values have a host and file system dependent
45776 accuracy. Especially on Windows hosts, the file system may not
45777 support exact timing values.
45780 The target gets a @code{struct stat} of the above representation and is
45781 responsible for coercing it to the target representation before
45784 Note that due to size differences between the host, target, and protocol
45785 representations of @code{struct stat} members, these members could eventually
45786 get truncated on the target.
45788 @node struct timeval
45789 @unnumberedsubsubsec struct timeval
45790 @cindex struct timeval, in file-i/o protocol
45792 The buffer of type @code{struct timeval} used by the File-I/O protocol
45793 is defined as follows:
45797 time_t tv_sec; /* second */
45798 long tv_usec; /* microsecond */
45802 The integral datatypes conform to the definitions given in the
45803 appropriate section (see @ref{Integral Datatypes}, for details) so this
45804 structure is of size 8 bytes.
45807 @subsection Constants
45808 @cindex constants, in file-i/o protocol
45810 The following values are used for the constants inside of the
45811 protocol. @value{GDBN} and target are responsible for translating these
45812 values before and after the call as needed.
45823 @unnumberedsubsubsec Open Flags
45824 @cindex open flags, in file-i/o protocol
45826 All values are given in hexadecimal representation.
45838 @node mode_t Values
45839 @unnumberedsubsubsec mode_t Values
45840 @cindex mode_t values, in file-i/o protocol
45842 All values are given in octal representation.
45859 @unnumberedsubsubsec Errno Values
45860 @cindex errno values, in file-i/o protocol
45862 All values are given in decimal representation.
45887 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45888 any error value not in the list of supported error numbers.
45891 @unnumberedsubsubsec Lseek Flags
45892 @cindex lseek flags, in file-i/o protocol
45901 @unnumberedsubsubsec Limits
45902 @cindex limits, in file-i/o protocol
45904 All values are given in decimal representation.
45907 INT_MIN -2147483648
45909 UINT_MAX 4294967295
45910 LONG_MIN -9223372036854775808
45911 LONG_MAX 9223372036854775807
45912 ULONG_MAX 18446744073709551615
45915 @node File-I/O Examples
45916 @subsection File-I/O Examples
45917 @cindex file-i/o examples
45919 Example sequence of a write call, file descriptor 3, buffer is at target
45920 address 0x1234, 6 bytes should be written:
45923 <- @code{Fwrite,3,1234,6}
45924 @emph{request memory read from target}
45927 @emph{return "6 bytes written"}
45931 Example sequence of a read call, file descriptor 3, buffer is at target
45932 address 0x1234, 6 bytes should be read:
45935 <- @code{Fread,3,1234,6}
45936 @emph{request memory write to target}
45937 -> @code{X1234,6:XXXXXX}
45938 @emph{return "6 bytes read"}
45942 Example sequence of a read call, call fails on the host due to invalid
45943 file descriptor (@code{EBADF}):
45946 <- @code{Fread,3,1234,6}
45950 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45954 <- @code{Fread,3,1234,6}
45959 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45963 <- @code{Fread,3,1234,6}
45964 -> @code{X1234,6:XXXXXX}
45968 @node Library List Format
45969 @section Library List Format
45970 @cindex library list format, remote protocol
45972 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45973 same process as your application to manage libraries. In this case,
45974 @value{GDBN} can use the loader's symbol table and normal memory
45975 operations to maintain a list of shared libraries. On other
45976 platforms, the operating system manages loaded libraries.
45977 @value{GDBN} can not retrieve the list of currently loaded libraries
45978 through memory operations, so it uses the @samp{qXfer:libraries:read}
45979 packet (@pxref{qXfer library list read}) instead. The remote stub
45980 queries the target's operating system and reports which libraries
45983 The @samp{qXfer:libraries:read} packet returns an XML document which
45984 lists loaded libraries and their offsets. Each library has an
45985 associated name and one or more segment or section base addresses,
45986 which report where the library was loaded in memory.
45988 For the common case of libraries that are fully linked binaries, the
45989 library should have a list of segments. If the target supports
45990 dynamic linking of a relocatable object file, its library XML element
45991 should instead include a list of allocated sections. The segment or
45992 section bases are start addresses, not relocation offsets; they do not
45993 depend on the library's link-time base addresses.
45995 @value{GDBN} must be linked with the Expat library to support XML
45996 library lists. @xref{Expat}.
45998 A simple memory map, with one loaded library relocated by a single
45999 offset, looks like this:
46003 <library name="/lib/libc.so.6">
46004 <segment address="0x10000000"/>
46009 Another simple memory map, with one loaded library with three
46010 allocated sections (.text, .data, .bss), looks like this:
46014 <library name="sharedlib.o">
46015 <section address="0x10000000"/>
46016 <section address="0x20000000"/>
46017 <section address="0x30000000"/>
46022 The format of a library list is described by this DTD:
46025 <!-- library-list: Root element with versioning -->
46026 <!ELEMENT library-list (library)*>
46027 <!ATTLIST library-list version CDATA #FIXED "1.0">
46028 <!ELEMENT library (segment*, section*)>
46029 <!ATTLIST library name CDATA #REQUIRED>
46030 <!ELEMENT segment EMPTY>
46031 <!ATTLIST segment address CDATA #REQUIRED>
46032 <!ELEMENT section EMPTY>
46033 <!ATTLIST section address CDATA #REQUIRED>
46036 In addition, segments and section descriptors cannot be mixed within a
46037 single library element, and you must supply at least one segment or
46038 section for each library.
46040 @node Library List Format for SVR4 Targets
46041 @section Library List Format for SVR4 Targets
46042 @cindex library list format, remote protocol
46044 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
46045 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
46046 shared libraries. Still a special library list provided by this packet is
46047 more efficient for the @value{GDBN} remote protocol.
46049 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
46050 loaded libraries and their SVR4 linker parameters. For each library on SVR4
46051 target, the following parameters are reported:
46055 @code{name}, the absolute file name from the @code{l_name} field of
46056 @code{struct link_map}.
46058 @code{lm} with address of @code{struct link_map} used for TLS
46059 (Thread Local Storage) access.
46061 @code{l_addr}, the displacement as read from the field @code{l_addr} of
46062 @code{struct link_map}. For prelinked libraries this is not an absolute
46063 memory address. It is a displacement of absolute memory address against
46064 address the file was prelinked to during the library load.
46066 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
46069 Additionally the single @code{main-lm} attribute specifies address of
46070 @code{struct link_map} used for the main executable. This parameter is used
46071 for TLS access and its presence is optional.
46073 @value{GDBN} must be linked with the Expat library to support XML
46074 SVR4 library lists. @xref{Expat}.
46076 A simple memory map, with two loaded libraries (which do not use prelink),
46080 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
46081 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
46083 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
46085 </library-list-svr>
46088 The format of an SVR4 library list is described by this DTD:
46091 <!-- library-list-svr4: Root element with versioning -->
46092 <!ELEMENT library-list-svr4 (library)*>
46093 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
46094 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
46095 <!ELEMENT library EMPTY>
46096 <!ATTLIST library name CDATA #REQUIRED>
46097 <!ATTLIST library lm CDATA #REQUIRED>
46098 <!ATTLIST library l_addr CDATA #REQUIRED>
46099 <!ATTLIST library l_ld CDATA #REQUIRED>
46102 @node Memory Map Format
46103 @section Memory Map Format
46104 @cindex memory map format
46106 To be able to write into flash memory, @value{GDBN} needs to obtain a
46107 memory map from the target. This section describes the format of the
46110 The memory map is obtained using the @samp{qXfer:memory-map:read}
46111 (@pxref{qXfer memory map read}) packet and is an XML document that
46112 lists memory regions.
46114 @value{GDBN} must be linked with the Expat library to support XML
46115 memory maps. @xref{Expat}.
46117 The top-level structure of the document is shown below:
46120 <?xml version="1.0"?>
46121 <!DOCTYPE memory-map
46122 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46123 "http://sourceware.org/gdb/gdb-memory-map.dtd">
46129 Each region can be either:
46134 A region of RAM starting at @var{addr} and extending for @var{length}
46138 <memory type="ram" start="@var{addr}" length="@var{length}"/>
46143 A region of read-only memory:
46146 <memory type="rom" start="@var{addr}" length="@var{length}"/>
46151 A region of flash memory, with erasure blocks @var{blocksize}
46155 <memory type="flash" start="@var{addr}" length="@var{length}">
46156 <property name="blocksize">@var{blocksize}</property>
46162 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
46163 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
46164 packets to write to addresses in such ranges.
46166 The formal DTD for memory map format is given below:
46169 <!-- ................................................... -->
46170 <!-- Memory Map XML DTD ................................ -->
46171 <!-- File: memory-map.dtd .............................. -->
46172 <!-- .................................... .............. -->
46173 <!-- memory-map.dtd -->
46174 <!-- memory-map: Root element with versioning -->
46175 <!ELEMENT memory-map (memory)*>
46176 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
46177 <!ELEMENT memory (property)*>
46178 <!-- memory: Specifies a memory region,
46179 and its type, or device. -->
46180 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
46181 start CDATA #REQUIRED
46182 length CDATA #REQUIRED>
46183 <!-- property: Generic attribute tag -->
46184 <!ELEMENT property (#PCDATA | property)*>
46185 <!ATTLIST property name (blocksize) #REQUIRED>
46188 @node Thread List Format
46189 @section Thread List Format
46190 @cindex thread list format
46192 To efficiently update the list of threads and their attributes,
46193 @value{GDBN} issues the @samp{qXfer:threads:read} packet
46194 (@pxref{qXfer threads read}) and obtains the XML document with
46195 the following structure:
46198 <?xml version="1.0"?>
46200 <thread id="id" core="0" name="name">
46201 ... description ...
46206 Each @samp{thread} element must have the @samp{id} attribute that
46207 identifies the thread (@pxref{thread-id syntax}). The
46208 @samp{core} attribute, if present, specifies which processor core
46209 the thread was last executing on. The @samp{name} attribute, if
46210 present, specifies the human-readable name of the thread. The content
46211 of the of @samp{thread} element is interpreted as human-readable
46212 auxiliary information. The @samp{handle} attribute, if present,
46213 is a hex encoded representation of the thread handle.
46216 @node Traceframe Info Format
46217 @section Traceframe Info Format
46218 @cindex traceframe info format
46220 To be able to know which objects in the inferior can be examined when
46221 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
46222 memory ranges, registers and trace state variables that have been
46223 collected in a traceframe.
46225 This list is obtained using the @samp{qXfer:traceframe-info:read}
46226 (@pxref{qXfer traceframe info read}) packet and is an XML document.
46228 @value{GDBN} must be linked with the Expat library to support XML
46229 traceframe info discovery. @xref{Expat}.
46231 The top-level structure of the document is shown below:
46234 <?xml version="1.0"?>
46235 <!DOCTYPE traceframe-info
46236 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46237 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
46243 Each traceframe block can be either:
46248 A region of collected memory starting at @var{addr} and extending for
46249 @var{length} bytes from there:
46252 <memory start="@var{addr}" length="@var{length}"/>
46256 A block indicating trace state variable numbered @var{number} has been
46260 <tvar id="@var{number}"/>
46265 The formal DTD for the traceframe info format is given below:
46268 <!ELEMENT traceframe-info (memory | tvar)* >
46269 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
46271 <!ELEMENT memory EMPTY>
46272 <!ATTLIST memory start CDATA #REQUIRED
46273 length CDATA #REQUIRED>
46275 <!ATTLIST tvar id CDATA #REQUIRED>
46278 @node Branch Trace Format
46279 @section Branch Trace Format
46280 @cindex branch trace format
46282 In order to display the branch trace of an inferior thread,
46283 @value{GDBN} needs to obtain the list of branches. This list is
46284 represented as list of sequential code blocks that are connected via
46285 branches. The code in each block has been executed sequentially.
46287 This list is obtained using the @samp{qXfer:btrace:read}
46288 (@pxref{qXfer btrace read}) packet and is an XML document.
46290 @value{GDBN} must be linked with the Expat library to support XML
46291 traceframe info discovery. @xref{Expat}.
46293 The top-level structure of the document is shown below:
46296 <?xml version="1.0"?>
46298 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
46299 "http://sourceware.org/gdb/gdb-btrace.dtd">
46308 A block of sequentially executed instructions starting at @var{begin}
46309 and ending at @var{end}:
46312 <block begin="@var{begin}" end="@var{end}"/>
46317 The formal DTD for the branch trace format is given below:
46320 <!ELEMENT btrace (block* | pt) >
46321 <!ATTLIST btrace version CDATA #FIXED "1.0">
46323 <!ELEMENT block EMPTY>
46324 <!ATTLIST block begin CDATA #REQUIRED
46325 end CDATA #REQUIRED>
46327 <!ELEMENT pt (pt-config?, raw?)>
46329 <!ELEMENT pt-config (cpu?)>
46331 <!ELEMENT cpu EMPTY>
46332 <!ATTLIST cpu vendor CDATA #REQUIRED
46333 family CDATA #REQUIRED
46334 model CDATA #REQUIRED
46335 stepping CDATA #REQUIRED>
46337 <!ELEMENT raw (#PCDATA)>
46340 @node Branch Trace Configuration Format
46341 @section Branch Trace Configuration Format
46342 @cindex branch trace configuration format
46344 For each inferior thread, @value{GDBN} can obtain the branch trace
46345 configuration using the @samp{qXfer:btrace-conf:read}
46346 (@pxref{qXfer btrace-conf read}) packet.
46348 The configuration describes the branch trace format and configuration
46349 settings for that format. The following information is described:
46353 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
46356 The size of the @acronym{BTS} ring buffer in bytes.
46359 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46363 The size of the @acronym{Intel PT} ring buffer in bytes.
46367 @value{GDBN} must be linked with the Expat library to support XML
46368 branch trace configuration discovery. @xref{Expat}.
46370 The formal DTD for the branch trace configuration format is given below:
46373 <!ELEMENT btrace-conf (bts?, pt?)>
46374 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46376 <!ELEMENT bts EMPTY>
46377 <!ATTLIST bts size CDATA #IMPLIED>
46379 <!ELEMENT pt EMPTY>
46380 <!ATTLIST pt size CDATA #IMPLIED>
46383 @include agentexpr.texi
46385 @node Target Descriptions
46386 @appendix Target Descriptions
46387 @cindex target descriptions
46389 One of the challenges of using @value{GDBN} to debug embedded systems
46390 is that there are so many minor variants of each processor
46391 architecture in use. It is common practice for vendors to start with
46392 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46393 and then make changes to adapt it to a particular market niche. Some
46394 architectures have hundreds of variants, available from dozens of
46395 vendors. This leads to a number of problems:
46399 With so many different customized processors, it is difficult for
46400 the @value{GDBN} maintainers to keep up with the changes.
46402 Since individual variants may have short lifetimes or limited
46403 audiences, it may not be worthwhile to carry information about every
46404 variant in the @value{GDBN} source tree.
46406 When @value{GDBN} does support the architecture of the embedded system
46407 at hand, the task of finding the correct architecture name to give the
46408 @command{set architecture} command can be error-prone.
46411 To address these problems, the @value{GDBN} remote protocol allows a
46412 target system to not only identify itself to @value{GDBN}, but to
46413 actually describe its own features. This lets @value{GDBN} support
46414 processor variants it has never seen before --- to the extent that the
46415 descriptions are accurate, and that @value{GDBN} understands them.
46417 @value{GDBN} must be linked with the Expat library to support XML
46418 target descriptions. @xref{Expat}.
46421 * Retrieving Descriptions:: How descriptions are fetched from a target.
46422 * Target Description Format:: The contents of a target description.
46423 * Predefined Target Types:: Standard types available for target
46425 * Enum Target Types:: How to define enum target types.
46426 * Standard Target Features:: Features @value{GDBN} knows about.
46429 @node Retrieving Descriptions
46430 @section Retrieving Descriptions
46432 Target descriptions can be read from the target automatically, or
46433 specified by the user manually. The default behavior is to read the
46434 description from the target. @value{GDBN} retrieves it via the remote
46435 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46436 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46437 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46438 XML document, of the form described in @ref{Target Description
46441 Alternatively, you can specify a file to read for the target description.
46442 If a file is set, the target will not be queried. The commands to
46443 specify a file are:
46446 @cindex set tdesc filename
46447 @item set tdesc filename @var{path}
46448 Read the target description from @var{path}.
46450 @cindex unset tdesc filename
46451 @item unset tdesc filename
46452 Do not read the XML target description from a file. @value{GDBN}
46453 will use the description supplied by the current target.
46455 @cindex show tdesc filename
46456 @item show tdesc filename
46457 Show the filename to read for a target description, if any.
46461 @node Target Description Format
46462 @section Target Description Format
46463 @cindex target descriptions, XML format
46465 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46466 document which complies with the Document Type Definition provided in
46467 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46468 means you can use generally available tools like @command{xmllint} to
46469 check that your feature descriptions are well-formed and valid.
46470 However, to help people unfamiliar with XML write descriptions for
46471 their targets, we also describe the grammar here.
46473 Target descriptions can identify the architecture of the remote target
46474 and (for some architectures) provide information about custom register
46475 sets. They can also identify the OS ABI of the remote target.
46476 @value{GDBN} can use this information to autoconfigure for your
46477 target, or to warn you if you connect to an unsupported target.
46479 Here is a simple target description:
46482 <target version="1.0">
46483 <architecture>i386:x86-64</architecture>
46488 This minimal description only says that the target uses
46489 the x86-64 architecture.
46491 A target description has the following overall form, with [ ] marking
46492 optional elements and @dots{} marking repeatable elements. The elements
46493 are explained further below.
46496 <?xml version="1.0"?>
46497 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46498 <target version="1.0">
46499 @r{[}@var{architecture}@r{]}
46500 @r{[}@var{osabi}@r{]}
46501 @r{[}@var{compatible}@r{]}
46502 @r{[}@var{feature}@dots{}@r{]}
46507 The description is generally insensitive to whitespace and line
46508 breaks, under the usual common-sense rules. The XML version
46509 declaration and document type declaration can generally be omitted
46510 (@value{GDBN} does not require them), but specifying them may be
46511 useful for XML validation tools. The @samp{version} attribute for
46512 @samp{<target>} may also be omitted, but we recommend
46513 including it; if future versions of @value{GDBN} use an incompatible
46514 revision of @file{gdb-target.dtd}, they will detect and report
46515 the version mismatch.
46517 @subsection Inclusion
46518 @cindex target descriptions, inclusion
46521 @cindex <xi:include>
46524 It can sometimes be valuable to split a target description up into
46525 several different annexes, either for organizational purposes, or to
46526 share files between different possible target descriptions. You can
46527 divide a description into multiple files by replacing any element of
46528 the target description with an inclusion directive of the form:
46531 <xi:include href="@var{document}"/>
46535 When @value{GDBN} encounters an element of this form, it will retrieve
46536 the named XML @var{document}, and replace the inclusion directive with
46537 the contents of that document. If the current description was read
46538 using @samp{qXfer}, then so will be the included document;
46539 @var{document} will be interpreted as the name of an annex. If the
46540 current description was read from a file, @value{GDBN} will look for
46541 @var{document} as a file in the same directory where it found the
46542 original description.
46544 @subsection Architecture
46545 @cindex <architecture>
46547 An @samp{<architecture>} element has this form:
46550 <architecture>@var{arch}</architecture>
46553 @var{arch} is one of the architectures from the set accepted by
46554 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46557 @cindex @code{<osabi>}
46559 This optional field was introduced in @value{GDBN} version 7.0.
46560 Previous versions of @value{GDBN} ignore it.
46562 An @samp{<osabi>} element has this form:
46565 <osabi>@var{abi-name}</osabi>
46568 @var{abi-name} is an OS ABI name from the same selection accepted by
46569 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46571 @subsection Compatible Architecture
46572 @cindex @code{<compatible>}
46574 This optional field was introduced in @value{GDBN} version 7.0.
46575 Previous versions of @value{GDBN} ignore it.
46577 A @samp{<compatible>} element has this form:
46580 <compatible>@var{arch}</compatible>
46583 @var{arch} is one of the architectures from the set accepted by
46584 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46586 A @samp{<compatible>} element is used to specify that the target
46587 is able to run binaries in some other than the main target architecture
46588 given by the @samp{<architecture>} element. For example, on the
46589 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46590 or @code{powerpc:common64}, but the system is able to run binaries
46591 in the @code{spu} architecture as well. The way to describe this
46592 capability with @samp{<compatible>} is as follows:
46595 <architecture>powerpc:common</architecture>
46596 <compatible>spu</compatible>
46599 @subsection Features
46602 Each @samp{<feature>} describes some logical portion of the target
46603 system. Features are currently used to describe available CPU
46604 registers and the types of their contents. A @samp{<feature>} element
46608 <feature name="@var{name}">
46609 @r{[}@var{type}@dots{}@r{]}
46615 Each feature's name should be unique within the description. The name
46616 of a feature does not matter unless @value{GDBN} has some special
46617 knowledge of the contents of that feature; if it does, the feature
46618 should have its standard name. @xref{Standard Target Features}.
46622 Any register's value is a collection of bits which @value{GDBN} must
46623 interpret. The default interpretation is a two's complement integer,
46624 but other types can be requested by name in the register description.
46625 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46626 Target Types}), and the description can define additional composite
46629 Each type element must have an @samp{id} attribute, which gives
46630 a unique (within the containing @samp{<feature>}) name to the type.
46631 Types must be defined before they are used.
46634 Some targets offer vector registers, which can be treated as arrays
46635 of scalar elements. These types are written as @samp{<vector>} elements,
46636 specifying the array element type, @var{type}, and the number of elements,
46640 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46644 If a register's value is usefully viewed in multiple ways, define it
46645 with a union type containing the useful representations. The
46646 @samp{<union>} element contains one or more @samp{<field>} elements,
46647 each of which has a @var{name} and a @var{type}:
46650 <union id="@var{id}">
46651 <field name="@var{name}" type="@var{type}"/>
46658 If a register's value is composed from several separate values, define
46659 it with either a structure type or a flags type.
46660 A flags type may only contain bitfields.
46661 A structure type may either contain only bitfields or contain no bitfields.
46662 If the value contains only bitfields, its total size in bytes must be
46665 Non-bitfield values have a @var{name} and @var{type}.
46668 <struct id="@var{id}">
46669 <field name="@var{name}" type="@var{type}"/>
46674 Both @var{name} and @var{type} values are required.
46675 No implicit padding is added.
46677 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46680 <struct id="@var{id}" size="@var{size}">
46681 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46687 <flags id="@var{id}" size="@var{size}">
46688 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46693 The @var{name} value is required.
46694 Bitfield values may be named with the empty string, @samp{""},
46695 in which case the field is ``filler'' and its value is not printed.
46696 Not all bits need to be specified, so ``filler'' fields are optional.
46698 The @var{start} and @var{end} values are required, and @var{type}
46700 The field's @var{start} must be less than or equal to its @var{end},
46701 and zero represents the least significant bit.
46703 The default value of @var{type} is @code{bool} for single bit fields,
46704 and an unsigned integer otherwise.
46706 Which to choose? Structures or flags?
46708 Registers defined with @samp{flags} have these advantages over
46709 defining them with @samp{struct}:
46713 Arithmetic may be performed on them as if they were integers.
46715 They are printed in a more readable fashion.
46718 Registers defined with @samp{struct} have one advantage over
46719 defining them with @samp{flags}:
46723 One can fetch individual fields like in @samp{C}.
46726 (gdb) print $my_struct_reg.field3
46732 @subsection Registers
46735 Each register is represented as an element with this form:
46738 <reg name="@var{name}"
46739 bitsize="@var{size}"
46740 @r{[}regnum="@var{num}"@r{]}
46741 @r{[}save-restore="@var{save-restore}"@r{]}
46742 @r{[}type="@var{type}"@r{]}
46743 @r{[}group="@var{group}"@r{]}/>
46747 The components are as follows:
46752 The register's name; it must be unique within the target description.
46755 The register's size, in bits.
46758 The register's number. If omitted, a register's number is one greater
46759 than that of the previous register (either in the current feature or in
46760 a preceding feature); the first register in the target description
46761 defaults to zero. This register number is used to read or write
46762 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46763 packets, and registers appear in the @code{g} and @code{G} packets
46764 in order of increasing register number.
46767 Whether the register should be preserved across inferior function
46768 calls; this must be either @code{yes} or @code{no}. The default is
46769 @code{yes}, which is appropriate for most registers except for
46770 some system control registers; this is not related to the target's
46774 The type of the register. It may be a predefined type, a type
46775 defined in the current feature, or one of the special types @code{int}
46776 and @code{float}. @code{int} is an integer type of the correct size
46777 for @var{bitsize}, and @code{float} is a floating point type (in the
46778 architecture's normal floating point format) of the correct size for
46779 @var{bitsize}. The default is @code{int}.
46782 The register group to which this register belongs. It can be one of the
46783 standard register groups @code{general}, @code{float}, @code{vector} or an
46784 arbitrary string. Group names should be limited to alphanumeric characters.
46785 If a group name is made up of multiple words the words may be separated by
46786 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46787 @var{group} is specified, @value{GDBN} will not display the register in
46788 @code{info registers}.
46792 @node Predefined Target Types
46793 @section Predefined Target Types
46794 @cindex target descriptions, predefined types
46796 Type definitions in the self-description can build up composite types
46797 from basic building blocks, but can not define fundamental types. Instead,
46798 standard identifiers are provided by @value{GDBN} for the fundamental
46799 types. The currently supported types are:
46804 Boolean type, occupying a single bit.
46812 Signed integer types holding the specified number of bits.
46820 Unsigned integer types holding the specified number of bits.
46824 Pointers to unspecified code and data. The program counter and
46825 any dedicated return address register may be marked as code
46826 pointers; printing a code pointer converts it into a symbolic
46827 address. The stack pointer and any dedicated address registers
46828 may be marked as data pointers.
46831 Half precision IEEE floating point.
46834 Single precision IEEE floating point.
46837 Double precision IEEE floating point.
46840 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46843 The 12-byte extended precision format used by ARM FPA registers.
46846 The 10-byte extended precision format used by x87 registers.
46849 32bit @sc{eflags} register used by x86.
46852 32bit @sc{mxcsr} register used by x86.
46856 @node Enum Target Types
46857 @section Enum Target Types
46858 @cindex target descriptions, enum types
46860 Enum target types are useful in @samp{struct} and @samp{flags}
46861 register descriptions. @xref{Target Description Format}.
46863 Enum types have a name, size and a list of name/value pairs.
46866 <enum id="@var{id}" size="@var{size}">
46867 <evalue name="@var{name}" value="@var{value}"/>
46872 Enums must be defined before they are used.
46875 <enum id="levels_type" size="4">
46876 <evalue name="low" value="0"/>
46877 <evalue name="high" value="1"/>
46879 <flags id="flags_type" size="4">
46880 <field name="X" start="0"/>
46881 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46883 <reg name="flags" bitsize="32" type="flags_type"/>
46886 Given that description, a value of 3 for the @samp{flags} register
46887 would be printed as:
46890 (gdb) info register flags
46891 flags 0x3 [ X LEVEL=high ]
46894 @node Standard Target Features
46895 @section Standard Target Features
46896 @cindex target descriptions, standard features
46898 A target description must contain either no registers or all the
46899 target's registers. If the description contains no registers, then
46900 @value{GDBN} will assume a default register layout, selected based on
46901 the architecture. If the description contains any registers, the
46902 default layout will not be used; the standard registers must be
46903 described in the target description, in such a way that @value{GDBN}
46904 can recognize them.
46906 This is accomplished by giving specific names to feature elements
46907 which contain standard registers. @value{GDBN} will look for features
46908 with those names and verify that they contain the expected registers;
46909 if any known feature is missing required registers, or if any required
46910 feature is missing, @value{GDBN} will reject the target
46911 description. You can add additional registers to any of the
46912 standard features --- @value{GDBN} will display them just as if
46913 they were added to an unrecognized feature.
46915 This section lists the known features and their expected contents.
46916 Sample XML documents for these features are included in the
46917 @value{GDBN} source tree, in the directory @file{gdb/features}.
46919 Names recognized by @value{GDBN} should include the name of the
46920 company or organization which selected the name, and the overall
46921 architecture to which the feature applies; so e.g.@: the feature
46922 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46924 The names of registers are not case sensitive for the purpose
46925 of recognizing standard features, but @value{GDBN} will only display
46926 registers using the capitalization used in the description.
46929 * AArch64 Features::
46933 * LoongArch Features::
46934 * MicroBlaze Features::
46938 * Nios II Features::
46939 * OpenRISC 1000 Features::
46940 * PowerPC Features::
46941 * RISC-V Features::
46943 * S/390 and System z Features::
46949 @node AArch64 Features
46950 @subsection AArch64 Features
46951 @cindex target descriptions, AArch64 features
46953 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46954 targets. It should contain registers @samp{x0} through @samp{x30},
46955 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46957 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46958 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46961 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46962 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46963 through @samp{p15}, @samp{ffr} and @samp{vg}.
46965 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46966 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46969 @subsection ARC Features
46970 @cindex target descriptions, ARC Features
46972 ARC processors are so configurable that even core registers and their numbers
46973 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46974 registers, which are important to @value{GDBN}, are not ``core'' registers in
46975 ARC. Therefore, there are two features that their presence is mandatory:
46976 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46978 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46983 @samp{r0} through @samp{r25} for normal register file targets.
46985 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46986 register file targets.
46988 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46989 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46992 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46993 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46994 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46995 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46996 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46997 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46998 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46999 because of their inaccessibility during user space debugging sessions.
47001 Extension core registers @samp{r32} through @samp{r59} are optional and their
47002 existence depends on the configuration. When debugging GNU/Linux applications,
47003 i.e.@: user space debugging, these core registers are not available.
47005 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
47006 is the list of registers pertinent to this feature:
47010 mandatory: @samp{pc} and @samp{status32}.
47012 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
47016 @subsection ARM Features
47017 @cindex target descriptions, ARM features
47019 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
47021 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
47022 @samp{lr}, @samp{pc}, and @samp{cpsr}.
47024 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
47025 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
47026 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
47029 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
47030 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
47032 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
47033 must contain register @samp{vpr}.
47035 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
47036 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
47038 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
47039 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
47040 synthesize the @samp{q} pseudo registers from @samp{d} register
47043 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
47044 it should contain at least registers @samp{wR0} through @samp{wR15} and
47045 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
47046 @samp{wCSSF}, and @samp{wCASF} registers are optional.
47048 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
47049 should contain at least registers @samp{d0} through @samp{d15}. If
47050 they are present, @samp{d16} through @samp{d31} should also be included.
47051 @value{GDBN} will synthesize the single-precision registers from
47052 halves of the double-precision registers.
47054 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
47055 need to contain registers; it instructs @value{GDBN} to display the
47056 VFP double-precision registers as vectors and to synthesize the
47057 quad-precision registers from pairs of double-precision registers.
47058 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
47059 be present and include 32 double-precision registers.
47061 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
47062 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
47063 will track return address signing states and will decorate backtraces using
47064 the [PAC] marker, similar to AArch64's PAC extension.
47065 @xref{AArch64 PAC}.
47067 @node i386 Features
47068 @subsection i386 Features
47069 @cindex target descriptions, i386 features
47071 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
47072 targets. It should describe the following registers:
47076 @samp{eax} through @samp{edi} plus @samp{eip} for i386
47078 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
47080 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
47081 @samp{fs}, @samp{gs}
47083 @samp{st0} through @samp{st7}
47085 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
47086 @samp{foseg}, @samp{fooff} and @samp{fop}
47089 The register sets may be different, depending on the target.
47091 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
47092 describe registers:
47096 @samp{xmm0} through @samp{xmm7} for i386
47098 @samp{xmm0} through @samp{xmm15} for amd64
47103 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
47104 @samp{org.gnu.gdb.i386.sse} feature. It should
47105 describe the upper 128 bits of @sc{ymm} registers:
47109 @samp{ymm0h} through @samp{ymm7h} for i386
47111 @samp{ymm0h} through @samp{ymm15h} for amd64
47114 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
47115 Memory Protection Extension (MPX). It should describe the following registers:
47119 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
47121 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
47124 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
47125 describe a single register, @samp{orig_eax}.
47127 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
47128 describe two system registers: @samp{fs_base} and @samp{gs_base}.
47130 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
47131 @samp{org.gnu.gdb.i386.avx} feature. It should
47132 describe additional @sc{xmm} registers:
47136 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
47139 It should describe the upper 128 bits of additional @sc{ymm} registers:
47143 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
47147 describe the upper 256 bits of @sc{zmm} registers:
47151 @samp{zmm0h} through @samp{zmm7h} for i386.
47153 @samp{zmm0h} through @samp{zmm15h} for amd64.
47157 describe the additional @sc{zmm} registers:
47161 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
47164 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
47165 describe a single register, @samp{pkru}. It is a 32-bit register
47166 valid for i386 and amd64.
47168 @node LoongArch Features
47169 @subsection LoongArch Features
47170 @cindex target descriptions, LoongArch Features
47172 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
47173 targets. It should contain the registers @samp{r0} through @samp{r31},
47174 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
47175 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
47177 The @samp{org.gnu.gdb.loongarch.fpu} feature is optional. If present,
47178 it should contain registers @samp{f0} through @samp{f31}, @samp{fcc},
47181 @node MicroBlaze Features
47182 @subsection MicroBlaze Features
47183 @cindex target descriptions, MicroBlaze features
47185 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
47186 targets. It should contain registers @samp{r0} through @samp{r31},
47187 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
47188 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
47189 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
47191 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
47192 If present, it should contain registers @samp{rshr} and @samp{rslr}
47194 @node MIPS Features
47195 @subsection @acronym{MIPS} Features
47196 @cindex target descriptions, @acronym{MIPS} features
47198 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
47199 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
47200 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
47203 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
47204 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
47205 registers. They may be 32-bit or 64-bit depending on the target.
47207 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
47208 it may be optional in a future version of @value{GDBN}. It should
47209 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
47210 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
47212 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
47213 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
47214 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
47215 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
47217 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
47218 contain a single register, @samp{restart}, which is used by the
47219 Linux kernel to control restartable syscalls.
47221 @node M68K Features
47222 @subsection M68K Features
47223 @cindex target descriptions, M68K features
47226 @item @samp{org.gnu.gdb.m68k.core}
47227 @itemx @samp{org.gnu.gdb.coldfire.core}
47228 @itemx @samp{org.gnu.gdb.fido.core}
47229 One of those features must be always present.
47230 The feature that is present determines which flavor of m68k is
47231 used. The feature that is present should contain registers
47232 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
47233 @samp{sp}, @samp{ps} and @samp{pc}.
47235 @item @samp{org.gnu.gdb.coldfire.fp}
47236 This feature is optional. If present, it should contain registers
47237 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
47240 Note that, despite the fact that this feature's name says
47241 @samp{coldfire}, it is used to describe any floating point registers.
47242 The size of the registers must match the main m68k flavor; so, for
47243 example, if the primary feature is reported as @samp{coldfire}, then
47244 64-bit floating point registers are required.
47247 @node NDS32 Features
47248 @subsection NDS32 Features
47249 @cindex target descriptions, NDS32 features
47251 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
47252 targets. It should contain at least registers @samp{r0} through
47253 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
47256 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
47257 it should contain 64-bit double-precision floating-point registers
47258 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
47259 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
47261 @emph{Note:} The first sixteen 64-bit double-precision floating-point
47262 registers are overlapped with the thirty-two 32-bit single-precision
47263 floating-point registers. The 32-bit single-precision registers, if
47264 not being listed explicitly, will be synthesized from halves of the
47265 overlapping 64-bit double-precision registers. Listing 32-bit
47266 single-precision registers explicitly is deprecated, and the
47267 support to it could be totally removed some day.
47269 @node Nios II Features
47270 @subsection Nios II Features
47271 @cindex target descriptions, Nios II features
47273 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
47274 targets. It should contain the 32 core registers (@samp{zero},
47275 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
47276 @samp{pc}, and the 16 control registers (@samp{status} through
47279 @node OpenRISC 1000 Features
47280 @subsection Openrisc 1000 Features
47281 @cindex target descriptions, OpenRISC 1000 features
47283 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
47284 targets. It should contain the 32 general purpose registers (@samp{r0}
47285 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
47287 @node PowerPC Features
47288 @subsection PowerPC Features
47289 @cindex target descriptions, PowerPC features
47291 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
47292 targets. It should contain registers @samp{r0} through @samp{r31},
47293 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
47294 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
47296 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
47297 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
47299 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
47300 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
47301 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
47302 through @samp{v31} as aliases for the corresponding @samp{vrX}
47305 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
47306 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
47307 combine these registers with the floating point registers (@samp{f0}
47308 through @samp{f31}) and the altivec registers (@samp{vr0} through
47309 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
47310 @samp{vs63}, the set of vector-scalar registers for POWER7.
47311 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
47312 @samp{org.gnu.gdb.power.altivec}.
47314 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
47315 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
47316 @samp{spefscr}. SPE targets should provide 32-bit registers in
47317 @samp{org.gnu.gdb.power.core} and provide the upper halves in
47318 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
47319 these to present registers @samp{ev0} through @samp{ev31} to the
47322 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
47323 contain the 64-bit register @samp{ppr}.
47325 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
47326 contain the 64-bit register @samp{dscr}.
47328 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
47329 contain the 64-bit register @samp{tar}.
47331 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
47332 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
47335 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
47336 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
47337 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
47338 server PMU registers provided by @sc{gnu}/Linux.
47340 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
47341 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
47344 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
47345 contain the checkpointed general-purpose registers @samp{cr0} through
47346 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
47347 @samp{cctr}. These registers may all be either 32-bit or 64-bit
47348 depending on the target. It should also contain the checkpointed
47349 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
47352 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
47353 contain the checkpointed 64-bit floating-point registers @samp{cf0}
47354 through @samp{cf31}, as well as the checkpointed 64-bit register
47357 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
47358 should contain the checkpointed altivec registers @samp{cvr0} through
47359 @samp{cvr31}, all 128-bit wide. It should also contain the
47360 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
47363 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
47364 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
47365 will combine these registers with the checkpointed floating point
47366 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47367 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47368 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47369 @samp{cvs63}. Therefore, this feature requires both
47370 @samp{org.gnu.gdb.power.htm.altivec} and
47371 @samp{org.gnu.gdb.power.htm.fpu}.
47373 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47374 contain the 64-bit checkpointed register @samp{cppr}.
47376 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47377 contain the 64-bit checkpointed register @samp{cdscr}.
47379 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47380 contain the 64-bit checkpointed register @samp{ctar}.
47383 @node RISC-V Features
47384 @subsection RISC-V Features
47385 @cindex target descriptions, RISC-V Features
47387 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47388 targets. It should contain the registers @samp{x0} through
47389 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47390 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47393 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47394 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47395 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47396 architectural register names, or the ABI names can be used.
47398 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47399 it should contain registers that are not backed by real registers on
47400 the target, but are instead virtual, where the register value is
47401 derived from other target state. In many ways these are like
47402 @value{GDBN}s pseudo-registers, except implemented by the target.
47403 Currently the only register expected in this set is the one byte
47404 @samp{priv} register that contains the target's privilege level in the
47405 least significant two bits.
47407 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47408 should contain all of the target's standard CSRs. Standard CSRs are
47409 those defined in the RISC-V specification documents. There is some
47410 overlap between this feature and the fpu feature; the @samp{fflags},
47411 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47412 expectation is that these registers will be in the fpu feature if the
47413 target has floating point hardware, but can be moved into the csr
47414 feature if the target has the floating point control registers, but no
47415 other floating point hardware.
47417 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47418 it should contain registers @samp{v0} through @samp{v31}, all of which
47419 must be the same size. These requirements are based on the v0.10
47420 draft vector extension, as the vector extension is not yet final. In
47421 the event that the register set of the vector extension changes for
47422 the final specification, the requirements given here could change for
47423 future releases of @value{GDBN}.
47426 @subsection RX Features
47427 @cindex target descriptions, RX Features
47429 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47430 targets. It should contain the registers @samp{r0} through
47431 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47432 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47434 @node S/390 and System z Features
47435 @subsection S/390 and System z Features
47436 @cindex target descriptions, S/390 features
47437 @cindex target descriptions, System z features
47439 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47440 System z targets. It should contain the PSW and the 16 general
47441 registers. In particular, System z targets should provide the 64-bit
47442 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47443 S/390 targets should provide the 32-bit versions of these registers.
47444 A System z target that runs in 31-bit addressing mode should provide
47445 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47446 register's upper halves @samp{r0h} through @samp{r15h}, and their
47447 lower halves @samp{r0l} through @samp{r15l}.
47449 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47450 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47453 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47454 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47456 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47457 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47458 targets and 32-bit otherwise. In addition, the feature may contain
47459 the @samp{last_break} register, whose width depends on the addressing
47460 mode, as well as the @samp{system_call} register, which is always
47463 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47464 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47465 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47467 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47468 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47469 combined by @value{GDBN} with the floating point registers @samp{f0}
47470 through @samp{f15} to present the 128-bit wide vector registers
47471 @samp{v0} through @samp{v15}. In addition, this feature should
47472 contain the 128-bit wide vector registers @samp{v16} through
47475 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47476 the 64-bit wide guarded-storage-control registers @samp{gsd},
47477 @samp{gssm}, and @samp{gsepla}.
47479 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47480 the 64-bit wide guarded-storage broadcast control registers
47481 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47483 @node Sparc Features
47484 @subsection Sparc Features
47485 @cindex target descriptions, sparc32 features
47486 @cindex target descriptions, sparc64 features
47487 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47488 targets. It should describe the following registers:
47492 @samp{g0} through @samp{g7}
47494 @samp{o0} through @samp{o7}
47496 @samp{l0} through @samp{l7}
47498 @samp{i0} through @samp{i7}
47501 They may be 32-bit or 64-bit depending on the target.
47503 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47504 targets. It should describe the following registers:
47508 @samp{f0} through @samp{f31}
47510 @samp{f32} through @samp{f62} for sparc64
47513 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47514 targets. It should describe the following registers:
47518 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47519 @samp{fsr}, and @samp{csr} for sparc32
47521 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47525 @node TIC6x Features
47526 @subsection TMS320C6x Features
47527 @cindex target descriptions, TIC6x features
47528 @cindex target descriptions, TMS320C6x features
47529 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47530 targets. It should contain registers @samp{A0} through @samp{A15},
47531 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47533 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47534 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47535 through @samp{B31}.
47537 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47538 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47540 @node Operating System Information
47541 @appendix Operating System Information
47542 @cindex operating system information
47544 Users of @value{GDBN} often wish to obtain information about the state of
47545 the operating system running on the target---for example the list of
47546 processes, or the list of open files. This section describes the
47547 mechanism that makes it possible. This mechanism is similar to the
47548 target features mechanism (@pxref{Target Descriptions}), but focuses
47549 on a different aspect of target.
47551 Operating system information is retrieved from the target via the
47552 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47553 read}). The object name in the request should be @samp{osdata}, and
47554 the @var{annex} identifies the data to be fetched.
47561 @appendixsection Process list
47562 @cindex operating system information, process list
47564 When requesting the process list, the @var{annex} field in the
47565 @samp{qXfer} request should be @samp{processes}. The returned data is
47566 an XML document. The formal syntax of this document is defined in
47567 @file{gdb/features/osdata.dtd}.
47569 An example document is:
47572 <?xml version="1.0"?>
47573 <!DOCTYPE target SYSTEM "osdata.dtd">
47574 <osdata type="processes">
47576 <column name="pid">1</column>
47577 <column name="user">root</column>
47578 <column name="command">/sbin/init</column>
47579 <column name="cores">1,2,3</column>
47584 Each item should include a column whose name is @samp{pid}. The value
47585 of that column should identify the process on the target. The
47586 @samp{user} and @samp{command} columns are optional, and will be
47587 displayed by @value{GDBN}. The @samp{cores} column, if present,
47588 should contain a comma-separated list of cores that this process
47589 is running on. Target may provide additional columns,
47590 which @value{GDBN} currently ignores.
47592 @node Trace File Format
47593 @appendix Trace File Format
47594 @cindex trace file format
47596 The trace file comes in three parts: a header, a textual description
47597 section, and a trace frame section with binary data.
47599 The header has the form @code{\x7fTRACE0\n}. The first byte is
47600 @code{0x7f} so as to indicate that the file contains binary data,
47601 while the @code{0} is a version number that may have different values
47604 The description section consists of multiple lines of @sc{ascii} text
47605 separated by newline characters (@code{0xa}). The lines may include a
47606 variety of optional descriptive or context-setting information, such
47607 as tracepoint definitions or register set size. @value{GDBN} will
47608 ignore any line that it does not recognize. An empty line marks the end
47613 Specifies the size of a register block in bytes. This is equal to the
47614 size of a @code{g} packet payload in the remote protocol. @var{size}
47615 is an ascii decimal number. There should be only one such line in
47616 a single trace file.
47618 @item status @var{status}
47619 Trace status. @var{status} has the same format as a @code{qTStatus}
47620 remote packet reply. There should be only one such line in a single trace
47623 @item tp @var{payload}
47624 Tracepoint definition. The @var{payload} has the same format as
47625 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47626 may take multiple lines of definition, corresponding to the multiple
47629 @item tsv @var{payload}
47630 Trace state variable definition. The @var{payload} has the same format as
47631 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47632 may take multiple lines of definition, corresponding to the multiple
47635 @item tdesc @var{payload}
47636 Target description in XML format. The @var{payload} is a single line of
47637 the XML file. All such lines should be concatenated together to get
47638 the original XML file. This file is in the same format as @code{qXfer}
47639 @code{features} payload, and corresponds to the main @code{target.xml}
47640 file. Includes are not allowed.
47644 The trace frame section consists of a number of consecutive frames.
47645 Each frame begins with a two-byte tracepoint number, followed by a
47646 four-byte size giving the amount of data in the frame. The data in
47647 the frame consists of a number of blocks, each introduced by a
47648 character indicating its type (at least register, memory, and trace
47649 state variable). The data in this section is raw binary, not a
47650 hexadecimal or other encoding; its endianness matches the target's
47653 @c FIXME bi-arch may require endianness/arch info in description section
47656 @item R @var{bytes}
47657 Register block. The number and ordering of bytes matches that of a
47658 @code{g} packet in the remote protocol. Note that these are the
47659 actual bytes, in target order, not a hexadecimal encoding.
47661 @item M @var{address} @var{length} @var{bytes}...
47662 Memory block. This is a contiguous block of memory, at the 8-byte
47663 address @var{address}, with a 2-byte length @var{length}, followed by
47664 @var{length} bytes.
47666 @item V @var{number} @var{value}
47667 Trace state variable block. This records the 8-byte signed value
47668 @var{value} of trace state variable numbered @var{number}.
47672 Future enhancements of the trace file format may include additional types
47675 @node Index Section Format
47676 @appendix @code{.gdb_index} section format
47677 @cindex .gdb_index section format
47678 @cindex index section format
47680 This section documents the index section that is created by @code{save
47681 gdb-index} (@pxref{Index Files}). The index section is
47682 DWARF-specific; some knowledge of DWARF is assumed in this
47685 The mapped index file format is designed to be directly
47686 @code{mmap}able on any architecture. In most cases, a datum is
47687 represented using a little-endian 32-bit integer value, called an
47688 @code{offset_type}. Big endian machines must byte-swap the values
47689 before using them. Exceptions to this rule are noted. The data is
47690 laid out such that alignment is always respected.
47692 A mapped index consists of several areas, laid out in order.
47696 The file header. This is a sequence of values, of @code{offset_type}
47697 unless otherwise noted:
47701 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47702 Version 4 uses a different hashing function from versions 5 and 6.
47703 Version 6 includes symbols for inlined functions, whereas versions 4
47704 and 5 do not. Version 7 adds attributes to the CU indices in the
47705 symbol table. Version 8 specifies that symbols from DWARF type units
47706 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47707 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47709 @value{GDBN} will only read version 4, 5, or 6 indices
47710 by specifying @code{set use-deprecated-index-sections on}.
47711 GDB has a workaround for potentially broken version 7 indices so it is
47712 currently not flagged as deprecated.
47715 The offset, from the start of the file, of the CU list.
47718 The offset, from the start of the file, of the types CU list. Note
47719 that this area can be empty, in which case this offset will be equal
47720 to the next offset.
47723 The offset, from the start of the file, of the address area.
47726 The offset, from the start of the file, of the symbol table.
47729 The offset, from the start of the file, of the constant pool.
47733 The CU list. This is a sequence of pairs of 64-bit little-endian
47734 values, sorted by the CU offset. The first element in each pair is
47735 the offset of a CU in the @code{.debug_info} section. The second
47736 element in each pair is the length of that CU. References to a CU
47737 elsewhere in the map are done using a CU index, which is just the
47738 0-based index into this table. Note that if there are type CUs, then
47739 conceptually CUs and type CUs form a single list for the purposes of
47743 The types CU list. This is a sequence of triplets of 64-bit
47744 little-endian values. In a triplet, the first value is the CU offset,
47745 the second value is the type offset in the CU, and the third value is
47746 the type signature. The types CU list is not sorted.
47749 The address area. The address area consists of a sequence of address
47750 entries. Each address entry has three elements:
47754 The low address. This is a 64-bit little-endian value.
47757 The high address. This is a 64-bit little-endian value. Like
47758 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47761 The CU index. This is an @code{offset_type} value.
47765 The symbol table. This is an open-addressed hash table. The size of
47766 the hash table is always a power of 2.
47768 Each slot in the hash table consists of a pair of @code{offset_type}
47769 values. The first value is the offset of the symbol's name in the
47770 constant pool. The second value is the offset of the CU vector in the
47773 If both values are 0, then this slot in the hash table is empty. This
47774 is ok because while 0 is a valid constant pool index, it cannot be a
47775 valid index for both a string and a CU vector.
47777 The hash value for a table entry is computed by applying an
47778 iterative hash function to the symbol's name. Starting with an
47779 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47780 the string is incorporated into the hash using the formula depending on the
47785 The formula is @code{r = r * 67 + c - 113}.
47787 @item Versions 5 to 7
47788 The formula is @code{r = r * 67 + tolower (c) - 113}.
47791 The terminating @samp{\0} is not incorporated into the hash.
47793 The step size used in the hash table is computed via
47794 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47795 value, and @samp{size} is the size of the hash table. The step size
47796 is used to find the next candidate slot when handling a hash
47799 The names of C@t{++} symbols in the hash table are canonicalized. We
47800 don't currently have a simple description of the canonicalization
47801 algorithm; if you intend to create new index sections, you must read
47805 The constant pool. This is simply a bunch of bytes. It is organized
47806 so that alignment is correct: CU vectors are stored first, followed by
47809 A CU vector in the constant pool is a sequence of @code{offset_type}
47810 values. The first value is the number of CU indices in the vector.
47811 Each subsequent value is the index and symbol attributes of a CU in
47812 the CU list. This element in the hash table is used to indicate which
47813 CUs define the symbol and how the symbol is used.
47814 See below for the format of each CU index+attributes entry.
47816 A string in the constant pool is zero-terminated.
47819 Attributes were added to CU index values in @code{.gdb_index} version 7.
47820 If a symbol has multiple uses within a CU then there is one
47821 CU index+attributes value for each use.
47823 The format of each CU index+attributes entry is as follows
47829 This is the index of the CU in the CU list.
47831 These bits are reserved for future purposes and must be zero.
47833 The kind of the symbol in the CU.
47837 This value is reserved and should not be used.
47838 By reserving zero the full @code{offset_type} value is backwards compatible
47839 with previous versions of the index.
47841 The symbol is a type.
47843 The symbol is a variable or an enum value.
47845 The symbol is a function.
47847 Any other kind of symbol.
47849 These values are reserved.
47853 This bit is zero if the value is global and one if it is static.
47855 The determination of whether a symbol is global or static is complicated.
47856 The authorative reference is the file @file{dwarf2read.c} in
47857 @value{GDBN} sources.
47861 This pseudo-code describes the computation of a symbol's kind and
47862 global/static attributes in the index.
47865 is_external = get_attribute (die, DW_AT_external);
47866 language = get_attribute (cu_die, DW_AT_language);
47869 case DW_TAG_typedef:
47870 case DW_TAG_base_type:
47871 case DW_TAG_subrange_type:
47875 case DW_TAG_enumerator:
47877 is_static = language != CPLUS;
47879 case DW_TAG_subprogram:
47881 is_static = ! (is_external || language == ADA);
47883 case DW_TAG_constant:
47885 is_static = ! is_external;
47887 case DW_TAG_variable:
47889 is_static = ! is_external;
47891 case DW_TAG_namespace:
47895 case DW_TAG_class_type:
47896 case DW_TAG_interface_type:
47897 case DW_TAG_structure_type:
47898 case DW_TAG_union_type:
47899 case DW_TAG_enumeration_type:
47901 is_static = language != CPLUS;
47909 @appendix Download debugging resources with Debuginfod
47912 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47915 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47916 can query servers using the build IDs associated with missing debug info,
47917 executables and source files in order to download them on demand.
47919 For instructions on building @value{GDBN} with @file{libdebuginfod},
47920 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47921 with @code{elfutils}, starting with version 0.178. See
47922 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47923 regarding @code{debuginfod}.
47926 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47929 @node Debuginfod Settings
47930 @section Debuginfod Settings
47932 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47935 @kindex set debuginfod enabled
47936 @anchor{set debuginfod enabled}
47937 @item set debuginfod enabled
47938 @itemx set debuginfod enabled on
47939 @cindex enable debuginfod
47940 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47941 info or source files.
47943 @item set debuginfod enabled off
47944 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47945 debug info or source files. By default, @code{debuginfod enabled} is set to
47946 @code{off} for non-interactive sessions.
47948 @item set debuginfod enabled ask
47949 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47950 attempting to perform the next query. By default, @code{debuginfod enabled}
47951 is set to @code{ask} for interactive sessions.
47953 @kindex show debuginfod enabled
47954 @item show debuginfod enabled
47955 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47958 @kindex set debuginfod urls
47959 @cindex configure debuginfod URLs
47960 @item set debuginfod urls
47961 @itemx set debuginfod urls @var{urls}
47962 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47963 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47964 should be used. The default value of @code{debuginfod urls} is copied from
47965 the @var{DEBUGINFOD_URLS} environment variable.
47967 @kindex show debuginfod urls
47968 @item show debuginfod urls
47969 Display the list of URLs that @code{debuginfod} will attempt to query.
47971 @kindex set debuginfod verbose
47972 @cindex debuginfod verbosity
47973 @item set debuginfod verbose
47974 @itemx set debuginfod verbose @var{n}
47975 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47976 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47979 @kindex show debuginfod verbose
47980 @item show debuginfod verbose
47981 Show the current verbosity setting.
47986 @appendix Manual pages
47990 * gdb man:: The GNU Debugger man page
47991 * gdbserver man:: Remote Server for the GNU Debugger man page
47992 * gcore man:: Generate a core file of a running program
47993 * gdbinit man:: gdbinit scripts
47994 * gdb-add-index man:: Add index files to speed up GDB
48000 @c man title gdb The GNU Debugger
48002 @c man begin SYNOPSIS gdb
48003 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
48006 @c man begin DESCRIPTION gdb
48007 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
48008 going on ``inside'' another program while it executes -- or what another
48009 program was doing at the moment it crashed.
48011 @value{GDBN} can do four main kinds of things (plus other things in support of
48012 these) to help you catch bugs in the act:
48016 Start your program, specifying anything that might affect its behavior.
48019 Make your program stop on specified conditions.
48022 Examine what has happened, when your program has stopped.
48025 Change things in your program, so you can experiment with correcting the
48026 effects of one bug and go on to learn about another.
48029 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
48032 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
48033 commands from the terminal until you tell it to exit with the @value{GDBN}
48034 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
48035 by using the command @code{help}.
48037 You can run @code{gdb} with no arguments or options; but the most
48038 usual way to start @value{GDBN} is with one argument or two, specifying an
48039 executable program as the argument:
48045 You can also start with both an executable program and a core file specified:
48051 You can, instead, specify a process ID as a second argument or use option
48052 @code{-p}, if you want to debug a running process:
48060 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
48061 can omit the @var{program} filename.
48063 Here are some of the most frequently needed @value{GDBN} commands:
48065 @c pod2man highlights the right hand side of the @item lines.
48067 @item break [@var{file}:][@var{function}|@var{line}]
48068 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
48070 @item run [@var{arglist}]
48071 Start your program (with @var{arglist}, if specified).
48074 Backtrace: display the program stack.
48076 @item print @var{expr}
48077 Display the value of an expression.
48080 Continue running your program (after stopping, e.g.@: at a breakpoint).
48083 Execute next program line (after stopping); step @emph{over} any
48084 function calls in the line.
48086 @item edit [@var{file}:]@var{function}
48087 look at the program line where it is presently stopped.
48089 @item list [@var{file}:]@var{function}
48090 type the text of the program in the vicinity of where it is presently stopped.
48093 Execute next program line (after stopping); step @emph{into} any
48094 function calls in the line.
48096 @item help [@var{name}]
48097 Show information about @value{GDBN} command @var{name}, or general information
48098 about using @value{GDBN}.
48102 Exit from @value{GDBN}.
48106 For full details on @value{GDBN},
48107 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48108 by Richard M. Stallman and Roland H. Pesch. The same text is available online
48109 as the @code{gdb} entry in the @code{info} program.
48113 @c man begin OPTIONS gdb
48114 Any arguments other than options specify an executable
48115 file and core file (or process ID); that is, the first argument
48116 encountered with no
48117 associated option flag is equivalent to a @option{--se} option, and the second,
48118 if any, is equivalent to a @option{-c} option if it's the name of a file.
48120 both long and abbreviated forms; both are shown here. The long forms are also
48121 recognized if you truncate them, so long as enough of the option is
48122 present to be unambiguous.
48124 The abbreviated forms are shown here with @samp{-} and long forms are shown
48125 with @samp{--} to reflect how they are shown in @option{--help}. However,
48126 @value{GDBN} recognizes all of the following conventions for most options:
48129 @item --option=@var{value}
48130 @item --option @var{value}
48131 @item -option=@var{value}
48132 @item -option @var{value}
48133 @item --o=@var{value}
48134 @item --o @var{value}
48135 @item -o=@var{value}
48136 @item -o @var{value}
48139 All the options and command line arguments you give are processed
48140 in sequential order. The order makes a difference when the @option{-x}
48146 List all options, with brief explanations.
48148 @item --symbols=@var{file}
48149 @itemx -s @var{file}
48150 Read symbol table from @var{file}.
48153 Enable writing into executable and core files.
48155 @item --exec=@var{file}
48156 @itemx -e @var{file}
48157 Use @var{file} as the executable file to execute when
48158 appropriate, and for examining pure data in conjunction with a core
48161 @item --se=@var{file}
48162 Read symbol table from @var{file} and use it as the executable
48165 @item --core=@var{file}
48166 @itemx -c @var{file}
48167 Use @var{file} as a core dump to examine.
48169 @item --command=@var{file}
48170 @itemx -x @var{file}
48171 Execute @value{GDBN} commands from @var{file}.
48173 @item --eval-command=@var{command}
48174 @item -ex @var{command}
48175 Execute given @value{GDBN} @var{command}.
48177 @item --init-eval-command=@var{command}
48179 Execute @value{GDBN} @var{command} before loading the inferior.
48181 @item --directory=@var{directory}
48182 @itemx -d @var{directory}
48183 Add @var{directory} to the path to search for source files.
48186 Do not execute commands from @file{~/.config/gdb/gdbinit},
48187 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
48188 @file{~/.gdbearlyinit}
48192 Do not execute commands from any @file{.gdbinit} or
48193 @file{.gdbearlyinit} initialization files.
48198 ``Quiet''. Do not print the introductory and copyright messages. These
48199 messages are also suppressed in batch mode.
48202 Run in batch mode. Exit with status @code{0} after processing all the command
48203 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
48204 Exit with nonzero status if an error occurs in executing the @value{GDBN}
48205 commands in the command files.
48207 Batch mode may be useful for running @value{GDBN} as a filter, for example to
48208 download and run a program on another computer; in order to make this
48209 more useful, the message
48212 Program exited normally.
48216 (which is ordinarily issued whenever a program running under @value{GDBN} control
48217 terminates) is not issued when running in batch mode.
48219 @item --batch-silent
48220 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
48221 output is supressed (stderr is unaffected). This is much quieter than
48222 @option{--silent} and would be useless for an interactive session.
48224 This is particularly useful when using targets that give @samp{Loading section}
48225 messages, for example.
48227 Note that targets that give their output via @value{GDBN}, as opposed to writing
48228 directly to @code{stdout}, will also be made silent.
48230 @item --args @var{prog} [@var{arglist}]
48231 Change interpretation of command line so that arguments following this
48232 option are passed as arguments to the inferior. As an example, take
48233 the following command:
48240 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
48241 the other hand, using:
48244 gdb --args ./a.out -q
48248 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
48250 @item --pid=@var{pid}
48251 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
48254 Open the terminal user interface.
48257 Read all symbols from the given symfile on the first access.
48260 Do not read symbol files.
48262 @item --return-child-result
48263 @value{GDBN}'s exit code will be the same as the child's exit code.
48265 @item --configuration
48266 Print details about GDB configuration and then exit.
48269 Print version information and then exit.
48271 @item --cd=@var{directory}
48272 Run @value{GDBN} using @var{directory} as its working directory,
48273 instead of the current directory.
48275 @item --data-directory=@var{directory}
48277 Run @value{GDBN} using @var{directory} as its data directory. The data
48278 directory is where @value{GDBN} searches for its auxiliary files.
48282 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
48283 @value{GDBN} to output the full file name and line number in a standard,
48284 recognizable fashion each time a stack frame is displayed (which
48285 includes each time the program stops). This recognizable format looks
48286 like two @samp{\032} characters, followed by the file name, line number
48287 and character position separated by colons, and a newline. The
48288 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
48289 characters as a signal to display the source code for the frame.
48291 @item -b @var{baudrate}
48292 Set the line speed (baud rate or bits per second) of any serial
48293 interface used by @value{GDBN} for remote debugging.
48295 @item -l @var{timeout}
48296 Set timeout, in seconds, for remote debugging.
48298 @item --tty=@var{device}
48299 Run using @var{device} for your program's standard input and output.
48303 @c man begin SEEALSO gdb
48305 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48306 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48307 documentation are properly installed at your site, the command
48314 should give you access to the complete manual.
48316 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48317 Richard M. Stallman and Roland H. Pesch, July 1991.
48321 @node gdbserver man
48322 @heading gdbserver man
48324 @c man title gdbserver Remote Server for the GNU Debugger
48326 @c man begin SYNOPSIS gdbserver
48327 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48329 gdbserver --attach @var{comm} @var{pid}
48331 gdbserver --multi @var{comm}
48335 @c man begin DESCRIPTION gdbserver
48336 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
48337 than the one which is running the program being debugged.
48340 @subheading Usage (server (target) side)
48343 Usage (server (target) side):
48346 First, you need to have a copy of the program you want to debug put onto
48347 the target system. The program can be stripped to save space if needed, as
48348 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
48349 the @value{GDBN} running on the host system.
48351 To use the server, you log on to the target system, and run the @command{gdbserver}
48352 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
48353 your program, and (c) its arguments. The general syntax is:
48356 target> gdbserver @var{comm} @var{program} [@var{args} ...]
48359 For example, using a serial port, you might say:
48363 @c @file would wrap it as F</dev/com1>.
48364 target> gdbserver /dev/com1 emacs foo.txt
48367 target> gdbserver @file{/dev/com1} emacs foo.txt
48371 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48372 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48373 waits patiently for the host @value{GDBN} to communicate with it.
48375 To use a TCP connection, you could say:
48378 target> gdbserver host:2345 emacs foo.txt
48381 This says pretty much the same thing as the last example, except that we are
48382 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48383 that we are expecting to see a TCP connection from @code{host} to local TCP port
48384 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48385 want for the port number as long as it does not conflict with any existing TCP
48386 ports on the target system. This same port number must be used in the host
48387 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48388 you chose a port number that conflicts with another service, @command{gdbserver} will
48389 print an error message and exit.
48391 @command{gdbserver} can also attach to running programs.
48392 This is accomplished via the @option{--attach} argument. The syntax is:
48395 target> gdbserver --attach @var{comm} @var{pid}
48398 @var{pid} is the process ID of a currently running process. It isn't
48399 necessary to point @command{gdbserver} at a binary for the running process.
48401 To start @code{gdbserver} without supplying an initial command to run
48402 or process ID to attach, use the @option{--multi} command line option.
48403 In such case you should connect using @kbd{target extended-remote} to start
48404 the program you want to debug.
48407 target> gdbserver --multi @var{comm}
48411 @subheading Usage (host side)
48417 You need an unstripped copy of the target program on your host system, since
48418 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48419 would, with the target program as the first argument. (You may need to use the
48420 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48421 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48422 new command you need to know about is @code{target remote}
48423 (or @code{target extended-remote}). Its argument is either
48424 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48425 descriptor. For example:
48429 @c @file would wrap it as F</dev/ttyb>.
48430 (gdb) target remote /dev/ttyb
48433 (gdb) target remote @file{/dev/ttyb}
48438 communicates with the server via serial line @file{/dev/ttyb}, and:
48441 (gdb) target remote the-target:2345
48445 communicates via a TCP connection to port 2345 on host `the-target', where
48446 you previously started up @command{gdbserver} with the same port number. Note that for
48447 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48448 command, otherwise you may get an error that looks something like
48449 `Connection refused'.
48451 @command{gdbserver} can also debug multiple inferiors at once,
48454 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48455 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48458 @ref{Inferiors Connections and Programs}.
48460 In such case use the @code{extended-remote} @value{GDBN} command variant:
48463 (gdb) target extended-remote the-target:2345
48466 The @command{gdbserver} option @option{--multi} may or may not be used in such
48470 @c man begin OPTIONS gdbserver
48471 There are three different modes for invoking @command{gdbserver}:
48476 Debug a specific program specified by its program name:
48479 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48482 The @var{comm} parameter specifies how should the server communicate
48483 with @value{GDBN}; it is either a device name (to use a serial line),
48484 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48485 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48486 debug in @var{prog}. Any remaining arguments will be passed to the
48487 program verbatim. When the program exits, @value{GDBN} will close the
48488 connection, and @code{gdbserver} will exit.
48491 Debug a specific program by specifying the process ID of a running
48495 gdbserver --attach @var{comm} @var{pid}
48498 The @var{comm} parameter is as described above. Supply the process ID
48499 of a running program in @var{pid}; @value{GDBN} will do everything
48500 else. Like with the previous mode, when the process @var{pid} exits,
48501 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48504 Multi-process mode -- debug more than one program/process:
48507 gdbserver --multi @var{comm}
48510 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48511 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48512 close the connection when a process being debugged exits, so you can
48513 debug several processes in the same session.
48516 In each of the modes you may specify these options:
48521 List all options, with brief explanations.
48524 This option causes @command{gdbserver} to print its version number and exit.
48527 @command{gdbserver} will attach to a running program. The syntax is:
48530 target> gdbserver --attach @var{comm} @var{pid}
48533 @var{pid} is the process ID of a currently running process. It isn't
48534 necessary to point @command{gdbserver} at a binary for the running process.
48537 To start @code{gdbserver} without supplying an initial command to run
48538 or process ID to attach, use this command line option.
48539 Then you can connect using @kbd{target extended-remote} and start
48540 the program you want to debug. The syntax is:
48543 target> gdbserver --multi @var{comm}
48547 Instruct @code{gdbserver} to display extra status information about the debugging
48549 This option is intended for @code{gdbserver} development and for bug reports to
48552 @item --remote-debug
48553 Instruct @code{gdbserver} to display remote protocol debug output.
48554 This option is intended for @code{gdbserver} development and for bug reports to
48557 @item --debug-file=@var{filename}
48558 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48559 This option is intended for @code{gdbserver} development and for bug reports to
48562 @item --debug-format=option1@r{[},option2,...@r{]}
48563 Instruct @code{gdbserver} to include extra information in each line
48564 of debugging output.
48565 @xref{Other Command-Line Arguments for gdbserver}.
48568 Specify a wrapper to launch programs
48569 for debugging. The option should be followed by the name of the
48570 wrapper, then any command-line arguments to pass to the wrapper, then
48571 @kbd{--} indicating the end of the wrapper arguments.
48574 By default, @command{gdbserver} keeps the listening TCP port open, so that
48575 additional connections are possible. However, if you start @code{gdbserver}
48576 with the @option{--once} option, it will stop listening for any further
48577 connection attempts after connecting to the first @value{GDBN} session.
48579 @c --disable-packet is not documented for users.
48581 @c --disable-randomization and --no-disable-randomization are superseded by
48582 @c QDisableRandomization.
48587 @c man begin SEEALSO gdbserver
48589 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48590 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48591 documentation are properly installed at your site, the command
48597 should give you access to the complete manual.
48599 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48600 Richard M. Stallman and Roland H. Pesch, July 1991.
48607 @c man title gcore Generate a core file of a running program
48610 @c man begin SYNOPSIS gcore
48611 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48615 @c man begin DESCRIPTION gcore
48616 Generate core dumps of one or more running programs with process IDs
48617 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48618 is equivalent to one produced by the kernel when the process crashes
48619 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48620 limit). However, unlike after a crash, after @command{gcore} finishes
48621 its job the program remains running without any change.
48624 @c man begin OPTIONS gcore
48627 Dump all memory mappings. The actual effect of this option depends on
48628 the Operating System. On @sc{gnu}/Linux, it will disable
48629 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48630 enable @code{dump-excluded-mappings} (@pxref{set
48631 dump-excluded-mappings}).
48633 @item -o @var{prefix}
48634 The optional argument @var{prefix} specifies the prefix to be used
48635 when composing the file names of the core dumps. The file name is
48636 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48637 process ID of the running program being analyzed by @command{gcore}.
48638 If not specified, @var{prefix} defaults to @var{gcore}.
48642 @c man begin SEEALSO gcore
48644 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48645 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48646 documentation are properly installed at your site, the command
48653 should give you access to the complete manual.
48655 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48656 Richard M. Stallman and Roland H. Pesch, July 1991.
48663 @c man title gdbinit GDB initialization scripts
48666 @c man begin SYNOPSIS gdbinit
48667 @ifset SYSTEM_GDBINIT
48668 @value{SYSTEM_GDBINIT}
48671 @ifset SYSTEM_GDBINIT_DIR
48672 @value{SYSTEM_GDBINIT_DIR}/*
48675 ~/.config/gdb/gdbinit
48683 @c man begin DESCRIPTION gdbinit
48684 These files contain @value{GDBN} commands to automatically execute during
48685 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48688 the @value{GDBN} manual in node @code{Sequences}
48689 -- shell command @code{info -f gdb -n Sequences}.
48695 Please read more in
48697 the @value{GDBN} manual in node @code{Startup}
48698 -- shell command @code{info -f gdb -n Startup}.
48705 @ifset SYSTEM_GDBINIT
48706 @item @value{SYSTEM_GDBINIT}
48708 @ifclear SYSTEM_GDBINIT
48709 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48711 System-wide initialization file. It is executed unless user specified
48712 @value{GDBN} option @code{-nx} or @code{-n}.
48715 the @value{GDBN} manual in node @code{System-wide configuration}
48716 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48718 @ifset SYSTEM_GDBINIT_DIR
48719 @item @value{SYSTEM_GDBINIT_DIR}
48721 @ifclear SYSTEM_GDBINIT_DIR
48722 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48724 System-wide initialization directory. All files in this directory are
48725 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48726 @code{-n}, as long as they have a recognized file extension.
48729 the @value{GDBN} manual in node @code{System-wide configuration}
48730 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48733 @ref{System-wide configuration}.
48736 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48737 User initialization file. It is executed unless user specified
48738 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48740 @item @file{.gdbinit}
48741 Initialization file for current directory. It may need to be enabled with
48742 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48745 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48746 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48749 @ref{Init File in the Current Directory}.
48754 @c man begin SEEALSO gdbinit
48756 gdb(1), @code{info -f gdb -n Startup}
48758 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48759 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48760 documentation are properly installed at your site, the command
48766 should give you access to the complete manual.
48768 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48769 Richard M. Stallman and Roland H. Pesch, July 1991.
48773 @node gdb-add-index man
48774 @heading gdb-add-index
48775 @pindex gdb-add-index
48776 @anchor{gdb-add-index}
48778 @c man title gdb-add-index Add index files to speed up GDB
48780 @c man begin SYNOPSIS gdb-add-index
48781 gdb-add-index @var{filename}
48784 @c man begin DESCRIPTION gdb-add-index
48785 When @value{GDBN} finds a symbol file, it scans the symbols in the
48786 file in order to construct an internal symbol table. This lets most
48787 @value{GDBN} operations work quickly--at the cost of a delay early on.
48788 For large programs, this delay can be quite lengthy, so @value{GDBN}
48789 provides a way to build an index, which speeds up startup.
48791 To determine whether a file contains such an index, use the command
48792 @kbd{readelf -S filename}: the index is stored in a section named
48793 @code{.gdb_index}. The index file can only be produced on systems
48794 which use ELF binaries and DWARF debug information (i.e., sections
48795 named @code{.debug_*}).
48797 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48798 in the @env{PATH} environment variable. If you want to use different
48799 versions of these programs, you can specify them through the
48800 @env{GDB} and @env{OBJDUMP} environment variables.
48804 the @value{GDBN} manual in node @code{Index Files}
48805 -- shell command @kbd{info -f gdb -n "Index Files"}.
48812 @c man begin SEEALSO gdb-add-index
48814 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48815 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48816 documentation are properly installed at your site, the command
48822 should give you access to the complete manual.
48824 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48825 Richard M. Stallman and Roland H. Pesch, July 1991.
48831 @node GNU Free Documentation License
48832 @appendix GNU Free Documentation License
48835 @node Concept Index
48836 @unnumbered Concept Index
48840 @node Command and Variable Index
48841 @unnumbered Command, Variable, and Function Index
48846 % I think something like @@colophon should be in texinfo. In the
48848 \long\def\colophon{\hbox to0pt{}\vfill
48849 \centerline{The body of this manual is set in}
48850 \centerline{\fontname\tenrm,}
48851 \centerline{with headings in {\bf\fontname\tenbf}}
48852 \centerline{and examples in {\tt\fontname\tentt}.}
48853 \centerline{{\it\fontname\tenit\/},}
48854 \centerline{{\bf\fontname\tenbf}, and}
48855 \centerline{{\sl\fontname\tensl\/}}
48856 \centerline{are used for emphasis.}\vfill}
48858 % Blame: doc@@cygnus.com, 1991.