1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2021 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{} 1988-2021 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) 1988-2021 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 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
560 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
561 the Linux kernel BPF virtual architecture. This work was sponsored by
565 @chapter A Sample @value{GDBN} Session
567 You can use this manual at your leisure to read all about @value{GDBN}.
568 However, a handful of commands are enough to get started using the
569 debugger. This chapter illustrates those commands.
572 In this sample session, we emphasize user input like this: @b{input},
573 to make it easier to pick out from the surrounding output.
576 @c FIXME: this example may not be appropriate for some configs, where
577 @c FIXME...primary interest is in remote use.
579 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
580 processor) exhibits the following bug: sometimes, when we change its
581 quote strings from the default, the commands used to capture one macro
582 definition within another stop working. In the following short @code{m4}
583 session, we define a macro @code{foo} which expands to @code{0000}; we
584 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
585 same thing. However, when we change the open quote string to
586 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
587 procedure fails to define a new synonym @code{baz}:
596 @b{define(bar,defn(`foo'))}
600 @b{changequote(<QUOTE>,<UNQUOTE>)}
602 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
605 m4: End of input: 0: fatal error: EOF in string
609 Let us use @value{GDBN} to try to see what is going on.
612 $ @b{@value{GDBP} m4}
613 @c FIXME: this falsifies the exact text played out, to permit smallbook
614 @c FIXME... format to come out better.
615 @value{GDBN} is free software and you are welcome to distribute copies
616 of it under certain conditions; type "show copying" to see
618 There is absolutely no warranty for @value{GDBN}; type "show warranty"
621 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
626 @value{GDBN} reads only enough symbol data to know where to find the
627 rest when needed; as a result, the first prompt comes up very quickly.
628 We now tell @value{GDBN} to use a narrower display width than usual, so
629 that examples fit in this manual.
632 (@value{GDBP}) @b{set width 70}
636 We need to see how the @code{m4} built-in @code{changequote} works.
637 Having looked at the source, we know the relevant subroutine is
638 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
639 @code{break} command.
642 (@value{GDBP}) @b{break m4_changequote}
643 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
647 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
648 control; as long as control does not reach the @code{m4_changequote}
649 subroutine, the program runs as usual:
652 (@value{GDBP}) @b{run}
653 Starting program: /work/Editorial/gdb/gnu/m4/m4
661 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
662 suspends execution of @code{m4}, displaying information about the
663 context where it stops.
666 @b{changequote(<QUOTE>,<UNQUOTE>)}
668 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
670 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
674 Now we use the command @code{n} (@code{next}) to advance execution to
675 the next line of the current function.
679 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
684 @code{set_quotes} looks like a promising subroutine. We can go into it
685 by using the command @code{s} (@code{step}) instead of @code{next}.
686 @code{step} goes to the next line to be executed in @emph{any}
687 subroutine, so it steps into @code{set_quotes}.
691 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 530 if (lquote != def_lquote)
697 The display that shows the subroutine where @code{m4} is now
698 suspended (and its arguments) is called a stack frame display. It
699 shows a summary of the stack. We can use the @code{backtrace}
700 command (which can also be spelled @code{bt}), to see where we are
701 in the stack as a whole: the @code{backtrace} command displays a
702 stack frame for each active subroutine.
705 (@value{GDBP}) @b{bt}
706 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
708 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
710 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
711 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
713 #4 0x79dc in expand_input () at macro.c:40
714 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
718 We step through a few more lines to see what happens. The first two
719 times, we can use @samp{s}; the next two times we use @code{n} to avoid
720 falling into the @code{xstrdup} subroutine.
724 0x3b5c 532 if (rquote != def_rquote)
726 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
727 def_lquote : xstrdup(lq);
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
736 The last line displayed looks a little odd; we can examine the variables
737 @code{lquote} and @code{rquote} to see if they are in fact the new left
738 and right quotes we specified. We use the command @code{p}
739 (@code{print}) to see their values.
742 (@value{GDBP}) @b{p lquote}
743 $1 = 0x35d40 "<QUOTE>"
744 (@value{GDBP}) @b{p rquote}
745 $2 = 0x35d50 "<UNQUOTE>"
749 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
750 To look at some context, we can display ten lines of source
751 surrounding the current line with the @code{l} (@code{list}) command.
757 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
759 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
762 538 len_lquote = strlen(rquote);
763 539 len_rquote = strlen(lquote);
770 Let us step past the two lines that set @code{len_lquote} and
771 @code{len_rquote}, and then examine the values of those variables.
775 539 len_rquote = strlen(lquote);
778 (@value{GDBP}) @b{p len_lquote}
780 (@value{GDBP}) @b{p len_rquote}
785 That certainly looks wrong, assuming @code{len_lquote} and
786 @code{len_rquote} are meant to be the lengths of @code{lquote} and
787 @code{rquote} respectively. We can set them to better values using
788 the @code{p} command, since it can print the value of
789 any expression---and that expression can include subroutine calls and
793 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
795 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
800 Is that enough to fix the problem of using the new quotes with the
801 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
802 executing with the @code{c} (@code{continue}) command, and then try the
803 example that caused trouble initially:
809 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
816 Success! The new quotes now work just as well as the default ones. The
817 problem seems to have been just the two typos defining the wrong
818 lengths. We allow @code{m4} exit by giving it an EOF as input:
822 Program exited normally.
826 The message @samp{Program exited normally.} is from @value{GDBN}; it
827 indicates @code{m4} has finished executing. We can end our @value{GDBN}
828 session with the @value{GDBN} @code{quit} command.
831 (@value{GDBP}) @b{quit}
835 @chapter Getting In and Out of @value{GDBN}
837 This chapter discusses how to start @value{GDBN}, and how to get out of it.
841 type @samp{@value{GDBP}} to start @value{GDBN}.
843 type @kbd{quit} or @kbd{Ctrl-d} to exit.
847 * Invoking GDB:: How to start @value{GDBN}
848 * Quitting GDB:: How to quit @value{GDBN}
849 * Shell Commands:: How to use shell commands inside @value{GDBN}
850 * Logging Output:: How to log @value{GDBN}'s output to a file
854 @section Invoking @value{GDBN}
856 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
857 @value{GDBN} reads commands from the terminal until you tell it to exit.
859 You can also run @code{@value{GDBP}} with a variety of arguments and options,
860 to specify more of your debugging environment at the outset.
862 The command-line options described here are designed
863 to cover a variety of situations; in some environments, some of these
864 options may effectively be unavailable.
866 The most usual way to start @value{GDBN} is with one argument,
867 specifying an executable program:
870 @value{GDBP} @var{program}
874 You can also start with both an executable program and a core file
878 @value{GDBP} @var{program} @var{core}
881 You can, instead, specify a process ID as a second argument or use option
882 @code{-p}, if you want to debug a running process:
885 @value{GDBP} @var{program} 1234
890 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
891 can omit the @var{program} filename.
893 Taking advantage of the second command-line argument requires a fairly
894 complete operating system; when you use @value{GDBN} as a remote
895 debugger attached to a bare board, there may not be any notion of
896 ``process'', and there is often no way to get a core dump. @value{GDBN}
897 will warn you if it is unable to attach or to read core dumps.
899 You can optionally have @code{@value{GDBP}} pass any arguments after the
900 executable file to the inferior using @code{--args}. This option stops
903 @value{GDBP} --args gcc -O2 -c foo.c
905 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
906 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
908 You can run @code{@value{GDBP}} without printing the front material, which describes
909 @value{GDBN}'s non-warranty, by specifying @code{--silent}
910 (or @code{-q}/@code{--quiet}):
913 @value{GDBP} --silent
917 You can further control how @value{GDBN} starts up by using command-line
918 options. @value{GDBN} itself can remind you of the options available.
928 to display all available options and briefly describe their use
929 (@samp{@value{GDBP} -h} is a shorter equivalent).
931 All options and command line arguments you give are processed
932 in sequential order. The order makes a difference when the
933 @samp{-x} option is used.
937 * File Options:: Choosing files
938 * Mode Options:: Choosing modes
939 * Startup:: What @value{GDBN} does during startup
940 * Initialization Files:: Initialization Files
944 @subsection Choosing Files
946 When @value{GDBN} starts, it reads any arguments other than options as
947 specifying an executable file and core file (or process ID). This is
948 the same as if the arguments were specified by the @samp{-se} and
949 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
950 first argument that does not have an associated option flag as
951 equivalent to the @samp{-se} option followed by that argument; and the
952 second argument that does not have an associated option flag, if any, as
953 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
954 If the second argument begins with a decimal digit, @value{GDBN} will
955 first attempt to attach to it as a process, and if that fails, attempt
956 to open it as a corefile. If you have a corefile whose name begins with
957 a digit, you can prevent @value{GDBN} from treating it as a pid by
958 prefixing it with @file{./}, e.g.@: @file{./12345}.
960 If @value{GDBN} has not been configured to included core file support,
961 such as for most embedded targets, then it will complain about a second
962 argument and ignore it.
964 Many options have both long and short forms; both are shown in the
965 following list. @value{GDBN} also recognizes the long forms if you truncate
966 them, so long as enough of the option is present to be unambiguous.
967 (If you prefer, you can flag option arguments with @samp{--} rather
968 than @samp{-}, though we illustrate the more usual convention.)
970 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
971 @c way, both those who look for -foo and --foo in the index, will find
975 @item -symbols @var{file}
977 @cindex @code{--symbols}
979 Read symbol table from file @var{file}.
981 @item -exec @var{file}
983 @cindex @code{--exec}
985 Use file @var{file} as the executable file to execute when appropriate,
986 and for examining pure data in conjunction with a core dump.
990 Read symbol table from file @var{file} and use it as the executable
993 @item -core @var{file}
995 @cindex @code{--core}
997 Use file @var{file} as a core dump to examine.
999 @item -pid @var{number}
1000 @itemx -p @var{number}
1001 @cindex @code{--pid}
1003 Connect to process ID @var{number}, as with the @code{attach} command.
1005 @item -command @var{file}
1006 @itemx -x @var{file}
1007 @cindex @code{--command}
1009 Execute commands from file @var{file}. The contents of this file is
1010 evaluated exactly as the @code{source} command would.
1011 @xref{Command Files,, Command files}.
1013 @item -eval-command @var{command}
1014 @itemx -ex @var{command}
1015 @cindex @code{--eval-command}
1017 Execute a single @value{GDBN} command.
1019 This option may be used multiple times to call multiple commands. It may
1020 also be interleaved with @samp{-command} as required.
1023 @value{GDBP} -ex 'target sim' -ex 'load' \
1024 -x setbreakpoints -ex 'run' a.out
1027 @item -init-command @var{file}
1028 @itemx -ix @var{file}
1029 @cindex @code{--init-command}
1031 Execute commands from file @var{file} before loading the inferior (but
1032 after loading gdbinit files).
1035 @item -init-eval-command @var{command}
1036 @itemx -iex @var{command}
1037 @cindex @code{--init-eval-command}
1039 Execute a single @value{GDBN} command before loading the inferior (but
1040 after loading gdbinit files).
1043 @item -early-init-command @var{file}
1044 @itemx -eix @var{file}
1045 @cindex @code{--early-init-command}
1047 Execute commands from @var{file} very early in the initialization
1048 process, before any output is produced. @xref{Startup}.
1050 @item -early-init-eval-command @var{command}
1051 @itemx -eiex @var{command}
1052 @cindex @code{--early-init-eval-command}
1053 @cindex @code{-eiex}
1054 Execute a single @value{GDBN} command very early in the initialization
1055 process, before any output is produced.
1057 @item -directory @var{directory}
1058 @itemx -d @var{directory}
1059 @cindex @code{--directory}
1061 Add @var{directory} to the path to search for source and script files.
1065 @cindex @code{--readnow}
1067 Read each symbol file's entire symbol table immediately, rather than
1068 the default, which is to read it incrementally as it is needed.
1069 This makes startup slower, but makes future operations faster.
1072 @anchor{--readnever}
1073 @cindex @code{--readnever}, command-line option
1074 Do not read each symbol file's symbolic debug information. This makes
1075 startup faster but at the expense of not being able to perform
1076 symbolic debugging. DWARF unwind information is also not read,
1077 meaning backtraces may become incomplete or inaccurate. One use of
1078 this is when a user simply wants to do the following sequence: attach,
1079 dump core, detach. Loading the debugging information in this case is
1080 an unnecessary cause of delay.
1084 @subsection Choosing Modes
1086 You can run @value{GDBN} in various alternative modes---for example, in
1087 batch mode or quiet mode.
1095 Do not execute commands found in any initialization files
1096 (@pxref{Initialization Files}).
1101 Do not execute commands found in any home directory initialization
1102 file (@pxref{Initialization Files,,Home directory initialization
1103 file}). The system wide and current directory initialization files
1109 @cindex @code{--quiet}
1110 @cindex @code{--silent}
1112 ``Quiet''. Do not print the introductory and copyright messages. These
1113 messages are also suppressed in batch mode.
1115 @kindex set startup-quietly
1116 @kindex show startup-quietly
1117 This can also be enabled using @code{set startup-quietly on}. The
1118 default is @code{off}. Use @code{show startup-quietly} to see the
1119 current setting. Place @code{set startup-quietly on} into your early
1120 initialization file (@pxref{Initialization Files,,Initialization
1121 Files}) to have future @value{GDBN} sessions startup quietly.
1124 @cindex @code{--batch}
1125 Run in batch mode. Exit with status @code{0} after processing all the
1126 command files specified with @samp{-x} (and all commands from
1127 initialization files, if not inhibited with @samp{-n}). Exit with
1128 nonzero status if an error occurs in executing the @value{GDBN} commands
1129 in the command files. Batch mode also disables pagination, sets unlimited
1130 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1131 off} were in effect (@pxref{Messages/Warnings}).
1133 Batch mode may be useful for running @value{GDBN} as a filter, for
1134 example to download and run a program on another computer; in order to
1135 make this more useful, the message
1138 Program exited normally.
1142 (which is ordinarily issued whenever a program running under
1143 @value{GDBN} control terminates) is not issued when running in batch
1147 @cindex @code{--batch-silent}
1148 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1149 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1150 unaffected). This is much quieter than @samp{-silent} and would be useless
1151 for an interactive session.
1153 This is particularly useful when using targets that give @samp{Loading section}
1154 messages, for example.
1156 Note that targets that give their output via @value{GDBN}, as opposed to
1157 writing directly to @code{stdout}, will also be made silent.
1159 @item -return-child-result
1160 @cindex @code{--return-child-result}
1161 The return code from @value{GDBN} will be the return code from the child
1162 process (the process being debugged), with the following exceptions:
1166 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1167 internal error. In this case the exit code is the same as it would have been
1168 without @samp{-return-child-result}.
1170 The user quits with an explicit value. E.g., @samp{quit 1}.
1172 The child process never runs, or is not allowed to terminate, in which case
1173 the exit code will be -1.
1176 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1177 when @value{GDBN} is being used as a remote program loader or simulator
1182 @cindex @code{--nowindows}
1184 ``No windows''. If @value{GDBN} comes with a graphical user interface
1185 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1186 interface. If no GUI is available, this option has no effect.
1190 @cindex @code{--windows}
1192 If @value{GDBN} includes a GUI, then this option requires it to be
1195 @item -cd @var{directory}
1197 Run @value{GDBN} using @var{directory} as its working directory,
1198 instead of the current directory.
1200 @item -data-directory @var{directory}
1201 @itemx -D @var{directory}
1202 @cindex @code{--data-directory}
1204 Run @value{GDBN} using @var{directory} as its data directory.
1205 The data directory is where @value{GDBN} searches for its
1206 auxiliary files. @xref{Data Files}.
1210 @cindex @code{--fullname}
1212 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1213 subprocess. It tells @value{GDBN} to output the full file name and line
1214 number in a standard, recognizable fashion each time a stack frame is
1215 displayed (which includes each time your program stops). This
1216 recognizable format looks like two @samp{\032} characters, followed by
1217 the file name, line number and character position separated by colons,
1218 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1219 @samp{\032} characters as a signal to display the source code for the
1222 @item -annotate @var{level}
1223 @cindex @code{--annotate}
1224 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1225 effect is identical to using @samp{set annotate @var{level}}
1226 (@pxref{Annotations}). The annotation @var{level} controls how much
1227 information @value{GDBN} prints together with its prompt, values of
1228 expressions, source lines, and other types of output. Level 0 is the
1229 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1230 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1231 that control @value{GDBN}, and level 2 has been deprecated.
1233 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1237 @cindex @code{--args}
1238 Change interpretation of command line so that arguments following the
1239 executable file are passed as command line arguments to the inferior.
1240 This option stops option processing.
1242 @item -baud @var{bps}
1244 @cindex @code{--baud}
1246 Set the line speed (baud rate or bits per second) of any serial
1247 interface used by @value{GDBN} for remote debugging.
1249 @item -l @var{timeout}
1251 Set the timeout (in seconds) of any communication used by @value{GDBN}
1252 for remote debugging.
1254 @item -tty @var{device}
1255 @itemx -t @var{device}
1256 @cindex @code{--tty}
1258 Run using @var{device} for your program's standard input and output.
1259 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1261 @c resolve the situation of these eventually
1263 @cindex @code{--tui}
1264 Activate the @dfn{Text User Interface} when starting. The Text User
1265 Interface manages several text windows on the terminal, showing
1266 source, assembly, registers and @value{GDBN} command outputs
1267 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1268 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1269 Using @value{GDBN} under @sc{gnu} Emacs}).
1271 @item -interpreter @var{interp}
1272 @cindex @code{--interpreter}
1273 Use the interpreter @var{interp} for interface with the controlling
1274 program or device. This option is meant to be set by programs which
1275 communicate with @value{GDBN} using it as a back end.
1276 @xref{Interpreters, , Command Interpreters}.
1278 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1279 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1280 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1281 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1282 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1283 interfaces are no longer supported.
1286 @cindex @code{--write}
1287 Open the executable and core files for both reading and writing. This
1288 is equivalent to the @samp{set write on} command inside @value{GDBN}
1292 @cindex @code{--statistics}
1293 This option causes @value{GDBN} to print statistics about time and
1294 memory usage after it completes each command and returns to the prompt.
1297 @cindex @code{--version}
1298 This option causes @value{GDBN} to print its version number and
1299 no-warranty blurb, and exit.
1301 @item -configuration
1302 @cindex @code{--configuration}
1303 This option causes @value{GDBN} to print details about its build-time
1304 configuration parameters, and then exit. These details can be
1305 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1310 @subsection What @value{GDBN} Does During Startup
1311 @cindex @value{GDBN} startup
1313 Here's the description of what @value{GDBN} does during session startup:
1318 Performs minimal setup required to initialize basic internal state.
1321 @cindex early initialization file
1322 Reads commands from the early initialization file (if any) in your
1323 home directory. Only a restricted set of commands can be placed into
1324 an early initialization file, see @ref{Initialization Files}, for
1328 Executes commands and command files specified by the @samp{-eiex} and
1329 @samp{-eix} command line options in their specified order. Only a
1330 restricted set of commands can be used with @samp{-eiex} and
1331 @samp{eix}, see @ref{Initialization Files}, for details.
1334 Sets up the command interpreter as specified by the command line
1335 (@pxref{Mode Options, interpreter}).
1339 Reads the system wide initialization file and the files from the
1340 system wide initialization directory, @pxref{System Wide Init Files}.
1343 Reads the initialization file (if any) in your home directory and
1344 executes all the commands in that file, @pxref{Home Directory Init
1347 @anchor{Option -init-eval-command}
1349 Executes commands and command files specified by the @samp{-iex} and
1350 @samp{-ix} options in their specified order. Usually you should use the
1351 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1352 settings before @value{GDBN} init files get executed and before inferior
1356 Processes command line options and operands.
1359 Reads and executes the commands from the initialization file (if any)
1360 in the current working directory as long as @samp{set auto-load
1361 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1362 Directory}). This is only done if the current directory is different
1363 from your home directory. Thus, you can have more than one init file,
1364 one generic in your home directory, and another, specific to the
1365 program you are debugging, in the directory where you invoke
1366 @value{GDBN}. @xref{Init File in the Current Directory during
1370 If the command line specified a program to debug, or a process to
1371 attach to, or a core file, @value{GDBN} loads any auto-loaded
1372 scripts provided for the program or for its loaded shared libraries.
1373 @xref{Auto-loading}.
1375 If you wish to disable the auto-loading during startup,
1376 you must do something like the following:
1379 $ gdb -iex "set auto-load python-scripts off" myprogram
1382 Option @samp{-ex} does not work because the auto-loading is then turned
1386 Executes commands and command files specified by the @samp{-ex} and
1387 @samp{-x} options in their specified order. @xref{Command Files}, for
1388 more details about @value{GDBN} command files.
1391 Reads the command history recorded in the @dfn{history file}.
1392 @xref{Command History}, for more details about the command history and the
1393 files where @value{GDBN} records it.
1396 @node Initialization Files
1397 @subsection Initialization Files
1398 @cindex init file name
1400 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1401 from several initialization files. These initialization files use the
1402 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1403 processed by @value{GDBN} in the same way.
1405 To display the list of initialization files loaded by @value{GDBN} at
1406 startup, in the order they will be loaded, you can use @kbd{gdb
1409 @cindex early initialization
1410 The @dfn{early initialization} file is loaded very early in
1411 @value{GDBN}'s initialization process, before the interpreter
1412 (@pxref{Interpreters}) has been initialized, and before the default
1413 target (@pxref{Targets}) is initialized. Only @code{set} or
1414 @code{source} commands should be placed into an early initialization
1415 file, and the only @code{set} commands that can be used are those that
1416 control how @value{GDBN} starts up.
1418 Commands that can be placed into an early initialization file will be
1419 documented as such throughout this manual. Any command that is not
1420 documented as being suitable for an early initialization file should
1421 instead be placed into a general initialization file. Command files
1422 passed to @code{--early-init-command} or @code{-eix} are also early
1423 initialization files, with the same command restrictions. Only
1424 commands that can appear in an early initialization file should be
1425 passed to @code{--early-init-eval-command} or @code{-eiex}.
1427 @cindex general initialization
1428 In contrast, the @dfn{general initialization} files are processed
1429 later, after @value{GDBN} has finished its own internal initialization
1430 process, any valid command can be used in these files.
1432 @cindex initialization file
1433 Throughout the rest of this document the term @dfn{initialization
1434 file} refers to one of the general initialization files, not the early
1435 initialization file. Any discussion of the early initialization file
1436 will specifically mention that it is the early initialization file
1439 As the system wide and home directory initialization files are
1440 processed before most command line options, changes to settings
1441 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1442 command line options and operands.
1444 The following sections describe where @value{GDBN} looks for the early
1445 initialization and initialization files, and the order that the files
1448 @subsubsection Home directory early initialization files
1450 @value{GDBN} initially looks for an early initialization file in the
1451 users home directory@footnote{On DOS/Windows systems, the home
1452 directory is the one pointed to by the @env{HOME} environment
1453 variable.}. There are a number of locations that @value{GDBN} will
1454 search in the home directory, these locations are searched in order
1455 and @value{GDBN} will load the first file that it finds, and
1456 subsequent locations will not be checked.
1458 On non-macOS hosts the locations searched are:
1461 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1462 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1464 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1465 by the environment variable @env{HOME}, if it is defined.
1467 The file @file{.gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{HOME}, if it is defined.
1471 By contrast, on macOS hosts the locations searched are:
1474 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1475 directory pointed to by the environment variable @env{HOME}, if it is
1478 The file @file{.gdbearlyinit} within the directory pointed to by the
1479 environment variable @env{HOME}, if it is defined.
1482 It is possible to prevent the home directory early initialization file
1483 from being loaded using the @samp{-nx} or @samp{-nh} command line
1484 options, @pxref{Mode Options,,Choosing Modes}.
1486 @anchor{System Wide Init Files}
1487 @subsubsection System wide initialization files
1489 There are two locations that are searched for system wide
1490 initialization files. Both of these locations are always checked:
1494 @item @file{system.gdbinit}
1495 This is a single system-wide initialization file. Its location is
1496 specified with the @code{--with-system-gdbinit} configure option
1497 (@pxref{System-wide configuration}). It is loaded first when
1498 @value{GDBN} starts, before command line options have been processed.
1500 @item @file{system.gdbinit.d}
1501 This is the system-wide initialization directory. Its location is
1502 specified with the @code{--with-system-gdbinit-dir} configure option
1503 (@pxref{System-wide configuration}). Files in this directory are
1504 loaded in alphabetical order immediately after @file{system.gdbinit}
1505 (if enabled) when @value{GDBN} starts, before command line options
1506 have been processed. Files need to have a recognized scripting
1507 language extension (@file{.py}/@file{.scm}) or be named with a
1508 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1509 commands. @value{GDBN} will not recurse into any subdirectories of
1514 It is possible to prevent the system wide initialization files from
1515 being loaded using the @samp{-nx} command line option, @pxref{Mode
1516 Options,,Choosing Modes}.
1518 @anchor{Home Directory Init File}
1519 @subsubsection Home directory initialization file
1520 @cindex @file{gdbinit}
1521 @cindex @file{.gdbinit}
1522 @cindex @file{gdb.ini}
1524 After loading the system wide initialization files @value{GDBN} will
1525 look for an initialization file in the users home
1526 directory@footnote{On DOS/Windows systems, the home directory is the
1527 one pointed to by the @env{HOME} environment variable.}. There are a
1528 number of locations that @value{GDBN} will search in the home
1529 directory, these locations are searched in order and @value{GDBN} will
1530 load the first file that it finds, and subsequent locations will not
1533 On non-Apple hosts the locations searched are:
1535 @item $XDG_CONFIG_HOME/gdb/gdbinit
1536 @item $HOME/.config/gdb/gdbinit
1537 @item $HOME/.gdbinit
1540 While on Apple hosts the locations searched are:
1542 @item $HOME/Library/Preferences/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 It is possible to prevent the home directory initialization file from
1547 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1548 @pxref{Mode Options,,Choosing Modes}.
1550 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1551 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1552 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1553 uses the standard name, but if it finds a @file{gdb.ini} file in your
1554 home directory, it warns you about that and suggests to rename the
1555 file to the standard name.
1557 @anchor{Init File in the Current Directory during Startup}
1558 @subsubsection Local directory initialization file
1560 @value{GDBN} will check the current directory for a file called
1561 @file{.gdbinit}. It is loaded last, after command line options
1562 other than @samp{-x} and @samp{-ex} have been processed. The command
1563 line options @samp{-x} and @samp{-ex} are processed last, after
1564 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1567 If the file in the current directory was already loaded as the home
1568 directory initialization file then it will not be loaded a second
1571 It is possible to prevent the local directory initialization file from
1572 being loaded using the @samp{-nx} command line option, @pxref{Mode
1573 Options,,Choosing Modes}.
1576 @section Quitting @value{GDBN}
1577 @cindex exiting @value{GDBN}
1578 @cindex leaving @value{GDBN}
1581 @kindex quit @r{[}@var{expression}@r{]}
1582 @kindex q @r{(@code{quit})}
1583 @item quit @r{[}@var{expression}@r{]}
1585 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1586 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1587 do not supply @var{expression}, @value{GDBN} will terminate normally;
1588 otherwise it will terminate using the result of @var{expression} as the
1593 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1594 terminates the action of any @value{GDBN} command that is in progress and
1595 returns to @value{GDBN} command level. It is safe to type the interrupt
1596 character at any time because @value{GDBN} does not allow it to take effect
1597 until a time when it is safe.
1599 If you have been using @value{GDBN} to control an attached process or
1600 device, you can release it with the @code{detach} command
1601 (@pxref{Attach, ,Debugging an Already-running Process}).
1603 @node Shell Commands
1604 @section Shell Commands
1606 If you need to execute occasional shell commands during your
1607 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1608 just use the @code{shell} command.
1613 @cindex shell escape
1614 @item shell @var{command-string}
1615 @itemx !@var{command-string}
1616 Invoke a standard shell to execute @var{command-string}.
1617 Note that no space is needed between @code{!} and @var{command-string}.
1618 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1619 exists, determines which shell to run. Otherwise @value{GDBN} uses
1620 the default shell (@file{/bin/sh} on GNU and Unix systems,
1621 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1624 The utility @code{make} is often needed in development environments.
1625 You do not have to use the @code{shell} command for this purpose in
1630 @cindex calling make
1631 @item make @var{make-args}
1632 Execute the @code{make} program with the specified
1633 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1639 @cindex send the output of a gdb command to a shell command
1641 @item pipe [@var{command}] | @var{shell_command}
1642 @itemx | [@var{command}] | @var{shell_command}
1643 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1644 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1645 Executes @var{command} and sends its output to @var{shell_command}.
1646 Note that no space is needed around @code{|}.
1647 If no @var{command} is provided, the last command executed is repeated.
1649 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1650 can be used to specify an alternate delimiter string @var{delim} that separates
1651 the @var{command} from the @var{shell_command}.
1684 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1685 this contains a PIPE char
1686 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1687 this contains a PIPE char!
1693 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1694 can be used to examine the exit status of the last shell command launched
1695 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1696 @xref{Convenience Vars,, Convenience Variables}.
1698 @node Logging Output
1699 @section Logging Output
1700 @cindex logging @value{GDBN} output
1701 @cindex save @value{GDBN} output to a file
1703 You may want to save the output of @value{GDBN} commands to a file.
1704 There are several commands to control @value{GDBN}'s logging.
1708 @item set logging on
1710 @item set logging off
1712 @cindex logging file name
1713 @item set logging file @var{file}
1714 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1715 @item set logging overwrite [on|off]
1716 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1717 you want @code{set logging on} to overwrite the logfile instead.
1718 @item set logging redirect [on|off]
1719 By default, @value{GDBN} output will go to both the terminal and the logfile.
1720 Set @code{redirect} if you want output to go only to the log file.
1721 @item set logging debugredirect [on|off]
1722 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1723 Set @code{debugredirect} if you want debug output to go only to the log file.
1724 @kindex show logging
1726 Show the current values of the logging settings.
1729 You can also redirect the output of a @value{GDBN} command to a
1730 shell command. @xref{pipe}.
1732 @chapter @value{GDBN} Commands
1734 You can abbreviate a @value{GDBN} command to the first few letters of the command
1735 name, if that abbreviation is unambiguous; and you can repeat certain
1736 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1737 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1738 show you the alternatives available, if there is more than one possibility).
1741 * Command Syntax:: How to give commands to @value{GDBN}
1742 * Command Settings:: How to change default behavior of commands
1743 * Completion:: Command completion
1744 * Command Options:: Command options
1745 * Help:: How to ask @value{GDBN} for help
1748 @node Command Syntax
1749 @section Command Syntax
1751 A @value{GDBN} command is a single line of input. There is no limit on
1752 how long it can be. It starts with a command name, which is followed by
1753 arguments whose meaning depends on the command name. For example, the
1754 command @code{step} accepts an argument which is the number of times to
1755 step, as in @samp{step 5}. You can also use the @code{step} command
1756 with no arguments. Some commands do not allow any arguments.
1758 @cindex abbreviation
1759 @value{GDBN} command names may always be truncated if that abbreviation is
1760 unambiguous. Other possible command abbreviations are listed in the
1761 documentation for individual commands. In some cases, even ambiguous
1762 abbreviations are allowed; for example, @code{s} is specially defined as
1763 equivalent to @code{step} even though there are other commands whose
1764 names start with @code{s}. You can test abbreviations by using them as
1765 arguments to the @code{help} command.
1767 @cindex repeating commands
1768 @kindex RET @r{(repeat last command)}
1769 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1770 repeat the previous command. Certain commands (for example, @code{run})
1771 will not repeat this way; these are commands whose unintentional
1772 repetition might cause trouble and which you are unlikely to want to
1773 repeat. User-defined commands can disable this feature; see
1774 @ref{Define, dont-repeat}.
1776 The @code{list} and @code{x} commands, when you repeat them with
1777 @key{RET}, construct new arguments rather than repeating
1778 exactly as typed. This permits easy scanning of source or memory.
1780 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1781 output, in a way similar to the common utility @code{more}
1782 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1783 @key{RET} too many in this situation, @value{GDBN} disables command
1784 repetition after any command that generates this sort of display.
1786 @kindex # @r{(a comment)}
1788 Any text from a @kbd{#} to the end of the line is a comment; it does
1789 nothing. This is useful mainly in command files (@pxref{Command
1790 Files,,Command Files}).
1792 @cindex repeating command sequences
1793 @kindex Ctrl-o @r{(operate-and-get-next)}
1794 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1795 commands. This command accepts the current line, like @key{RET}, and
1796 then fetches the next line relative to the current line from the history
1800 @node Command Settings
1801 @section Command Settings
1802 @cindex default behavior of commands, changing
1803 @cindex default settings, changing
1805 Many commands change their behavior according to command-specific
1806 variables or settings. These settings can be changed with the
1807 @code{set} subcommands. For example, the @code{print} command
1808 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1809 settings changeable with the commands @code{set print elements
1810 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1812 You can change these settings to your preference in the gdbinit files
1813 loaded at @value{GDBN} startup. @xref{Startup}.
1815 The settings can also be changed interactively during the debugging
1816 session. For example, to change the limit of array elements to print,
1817 you can do the following:
1819 (@value{GDBN}) set print elements 10
1820 (@value{GDBN}) print some_array
1821 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1824 The above @code{set print elements 10} command changes the number of
1825 elements to print from the default of 200 to 10. If you only intend
1826 this limit of 10 to be used for printing @code{some_array}, then you
1827 must restore the limit back to 200, with @code{set print elements
1830 Some commands allow overriding settings with command options. For
1831 example, the @code{print} command supports a number of options that
1832 allow overriding relevant global print settings as set by @code{set
1833 print} subcommands. @xref{print options}. The example above could be
1836 (@value{GDBN}) print -elements 10 -- some_array
1837 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1840 Alternatively, you can use the @code{with} command to change a setting
1841 temporarily, for the duration of a command invocation.
1844 @kindex with command
1845 @kindex w @r{(@code{with})}
1847 @cindex temporarily change settings
1848 @item with @var{setting} [@var{value}] [-- @var{command}]
1849 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1850 Temporarily set @var{setting} to @var{value} for the duration of
1853 @var{setting} is any setting you can change with the @code{set}
1854 subcommands. @var{value} is the value to assign to @code{setting}
1855 while running @code{command}.
1857 If no @var{command} is provided, the last command executed is
1860 If a @var{command} is provided, it must be preceded by a double dash
1861 (@code{--}) separator. This is required because some settings accept
1862 free-form arguments, such as expressions or filenames.
1864 For example, the command
1866 (@value{GDBN}) with print array on -- print some_array
1869 is equivalent to the following 3 commands:
1871 (@value{GDBN}) set print array on
1872 (@value{GDBN}) print some_array
1873 (@value{GDBN}) set print array off
1876 The @code{with} command is particularly useful when you want to
1877 override a setting while running user-defined commands, or commands
1878 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1881 (@value{GDBN}) with print pretty on -- my_complex_command
1884 To change several settings for the same command, you can nest
1885 @code{with} commands. For example, @code{with language ada -- with
1886 print elements 10} temporarily changes the language to Ada and sets a
1887 limit of 10 elements to print for arrays and strings.
1892 @section Command Completion
1895 @cindex word completion
1896 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1897 only one possibility; it can also show you what the valid possibilities
1898 are for the next word in a command, at any time. This works for @value{GDBN}
1899 commands, @value{GDBN} subcommands, command options, and the names of symbols
1902 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1903 of a word. If there is only one possibility, @value{GDBN} fills in the
1904 word, and waits for you to finish the command (or press @key{RET} to
1905 enter it). For example, if you type
1907 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1908 @c complete accuracy in these examples; space introduced for clarity.
1909 @c If texinfo enhancements make it unnecessary, it would be nice to
1910 @c replace " @key" by "@key" in the following...
1912 (@value{GDBP}) info bre @key{TAB}
1916 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1917 the only @code{info} subcommand beginning with @samp{bre}:
1920 (@value{GDBP}) info breakpoints
1924 You can either press @key{RET} at this point, to run the @code{info
1925 breakpoints} command, or backspace and enter something else, if
1926 @samp{breakpoints} does not look like the command you expected. (If you
1927 were sure you wanted @code{info breakpoints} in the first place, you
1928 might as well just type @key{RET} immediately after @samp{info bre},
1929 to exploit command abbreviations rather than command completion).
1931 If there is more than one possibility for the next word when you press
1932 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1933 characters and try again, or just press @key{TAB} a second time;
1934 @value{GDBN} displays all the possible completions for that word. For
1935 example, you might want to set a breakpoint on a subroutine whose name
1936 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1937 just sounds the bell. Typing @key{TAB} again displays all the
1938 function names in your program that begin with those characters, for
1942 (@value{GDBP}) b make_ @key{TAB}
1943 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1944 make_a_section_from_file make_environ
1945 make_abs_section make_function_type
1946 make_blockvector make_pointer_type
1947 make_cleanup make_reference_type
1948 make_command make_symbol_completion_list
1949 (@value{GDBP}) b make_
1953 After displaying the available possibilities, @value{GDBN} copies your
1954 partial input (@samp{b make_} in the example) so you can finish the
1957 If you just want to see the list of alternatives in the first place, you
1958 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1959 means @kbd{@key{META} ?}. You can type this either by holding down a
1960 key designated as the @key{META} shift on your keyboard (if there is
1961 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1963 If the number of possible completions is large, @value{GDBN} will
1964 print as much of the list as it has collected, as well as a message
1965 indicating that the list may be truncated.
1968 (@value{GDBP}) b m@key{TAB}@key{TAB}
1970 <... the rest of the possible completions ...>
1971 *** List may be truncated, max-completions reached. ***
1976 This behavior can be controlled with the following commands:
1979 @kindex set max-completions
1980 @item set max-completions @var{limit}
1981 @itemx set max-completions unlimited
1982 Set the maximum number of completion candidates. @value{GDBN} will
1983 stop looking for more completions once it collects this many candidates.
1984 This is useful when completing on things like function names as collecting
1985 all the possible candidates can be time consuming.
1986 The default value is 200. A value of zero disables tab-completion.
1987 Note that setting either no limit or a very large limit can make
1989 @kindex show max-completions
1990 @item show max-completions
1991 Show the maximum number of candidates that @value{GDBN} will collect and show
1995 @cindex quotes in commands
1996 @cindex completion of quoted strings
1997 Sometimes the string you need, while logically a ``word'', may contain
1998 parentheses or other characters that @value{GDBN} normally excludes from
1999 its notion of a word. To permit word completion to work in this
2000 situation, you may enclose words in @code{'} (single quote marks) in
2001 @value{GDBN} commands.
2003 A likely situation where you might need this is in typing an
2004 expression that involves a C@t{++} symbol name with template
2005 parameters. This is because when completing expressions, GDB treats
2006 the @samp{<} character as word delimiter, assuming that it's the
2007 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2010 For example, when you want to call a C@t{++} template function
2011 interactively using the @code{print} or @code{call} commands, you may
2012 need to distinguish whether you mean the version of @code{name} that
2013 was specialized for @code{int}, @code{name<int>()}, or the version
2014 that was specialized for @code{float}, @code{name<float>()}. To use
2015 the word-completion facilities in this situation, type a single quote
2016 @code{'} at the beginning of the function name. This alerts
2017 @value{GDBN} that it may need to consider more information than usual
2018 when you press @key{TAB} or @kbd{M-?} to request word completion:
2021 (@value{GDBP}) p 'func< @kbd{M-?}
2022 func<int>() func<float>()
2023 (@value{GDBP}) p 'func<
2026 When setting breakpoints however (@pxref{Specify Location}), you don't
2027 usually need to type a quote before the function name, because
2028 @value{GDBN} understands that you want to set a breakpoint on a
2032 (@value{GDBP}) b func< @kbd{M-?}
2033 func<int>() func<float>()
2034 (@value{GDBP}) b func<
2037 This is true even in the case of typing the name of C@t{++} overloaded
2038 functions (multiple definitions of the same function, distinguished by
2039 argument type). For example, when you want to set a breakpoint you
2040 don't need to distinguish whether you mean the version of @code{name}
2041 that takes an @code{int} parameter, @code{name(int)}, or the version
2042 that takes a @code{float} parameter, @code{name(float)}.
2045 (@value{GDBP}) b bubble( @kbd{M-?}
2046 bubble(int) bubble(double)
2047 (@value{GDBP}) b bubble(dou @kbd{M-?}
2051 See @ref{quoting names} for a description of other scenarios that
2054 For more information about overloaded functions, see @ref{C Plus Plus
2055 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2056 overload-resolution off} to disable overload resolution;
2057 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2059 @cindex completion of structure field names
2060 @cindex structure field name completion
2061 @cindex completion of union field names
2062 @cindex union field name completion
2063 When completing in an expression which looks up a field in a
2064 structure, @value{GDBN} also tries@footnote{The completer can be
2065 confused by certain kinds of invalid expressions. Also, it only
2066 examines the static type of the expression, not the dynamic type.} to
2067 limit completions to the field names available in the type of the
2071 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2072 magic to_fputs to_rewind
2073 to_data to_isatty to_write
2074 to_delete to_put to_write_async_safe
2079 This is because the @code{gdb_stdout} is a variable of the type
2080 @code{struct ui_file} that is defined in @value{GDBN} sources as
2087 ui_file_flush_ftype *to_flush;
2088 ui_file_write_ftype *to_write;
2089 ui_file_write_async_safe_ftype *to_write_async_safe;
2090 ui_file_fputs_ftype *to_fputs;
2091 ui_file_read_ftype *to_read;
2092 ui_file_delete_ftype *to_delete;
2093 ui_file_isatty_ftype *to_isatty;
2094 ui_file_rewind_ftype *to_rewind;
2095 ui_file_put_ftype *to_put;
2100 @node Command Options
2101 @section Command options
2103 @cindex command options
2104 Some commands accept options starting with a leading dash. For
2105 example, @code{print -pretty}. Similarly to command names, you can
2106 abbreviate a @value{GDBN} option to the first few letters of the
2107 option name, if that abbreviation is unambiguous, and you can also use
2108 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2109 in an option (or to show you the alternatives available, if there is
2110 more than one possibility).
2112 @cindex command options, raw input
2113 Some commands take raw input as argument. For example, the print
2114 command processes arbitrary expressions in any of the languages
2115 supported by @value{GDBN}. With such commands, because raw input may
2116 start with a leading dash that would be confused with an option or any
2117 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2118 -pretty} or printing negative @code{p}?), if you specify any command
2119 option, then you must use a double-dash (@code{--}) delimiter to
2120 indicate the end of options.
2122 @cindex command options, boolean
2124 Some options are described as accepting an argument which can be
2125 either @code{on} or @code{off}. These are known as @dfn{boolean
2126 options}. Similarly to boolean settings commands---@code{on} and
2127 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2128 @code{enable} can also be used as ``true'' value, and any of @code{0},
2129 @code{no} and @code{disable} can also be used as ``false'' value. You
2130 can also omit a ``true'' value, as it is implied by default.
2132 For example, these are equivalent:
2135 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2136 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2139 You can discover the set of options some command accepts by completing
2140 on @code{-} after the command name. For example:
2143 (@value{GDBP}) print -@key{TAB}@key{TAB}
2144 -address -max-depth -raw-values -union
2145 -array -null-stop -repeats -vtbl
2146 -array-indexes -object -static-members
2147 -elements -pretty -symbol
2150 Completion will in some cases guide you with a suggestion of what kind
2151 of argument an option expects. For example:
2154 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2158 Here, the option expects a number (e.g., @code{100}), not literal
2159 @code{NUMBER}. Such metasyntactical arguments are always presented in
2162 (For more on using the @code{print} command, see @ref{Data, ,Examining
2166 @section Getting Help
2167 @cindex online documentation
2170 You can always ask @value{GDBN} itself for information on its commands,
2171 using the command @code{help}.
2174 @kindex h @r{(@code{help})}
2177 You can use @code{help} (abbreviated @code{h}) with no arguments to
2178 display a short list of named classes of commands:
2182 List of classes of commands:
2184 aliases -- User-defined aliases of other commands
2185 breakpoints -- Making program stop at certain points
2186 data -- Examining data
2187 files -- Specifying and examining files
2188 internals -- Maintenance commands
2189 obscure -- Obscure features
2190 running -- Running the program
2191 stack -- Examining the stack
2192 status -- Status inquiries
2193 support -- Support facilities
2194 tracepoints -- Tracing of program execution without
2195 stopping the program
2196 user-defined -- User-defined commands
2198 Type "help" followed by a class name for a list of
2199 commands in that class.
2200 Type "help" followed by command name for full
2202 Command name abbreviations are allowed if unambiguous.
2205 @c the above line break eliminates huge line overfull...
2207 @item help @var{class}
2208 Using one of the general help classes as an argument, you can get a
2209 list of the individual commands in that class. If a command has
2210 aliases, the aliases are given after the command name, separated by
2211 commas. If an alias has default arguments, the full definition of
2212 the alias is given after the first line.
2213 For example, here is the help display for the class @code{status}:
2216 (@value{GDBP}) help status
2221 @c Line break in "show" line falsifies real output, but needed
2222 @c to fit in smallbook page size.
2223 info, inf, i -- Generic command for showing things
2224 about the program being debugged
2225 info address, iamain -- Describe where symbol SYM is stored.
2226 alias iamain = info address main
2227 info all-registers -- List of all registers and their contents,
2228 for selected stack frame.
2230 show, info set -- Generic command for showing things
2233 Type "help" followed by command name for full
2235 Command name abbreviations are allowed if unambiguous.
2239 @item help @var{command}
2240 With a command name as @code{help} argument, @value{GDBN} displays a
2241 short paragraph on how to use that command. If that command has
2242 one or more aliases, @value{GDBN} will display a first line with
2243 the command name and all its aliases separated by commas.
2244 This first line will be followed by the full definition of all aliases
2245 having default arguments.
2248 @item apropos [-v] @var{regexp}
2249 The @code{apropos} command searches through all of the @value{GDBN}
2250 commands, and their documentation, for the regular expression specified in
2251 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2252 which stands for @samp{verbose}, indicates to output the full documentation
2253 of the matching commands and highlight the parts of the documentation
2254 matching @var{regexp}. For example:
2265 alias -- Define a new command that is an alias of an existing command
2266 aliases -- User-defined aliases of other commands
2274 apropos -v cut.*thread apply
2278 results in the below output, where @samp{cut for 'thread apply}
2279 is highlighted if styling is enabled.
2283 taas -- Apply a command to all threads (ignoring errors
2286 shortcut for 'thread apply all -s COMMAND'
2288 tfaas -- Apply a command to all frames of all threads
2289 (ignoring errors and empty output).
2290 Usage: tfaas COMMAND
2291 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2296 @item complete @var{args}
2297 The @code{complete @var{args}} command lists all the possible completions
2298 for the beginning of a command. Use @var{args} to specify the beginning of the
2299 command you want completed. For example:
2305 @noindent results in:
2316 @noindent This is intended for use by @sc{gnu} Emacs.
2319 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2320 and @code{show} to inquire about the state of your program, or the state
2321 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2322 manual introduces each of them in the appropriate context. The listings
2323 under @code{info} and under @code{show} in the Command, Variable, and
2324 Function Index point to all the sub-commands. @xref{Command and Variable
2330 @kindex i @r{(@code{info})}
2332 This command (abbreviated @code{i}) is for describing the state of your
2333 program. For example, you can show the arguments passed to a function
2334 with @code{info args}, list the registers currently in use with @code{info
2335 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2336 You can get a complete list of the @code{info} sub-commands with
2337 @w{@code{help info}}.
2341 You can assign the result of an expression to an environment variable with
2342 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2343 @code{set prompt $}.
2347 In contrast to @code{info}, @code{show} is for describing the state of
2348 @value{GDBN} itself.
2349 You can change most of the things you can @code{show}, by using the
2350 related command @code{set}; for example, you can control what number
2351 system is used for displays with @code{set radix}, or simply inquire
2352 which is currently in use with @code{show radix}.
2355 To display all the settable parameters and their current
2356 values, you can use @code{show} with no arguments; you may also use
2357 @code{info set}. Both commands produce the same display.
2358 @c FIXME: "info set" violates the rule that "info" is for state of
2359 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2360 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2364 Here are several miscellaneous @code{show} subcommands, all of which are
2365 exceptional in lacking corresponding @code{set} commands:
2368 @kindex show version
2369 @cindex @value{GDBN} version number
2371 Show what version of @value{GDBN} is running. You should include this
2372 information in @value{GDBN} bug-reports. If multiple versions of
2373 @value{GDBN} are in use at your site, you may need to determine which
2374 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2375 commands are introduced, and old ones may wither away. Also, many
2376 system vendors ship variant versions of @value{GDBN}, and there are
2377 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2378 The version number is the same as the one announced when you start
2381 @kindex show copying
2382 @kindex info copying
2383 @cindex display @value{GDBN} copyright
2386 Display information about permission for copying @value{GDBN}.
2388 @kindex show warranty
2389 @kindex info warranty
2391 @itemx info warranty
2392 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2393 if your version of @value{GDBN} comes with one.
2395 @kindex show configuration
2396 @item show configuration
2397 Display detailed information about the way @value{GDBN} was configured
2398 when it was built. This displays the optional arguments passed to the
2399 @file{configure} script and also configuration parameters detected
2400 automatically by @command{configure}. When reporting a @value{GDBN}
2401 bug (@pxref{GDB Bugs}), it is important to include this information in
2407 @chapter Running Programs Under @value{GDBN}
2409 When you run a program under @value{GDBN}, you must first generate
2410 debugging information when you compile it.
2412 You may start @value{GDBN} with its arguments, if any, in an environment
2413 of your choice. If you are doing native debugging, you may redirect
2414 your program's input and output, debug an already running process, or
2415 kill a child process.
2418 * Compilation:: Compiling for debugging
2419 * Starting:: Starting your program
2420 * Arguments:: Your program's arguments
2421 * Environment:: Your program's environment
2423 * Working Directory:: Your program's working directory
2424 * Input/Output:: Your program's input and output
2425 * Attach:: Debugging an already-running process
2426 * Kill Process:: Killing the child process
2427 * Inferiors Connections and Programs:: Debugging multiple inferiors
2428 connections and programs
2429 * Threads:: Debugging programs with multiple threads
2430 * Forks:: Debugging forks
2431 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2435 @section Compiling for Debugging
2437 In order to debug a program effectively, you need to generate
2438 debugging information when you compile it. This debugging information
2439 is stored in the object file; it describes the data type of each
2440 variable or function and the correspondence between source line numbers
2441 and addresses in the executable code.
2443 To request debugging information, specify the @samp{-g} option when you run
2446 Programs that are to be shipped to your customers are compiled with
2447 optimizations, using the @samp{-O} compiler option. However, some
2448 compilers are unable to handle the @samp{-g} and @samp{-O} options
2449 together. Using those compilers, you cannot generate optimized
2450 executables containing debugging information.
2452 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2453 without @samp{-O}, making it possible to debug optimized code. We
2454 recommend that you @emph{always} use @samp{-g} whenever you compile a
2455 program. You may think your program is correct, but there is no sense
2456 in pushing your luck. For more information, see @ref{Optimized Code}.
2458 Older versions of the @sc{gnu} C compiler permitted a variant option
2459 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2460 format; if your @sc{gnu} C compiler has this option, do not use it.
2462 @value{GDBN} knows about preprocessor macros and can show you their
2463 expansion (@pxref{Macros}). Most compilers do not include information
2464 about preprocessor macros in the debugging information if you specify
2465 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2466 the @sc{gnu} C compiler, provides macro information if you are using
2467 the DWARF debugging format, and specify the option @option{-g3}.
2469 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2470 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2471 information on @value{NGCC} options affecting debug information.
2473 You will have the best debugging experience if you use the latest
2474 version of the DWARF debugging format that your compiler supports.
2475 DWARF is currently the most expressive and best supported debugging
2476 format in @value{GDBN}.
2480 @section Starting your Program
2486 @kindex r @r{(@code{run})}
2489 Use the @code{run} command to start your program under @value{GDBN}.
2490 You must first specify the program name with an argument to
2491 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2492 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2493 command (@pxref{Files, ,Commands to Specify Files}).
2497 If you are running your program in an execution environment that
2498 supports processes, @code{run} creates an inferior process and makes
2499 that process run your program. In some environments without processes,
2500 @code{run} jumps to the start of your program. Other targets,
2501 like @samp{remote}, are always running. If you get an error
2502 message like this one:
2505 The "remote" target does not support "run".
2506 Try "help target" or "continue".
2510 then use @code{continue} to run your program. You may need @code{load}
2511 first (@pxref{load}).
2513 The execution of a program is affected by certain information it
2514 receives from its superior. @value{GDBN} provides ways to specify this
2515 information, which you must do @emph{before} starting your program. (You
2516 can change it after starting your program, but such changes only affect
2517 your program the next time you start it.) This information may be
2518 divided into four categories:
2521 @item The @emph{arguments.}
2522 Specify the arguments to give your program as the arguments of the
2523 @code{run} command. If a shell is available on your target, the shell
2524 is used to pass the arguments, so that you may use normal conventions
2525 (such as wildcard expansion or variable substitution) in describing
2527 In Unix systems, you can control which shell is used with the
2528 @env{SHELL} environment variable. If you do not define @env{SHELL},
2529 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2530 use of any shell with the @code{set startup-with-shell} command (see
2533 @item The @emph{environment.}
2534 Your program normally inherits its environment from @value{GDBN}, but you can
2535 use the @value{GDBN} commands @code{set environment} and @code{unset
2536 environment} to change parts of the environment that affect
2537 your program. @xref{Environment, ,Your Program's Environment}.
2539 @item The @emph{working directory.}
2540 You can set your program's working directory with the command
2541 @kbd{set cwd}. If you do not set any working directory with this
2542 command, your program will inherit @value{GDBN}'s working directory if
2543 native debugging, or the remote server's working directory if remote
2544 debugging. @xref{Working Directory, ,Your Program's Working
2547 @item The @emph{standard input and output.}
2548 Your program normally uses the same device for standard input and
2549 standard output as @value{GDBN} is using. You can redirect input and output
2550 in the @code{run} command line, or you can use the @code{tty} command to
2551 set a different device for your program.
2552 @xref{Input/Output, ,Your Program's Input and Output}.
2555 @emph{Warning:} While input and output redirection work, you cannot use
2556 pipes to pass the output of the program you are debugging to another
2557 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2561 When you issue the @code{run} command, your program begins to execute
2562 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2563 of how to arrange for your program to stop. Once your program has
2564 stopped, you may call functions in your program, using the @code{print}
2565 or @code{call} commands. @xref{Data, ,Examining Data}.
2567 If the modification time of your symbol file has changed since the last
2568 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2569 table, and reads it again. When it does this, @value{GDBN} tries to retain
2570 your current breakpoints.
2575 @cindex run to main procedure
2576 The name of the main procedure can vary from language to language.
2577 With C or C@t{++}, the main procedure name is always @code{main}, but
2578 other languages such as Ada do not require a specific name for their
2579 main procedure. The debugger provides a convenient way to start the
2580 execution of the program and to stop at the beginning of the main
2581 procedure, depending on the language used.
2583 The @samp{start} command does the equivalent of setting a temporary
2584 breakpoint at the beginning of the main procedure and then invoking
2585 the @samp{run} command.
2587 @cindex elaboration phase
2588 Some programs contain an @dfn{elaboration} phase where some startup code is
2589 executed before the main procedure is called. This depends on the
2590 languages used to write your program. In C@t{++}, for instance,
2591 constructors for static and global objects are executed before
2592 @code{main} is called. It is therefore possible that the debugger stops
2593 before reaching the main procedure. However, the temporary breakpoint
2594 will remain to halt execution.
2596 Specify the arguments to give to your program as arguments to the
2597 @samp{start} command. These arguments will be given verbatim to the
2598 underlying @samp{run} command. Note that the same arguments will be
2599 reused if no argument is provided during subsequent calls to
2600 @samp{start} or @samp{run}.
2602 It is sometimes necessary to debug the program during elaboration. In
2603 these cases, using the @code{start} command would stop the execution
2604 of your program too late, as the program would have already completed
2605 the elaboration phase. Under these circumstances, either insert
2606 breakpoints in your elaboration code before running your program or
2607 use the @code{starti} command.
2611 @cindex run to first instruction
2612 The @samp{starti} command does the equivalent of setting a temporary
2613 breakpoint at the first instruction of a program's execution and then
2614 invoking the @samp{run} command. For programs containing an
2615 elaboration phase, the @code{starti} command will stop execution at
2616 the start of the elaboration phase.
2618 @anchor{set exec-wrapper}
2619 @kindex set exec-wrapper
2620 @item set exec-wrapper @var{wrapper}
2621 @itemx show exec-wrapper
2622 @itemx unset exec-wrapper
2623 When @samp{exec-wrapper} is set, the specified wrapper is used to
2624 launch programs for debugging. @value{GDBN} starts your program
2625 with a shell command of the form @kbd{exec @var{wrapper}
2626 @var{program}}. Quoting is added to @var{program} and its
2627 arguments, but not to @var{wrapper}, so you should add quotes if
2628 appropriate for your shell. The wrapper runs until it executes
2629 your program, and then @value{GDBN} takes control.
2631 You can use any program that eventually calls @code{execve} with
2632 its arguments as a wrapper. Several standard Unix utilities do
2633 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2634 with @code{exec "$@@"} will also work.
2636 For example, you can use @code{env} to pass an environment variable to
2637 the debugged program, without setting the variable in your shell's
2641 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2645 This command is available when debugging locally on most targets, excluding
2646 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2648 @kindex set startup-with-shell
2649 @anchor{set startup-with-shell}
2650 @item set startup-with-shell
2651 @itemx set startup-with-shell on
2652 @itemx set startup-with-shell off
2653 @itemx show startup-with-shell
2654 On Unix systems, by default, if a shell is available on your target,
2655 @value{GDBN}) uses it to start your program. Arguments of the
2656 @code{run} command are passed to the shell, which does variable
2657 substitution, expands wildcard characters and performs redirection of
2658 I/O. In some circumstances, it may be useful to disable such use of a
2659 shell, for example, when debugging the shell itself or diagnosing
2660 startup failures such as:
2664 Starting program: ./a.out
2665 During startup program terminated with signal SIGSEGV, Segmentation fault.
2669 which indicates the shell or the wrapper specified with
2670 @samp{exec-wrapper} crashed, not your program. Most often, this is
2671 caused by something odd in your shell's non-interactive mode
2672 initialization file---such as @file{.cshrc} for C-shell,
2673 $@file{.zshenv} for the Z shell, or the file specified in the
2674 @env{BASH_ENV} environment variable for BASH.
2676 @anchor{set auto-connect-native-target}
2677 @kindex set auto-connect-native-target
2678 @item set auto-connect-native-target
2679 @itemx set auto-connect-native-target on
2680 @itemx set auto-connect-native-target off
2681 @itemx show auto-connect-native-target
2683 By default, if the current inferior is not connected to any target yet
2684 (e.g., with @code{target remote}), the @code{run} command starts your
2685 program as a native process under @value{GDBN}, on your local machine.
2686 If you're sure you don't want to debug programs on your local machine,
2687 you can tell @value{GDBN} to not connect to the native target
2688 automatically with the @code{set auto-connect-native-target off}
2691 If @code{on}, which is the default, and if the current inferior is not
2692 connected to a target already, the @code{run} command automaticaly
2693 connects to the native target, if one is available.
2695 If @code{off}, and if the current inferior is not connected to a
2696 target already, the @code{run} command fails with an error:
2700 Don't know how to run. Try "help target".
2703 If the current inferior is already connected to a target, @value{GDBN}
2704 always uses it with the @code{run} command.
2706 In any case, you can explicitly connect to the native target with the
2707 @code{target native} command. For example,
2710 (@value{GDBP}) set auto-connect-native-target off
2712 Don't know how to run. Try "help target".
2713 (@value{GDBP}) target native
2715 Starting program: ./a.out
2716 [Inferior 1 (process 10421) exited normally]
2719 In case you connected explicitly to the @code{native} target,
2720 @value{GDBN} remains connected even if all inferiors exit, ready for
2721 the next @code{run} command. Use the @code{disconnect} command to
2724 Examples of other commands that likewise respect the
2725 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2726 proc}, @code{info os}.
2728 @kindex set disable-randomization
2729 @item set disable-randomization
2730 @itemx set disable-randomization on
2731 This option (enabled by default in @value{GDBN}) will turn off the native
2732 randomization of the virtual address space of the started program. This option
2733 is useful for multiple debugging sessions to make the execution better
2734 reproducible and memory addresses reusable across debugging sessions.
2736 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2737 On @sc{gnu}/Linux you can get the same behavior using
2740 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2743 @item set disable-randomization off
2744 Leave the behavior of the started executable unchanged. Some bugs rear their
2745 ugly heads only when the program is loaded at certain addresses. If your bug
2746 disappears when you run the program under @value{GDBN}, that might be because
2747 @value{GDBN} by default disables the address randomization on platforms, such
2748 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2749 disable-randomization off} to try to reproduce such elusive bugs.
2751 On targets where it is available, virtual address space randomization
2752 protects the programs against certain kinds of security attacks. In these
2753 cases the attacker needs to know the exact location of a concrete executable
2754 code. Randomizing its location makes it impossible to inject jumps misusing
2755 a code at its expected addresses.
2757 Prelinking shared libraries provides a startup performance advantage but it
2758 makes addresses in these libraries predictable for privileged processes by
2759 having just unprivileged access at the target system. Reading the shared
2760 library binary gives enough information for assembling the malicious code
2761 misusing it. Still even a prelinked shared library can get loaded at a new
2762 random address just requiring the regular relocation process during the
2763 startup. Shared libraries not already prelinked are always loaded at
2764 a randomly chosen address.
2766 Position independent executables (PIE) contain position independent code
2767 similar to the shared libraries and therefore such executables get loaded at
2768 a randomly chosen address upon startup. PIE executables always load even
2769 already prelinked shared libraries at a random address. You can build such
2770 executable using @command{gcc -fPIE -pie}.
2772 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2773 (as long as the randomization is enabled).
2775 @item show disable-randomization
2776 Show the current setting of the explicit disable of the native randomization of
2777 the virtual address space of the started program.
2782 @section Your Program's Arguments
2784 @cindex arguments (to your program)
2785 The arguments to your program can be specified by the arguments of the
2787 They are passed to a shell, which expands wildcard characters and
2788 performs redirection of I/O, and thence to your program. Your
2789 @env{SHELL} environment variable (if it exists) specifies what shell
2790 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2791 the default shell (@file{/bin/sh} on Unix).
2793 On non-Unix systems, the program is usually invoked directly by
2794 @value{GDBN}, which emulates I/O redirection via the appropriate system
2795 calls, and the wildcard characters are expanded by the startup code of
2796 the program, not by the shell.
2798 @code{run} with no arguments uses the same arguments used by the previous
2799 @code{run}, or those set by the @code{set args} command.
2804 Specify the arguments to be used the next time your program is run. If
2805 @code{set args} has no arguments, @code{run} executes your program
2806 with no arguments. Once you have run your program with arguments,
2807 using @code{set args} before the next @code{run} is the only way to run
2808 it again without arguments.
2812 Show the arguments to give your program when it is started.
2816 @section Your Program's Environment
2818 @cindex environment (of your program)
2819 The @dfn{environment} consists of a set of environment variables and
2820 their values. Environment variables conventionally record such things as
2821 your user name, your home directory, your terminal type, and your search
2822 path for programs to run. Usually you set up environment variables with
2823 the shell and they are inherited by all the other programs you run. When
2824 debugging, it can be useful to try running your program with a modified
2825 environment without having to start @value{GDBN} over again.
2829 @item path @var{directory}
2830 Add @var{directory} to the front of the @env{PATH} environment variable
2831 (the search path for executables) that will be passed to your program.
2832 The value of @env{PATH} used by @value{GDBN} does not change.
2833 You may specify several directory names, separated by whitespace or by a
2834 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2835 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2836 is moved to the front, so it is searched sooner.
2838 You can use the string @samp{$cwd} to refer to whatever is the current
2839 working directory at the time @value{GDBN} searches the path. If you
2840 use @samp{.} instead, it refers to the directory where you executed the
2841 @code{path} command. @value{GDBN} replaces @samp{.} in the
2842 @var{directory} argument (with the current path) before adding
2843 @var{directory} to the search path.
2844 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2845 @c document that, since repeating it would be a no-op.
2849 Display the list of search paths for executables (the @env{PATH}
2850 environment variable).
2852 @kindex show environment
2853 @item show environment @r{[}@var{varname}@r{]}
2854 Print the value of environment variable @var{varname} to be given to
2855 your program when it starts. If you do not supply @var{varname},
2856 print the names and values of all environment variables to be given to
2857 your program. You can abbreviate @code{environment} as @code{env}.
2859 @kindex set environment
2860 @anchor{set environment}
2861 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2862 Set environment variable @var{varname} to @var{value}. The value
2863 changes for your program (and the shell @value{GDBN} uses to launch
2864 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2865 values of environment variables are just strings, and any
2866 interpretation is supplied by your program itself. The @var{value}
2867 parameter is optional; if it is eliminated, the variable is set to a
2869 @c "any string" here does not include leading, trailing
2870 @c blanks. Gnu asks: does anyone care?
2872 For example, this command:
2879 tells the debugged program, when subsequently run, that its user is named
2880 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2881 are not actually required.)
2883 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2884 which also inherits the environment set with @code{set environment}.
2885 If necessary, you can avoid that by using the @samp{env} program as a
2886 wrapper instead of using @code{set environment}. @xref{set
2887 exec-wrapper}, for an example doing just that.
2889 Environment variables that are set by the user are also transmitted to
2890 @command{gdbserver} to be used when starting the remote inferior.
2891 @pxref{QEnvironmentHexEncoded}.
2893 @kindex unset environment
2894 @anchor{unset environment}
2895 @item unset environment @var{varname}
2896 Remove variable @var{varname} from the environment to be passed to your
2897 program. This is different from @samp{set env @var{varname} =};
2898 @code{unset environment} removes the variable from the environment,
2899 rather than assigning it an empty value.
2901 Environment variables that are unset by the user are also unset on
2902 @command{gdbserver} when starting the remote inferior.
2903 @pxref{QEnvironmentUnset}.
2906 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2907 the shell indicated by your @env{SHELL} environment variable if it
2908 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2909 names a shell that runs an initialization file when started
2910 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2911 for the Z shell, or the file specified in the @env{BASH_ENV}
2912 environment variable for BASH---any variables you set in that file
2913 affect your program. You may wish to move setting of environment
2914 variables to files that are only run when you sign on, such as
2915 @file{.login} or @file{.profile}.
2917 @node Working Directory
2918 @section Your Program's Working Directory
2920 @cindex working directory (of your program)
2921 Each time you start your program with @code{run}, the inferior will be
2922 initialized with the current working directory specified by the
2923 @kbd{set cwd} command. If no directory has been specified by this
2924 command, then the inferior will inherit @value{GDBN}'s current working
2925 directory as its working directory if native debugging, or it will
2926 inherit the remote server's current working directory if remote
2931 @cindex change inferior's working directory
2932 @anchor{set cwd command}
2933 @item set cwd @r{[}@var{directory}@r{]}
2934 Set the inferior's working directory to @var{directory}, which will be
2935 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2936 argument has been specified, the command clears the setting and resets
2937 it to an empty state. This setting has no effect on @value{GDBN}'s
2938 working directory, and it only takes effect the next time you start
2939 the inferior. The @file{~} in @var{directory} is a short for the
2940 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2941 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2942 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2945 You can also change @value{GDBN}'s current working directory by using
2946 the @code{cd} command.
2950 @cindex show inferior's working directory
2952 Show the inferior's working directory. If no directory has been
2953 specified by @kbd{set cwd}, then the default inferior's working
2954 directory is the same as @value{GDBN}'s working directory.
2957 @cindex change @value{GDBN}'s working directory
2959 @item cd @r{[}@var{directory}@r{]}
2960 Set the @value{GDBN} working directory to @var{directory}. If not
2961 given, @var{directory} uses @file{'~'}.
2963 The @value{GDBN} working directory serves as a default for the
2964 commands that specify files for @value{GDBN} to operate on.
2965 @xref{Files, ,Commands to Specify Files}.
2966 @xref{set cwd command}.
2970 Print the @value{GDBN} working directory.
2973 It is generally impossible to find the current working directory of
2974 the process being debugged (since a program can change its directory
2975 during its run). If you work on a system where @value{GDBN} supports
2976 the @code{info proc} command (@pxref{Process Information}), you can
2977 use the @code{info proc} command to find out the
2978 current working directory of the debuggee.
2981 @section Your Program's Input and Output
2986 By default, the program you run under @value{GDBN} does input and output to
2987 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2988 to its own terminal modes to interact with you, but it records the terminal
2989 modes your program was using and switches back to them when you continue
2990 running your program.
2993 @kindex info terminal
2995 Displays information recorded by @value{GDBN} about the terminal modes your
2999 You can redirect your program's input and/or output using shell
3000 redirection with the @code{run} command. For example,
3007 starts your program, diverting its output to the file @file{outfile}.
3010 @cindex controlling terminal
3011 Another way to specify where your program should do input and output is
3012 with the @code{tty} command. This command accepts a file name as
3013 argument, and causes this file to be the default for future @code{run}
3014 commands. It also resets the controlling terminal for the child
3015 process, for future @code{run} commands. For example,
3022 directs that processes started with subsequent @code{run} commands
3023 default to do input and output on the terminal @file{/dev/ttyb} and have
3024 that as their controlling terminal.
3026 An explicit redirection in @code{run} overrides the @code{tty} command's
3027 effect on the input/output device, but not its effect on the controlling
3030 When you use the @code{tty} command or redirect input in the @code{run}
3031 command, only the input @emph{for your program} is affected. The input
3032 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3033 for @code{set inferior-tty}.
3035 @cindex inferior tty
3036 @cindex set inferior controlling terminal
3037 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3038 display the name of the terminal that will be used for future runs of your
3042 @item set inferior-tty [ @var{tty} ]
3043 @kindex set inferior-tty
3044 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3045 restores the default behavior, which is to use the same terminal as
3048 @item show inferior-tty
3049 @kindex show inferior-tty
3050 Show the current tty for the program being debugged.
3054 @section Debugging an Already-running Process
3059 @item attach @var{process-id}
3060 This command attaches to a running process---one that was started
3061 outside @value{GDBN}. (@code{info files} shows your active
3062 targets.) The command takes as argument a process ID. The usual way to
3063 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3064 or with the @samp{jobs -l} shell command.
3066 @code{attach} does not repeat if you press @key{RET} a second time after
3067 executing the command.
3070 To use @code{attach}, your program must be running in an environment
3071 which supports processes; for example, @code{attach} does not work for
3072 programs on bare-board targets that lack an operating system. You must
3073 also have permission to send the process a signal.
3075 When you use @code{attach}, the debugger finds the program running in
3076 the process first by looking in the current working directory, then (if
3077 the program is not found) by using the source file search path
3078 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3079 the @code{file} command to load the program. @xref{Files, ,Commands to
3082 @anchor{set exec-file-mismatch}
3083 If the debugger can determine that the executable file running in the
3084 process it is attaching to does not match the current exec-file loaded
3085 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3086 handle the mismatch. @value{GDBN} tries to compare the files by
3087 comparing their build IDs (@pxref{build ID}), if available.
3090 @kindex exec-file-mismatch
3091 @cindex set exec-file-mismatch
3092 @item set exec-file-mismatch @samp{ask|warn|off}
3094 Whether to detect mismatch between the current executable file loaded
3095 by @value{GDBN} and the executable file used to start the process. If
3096 @samp{ask}, the default, display a warning and ask the user whether to
3097 load the process executable file; if @samp{warn}, just display a
3098 warning; if @samp{off}, don't attempt to detect a mismatch.
3099 If the user confirms loading the process executable file, then its symbols
3100 will be loaded as well.
3102 @cindex show exec-file-mismatch
3103 @item show exec-file-mismatch
3104 Show the current value of @code{exec-file-mismatch}.
3108 The first thing @value{GDBN} does after arranging to debug the specified
3109 process is to stop it. You can examine and modify an attached process
3110 with all the @value{GDBN} commands that are ordinarily available when
3111 you start processes with @code{run}. You can insert breakpoints; you
3112 can step and continue; you can modify storage. If you would rather the
3113 process continue running, you may use the @code{continue} command after
3114 attaching @value{GDBN} to the process.
3119 When you have finished debugging the attached process, you can use the
3120 @code{detach} command to release it from @value{GDBN} control. Detaching
3121 the process continues its execution. After the @code{detach} command,
3122 that process and @value{GDBN} become completely independent once more, and you
3123 are ready to @code{attach} another process or start one with @code{run}.
3124 @code{detach} does not repeat if you press @key{RET} again after
3125 executing the command.
3128 If you exit @value{GDBN} while you have an attached process, you detach
3129 that process. If you use the @code{run} command, you kill that process.
3130 By default, @value{GDBN} asks for confirmation if you try to do either of these
3131 things; you can control whether or not you need to confirm by using the
3132 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3136 @section Killing the Child Process
3141 Kill the child process in which your program is running under @value{GDBN}.
3144 This command is useful if you wish to debug a core dump instead of a
3145 running process. @value{GDBN} ignores any core dump file while your program
3148 On some operating systems, a program cannot be executed outside @value{GDBN}
3149 while you have breakpoints set on it inside @value{GDBN}. You can use the
3150 @code{kill} command in this situation to permit running your program
3151 outside the debugger.
3153 The @code{kill} command is also useful if you wish to recompile and
3154 relink your program, since on many systems it is impossible to modify an
3155 executable file while it is running in a process. In this case, when you
3156 next type @code{run}, @value{GDBN} notices that the file has changed, and
3157 reads the symbol table again (while trying to preserve your current
3158 breakpoint settings).
3160 @node Inferiors Connections and Programs
3161 @section Debugging Multiple Inferiors Connections and Programs
3163 @value{GDBN} lets you run and debug multiple programs in a single
3164 session. In addition, @value{GDBN} on some systems may let you run
3165 several programs simultaneously (otherwise you have to exit from one
3166 before starting another). On some systems @value{GDBN} may even let
3167 you debug several programs simultaneously on different remote systems.
3168 In the most general case, you can have multiple threads of execution
3169 in each of multiple processes, launched from multiple executables,
3170 running on different machines.
3173 @value{GDBN} represents the state of each program execution with an
3174 object called an @dfn{inferior}. An inferior typically corresponds to
3175 a process, but is more general and applies also to targets that do not
3176 have processes. Inferiors may be created before a process runs, and
3177 may be retained after a process exits. Inferiors have unique
3178 identifiers that are different from process ids. Usually each
3179 inferior will also have its own distinct address space, although some
3180 embedded targets may have several inferiors running in different parts
3181 of a single address space. Each inferior may in turn have multiple
3182 threads running in it.
3184 To find out what inferiors exist at any moment, use @w{@code{info
3188 @kindex info inferiors [ @var{id}@dots{} ]
3189 @item info inferiors
3190 Print a list of all inferiors currently being managed by @value{GDBN}.
3191 By default all inferiors are printed, but the argument @var{id}@dots{}
3192 -- a space separated list of inferior numbers -- can be used to limit
3193 the display to just the requested inferiors.
3195 @value{GDBN} displays for each inferior (in this order):
3199 the inferior number assigned by @value{GDBN}
3202 the target system's inferior identifier
3205 the target connection the inferior is bound to, including the unique
3206 connection number assigned by @value{GDBN}, and the protocol used by
3210 the name of the executable the inferior is running.
3215 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3216 indicates the current inferior.
3220 @c end table here to get a little more width for example
3223 (@value{GDBP}) info inferiors
3224 Num Description Connection Executable
3225 * 1 process 3401 1 (native) goodbye
3226 2 process 2307 2 (extended-remote host:10000) hello
3229 To get informations about the current inferior, use @code{inferior}:
3234 Shows information about the current inferior.
3238 @c end table here to get a little more width for example
3241 (@value{GDBP}) inferior
3242 [Current inferior is 1 [process 3401] (helloworld)]
3245 To find out what open target connections exist at any moment, use
3246 @w{@code{info connections}}:
3249 @kindex info connections [ @var{id}@dots{} ]
3250 @item info connections
3251 Print a list of all open target connections currently being managed by
3252 @value{GDBN}. By default all connections are printed, but the
3253 argument @var{id}@dots{} -- a space separated list of connections
3254 numbers -- can be used to limit the display to just the requested
3257 @value{GDBN} displays for each connection (in this order):
3261 the connection number assigned by @value{GDBN}.
3264 the protocol used by the connection.
3267 a textual description of the protocol used by the connection.
3272 An asterisk @samp{*} preceding the connection number indicates the
3273 connection of the current inferior.
3277 @c end table here to get a little more width for example
3280 (@value{GDBP}) info connections
3281 Num What Description
3282 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3283 2 native Native process
3284 3 core Local core dump file
3287 To switch focus between inferiors, use the @code{inferior} command:
3290 @kindex inferior @var{infno}
3291 @item inferior @var{infno}
3292 Make inferior number @var{infno} the current inferior. The argument
3293 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3294 in the first field of the @samp{info inferiors} display.
3297 @vindex $_inferior@r{, convenience variable}
3298 The debugger convenience variable @samp{$_inferior} contains the
3299 number of the current inferior. You may find this useful in writing
3300 breakpoint conditional expressions, command scripts, and so forth.
3301 @xref{Convenience Vars,, Convenience Variables}, for general
3302 information on convenience variables.
3304 You can get multiple executables into a debugging session via the
3305 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3306 systems @value{GDBN} can add inferiors to the debug session
3307 automatically by following calls to @code{fork} and @code{exec}. To
3308 remove inferiors from the debugging session use the
3309 @w{@code{remove-inferiors}} command.
3312 @kindex add-inferior
3313 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3314 Adds @var{n} inferiors to be run using @var{executable} as the
3315 executable; @var{n} defaults to 1. If no executable is specified,
3316 the inferiors begins empty, with no program. You can still assign or
3317 change the program assigned to the inferior at any time by using the
3318 @code{file} command with the executable name as its argument.
3320 By default, the new inferior begins connected to the same target
3321 connection as the current inferior. For example, if the current
3322 inferior was connected to @code{gdbserver} with @code{target remote},
3323 then the new inferior will be connected to the same @code{gdbserver}
3324 instance. The @samp{-no-connection} option starts the new inferior
3325 with no connection yet. You can then for example use the @code{target
3326 remote} command to connect to some other @code{gdbserver} instance,
3327 use @code{run} to spawn a local program, etc.
3329 @kindex clone-inferior
3330 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3331 Adds @var{n} inferiors ready to execute the same program as inferior
3332 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3333 number of the current inferior. This is a convenient command when you
3334 want to run another instance of the inferior you are debugging.
3337 (@value{GDBP}) info inferiors
3338 Num Description Connection Executable
3339 * 1 process 29964 1 (native) helloworld
3340 (@value{GDBP}) clone-inferior
3343 (@value{GDBP}) info inferiors
3344 Num Description Connection Executable
3345 * 1 process 29964 1 (native) helloworld
3346 2 <null> 1 (native) helloworld
3349 You can now simply switch focus to inferior 2 and run it.
3351 @kindex remove-inferiors
3352 @item remove-inferiors @var{infno}@dots{}
3353 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3354 possible to remove an inferior that is running with this command. For
3355 those, use the @code{kill} or @code{detach} command first.
3359 To quit debugging one of the running inferiors that is not the current
3360 inferior, you can either detach from it by using the @w{@code{detach
3361 inferior}} command (allowing it to run independently), or kill it
3362 using the @w{@code{kill inferiors}} command:
3365 @kindex detach inferiors @var{infno}@dots{}
3366 @item detach inferior @var{infno}@dots{}
3367 Detach from the inferior or inferiors identified by @value{GDBN}
3368 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3369 still stays on the list of inferiors shown by @code{info inferiors},
3370 but its Description will show @samp{<null>}.
3372 @kindex kill inferiors @var{infno}@dots{}
3373 @item kill inferiors @var{infno}@dots{}
3374 Kill the inferior or inferiors identified by @value{GDBN} inferior
3375 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3376 stays on the list of inferiors shown by @code{info inferiors}, but its
3377 Description will show @samp{<null>}.
3380 After the successful completion of a command such as @code{detach},
3381 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3382 a normal process exit, the inferior is still valid and listed with
3383 @code{info inferiors}, ready to be restarted.
3386 To be notified when inferiors are started or exit under @value{GDBN}'s
3387 control use @w{@code{set print inferior-events}}:
3390 @kindex set print inferior-events
3391 @cindex print messages on inferior start and exit
3392 @item set print inferior-events
3393 @itemx set print inferior-events on
3394 @itemx set print inferior-events off
3395 The @code{set print inferior-events} command allows you to enable or
3396 disable printing of messages when @value{GDBN} notices that new
3397 inferiors have started or that inferiors have exited or have been
3398 detached. By default, these messages will not be printed.
3400 @kindex show print inferior-events
3401 @item show print inferior-events
3402 Show whether messages will be printed when @value{GDBN} detects that
3403 inferiors have started, exited or have been detached.
3406 Many commands will work the same with multiple programs as with a
3407 single program: e.g., @code{print myglobal} will simply display the
3408 value of @code{myglobal} in the current inferior.
3411 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3412 get more info about the relationship of inferiors, programs, address
3413 spaces in a debug session. You can do that with the @w{@code{maint
3414 info program-spaces}} command.
3417 @kindex maint info program-spaces
3418 @item maint info program-spaces
3419 Print a list of all program spaces currently being managed by
3422 @value{GDBN} displays for each program space (in this order):
3426 the program space number assigned by @value{GDBN}
3429 the name of the executable loaded into the program space, with e.g.,
3430 the @code{file} command.
3435 An asterisk @samp{*} preceding the @value{GDBN} program space number
3436 indicates the current program space.
3438 In addition, below each program space line, @value{GDBN} prints extra
3439 information that isn't suitable to display in tabular form. For
3440 example, the list of inferiors bound to the program space.
3443 (@value{GDBP}) maint info program-spaces
3447 Bound inferiors: ID 1 (process 21561)
3450 Here we can see that no inferior is running the program @code{hello},
3451 while @code{process 21561} is running the program @code{goodbye}. On
3452 some targets, it is possible that multiple inferiors are bound to the
3453 same program space. The most common example is that of debugging both
3454 the parent and child processes of a @code{vfork} call. For example,
3457 (@value{GDBP}) maint info program-spaces
3460 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3463 Here, both inferior 2 and inferior 1 are running in the same program
3464 space as a result of inferior 1 having executed a @code{vfork} call.
3468 @section Debugging Programs with Multiple Threads
3470 @cindex threads of execution
3471 @cindex multiple threads
3472 @cindex switching threads
3473 In some operating systems, such as GNU/Linux and Solaris, a single program
3474 may have more than one @dfn{thread} of execution. The precise semantics
3475 of threads differ from one operating system to another, but in general
3476 the threads of a single program are akin to multiple processes---except
3477 that they share one address space (that is, they can all examine and
3478 modify the same variables). On the other hand, each thread has its own
3479 registers and execution stack, and perhaps private memory.
3481 @value{GDBN} provides these facilities for debugging multi-thread
3485 @item automatic notification of new threads
3486 @item @samp{thread @var{thread-id}}, a command to switch among threads
3487 @item @samp{info threads}, a command to inquire about existing threads
3488 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3489 a command to apply a command to a list of threads
3490 @item thread-specific breakpoints
3491 @item @samp{set print thread-events}, which controls printing of
3492 messages on thread start and exit.
3493 @item @samp{set libthread-db-search-path @var{path}}, which lets
3494 the user specify which @code{libthread_db} to use if the default choice
3495 isn't compatible with the program.
3498 @cindex focus of debugging
3499 @cindex current thread
3500 The @value{GDBN} thread debugging facility allows you to observe all
3501 threads while your program runs---but whenever @value{GDBN} takes
3502 control, one thread in particular is always the focus of debugging.
3503 This thread is called the @dfn{current thread}. Debugging commands show
3504 program information from the perspective of the current thread.
3506 @cindex @code{New} @var{systag} message
3507 @cindex thread identifier (system)
3508 @c FIXME-implementors!! It would be more helpful if the [New...] message
3509 @c included GDB's numeric thread handle, so you could just go to that
3510 @c thread without first checking `info threads'.
3511 Whenever @value{GDBN} detects a new thread in your program, it displays
3512 the target system's identification for the thread with a message in the
3513 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3514 whose form varies depending on the particular system. For example, on
3515 @sc{gnu}/Linux, you might see
3518 [New Thread 0x41e02940 (LWP 25582)]
3522 when @value{GDBN} notices a new thread. In contrast, on other systems,
3523 the @var{systag} is simply something like @samp{process 368}, with no
3526 @c FIXME!! (1) Does the [New...] message appear even for the very first
3527 @c thread of a program, or does it only appear for the
3528 @c second---i.e.@: when it becomes obvious we have a multithread
3530 @c (2) *Is* there necessarily a first thread always? Or do some
3531 @c multithread systems permit starting a program with multiple
3532 @c threads ab initio?
3534 @anchor{thread numbers}
3535 @cindex thread number, per inferior
3536 @cindex thread identifier (GDB)
3537 For debugging purposes, @value{GDBN} associates its own thread number
3538 ---always a single integer---with each thread of an inferior. This
3539 number is unique between all threads of an inferior, but not unique
3540 between threads of different inferiors.
3542 @cindex qualified thread ID
3543 You can refer to a given thread in an inferior using the qualified
3544 @var{inferior-num}.@var{thread-num} syntax, also known as
3545 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3546 number and @var{thread-num} being the thread number of the given
3547 inferior. For example, thread @code{2.3} refers to thread number 3 of
3548 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3549 then @value{GDBN} infers you're referring to a thread of the current
3552 Until you create a second inferior, @value{GDBN} does not show the
3553 @var{inferior-num} part of thread IDs, even though you can always use
3554 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3555 of inferior 1, the initial inferior.
3557 @anchor{thread ID lists}
3558 @cindex thread ID lists
3559 Some commands accept a space-separated @dfn{thread ID list} as
3560 argument. A list element can be:
3564 A thread ID as shown in the first field of the @samp{info threads}
3565 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3569 A range of thread numbers, again with or without an inferior
3570 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3571 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3574 All threads of an inferior, specified with a star wildcard, with or
3575 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3576 @samp{1.*}) or @code{*}. The former refers to all threads of the
3577 given inferior, and the latter form without an inferior qualifier
3578 refers to all threads of the current inferior.
3582 For example, if the current inferior is 1, and inferior 7 has one
3583 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3584 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3585 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3586 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3590 @anchor{global thread numbers}
3591 @cindex global thread number
3592 @cindex global thread identifier (GDB)
3593 In addition to a @emph{per-inferior} number, each thread is also
3594 assigned a unique @emph{global} number, also known as @dfn{global
3595 thread ID}, a single integer. Unlike the thread number component of
3596 the thread ID, no two threads have the same global ID, even when
3597 you're debugging multiple inferiors.
3599 From @value{GDBN}'s perspective, a process always has at least one
3600 thread. In other words, @value{GDBN} assigns a thread number to the
3601 program's ``main thread'' even if the program is not multi-threaded.
3603 @vindex $_thread@r{, convenience variable}
3604 @vindex $_gthread@r{, convenience variable}
3605 The debugger convenience variables @samp{$_thread} and
3606 @samp{$_gthread} contain, respectively, the per-inferior thread number
3607 and the global thread number of the current thread. You may find this
3608 useful in writing breakpoint conditional expressions, command scripts,
3609 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3610 general information on convenience variables.
3612 If @value{GDBN} detects the program is multi-threaded, it augments the
3613 usual message about stopping at a breakpoint with the ID and name of
3614 the thread that hit the breakpoint.
3617 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3620 Likewise when the program receives a signal:
3623 Thread 1 "main" received signal SIGINT, Interrupt.
3627 @kindex info threads
3628 @item info threads @r{[}@var{thread-id-list}@r{]}
3630 Display information about one or more threads. With no arguments
3631 displays information about all threads. You can specify the list of
3632 threads that you want to display using the thread ID list syntax
3633 (@pxref{thread ID lists}).
3635 @value{GDBN} displays for each thread (in this order):
3639 the per-inferior thread number assigned by @value{GDBN}
3642 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3643 option was specified
3646 the target system's thread identifier (@var{systag})
3649 the thread's name, if one is known. A thread can either be named by
3650 the user (see @code{thread name}, below), or, in some cases, by the
3654 the current stack frame summary for that thread
3658 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3659 indicates the current thread.
3663 @c end table here to get a little more width for example
3666 (@value{GDBP}) info threads
3668 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3669 2 process 35 thread 23 0x34e5 in sigpause ()
3670 3 process 35 thread 27 0x34e5 in sigpause ()
3674 If you're debugging multiple inferiors, @value{GDBN} displays thread
3675 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3676 Otherwise, only @var{thread-num} is shown.
3678 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3679 indicating each thread's global thread ID:
3682 (@value{GDBP}) info threads
3683 Id GId Target Id Frame
3684 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3685 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3686 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3687 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3690 On Solaris, you can display more information about user threads with a
3691 Solaris-specific command:
3694 @item maint info sol-threads
3695 @kindex maint info sol-threads
3696 @cindex thread info (Solaris)
3697 Display info on Solaris user threads.
3701 @kindex thread @var{thread-id}
3702 @item thread @var{thread-id}
3703 Make thread ID @var{thread-id} the current thread. The command
3704 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3705 the first field of the @samp{info threads} display, with or without an
3706 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3708 @value{GDBN} responds by displaying the system identifier of the
3709 thread you selected, and its current stack frame summary:
3712 (@value{GDBP}) thread 2
3713 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3714 #0 some_function (ignore=0x0) at example.c:8
3715 8 printf ("hello\n");
3719 As with the @samp{[New @dots{}]} message, the form of the text after
3720 @samp{Switching to} depends on your system's conventions for identifying
3723 @anchor{thread apply all}
3724 @kindex thread apply
3725 @cindex apply command to several threads
3726 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3727 The @code{thread apply} command allows you to apply the named
3728 @var{command} to one or more threads. Specify the threads that you
3729 want affected using the thread ID list syntax (@pxref{thread ID
3730 lists}), or specify @code{all} to apply to all threads. To apply a
3731 command to all threads in descending order, type @kbd{thread apply all
3732 @var{command}}. To apply a command to all threads in ascending order,
3733 type @kbd{thread apply all -ascending @var{command}}.
3735 The @var{flag} arguments control what output to produce and how to handle
3736 errors raised when applying @var{command} to a thread. @var{flag}
3737 must start with a @code{-} directly followed by one letter in
3738 @code{qcs}. If several flags are provided, they must be given
3739 individually, such as @code{-c -q}.
3741 By default, @value{GDBN} displays some thread information before the
3742 output produced by @var{command}, and an error raised during the
3743 execution of a @var{command} will abort @code{thread apply}. The
3744 following flags can be used to fine-tune this behavior:
3748 The flag @code{-c}, which stands for @samp{continue}, causes any
3749 errors in @var{command} to be displayed, and the execution of
3750 @code{thread apply} then continues.
3752 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3753 or empty output produced by a @var{command} to be silently ignored.
3754 That is, the execution continues, but the thread information and errors
3757 The flag @code{-q} (@samp{quiet}) disables printing the thread
3761 Flags @code{-c} and @code{-s} cannot be used together.
3764 @cindex apply command to all threads (ignoring errors and empty output)
3765 @item taas [@var{option}]@dots{} @var{command}
3766 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3767 Applies @var{command} on all threads, ignoring errors and empty output.
3769 The @code{taas} command accepts the same options as the @code{thread
3770 apply all} command. @xref{thread apply all}.
3773 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3774 @item tfaas [@var{option}]@dots{} @var{command}
3775 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3776 Applies @var{command} on all frames of all threads, ignoring errors
3777 and empty output. Note that the flag @code{-s} is specified twice:
3778 The first @code{-s} ensures that @code{thread apply} only shows the thread
3779 information of the threads for which @code{frame apply} produces
3780 some output. The second @code{-s} is needed to ensure that @code{frame
3781 apply} shows the frame information of a frame only if the
3782 @var{command} successfully produced some output.
3784 It can for example be used to print a local variable or a function
3785 argument without knowing the thread or frame where this variable or argument
3788 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3791 The @code{tfaas} command accepts the same options as the @code{frame
3792 apply} command. @xref{Frame Apply,,frame apply}.
3795 @cindex name a thread
3796 @item thread name [@var{name}]
3797 This command assigns a name to the current thread. If no argument is
3798 given, any existing user-specified name is removed. The thread name
3799 appears in the @samp{info threads} display.
3801 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3802 determine the name of the thread as given by the OS. On these
3803 systems, a name specified with @samp{thread name} will override the
3804 system-give name, and removing the user-specified name will cause
3805 @value{GDBN} to once again display the system-specified name.
3808 @cindex search for a thread
3809 @item thread find [@var{regexp}]
3810 Search for and display thread ids whose name or @var{systag}
3811 matches the supplied regular expression.
3813 As well as being the complement to the @samp{thread name} command,
3814 this command also allows you to identify a thread by its target
3815 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3819 (@value{GDBN}) thread find 26688
3820 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3821 (@value{GDBN}) info thread 4
3823 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3826 @kindex set print thread-events
3827 @cindex print messages on thread start and exit
3828 @item set print thread-events
3829 @itemx set print thread-events on
3830 @itemx set print thread-events off
3831 The @code{set print thread-events} command allows you to enable or
3832 disable printing of messages when @value{GDBN} notices that new threads have
3833 started or that threads have exited. By default, these messages will
3834 be printed if detection of these events is supported by the target.
3835 Note that these messages cannot be disabled on all targets.
3837 @kindex show print thread-events
3838 @item show print thread-events
3839 Show whether messages will be printed when @value{GDBN} detects that threads
3840 have started and exited.
3843 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3844 more information about how @value{GDBN} behaves when you stop and start
3845 programs with multiple threads.
3847 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3848 watchpoints in programs with multiple threads.
3850 @anchor{set libthread-db-search-path}
3852 @kindex set libthread-db-search-path
3853 @cindex search path for @code{libthread_db}
3854 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3855 If this variable is set, @var{path} is a colon-separated list of
3856 directories @value{GDBN} will use to search for @code{libthread_db}.
3857 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3858 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3859 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3862 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3863 @code{libthread_db} library to obtain information about threads in the
3864 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3865 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3866 specific thread debugging library loading is enabled
3867 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3869 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3870 refers to the default system directories that are
3871 normally searched for loading shared libraries. The @samp{$sdir} entry
3872 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3873 (@pxref{libthread_db.so.1 file}).
3875 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3876 refers to the directory from which @code{libpthread}
3877 was loaded in the inferior process.
3879 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3880 @value{GDBN} attempts to initialize it with the current inferior process.
3881 If this initialization fails (which could happen because of a version
3882 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3883 will unload @code{libthread_db}, and continue with the next directory.
3884 If none of @code{libthread_db} libraries initialize successfully,
3885 @value{GDBN} will issue a warning and thread debugging will be disabled.
3887 Setting @code{libthread-db-search-path} is currently implemented
3888 only on some platforms.
3890 @kindex show libthread-db-search-path
3891 @item show libthread-db-search-path
3892 Display current libthread_db search path.
3894 @kindex set debug libthread-db
3895 @kindex show debug libthread-db
3896 @cindex debugging @code{libthread_db}
3897 @item set debug libthread-db
3898 @itemx show debug libthread-db
3899 Turns on or off display of @code{libthread_db}-related events.
3900 Use @code{1} to enable, @code{0} to disable.
3904 @section Debugging Forks
3906 @cindex fork, debugging programs which call
3907 @cindex multiple processes
3908 @cindex processes, multiple
3909 On most systems, @value{GDBN} has no special support for debugging
3910 programs which create additional processes using the @code{fork}
3911 function. When a program forks, @value{GDBN} will continue to debug the
3912 parent process and the child process will run unimpeded. If you have
3913 set a breakpoint in any code which the child then executes, the child
3914 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3915 will cause it to terminate.
3917 However, if you want to debug the child process there is a workaround
3918 which isn't too painful. Put a call to @code{sleep} in the code which
3919 the child process executes after the fork. It may be useful to sleep
3920 only if a certain environment variable is set, or a certain file exists,
3921 so that the delay need not occur when you don't want to run @value{GDBN}
3922 on the child. While the child is sleeping, use the @code{ps} program to
3923 get its process ID. Then tell @value{GDBN} (a new invocation of
3924 @value{GDBN} if you are also debugging the parent process) to attach to
3925 the child process (@pxref{Attach}). From that point on you can debug
3926 the child process just like any other process which you attached to.
3928 On some systems, @value{GDBN} provides support for debugging programs
3929 that create additional processes using the @code{fork} or @code{vfork}
3930 functions. On @sc{gnu}/Linux platforms, this feature is supported
3931 with kernel version 2.5.46 and later.
3933 The fork debugging commands are supported in native mode and when
3934 connected to @code{gdbserver} in either @code{target remote} mode or
3935 @code{target extended-remote} mode.
3937 By default, when a program forks, @value{GDBN} will continue to debug
3938 the parent process and the child process will run unimpeded.
3940 If you want to follow the child process instead of the parent process,
3941 use the command @w{@code{set follow-fork-mode}}.
3944 @kindex set follow-fork-mode
3945 @item set follow-fork-mode @var{mode}
3946 Set the debugger response to a program call of @code{fork} or
3947 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3948 process. The @var{mode} argument can be:
3952 The original process is debugged after a fork. The child process runs
3953 unimpeded. This is the default.
3956 The new process is debugged after a fork. The parent process runs
3961 @kindex show follow-fork-mode
3962 @item show follow-fork-mode
3963 Display the current debugger response to a @code{fork} or @code{vfork} call.
3966 @cindex debugging multiple processes
3967 On Linux, if you want to debug both the parent and child processes, use the
3968 command @w{@code{set detach-on-fork}}.
3971 @kindex set detach-on-fork
3972 @item set detach-on-fork @var{mode}
3973 Tells gdb whether to detach one of the processes after a fork, or
3974 retain debugger control over them both.
3978 The child process (or parent process, depending on the value of
3979 @code{follow-fork-mode}) will be detached and allowed to run
3980 independently. This is the default.
3983 Both processes will be held under the control of @value{GDBN}.
3984 One process (child or parent, depending on the value of
3985 @code{follow-fork-mode}) is debugged as usual, while the other
3990 @kindex show detach-on-fork
3991 @item show detach-on-fork
3992 Show whether detach-on-fork mode is on/off.
3995 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3996 will retain control of all forked processes (including nested forks).
3997 You can list the forked processes under the control of @value{GDBN} by
3998 using the @w{@code{info inferiors}} command, and switch from one fork
3999 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4000 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4002 To quit debugging one of the forked processes, you can either detach
4003 from it by using the @w{@code{detach inferiors}} command (allowing it
4004 to run independently), or kill it using the @w{@code{kill inferiors}}
4005 command. @xref{Inferiors Connections and Programs, ,Debugging
4006 Multiple Inferiors Connections and Programs}.
4008 If you ask to debug a child process and a @code{vfork} is followed by an
4009 @code{exec}, @value{GDBN} executes the new target up to the first
4010 breakpoint in the new target. If you have a breakpoint set on
4011 @code{main} in your original program, the breakpoint will also be set on
4012 the child process's @code{main}.
4014 On some systems, when a child process is spawned by @code{vfork}, you
4015 cannot debug the child or parent until an @code{exec} call completes.
4017 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4018 call executes, the new target restarts. To restart the parent
4019 process, use the @code{file} command with the parent executable name
4020 as its argument. By default, after an @code{exec} call executes,
4021 @value{GDBN} discards the symbols of the previous executable image.
4022 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4026 @kindex set follow-exec-mode
4027 @item set follow-exec-mode @var{mode}
4029 Set debugger response to a program call of @code{exec}. An
4030 @code{exec} call replaces the program image of a process.
4032 @code{follow-exec-mode} can be:
4036 @value{GDBN} creates a new inferior and rebinds the process to this
4037 new inferior. The program the process was running before the
4038 @code{exec} call can be restarted afterwards by restarting the
4044 (@value{GDBP}) info inferiors
4046 Id Description Executable
4049 process 12020 is executing new program: prog2
4050 Program exited normally.
4051 (@value{GDBP}) info inferiors
4052 Id Description Executable
4058 @value{GDBN} keeps the process bound to the same inferior. The new
4059 executable image replaces the previous executable loaded in the
4060 inferior. Restarting the inferior after the @code{exec} call, with
4061 e.g., the @code{run} command, restarts the executable the process was
4062 running after the @code{exec} call. This is the default mode.
4067 (@value{GDBP}) info inferiors
4068 Id Description Executable
4071 process 12020 is executing new program: prog2
4072 Program exited normally.
4073 (@value{GDBP}) info inferiors
4074 Id Description Executable
4081 @code{follow-exec-mode} is supported in native mode and
4082 @code{target extended-remote} mode.
4084 You can use the @code{catch} command to make @value{GDBN} stop whenever
4085 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4086 Catchpoints, ,Setting Catchpoints}.
4088 @node Checkpoint/Restart
4089 @section Setting a @emph{Bookmark} to Return to Later
4094 @cindex snapshot of a process
4095 @cindex rewind program state
4097 On certain operating systems@footnote{Currently, only
4098 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4099 program's state, called a @dfn{checkpoint}, and come back to it
4102 Returning to a checkpoint effectively undoes everything that has
4103 happened in the program since the @code{checkpoint} was saved. This
4104 includes changes in memory, registers, and even (within some limits)
4105 system state. Effectively, it is like going back in time to the
4106 moment when the checkpoint was saved.
4108 Thus, if you're stepping thru a program and you think you're
4109 getting close to the point where things go wrong, you can save
4110 a checkpoint. Then, if you accidentally go too far and miss
4111 the critical statement, instead of having to restart your program
4112 from the beginning, you can just go back to the checkpoint and
4113 start again from there.
4115 This can be especially useful if it takes a lot of time or
4116 steps to reach the point where you think the bug occurs.
4118 To use the @code{checkpoint}/@code{restart} method of debugging:
4123 Save a snapshot of the debugged program's current execution state.
4124 The @code{checkpoint} command takes no arguments, but each checkpoint
4125 is assigned a small integer id, similar to a breakpoint id.
4127 @kindex info checkpoints
4128 @item info checkpoints
4129 List the checkpoints that have been saved in the current debugging
4130 session. For each checkpoint, the following information will be
4137 @item Source line, or label
4140 @kindex restart @var{checkpoint-id}
4141 @item restart @var{checkpoint-id}
4142 Restore the program state that was saved as checkpoint number
4143 @var{checkpoint-id}. All program variables, registers, stack frames
4144 etc.@: will be returned to the values that they had when the checkpoint
4145 was saved. In essence, gdb will ``wind back the clock'' to the point
4146 in time when the checkpoint was saved.
4148 Note that breakpoints, @value{GDBN} variables, command history etc.
4149 are not affected by restoring a checkpoint. In general, a checkpoint
4150 only restores things that reside in the program being debugged, not in
4153 @kindex delete checkpoint @var{checkpoint-id}
4154 @item delete checkpoint @var{checkpoint-id}
4155 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4159 Returning to a previously saved checkpoint will restore the user state
4160 of the program being debugged, plus a significant subset of the system
4161 (OS) state, including file pointers. It won't ``un-write'' data from
4162 a file, but it will rewind the file pointer to the previous location,
4163 so that the previously written data can be overwritten. For files
4164 opened in read mode, the pointer will also be restored so that the
4165 previously read data can be read again.
4167 Of course, characters that have been sent to a printer (or other
4168 external device) cannot be ``snatched back'', and characters received
4169 from eg.@: a serial device can be removed from internal program buffers,
4170 but they cannot be ``pushed back'' into the serial pipeline, ready to
4171 be received again. Similarly, the actual contents of files that have
4172 been changed cannot be restored (at this time).
4174 However, within those constraints, you actually can ``rewind'' your
4175 program to a previously saved point in time, and begin debugging it
4176 again --- and you can change the course of events so as to debug a
4177 different execution path this time.
4179 @cindex checkpoints and process id
4180 Finally, there is one bit of internal program state that will be
4181 different when you return to a checkpoint --- the program's process
4182 id. Each checkpoint will have a unique process id (or @var{pid}),
4183 and each will be different from the program's original @var{pid}.
4184 If your program has saved a local copy of its process id, this could
4185 potentially pose a problem.
4187 @subsection A Non-obvious Benefit of Using Checkpoints
4189 On some systems such as @sc{gnu}/Linux, address space randomization
4190 is performed on new processes for security reasons. This makes it
4191 difficult or impossible to set a breakpoint, or watchpoint, on an
4192 absolute address if you have to restart the program, since the
4193 absolute location of a symbol will change from one execution to the
4196 A checkpoint, however, is an @emph{identical} copy of a process.
4197 Therefore if you create a checkpoint at (eg.@:) the start of main,
4198 and simply return to that checkpoint instead of restarting the
4199 process, you can avoid the effects of address randomization and
4200 your symbols will all stay in the same place.
4203 @chapter Stopping and Continuing
4205 The principal purposes of using a debugger are so that you can stop your
4206 program before it terminates; or so that, if your program runs into
4207 trouble, you can investigate and find out why.
4209 Inside @value{GDBN}, your program may stop for any of several reasons,
4210 such as a signal, a breakpoint, or reaching a new line after a
4211 @value{GDBN} command such as @code{step}. You may then examine and
4212 change variables, set new breakpoints or remove old ones, and then
4213 continue execution. Usually, the messages shown by @value{GDBN} provide
4214 ample explanation of the status of your program---but you can also
4215 explicitly request this information at any time.
4218 @kindex info program
4220 Display information about the status of your program: whether it is
4221 running or not, what process it is, and why it stopped.
4225 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4226 * Continuing and Stepping:: Resuming execution
4227 * Skipping Over Functions and Files::
4228 Skipping over functions and files
4230 * Thread Stops:: Stopping and starting multi-thread programs
4234 @section Breakpoints, Watchpoints, and Catchpoints
4237 A @dfn{breakpoint} makes your program stop whenever a certain point in
4238 the program is reached. For each breakpoint, you can add conditions to
4239 control in finer detail whether your program stops. You can set
4240 breakpoints with the @code{break} command and its variants (@pxref{Set
4241 Breaks, ,Setting Breakpoints}), to specify the place where your program
4242 should stop by line number, function name or exact address in the
4245 On some systems, you can set breakpoints in shared libraries before
4246 the executable is run.
4249 @cindex data breakpoints
4250 @cindex memory tracing
4251 @cindex breakpoint on memory address
4252 @cindex breakpoint on variable modification
4253 A @dfn{watchpoint} is a special breakpoint that stops your program
4254 when the value of an expression changes. The expression may be a value
4255 of a variable, or it could involve values of one or more variables
4256 combined by operators, such as @samp{a + b}. This is sometimes called
4257 @dfn{data breakpoints}. You must use a different command to set
4258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4259 from that, you can manage a watchpoint like any other breakpoint: you
4260 enable, disable, and delete both breakpoints and watchpoints using the
4263 You can arrange to have values from your program displayed automatically
4264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4268 @cindex breakpoint on events
4269 A @dfn{catchpoint} is another special breakpoint that stops your program
4270 when a certain kind of event occurs, such as the throwing of a C@t{++}
4271 exception or the loading of a library. As with watchpoints, you use a
4272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4273 Catchpoints}), but aside from that, you can manage a catchpoint like any
4274 other breakpoint. (To stop when your program receives a signal, use the
4275 @code{handle} command; see @ref{Signals, ,Signals}.)
4277 @cindex breakpoint numbers
4278 @cindex numbers for breakpoints
4279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4280 catchpoint when you create it; these numbers are successive integers
4281 starting with one. In many of the commands for controlling various
4282 features of breakpoints you use the breakpoint number to say which
4283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4284 @dfn{disabled}; if disabled, it has no effect on your program until you
4287 @cindex breakpoint ranges
4288 @cindex breakpoint lists
4289 @cindex ranges of breakpoints
4290 @cindex lists of breakpoints
4291 Some @value{GDBN} commands accept a space-separated list of breakpoints
4292 on which to operate. A list element can be either a single breakpoint number,
4293 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4294 When a breakpoint list is given to a command, all breakpoints in that list
4298 * Set Breaks:: Setting breakpoints
4299 * Set Watchpoints:: Setting watchpoints
4300 * Set Catchpoints:: Setting catchpoints
4301 * Delete Breaks:: Deleting breakpoints
4302 * Disabling:: Disabling breakpoints
4303 * Conditions:: Break conditions
4304 * Break Commands:: Breakpoint command lists
4305 * Dynamic Printf:: Dynamic printf
4306 * Save Breakpoints:: How to save breakpoints in a file
4307 * Static Probe Points:: Listing static probe points
4308 * Error in Breakpoints:: ``Cannot insert breakpoints''
4309 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4313 @subsection Setting Breakpoints
4315 @c FIXME LMB what does GDB do if no code on line of breakpt?
4316 @c consider in particular declaration with/without initialization.
4318 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4321 @kindex b @r{(@code{break})}
4322 @vindex $bpnum@r{, convenience variable}
4323 @cindex latest breakpoint
4324 Breakpoints are set with the @code{break} command (abbreviated
4325 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4326 number of the breakpoint you've set most recently; see @ref{Convenience
4327 Vars,, Convenience Variables}, for a discussion of what you can do with
4328 convenience variables.
4331 @item break @var{location}
4332 Set a breakpoint at the given @var{location}, which can specify a
4333 function name, a line number, or an address of an instruction.
4334 (@xref{Specify Location}, for a list of all the possible ways to
4335 specify a @var{location}.) The breakpoint will stop your program just
4336 before it executes any of the code in the specified @var{location}.
4338 When using source languages that permit overloading of symbols, such as
4339 C@t{++}, a function name may refer to more than one possible place to break.
4340 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4343 It is also possible to insert a breakpoint that will stop the program
4344 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4345 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4348 When called without any arguments, @code{break} sets a breakpoint at
4349 the next instruction to be executed in the selected stack frame
4350 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4351 innermost, this makes your program stop as soon as control
4352 returns to that frame. This is similar to the effect of a
4353 @code{finish} command in the frame inside the selected frame---except
4354 that @code{finish} does not leave an active breakpoint. If you use
4355 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4356 the next time it reaches the current location; this may be useful
4359 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4360 least one instruction has been executed. If it did not do this, you
4361 would be unable to proceed past a breakpoint without first disabling the
4362 breakpoint. This rule applies whether or not the breakpoint already
4363 existed when your program stopped.
4365 @item break @dots{} if @var{cond}
4366 Set a breakpoint with condition @var{cond}; evaluate the expression
4367 @var{cond} each time the breakpoint is reached, and stop only if the
4368 value is nonzero---that is, if @var{cond} evaluates as true.
4369 @samp{@dots{}} stands for one of the possible arguments described
4370 above (or no argument) specifying where to break. @xref{Conditions,
4371 ,Break Conditions}, for more information on breakpoint conditions.
4373 The breakpoint may be mapped to multiple locations. If the breakpoint
4374 condition @var{cond} is invalid at some but not all of the locations,
4375 the locations for which the condition is invalid are disabled. For
4376 example, @value{GDBN} reports below that two of the three locations
4380 (@value{GDBP}) break func if a == 10
4381 warning: failed to validate condition at location 0x11ce, disabling:
4382 No symbol "a" in current context.
4383 warning: failed to validate condition at location 0x11b6, disabling:
4384 No symbol "a" in current context.
4385 Breakpoint 1 at 0x11b6: func. (3 locations)
4388 Locations that are disabled because of the condition are denoted by an
4389 uppercase @code{N} in the output of the @code{info breakpoints}
4393 (@value{GDBP}) info breakpoints
4394 Num Type Disp Enb Address What
4395 1 breakpoint keep y <MULTIPLE>
4396 stop only if a == 10
4397 1.1 N* 0x00000000000011b6 in ...
4398 1.2 y 0x00000000000011c2 in ...
4399 1.3 N* 0x00000000000011ce in ...
4400 (*): Breakpoint condition is invalid at this location.
4403 If the breakpoint condition @var{cond} is invalid in the context of
4404 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4405 define the breakpoint. For example, if variable @code{foo} is an
4409 (@value{GDBP}) break func if foo
4410 No symbol "foo" in current context.
4413 @item break @dots{} -force-condition if @var{cond}
4414 There may be cases where the condition @var{cond} is invalid at all
4415 the current locations, but the user knows that it will be valid at a
4416 future location; for example, because of a library load. In such
4417 cases, by using the @code{-force-condition} keyword before @samp{if},
4418 @value{GDBN} can be forced to define the breakpoint with the given
4419 condition expression instead of refusing it.
4422 (@value{GDBP}) break func -force-condition if foo
4423 warning: failed to validate condition at location 1, disabling:
4424 No symbol "foo" in current context.
4425 warning: failed to validate condition at location 2, disabling:
4426 No symbol "foo" in current context.
4427 warning: failed to validate condition at location 3, disabling:
4428 No symbol "foo" in current context.
4429 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4432 This causes all the present locations where the breakpoint would
4433 otherwise be inserted, to be disabled, as seen in the example above.
4434 However, if there exist locations at which the condition is valid, the
4435 @code{-force-condition} keyword has no effect.
4438 @item tbreak @var{args}
4439 Set a breakpoint enabled only for one stop. The @var{args} are the
4440 same as for the @code{break} command, and the breakpoint is set in the same
4441 way, but the breakpoint is automatically deleted after the first time your
4442 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4445 @cindex hardware breakpoints
4446 @item hbreak @var{args}
4447 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4448 @code{break} command and the breakpoint is set in the same way, but the
4449 breakpoint requires hardware support and some target hardware may not
4450 have this support. The main purpose of this is EPROM/ROM code
4451 debugging, so you can set a breakpoint at an instruction without
4452 changing the instruction. This can be used with the new trap-generation
4453 provided by SPARClite DSU and most x86-based targets. These targets
4454 will generate traps when a program accesses some data or instruction
4455 address that is assigned to the debug registers. However the hardware
4456 breakpoint registers can take a limited number of breakpoints. For
4457 example, on the DSU, only two data breakpoints can be set at a time, and
4458 @value{GDBN} will reject this command if more than two are used. Delete
4459 or disable unused hardware breakpoints before setting new ones
4460 (@pxref{Disabling, ,Disabling Breakpoints}).
4461 @xref{Conditions, ,Break Conditions}.
4462 For remote targets, you can restrict the number of hardware
4463 breakpoints @value{GDBN} will use, see @ref{set remote
4464 hardware-breakpoint-limit}.
4467 @item thbreak @var{args}
4468 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4469 are the same as for the @code{hbreak} command and the breakpoint is set in
4470 the same way. However, like the @code{tbreak} command,
4471 the breakpoint is automatically deleted after the
4472 first time your program stops there. Also, like the @code{hbreak}
4473 command, the breakpoint requires hardware support and some target hardware
4474 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4475 See also @ref{Conditions, ,Break Conditions}.
4478 @cindex regular expression
4479 @cindex breakpoints at functions matching a regexp
4480 @cindex set breakpoints in many functions
4481 @item rbreak @var{regex}
4482 Set breakpoints on all functions matching the regular expression
4483 @var{regex}. This command sets an unconditional breakpoint on all
4484 matches, printing a list of all breakpoints it set. Once these
4485 breakpoints are set, they are treated just like the breakpoints set with
4486 the @code{break} command. You can delete them, disable them, or make
4487 them conditional the same way as any other breakpoint.
4489 In programs using different languages, @value{GDBN} chooses the syntax
4490 to print the list of all breakpoints it sets according to the
4491 @samp{set language} value: using @samp{set language auto}
4492 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4493 language of the breakpoint's function, other values mean to use
4494 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4496 The syntax of the regular expression is the standard one used with tools
4497 like @file{grep}. Note that this is different from the syntax used by
4498 shells, so for instance @code{foo*} matches all functions that include
4499 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4500 @code{.*} leading and trailing the regular expression you supply, so to
4501 match only functions that begin with @code{foo}, use @code{^foo}.
4503 @cindex non-member C@t{++} functions, set breakpoint in
4504 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4505 breakpoints on overloaded functions that are not members of any special
4508 @cindex set breakpoints on all functions
4509 The @code{rbreak} command can be used to set breakpoints in
4510 @strong{all} the functions in a program, like this:
4513 (@value{GDBP}) rbreak .
4516 @item rbreak @var{file}:@var{regex}
4517 If @code{rbreak} is called with a filename qualification, it limits
4518 the search for functions matching the given regular expression to the
4519 specified @var{file}. This can be used, for example, to set breakpoints on
4520 every function in a given file:
4523 (@value{GDBP}) rbreak file.c:.
4526 The colon separating the filename qualifier from the regex may
4527 optionally be surrounded by spaces.
4529 @kindex info breakpoints
4530 @cindex @code{$_} and @code{info breakpoints}
4531 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4532 @itemx info break @r{[}@var{list}@dots{}@r{]}
4533 Print a table of all breakpoints, watchpoints, and catchpoints set and
4534 not deleted. Optional argument @var{n} means print information only
4535 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4536 For each breakpoint, following columns are printed:
4539 @item Breakpoint Numbers
4541 Breakpoint, watchpoint, or catchpoint.
4543 Whether the breakpoint is marked to be disabled or deleted when hit.
4544 @item Enabled or Disabled
4545 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4546 that are not enabled.
4548 Where the breakpoint is in your program, as a memory address. For a
4549 pending breakpoint whose address is not yet known, this field will
4550 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4551 library that has the symbol or line referred by breakpoint is loaded.
4552 See below for details. A breakpoint with several locations will
4553 have @samp{<MULTIPLE>} in this field---see below for details.
4555 Where the breakpoint is in the source for your program, as a file and
4556 line number. For a pending breakpoint, the original string passed to
4557 the breakpoint command will be listed as it cannot be resolved until
4558 the appropriate shared library is loaded in the future.
4562 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4563 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4564 @value{GDBN} on the host's side. If it is ``target'', then the condition
4565 is evaluated by the target. The @code{info break} command shows
4566 the condition on the line following the affected breakpoint, together with
4567 its condition evaluation mode in between parentheses.
4569 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4570 allowed to have a condition specified for it. The condition is not parsed for
4571 validity until a shared library is loaded that allows the pending
4572 breakpoint to resolve to a valid location.
4575 @code{info break} with a breakpoint
4576 number @var{n} as argument lists only that breakpoint. The
4577 convenience variable @code{$_} and the default examining-address for
4578 the @code{x} command are set to the address of the last breakpoint
4579 listed (@pxref{Memory, ,Examining Memory}).
4582 @code{info break} displays a count of the number of times the breakpoint
4583 has been hit. This is especially useful in conjunction with the
4584 @code{ignore} command. You can ignore a large number of breakpoint
4585 hits, look at the breakpoint info to see how many times the breakpoint
4586 was hit, and then run again, ignoring one less than that number. This
4587 will get you quickly to the last hit of that breakpoint.
4590 For a breakpoints with an enable count (xref) greater than 1,
4591 @code{info break} also displays that count.
4595 @value{GDBN} allows you to set any number of breakpoints at the same place in
4596 your program. There is nothing silly or meaningless about this. When
4597 the breakpoints are conditional, this is even useful
4598 (@pxref{Conditions, ,Break Conditions}).
4600 @cindex multiple locations, breakpoints
4601 @cindex breakpoints, multiple locations
4602 It is possible that a breakpoint corresponds to several locations
4603 in your program. Examples of this situation are:
4607 Multiple functions in the program may have the same name.
4610 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4611 instances of the function body, used in different cases.
4614 For a C@t{++} template function, a given line in the function can
4615 correspond to any number of instantiations.
4618 For an inlined function, a given source line can correspond to
4619 several places where that function is inlined.
4622 In all those cases, @value{GDBN} will insert a breakpoint at all
4623 the relevant locations.
4625 A breakpoint with multiple locations is displayed in the breakpoint
4626 table using several rows---one header row, followed by one row for
4627 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4628 address column. The rows for individual locations contain the actual
4629 addresses for locations, and show the functions to which those
4630 locations belong. The number column for a location is of the form
4631 @var{breakpoint-number}.@var{location-number}.
4636 Num Type Disp Enb Address What
4637 1 breakpoint keep y <MULTIPLE>
4639 breakpoint already hit 1 time
4640 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4641 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4644 You cannot delete the individual locations from a breakpoint. However,
4645 each location can be individually enabled or disabled by passing
4646 @var{breakpoint-number}.@var{location-number} as argument to the
4647 @code{enable} and @code{disable} commands. It's also possible to
4648 @code{enable} and @code{disable} a range of @var{location-number}
4649 locations using a @var{breakpoint-number} and two @var{location-number}s,
4650 in increasing order, separated by a hyphen, like
4651 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4652 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4653 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4654 all of the locations that belong to that breakpoint.
4656 @cindex pending breakpoints
4657 It's quite common to have a breakpoint inside a shared library.
4658 Shared libraries can be loaded and unloaded explicitly,
4659 and possibly repeatedly, as the program is executed. To support
4660 this use case, @value{GDBN} updates breakpoint locations whenever
4661 any shared library is loaded or unloaded. Typically, you would
4662 set a breakpoint in a shared library at the beginning of your
4663 debugging session, when the library is not loaded, and when the
4664 symbols from the library are not available. When you try to set
4665 breakpoint, @value{GDBN} will ask you if you want to set
4666 a so called @dfn{pending breakpoint}---breakpoint whose address
4667 is not yet resolved.
4669 After the program is run, whenever a new shared library is loaded,
4670 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4671 shared library contains the symbol or line referred to by some
4672 pending breakpoint, that breakpoint is resolved and becomes an
4673 ordinary breakpoint. When a library is unloaded, all breakpoints
4674 that refer to its symbols or source lines become pending again.
4676 This logic works for breakpoints with multiple locations, too. For
4677 example, if you have a breakpoint in a C@t{++} template function, and
4678 a newly loaded shared library has an instantiation of that template,
4679 a new location is added to the list of locations for the breakpoint.
4681 Except for having unresolved address, pending breakpoints do not
4682 differ from regular breakpoints. You can set conditions or commands,
4683 enable and disable them and perform other breakpoint operations.
4685 @value{GDBN} provides some additional commands for controlling what
4686 happens when the @samp{break} command cannot resolve breakpoint
4687 address specification to an address:
4689 @kindex set breakpoint pending
4690 @kindex show breakpoint pending
4692 @item set breakpoint pending auto
4693 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4694 location, it queries you whether a pending breakpoint should be created.
4696 @item set breakpoint pending on
4697 This indicates that an unrecognized breakpoint location should automatically
4698 result in a pending breakpoint being created.
4700 @item set breakpoint pending off
4701 This indicates that pending breakpoints are not to be created. Any
4702 unrecognized breakpoint location results in an error. This setting does
4703 not affect any pending breakpoints previously created.
4705 @item show breakpoint pending
4706 Show the current behavior setting for creating pending breakpoints.
4709 The settings above only affect the @code{break} command and its
4710 variants. Once breakpoint is set, it will be automatically updated
4711 as shared libraries are loaded and unloaded.
4713 @cindex automatic hardware breakpoints
4714 For some targets, @value{GDBN} can automatically decide if hardware or
4715 software breakpoints should be used, depending on whether the
4716 breakpoint address is read-only or read-write. This applies to
4717 breakpoints set with the @code{break} command as well as to internal
4718 breakpoints set by commands like @code{next} and @code{finish}. For
4719 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4722 You can control this automatic behaviour with the following commands:
4724 @kindex set breakpoint auto-hw
4725 @kindex show breakpoint auto-hw
4727 @item set breakpoint auto-hw on
4728 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4729 will try to use the target memory map to decide if software or hardware
4730 breakpoint must be used.
4732 @item set breakpoint auto-hw off
4733 This indicates @value{GDBN} should not automatically select breakpoint
4734 type. If the target provides a memory map, @value{GDBN} will warn when
4735 trying to set software breakpoint at a read-only address.
4738 @value{GDBN} normally implements breakpoints by replacing the program code
4739 at the breakpoint address with a special instruction, which, when
4740 executed, given control to the debugger. By default, the program
4741 code is so modified only when the program is resumed. As soon as
4742 the program stops, @value{GDBN} restores the original instructions. This
4743 behaviour guards against leaving breakpoints inserted in the
4744 target should gdb abrubptly disconnect. However, with slow remote
4745 targets, inserting and removing breakpoint can reduce the performance.
4746 This behavior can be controlled with the following commands::
4748 @kindex set breakpoint always-inserted
4749 @kindex show breakpoint always-inserted
4751 @item set breakpoint always-inserted off
4752 All breakpoints, including newly added by the user, are inserted in
4753 the target only when the target is resumed. All breakpoints are
4754 removed from the target when it stops. This is the default mode.
4756 @item set breakpoint always-inserted on
4757 Causes all breakpoints to be inserted in the target at all times. If
4758 the user adds a new breakpoint, or changes an existing breakpoint, the
4759 breakpoints in the target are updated immediately. A breakpoint is
4760 removed from the target only when breakpoint itself is deleted.
4763 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4764 when a breakpoint breaks. If the condition is true, then the process being
4765 debugged stops, otherwise the process is resumed.
4767 If the target supports evaluating conditions on its end, @value{GDBN} may
4768 download the breakpoint, together with its conditions, to it.
4770 This feature can be controlled via the following commands:
4772 @kindex set breakpoint condition-evaluation
4773 @kindex show breakpoint condition-evaluation
4775 @item set breakpoint condition-evaluation host
4776 This option commands @value{GDBN} to evaluate the breakpoint
4777 conditions on the host's side. Unconditional breakpoints are sent to
4778 the target which in turn receives the triggers and reports them back to GDB
4779 for condition evaluation. This is the standard evaluation mode.
4781 @item set breakpoint condition-evaluation target
4782 This option commands @value{GDBN} to download breakpoint conditions
4783 to the target at the moment of their insertion. The target
4784 is responsible for evaluating the conditional expression and reporting
4785 breakpoint stop events back to @value{GDBN} whenever the condition
4786 is true. Due to limitations of target-side evaluation, some conditions
4787 cannot be evaluated there, e.g., conditions that depend on local data
4788 that is only known to the host. Examples include
4789 conditional expressions involving convenience variables, complex types
4790 that cannot be handled by the agent expression parser and expressions
4791 that are too long to be sent over to the target, specially when the
4792 target is a remote system. In these cases, the conditions will be
4793 evaluated by @value{GDBN}.
4795 @item set breakpoint condition-evaluation auto
4796 This is the default mode. If the target supports evaluating breakpoint
4797 conditions on its end, @value{GDBN} will download breakpoint conditions to
4798 the target (limitations mentioned previously apply). If the target does
4799 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4800 to evaluating all these conditions on the host's side.
4804 @cindex negative breakpoint numbers
4805 @cindex internal @value{GDBN} breakpoints
4806 @value{GDBN} itself sometimes sets breakpoints in your program for
4807 special purposes, such as proper handling of @code{longjmp} (in C
4808 programs). These internal breakpoints are assigned negative numbers,
4809 starting with @code{-1}; @samp{info breakpoints} does not display them.
4810 You can see these breakpoints with the @value{GDBN} maintenance command
4811 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4814 @node Set Watchpoints
4815 @subsection Setting Watchpoints
4817 @cindex setting watchpoints
4818 You can use a watchpoint to stop execution whenever the value of an
4819 expression changes, without having to predict a particular place where
4820 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4821 The expression may be as simple as the value of a single variable, or
4822 as complex as many variables combined by operators. Examples include:
4826 A reference to the value of a single variable.
4829 An address cast to an appropriate data type. For example,
4830 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4831 address (assuming an @code{int} occupies 4 bytes).
4834 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4835 expression can use any operators valid in the program's native
4836 language (@pxref{Languages}).
4839 You can set a watchpoint on an expression even if the expression can
4840 not be evaluated yet. For instance, you can set a watchpoint on
4841 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4842 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4843 the expression produces a valid value. If the expression becomes
4844 valid in some other way than changing a variable (e.g.@: if the memory
4845 pointed to by @samp{*global_ptr} becomes readable as the result of a
4846 @code{malloc} call), @value{GDBN} may not stop until the next time
4847 the expression changes.
4849 @cindex software watchpoints
4850 @cindex hardware watchpoints
4851 Depending on your system, watchpoints may be implemented in software or
4852 hardware. @value{GDBN} does software watchpointing by single-stepping your
4853 program and testing the variable's value each time, which is hundreds of
4854 times slower than normal execution. (But this may still be worth it, to
4855 catch errors where you have no clue what part of your program is the
4858 On some systems, such as most PowerPC or x86-based targets,
4859 @value{GDBN} includes support for hardware watchpoints, which do not
4860 slow down the running of your program.
4864 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4865 Set a watchpoint for an expression. @value{GDBN} will break when the
4866 expression @var{expr} is written into by the program and its value
4867 changes. The simplest (and the most popular) use of this command is
4868 to watch the value of a single variable:
4871 (@value{GDBP}) watch foo
4874 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4875 argument, @value{GDBN} breaks only when the thread identified by
4876 @var{thread-id} changes the value of @var{expr}. If any other threads
4877 change the value of @var{expr}, @value{GDBN} will not break. Note
4878 that watchpoints restricted to a single thread in this way only work
4879 with Hardware Watchpoints.
4881 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4882 (see below). The @code{-location} argument tells @value{GDBN} to
4883 instead watch the memory referred to by @var{expr}. In this case,
4884 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4885 and watch the memory at that address. The type of the result is used
4886 to determine the size of the watched memory. If the expression's
4887 result does not have an address, then @value{GDBN} will print an
4890 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4891 of masked watchpoints, if the current architecture supports this
4892 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4893 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4894 to an address to watch. The mask specifies that some bits of an address
4895 (the bits which are reset in the mask) should be ignored when matching
4896 the address accessed by the inferior against the watchpoint address.
4897 Thus, a masked watchpoint watches many addresses simultaneously---those
4898 addresses whose unmasked bits are identical to the unmasked bits in the
4899 watchpoint address. The @code{mask} argument implies @code{-location}.
4903 (@value{GDBP}) watch foo mask 0xffff00ff
4904 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4908 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4909 Set a watchpoint that will break when the value of @var{expr} is read
4913 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4914 Set a watchpoint that will break when @var{expr} is either read from
4915 or written into by the program.
4917 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4918 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4919 This command prints a list of watchpoints, using the same format as
4920 @code{info break} (@pxref{Set Breaks}).
4923 If you watch for a change in a numerically entered address you need to
4924 dereference it, as the address itself is just a constant number which will
4925 never change. @value{GDBN} refuses to create a watchpoint that watches
4926 a never-changing value:
4929 (@value{GDBP}) watch 0x600850
4930 Cannot watch constant value 0x600850.
4931 (@value{GDBP}) watch *(int *) 0x600850
4932 Watchpoint 1: *(int *) 6293584
4935 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4936 watchpoints execute very quickly, and the debugger reports a change in
4937 value at the exact instruction where the change occurs. If @value{GDBN}
4938 cannot set a hardware watchpoint, it sets a software watchpoint, which
4939 executes more slowly and reports the change in value at the next
4940 @emph{statement}, not the instruction, after the change occurs.
4942 @cindex use only software watchpoints
4943 You can force @value{GDBN} to use only software watchpoints with the
4944 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4945 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4946 the underlying system supports them. (Note that hardware-assisted
4947 watchpoints that were set @emph{before} setting
4948 @code{can-use-hw-watchpoints} to zero will still use the hardware
4949 mechanism of watching expression values.)
4952 @item set can-use-hw-watchpoints
4953 @kindex set can-use-hw-watchpoints
4954 Set whether or not to use hardware watchpoints.
4956 @item show can-use-hw-watchpoints
4957 @kindex show can-use-hw-watchpoints
4958 Show the current mode of using hardware watchpoints.
4961 For remote targets, you can restrict the number of hardware
4962 watchpoints @value{GDBN} will use, see @ref{set remote
4963 hardware-breakpoint-limit}.
4965 When you issue the @code{watch} command, @value{GDBN} reports
4968 Hardware watchpoint @var{num}: @var{expr}
4972 if it was able to set a hardware watchpoint.
4974 Currently, the @code{awatch} and @code{rwatch} commands can only set
4975 hardware watchpoints, because accesses to data that don't change the
4976 value of the watched expression cannot be detected without examining
4977 every instruction as it is being executed, and @value{GDBN} does not do
4978 that currently. If @value{GDBN} finds that it is unable to set a
4979 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4980 will print a message like this:
4983 Expression cannot be implemented with read/access watchpoint.
4986 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4987 data type of the watched expression is wider than what a hardware
4988 watchpoint on the target machine can handle. For example, some systems
4989 can only watch regions that are up to 4 bytes wide; on such systems you
4990 cannot set hardware watchpoints for an expression that yields a
4991 double-precision floating-point number (which is typically 8 bytes
4992 wide). As a work-around, it might be possible to break the large region
4993 into a series of smaller ones and watch them with separate watchpoints.
4995 If you set too many hardware watchpoints, @value{GDBN} might be unable
4996 to insert all of them when you resume the execution of your program.
4997 Since the precise number of active watchpoints is unknown until such
4998 time as the program is about to be resumed, @value{GDBN} might not be
4999 able to warn you about this when you set the watchpoints, and the
5000 warning will be printed only when the program is resumed:
5003 Hardware watchpoint @var{num}: Could not insert watchpoint
5007 If this happens, delete or disable some of the watchpoints.
5009 Watching complex expressions that reference many variables can also
5010 exhaust the resources available for hardware-assisted watchpoints.
5011 That's because @value{GDBN} needs to watch every variable in the
5012 expression with separately allocated resources.
5014 If you call a function interactively using @code{print} or @code{call},
5015 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5016 kind of breakpoint or the call completes.
5018 @value{GDBN} automatically deletes watchpoints that watch local
5019 (automatic) variables, or expressions that involve such variables, when
5020 they go out of scope, that is, when the execution leaves the block in
5021 which these variables were defined. In particular, when the program
5022 being debugged terminates, @emph{all} local variables go out of scope,
5023 and so only watchpoints that watch global variables remain set. If you
5024 rerun the program, you will need to set all such watchpoints again. One
5025 way of doing that would be to set a code breakpoint at the entry to the
5026 @code{main} function and when it breaks, set all the watchpoints.
5028 @cindex watchpoints and threads
5029 @cindex threads and watchpoints
5030 In multi-threaded programs, watchpoints will detect changes to the
5031 watched expression from every thread.
5034 @emph{Warning:} In multi-threaded programs, software watchpoints
5035 have only limited usefulness. If @value{GDBN} creates a software
5036 watchpoint, it can only watch the value of an expression @emph{in a
5037 single thread}. If you are confident that the expression can only
5038 change due to the current thread's activity (and if you are also
5039 confident that no other thread can become current), then you can use
5040 software watchpoints as usual. However, @value{GDBN} may not notice
5041 when a non-current thread's activity changes the expression. (Hardware
5042 watchpoints, in contrast, watch an expression in all threads.)
5045 @xref{set remote hardware-watchpoint-limit}.
5047 @node Set Catchpoints
5048 @subsection Setting Catchpoints
5049 @cindex catchpoints, setting
5050 @cindex exception handlers
5051 @cindex event handling
5053 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5054 kinds of program events, such as C@t{++} exceptions or the loading of a
5055 shared library. Use the @code{catch} command to set a catchpoint.
5059 @item catch @var{event}
5060 Stop when @var{event} occurs. The @var{event} can be any of the following:
5063 @item throw @r{[}@var{regexp}@r{]}
5064 @itemx rethrow @r{[}@var{regexp}@r{]}
5065 @itemx catch @r{[}@var{regexp}@r{]}
5067 @kindex catch rethrow
5069 @cindex stop on C@t{++} exceptions
5070 The throwing, re-throwing, or catching of a C@t{++} exception.
5072 If @var{regexp} is given, then only exceptions whose type matches the
5073 regular expression will be caught.
5075 @vindex $_exception@r{, convenience variable}
5076 The convenience variable @code{$_exception} is available at an
5077 exception-related catchpoint, on some systems. This holds the
5078 exception being thrown.
5080 There are currently some limitations to C@t{++} exception handling in
5085 The support for these commands is system-dependent. Currently, only
5086 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5090 The regular expression feature and the @code{$_exception} convenience
5091 variable rely on the presence of some SDT probes in @code{libstdc++}.
5092 If these probes are not present, then these features cannot be used.
5093 These probes were first available in the GCC 4.8 release, but whether
5094 or not they are available in your GCC also depends on how it was
5098 The @code{$_exception} convenience variable is only valid at the
5099 instruction at which an exception-related catchpoint is set.
5102 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5103 location in the system library which implements runtime exception
5104 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5105 (@pxref{Selection}) to get to your code.
5108 If you call a function interactively, @value{GDBN} normally returns
5109 control to you when the function has finished executing. If the call
5110 raises an exception, however, the call may bypass the mechanism that
5111 returns control to you and cause your program either to abort or to
5112 simply continue running until it hits a breakpoint, catches a signal
5113 that @value{GDBN} is listening for, or exits. This is the case even if
5114 you set a catchpoint for the exception; catchpoints on exceptions are
5115 disabled within interactive calls. @xref{Calling}, for information on
5116 controlling this with @code{set unwind-on-terminating-exception}.
5119 You cannot raise an exception interactively.
5122 You cannot install an exception handler interactively.
5125 @item exception @r{[}@var{name}@r{]}
5126 @kindex catch exception
5127 @cindex Ada exception catching
5128 @cindex catch Ada exceptions
5129 An Ada exception being raised. If an exception name is specified
5130 at the end of the command (eg @code{catch exception Program_Error}),
5131 the debugger will stop only when this specific exception is raised.
5132 Otherwise, the debugger stops execution when any Ada exception is raised.
5134 When inserting an exception catchpoint on a user-defined exception whose
5135 name is identical to one of the exceptions defined by the language, the
5136 fully qualified name must be used as the exception name. Otherwise,
5137 @value{GDBN} will assume that it should stop on the pre-defined exception
5138 rather than the user-defined one. For instance, assuming an exception
5139 called @code{Constraint_Error} is defined in package @code{Pck}, then
5140 the command to use to catch such exceptions is @kbd{catch exception
5141 Pck.Constraint_Error}.
5143 @vindex $_ada_exception@r{, convenience variable}
5144 The convenience variable @code{$_ada_exception} holds the address of
5145 the exception being thrown. This can be useful when setting a
5146 condition for such a catchpoint.
5148 @item exception unhandled
5149 @kindex catch exception unhandled
5150 An exception that was raised but is not handled by the program. The
5151 convenience variable @code{$_ada_exception} is set as for @code{catch
5154 @item handlers @r{[}@var{name}@r{]}
5155 @kindex catch handlers
5156 @cindex Ada exception handlers catching
5157 @cindex catch Ada exceptions when handled
5158 An Ada exception being handled. If an exception name is
5159 specified at the end of the command
5160 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5161 only when this specific exception is handled.
5162 Otherwise, the debugger stops execution when any Ada exception is handled.
5164 When inserting a handlers catchpoint on a user-defined
5165 exception whose name is identical to one of the exceptions
5166 defined by the language, the fully qualified name must be used
5167 as the exception name. Otherwise, @value{GDBN} will assume that it
5168 should stop on the pre-defined exception rather than the
5169 user-defined one. For instance, assuming an exception called
5170 @code{Constraint_Error} is defined in package @code{Pck}, then the
5171 command to use to catch such exceptions handling is
5172 @kbd{catch handlers Pck.Constraint_Error}.
5174 The convenience variable @code{$_ada_exception} is set as for
5175 @code{catch exception}.
5178 @kindex catch assert
5179 A failed Ada assertion. Note that the convenience variable
5180 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5184 @cindex break on fork/exec
5185 A call to @code{exec}.
5187 @anchor{catch syscall}
5189 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5190 @kindex catch syscall
5191 @cindex break on a system call.
5192 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5193 syscall is a mechanism for application programs to request a service
5194 from the operating system (OS) or one of the OS system services.
5195 @value{GDBN} can catch some or all of the syscalls issued by the
5196 debuggee, and show the related information for each syscall. If no
5197 argument is specified, calls to and returns from all system calls
5200 @var{name} can be any system call name that is valid for the
5201 underlying OS. Just what syscalls are valid depends on the OS. On
5202 GNU and Unix systems, you can find the full list of valid syscall
5203 names on @file{/usr/include/asm/unistd.h}.
5205 @c For MS-Windows, the syscall names and the corresponding numbers
5206 @c can be found, e.g., on this URL:
5207 @c http://www.metasploit.com/users/opcode/syscalls.html
5208 @c but we don't support Windows syscalls yet.
5210 Normally, @value{GDBN} knows in advance which syscalls are valid for
5211 each OS, so you can use the @value{GDBN} command-line completion
5212 facilities (@pxref{Completion,, command completion}) to list the
5215 You may also specify the system call numerically. A syscall's
5216 number is the value passed to the OS's syscall dispatcher to
5217 identify the requested service. When you specify the syscall by its
5218 name, @value{GDBN} uses its database of syscalls to convert the name
5219 into the corresponding numeric code, but using the number directly
5220 may be useful if @value{GDBN}'s database does not have the complete
5221 list of syscalls on your system (e.g., because @value{GDBN} lags
5222 behind the OS upgrades).
5224 You may specify a group of related syscalls to be caught at once using
5225 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5226 instance, on some platforms @value{GDBN} allows you to catch all
5227 network related syscalls, by passing the argument @code{group:network}
5228 to @code{catch syscall}. Note that not all syscall groups are
5229 available in every system. You can use the command completion
5230 facilities (@pxref{Completion,, command completion}) to list the
5231 syscall groups available on your environment.
5233 The example below illustrates how this command works if you don't provide
5237 (@value{GDBP}) catch syscall
5238 Catchpoint 1 (syscall)
5240 Starting program: /tmp/catch-syscall
5242 Catchpoint 1 (call to syscall 'close'), \
5243 0xffffe424 in __kernel_vsyscall ()
5247 Catchpoint 1 (returned from syscall 'close'), \
5248 0xffffe424 in __kernel_vsyscall ()
5252 Here is an example of catching a system call by name:
5255 (@value{GDBP}) catch syscall chroot
5256 Catchpoint 1 (syscall 'chroot' [61])
5258 Starting program: /tmp/catch-syscall
5260 Catchpoint 1 (call to syscall 'chroot'), \
5261 0xffffe424 in __kernel_vsyscall ()
5265 Catchpoint 1 (returned from syscall 'chroot'), \
5266 0xffffe424 in __kernel_vsyscall ()
5270 An example of specifying a system call numerically. In the case
5271 below, the syscall number has a corresponding entry in the XML
5272 file, so @value{GDBN} finds its name and prints it:
5275 (@value{GDBP}) catch syscall 252
5276 Catchpoint 1 (syscall(s) 'exit_group')
5278 Starting program: /tmp/catch-syscall
5280 Catchpoint 1 (call to syscall 'exit_group'), \
5281 0xffffe424 in __kernel_vsyscall ()
5285 Program exited normally.
5289 Here is an example of catching a syscall group:
5292 (@value{GDBP}) catch syscall group:process
5293 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5294 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5295 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5297 Starting program: /tmp/catch-syscall
5299 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5300 from /lib64/ld-linux-x86-64.so.2
5306 However, there can be situations when there is no corresponding name
5307 in XML file for that syscall number. In this case, @value{GDBN} prints
5308 a warning message saying that it was not able to find the syscall name,
5309 but the catchpoint will be set anyway. See the example below:
5312 (@value{GDBP}) catch syscall 764
5313 warning: The number '764' does not represent a known syscall.
5314 Catchpoint 2 (syscall 764)
5318 If you configure @value{GDBN} using the @samp{--without-expat} option,
5319 it will not be able to display syscall names. Also, if your
5320 architecture does not have an XML file describing its system calls,
5321 you will not be able to see the syscall names. It is important to
5322 notice that these two features are used for accessing the syscall
5323 name database. In either case, you will see a warning like this:
5326 (@value{GDBP}) catch syscall
5327 warning: Could not open "syscalls/i386-linux.xml"
5328 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5329 GDB will not be able to display syscall names.
5330 Catchpoint 1 (syscall)
5334 Of course, the file name will change depending on your architecture and system.
5336 Still using the example above, you can also try to catch a syscall by its
5337 number. In this case, you would see something like:
5340 (@value{GDBP}) catch syscall 252
5341 Catchpoint 1 (syscall(s) 252)
5344 Again, in this case @value{GDBN} would not be able to display syscall's names.
5348 A call to @code{fork}.
5352 A call to @code{vfork}.
5354 @item load @r{[}@var{regexp}@r{]}
5355 @itemx unload @r{[}@var{regexp}@r{]}
5357 @kindex catch unload
5358 The loading or unloading of a shared library. If @var{regexp} is
5359 given, then the catchpoint will stop only if the regular expression
5360 matches one of the affected libraries.
5362 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5363 @kindex catch signal
5364 The delivery of a signal.
5366 With no arguments, this catchpoint will catch any signal that is not
5367 used internally by @value{GDBN}, specifically, all signals except
5368 @samp{SIGTRAP} and @samp{SIGINT}.
5370 With the argument @samp{all}, all signals, including those used by
5371 @value{GDBN}, will be caught. This argument cannot be used with other
5374 Otherwise, the arguments are a list of signal names as given to
5375 @code{handle} (@pxref{Signals}). Only signals specified in this list
5378 One reason that @code{catch signal} can be more useful than
5379 @code{handle} is that you can attach commands and conditions to the
5382 When a signal is caught by a catchpoint, the signal's @code{stop} and
5383 @code{print} settings, as specified by @code{handle}, are ignored.
5384 However, whether the signal is still delivered to the inferior depends
5385 on the @code{pass} setting; this can be changed in the catchpoint's
5390 @item tcatch @var{event}
5392 Set a catchpoint that is enabled only for one stop. The catchpoint is
5393 automatically deleted after the first time the event is caught.
5397 Use the @code{info break} command to list the current catchpoints.
5401 @subsection Deleting Breakpoints
5403 @cindex clearing breakpoints, watchpoints, catchpoints
5404 @cindex deleting breakpoints, watchpoints, catchpoints
5405 It is often necessary to eliminate a breakpoint, watchpoint, or
5406 catchpoint once it has done its job and you no longer want your program
5407 to stop there. This is called @dfn{deleting} the breakpoint. A
5408 breakpoint that has been deleted no longer exists; it is forgotten.
5410 With the @code{clear} command you can delete breakpoints according to
5411 where they are in your program. With the @code{delete} command you can
5412 delete individual breakpoints, watchpoints, or catchpoints by specifying
5413 their breakpoint numbers.
5415 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5416 automatically ignores breakpoints on the first instruction to be executed
5417 when you continue execution without changing the execution address.
5422 Delete any breakpoints at the next instruction to be executed in the
5423 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5424 the innermost frame is selected, this is a good way to delete a
5425 breakpoint where your program just stopped.
5427 @item clear @var{location}
5428 Delete any breakpoints set at the specified @var{location}.
5429 @xref{Specify Location}, for the various forms of @var{location}; the
5430 most useful ones are listed below:
5433 @item clear @var{function}
5434 @itemx clear @var{filename}:@var{function}
5435 Delete any breakpoints set at entry to the named @var{function}.
5437 @item clear @var{linenum}
5438 @itemx clear @var{filename}:@var{linenum}
5439 Delete any breakpoints set at or within the code of the specified
5440 @var{linenum} of the specified @var{filename}.
5443 @cindex delete breakpoints
5445 @kindex d @r{(@code{delete})}
5446 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5447 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5448 list specified as argument. If no argument is specified, delete all
5449 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5450 confirm off}). You can abbreviate this command as @code{d}.
5454 @subsection Disabling Breakpoints
5456 @cindex enable/disable a breakpoint
5457 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5458 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5459 it had been deleted, but remembers the information on the breakpoint so
5460 that you can @dfn{enable} it again later.
5462 You disable and enable breakpoints, watchpoints, and catchpoints with
5463 the @code{enable} and @code{disable} commands, optionally specifying
5464 one or more breakpoint numbers as arguments. Use @code{info break} to
5465 print a list of all breakpoints, watchpoints, and catchpoints if you
5466 do not know which numbers to use.
5468 Disabling and enabling a breakpoint that has multiple locations
5469 affects all of its locations.
5471 A breakpoint, watchpoint, or catchpoint can have any of several
5472 different states of enablement:
5476 Enabled. The breakpoint stops your program. A breakpoint set
5477 with the @code{break} command starts out in this state.
5479 Disabled. The breakpoint has no effect on your program.
5481 Enabled once. The breakpoint stops your program, but then becomes
5484 Enabled for a count. The breakpoint stops your program for the next
5485 N times, then becomes disabled.
5487 Enabled for deletion. The breakpoint stops your program, but
5488 immediately after it does so it is deleted permanently. A breakpoint
5489 set with the @code{tbreak} command starts out in this state.
5492 You can use the following commands to enable or disable breakpoints,
5493 watchpoints, and catchpoints:
5497 @kindex dis @r{(@code{disable})}
5498 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5499 Disable the specified breakpoints---or all breakpoints, if none are
5500 listed. A disabled breakpoint has no effect but is not forgotten. All
5501 options such as ignore-counts, conditions and commands are remembered in
5502 case the breakpoint is enabled again later. You may abbreviate
5503 @code{disable} as @code{dis}.
5506 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5507 Enable the specified breakpoints (or all defined breakpoints). They
5508 become effective once again in stopping your program.
5510 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5511 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5512 of these breakpoints immediately after stopping your program.
5514 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5515 Enable the specified breakpoints temporarily. @value{GDBN} records
5516 @var{count} with each of the specified breakpoints, and decrements a
5517 breakpoint's count when it is hit. When any count reaches 0,
5518 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5519 count (@pxref{Conditions, ,Break Conditions}), that will be
5520 decremented to 0 before @var{count} is affected.
5522 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5523 Enable the specified breakpoints to work once, then die. @value{GDBN}
5524 deletes any of these breakpoints as soon as your program stops there.
5525 Breakpoints set by the @code{tbreak} command start out in this state.
5528 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5529 @c confusing: tbreak is also initially enabled.
5530 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5531 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5532 subsequently, they become disabled or enabled only when you use one of
5533 the commands above. (The command @code{until} can set and delete a
5534 breakpoint of its own, but it does not change the state of your other
5535 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5539 @subsection Break Conditions
5540 @cindex conditional breakpoints
5541 @cindex breakpoint conditions
5543 @c FIXME what is scope of break condition expr? Context where wanted?
5544 @c in particular for a watchpoint?
5545 The simplest sort of breakpoint breaks every time your program reaches a
5546 specified place. You can also specify a @dfn{condition} for a
5547 breakpoint. A condition is just a Boolean expression in your
5548 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5549 a condition evaluates the expression each time your program reaches it,
5550 and your program stops only if the condition is @emph{true}.
5552 This is the converse of using assertions for program validation; in that
5553 situation, you want to stop when the assertion is violated---that is,
5554 when the condition is false. In C, if you want to test an assertion expressed
5555 by the condition @var{assert}, you should set the condition
5556 @samp{! @var{assert}} on the appropriate breakpoint.
5558 Conditions are also accepted for watchpoints; you may not need them,
5559 since a watchpoint is inspecting the value of an expression anyhow---but
5560 it might be simpler, say, to just set a watchpoint on a variable name,
5561 and specify a condition that tests whether the new value is an interesting
5564 Break conditions can have side effects, and may even call functions in
5565 your program. This can be useful, for example, to activate functions
5566 that log program progress, or to use your own print functions to
5567 format special data structures. The effects are completely predictable
5568 unless there is another enabled breakpoint at the same address. (In
5569 that case, @value{GDBN} might see the other breakpoint first and stop your
5570 program without checking the condition of this one.) Note that
5571 breakpoint commands are usually more convenient and flexible than break
5573 purpose of performing side effects when a breakpoint is reached
5574 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5576 Breakpoint conditions can also be evaluated on the target's side if
5577 the target supports it. Instead of evaluating the conditions locally,
5578 @value{GDBN} encodes the expression into an agent expression
5579 (@pxref{Agent Expressions}) suitable for execution on the target,
5580 independently of @value{GDBN}. Global variables become raw memory
5581 locations, locals become stack accesses, and so forth.
5583 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5584 when its condition evaluates to true. This mechanism may provide faster
5585 response times depending on the performance characteristics of the target
5586 since it does not need to keep @value{GDBN} informed about
5587 every breakpoint trigger, even those with false conditions.
5589 Break conditions can be specified when a breakpoint is set, by using
5590 @samp{if} in the arguments to the @code{break} command. @xref{Set
5591 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5592 with the @code{condition} command.
5594 You can also use the @code{if} keyword with the @code{watch} command.
5595 The @code{catch} command does not recognize the @code{if} keyword;
5596 @code{condition} is the only way to impose a further condition on a
5601 @item condition @var{bnum} @var{expression}
5602 Specify @var{expression} as the break condition for breakpoint,
5603 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5604 breakpoint @var{bnum} stops your program only if the value of
5605 @var{expression} is true (nonzero, in C). When you use
5606 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5607 syntactic correctness, and to determine whether symbols in it have
5608 referents in the context of your breakpoint. If @var{expression} uses
5609 symbols not referenced in the context of the breakpoint, @value{GDBN}
5610 prints an error message:
5613 No symbol "foo" in current context.
5618 not actually evaluate @var{expression} at the time the @code{condition}
5619 command (or a command that sets a breakpoint with a condition, like
5620 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5622 @item condition -force @var{bnum} @var{expression}
5623 When the @code{-force} flag is used, define the condition even if
5624 @var{expression} is invalid at all the current locations of breakpoint
5625 @var{bnum}. This is similar to the @code{-force-condition} option
5626 of the @code{break} command.
5628 @item condition @var{bnum}
5629 Remove the condition from breakpoint number @var{bnum}. It becomes
5630 an ordinary unconditional breakpoint.
5633 @cindex ignore count (of breakpoint)
5634 A special case of a breakpoint condition is to stop only when the
5635 breakpoint has been reached a certain number of times. This is so
5636 useful that there is a special way to do it, using the @dfn{ignore
5637 count} of the breakpoint. Every breakpoint has an ignore count, which
5638 is an integer. Most of the time, the ignore count is zero, and
5639 therefore has no effect. But if your program reaches a breakpoint whose
5640 ignore count is positive, then instead of stopping, it just decrements
5641 the ignore count by one and continues. As a result, if the ignore count
5642 value is @var{n}, the breakpoint does not stop the next @var{n} times
5643 your program reaches it.
5647 @item ignore @var{bnum} @var{count}
5648 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5649 The next @var{count} times the breakpoint is reached, your program's
5650 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5653 To make the breakpoint stop the next time it is reached, specify
5656 When you use @code{continue} to resume execution of your program from a
5657 breakpoint, you can specify an ignore count directly as an argument to
5658 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5659 Stepping,,Continuing and Stepping}.
5661 If a breakpoint has a positive ignore count and a condition, the
5662 condition is not checked. Once the ignore count reaches zero,
5663 @value{GDBN} resumes checking the condition.
5665 You could achieve the effect of the ignore count with a condition such
5666 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5667 is decremented each time. @xref{Convenience Vars, ,Convenience
5671 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5674 @node Break Commands
5675 @subsection Breakpoint Command Lists
5677 @cindex breakpoint commands
5678 You can give any breakpoint (or watchpoint or catchpoint) a series of
5679 commands to execute when your program stops due to that breakpoint. For
5680 example, you might want to print the values of certain expressions, or
5681 enable other breakpoints.
5685 @kindex end@r{ (breakpoint commands)}
5686 @item commands @r{[}@var{list}@dots{}@r{]}
5687 @itemx @dots{} @var{command-list} @dots{}
5689 Specify a list of commands for the given breakpoints. The commands
5690 themselves appear on the following lines. Type a line containing just
5691 @code{end} to terminate the commands.
5693 To remove all commands from a breakpoint, type @code{commands} and
5694 follow it immediately with @code{end}; that is, give no commands.
5696 With no argument, @code{commands} refers to the last breakpoint,
5697 watchpoint, or catchpoint set (not to the breakpoint most recently
5698 encountered). If the most recent breakpoints were set with a single
5699 command, then the @code{commands} will apply to all the breakpoints
5700 set by that command. This applies to breakpoints set by
5701 @code{rbreak}, and also applies when a single @code{break} command
5702 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5706 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5707 disabled within a @var{command-list}.
5709 You can use breakpoint commands to start your program up again. Simply
5710 use the @code{continue} command, or @code{step}, or any other command
5711 that resumes execution.
5713 Any other commands in the command list, after a command that resumes
5714 execution, are ignored. This is because any time you resume execution
5715 (even with a simple @code{next} or @code{step}), you may encounter
5716 another breakpoint---which could have its own command list, leading to
5717 ambiguities about which list to execute.
5720 If the first command you specify in a command list is @code{silent}, the
5721 usual message about stopping at a breakpoint is not printed. This may
5722 be desirable for breakpoints that are to print a specific message and
5723 then continue. If none of the remaining commands print anything, you
5724 see no sign that the breakpoint was reached. @code{silent} is
5725 meaningful only at the beginning of a breakpoint command list.
5727 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5728 print precisely controlled output, and are often useful in silent
5729 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5731 For example, here is how you could use breakpoint commands to print the
5732 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5738 printf "x is %d\n",x
5743 One application for breakpoint commands is to compensate for one bug so
5744 you can test for another. Put a breakpoint just after the erroneous line
5745 of code, give it a condition to detect the case in which something
5746 erroneous has been done, and give it commands to assign correct values
5747 to any variables that need them. End with the @code{continue} command
5748 so that your program does not stop, and start with the @code{silent}
5749 command so that no output is produced. Here is an example:
5760 @node Dynamic Printf
5761 @subsection Dynamic Printf
5763 @cindex dynamic printf
5765 The dynamic printf command @code{dprintf} combines a breakpoint with
5766 formatted printing of your program's data to give you the effect of
5767 inserting @code{printf} calls into your program on-the-fly, without
5768 having to recompile it.
5770 In its most basic form, the output goes to the GDB console. However,
5771 you can set the variable @code{dprintf-style} for alternate handling.
5772 For instance, you can ask to format the output by calling your
5773 program's @code{printf} function. This has the advantage that the
5774 characters go to the program's output device, so they can recorded in
5775 redirects to files and so forth.
5777 If you are doing remote debugging with a stub or agent, you can also
5778 ask to have the printf handled by the remote agent. In addition to
5779 ensuring that the output goes to the remote program's device along
5780 with any other output the program might produce, you can also ask that
5781 the dprintf remain active even after disconnecting from the remote
5782 target. Using the stub/agent is also more efficient, as it can do
5783 everything without needing to communicate with @value{GDBN}.
5787 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5788 Whenever execution reaches @var{location}, print the values of one or
5789 more @var{expressions} under the control of the string @var{template}.
5790 To print several values, separate them with commas.
5792 @item set dprintf-style @var{style}
5793 Set the dprintf output to be handled in one of several different
5794 styles enumerated below. A change of style affects all existing
5795 dynamic printfs immediately. (If you need individual control over the
5796 print commands, simply define normal breakpoints with
5797 explicitly-supplied command lists.)
5801 @kindex dprintf-style gdb
5802 Handle the output using the @value{GDBN} @code{printf} command.
5805 @kindex dprintf-style call
5806 Handle the output by calling a function in your program (normally
5810 @kindex dprintf-style agent
5811 Have the remote debugging agent (such as @code{gdbserver}) handle
5812 the output itself. This style is only available for agents that
5813 support running commands on the target.
5816 @item set dprintf-function @var{function}
5817 Set the function to call if the dprintf style is @code{call}. By
5818 default its value is @code{printf}. You may set it to any expression.
5819 that @value{GDBN} can evaluate to a function, as per the @code{call}
5822 @item set dprintf-channel @var{channel}
5823 Set a ``channel'' for dprintf. If set to a non-empty value,
5824 @value{GDBN} will evaluate it as an expression and pass the result as
5825 a first argument to the @code{dprintf-function}, in the manner of
5826 @code{fprintf} and similar functions. Otherwise, the dprintf format
5827 string will be the first argument, in the manner of @code{printf}.
5829 As an example, if you wanted @code{dprintf} output to go to a logfile
5830 that is a standard I/O stream assigned to the variable @code{mylog},
5831 you could do the following:
5834 (gdb) set dprintf-style call
5835 (gdb) set dprintf-function fprintf
5836 (gdb) set dprintf-channel mylog
5837 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5838 Dprintf 1 at 0x123456: file main.c, line 25.
5840 1 dprintf keep y 0x00123456 in main at main.c:25
5841 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5846 Note that the @code{info break} displays the dynamic printf commands
5847 as normal breakpoint commands; you can thus easily see the effect of
5848 the variable settings.
5850 @item set disconnected-dprintf on
5851 @itemx set disconnected-dprintf off
5852 @kindex set disconnected-dprintf
5853 Choose whether @code{dprintf} commands should continue to run if
5854 @value{GDBN} has disconnected from the target. This only applies
5855 if the @code{dprintf-style} is @code{agent}.
5857 @item show disconnected-dprintf off
5858 @kindex show disconnected-dprintf
5859 Show the current choice for disconnected @code{dprintf}.
5863 @value{GDBN} does not check the validity of function and channel,
5864 relying on you to supply values that are meaningful for the contexts
5865 in which they are being used. For instance, the function and channel
5866 may be the values of local variables, but if that is the case, then
5867 all enabled dynamic prints must be at locations within the scope of
5868 those locals. If evaluation fails, @value{GDBN} will report an error.
5870 @node Save Breakpoints
5871 @subsection How to save breakpoints to a file
5873 To save breakpoint definitions to a file use the @w{@code{save
5874 breakpoints}} command.
5877 @kindex save breakpoints
5878 @cindex save breakpoints to a file for future sessions
5879 @item save breakpoints [@var{filename}]
5880 This command saves all current breakpoint definitions together with
5881 their commands and ignore counts, into a file @file{@var{filename}}
5882 suitable for use in a later debugging session. This includes all
5883 types of breakpoints (breakpoints, watchpoints, catchpoints,
5884 tracepoints). To read the saved breakpoint definitions, use the
5885 @code{source} command (@pxref{Command Files}). Note that watchpoints
5886 with expressions involving local variables may fail to be recreated
5887 because it may not be possible to access the context where the
5888 watchpoint is valid anymore. Because the saved breakpoint definitions
5889 are simply a sequence of @value{GDBN} commands that recreate the
5890 breakpoints, you can edit the file in your favorite editing program,
5891 and remove the breakpoint definitions you're not interested in, or
5892 that can no longer be recreated.
5895 @node Static Probe Points
5896 @subsection Static Probe Points
5898 @cindex static probe point, SystemTap
5899 @cindex static probe point, DTrace
5900 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5901 for Statically Defined Tracing, and the probes are designed to have a tiny
5902 runtime code and data footprint, and no dynamic relocations.
5904 Currently, the following types of probes are supported on
5905 ELF-compatible systems:
5909 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5910 @acronym{SDT} probes@footnote{See
5911 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5912 for more information on how to add @code{SystemTap} @acronym{SDT}
5913 probes in your applications.}. @code{SystemTap} probes are usable
5914 from assembly, C and C@t{++} languages@footnote{See
5915 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5916 for a good reference on how the @acronym{SDT} probes are implemented.}.
5918 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5919 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5923 @cindex semaphores on static probe points
5924 Some @code{SystemTap} probes have an associated semaphore variable;
5925 for instance, this happens automatically if you defined your probe
5926 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5927 @value{GDBN} will automatically enable it when you specify a
5928 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5929 breakpoint at a probe's location by some other method (e.g.,
5930 @code{break file:line}), then @value{GDBN} will not automatically set
5931 the semaphore. @code{DTrace} probes do not support semaphores.
5933 You can examine the available static static probes using @code{info
5934 probes}, with optional arguments:
5938 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5939 If given, @var{type} is either @code{stap} for listing
5940 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5941 probes. If omitted all probes are listed regardless of their types.
5943 If given, @var{provider} is a regular expression used to match against provider
5944 names when selecting which probes to list. If omitted, probes by all
5945 probes from all providers are listed.
5947 If given, @var{name} is a regular expression to match against probe names
5948 when selecting which probes to list. If omitted, probe names are not
5949 considered when deciding whether to display them.
5951 If given, @var{objfile} is a regular expression used to select which
5952 object files (executable or shared libraries) to examine. If not
5953 given, all object files are considered.
5955 @item info probes all
5956 List the available static probes, from all types.
5959 @cindex enabling and disabling probes
5960 Some probe points can be enabled and/or disabled. The effect of
5961 enabling or disabling a probe depends on the type of probe being
5962 handled. Some @code{DTrace} probes can be enabled or
5963 disabled, but @code{SystemTap} probes cannot be disabled.
5965 You can enable (or disable) one or more probes using the following
5966 commands, with optional arguments:
5969 @kindex enable probes
5970 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5971 If given, @var{provider} is a regular expression used to match against
5972 provider names when selecting which probes to enable. If omitted,
5973 all probes from all providers are enabled.
5975 If given, @var{name} is a regular expression to match against probe
5976 names when selecting which probes to enable. If omitted, probe names
5977 are not considered when deciding whether to enable them.
5979 If given, @var{objfile} is a regular expression used to select which
5980 object files (executable or shared libraries) to examine. If not
5981 given, all object files are considered.
5983 @kindex disable probes
5984 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5985 See the @code{enable probes} command above for a description of the
5986 optional arguments accepted by this command.
5989 @vindex $_probe_arg@r{, convenience variable}
5990 A probe may specify up to twelve arguments. These are available at the
5991 point at which the probe is defined---that is, when the current PC is
5992 at the probe's location. The arguments are available using the
5993 convenience variables (@pxref{Convenience Vars})
5994 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5995 probes each probe argument is an integer of the appropriate size;
5996 types are not preserved. In @code{DTrace} probes types are preserved
5997 provided that they are recognized as such by @value{GDBN}; otherwise
5998 the value of the probe argument will be a long integer. The
5999 convenience variable @code{$_probe_argc} holds the number of arguments
6000 at the current probe point.
6002 These variables are always available, but attempts to access them at
6003 any location other than a probe point will cause @value{GDBN} to give
6007 @c @ifclear BARETARGET
6008 @node Error in Breakpoints
6009 @subsection ``Cannot insert breakpoints''
6011 If you request too many active hardware-assisted breakpoints and
6012 watchpoints, you will see this error message:
6014 @c FIXME: the precise wording of this message may change; the relevant
6015 @c source change is not committed yet (Sep 3, 1999).
6017 Stopped; cannot insert breakpoints.
6018 You may have requested too many hardware breakpoints and watchpoints.
6022 This message is printed when you attempt to resume the program, since
6023 only then @value{GDBN} knows exactly how many hardware breakpoints and
6024 watchpoints it needs to insert.
6026 When this message is printed, you need to disable or remove some of the
6027 hardware-assisted breakpoints and watchpoints, and then continue.
6029 @node Breakpoint-related Warnings
6030 @subsection ``Breakpoint address adjusted...''
6031 @cindex breakpoint address adjusted
6033 Some processor architectures place constraints on the addresses at
6034 which breakpoints may be placed. For architectures thus constrained,
6035 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6036 with the constraints dictated by the architecture.
6038 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6039 a VLIW architecture in which a number of RISC-like instructions may be
6040 bundled together for parallel execution. The FR-V architecture
6041 constrains the location of a breakpoint instruction within such a
6042 bundle to the instruction with the lowest address. @value{GDBN}
6043 honors this constraint by adjusting a breakpoint's address to the
6044 first in the bundle.
6046 It is not uncommon for optimized code to have bundles which contain
6047 instructions from different source statements, thus it may happen that
6048 a breakpoint's address will be adjusted from one source statement to
6049 another. Since this adjustment may significantly alter @value{GDBN}'s
6050 breakpoint related behavior from what the user expects, a warning is
6051 printed when the breakpoint is first set and also when the breakpoint
6054 A warning like the one below is printed when setting a breakpoint
6055 that's been subject to address adjustment:
6058 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6061 Such warnings are printed both for user settable and @value{GDBN}'s
6062 internal breakpoints. If you see one of these warnings, you should
6063 verify that a breakpoint set at the adjusted address will have the
6064 desired affect. If not, the breakpoint in question may be removed and
6065 other breakpoints may be set which will have the desired behavior.
6066 E.g., it may be sufficient to place the breakpoint at a later
6067 instruction. A conditional breakpoint may also be useful in some
6068 cases to prevent the breakpoint from triggering too often.
6070 @value{GDBN} will also issue a warning when stopping at one of these
6071 adjusted breakpoints:
6074 warning: Breakpoint 1 address previously adjusted from 0x00010414
6078 When this warning is encountered, it may be too late to take remedial
6079 action except in cases where the breakpoint is hit earlier or more
6080 frequently than expected.
6082 @node Continuing and Stepping
6083 @section Continuing and Stepping
6087 @cindex resuming execution
6088 @dfn{Continuing} means resuming program execution until your program
6089 completes normally. In contrast, @dfn{stepping} means executing just
6090 one more ``step'' of your program, where ``step'' may mean either one
6091 line of source code, or one machine instruction (depending on what
6092 particular command you use). Either when continuing or when stepping,
6093 your program may stop even sooner, due to a breakpoint or a signal. (If
6094 it stops due to a signal, you may want to use @code{handle}, or use
6095 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6096 or you may step into the signal's handler (@pxref{stepping and signal
6101 @kindex c @r{(@code{continue})}
6102 @kindex fg @r{(resume foreground execution)}
6103 @item continue @r{[}@var{ignore-count}@r{]}
6104 @itemx c @r{[}@var{ignore-count}@r{]}
6105 @itemx fg @r{[}@var{ignore-count}@r{]}
6106 Resume program execution, at the address where your program last stopped;
6107 any breakpoints set at that address are bypassed. The optional argument
6108 @var{ignore-count} allows you to specify a further number of times to
6109 ignore a breakpoint at this location; its effect is like that of
6110 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6112 The argument @var{ignore-count} is meaningful only when your program
6113 stopped due to a breakpoint. At other times, the argument to
6114 @code{continue} is ignored.
6116 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6117 debugged program is deemed to be the foreground program) are provided
6118 purely for convenience, and have exactly the same behavior as
6122 To resume execution at a different place, you can use @code{return}
6123 (@pxref{Returning, ,Returning from a Function}) to go back to the
6124 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6125 Different Address}) to go to an arbitrary location in your program.
6127 A typical technique for using stepping is to set a breakpoint
6128 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6129 beginning of the function or the section of your program where a problem
6130 is believed to lie, run your program until it stops at that breakpoint,
6131 and then step through the suspect area, examining the variables that are
6132 interesting, until you see the problem happen.
6136 @kindex s @r{(@code{step})}
6138 Continue running your program until control reaches a different source
6139 line, then stop it and return control to @value{GDBN}. This command is
6140 abbreviated @code{s}.
6143 @c "without debugging information" is imprecise; actually "without line
6144 @c numbers in the debugging information". (gcc -g1 has debugging info but
6145 @c not line numbers). But it seems complex to try to make that
6146 @c distinction here.
6147 @emph{Warning:} If you use the @code{step} command while control is
6148 within a function that was compiled without debugging information,
6149 execution proceeds until control reaches a function that does have
6150 debugging information. Likewise, it will not step into a function which
6151 is compiled without debugging information. To step through functions
6152 without debugging information, use the @code{stepi} command, described
6156 The @code{step} command only stops at the first instruction of a source
6157 line. This prevents the multiple stops that could otherwise occur in
6158 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6159 to stop if a function that has debugging information is called within
6160 the line. In other words, @code{step} @emph{steps inside} any functions
6161 called within the line.
6163 Also, the @code{step} command only enters a function if there is line
6164 number information for the function. Otherwise it acts like the
6165 @code{next} command. This avoids problems when using @code{cc -gl}
6166 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6167 was any debugging information about the routine.
6169 @item step @var{count}
6170 Continue running as in @code{step}, but do so @var{count} times. If a
6171 breakpoint is reached, or a signal not related to stepping occurs before
6172 @var{count} steps, stepping stops right away.
6175 @kindex n @r{(@code{next})}
6176 @item next @r{[}@var{count}@r{]}
6177 Continue to the next source line in the current (innermost) stack frame.
6178 This is similar to @code{step}, but function calls that appear within
6179 the line of code are executed without stopping. Execution stops when
6180 control reaches a different line of code at the original stack level
6181 that was executing when you gave the @code{next} command. This command
6182 is abbreviated @code{n}.
6184 An argument @var{count} is a repeat count, as for @code{step}.
6187 @c FIX ME!! Do we delete this, or is there a way it fits in with
6188 @c the following paragraph? --- Vctoria
6190 @c @code{next} within a function that lacks debugging information acts like
6191 @c @code{step}, but any function calls appearing within the code of the
6192 @c function are executed without stopping.
6194 The @code{next} command only stops at the first instruction of a
6195 source line. This prevents multiple stops that could otherwise occur in
6196 @code{switch} statements, @code{for} loops, etc.
6198 @kindex set step-mode
6200 @cindex functions without line info, and stepping
6201 @cindex stepping into functions with no line info
6202 @itemx set step-mode on
6203 The @code{set step-mode on} command causes the @code{step} command to
6204 stop at the first instruction of a function which contains no debug line
6205 information rather than stepping over it.
6207 This is useful in cases where you may be interested in inspecting the
6208 machine instructions of a function which has no symbolic info and do not
6209 want @value{GDBN} to automatically skip over this function.
6211 @item set step-mode off
6212 Causes the @code{step} command to step over any functions which contains no
6213 debug information. This is the default.
6215 @item show step-mode
6216 Show whether @value{GDBN} will stop in or step over functions without
6217 source line debug information.
6220 @kindex fin @r{(@code{finish})}
6222 Continue running until just after function in the selected stack frame
6223 returns. Print the returned value (if any). This command can be
6224 abbreviated as @code{fin}.
6226 Contrast this with the @code{return} command (@pxref{Returning,
6227 ,Returning from a Function}).
6229 @kindex set print finish
6230 @kindex show print finish
6231 @item set print finish @r{[}on|off@r{]}
6232 @itemx show print finish
6233 By default the @code{finish} command will show the value that is
6234 returned by the function. This can be disabled using @code{set print
6235 finish off}. When disabled, the value is still entered into the value
6236 history (@pxref{Value History}), but not displayed.
6239 @kindex u @r{(@code{until})}
6240 @cindex run until specified location
6243 Continue running until a source line past the current line, in the
6244 current stack frame, is reached. This command is used to avoid single
6245 stepping through a loop more than once. It is like the @code{next}
6246 command, except that when @code{until} encounters a jump, it
6247 automatically continues execution until the program counter is greater
6248 than the address of the jump.
6250 This means that when you reach the end of a loop after single stepping
6251 though it, @code{until} makes your program continue execution until it
6252 exits the loop. In contrast, a @code{next} command at the end of a loop
6253 simply steps back to the beginning of the loop, which forces you to step
6254 through the next iteration.
6256 @code{until} always stops your program if it attempts to exit the current
6259 @code{until} may produce somewhat counterintuitive results if the order
6260 of machine code does not match the order of the source lines. For
6261 example, in the following excerpt from a debugging session, the @code{f}
6262 (@code{frame}) command shows that execution is stopped at line
6263 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6267 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6269 (@value{GDBP}) until
6270 195 for ( ; argc > 0; NEXTARG) @{
6273 This happened because, for execution efficiency, the compiler had
6274 generated code for the loop closure test at the end, rather than the
6275 start, of the loop---even though the test in a C @code{for}-loop is
6276 written before the body of the loop. The @code{until} command appeared
6277 to step back to the beginning of the loop when it advanced to this
6278 expression; however, it has not really gone to an earlier
6279 statement---not in terms of the actual machine code.
6281 @code{until} with no argument works by means of single
6282 instruction stepping, and hence is slower than @code{until} with an
6285 @item until @var{location}
6286 @itemx u @var{location}
6287 Continue running your program until either the specified @var{location} is
6288 reached, or the current stack frame returns. The location is any of
6289 the forms described in @ref{Specify Location}.
6290 This form of the command uses temporary breakpoints, and
6291 hence is quicker than @code{until} without an argument. The specified
6292 location is actually reached only if it is in the current frame. This
6293 implies that @code{until} can be used to skip over recursive function
6294 invocations. For instance in the code below, if the current location is
6295 line @code{96}, issuing @code{until 99} will execute the program up to
6296 line @code{99} in the same invocation of factorial, i.e., after the inner
6297 invocations have returned.
6300 94 int factorial (int value)
6302 96 if (value > 1) @{
6303 97 value *= factorial (value - 1);
6310 @kindex advance @var{location}
6311 @item advance @var{location}
6312 Continue running the program up to the given @var{location}. An argument is
6313 required, which should be of one of the forms described in
6314 @ref{Specify Location}.
6315 Execution will also stop upon exit from the current stack
6316 frame. This command is similar to @code{until}, but @code{advance} will
6317 not skip over recursive function calls, and the target location doesn't
6318 have to be in the same frame as the current one.
6322 @kindex si @r{(@code{stepi})}
6324 @itemx stepi @var{arg}
6326 Execute one machine instruction, then stop and return to the debugger.
6328 It is often useful to do @samp{display/i $pc} when stepping by machine
6329 instructions. This makes @value{GDBN} automatically display the next
6330 instruction to be executed, each time your program stops. @xref{Auto
6331 Display,, Automatic Display}.
6333 An argument is a repeat count, as in @code{step}.
6337 @kindex ni @r{(@code{nexti})}
6339 @itemx nexti @var{arg}
6341 Execute one machine instruction, but if it is a function call,
6342 proceed until the function returns.
6344 An argument is a repeat count, as in @code{next}.
6348 @anchor{range stepping}
6349 @cindex range stepping
6350 @cindex target-assisted range stepping
6351 By default, and if available, @value{GDBN} makes use of
6352 target-assisted @dfn{range stepping}. In other words, whenever you
6353 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6354 tells the target to step the corresponding range of instruction
6355 addresses instead of issuing multiple single-steps. This speeds up
6356 line stepping, particularly for remote targets. Ideally, there should
6357 be no reason you would want to turn range stepping off. However, it's
6358 possible that a bug in the debug info, a bug in the remote stub (for
6359 remote targets), or even a bug in @value{GDBN} could make line
6360 stepping behave incorrectly when target-assisted range stepping is
6361 enabled. You can use the following command to turn off range stepping
6365 @kindex set range-stepping
6366 @kindex show range-stepping
6367 @item set range-stepping
6368 @itemx show range-stepping
6369 Control whether range stepping is enabled.
6371 If @code{on}, and the target supports it, @value{GDBN} tells the
6372 target to step a range of addresses itself, instead of issuing
6373 multiple single-steps. If @code{off}, @value{GDBN} always issues
6374 single-steps, even if range stepping is supported by the target. The
6375 default is @code{on}.
6379 @node Skipping Over Functions and Files
6380 @section Skipping Over Functions and Files
6381 @cindex skipping over functions and files
6383 The program you are debugging may contain some functions which are
6384 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6385 skip a function, all functions in a file or a particular function in
6386 a particular file when stepping.
6388 For example, consider the following C function:
6399 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6400 are not interested in stepping through @code{boring}. If you run @code{step}
6401 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6402 step over both @code{foo} and @code{boring}!
6404 One solution is to @code{step} into @code{boring} and use the @code{finish}
6405 command to immediately exit it. But this can become tedious if @code{boring}
6406 is called from many places.
6408 A more flexible solution is to execute @kbd{skip boring}. This instructs
6409 @value{GDBN} never to step into @code{boring}. Now when you execute
6410 @code{step} at line 103, you'll step over @code{boring} and directly into
6413 Functions may be skipped by providing either a function name, linespec
6414 (@pxref{Specify Location}), regular expression that matches the function's
6415 name, file name or a @code{glob}-style pattern that matches the file name.
6417 On Posix systems the form of the regular expression is
6418 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6419 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6420 expression is whatever is provided by the @code{regcomp} function of
6421 the underlying system.
6422 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6423 description of @code{glob}-style patterns.
6427 @item skip @r{[}@var{options}@r{]}
6428 The basic form of the @code{skip} command takes zero or more options
6429 that specify what to skip.
6430 The @var{options} argument is any useful combination of the following:
6433 @item -file @var{file}
6434 @itemx -fi @var{file}
6435 Functions in @var{file} will be skipped over when stepping.
6437 @item -gfile @var{file-glob-pattern}
6438 @itemx -gfi @var{file-glob-pattern}
6439 @cindex skipping over files via glob-style patterns
6440 Functions in files matching @var{file-glob-pattern} will be skipped
6444 (gdb) skip -gfi utils/*.c
6447 @item -function @var{linespec}
6448 @itemx -fu @var{linespec}
6449 Functions named by @var{linespec} or the function containing the line
6450 named by @var{linespec} will be skipped over when stepping.
6451 @xref{Specify Location}.
6453 @item -rfunction @var{regexp}
6454 @itemx -rfu @var{regexp}
6455 @cindex skipping over functions via regular expressions
6456 Functions whose name matches @var{regexp} will be skipped over when stepping.
6458 This form is useful for complex function names.
6459 For example, there is generally no need to step into C@t{++} @code{std::string}
6460 constructors or destructors. Plus with C@t{++} templates it can be hard to
6461 write out the full name of the function, and often it doesn't matter what
6462 the template arguments are. Specifying the function to be skipped as a
6463 regular expression makes this easier.
6466 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6469 If you want to skip every templated C@t{++} constructor and destructor
6470 in the @code{std} namespace you can do:
6473 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6477 If no options are specified, the function you're currently debugging
6480 @kindex skip function
6481 @item skip function @r{[}@var{linespec}@r{]}
6482 After running this command, the function named by @var{linespec} or the
6483 function containing the line named by @var{linespec} will be skipped over when
6484 stepping. @xref{Specify Location}.
6486 If you do not specify @var{linespec}, the function you're currently debugging
6489 (If you have a function called @code{file} that you want to skip, use
6490 @kbd{skip function file}.)
6493 @item skip file @r{[}@var{filename}@r{]}
6494 After running this command, any function whose source lives in @var{filename}
6495 will be skipped over when stepping.
6498 (gdb) skip file boring.c
6499 File boring.c will be skipped when stepping.
6502 If you do not specify @var{filename}, functions whose source lives in the file
6503 you're currently debugging will be skipped.
6506 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6507 These are the commands for managing your list of skips:
6511 @item info skip @r{[}@var{range}@r{]}
6512 Print details about the specified skip(s). If @var{range} is not specified,
6513 print a table with details about all functions and files marked for skipping.
6514 @code{info skip} prints the following information about each skip:
6518 A number identifying this skip.
6519 @item Enabled or Disabled
6520 Enabled skips are marked with @samp{y}.
6521 Disabled skips are marked with @samp{n}.
6523 If the file name is a @samp{glob} pattern this is @samp{y}.
6524 Otherwise it is @samp{n}.
6526 The name or @samp{glob} pattern of the file to be skipped.
6527 If no file is specified this is @samp{<none>}.
6529 If the function name is a @samp{regular expression} this is @samp{y}.
6530 Otherwise it is @samp{n}.
6532 The name or regular expression of the function to skip.
6533 If no function is specified this is @samp{<none>}.
6537 @item skip delete @r{[}@var{range}@r{]}
6538 Delete the specified skip(s). If @var{range} is not specified, delete all
6542 @item skip enable @r{[}@var{range}@r{]}
6543 Enable the specified skip(s). If @var{range} is not specified, enable all
6546 @kindex skip disable
6547 @item skip disable @r{[}@var{range}@r{]}
6548 Disable the specified skip(s). If @var{range} is not specified, disable all
6551 @kindex set debug skip
6552 @item set debug skip @r{[}on|off@r{]}
6553 Set whether to print the debug output about skipping files and functions.
6555 @kindex show debug skip
6556 @item show debug skip
6557 Show whether the debug output about skipping files and functions is printed.
6565 A signal is an asynchronous event that can happen in a program. The
6566 operating system defines the possible kinds of signals, and gives each
6567 kind a name and a number. For example, in Unix @code{SIGINT} is the
6568 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6569 @code{SIGSEGV} is the signal a program gets from referencing a place in
6570 memory far away from all the areas in use; @code{SIGALRM} occurs when
6571 the alarm clock timer goes off (which happens only if your program has
6572 requested an alarm).
6574 @cindex fatal signals
6575 Some signals, including @code{SIGALRM}, are a normal part of the
6576 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6577 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6578 program has not specified in advance some other way to handle the signal.
6579 @code{SIGINT} does not indicate an error in your program, but it is normally
6580 fatal so it can carry out the purpose of the interrupt: to kill the program.
6582 @value{GDBN} has the ability to detect any occurrence of a signal in your
6583 program. You can tell @value{GDBN} in advance what to do for each kind of
6586 @cindex handling signals
6587 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6588 @code{SIGALRM} be silently passed to your program
6589 (so as not to interfere with their role in the program's functioning)
6590 but to stop your program immediately whenever an error signal happens.
6591 You can change these settings with the @code{handle} command.
6594 @kindex info signals
6598 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6599 handle each one. You can use this to see the signal numbers of all
6600 the defined types of signals.
6602 @item info signals @var{sig}
6603 Similar, but print information only about the specified signal number.
6605 @code{info handle} is an alias for @code{info signals}.
6607 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6608 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6609 for details about this command.
6612 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6613 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6614 can be the number of a signal or its name (with or without the
6615 @samp{SIG} at the beginning); a list of signal numbers of the form
6616 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6617 known signals. Optional arguments @var{keywords}, described below,
6618 say what change to make.
6622 The keywords allowed by the @code{handle} command can be abbreviated.
6623 Their full names are:
6627 @value{GDBN} should not stop your program when this signal happens. It may
6628 still print a message telling you that the signal has come in.
6631 @value{GDBN} should stop your program when this signal happens. This implies
6632 the @code{print} keyword as well.
6635 @value{GDBN} should print a message when this signal happens.
6638 @value{GDBN} should not mention the occurrence of the signal at all. This
6639 implies the @code{nostop} keyword as well.
6643 @value{GDBN} should allow your program to see this signal; your program
6644 can handle the signal, or else it may terminate if the signal is fatal
6645 and not handled. @code{pass} and @code{noignore} are synonyms.
6649 @value{GDBN} should not allow your program to see this signal.
6650 @code{nopass} and @code{ignore} are synonyms.
6654 When a signal stops your program, the signal is not visible to the
6656 continue. Your program sees the signal then, if @code{pass} is in
6657 effect for the signal in question @emph{at that time}. In other words,
6658 after @value{GDBN} reports a signal, you can use the @code{handle}
6659 command with @code{pass} or @code{nopass} to control whether your
6660 program sees that signal when you continue.
6662 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6663 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6664 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6667 You can also use the @code{signal} command to prevent your program from
6668 seeing a signal, or cause it to see a signal it normally would not see,
6669 or to give it any signal at any time. For example, if your program stopped
6670 due to some sort of memory reference error, you might store correct
6671 values into the erroneous variables and continue, hoping to see more
6672 execution; but your program would probably terminate immediately as
6673 a result of the fatal signal once it saw the signal. To prevent this,
6674 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6677 @cindex stepping and signal handlers
6678 @anchor{stepping and signal handlers}
6680 @value{GDBN} optimizes for stepping the mainline code. If a signal
6681 that has @code{handle nostop} and @code{handle pass} set arrives while
6682 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6683 in progress, @value{GDBN} lets the signal handler run and then resumes
6684 stepping the mainline code once the signal handler returns. In other
6685 words, @value{GDBN} steps over the signal handler. This prevents
6686 signals that you've specified as not interesting (with @code{handle
6687 nostop}) from changing the focus of debugging unexpectedly. Note that
6688 the signal handler itself may still hit a breakpoint, stop for another
6689 signal that has @code{handle stop} in effect, or for any other event
6690 that normally results in stopping the stepping command sooner. Also
6691 note that @value{GDBN} still informs you that the program received a
6692 signal if @code{handle print} is set.
6694 @anchor{stepping into signal handlers}
6696 If you set @code{handle pass} for a signal, and your program sets up a
6697 handler for it, then issuing a stepping command, such as @code{step}
6698 or @code{stepi}, when your program is stopped due to the signal will
6699 step @emph{into} the signal handler (if the target supports that).
6701 Likewise, if you use the @code{queue-signal} command to queue a signal
6702 to be delivered to the current thread when execution of the thread
6703 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6704 stepping command will step into the signal handler.
6706 Here's an example, using @code{stepi} to step to the first instruction
6707 of @code{SIGUSR1}'s handler:
6710 (@value{GDBP}) handle SIGUSR1
6711 Signal Stop Print Pass to program Description
6712 SIGUSR1 Yes Yes Yes User defined signal 1
6716 Program received signal SIGUSR1, User defined signal 1.
6717 main () sigusr1.c:28
6720 sigusr1_handler () at sigusr1.c:9
6724 The same, but using @code{queue-signal} instead of waiting for the
6725 program to receive the signal first:
6730 (@value{GDBP}) queue-signal SIGUSR1
6732 sigusr1_handler () at sigusr1.c:9
6737 @cindex extra signal information
6738 @anchor{extra signal information}
6740 On some targets, @value{GDBN} can inspect extra signal information
6741 associated with the intercepted signal, before it is actually
6742 delivered to the program being debugged. This information is exported
6743 by the convenience variable @code{$_siginfo}, and consists of data
6744 that is passed by the kernel to the signal handler at the time of the
6745 receipt of a signal. The data type of the information itself is
6746 target dependent. You can see the data type using the @code{ptype
6747 $_siginfo} command. On Unix systems, it typically corresponds to the
6748 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6751 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6752 referenced address that raised a segmentation fault.
6756 (@value{GDBP}) continue
6757 Program received signal SIGSEGV, Segmentation fault.
6758 0x0000000000400766 in main ()
6760 (@value{GDBP}) ptype $_siginfo
6767 struct @{...@} _kill;
6768 struct @{...@} _timer;
6770 struct @{...@} _sigchld;
6771 struct @{...@} _sigfault;
6772 struct @{...@} _sigpoll;
6775 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6779 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6780 $1 = (void *) 0x7ffff7ff7000
6784 Depending on target support, @code{$_siginfo} may also be writable.
6786 @cindex Intel MPX boundary violations
6787 @cindex boundary violations, Intel MPX
6788 On some targets, a @code{SIGSEGV} can be caused by a boundary
6789 violation, i.e., accessing an address outside of the allowed range.
6790 In those cases @value{GDBN} may displays additional information,
6791 depending on how @value{GDBN} has been told to handle the signal.
6792 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6793 kind: "Upper" or "Lower", the memory address accessed and the
6794 bounds, while with @code{handle nostop SIGSEGV} no additional
6795 information is displayed.
6797 The usual output of a segfault is:
6799 Program received signal SIGSEGV, Segmentation fault
6800 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6801 68 value = *(p + len);
6804 While a bound violation is presented as:
6806 Program received signal SIGSEGV, Segmentation fault
6807 Upper bound violation while accessing address 0x7fffffffc3b3
6808 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6809 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6810 68 value = *(p + len);
6814 @section Stopping and Starting Multi-thread Programs
6816 @cindex stopped threads
6817 @cindex threads, stopped
6819 @cindex continuing threads
6820 @cindex threads, continuing
6822 @value{GDBN} supports debugging programs with multiple threads
6823 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6824 are two modes of controlling execution of your program within the
6825 debugger. In the default mode, referred to as @dfn{all-stop mode},
6826 when any thread in your program stops (for example, at a breakpoint
6827 or while being stepped), all other threads in the program are also stopped by
6828 @value{GDBN}. On some targets, @value{GDBN} also supports
6829 @dfn{non-stop mode}, in which other threads can continue to run freely while
6830 you examine the stopped thread in the debugger.
6833 * All-Stop Mode:: All threads stop when GDB takes control
6834 * Non-Stop Mode:: Other threads continue to execute
6835 * Background Execution:: Running your program asynchronously
6836 * Thread-Specific Breakpoints:: Controlling breakpoints
6837 * Interrupted System Calls:: GDB may interfere with system calls
6838 * Observer Mode:: GDB does not alter program behavior
6842 @subsection All-Stop Mode
6844 @cindex all-stop mode
6846 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6847 @emph{all} threads of execution stop, not just the current thread. This
6848 allows you to examine the overall state of the program, including
6849 switching between threads, without worrying that things may change
6852 Conversely, whenever you restart the program, @emph{all} threads start
6853 executing. @emph{This is true even when single-stepping} with commands
6854 like @code{step} or @code{next}.
6856 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6857 Since thread scheduling is up to your debugging target's operating
6858 system (not controlled by @value{GDBN}), other threads may
6859 execute more than one statement while the current thread completes a
6860 single step. Moreover, in general other threads stop in the middle of a
6861 statement, rather than at a clean statement boundary, when the program
6864 You might even find your program stopped in another thread after
6865 continuing or even single-stepping. This happens whenever some other
6866 thread runs into a breakpoint, a signal, or an exception before the
6867 first thread completes whatever you requested.
6869 @cindex automatic thread selection
6870 @cindex switching threads automatically
6871 @cindex threads, automatic switching
6872 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6873 signal, it automatically selects the thread where that breakpoint or
6874 signal happened. @value{GDBN} alerts you to the context switch with a
6875 message such as @samp{[Switching to Thread @var{n}]} to identify the
6878 On some OSes, you can modify @value{GDBN}'s default behavior by
6879 locking the OS scheduler to allow only a single thread to run.
6882 @item set scheduler-locking @var{mode}
6883 @cindex scheduler locking mode
6884 @cindex lock scheduler
6885 Set the scheduler locking mode. It applies to normal execution,
6886 record mode, and replay mode. If it is @code{off}, then there is no
6887 locking and any thread may run at any time. If @code{on}, then only
6888 the current thread may run when the inferior is resumed. The
6889 @code{step} mode optimizes for single-stepping; it prevents other
6890 threads from preempting the current thread while you are stepping, so
6891 that the focus of debugging does not change unexpectedly. Other
6892 threads never get a chance to run when you step, and they are
6893 completely free to run when you use commands like @samp{continue},
6894 @samp{until}, or @samp{finish}. However, unless another thread hits a
6895 breakpoint during its timeslice, @value{GDBN} does not change the
6896 current thread away from the thread that you are debugging. The
6897 @code{replay} mode behaves like @code{off} in record mode and like
6898 @code{on} in replay mode.
6900 @item show scheduler-locking
6901 Display the current scheduler locking mode.
6904 @cindex resume threads of multiple processes simultaneously
6905 By default, when you issue one of the execution commands such as
6906 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6907 threads of the current inferior to run. For example, if @value{GDBN}
6908 is attached to two inferiors, each with two threads, the
6909 @code{continue} command resumes only the two threads of the current
6910 inferior. This is useful, for example, when you debug a program that
6911 forks and you want to hold the parent stopped (so that, for instance,
6912 it doesn't run to exit), while you debug the child. In other
6913 situations, you may not be interested in inspecting the current state
6914 of any of the processes @value{GDBN} is attached to, and you may want
6915 to resume them all until some breakpoint is hit. In the latter case,
6916 you can instruct @value{GDBN} to allow all threads of all the
6917 inferiors to run with the @w{@code{set schedule-multiple}} command.
6920 @kindex set schedule-multiple
6921 @item set schedule-multiple
6922 Set the mode for allowing threads of multiple processes to be resumed
6923 when an execution command is issued. When @code{on}, all threads of
6924 all processes are allowed to run. When @code{off}, only the threads
6925 of the current process are resumed. The default is @code{off}. The
6926 @code{scheduler-locking} mode takes precedence when set to @code{on},
6927 or while you are stepping and set to @code{step}.
6929 @item show schedule-multiple
6930 Display the current mode for resuming the execution of threads of
6935 @subsection Non-Stop Mode
6937 @cindex non-stop mode
6939 @c This section is really only a place-holder, and needs to be expanded
6940 @c with more details.
6942 For some multi-threaded targets, @value{GDBN} supports an optional
6943 mode of operation in which you can examine stopped program threads in
6944 the debugger while other threads continue to execute freely. This
6945 minimizes intrusion when debugging live systems, such as programs
6946 where some threads have real-time constraints or must continue to
6947 respond to external events. This is referred to as @dfn{non-stop} mode.
6949 In non-stop mode, when a thread stops to report a debugging event,
6950 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6951 threads as well, in contrast to the all-stop mode behavior. Additionally,
6952 execution commands such as @code{continue} and @code{step} apply by default
6953 only to the current thread in non-stop mode, rather than all threads as
6954 in all-stop mode. This allows you to control threads explicitly in
6955 ways that are not possible in all-stop mode --- for example, stepping
6956 one thread while allowing others to run freely, stepping
6957 one thread while holding all others stopped, or stepping several threads
6958 independently and simultaneously.
6960 To enter non-stop mode, use this sequence of commands before you run
6961 or attach to your program:
6964 # If using the CLI, pagination breaks non-stop.
6967 # Finally, turn it on!
6971 You can use these commands to manipulate the non-stop mode setting:
6974 @kindex set non-stop
6975 @item set non-stop on
6976 Enable selection of non-stop mode.
6977 @item set non-stop off
6978 Disable selection of non-stop mode.
6979 @kindex show non-stop
6981 Show the current non-stop enablement setting.
6984 Note these commands only reflect whether non-stop mode is enabled,
6985 not whether the currently-executing program is being run in non-stop mode.
6986 In particular, the @code{set non-stop} preference is only consulted when
6987 @value{GDBN} starts or connects to the target program, and it is generally
6988 not possible to switch modes once debugging has started. Furthermore,
6989 since not all targets support non-stop mode, even when you have enabled
6990 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6993 In non-stop mode, all execution commands apply only to the current thread
6994 by default. That is, @code{continue} only continues one thread.
6995 To continue all threads, issue @code{continue -a} or @code{c -a}.
6997 You can use @value{GDBN}'s background execution commands
6998 (@pxref{Background Execution}) to run some threads in the background
6999 while you continue to examine or step others from @value{GDBN}.
7000 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7001 always executed asynchronously in non-stop mode.
7003 Suspending execution is done with the @code{interrupt} command when
7004 running in the background, or @kbd{Ctrl-c} during foreground execution.
7005 In all-stop mode, this stops the whole process;
7006 but in non-stop mode the interrupt applies only to the current thread.
7007 To stop the whole program, use @code{interrupt -a}.
7009 Other execution commands do not currently support the @code{-a} option.
7011 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7012 that thread current, as it does in all-stop mode. This is because the
7013 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7014 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7015 changed to a different thread just as you entered a command to operate on the
7016 previously current thread.
7018 @node Background Execution
7019 @subsection Background Execution
7021 @cindex foreground execution
7022 @cindex background execution
7023 @cindex asynchronous execution
7024 @cindex execution, foreground, background and asynchronous
7026 @value{GDBN}'s execution commands have two variants: the normal
7027 foreground (synchronous) behavior, and a background
7028 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7029 the program to report that some thread has stopped before prompting for
7030 another command. In background execution, @value{GDBN} immediately gives
7031 a command prompt so that you can issue other commands while your program runs.
7033 If the target doesn't support async mode, @value{GDBN} issues an error
7034 message if you attempt to use the background execution commands.
7036 @cindex @code{&}, background execution of commands
7037 To specify background execution, add a @code{&} to the command. For example,
7038 the background form of the @code{continue} command is @code{continue&}, or
7039 just @code{c&}. The execution commands that accept background execution
7045 @xref{Starting, , Starting your Program}.
7049 @xref{Attach, , Debugging an Already-running Process}.
7053 @xref{Continuing and Stepping, step}.
7057 @xref{Continuing and Stepping, stepi}.
7061 @xref{Continuing and Stepping, next}.
7065 @xref{Continuing and Stepping, nexti}.
7069 @xref{Continuing and Stepping, continue}.
7073 @xref{Continuing and Stepping, finish}.
7077 @xref{Continuing and Stepping, until}.
7081 Background execution is especially useful in conjunction with non-stop
7082 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7083 However, you can also use these commands in the normal all-stop mode with
7084 the restriction that you cannot issue another execution command until the
7085 previous one finishes. Examples of commands that are valid in all-stop
7086 mode while the program is running include @code{help} and @code{info break}.
7088 You can interrupt your program while it is running in the background by
7089 using the @code{interrupt} command.
7096 Suspend execution of the running program. In all-stop mode,
7097 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7098 only the current thread. To stop the whole program in non-stop mode,
7099 use @code{interrupt -a}.
7102 @node Thread-Specific Breakpoints
7103 @subsection Thread-Specific Breakpoints
7105 When your program has multiple threads (@pxref{Threads,, Debugging
7106 Programs with Multiple Threads}), you can choose whether to set
7107 breakpoints on all threads, or on a particular thread.
7110 @cindex breakpoints and threads
7111 @cindex thread breakpoints
7112 @kindex break @dots{} thread @var{thread-id}
7113 @item break @var{location} thread @var{thread-id}
7114 @itemx break @var{location} thread @var{thread-id} if @dots{}
7115 @var{location} specifies source lines; there are several ways of
7116 writing them (@pxref{Specify Location}), but the effect is always to
7117 specify some source line.
7119 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7120 to specify that you only want @value{GDBN} to stop the program when a
7121 particular thread reaches this breakpoint. The @var{thread-id} specifier
7122 is one of the thread identifiers assigned by @value{GDBN}, shown
7123 in the first column of the @samp{info threads} display.
7125 If you do not specify @samp{thread @var{thread-id}} when you set a
7126 breakpoint, the breakpoint applies to @emph{all} threads of your
7129 You can use the @code{thread} qualifier on conditional breakpoints as
7130 well; in this case, place @samp{thread @var{thread-id}} before or
7131 after the breakpoint condition, like this:
7134 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7139 Thread-specific breakpoints are automatically deleted when
7140 @value{GDBN} detects the corresponding thread is no longer in the
7141 thread list. For example:
7145 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7148 There are several ways for a thread to disappear, such as a regular
7149 thread exit, but also when you detach from the process with the
7150 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7151 Process}), or if @value{GDBN} loses the remote connection
7152 (@pxref{Remote Debugging}), etc. Note that with some targets,
7153 @value{GDBN} is only able to detect a thread has exited when the user
7154 explictly asks for the thread list with the @code{info threads}
7157 @node Interrupted System Calls
7158 @subsection Interrupted System Calls
7160 @cindex thread breakpoints and system calls
7161 @cindex system calls and thread breakpoints
7162 @cindex premature return from system calls
7163 There is an unfortunate side effect when using @value{GDBN} to debug
7164 multi-threaded programs. If one thread stops for a
7165 breakpoint, or for some other reason, and another thread is blocked in a
7166 system call, then the system call may return prematurely. This is a
7167 consequence of the interaction between multiple threads and the signals
7168 that @value{GDBN} uses to implement breakpoints and other events that
7171 To handle this problem, your program should check the return value of
7172 each system call and react appropriately. This is good programming
7175 For example, do not write code like this:
7181 The call to @code{sleep} will return early if a different thread stops
7182 at a breakpoint or for some other reason.
7184 Instead, write this:
7189 unslept = sleep (unslept);
7192 A system call is allowed to return early, so the system is still
7193 conforming to its specification. But @value{GDBN} does cause your
7194 multi-threaded program to behave differently than it would without
7197 Also, @value{GDBN} uses internal breakpoints in the thread library to
7198 monitor certain events such as thread creation and thread destruction.
7199 When such an event happens, a system call in another thread may return
7200 prematurely, even though your program does not appear to stop.
7203 @subsection Observer Mode
7205 If you want to build on non-stop mode and observe program behavior
7206 without any chance of disruption by @value{GDBN}, you can set
7207 variables to disable all of the debugger's attempts to modify state,
7208 whether by writing memory, inserting breakpoints, etc. These operate
7209 at a low level, intercepting operations from all commands.
7211 When all of these are set to @code{off}, then @value{GDBN} is said to
7212 be @dfn{observer mode}. As a convenience, the variable
7213 @code{observer} can be set to disable these, plus enable non-stop
7216 Note that @value{GDBN} will not prevent you from making nonsensical
7217 combinations of these settings. For instance, if you have enabled
7218 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7219 then breakpoints that work by writing trap instructions into the code
7220 stream will still not be able to be placed.
7225 @item set observer on
7226 @itemx set observer off
7227 When set to @code{on}, this disables all the permission variables
7228 below (except for @code{insert-fast-tracepoints}), plus enables
7229 non-stop debugging. Setting this to @code{off} switches back to
7230 normal debugging, though remaining in non-stop mode.
7233 Show whether observer mode is on or off.
7235 @kindex may-write-registers
7236 @item set may-write-registers on
7237 @itemx set may-write-registers off
7238 This controls whether @value{GDBN} will attempt to alter the values of
7239 registers, such as with assignment expressions in @code{print}, or the
7240 @code{jump} command. It defaults to @code{on}.
7242 @item show may-write-registers
7243 Show the current permission to write registers.
7245 @kindex may-write-memory
7246 @item set may-write-memory on
7247 @itemx set may-write-memory off
7248 This controls whether @value{GDBN} will attempt to alter the contents
7249 of memory, such as with assignment expressions in @code{print}. It
7250 defaults to @code{on}.
7252 @item show may-write-memory
7253 Show the current permission to write memory.
7255 @kindex may-insert-breakpoints
7256 @item set may-insert-breakpoints on
7257 @itemx set may-insert-breakpoints off
7258 This controls whether @value{GDBN} will attempt to insert breakpoints.
7259 This affects all breakpoints, including internal breakpoints defined
7260 by @value{GDBN}. It defaults to @code{on}.
7262 @item show may-insert-breakpoints
7263 Show the current permission to insert breakpoints.
7265 @kindex may-insert-tracepoints
7266 @item set may-insert-tracepoints on
7267 @itemx set may-insert-tracepoints off
7268 This controls whether @value{GDBN} will attempt to insert (regular)
7269 tracepoints at the beginning of a tracing experiment. It affects only
7270 non-fast tracepoints, fast tracepoints being under the control of
7271 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7273 @item show may-insert-tracepoints
7274 Show the current permission to insert tracepoints.
7276 @kindex may-insert-fast-tracepoints
7277 @item set may-insert-fast-tracepoints on
7278 @itemx set may-insert-fast-tracepoints off
7279 This controls whether @value{GDBN} will attempt to insert fast
7280 tracepoints at the beginning of a tracing experiment. It affects only
7281 fast tracepoints, regular (non-fast) tracepoints being under the
7282 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7284 @item show may-insert-fast-tracepoints
7285 Show the current permission to insert fast tracepoints.
7287 @kindex may-interrupt
7288 @item set may-interrupt on
7289 @itemx set may-interrupt off
7290 This controls whether @value{GDBN} will attempt to interrupt or stop
7291 program execution. When this variable is @code{off}, the
7292 @code{interrupt} command will have no effect, nor will
7293 @kbd{Ctrl-c}. It defaults to @code{on}.
7295 @item show may-interrupt
7296 Show the current permission to interrupt or stop the program.
7300 @node Reverse Execution
7301 @chapter Running programs backward
7302 @cindex reverse execution
7303 @cindex running programs backward
7305 When you are debugging a program, it is not unusual to realize that
7306 you have gone too far, and some event of interest has already happened.
7307 If the target environment supports it, @value{GDBN} can allow you to
7308 ``rewind'' the program by running it backward.
7310 A target environment that supports reverse execution should be able
7311 to ``undo'' the changes in machine state that have taken place as the
7312 program was executing normally. Variables, registers etc.@: should
7313 revert to their previous values. Obviously this requires a great
7314 deal of sophistication on the part of the target environment; not
7315 all target environments can support reverse execution.
7317 When a program is executed in reverse, the instructions that
7318 have most recently been executed are ``un-executed'', in reverse
7319 order. The program counter runs backward, following the previous
7320 thread of execution in reverse. As each instruction is ``un-executed'',
7321 the values of memory and/or registers that were changed by that
7322 instruction are reverted to their previous states. After executing
7323 a piece of source code in reverse, all side effects of that code
7324 should be ``undone'', and all variables should be returned to their
7325 prior values@footnote{
7326 Note that some side effects are easier to undo than others. For instance,
7327 memory and registers are relatively easy, but device I/O is hard. Some
7328 targets may be able undo things like device I/O, and some may not.
7330 The contract between @value{GDBN} and the reverse executing target
7331 requires only that the target do something reasonable when
7332 @value{GDBN} tells it to execute backwards, and then report the
7333 results back to @value{GDBN}. Whatever the target reports back to
7334 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7335 assumes that the memory and registers that the target reports are in a
7336 consistent state, but @value{GDBN} accepts whatever it is given.
7339 On some platforms, @value{GDBN} has built-in support for reverse
7340 execution, activated with the @code{record} or @code{record btrace}
7341 commands. @xref{Process Record and Replay}. Some remote targets,
7342 typically full system emulators, support reverse execution directly
7343 without requiring any special command.
7345 If you are debugging in a target environment that supports
7346 reverse execution, @value{GDBN} provides the following commands.
7349 @kindex reverse-continue
7350 @kindex rc @r{(@code{reverse-continue})}
7351 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7352 @itemx rc @r{[}@var{ignore-count}@r{]}
7353 Beginning at the point where your program last stopped, start executing
7354 in reverse. Reverse execution will stop for breakpoints and synchronous
7355 exceptions (signals), just like normal execution. Behavior of
7356 asynchronous signals depends on the target environment.
7358 @kindex reverse-step
7359 @kindex rs @r{(@code{step})}
7360 @item reverse-step @r{[}@var{count}@r{]}
7361 Run the program backward until control reaches the start of a
7362 different source line; then stop it, and return control to @value{GDBN}.
7364 Like the @code{step} command, @code{reverse-step} will only stop
7365 at the beginning of a source line. It ``un-executes'' the previously
7366 executed source line. If the previous source line included calls to
7367 debuggable functions, @code{reverse-step} will step (backward) into
7368 the called function, stopping at the beginning of the @emph{last}
7369 statement in the called function (typically a return statement).
7371 Also, as with the @code{step} command, if non-debuggable functions are
7372 called, @code{reverse-step} will run thru them backward without stopping.
7374 @kindex reverse-stepi
7375 @kindex rsi @r{(@code{reverse-stepi})}
7376 @item reverse-stepi @r{[}@var{count}@r{]}
7377 Reverse-execute one machine instruction. Note that the instruction
7378 to be reverse-executed is @emph{not} the one pointed to by the program
7379 counter, but the instruction executed prior to that one. For instance,
7380 if the last instruction was a jump, @code{reverse-stepi} will take you
7381 back from the destination of the jump to the jump instruction itself.
7383 @kindex reverse-next
7384 @kindex rn @r{(@code{reverse-next})}
7385 @item reverse-next @r{[}@var{count}@r{]}
7386 Run backward to the beginning of the previous line executed in
7387 the current (innermost) stack frame. If the line contains function
7388 calls, they will be ``un-executed'' without stopping. Starting from
7389 the first line of a function, @code{reverse-next} will take you back
7390 to the caller of that function, @emph{before} the function was called,
7391 just as the normal @code{next} command would take you from the last
7392 line of a function back to its return to its caller
7393 @footnote{Unless the code is too heavily optimized.}.
7395 @kindex reverse-nexti
7396 @kindex rni @r{(@code{reverse-nexti})}
7397 @item reverse-nexti @r{[}@var{count}@r{]}
7398 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7399 in reverse, except that called functions are ``un-executed'' atomically.
7400 That is, if the previously executed instruction was a return from
7401 another function, @code{reverse-nexti} will continue to execute
7402 in reverse until the call to that function (from the current stack
7405 @kindex reverse-finish
7406 @item reverse-finish
7407 Just as the @code{finish} command takes you to the point where the
7408 current function returns, @code{reverse-finish} takes you to the point
7409 where it was called. Instead of ending up at the end of the current
7410 function invocation, you end up at the beginning.
7412 @kindex set exec-direction
7413 @item set exec-direction
7414 Set the direction of target execution.
7415 @item set exec-direction reverse
7416 @cindex execute forward or backward in time
7417 @value{GDBN} will perform all execution commands in reverse, until the
7418 exec-direction mode is changed to ``forward''. Affected commands include
7419 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7420 command cannot be used in reverse mode.
7421 @item set exec-direction forward
7422 @value{GDBN} will perform all execution commands in the normal fashion.
7423 This is the default.
7427 @node Process Record and Replay
7428 @chapter Recording Inferior's Execution and Replaying It
7429 @cindex process record and replay
7430 @cindex recording inferior's execution and replaying it
7432 On some platforms, @value{GDBN} provides a special @dfn{process record
7433 and replay} target that can record a log of the process execution, and
7434 replay it later with both forward and reverse execution commands.
7437 When this target is in use, if the execution log includes the record
7438 for the next instruction, @value{GDBN} will debug in @dfn{replay
7439 mode}. In the replay mode, the inferior does not really execute code
7440 instructions. Instead, all the events that normally happen during
7441 code execution are taken from the execution log. While code is not
7442 really executed in replay mode, the values of registers (including the
7443 program counter register) and the memory of the inferior are still
7444 changed as they normally would. Their contents are taken from the
7448 If the record for the next instruction is not in the execution log,
7449 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7450 inferior executes normally, and @value{GDBN} records the execution log
7453 The process record and replay target supports reverse execution
7454 (@pxref{Reverse Execution}), even if the platform on which the
7455 inferior runs does not. However, the reverse execution is limited in
7456 this case by the range of the instructions recorded in the execution
7457 log. In other words, reverse execution on platforms that don't
7458 support it directly can only be done in the replay mode.
7460 When debugging in the reverse direction, @value{GDBN} will work in
7461 replay mode as long as the execution log includes the record for the
7462 previous instruction; otherwise, it will work in record mode, if the
7463 platform supports reverse execution, or stop if not.
7465 Currently, process record and replay is supported on ARM, Aarch64,
7466 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7467 GNU/Linux. Process record and replay can be used both when native
7468 debugging, and when remote debugging via @code{gdbserver}.
7470 For architecture environments that support process record and replay,
7471 @value{GDBN} provides the following commands:
7474 @kindex target record
7475 @kindex target record-full
7476 @kindex target record-btrace
7479 @kindex record btrace
7480 @kindex record btrace bts
7481 @kindex record btrace pt
7487 @kindex rec btrace bts
7488 @kindex rec btrace pt
7491 @item record @var{method}
7492 This command starts the process record and replay target. The
7493 recording method can be specified as parameter. Without a parameter
7494 the command uses the @code{full} recording method. The following
7495 recording methods are available:
7499 Full record/replay recording using @value{GDBN}'s software record and
7500 replay implementation. This method allows replaying and reverse
7503 @item btrace @var{format}
7504 Hardware-supported instruction recording, supported on Intel
7505 processors. This method does not record data. Further, the data is
7506 collected in a ring buffer so old data will be overwritten when the
7507 buffer is full. It allows limited reverse execution. Variables and
7508 registers are not available during reverse execution. In remote
7509 debugging, recording continues on disconnect. Recorded data can be
7510 inspected after reconnecting. The recording may be stopped using
7513 The recording format can be specified as parameter. Without a parameter
7514 the command chooses the recording format. The following recording
7515 formats are available:
7519 @cindex branch trace store
7520 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7521 this format, the processor stores a from/to record for each executed
7522 branch in the btrace ring buffer.
7525 @cindex Intel Processor Trace
7526 Use the @dfn{Intel Processor Trace} recording format. In this
7527 format, the processor stores the execution trace in a compressed form
7528 that is afterwards decoded by @value{GDBN}.
7530 The trace can be recorded with very low overhead. The compressed
7531 trace format also allows small trace buffers to already contain a big
7532 number of instructions compared to @acronym{BTS}.
7534 Decoding the recorded execution trace, on the other hand, is more
7535 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7536 increased number of instructions to process. You should increase the
7537 buffer-size with care.
7540 Not all recording formats may be available on all processors.
7543 The process record and replay target can only debug a process that is
7544 already running. Therefore, you need first to start the process with
7545 the @kbd{run} or @kbd{start} commands, and then start the recording
7546 with the @kbd{record @var{method}} command.
7548 @cindex displaced stepping, and process record and replay
7549 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7550 will be automatically disabled when process record and replay target
7551 is started. That's because the process record and replay target
7552 doesn't support displaced stepping.
7554 @cindex non-stop mode, and process record and replay
7555 @cindex asynchronous execution, and process record and replay
7556 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7557 the asynchronous execution mode (@pxref{Background Execution}), not
7558 all recording methods are available. The @code{full} recording method
7559 does not support these two modes.
7564 Stop the process record and replay target. When process record and
7565 replay target stops, the entire execution log will be deleted and the
7566 inferior will either be terminated, or will remain in its final state.
7568 When you stop the process record and replay target in record mode (at
7569 the end of the execution log), the inferior will be stopped at the
7570 next instruction that would have been recorded. In other words, if
7571 you record for a while and then stop recording, the inferior process
7572 will be left in the same state as if the recording never happened.
7574 On the other hand, if the process record and replay target is stopped
7575 while in replay mode (that is, not at the end of the execution log,
7576 but at some earlier point), the inferior process will become ``live''
7577 at that earlier state, and it will then be possible to continue the
7578 usual ``live'' debugging of the process from that state.
7580 When the inferior process exits, or @value{GDBN} detaches from it,
7581 process record and replay target will automatically stop itself.
7585 Go to a specific location in the execution log. There are several
7586 ways to specify the location to go to:
7589 @item record goto begin
7590 @itemx record goto start
7591 Go to the beginning of the execution log.
7593 @item record goto end
7594 Go to the end of the execution log.
7596 @item record goto @var{n}
7597 Go to instruction number @var{n} in the execution log.
7601 @item record save @var{filename}
7602 Save the execution log to a file @file{@var{filename}}.
7603 Default filename is @file{gdb_record.@var{process_id}}, where
7604 @var{process_id} is the process ID of the inferior.
7606 This command may not be available for all recording methods.
7608 @kindex record restore
7609 @item record restore @var{filename}
7610 Restore the execution log from a file @file{@var{filename}}.
7611 File must have been created with @code{record save}.
7613 @kindex set record full
7614 @item set record full insn-number-max @var{limit}
7615 @itemx set record full insn-number-max unlimited
7616 Set the limit of instructions to be recorded for the @code{full}
7617 recording method. Default value is 200000.
7619 If @var{limit} is a positive number, then @value{GDBN} will start
7620 deleting instructions from the log once the number of the record
7621 instructions becomes greater than @var{limit}. For every new recorded
7622 instruction, @value{GDBN} will delete the earliest recorded
7623 instruction to keep the number of recorded instructions at the limit.
7624 (Since deleting recorded instructions loses information, @value{GDBN}
7625 lets you control what happens when the limit is reached, by means of
7626 the @code{stop-at-limit} option, described below.)
7628 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7629 delete recorded instructions from the execution log. The number of
7630 recorded instructions is limited only by the available memory.
7632 @kindex show record full
7633 @item show record full insn-number-max
7634 Show the limit of instructions to be recorded with the @code{full}
7637 @item set record full stop-at-limit
7638 Control the behavior of the @code{full} recording method when the
7639 number of recorded instructions reaches the limit. If ON (the
7640 default), @value{GDBN} will stop when the limit is reached for the
7641 first time and ask you whether you want to stop the inferior or
7642 continue running it and recording the execution log. If you decide
7643 to continue recording, each new recorded instruction will cause the
7644 oldest one to be deleted.
7646 If this option is OFF, @value{GDBN} will automatically delete the
7647 oldest record to make room for each new one, without asking.
7649 @item show record full stop-at-limit
7650 Show the current setting of @code{stop-at-limit}.
7652 @item set record full memory-query
7653 Control the behavior when @value{GDBN} is unable to record memory
7654 changes caused by an instruction for the @code{full} recording method.
7655 If ON, @value{GDBN} will query whether to stop the inferior in that
7658 If this option is OFF (the default), @value{GDBN} will automatically
7659 ignore the effect of such instructions on memory. Later, when
7660 @value{GDBN} replays this execution log, it will mark the log of this
7661 instruction as not accessible, and it will not affect the replay
7664 @item show record full memory-query
7665 Show the current setting of @code{memory-query}.
7667 @kindex set record btrace
7668 The @code{btrace} record target does not trace data. As a
7669 convenience, when replaying, @value{GDBN} reads read-only memory off
7670 the live program directly, assuming that the addresses of the
7671 read-only areas don't change. This for example makes it possible to
7672 disassemble code while replaying, but not to print variables.
7673 In some cases, being able to inspect variables might be useful.
7674 You can use the following command for that:
7676 @item set record btrace replay-memory-access
7677 Control the behavior of the @code{btrace} recording method when
7678 accessing memory during replay. If @code{read-only} (the default),
7679 @value{GDBN} will only allow accesses to read-only memory.
7680 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7681 and to read-write memory. Beware that the accessed memory corresponds
7682 to the live target and not necessarily to the current replay
7685 @item set record btrace cpu @var{identifier}
7686 Set the processor to be used for enabling workarounds for processor
7687 errata when decoding the trace.
7689 Processor errata are defects in processor operation, caused by its
7690 design or manufacture. They can cause a trace not to match the
7691 specification. This, in turn, may cause trace decode to fail.
7692 @value{GDBN} can detect erroneous trace packets and correct them, thus
7693 avoiding the decoding failures. These corrections are known as
7694 @dfn{errata workarounds}, and are enabled based on the processor on
7695 which the trace was recorded.
7697 By default, @value{GDBN} attempts to detect the processor
7698 automatically, and apply the necessary workarounds for it. However,
7699 you may need to specify the processor if @value{GDBN} does not yet
7700 support it. This command allows you to do that, and also allows to
7701 disable the workarounds.
7703 The argument @var{identifier} identifies the @sc{cpu} and is of the
7704 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7705 there are two special identifiers, @code{none} and @code{auto}
7708 The following vendor identifiers and corresponding processor
7709 identifiers are currently supported:
7711 @multitable @columnfractions .1 .9
7714 @tab @var{family}/@var{model}[/@var{stepping}]
7718 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7719 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7721 If @var{identifier} is @code{auto}, enable errata workarounds for the
7722 processor on which the trace was recorded. If @var{identifier} is
7723 @code{none}, errata workarounds are disabled.
7725 For example, when using an old @value{GDBN} on a new system, decode
7726 may fail because @value{GDBN} does not support the new processor. It
7727 often suffices to specify an older processor that @value{GDBN}
7732 Active record target: record-btrace
7733 Recording format: Intel Processor Trace.
7735 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7736 (gdb) set record btrace cpu intel:6/158
7738 Active record target: record-btrace
7739 Recording format: Intel Processor Trace.
7741 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7744 @kindex show record btrace
7745 @item show record btrace replay-memory-access
7746 Show the current setting of @code{replay-memory-access}.
7748 @item show record btrace cpu
7749 Show the processor to be used for enabling trace decode errata
7752 @kindex set record btrace bts
7753 @item set record btrace bts buffer-size @var{size}
7754 @itemx set record btrace bts buffer-size unlimited
7755 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7756 format. Default is 64KB.
7758 If @var{size} is a positive number, then @value{GDBN} will try to
7759 allocate a buffer of at least @var{size} bytes for each new thread
7760 that uses the btrace recording method and the @acronym{BTS} format.
7761 The actually obtained buffer size may differ from the requested
7762 @var{size}. Use the @code{info record} command to see the actual
7763 buffer size for each thread that uses the btrace recording method and
7764 the @acronym{BTS} format.
7766 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7767 allocate a buffer of 4MB.
7769 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7770 also need longer to process the branch trace data before it can be used.
7772 @item show record btrace bts buffer-size @var{size}
7773 Show the current setting of the requested ring buffer size for branch
7774 tracing in @acronym{BTS} format.
7776 @kindex set record btrace pt
7777 @item set record btrace pt buffer-size @var{size}
7778 @itemx set record btrace pt buffer-size unlimited
7779 Set the requested ring buffer size for branch tracing in Intel
7780 Processor Trace format. Default is 16KB.
7782 If @var{size} is a positive number, then @value{GDBN} will try to
7783 allocate a buffer of at least @var{size} bytes for each new thread
7784 that uses the btrace recording method and the Intel Processor Trace
7785 format. The actually obtained buffer size may differ from the
7786 requested @var{size}. Use the @code{info record} command to see the
7787 actual buffer size for each thread.
7789 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7790 allocate a buffer of 4MB.
7792 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7793 also need longer to process the branch trace data before it can be used.
7795 @item show record btrace pt buffer-size @var{size}
7796 Show the current setting of the requested ring buffer size for branch
7797 tracing in Intel Processor Trace format.
7801 Show various statistics about the recording depending on the recording
7806 For the @code{full} recording method, it shows the state of process
7807 record and its in-memory execution log buffer, including:
7811 Whether in record mode or replay mode.
7813 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7815 Highest recorded instruction number.
7817 Current instruction about to be replayed (if in replay mode).
7819 Number of instructions contained in the execution log.
7821 Maximum number of instructions that may be contained in the execution log.
7825 For the @code{btrace} recording method, it shows:
7831 Number of instructions that have been recorded.
7833 Number of blocks of sequential control-flow formed by the recorded
7836 Whether in record mode or replay mode.
7839 For the @code{bts} recording format, it also shows:
7842 Size of the perf ring buffer.
7845 For the @code{pt} recording format, it also shows:
7848 Size of the perf ring buffer.
7852 @kindex record delete
7855 When record target runs in replay mode (``in the past''), delete the
7856 subsequent execution log and begin to record a new execution log starting
7857 from the current address. This means you will abandon the previously
7858 recorded ``future'' and begin recording a new ``future''.
7860 @kindex record instruction-history
7861 @kindex rec instruction-history
7862 @item record instruction-history
7863 Disassembles instructions from the recorded execution log. By
7864 default, ten instructions are disassembled. This can be changed using
7865 the @code{set record instruction-history-size} command. Instructions
7866 are printed in execution order.
7868 It can also print mixed source+disassembly if you specify the the
7869 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7870 as well as in symbolic form by specifying the @code{/r} modifier.
7872 The current position marker is printed for the instruction at the
7873 current program counter value. This instruction can appear multiple
7874 times in the trace and the current position marker will be printed
7875 every time. To omit the current position marker, specify the
7878 To better align the printed instructions when the trace contains
7879 instructions from more than one function, the function name may be
7880 omitted by specifying the @code{/f} modifier.
7882 Speculatively executed instructions are prefixed with @samp{?}. This
7883 feature is not available for all recording formats.
7885 There are several ways to specify what part of the execution log to
7889 @item record instruction-history @var{insn}
7890 Disassembles ten instructions starting from instruction number
7893 @item record instruction-history @var{insn}, +/-@var{n}
7894 Disassembles @var{n} instructions around instruction number
7895 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7896 @var{n} instructions after instruction number @var{insn}. If
7897 @var{n} is preceded with @code{-}, disassembles @var{n}
7898 instructions before instruction number @var{insn}.
7900 @item record instruction-history
7901 Disassembles ten more instructions after the last disassembly.
7903 @item record instruction-history -
7904 Disassembles ten more instructions before the last disassembly.
7906 @item record instruction-history @var{begin}, @var{end}
7907 Disassembles instructions beginning with instruction number
7908 @var{begin} until instruction number @var{end}. The instruction
7909 number @var{end} is included.
7912 This command may not be available for all recording methods.
7915 @item set record instruction-history-size @var{size}
7916 @itemx set record instruction-history-size unlimited
7917 Define how many instructions to disassemble in the @code{record
7918 instruction-history} command. The default value is 10.
7919 A @var{size} of @code{unlimited} means unlimited instructions.
7922 @item show record instruction-history-size
7923 Show how many instructions to disassemble in the @code{record
7924 instruction-history} command.
7926 @kindex record function-call-history
7927 @kindex rec function-call-history
7928 @item record function-call-history
7929 Prints the execution history at function granularity. For each sequence
7930 of instructions that belong to the same function, it prints the name of
7931 that function, the source lines for this instruction sequence (if the
7932 @code{/l} modifier is specified), and the instructions numbers that form
7933 the sequence (if the @code{/i} modifier is specified). The function names
7934 are indented to reflect the call stack depth if the @code{/c} modifier is
7935 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7939 (@value{GDBP}) @b{list 1, 10}
7950 (@value{GDBP}) @b{record function-call-history /ilc}
7951 1 bar inst 1,4 at foo.c:6,8
7952 2 foo inst 5,10 at foo.c:2,3
7953 3 bar inst 11,13 at foo.c:9,10
7956 By default, ten functions are printed. This can be changed using the
7957 @code{set record function-call-history-size} command. Functions are
7958 printed in execution order. There are several ways to specify what
7962 @item record function-call-history @var{func}
7963 Prints ten functions starting from function number @var{func}.
7965 @item record function-call-history @var{func}, +/-@var{n}
7966 Prints @var{n} functions around function number @var{func}. If
7967 @var{n} is preceded with @code{+}, prints @var{n} functions after
7968 function number @var{func}. If @var{n} is preceded with @code{-},
7969 prints @var{n} functions before function number @var{func}.
7971 @item record function-call-history
7972 Prints ten more functions after the last ten-function print.
7974 @item record function-call-history -
7975 Prints ten more functions before the last ten-function print.
7977 @item record function-call-history @var{begin}, @var{end}
7978 Prints functions beginning with function number @var{begin} until
7979 function number @var{end}. The function number @var{end} is included.
7982 This command may not be available for all recording methods.
7984 @item set record function-call-history-size @var{size}
7985 @itemx set record function-call-history-size unlimited
7986 Define how many functions to print in the
7987 @code{record function-call-history} command. The default value is 10.
7988 A size of @code{unlimited} means unlimited functions.
7990 @item show record function-call-history-size
7991 Show how many functions to print in the
7992 @code{record function-call-history} command.
7997 @chapter Examining the Stack
7999 When your program has stopped, the first thing you need to know is where it
8000 stopped and how it got there.
8003 Each time your program performs a function call, information about the call
8005 That information includes the location of the call in your program,
8006 the arguments of the call,
8007 and the local variables of the function being called.
8008 The information is saved in a block of data called a @dfn{stack frame}.
8009 The stack frames are allocated in a region of memory called the @dfn{call
8012 When your program stops, the @value{GDBN} commands for examining the
8013 stack allow you to see all of this information.
8015 @cindex selected frame
8016 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8017 @value{GDBN} commands refer implicitly to the selected frame. In
8018 particular, whenever you ask @value{GDBN} for the value of a variable in
8019 your program, the value is found in the selected frame. There are
8020 special @value{GDBN} commands to select whichever frame you are
8021 interested in. @xref{Selection, ,Selecting a Frame}.
8023 When your program stops, @value{GDBN} automatically selects the
8024 currently executing frame and describes it briefly, similar to the
8025 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8028 * Frames:: Stack frames
8029 * Backtrace:: Backtraces
8030 * Selection:: Selecting a frame
8031 * Frame Info:: Information on a frame
8032 * Frame Apply:: Applying a command to several frames
8033 * Frame Filter Management:: Managing frame filters
8038 @section Stack Frames
8040 @cindex frame, definition
8042 The call stack is divided up into contiguous pieces called @dfn{stack
8043 frames}, or @dfn{frames} for short; each frame is the data associated
8044 with one call to one function. The frame contains the arguments given
8045 to the function, the function's local variables, and the address at
8046 which the function is executing.
8048 @cindex initial frame
8049 @cindex outermost frame
8050 @cindex innermost frame
8051 When your program is started, the stack has only one frame, that of the
8052 function @code{main}. This is called the @dfn{initial} frame or the
8053 @dfn{outermost} frame. Each time a function is called, a new frame is
8054 made. Each time a function returns, the frame for that function invocation
8055 is eliminated. If a function is recursive, there can be many frames for
8056 the same function. The frame for the function in which execution is
8057 actually occurring is called the @dfn{innermost} frame. This is the most
8058 recently created of all the stack frames that still exist.
8060 @cindex frame pointer
8061 Inside your program, stack frames are identified by their addresses. A
8062 stack frame consists of many bytes, each of which has its own address; each
8063 kind of computer has a convention for choosing one byte whose
8064 address serves as the address of the frame. Usually this address is kept
8065 in a register called the @dfn{frame pointer register}
8066 (@pxref{Registers, $fp}) while execution is going on in that frame.
8069 @cindex frame number
8070 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8071 number that is zero for the innermost frame, one for the frame that
8072 called it, and so on upward. These level numbers give you a way of
8073 designating stack frames in @value{GDBN} commands. The terms
8074 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8075 describe this number.
8077 @c The -fomit-frame-pointer below perennially causes hbox overflow
8078 @c underflow problems.
8079 @cindex frameless execution
8080 Some compilers provide a way to compile functions so that they operate
8081 without stack frames. (For example, the @value{NGCC} option
8083 @samp{-fomit-frame-pointer}
8085 generates functions without a frame.)
8086 This is occasionally done with heavily used library functions to save
8087 the frame setup time. @value{GDBN} has limited facilities for dealing
8088 with these function invocations. If the innermost function invocation
8089 has no stack frame, @value{GDBN} nevertheless regards it as though
8090 it had a separate frame, which is numbered zero as usual, allowing
8091 correct tracing of the function call chain. However, @value{GDBN} has
8092 no provision for frameless functions elsewhere in the stack.
8098 @cindex call stack traces
8099 A backtrace is a summary of how your program got where it is. It shows one
8100 line per frame, for many frames, starting with the currently executing
8101 frame (frame zero), followed by its caller (frame one), and on up the
8104 @anchor{backtrace-command}
8106 @kindex bt @r{(@code{backtrace})}
8107 To print a backtrace of the entire stack, use the @code{backtrace}
8108 command, or its alias @code{bt}. This command will print one line per
8109 frame for frames in the stack. By default, all stack frames are
8110 printed. You can stop the backtrace at any time by typing the system
8111 interrupt character, normally @kbd{Ctrl-c}.
8114 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8115 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8116 Print the backtrace of the entire stack.
8118 The optional @var{count} can be one of the following:
8123 Print only the innermost @var{n} frames, where @var{n} is a positive
8128 Print only the outermost @var{n} frames, where @var{n} is a positive
8136 Print the values of the local variables also. This can be combined
8137 with the optional @var{count} to limit the number of frames shown.
8140 Do not run Python frame filters on this backtrace. @xref{Frame
8141 Filter API}, for more information. Additionally use @ref{disable
8142 frame-filter all} to turn off all frame filters. This is only
8143 relevant when @value{GDBN} has been configured with @code{Python}
8147 A Python frame filter might decide to ``elide'' some frames. Normally
8148 such elided frames are still printed, but they are indented relative
8149 to the filtered frames that cause them to be elided. The @code{-hide}
8150 option causes elided frames to not be printed at all.
8153 The @code{backtrace} command also supports a number of options that
8154 allow overriding relevant global print settings as set by @code{set
8155 backtrace} and @code{set print} subcommands:
8158 @item -past-main [@code{on}|@code{off}]
8159 Set whether backtraces should continue past @code{main}. Related setting:
8160 @ref{set backtrace past-main}.
8162 @item -past-entry [@code{on}|@code{off}]
8163 Set whether backtraces should continue past the entry point of a program.
8164 Related setting: @ref{set backtrace past-entry}.
8166 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8167 Set printing of function arguments at function entry.
8168 Related setting: @ref{set print entry-values}.
8170 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8171 Set printing of non-scalar frame arguments.
8172 Related setting: @ref{set print frame-arguments}.
8174 @item -raw-frame-arguments [@code{on}|@code{off}]
8175 Set whether to print frame arguments in raw form.
8176 Related setting: @ref{set print raw-frame-arguments}.
8178 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8179 Set printing of frame information.
8180 Related setting: @ref{set print frame-info}.
8183 The optional @var{qualifier} is maintained for backward compatibility.
8184 It can be one of the following:
8188 Equivalent to the @code{-full} option.
8191 Equivalent to the @code{-no-filters} option.
8194 Equivalent to the @code{-hide} option.
8201 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8202 are additional aliases for @code{backtrace}.
8204 @cindex multiple threads, backtrace
8205 In a multi-threaded program, @value{GDBN} by default shows the
8206 backtrace only for the current thread. To display the backtrace for
8207 several or all of the threads, use the command @code{thread apply}
8208 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8209 apply all backtrace}, @value{GDBN} will display the backtrace for all
8210 the threads; this is handy when you debug a core dump of a
8211 multi-threaded program.
8213 Each line in the backtrace shows the frame number and the function name.
8214 The program counter value is also shown---unless you use @code{set
8215 print address off}. The backtrace also shows the source file name and
8216 line number, as well as the arguments to the function. The program
8217 counter value is omitted if it is at the beginning of the code for that
8220 Here is an example of a backtrace. It was made with the command
8221 @samp{bt 3}, so it shows the innermost three frames.
8225 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8227 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8228 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8230 (More stack frames follow...)
8235 The display for frame zero does not begin with a program counter
8236 value, indicating that your program has stopped at the beginning of the
8237 code for line @code{993} of @code{builtin.c}.
8240 The value of parameter @code{data} in frame 1 has been replaced by
8241 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8242 only if it is a scalar (integer, pointer, enumeration, etc). See command
8243 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8244 on how to configure the way function parameter values are printed.
8245 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8246 what frame information is printed.
8248 @cindex optimized out, in backtrace
8249 @cindex function call arguments, optimized out
8250 If your program was compiled with optimizations, some compilers will
8251 optimize away arguments passed to functions if those arguments are
8252 never used after the call. Such optimizations generate code that
8253 passes arguments through registers, but doesn't store those arguments
8254 in the stack frame. @value{GDBN} has no way of displaying such
8255 arguments in stack frames other than the innermost one. Here's what
8256 such a backtrace might look like:
8260 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8262 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8263 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8265 (More stack frames follow...)
8270 The values of arguments that were not saved in their stack frames are
8271 shown as @samp{<optimized out>}.
8273 If you need to display the values of such optimized-out arguments,
8274 either deduce that from other variables whose values depend on the one
8275 you are interested in, or recompile without optimizations.
8277 @cindex backtrace beyond @code{main} function
8278 @cindex program entry point
8279 @cindex startup code, and backtrace
8280 Most programs have a standard user entry point---a place where system
8281 libraries and startup code transition into user code. For C this is
8282 @code{main}@footnote{
8283 Note that embedded programs (the so-called ``free-standing''
8284 environment) are not required to have a @code{main} function as the
8285 entry point. They could even have multiple entry points.}.
8286 When @value{GDBN} finds the entry function in a backtrace
8287 it will terminate the backtrace, to avoid tracing into highly
8288 system-specific (and generally uninteresting) code.
8290 If you need to examine the startup code, or limit the number of levels
8291 in a backtrace, you can change this behavior:
8294 @item set backtrace past-main
8295 @itemx set backtrace past-main on
8296 @anchor{set backtrace past-main}
8297 @kindex set backtrace
8298 Backtraces will continue past the user entry point.
8300 @item set backtrace past-main off
8301 Backtraces will stop when they encounter the user entry point. This is the
8304 @item show backtrace past-main
8305 @kindex show backtrace
8306 Display the current user entry point backtrace policy.
8308 @item set backtrace past-entry
8309 @itemx set backtrace past-entry on
8310 @anchor{set backtrace past-entry}
8311 Backtraces will continue past the internal entry point of an application.
8312 This entry point is encoded by the linker when the application is built,
8313 and is likely before the user entry point @code{main} (or equivalent) is called.
8315 @item set backtrace past-entry off
8316 Backtraces will stop when they encounter the internal entry point of an
8317 application. This is the default.
8319 @item show backtrace past-entry
8320 Display the current internal entry point backtrace policy.
8322 @item set backtrace limit @var{n}
8323 @itemx set backtrace limit 0
8324 @itemx set backtrace limit unlimited
8325 @anchor{set backtrace limit}
8326 @cindex backtrace limit
8327 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8328 or zero means unlimited levels.
8330 @item show backtrace limit
8331 Display the current limit on backtrace levels.
8334 You can control how file names are displayed.
8337 @item set filename-display
8338 @itemx set filename-display relative
8339 @cindex filename-display
8340 Display file names relative to the compilation directory. This is the default.
8342 @item set filename-display basename
8343 Display only basename of a filename.
8345 @item set filename-display absolute
8346 Display an absolute filename.
8348 @item show filename-display
8349 Show the current way to display filenames.
8353 @section Selecting a Frame
8355 Most commands for examining the stack and other data in your program work on
8356 whichever stack frame is selected at the moment. Here are the commands for
8357 selecting a stack frame; all of them finish by printing a brief description
8358 of the stack frame just selected.
8361 @kindex frame@r{, selecting}
8362 @kindex f @r{(@code{frame})}
8363 @item frame @r{[} @var{frame-selection-spec} @r{]}
8364 @item f @r{[} @var{frame-selection-spec} @r{]}
8365 The @command{frame} command allows different stack frames to be
8366 selected. The @var{frame-selection-spec} can be any of the following:
8371 @item level @var{num}
8372 Select frame level @var{num}. Recall that frame zero is the innermost
8373 (currently executing) frame, frame one is the frame that called the
8374 innermost one, and so on. The highest level frame is usually the one
8377 As this is the most common method of navigating the frame stack, the
8378 string @command{level} can be omitted. For example, the following two
8379 commands are equivalent:
8382 (@value{GDBP}) frame 3
8383 (@value{GDBP}) frame level 3
8386 @kindex frame address
8387 @item address @var{stack-address}
8388 Select the frame with stack address @var{stack-address}. The
8389 @var{stack-address} for a frame can be seen in the output of
8390 @command{info frame}, for example:
8394 Stack level 1, frame at 0x7fffffffda30:
8395 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8396 tail call frame, caller of frame at 0x7fffffffda30
8397 source language c++.
8398 Arglist at unknown address.
8399 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8402 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8403 indicated by the line:
8406 Stack level 1, frame at 0x7fffffffda30:
8409 @kindex frame function
8410 @item function @var{function-name}
8411 Select the stack frame for function @var{function-name}. If there are
8412 multiple stack frames for function @var{function-name} then the inner
8413 most stack frame is selected.
8416 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8417 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8418 viewed has stack address @var{stack-addr}, and optionally, a program
8419 counter address of @var{pc-addr}.
8421 This is useful mainly if the chaining of stack frames has been
8422 damaged by a bug, making it impossible for @value{GDBN} to assign
8423 numbers properly to all frames. In addition, this can be useful
8424 when your program has multiple stacks and switches between them.
8426 When viewing a frame outside the current backtrace using
8427 @command{frame view} then you can always return to the original
8428 stack using one of the previous stack frame selection instructions,
8429 for example @command{frame level 0}.
8435 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8436 numbers @var{n}, this advances toward the outermost frame, to higher
8437 frame numbers, to frames that have existed longer.
8440 @kindex do @r{(@code{down})}
8442 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8443 positive numbers @var{n}, this advances toward the innermost frame, to
8444 lower frame numbers, to frames that were created more recently.
8445 You may abbreviate @code{down} as @code{do}.
8448 All of these commands end by printing two lines of output describing the
8449 frame. The first line shows the frame number, the function name, the
8450 arguments, and the source file and line number of execution in that
8451 frame. The second line shows the text of that source line.
8459 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8461 10 read_input_file (argv[i]);
8465 After such a printout, the @code{list} command with no arguments
8466 prints ten lines centered on the point of execution in the frame.
8467 You can also edit the program at the point of execution with your favorite
8468 editing program by typing @code{edit}.
8469 @xref{List, ,Printing Source Lines},
8473 @kindex select-frame
8474 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8475 The @code{select-frame} command is a variant of @code{frame} that does
8476 not display the new frame after selecting it. This command is
8477 intended primarily for use in @value{GDBN} command scripts, where the
8478 output might be unnecessary and distracting. The
8479 @var{frame-selection-spec} is as for the @command{frame} command
8480 described in @ref{Selection, ,Selecting a Frame}.
8482 @kindex down-silently
8484 @item up-silently @var{n}
8485 @itemx down-silently @var{n}
8486 These two commands are variants of @code{up} and @code{down},
8487 respectively; they differ in that they do their work silently, without
8488 causing display of the new frame. They are intended primarily for use
8489 in @value{GDBN} command scripts, where the output might be unnecessary and
8494 @section Information About a Frame
8496 There are several other commands to print information about the selected
8502 When used without any argument, this command does not change which
8503 frame is selected, but prints a brief description of the currently
8504 selected stack frame. It can be abbreviated @code{f}. With an
8505 argument, this command is used to select a stack frame.
8506 @xref{Selection, ,Selecting a Frame}.
8509 @kindex info f @r{(@code{info frame})}
8512 This command prints a verbose description of the selected stack frame,
8517 the address of the frame
8519 the address of the next frame down (called by this frame)
8521 the address of the next frame up (caller of this frame)
8523 the language in which the source code corresponding to this frame is written
8525 the address of the frame's arguments
8527 the address of the frame's local variables
8529 the program counter saved in it (the address of execution in the caller frame)
8531 which registers were saved in the frame
8534 @noindent The verbose description is useful when
8535 something has gone wrong that has made the stack format fail to fit
8536 the usual conventions.
8538 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8539 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8540 Print a verbose description of the frame selected by
8541 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8542 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8543 a Frame}). The selected frame remains unchanged by this command.
8546 @item info args [-q]
8547 Print the arguments of the selected frame, each on a separate line.
8549 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8550 printing header information and messages explaining why no argument
8553 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8554 Like @kbd{info args}, but only print the arguments selected
8555 with the provided regexp(s).
8557 If @var{regexp} is provided, print only the arguments whose names
8558 match the regular expression @var{regexp}.
8560 If @var{type_regexp} is provided, print only the arguments whose
8561 types, as printed by the @code{whatis} command, match
8562 the regular expression @var{type_regexp}.
8563 If @var{type_regexp} contains space(s), it should be enclosed in
8564 quote characters. If needed, use backslash to escape the meaning
8565 of special characters or quotes.
8567 If both @var{regexp} and @var{type_regexp} are provided, an argument
8568 is printed only if its name matches @var{regexp} and its type matches
8571 @item info locals [-q]
8573 Print the local variables of the selected frame, each on a separate
8574 line. These are all variables (declared either static or automatic)
8575 accessible at the point of execution of the selected frame.
8577 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8578 printing header information and messages explaining why no local variables
8581 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8582 Like @kbd{info locals}, but only print the local variables selected
8583 with the provided regexp(s).
8585 If @var{regexp} is provided, print only the local variables whose names
8586 match the regular expression @var{regexp}.
8588 If @var{type_regexp} is provided, print only the local variables whose
8589 types, as printed by the @code{whatis} command, match
8590 the regular expression @var{type_regexp}.
8591 If @var{type_regexp} contains space(s), it should be enclosed in
8592 quote characters. If needed, use backslash to escape the meaning
8593 of special characters or quotes.
8595 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8596 is printed only if its name matches @var{regexp} and its type matches
8599 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8600 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8601 For example, your program might use Resource Acquisition Is
8602 Initialization types (RAII) such as @code{lock_something_t}: each
8603 local variable of type @code{lock_something_t} automatically places a
8604 lock that is destroyed when the variable goes out of scope. You can
8605 then list all acquired locks in your program by doing
8607 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8610 or the equivalent shorter form
8612 tfaas i lo -q -t lock_something_t
8618 @section Applying a Command to Several Frames.
8620 @cindex apply command to several frames
8622 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8623 The @code{frame apply} command allows you to apply the named
8624 @var{command} to one or more frames.
8628 Specify @code{all} to apply @var{command} to all frames.
8631 Use @var{count} to apply @var{command} to the innermost @var{count}
8632 frames, where @var{count} is a positive number.
8635 Use @var{-count} to apply @var{command} to the outermost @var{count}
8636 frames, where @var{count} is a positive number.
8639 Use @code{level} to apply @var{command} to the set of frames identified
8640 by the @var{level} list. @var{level} is a frame level or a range of frame
8641 levels as @var{level1}-@var{level2}. The frame level is the number shown
8642 in the first field of the @samp{backtrace} command output.
8643 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8644 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8648 Note that the frames on which @code{frame apply} applies a command are
8649 also influenced by the @code{set backtrace} settings such as @code{set
8650 backtrace past-main} and @code{set backtrace limit N}.
8651 @xref{Backtrace,,Backtraces}.
8653 The @code{frame apply} command also supports a number of options that
8654 allow overriding relevant @code{set backtrace} settings:
8657 @item -past-main [@code{on}|@code{off}]
8658 Whether backtraces should continue past @code{main}.
8659 Related setting: @ref{set backtrace past-main}.
8661 @item -past-entry [@code{on}|@code{off}]
8662 Whether backtraces should continue past the entry point of a program.
8663 Related setting: @ref{set backtrace past-entry}.
8666 By default, @value{GDBN} displays some frame information before the
8667 output produced by @var{command}, and an error raised during the
8668 execution of a @var{command} will abort @code{frame apply}. The
8669 following options can be used to fine-tune these behaviors:
8673 The flag @code{-c}, which stands for @samp{continue}, causes any
8674 errors in @var{command} to be displayed, and the execution of
8675 @code{frame apply} then continues.
8677 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8678 or empty output produced by a @var{command} to be silently ignored.
8679 That is, the execution continues, but the frame information and errors
8682 The flag @code{-q} (@samp{quiet}) disables printing the frame
8686 The following example shows how the flags @code{-c} and @code{-s} are
8687 working when applying the command @code{p j} to all frames, where
8688 variable @code{j} can only be successfully printed in the outermost
8689 @code{#1 main} frame.
8693 (gdb) frame apply all p j
8694 #0 some_function (i=5) at fun.c:4
8695 No symbol "j" in current context.
8696 (gdb) frame apply all -c p j
8697 #0 some_function (i=5) at fun.c:4
8698 No symbol "j" in current context.
8699 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8701 (gdb) frame apply all -s p j
8702 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8708 By default, @samp{frame apply}, prints the frame location
8709 information before the command output:
8713 (gdb) frame apply all p $sp
8714 #0 some_function (i=5) at fun.c:4
8715 $4 = (void *) 0xffffd1e0
8716 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8717 $5 = (void *) 0xffffd1f0
8722 If the flag @code{-q} is given, no frame information is printed:
8725 (gdb) frame apply all -q p $sp
8726 $12 = (void *) 0xffffd1e0
8727 $13 = (void *) 0xffffd1f0
8737 @cindex apply a command to all frames (ignoring errors and empty output)
8738 @item faas @var{command}
8739 Shortcut for @code{frame apply all -s @var{command}}.
8740 Applies @var{command} on all frames, ignoring errors and empty output.
8742 It can for example be used to print a local variable or a function
8743 argument without knowing the frame where this variable or argument
8746 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8749 The @code{faas} command accepts the same options as the @code{frame
8750 apply} command. @xref{Frame Apply,,frame apply}.
8752 Note that the command @code{tfaas @var{command}} applies @var{command}
8753 on all frames of all threads. See @xref{Threads,,Threads}.
8757 @node Frame Filter Management
8758 @section Management of Frame Filters.
8759 @cindex managing frame filters
8761 Frame filters are Python based utilities to manage and decorate the
8762 output of frames. @xref{Frame Filter API}, for further information.
8764 Managing frame filters is performed by several commands available
8765 within @value{GDBN}, detailed here.
8768 @kindex info frame-filter
8769 @item info frame-filter
8770 Print a list of installed frame filters from all dictionaries, showing
8771 their name, priority and enabled status.
8773 @kindex disable frame-filter
8774 @anchor{disable frame-filter all}
8775 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8776 Disable a frame filter in the dictionary matching
8777 @var{filter-dictionary} and @var{filter-name}. The
8778 @var{filter-dictionary} may be @code{all}, @code{global},
8779 @code{progspace}, or the name of the object file where the frame filter
8780 dictionary resides. When @code{all} is specified, all frame filters
8781 across all dictionaries are disabled. The @var{filter-name} is the name
8782 of the frame filter and is used when @code{all} is not the option for
8783 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8784 may be enabled again later.
8786 @kindex enable frame-filter
8787 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8788 Enable a frame filter in the dictionary matching
8789 @var{filter-dictionary} and @var{filter-name}. The
8790 @var{filter-dictionary} may be @code{all}, @code{global},
8791 @code{progspace} or the name of the object file where the frame filter
8792 dictionary resides. When @code{all} is specified, all frame filters across
8793 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8794 filter and is used when @code{all} is not the option for
8795 @var{filter-dictionary}.
8800 (gdb) info frame-filter
8802 global frame-filters:
8803 Priority Enabled Name
8804 1000 No PrimaryFunctionFilter
8807 progspace /build/test frame-filters:
8808 Priority Enabled Name
8809 100 Yes ProgspaceFilter
8811 objfile /build/test frame-filters:
8812 Priority Enabled Name
8813 999 Yes BuildProgramFilter
8815 (gdb) disable frame-filter /build/test BuildProgramFilter
8816 (gdb) info frame-filter
8818 global frame-filters:
8819 Priority Enabled Name
8820 1000 No PrimaryFunctionFilter
8823 progspace /build/test frame-filters:
8824 Priority Enabled Name
8825 100 Yes ProgspaceFilter
8827 objfile /build/test frame-filters:
8828 Priority Enabled Name
8829 999 No BuildProgramFilter
8831 (gdb) enable frame-filter global PrimaryFunctionFilter
8832 (gdb) info frame-filter
8834 global frame-filters:
8835 Priority Enabled Name
8836 1000 Yes PrimaryFunctionFilter
8839 progspace /build/test frame-filters:
8840 Priority Enabled Name
8841 100 Yes ProgspaceFilter
8843 objfile /build/test frame-filters:
8844 Priority Enabled Name
8845 999 No BuildProgramFilter
8848 @kindex set frame-filter priority
8849 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8850 Set the @var{priority} of a frame filter in the dictionary matching
8851 @var{filter-dictionary}, and the frame filter name matching
8852 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8853 @code{progspace} or the name of the object file where the frame filter
8854 dictionary resides. The @var{priority} is an integer.
8856 @kindex show frame-filter priority
8857 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8858 Show the @var{priority} of a frame filter in the dictionary matching
8859 @var{filter-dictionary}, and the frame filter name matching
8860 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8861 @code{progspace} or the name of the object file where the frame filter
8867 (gdb) info frame-filter
8869 global frame-filters:
8870 Priority Enabled Name
8871 1000 Yes PrimaryFunctionFilter
8874 progspace /build/test frame-filters:
8875 Priority Enabled Name
8876 100 Yes ProgspaceFilter
8878 objfile /build/test frame-filters:
8879 Priority Enabled Name
8880 999 No BuildProgramFilter
8882 (gdb) set frame-filter priority global Reverse 50
8883 (gdb) info frame-filter
8885 global frame-filters:
8886 Priority Enabled Name
8887 1000 Yes PrimaryFunctionFilter
8890 progspace /build/test frame-filters:
8891 Priority Enabled Name
8892 100 Yes ProgspaceFilter
8894 objfile /build/test frame-filters:
8895 Priority Enabled Name
8896 999 No BuildProgramFilter
8901 @chapter Examining Source Files
8903 @value{GDBN} can print parts of your program's source, since the debugging
8904 information recorded in the program tells @value{GDBN} what source files were
8905 used to build it. When your program stops, @value{GDBN} spontaneously prints
8906 the line where it stopped. Likewise, when you select a stack frame
8907 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8908 execution in that frame has stopped. You can print other portions of
8909 source files by explicit command.
8911 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8912 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8913 @value{GDBN} under @sc{gnu} Emacs}.
8916 * List:: Printing source lines
8917 * Specify Location:: How to specify code locations
8918 * Edit:: Editing source files
8919 * Search:: Searching source files
8920 * Source Path:: Specifying source directories
8921 * Machine Code:: Source and machine code
8925 @section Printing Source Lines
8928 @kindex l @r{(@code{list})}
8929 To print lines from a source file, use the @code{list} command
8930 (abbreviated @code{l}). By default, ten lines are printed.
8931 There are several ways to specify what part of the file you want to
8932 print; see @ref{Specify Location}, for the full list.
8934 Here are the forms of the @code{list} command most commonly used:
8937 @item list @var{linenum}
8938 Print lines centered around line number @var{linenum} in the
8939 current source file.
8941 @item list @var{function}
8942 Print lines centered around the beginning of function
8946 Print more lines. If the last lines printed were printed with a
8947 @code{list} command, this prints lines following the last lines
8948 printed; however, if the last line printed was a solitary line printed
8949 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8950 Stack}), this prints lines centered around that line.
8953 Print lines just before the lines last printed.
8956 @cindex @code{list}, how many lines to display
8957 By default, @value{GDBN} prints ten source lines with any of these forms of
8958 the @code{list} command. You can change this using @code{set listsize}:
8961 @kindex set listsize
8962 @item set listsize @var{count}
8963 @itemx set listsize unlimited
8964 Make the @code{list} command display @var{count} source lines (unless
8965 the @code{list} argument explicitly specifies some other number).
8966 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8968 @kindex show listsize
8970 Display the number of lines that @code{list} prints.
8973 Repeating a @code{list} command with @key{RET} discards the argument,
8974 so it is equivalent to typing just @code{list}. This is more useful
8975 than listing the same lines again. An exception is made for an
8976 argument of @samp{-}; that argument is preserved in repetition so that
8977 each repetition moves up in the source file.
8979 In general, the @code{list} command expects you to supply zero, one or two
8980 @dfn{locations}. Locations specify source lines; there are several ways
8981 of writing them (@pxref{Specify Location}), but the effect is always
8982 to specify some source line.
8984 Here is a complete description of the possible arguments for @code{list}:
8987 @item list @var{location}
8988 Print lines centered around the line specified by @var{location}.
8990 @item list @var{first},@var{last}
8991 Print lines from @var{first} to @var{last}. Both arguments are
8992 locations. When a @code{list} command has two locations, and the
8993 source file of the second location is omitted, this refers to
8994 the same source file as the first location.
8996 @item list ,@var{last}
8997 Print lines ending with @var{last}.
8999 @item list @var{first},
9000 Print lines starting with @var{first}.
9003 Print lines just after the lines last printed.
9006 Print lines just before the lines last printed.
9009 As described in the preceding table.
9012 @node Specify Location
9013 @section Specifying a Location
9014 @cindex specifying location
9016 @cindex source location
9018 Several @value{GDBN} commands accept arguments that specify a location
9019 of your program's code. Since @value{GDBN} is a source-level
9020 debugger, a location usually specifies some line in the source code.
9021 Locations may be specified using three different formats:
9022 linespec locations, explicit locations, or address locations.
9025 * Linespec Locations:: Linespec locations
9026 * Explicit Locations:: Explicit locations
9027 * Address Locations:: Address locations
9030 @node Linespec Locations
9031 @subsection Linespec Locations
9032 @cindex linespec locations
9034 A @dfn{linespec} is a colon-separated list of source location parameters such
9035 as file name, function name, etc. Here are all the different ways of
9036 specifying a linespec:
9040 Specifies the line number @var{linenum} of the current source file.
9043 @itemx +@var{offset}
9044 Specifies the line @var{offset} lines before or after the @dfn{current
9045 line}. For the @code{list} command, the current line is the last one
9046 printed; for the breakpoint commands, this is the line at which
9047 execution stopped in the currently selected @dfn{stack frame}
9048 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9049 used as the second of the two linespecs in a @code{list} command,
9050 this specifies the line @var{offset} lines up or down from the first
9053 @item @var{filename}:@var{linenum}
9054 Specifies the line @var{linenum} in the source file @var{filename}.
9055 If @var{filename} is a relative file name, then it will match any
9056 source file name with the same trailing components. For example, if
9057 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9058 name of @file{/build/trunk/gcc/expr.c}, but not
9059 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9061 @item @var{function}
9062 Specifies the line that begins the body of the function @var{function}.
9063 For example, in C, this is the line with the open brace.
9065 By default, in C@t{++} and Ada, @var{function} is interpreted as
9066 specifying all functions named @var{function} in all scopes. For
9067 C@t{++}, this means in all namespaces and classes. For Ada, this
9068 means in all packages.
9070 For example, assuming a program with C@t{++} symbols named
9071 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9072 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9074 Commands that accept a linespec let you override this with the
9075 @code{-qualified} option. For example, @w{@kbd{break -qualified
9076 func}} sets a breakpoint on a free-function named @code{func} ignoring
9077 any C@t{++} class methods and namespace functions called @code{func}.
9079 @xref{Explicit Locations}.
9081 @item @var{function}:@var{label}
9082 Specifies the line where @var{label} appears in @var{function}.
9084 @item @var{filename}:@var{function}
9085 Specifies the line that begins the body of the function @var{function}
9086 in the file @var{filename}. You only need the file name with a
9087 function name to avoid ambiguity when there are identically named
9088 functions in different source files.
9091 Specifies the line at which the label named @var{label} appears
9092 in the function corresponding to the currently selected stack frame.
9093 If there is no current selected stack frame (for instance, if the inferior
9094 is not running), then @value{GDBN} will not search for a label.
9096 @cindex breakpoint at static probe point
9097 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9098 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9099 applications to embed static probes. @xref{Static Probe Points}, for more
9100 information on finding and using static probes. This form of linespec
9101 specifies the location of such a static probe.
9103 If @var{objfile} is given, only probes coming from that shared library
9104 or executable matching @var{objfile} as a regular expression are considered.
9105 If @var{provider} is given, then only probes from that provider are considered.
9106 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9107 each one of those probes.
9110 @node Explicit Locations
9111 @subsection Explicit Locations
9112 @cindex explicit locations
9114 @dfn{Explicit locations} allow the user to directly specify the source
9115 location's parameters using option-value pairs.
9117 Explicit locations are useful when several functions, labels, or
9118 file names have the same name (base name for files) in the program's
9119 sources. In these cases, explicit locations point to the source
9120 line you meant more accurately and unambiguously. Also, using
9121 explicit locations might be faster in large programs.
9123 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9124 defined in the file named @file{foo} or the label @code{bar} in a function
9125 named @code{foo}. @value{GDBN} must search either the file system or
9126 the symbol table to know.
9128 The list of valid explicit location options is summarized in the
9132 @item -source @var{filename}
9133 The value specifies the source file name. To differentiate between
9134 files with the same base name, prepend as many directories as is necessary
9135 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9136 @value{GDBN} will use the first file it finds with the given base
9137 name. This option requires the use of either @code{-function} or @code{-line}.
9139 @item -function @var{function}
9140 The value specifies the name of a function. Operations
9141 on function locations unmodified by other options (such as @code{-label}
9142 or @code{-line}) refer to the line that begins the body of the function.
9143 In C, for example, this is the line with the open brace.
9145 By default, in C@t{++} and Ada, @var{function} is interpreted as
9146 specifying all functions named @var{function} in all scopes. For
9147 C@t{++}, this means in all namespaces and classes. For Ada, this
9148 means in all packages.
9150 For example, assuming a program with C@t{++} symbols named
9151 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9152 -function func}} and @w{@kbd{break -function B::func}} set a
9153 breakpoint on both symbols.
9155 You can use the @kbd{-qualified} flag to override this (see below).
9159 This flag makes @value{GDBN} interpret a function name specified with
9160 @kbd{-function} as a complete fully-qualified name.
9162 For example, assuming a C@t{++} program with symbols named
9163 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9164 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9166 (Note: the @kbd{-qualified} option can precede a linespec as well
9167 (@pxref{Linespec Locations}), so the particular example above could be
9168 simplified as @w{@kbd{break -qualified B::func}}.)
9170 @item -label @var{label}
9171 The value specifies the name of a label. When the function
9172 name is not specified, the label is searched in the function of the currently
9173 selected stack frame.
9175 @item -line @var{number}
9176 The value specifies a line offset for the location. The offset may either
9177 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9178 the command. When specified without any other options, the line offset is
9179 relative to the current line.
9182 Explicit location options may be abbreviated by omitting any non-unique
9183 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9185 @node Address Locations
9186 @subsection Address Locations
9187 @cindex address locations
9189 @dfn{Address locations} indicate a specific program address. They have
9190 the generalized form *@var{address}.
9192 For line-oriented commands, such as @code{list} and @code{edit}, this
9193 specifies a source line that contains @var{address}. For @code{break} and
9194 other breakpoint-oriented commands, this can be used to set breakpoints in
9195 parts of your program which do not have debugging information or
9198 Here @var{address} may be any expression valid in the current working
9199 language (@pxref{Languages, working language}) that specifies a code
9200 address. In addition, as a convenience, @value{GDBN} extends the
9201 semantics of expressions used in locations to cover several situations
9202 that frequently occur during debugging. Here are the various forms
9206 @item @var{expression}
9207 Any expression valid in the current working language.
9209 @item @var{funcaddr}
9210 An address of a function or procedure derived from its name. In C,
9211 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9212 simply the function's name @var{function} (and actually a special case
9213 of a valid expression). In Pascal and Modula-2, this is
9214 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9215 (although the Pascal form also works).
9217 This form specifies the address of the function's first instruction,
9218 before the stack frame and arguments have been set up.
9220 @item '@var{filename}':@var{funcaddr}
9221 Like @var{funcaddr} above, but also specifies the name of the source
9222 file explicitly. This is useful if the name of the function does not
9223 specify the function unambiguously, e.g., if there are several
9224 functions with identical names in different source files.
9228 @section Editing Source Files
9229 @cindex editing source files
9232 @kindex e @r{(@code{edit})}
9233 To edit the lines in a source file, use the @code{edit} command.
9234 The editing program of your choice
9235 is invoked with the current line set to
9236 the active line in the program.
9237 Alternatively, there are several ways to specify what part of the file you
9238 want to print if you want to see other parts of the program:
9241 @item edit @var{location}
9242 Edit the source file specified by @code{location}. Editing starts at
9243 that @var{location}, e.g., at the specified source line of the
9244 specified file. @xref{Specify Location}, for all the possible forms
9245 of the @var{location} argument; here are the forms of the @code{edit}
9246 command most commonly used:
9249 @item edit @var{number}
9250 Edit the current source file with @var{number} as the active line number.
9252 @item edit @var{function}
9253 Edit the file containing @var{function} at the beginning of its definition.
9258 @subsection Choosing your Editor
9259 You can customize @value{GDBN} to use any editor you want
9261 The only restriction is that your editor (say @code{ex}), recognizes the
9262 following command-line syntax:
9264 ex +@var{number} file
9266 The optional numeric value +@var{number} specifies the number of the line in
9267 the file where to start editing.}.
9268 By default, it is @file{@value{EDITOR}}, but you can change this
9269 by setting the environment variable @env{EDITOR} before using
9270 @value{GDBN}. For example, to configure @value{GDBN} to use the
9271 @code{vi} editor, you could use these commands with the @code{sh} shell:
9277 or in the @code{csh} shell,
9279 setenv EDITOR /usr/bin/vi
9284 @section Searching Source Files
9285 @cindex searching source files
9287 There are two commands for searching through the current source file for a
9292 @kindex forward-search
9293 @kindex fo @r{(@code{forward-search})}
9294 @item forward-search @var{regexp}
9295 @itemx search @var{regexp}
9296 The command @samp{forward-search @var{regexp}} checks each line,
9297 starting with the one following the last line listed, for a match for
9298 @var{regexp}. It lists the line that is found. You can use the
9299 synonym @samp{search @var{regexp}} or abbreviate the command name as
9302 @kindex reverse-search
9303 @item reverse-search @var{regexp}
9304 The command @samp{reverse-search @var{regexp}} checks each line, starting
9305 with the one before the last line listed and going backward, for a match
9306 for @var{regexp}. It lists the line that is found. You can abbreviate
9307 this command as @code{rev}.
9311 @section Specifying Source Directories
9314 @cindex directories for source files
9315 Executable programs sometimes do not record the directories of the source
9316 files from which they were compiled, just the names. Even when they do,
9317 the directories could be moved between the compilation and your debugging
9318 session. @value{GDBN} has a list of directories to search for source files;
9319 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9320 it tries all the directories in the list, in the order they are present
9321 in the list, until it finds a file with the desired name.
9323 For example, suppose an executable references the file
9324 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9325 directory, and the @dfn{source path} is @file{/mnt/cross}.
9326 @value{GDBN} would look for the source file in the following
9331 @item @file{/usr/src/foo-1.0/lib/foo.c}
9332 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9333 @item @file{/mnt/cross/foo.c}
9337 If the source file is not present at any of the above locations then
9338 an error is printed. @value{GDBN} does not look up the parts of the
9339 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9340 Likewise, the subdirectories of the source path are not searched: if
9341 the source path is @file{/mnt/cross}, and the binary refers to
9342 @file{foo.c}, @value{GDBN} would not find it under
9343 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9345 Plain file names, relative file names with leading directories, file
9346 names containing dots, etc.@: are all treated as described above,
9347 except that non-absolute file names are not looked up literally. If
9348 the @dfn{source path} is @file{/mnt/cross}, the source file is
9349 recorded as @file{../lib/foo.c}, and no compilation directory is
9350 recorded, then @value{GDBN} will search in the following locations:
9354 @item @file{/mnt/cross/../lib/foo.c}
9355 @item @file{/mnt/cross/foo.c}
9361 @vindex $cdir@r{, convenience variable}
9362 @vindex $cwd@r{, convenience variable}
9363 @cindex compilation directory
9364 @cindex current directory
9365 @cindex working directory
9366 @cindex directory, current
9367 @cindex directory, compilation
9368 The @dfn{source path} will always include two special entries
9369 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9370 (if one is recorded) and the current working directory respectively.
9372 @samp{$cdir} causes @value{GDBN} to search within the compilation
9373 directory, if one is recorded in the debug information. If no
9374 compilation directory is recorded in the debug information then
9375 @samp{$cdir} is ignored.
9377 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9378 current working directory as it changes during your @value{GDBN}
9379 session, while the latter is immediately expanded to the current
9380 directory at the time you add an entry to the source path.
9382 If a compilation directory is recorded in the debug information, and
9383 @value{GDBN} has not found the source file after the first search
9384 using @dfn{source path}, then @value{GDBN} will combine the
9385 compilation directory and the filename, and then search for the source
9386 file again using the @dfn{source path}.
9388 For example, if the executable records the source file as
9389 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9390 recorded as @file{/project/build}, and the @dfn{source path} is
9391 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9392 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9393 search for the source file in the following locations:
9397 @item @file{/usr/src/foo-1.0/lib/foo.c}
9398 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9399 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9400 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9401 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9402 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9403 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9404 @item @file{/mnt/cross/foo.c}
9405 @item @file{/project/build/foo.c}
9406 @item @file{/home/user/foo.c}
9410 If the file name in the previous example had been recorded in the
9411 executable as a relative path rather than an absolute path, then the
9412 first look up would not have occurred, but all of the remaining steps
9415 When searching for source files on MS-DOS and MS-Windows, where
9416 absolute paths start with a drive letter (e.g.@:
9417 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9418 from the file name before appending it to a search directory from
9419 @dfn{source path}; for instance if the executable references the
9420 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9421 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9422 locations for the source file:
9426 @item @file{C:/project/foo.c}
9427 @item @file{D:/mnt/cross/project/foo.c}
9428 @item @file{D:/mnt/cross/foo.c}
9432 Note that the executable search path is @emph{not} used to locate the
9435 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9436 any information it has cached about where source files are found and where
9437 each line is in the file.
9441 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9442 and @samp{$cwd}, in that order.
9443 To add other directories, use the @code{directory} command.
9445 The search path is used to find both program source files and @value{GDBN}
9446 script files (read using the @samp{-command} option and @samp{source} command).
9448 In addition to the source path, @value{GDBN} provides a set of commands
9449 that manage a list of source path substitution rules. A @dfn{substitution
9450 rule} specifies how to rewrite source directories stored in the program's
9451 debug information in case the sources were moved to a different
9452 directory between compilation and debugging. A rule is made of
9453 two strings, the first specifying what needs to be rewritten in
9454 the path, and the second specifying how it should be rewritten.
9455 In @ref{set substitute-path}, we name these two parts @var{from} and
9456 @var{to} respectively. @value{GDBN} does a simple string replacement
9457 of @var{from} with @var{to} at the start of the directory part of the
9458 source file name, and uses that result instead of the original file
9459 name to look up the sources.
9461 Using the previous example, suppose the @file{foo-1.0} tree has been
9462 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9463 @value{GDBN} to replace @file{/usr/src} in all source path names with
9464 @file{/mnt/cross}. The first lookup will then be
9465 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9466 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9467 substitution rule, use the @code{set substitute-path} command
9468 (@pxref{set substitute-path}).
9470 To avoid unexpected substitution results, a rule is applied only if the
9471 @var{from} part of the directory name ends at a directory separator.
9472 For instance, a rule substituting @file{/usr/source} into
9473 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9474 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9475 is applied only at the beginning of the directory name, this rule will
9476 not be applied to @file{/root/usr/source/baz.c} either.
9478 In many cases, you can achieve the same result using the @code{directory}
9479 command. However, @code{set substitute-path} can be more efficient in
9480 the case where the sources are organized in a complex tree with multiple
9481 subdirectories. With the @code{directory} command, you need to add each
9482 subdirectory of your project. If you moved the entire tree while
9483 preserving its internal organization, then @code{set substitute-path}
9484 allows you to direct the debugger to all the sources with one single
9487 @code{set substitute-path} is also more than just a shortcut command.
9488 The source path is only used if the file at the original location no
9489 longer exists. On the other hand, @code{set substitute-path} modifies
9490 the debugger behavior to look at the rewritten location instead. So, if
9491 for any reason a source file that is not relevant to your executable is
9492 located at the original location, a substitution rule is the only
9493 method available to point @value{GDBN} at the new location.
9495 @cindex @samp{--with-relocated-sources}
9496 @cindex default source path substitution
9497 You can configure a default source path substitution rule by
9498 configuring @value{GDBN} with the
9499 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9500 should be the name of a directory under @value{GDBN}'s configured
9501 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9502 directory names in debug information under @var{dir} will be adjusted
9503 automatically if the installed @value{GDBN} is moved to a new
9504 location. This is useful if @value{GDBN}, libraries or executables
9505 with debug information and corresponding source code are being moved
9509 @item directory @var{dirname} @dots{}
9510 @item dir @var{dirname} @dots{}
9511 Add directory @var{dirname} to the front of the source path. Several
9512 directory names may be given to this command, separated by @samp{:}
9513 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9514 part of absolute file names) or
9515 whitespace. You may specify a directory that is already in the source
9516 path; this moves it forward, so @value{GDBN} searches it sooner.
9518 The special strings @samp{$cdir} (to refer to the compilation
9519 directory, if one is recorded), and @samp{$cwd} (to refer to the
9520 current working directory) can also be included in the list of
9521 directories @var{dirname}. Though these will already be in the source
9522 path they will be moved forward in the list so @value{GDBN} searches
9526 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9528 @c RET-repeat for @code{directory} is explicitly disabled, but since
9529 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9531 @item set directories @var{path-list}
9532 @kindex set directories
9533 Set the source path to @var{path-list}.
9534 @samp{$cdir:$cwd} are added if missing.
9536 @item show directories
9537 @kindex show directories
9538 Print the source path: show which directories it contains.
9540 @anchor{set substitute-path}
9541 @item set substitute-path @var{from} @var{to}
9542 @kindex set substitute-path
9543 Define a source path substitution rule, and add it at the end of the
9544 current list of existing substitution rules. If a rule with the same
9545 @var{from} was already defined, then the old rule is also deleted.
9547 For example, if the file @file{/foo/bar/baz.c} was moved to
9548 @file{/mnt/cross/baz.c}, then the command
9551 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9555 will tell @value{GDBN} to replace @samp{/foo/bar} with
9556 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9557 @file{baz.c} even though it was moved.
9559 In the case when more than one substitution rule have been defined,
9560 the rules are evaluated one by one in the order where they have been
9561 defined. The first one matching, if any, is selected to perform
9564 For instance, if we had entered the following commands:
9567 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9568 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9572 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9573 @file{/mnt/include/defs.h} by using the first rule. However, it would
9574 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9575 @file{/mnt/src/lib/foo.c}.
9578 @item unset substitute-path [path]
9579 @kindex unset substitute-path
9580 If a path is specified, search the current list of substitution rules
9581 for a rule that would rewrite that path. Delete that rule if found.
9582 A warning is emitted by the debugger if no rule could be found.
9584 If no path is specified, then all substitution rules are deleted.
9586 @item show substitute-path [path]
9587 @kindex show substitute-path
9588 If a path is specified, then print the source path substitution rule
9589 which would rewrite that path, if any.
9591 If no path is specified, then print all existing source path substitution
9596 If your source path is cluttered with directories that are no longer of
9597 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9598 versions of source. You can correct the situation as follows:
9602 Use @code{directory} with no argument to reset the source path to its default value.
9605 Use @code{directory} with suitable arguments to reinstall the
9606 directories you want in the source path. You can add all the
9607 directories in one command.
9611 @section Source and Machine Code
9612 @cindex source line and its code address
9614 You can use the command @code{info line} to map source lines to program
9615 addresses (and vice versa), and the command @code{disassemble} to display
9616 a range of addresses as machine instructions. You can use the command
9617 @code{set disassemble-next-line} to set whether to disassemble next
9618 source line when execution stops. When run under @sc{gnu} Emacs
9619 mode, the @code{info line} command causes the arrow to point to the
9620 line specified. Also, @code{info line} prints addresses in symbolic form as
9626 @itemx info line @var{location}
9627 Print the starting and ending addresses of the compiled code for
9628 source line @var{location}. You can specify source lines in any of
9629 the ways documented in @ref{Specify Location}. With no @var{location}
9630 information about the current source line is printed.
9633 For example, we can use @code{info line} to discover the location of
9634 the object code for the first line of function
9635 @code{m4_changequote}:
9638 (@value{GDBP}) info line m4_changequote
9639 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9640 ends at 0x6350 <m4_changequote+4>.
9644 @cindex code address and its source line
9645 We can also inquire (using @code{*@var{addr}} as the form for
9646 @var{location}) what source line covers a particular address:
9648 (@value{GDBP}) info line *0x63ff
9649 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9650 ends at 0x6404 <m4_changequote+184>.
9653 @cindex @code{$_} and @code{info line}
9654 @cindex @code{x} command, default address
9655 @kindex x@r{(examine), and} info line
9656 After @code{info line}, the default address for the @code{x} command
9657 is changed to the starting address of the line, so that @samp{x/i} is
9658 sufficient to begin examining the machine code (@pxref{Memory,
9659 ,Examining Memory}). Also, this address is saved as the value of the
9660 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9663 @cindex info line, repeated calls
9664 After @code{info line}, using @code{info line} again without
9665 specifying a location will display information about the next source
9670 @cindex assembly instructions
9671 @cindex instructions, assembly
9672 @cindex machine instructions
9673 @cindex listing machine instructions
9675 @itemx disassemble /m
9676 @itemx disassemble /s
9677 @itemx disassemble /r
9678 This specialized command dumps a range of memory as machine
9679 instructions. It can also print mixed source+disassembly by specifying
9680 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9681 as well as in symbolic form by specifying the @code{/r} modifier.
9682 The default memory range is the function surrounding the
9683 program counter of the selected frame. A single argument to this
9684 command is a program counter value; @value{GDBN} dumps the function
9685 surrounding this value. When two arguments are given, they should
9686 be separated by a comma, possibly surrounded by whitespace. The
9687 arguments specify a range of addresses to dump, in one of two forms:
9690 @item @var{start},@var{end}
9691 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9692 @item @var{start},+@var{length}
9693 the addresses from @var{start} (inclusive) to
9694 @code{@var{start}+@var{length}} (exclusive).
9698 When 2 arguments are specified, the name of the function is also
9699 printed (since there could be several functions in the given range).
9701 The argument(s) can be any expression yielding a numeric value, such as
9702 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9704 If the range of memory being disassembled contains current program counter,
9705 the instruction at that location is shown with a @code{=>} marker.
9708 The following example shows the disassembly of a range of addresses of
9709 HP PA-RISC 2.0 code:
9712 (@value{GDBP}) disas 0x32c4, 0x32e4
9713 Dump of assembler code from 0x32c4 to 0x32e4:
9714 0x32c4 <main+204>: addil 0,dp
9715 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9716 0x32cc <main+212>: ldil 0x3000,r31
9717 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9718 0x32d4 <main+220>: ldo 0(r31),rp
9719 0x32d8 <main+224>: addil -0x800,dp
9720 0x32dc <main+228>: ldo 0x588(r1),r26
9721 0x32e0 <main+232>: ldil 0x3000,r31
9722 End of assembler dump.
9725 Here is an example showing mixed source+assembly for Intel x86
9726 with @code{/m} or @code{/s}, when the program is stopped just after
9727 function prologue in a non-optimized function with no inline code.
9730 (@value{GDBP}) disas /m main
9731 Dump of assembler code for function main:
9733 0x08048330 <+0>: push %ebp
9734 0x08048331 <+1>: mov %esp,%ebp
9735 0x08048333 <+3>: sub $0x8,%esp
9736 0x08048336 <+6>: and $0xfffffff0,%esp
9737 0x08048339 <+9>: sub $0x10,%esp
9739 6 printf ("Hello.\n");
9740 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9741 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9745 0x08048348 <+24>: mov $0x0,%eax
9746 0x0804834d <+29>: leave
9747 0x0804834e <+30>: ret
9749 End of assembler dump.
9752 The @code{/m} option is deprecated as its output is not useful when
9753 there is either inlined code or re-ordered code.
9754 The @code{/s} option is the preferred choice.
9755 Here is an example for AMD x86-64 showing the difference between
9756 @code{/m} output and @code{/s} output.
9757 This example has one inline function defined in a header file,
9758 and the code is compiled with @samp{-O2} optimization.
9759 Note how the @code{/m} output is missing the disassembly of
9760 several instructions that are present in the @code{/s} output.
9790 (@value{GDBP}) disas /m main
9791 Dump of assembler code for function main:
9795 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9796 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9800 0x000000000040041d <+29>: xor %eax,%eax
9801 0x000000000040041f <+31>: retq
9802 0x0000000000400420 <+32>: add %eax,%eax
9803 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9805 End of assembler dump.
9806 (@value{GDBP}) disas /s main
9807 Dump of assembler code for function main:
9811 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9815 0x0000000000400406 <+6>: test %eax,%eax
9816 0x0000000000400408 <+8>: js 0x400420 <main+32>
9821 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9822 0x000000000040040d <+13>: test %eax,%eax
9823 0x000000000040040f <+15>: mov $0x1,%eax
9824 0x0000000000400414 <+20>: cmovne %edx,%eax
9828 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9832 0x000000000040041d <+29>: xor %eax,%eax
9833 0x000000000040041f <+31>: retq
9837 0x0000000000400420 <+32>: add %eax,%eax
9838 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9839 End of assembler dump.
9842 Here is another example showing raw instructions in hex for AMD x86-64,
9845 (gdb) disas /r 0x400281,+10
9846 Dump of assembler code from 0x400281 to 0x40028b:
9847 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9848 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9849 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9850 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9851 End of assembler dump.
9854 Addresses cannot be specified as a location (@pxref{Specify Location}).
9855 So, for example, if you want to disassemble function @code{bar}
9856 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9857 and not @samp{disassemble foo.c:bar}.
9859 Some architectures have more than one commonly-used set of instruction
9860 mnemonics or other syntax.
9862 For programs that were dynamically linked and use shared libraries,
9863 instructions that call functions or branch to locations in the shared
9864 libraries might show a seemingly bogus location---it's actually a
9865 location of the relocation table. On some architectures, @value{GDBN}
9866 might be able to resolve these to actual function names.
9869 @kindex set disassembler-options
9870 @cindex disassembler options
9871 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9872 This command controls the passing of target specific information to
9873 the disassembler. For a list of valid options, please refer to the
9874 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9875 manual and/or the output of @kbd{objdump --help}
9876 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9877 The default value is the empty string.
9879 If it is necessary to specify more than one disassembler option, then
9880 multiple options can be placed together into a comma separated list.
9881 Currently this command is only supported on targets ARC, ARM, MIPS,
9884 @kindex show disassembler-options
9885 @item show disassembler-options
9886 Show the current setting of the disassembler options.
9890 @kindex set disassembly-flavor
9891 @cindex Intel disassembly flavor
9892 @cindex AT&T disassembly flavor
9893 @item set disassembly-flavor @var{instruction-set}
9894 Select the instruction set to use when disassembling the
9895 program via the @code{disassemble} or @code{x/i} commands.
9897 Currently this command is only defined for the Intel x86 family. You
9898 can set @var{instruction-set} to either @code{intel} or @code{att}.
9899 The default is @code{att}, the AT&T flavor used by default by Unix
9900 assemblers for x86-based targets.
9902 @kindex show disassembly-flavor
9903 @item show disassembly-flavor
9904 Show the current setting of the disassembly flavor.
9908 @kindex set disassemble-next-line
9909 @kindex show disassemble-next-line
9910 @item set disassemble-next-line
9911 @itemx show disassemble-next-line
9912 Control whether or not @value{GDBN} will disassemble the next source
9913 line or instruction when execution stops. If ON, @value{GDBN} will
9914 display disassembly of the next source line when execution of the
9915 program being debugged stops. This is @emph{in addition} to
9916 displaying the source line itself, which @value{GDBN} always does if
9917 possible. If the next source line cannot be displayed for some reason
9918 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9919 info in the debug info), @value{GDBN} will display disassembly of the
9920 next @emph{instruction} instead of showing the next source line. If
9921 AUTO, @value{GDBN} will display disassembly of next instruction only
9922 if the source line cannot be displayed. This setting causes
9923 @value{GDBN} to display some feedback when you step through a function
9924 with no line info or whose source file is unavailable. The default is
9925 OFF, which means never display the disassembly of the next line or
9931 @chapter Examining Data
9933 @cindex printing data
9934 @cindex examining data
9937 The usual way to examine data in your program is with the @code{print}
9938 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9939 evaluates and prints the value of an expression of the language your
9940 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9941 Different Languages}). It may also print the expression using a
9942 Python-based pretty-printer (@pxref{Pretty Printing}).
9945 @item print [[@var{options}] --] @var{expr}
9946 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9947 @var{expr} is an expression (in the source language). By default the
9948 value of @var{expr} is printed in a format appropriate to its data type;
9949 you can choose a different format by specifying @samp{/@var{f}}, where
9950 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9953 @anchor{print options}
9954 The @code{print} command supports a number of options that allow
9955 overriding relevant global print settings as set by @code{set print}
9959 @item -address [@code{on}|@code{off}]
9960 Set printing of addresses.
9961 Related setting: @ref{set print address}.
9963 @item -array [@code{on}|@code{off}]
9964 Pretty formatting of arrays.
9965 Related setting: @ref{set print array}.
9967 @item -array-indexes [@code{on}|@code{off}]
9968 Set printing of array indexes.
9969 Related setting: @ref{set print array-indexes}.
9971 @item -elements @var{number-of-elements}|@code{unlimited}
9972 Set limit on string chars or array elements to print. The value
9973 @code{unlimited} causes there to be no limit. Related setting:
9974 @ref{set print elements}.
9976 @item -max-depth @var{depth}|@code{unlimited}
9977 Set the threshold after which nested structures are replaced with
9978 ellipsis. Related setting: @ref{set print max-depth}.
9980 @item -null-stop [@code{on}|@code{off}]
9981 Set printing of char arrays to stop at first null char. Related
9982 setting: @ref{set print null-stop}.
9984 @item -object [@code{on}|@code{off}]
9985 Set printing C@t{++} virtual function tables. Related setting:
9986 @ref{set print object}.
9988 @item -pretty [@code{on}|@code{off}]
9989 Set pretty formatting of structures. Related setting: @ref{set print
9992 @item -raw-values [@code{on}|@code{off}]
9993 Set whether to print values in raw form, bypassing any
9994 pretty-printers for that value. Related setting: @ref{set print
9997 @item -repeats @var{number-of-repeats}|@code{unlimited}
9998 Set threshold for repeated print elements. @code{unlimited} causes
9999 all elements to be individually printed. Related setting: @ref{set
10002 @item -static-members [@code{on}|@code{off}]
10003 Set printing C@t{++} static members. Related setting: @ref{set print
10006 @item -symbol [@code{on}|@code{off}]
10007 Set printing of symbol names when printing pointers. Related setting:
10008 @ref{set print symbol}.
10010 @item -union [@code{on}|@code{off}]
10011 Set printing of unions interior to structures. Related setting:
10012 @ref{set print union}.
10014 @item -vtbl [@code{on}|@code{off}]
10015 Set printing of C++ virtual function tables. Related setting:
10016 @ref{set print vtbl}.
10019 Because the @code{print} command accepts arbitrary expressions which
10020 may look like options (including abbreviations), if you specify any
10021 command option, then you must use a double dash (@code{--}) to mark
10022 the end of option processing.
10024 For example, this prints the value of the @code{-p} expression:
10027 (@value{GDBP}) print -p
10030 While this repeats the last value in the value history (see below)
10031 with the @code{-pretty} option in effect:
10034 (@value{GDBP}) print -p --
10037 Here is an example including both on option and an expression:
10041 (@value{GDBP}) print -pretty -- *myptr
10053 @item print [@var{options}]
10054 @itemx print [@var{options}] /@var{f}
10055 @cindex reprint the last value
10056 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10057 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10058 conveniently inspect the same value in an alternative format.
10061 If the architecture supports memory tagging, the @code{print} command will
10062 display pointer/memory tag mismatches if what is being printed is a pointer
10063 or reference type. @xref{Memory Tagging}.
10065 A more low-level way of examining data is with the @code{x} command.
10066 It examines data in memory at a specified address and prints it in a
10067 specified format. @xref{Memory, ,Examining Memory}.
10069 If you are interested in information about types, or about how the
10070 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
10071 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10074 @cindex exploring hierarchical data structures
10076 Another way of examining values of expressions and type information is
10077 through the Python extension command @code{explore} (available only if
10078 the @value{GDBN} build is configured with @code{--with-python}). It
10079 offers an interactive way to start at the highest level (or, the most
10080 abstract level) of the data type of an expression (or, the data type
10081 itself) and explore all the way down to leaf scalar values/fields
10082 embedded in the higher level data types.
10085 @item explore @var{arg}
10086 @var{arg} is either an expression (in the source language), or a type
10087 visible in the current context of the program being debugged.
10090 The working of the @code{explore} command can be illustrated with an
10091 example. If a data type @code{struct ComplexStruct} is defined in your
10095 struct SimpleStruct
10101 struct ComplexStruct
10103 struct SimpleStruct *ss_p;
10109 followed by variable declarations as
10112 struct SimpleStruct ss = @{ 10, 1.11 @};
10113 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10117 then, the value of the variable @code{cs} can be explored using the
10118 @code{explore} command as follows.
10122 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10123 the following fields:
10125 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10126 arr = <Enter 1 to explore this field of type `int [10]'>
10128 Enter the field number of choice:
10132 Since the fields of @code{cs} are not scalar values, you are being
10133 prompted to chose the field you want to explore. Let's say you choose
10134 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10135 pointer, you will be asked if it is pointing to a single value. From
10136 the declaration of @code{cs} above, it is indeed pointing to a single
10137 value, hence you enter @code{y}. If you enter @code{n}, then you will
10138 be asked if it were pointing to an array of values, in which case this
10139 field will be explored as if it were an array.
10142 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10143 Continue exploring it as a pointer to a single value [y/n]: y
10144 The value of `*(cs.ss_p)' is a struct/class of type `struct
10145 SimpleStruct' with the following fields:
10147 i = 10 .. (Value of type `int')
10148 d = 1.1100000000000001 .. (Value of type `double')
10150 Press enter to return to parent value:
10154 If the field @code{arr} of @code{cs} was chosen for exploration by
10155 entering @code{1} earlier, then since it is as array, you will be
10156 prompted to enter the index of the element in the array that you want
10160 `cs.arr' is an array of `int'.
10161 Enter the index of the element you want to explore in `cs.arr': 5
10163 `(cs.arr)[5]' is a scalar value of type `int'.
10167 Press enter to return to parent value:
10170 In general, at any stage of exploration, you can go deeper towards the
10171 leaf values by responding to the prompts appropriately, or hit the
10172 return key to return to the enclosing data structure (the @i{higher}
10173 level data structure).
10175 Similar to exploring values, you can use the @code{explore} command to
10176 explore types. Instead of specifying a value (which is typically a
10177 variable name or an expression valid in the current context of the
10178 program being debugged), you specify a type name. If you consider the
10179 same example as above, your can explore the type
10180 @code{struct ComplexStruct} by passing the argument
10181 @code{struct ComplexStruct} to the @code{explore} command.
10184 (gdb) explore struct ComplexStruct
10188 By responding to the prompts appropriately in the subsequent interactive
10189 session, you can explore the type @code{struct ComplexStruct} in a
10190 manner similar to how the value @code{cs} was explored in the above
10193 The @code{explore} command also has two sub-commands,
10194 @code{explore value} and @code{explore type}. The former sub-command is
10195 a way to explicitly specify that value exploration of the argument is
10196 being invoked, while the latter is a way to explicitly specify that type
10197 exploration of the argument is being invoked.
10200 @item explore value @var{expr}
10201 @cindex explore value
10202 This sub-command of @code{explore} explores the value of the
10203 expression @var{expr} (if @var{expr} is an expression valid in the
10204 current context of the program being debugged). The behavior of this
10205 command is identical to that of the behavior of the @code{explore}
10206 command being passed the argument @var{expr}.
10208 @item explore type @var{arg}
10209 @cindex explore type
10210 This sub-command of @code{explore} explores the type of @var{arg} (if
10211 @var{arg} is a type visible in the current context of program being
10212 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10213 is an expression valid in the current context of the program being
10214 debugged). If @var{arg} is a type, then the behavior of this command is
10215 identical to that of the @code{explore} command being passed the
10216 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10217 this command will be identical to that of the @code{explore} command
10218 being passed the type of @var{arg} as the argument.
10222 * Expressions:: Expressions
10223 * Ambiguous Expressions:: Ambiguous Expressions
10224 * Variables:: Program variables
10225 * Arrays:: Artificial arrays
10226 * Output Formats:: Output formats
10227 * Memory:: Examining memory
10228 * Memory Tagging:: Memory Tagging
10229 * Auto Display:: Automatic display
10230 * Print Settings:: Print settings
10231 * Pretty Printing:: Python pretty printing
10232 * Value History:: Value history
10233 * Convenience Vars:: Convenience variables
10234 * Convenience Funs:: Convenience functions
10235 * Registers:: Registers
10236 * Floating Point Hardware:: Floating point hardware
10237 * Vector Unit:: Vector Unit
10238 * OS Information:: Auxiliary data provided by operating system
10239 * Memory Region Attributes:: Memory region attributes
10240 * Dump/Restore Files:: Copy between memory and a file
10241 * Core File Generation:: Cause a program dump its core
10242 * Character Sets:: Debugging programs that use a different
10243 character set than GDB does
10244 * Caching Target Data:: Data caching for targets
10245 * Searching Memory:: Searching memory for a sequence of bytes
10246 * Value Sizes:: Managing memory allocated for values
10250 @section Expressions
10252 @cindex expressions
10253 @code{print} and many other @value{GDBN} commands accept an expression and
10254 compute its value. Any kind of constant, variable or operator defined
10255 by the programming language you are using is valid in an expression in
10256 @value{GDBN}. This includes conditional expressions, function calls,
10257 casts, and string constants. It also includes preprocessor macros, if
10258 you compiled your program to include this information; see
10261 @cindex arrays in expressions
10262 @value{GDBN} supports array constants in expressions input by
10263 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10264 you can use the command @code{print @{1, 2, 3@}} to create an array
10265 of three integers. If you pass an array to a function or assign it
10266 to a program variable, @value{GDBN} copies the array to memory that
10267 is @code{malloc}ed in the target program.
10269 Because C is so widespread, most of the expressions shown in examples in
10270 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10271 Languages}, for information on how to use expressions in other
10274 In this section, we discuss operators that you can use in @value{GDBN}
10275 expressions regardless of your programming language.
10277 @cindex casts, in expressions
10278 Casts are supported in all languages, not just in C, because it is so
10279 useful to cast a number into a pointer in order to examine a structure
10280 at that address in memory.
10281 @c FIXME: casts supported---Mod2 true?
10283 @value{GDBN} supports these operators, in addition to those common
10284 to programming languages:
10288 @samp{@@} is a binary operator for treating parts of memory as arrays.
10289 @xref{Arrays, ,Artificial Arrays}, for more information.
10292 @samp{::} allows you to specify a variable in terms of the file or
10293 function where it is defined. @xref{Variables, ,Program Variables}.
10295 @cindex @{@var{type}@}
10296 @cindex type casting memory
10297 @cindex memory, viewing as typed object
10298 @cindex casts, to view memory
10299 @item @{@var{type}@} @var{addr}
10300 Refers to an object of type @var{type} stored at address @var{addr} in
10301 memory. The address @var{addr} may be any expression whose value is
10302 an integer or pointer (but parentheses are required around binary
10303 operators, just as in a cast). This construct is allowed regardless
10304 of what kind of data is normally supposed to reside at @var{addr}.
10307 @node Ambiguous Expressions
10308 @section Ambiguous Expressions
10309 @cindex ambiguous expressions
10311 Expressions can sometimes contain some ambiguous elements. For instance,
10312 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10313 a single function name to be defined several times, for application in
10314 different contexts. This is called @dfn{overloading}. Another example
10315 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10316 templates and is typically instantiated several times, resulting in
10317 the same function name being defined in different contexts.
10319 In some cases and depending on the language, it is possible to adjust
10320 the expression to remove the ambiguity. For instance in C@t{++}, you
10321 can specify the signature of the function you want to break on, as in
10322 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10323 qualified name of your function often makes the expression unambiguous
10326 When an ambiguity that needs to be resolved is detected, the debugger
10327 has the capability to display a menu of numbered choices for each
10328 possibility, and then waits for the selection with the prompt @samp{>}.
10329 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10330 aborts the current command. If the command in which the expression was
10331 used allows more than one choice to be selected, the next option in the
10332 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10335 For example, the following session excerpt shows an attempt to set a
10336 breakpoint at the overloaded symbol @code{String::after}.
10337 We choose three particular definitions of that function name:
10339 @c FIXME! This is likely to change to show arg type lists, at least
10342 (@value{GDBP}) b String::after
10345 [2] file:String.cc; line number:867
10346 [3] file:String.cc; line number:860
10347 [4] file:String.cc; line number:875
10348 [5] file:String.cc; line number:853
10349 [6] file:String.cc; line number:846
10350 [7] file:String.cc; line number:735
10352 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10353 Breakpoint 2 at 0xb344: file String.cc, line 875.
10354 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10355 Multiple breakpoints were set.
10356 Use the "delete" command to delete unwanted
10363 @kindex set multiple-symbols
10364 @item set multiple-symbols @var{mode}
10365 @cindex multiple-symbols menu
10367 This option allows you to adjust the debugger behavior when an expression
10370 By default, @var{mode} is set to @code{all}. If the command with which
10371 the expression is used allows more than one choice, then @value{GDBN}
10372 automatically selects all possible choices. For instance, inserting
10373 a breakpoint on a function using an ambiguous name results in a breakpoint
10374 inserted on each possible match. However, if a unique choice must be made,
10375 then @value{GDBN} uses the menu to help you disambiguate the expression.
10376 For instance, printing the address of an overloaded function will result
10377 in the use of the menu.
10379 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10380 when an ambiguity is detected.
10382 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10383 an error due to the ambiguity and the command is aborted.
10385 @kindex show multiple-symbols
10386 @item show multiple-symbols
10387 Show the current value of the @code{multiple-symbols} setting.
10391 @section Program Variables
10393 The most common kind of expression to use is the name of a variable
10396 Variables in expressions are understood in the selected stack frame
10397 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10401 global (or file-static)
10408 visible according to the scope rules of the
10409 programming language from the point of execution in that frame
10412 @noindent This means that in the function
10427 you can examine and use the variable @code{a} whenever your program is
10428 executing within the function @code{foo}, but you can only use or
10429 examine the variable @code{b} while your program is executing inside
10430 the block where @code{b} is declared.
10432 @cindex variable name conflict
10433 There is an exception: you can refer to a variable or function whose
10434 scope is a single source file even if the current execution point is not
10435 in this file. But it is possible to have more than one such variable or
10436 function with the same name (in different source files). If that
10437 happens, referring to that name has unpredictable effects. If you wish,
10438 you can specify a static variable in a particular function or file by
10439 using the colon-colon (@code{::}) notation:
10441 @cindex colon-colon, context for variables/functions
10443 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10444 @cindex @code{::}, context for variables/functions
10447 @var{file}::@var{variable}
10448 @var{function}::@var{variable}
10452 Here @var{file} or @var{function} is the name of the context for the
10453 static @var{variable}. In the case of file names, you can use quotes to
10454 make sure @value{GDBN} parses the file name as a single word---for example,
10455 to print a global value of @code{x} defined in @file{f2.c}:
10458 (@value{GDBP}) p 'f2.c'::x
10461 The @code{::} notation is normally used for referring to
10462 static variables, since you typically disambiguate uses of local variables
10463 in functions by selecting the appropriate frame and using the
10464 simple name of the variable. However, you may also use this notation
10465 to refer to local variables in frames enclosing the selected frame:
10474 process (a); /* Stop here */
10485 For example, if there is a breakpoint at the commented line,
10486 here is what you might see
10487 when the program stops after executing the call @code{bar(0)}:
10492 (@value{GDBP}) p bar::a
10494 (@value{GDBP}) up 2
10495 #2 0x080483d0 in foo (a=5) at foobar.c:12
10498 (@value{GDBP}) p bar::a
10502 @cindex C@t{++} scope resolution
10503 These uses of @samp{::} are very rarely in conflict with the very
10504 similar use of the same notation in C@t{++}. When they are in
10505 conflict, the C@t{++} meaning takes precedence; however, this can be
10506 overridden by quoting the file or function name with single quotes.
10508 For example, suppose the program is stopped in a method of a class
10509 that has a field named @code{includefile}, and there is also an
10510 include file named @file{includefile} that defines a variable,
10511 @code{some_global}.
10514 (@value{GDBP}) p includefile
10516 (@value{GDBP}) p includefile::some_global
10517 A syntax error in expression, near `'.
10518 (@value{GDBP}) p 'includefile'::some_global
10522 @cindex wrong values
10523 @cindex variable values, wrong
10524 @cindex function entry/exit, wrong values of variables
10525 @cindex optimized code, wrong values of variables
10527 @emph{Warning:} Occasionally, a local variable may appear to have the
10528 wrong value at certain points in a function---just after entry to a new
10529 scope, and just before exit.
10531 You may see this problem when you are stepping by machine instructions.
10532 This is because, on most machines, it takes more than one instruction to
10533 set up a stack frame (including local variable definitions); if you are
10534 stepping by machine instructions, variables may appear to have the wrong
10535 values until the stack frame is completely built. On exit, it usually
10536 also takes more than one machine instruction to destroy a stack frame;
10537 after you begin stepping through that group of instructions, local
10538 variable definitions may be gone.
10540 This may also happen when the compiler does significant optimizations.
10541 To be sure of always seeing accurate values, turn off all optimization
10544 @cindex ``No symbol "foo" in current context''
10545 Another possible effect of compiler optimizations is to optimize
10546 unused variables out of existence, or assign variables to registers (as
10547 opposed to memory addresses). Depending on the support for such cases
10548 offered by the debug info format used by the compiler, @value{GDBN}
10549 might not be able to display values for such local variables. If that
10550 happens, @value{GDBN} will print a message like this:
10553 No symbol "foo" in current context.
10556 To solve such problems, either recompile without optimizations, or use a
10557 different debug info format, if the compiler supports several such
10558 formats. @xref{Compilation}, for more information on choosing compiler
10559 options. @xref{C, ,C and C@t{++}}, for more information about debug
10560 info formats that are best suited to C@t{++} programs.
10562 If you ask to print an object whose contents are unknown to
10563 @value{GDBN}, e.g., because its data type is not completely specified
10564 by the debug information, @value{GDBN} will say @samp{<incomplete
10565 type>}. @xref{Symbols, incomplete type}, for more about this.
10567 @cindex no debug info variables
10568 If you try to examine or use the value of a (global) variable for
10569 which @value{GDBN} has no type information, e.g., because the program
10570 includes no debug information, @value{GDBN} displays an error message.
10571 @xref{Symbols, unknown type}, for more about unknown types. If you
10572 cast the variable to its declared type, @value{GDBN} gets the
10573 variable's value using the cast-to type as the variable's type. For
10574 example, in a C program:
10577 (@value{GDBP}) p var
10578 'var' has unknown type; cast it to its declared type
10579 (@value{GDBP}) p (float) var
10583 If you append @kbd{@@entry} string to a function parameter name you get its
10584 value at the time the function got called. If the value is not available an
10585 error message is printed. Entry values are available only with some compilers.
10586 Entry values are normally also printed at the function parameter list according
10587 to @ref{set print entry-values}.
10590 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10596 (gdb) print i@@entry
10600 Strings are identified as arrays of @code{char} values without specified
10601 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10602 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10603 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10604 defines literal string type @code{"char"} as @code{char} without a sign.
10609 signed char var1[] = "A";
10612 You get during debugging
10617 $2 = @{65 'A', 0 '\0'@}
10621 @section Artificial Arrays
10623 @cindex artificial array
10625 @kindex @@@r{, referencing memory as an array}
10626 It is often useful to print out several successive objects of the
10627 same type in memory; a section of an array, or an array of
10628 dynamically determined size for which only a pointer exists in the
10631 You can do this by referring to a contiguous span of memory as an
10632 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10633 operand of @samp{@@} should be the first element of the desired array
10634 and be an individual object. The right operand should be the desired length
10635 of the array. The result is an array value whose elements are all of
10636 the type of the left argument. The first element is actually the left
10637 argument; the second element comes from bytes of memory immediately
10638 following those that hold the first element, and so on. Here is an
10639 example. If a program says
10642 int *array = (int *) malloc (len * sizeof (int));
10646 you can print the contents of @code{array} with
10652 The left operand of @samp{@@} must reside in memory. Array values made
10653 with @samp{@@} in this way behave just like other arrays in terms of
10654 subscripting, and are coerced to pointers when used in expressions.
10655 Artificial arrays most often appear in expressions via the value history
10656 (@pxref{Value History, ,Value History}), after printing one out.
10658 Another way to create an artificial array is to use a cast.
10659 This re-interprets a value as if it were an array.
10660 The value need not be in memory:
10662 (@value{GDBP}) p/x (short[2])0x12345678
10663 $1 = @{0x1234, 0x5678@}
10666 As a convenience, if you leave the array length out (as in
10667 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10668 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10670 (@value{GDBP}) p/x (short[])0x12345678
10671 $2 = @{0x1234, 0x5678@}
10674 Sometimes the artificial array mechanism is not quite enough; in
10675 moderately complex data structures, the elements of interest may not
10676 actually be adjacent---for example, if you are interested in the values
10677 of pointers in an array. One useful work-around in this situation is
10678 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10679 Variables}) as a counter in an expression that prints the first
10680 interesting value, and then repeat that expression via @key{RET}. For
10681 instance, suppose you have an array @code{dtab} of pointers to
10682 structures, and you are interested in the values of a field @code{fv}
10683 in each structure. Here is an example of what you might type:
10693 @node Output Formats
10694 @section Output Formats
10696 @cindex formatted output
10697 @cindex output formats
10698 By default, @value{GDBN} prints a value according to its data type. Sometimes
10699 this is not what you want. For example, you might want to print a number
10700 in hex, or a pointer in decimal. Or you might want to view data in memory
10701 at a certain address as a character string or as an instruction. To do
10702 these things, specify an @dfn{output format} when you print a value.
10704 The simplest use of output formats is to say how to print a value
10705 already computed. This is done by starting the arguments of the
10706 @code{print} command with a slash and a format letter. The format
10707 letters supported are:
10711 Regard the bits of the value as an integer, and print the integer in
10715 Print as integer in signed decimal.
10718 Print as integer in unsigned decimal.
10721 Print as integer in octal.
10724 Print as integer in binary. The letter @samp{t} stands for ``two''.
10725 @footnote{@samp{b} cannot be used because these format letters are also
10726 used with the @code{x} command, where @samp{b} stands for ``byte'';
10727 see @ref{Memory,,Examining Memory}.}
10730 @cindex unknown address, locating
10731 @cindex locate address
10732 Print as an address, both absolute in hexadecimal and as an offset from
10733 the nearest preceding symbol. You can use this format used to discover
10734 where (in what function) an unknown address is located:
10737 (@value{GDBP}) p/a 0x54320
10738 $3 = 0x54320 <_initialize_vx+396>
10742 The command @code{info symbol 0x54320} yields similar results.
10743 @xref{Symbols, info symbol}.
10746 Regard as an integer and print it as a character constant. This
10747 prints both the numerical value and its character representation. The
10748 character representation is replaced with the octal escape @samp{\nnn}
10749 for characters outside the 7-bit @sc{ascii} range.
10751 Without this format, @value{GDBN} displays @code{char},
10752 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10753 constants. Single-byte members of vectors are displayed as integer
10757 Regard the bits of the value as a floating point number and print
10758 using typical floating point syntax.
10761 @cindex printing strings
10762 @cindex printing byte arrays
10763 Regard as a string, if possible. With this format, pointers to single-byte
10764 data are displayed as null-terminated strings and arrays of single-byte data
10765 are displayed as fixed-length strings. Other values are displayed in their
10768 Without this format, @value{GDBN} displays pointers to and arrays of
10769 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10770 strings. Single-byte members of a vector are displayed as an integer
10774 Like @samp{x} formatting, the value is treated as an integer and
10775 printed as hexadecimal, but leading zeros are printed to pad the value
10776 to the size of the integer type.
10779 @cindex raw printing
10780 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10781 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10782 Printing}). This typically results in a higher-level display of the
10783 value's contents. The @samp{r} format bypasses any Python
10784 pretty-printer which might exist.
10787 For example, to print the program counter in hex (@pxref{Registers}), type
10794 Note that no space is required before the slash; this is because command
10795 names in @value{GDBN} cannot contain a slash.
10797 To reprint the last value in the value history with a different format,
10798 you can use the @code{print} command with just a format and no
10799 expression. For example, @samp{p/x} reprints the last value in hex.
10802 @section Examining Memory
10804 You can use the command @code{x} (for ``examine'') to examine memory in
10805 any of several formats, independently of your program's data types.
10807 @cindex examining memory
10809 @kindex x @r{(examine memory)}
10810 @item x/@var{nfu} @var{addr}
10811 @itemx x @var{addr}
10813 Use the @code{x} command to examine memory.
10816 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10817 much memory to display and how to format it; @var{addr} is an
10818 expression giving the address where you want to start displaying memory.
10819 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10820 Several commands set convenient defaults for @var{addr}.
10823 @item @var{n}, the repeat count
10824 The repeat count is a decimal integer; the default is 1. It specifies
10825 how much memory (counting by units @var{u}) to display. If a negative
10826 number is specified, memory is examined backward from @var{addr}.
10827 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10830 @item @var{f}, the display format
10831 The display format is one of the formats used by @code{print}
10832 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10833 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
10834 @samp{m} (for displaying memory tags).
10835 The default is @samp{x} (hexadecimal) initially. The default changes
10836 each time you use either @code{x} or @code{print}.
10838 @item @var{u}, the unit size
10839 The unit size is any of
10845 Halfwords (two bytes).
10847 Words (four bytes). This is the initial default.
10849 Giant words (eight bytes).
10852 Each time you specify a unit size with @code{x}, that size becomes the
10853 default unit the next time you use @code{x}. For the @samp{i} format,
10854 the unit size is ignored and is normally not written. For the @samp{s} format,
10855 the unit size defaults to @samp{b}, unless it is explicitly given.
10856 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10857 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10858 Note that the results depend on the programming language of the
10859 current compilation unit. If the language is C, the @samp{s}
10860 modifier will use the UTF-16 encoding while @samp{w} will use
10861 UTF-32. The encoding is set by the programming language and cannot
10864 @item @var{addr}, starting display address
10865 @var{addr} is the address where you want @value{GDBN} to begin displaying
10866 memory. The expression need not have a pointer value (though it may);
10867 it is always interpreted as an integer address of a byte of memory.
10868 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10869 @var{addr} is usually just after the last address examined---but several
10870 other commands also set the default address: @code{info breakpoints} (to
10871 the address of the last breakpoint listed), @code{info line} (to the
10872 starting address of a line), and @code{print} (if you use it to display
10873 a value from memory).
10876 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10877 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10878 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10879 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10880 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10882 You can also specify a negative repeat count to examine memory backward
10883 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10884 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10886 Since the letters indicating unit sizes are all distinct from the
10887 letters specifying output formats, you do not have to remember whether
10888 unit size or format comes first; either order works. The output
10889 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10890 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10892 Even though the unit size @var{u} is ignored for the formats @samp{s}
10893 and @samp{i}, you might still want to use a count @var{n}; for example,
10894 @samp{3i} specifies that you want to see three machine instructions,
10895 including any operands. For convenience, especially when used with
10896 the @code{display} command, the @samp{i} format also prints branch delay
10897 slot instructions, if any, beyond the count specified, which immediately
10898 follow the last instruction that is within the count. The command
10899 @code{disassemble} gives an alternative way of inspecting machine
10900 instructions; see @ref{Machine Code,,Source and Machine Code}.
10902 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10903 the command displays null-terminated strings or instructions before the given
10904 address as many as the absolute value of the given number. For the @samp{i}
10905 format, we use line number information in the debug info to accurately locate
10906 instruction boundaries while disassembling backward. If line info is not
10907 available, the command stops examining memory with an error message.
10909 All the defaults for the arguments to @code{x} are designed to make it
10910 easy to continue scanning memory with minimal specifications each time
10911 you use @code{x}. For example, after you have inspected three machine
10912 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10913 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10914 the repeat count @var{n} is used again; the other arguments default as
10915 for successive uses of @code{x}.
10917 When examining machine instructions, the instruction at current program
10918 counter is shown with a @code{=>} marker. For example:
10921 (@value{GDBP}) x/5i $pc-6
10922 0x804837f <main+11>: mov %esp,%ebp
10923 0x8048381 <main+13>: push %ecx
10924 0x8048382 <main+14>: sub $0x4,%esp
10925 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10926 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10929 If the architecture supports memory tagging, the tags can be displayed by
10930 using @samp{m}. @xref{Memory Tagging}.
10932 The information will be displayed once per granule size
10933 (the amount of bytes a particular memory tag covers). For example, AArch64
10934 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
10936 Due to the way @value{GDBN} prints information with the @code{x} command (not
10937 aligned to a particular boundary), the tag information will refer to the
10938 initial address displayed on a particular line. If a memory tag boundary
10939 is crossed in the middle of a line displayed by the @code{x} command, it
10940 will be displayed on the next line.
10942 The @samp{m} format doesn't affect any other specified formats that were
10943 passed to the @code{x} command.
10945 @cindex @code{$_}, @code{$__}, and value history
10946 The addresses and contents printed by the @code{x} command are not saved
10947 in the value history because there is often too much of them and they
10948 would get in the way. Instead, @value{GDBN} makes these values available for
10949 subsequent use in expressions as values of the convenience variables
10950 @code{$_} and @code{$__}. After an @code{x} command, the last address
10951 examined is available for use in expressions in the convenience variable
10952 @code{$_}. The contents of that address, as examined, are available in
10953 the convenience variable @code{$__}.
10955 If the @code{x} command has a repeat count, the address and contents saved
10956 are from the last memory unit printed; this is not the same as the last
10957 address printed if several units were printed on the last line of output.
10959 @anchor{addressable memory unit}
10960 @cindex addressable memory unit
10961 Most targets have an addressable memory unit size of 8 bits. This means
10962 that to each memory address are associated 8 bits of data. Some
10963 targets, however, have other addressable memory unit sizes.
10964 Within @value{GDBN} and this document, the term
10965 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10966 when explicitly referring to a chunk of data of that size. The word
10967 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10968 the addressable memory unit size of the target. For most systems,
10969 addressable memory unit is a synonym of byte.
10971 @cindex remote memory comparison
10972 @cindex target memory comparison
10973 @cindex verify remote memory image
10974 @cindex verify target memory image
10975 When you are debugging a program running on a remote target machine
10976 (@pxref{Remote Debugging}), you may wish to verify the program's image
10977 in the remote machine's memory against the executable file you
10978 downloaded to the target. Or, on any target, you may want to check
10979 whether the program has corrupted its own read-only sections. The
10980 @code{compare-sections} command is provided for such situations.
10983 @kindex compare-sections
10984 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10985 Compare the data of a loadable section @var{section-name} in the
10986 executable file of the program being debugged with the same section in
10987 the target machine's memory, and report any mismatches. With no
10988 arguments, compares all loadable sections. With an argument of
10989 @code{-r}, compares all loadable read-only sections.
10991 Note: for remote targets, this command can be accelerated if the
10992 target supports computing the CRC checksum of a block of memory
10993 (@pxref{qCRC packet}).
10996 @node Memory Tagging
10997 @section Memory Tagging
10999 Memory tagging is a memory protection technology that uses a pair of tags to
11000 validate memory accesses through pointers. The tags are integer values
11001 usually comprised of a few bits, depending on the architecture.
11003 There are two types of tags that are used in this setup: logical and
11004 allocation. A logical tag is stored in the pointers themselves, usually at the
11005 higher bits of the pointers. An allocation tag is the tag associated
11006 with particular ranges of memory in the physical address space, against which
11007 the logical tags from pointers are compared.
11009 The pointer tag (logical tag) must match the memory tag (allocation tag)
11010 for the memory access to be valid. If the logical tag does not match the
11011 allocation tag, that will raise a memory violation.
11013 Allocation tags cover multiple contiguous bytes of physical memory. This
11014 range of bytes is called a memory tag granule and is architecture-specific.
11015 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11016 tag spans 16 bytes of memory.
11018 If the underlying architecture supports memory tagging, like AArch64 MTE
11019 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11020 against memory allocation tags.
11022 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11023 display tag information when appropriate, and a command prefix of
11024 @code{memory-tag} gives access to the various memory tagging commands.
11026 The @code{memory-tag} commands are the following:
11029 @kindex memory-tag print-logical-tag
11030 @item memory-tag print-logical-tag @var{pointer_expression}
11031 Print the logical tag stored in @var{pointer_expression}.
11032 @kindex memory-tag with-logical-tag
11033 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11034 Print the pointer given by @var{pointer_expression}, augmented with a logical
11035 tag of @var{tag_bytes}.
11036 @kindex memory-tag print-allocation-tag
11037 @item memory-tag print-allocation-tag @var{address_expression}
11038 Print the allocation tag associated with the memory address given by
11039 @var{address_expression}.
11040 @kindex memory-tag setatag
11041 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11042 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11043 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11044 @kindex memory-tag check
11045 @item memory-tag check @var{pointer_expression}
11046 Check if the logical tag in the pointer given by @var{pointer_expression}
11047 matches the allocation tag for the memory referenced by the pointer.
11049 This essentially emulates the hardware validation that is done when tagged
11050 memory is accessed through a pointer, but does not cause a memory fault as
11051 it would during hardware validation.
11053 It can be used to inspect potential memory tagging violations in the running
11054 process, before any faults get triggered.
11058 @section Automatic Display
11059 @cindex automatic display
11060 @cindex display of expressions
11062 If you find that you want to print the value of an expression frequently
11063 (to see how it changes), you might want to add it to the @dfn{automatic
11064 display list} so that @value{GDBN} prints its value each time your program stops.
11065 Each expression added to the list is given a number to identify it;
11066 to remove an expression from the list, you specify that number.
11067 The automatic display looks like this:
11071 3: bar[5] = (struct hack *) 0x3804
11075 This display shows item numbers, expressions and their current values. As with
11076 displays you request manually using @code{x} or @code{print}, you can
11077 specify the output format you prefer; in fact, @code{display} decides
11078 whether to use @code{print} or @code{x} depending your format
11079 specification---it uses @code{x} if you specify either the @samp{i}
11080 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11084 @item display @var{expr}
11085 Add the expression @var{expr} to the list of expressions to display
11086 each time your program stops. @xref{Expressions, ,Expressions}.
11088 @code{display} does not repeat if you press @key{RET} again after using it.
11090 @item display/@var{fmt} @var{expr}
11091 For @var{fmt} specifying only a display format and not a size or
11092 count, add the expression @var{expr} to the auto-display list but
11093 arrange to display it each time in the specified format @var{fmt}.
11094 @xref{Output Formats,,Output Formats}.
11096 @item display/@var{fmt} @var{addr}
11097 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11098 number of units, add the expression @var{addr} as a memory address to
11099 be examined each time your program stops. Examining means in effect
11100 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11103 For example, @samp{display/i $pc} can be helpful, to see the machine
11104 instruction about to be executed each time execution stops (@samp{$pc}
11105 is a common name for the program counter; @pxref{Registers, ,Registers}).
11108 @kindex delete display
11110 @item undisplay @var{dnums}@dots{}
11111 @itemx delete display @var{dnums}@dots{}
11112 Remove items from the list of expressions to display. Specify the
11113 numbers of the displays that you want affected with the command
11114 argument @var{dnums}. It can be a single display number, one of the
11115 numbers shown in the first field of the @samp{info display} display;
11116 or it could be a range of display numbers, as in @code{2-4}.
11118 @code{undisplay} does not repeat if you press @key{RET} after using it.
11119 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11121 @kindex disable display
11122 @item disable display @var{dnums}@dots{}
11123 Disable the display of item numbers @var{dnums}. A disabled display
11124 item is not printed automatically, but is not forgotten. It may be
11125 enabled again later. Specify the numbers of the displays that you
11126 want affected with the command argument @var{dnums}. It can be a
11127 single display number, one of the numbers shown in the first field of
11128 the @samp{info display} display; or it could be a range of display
11129 numbers, as in @code{2-4}.
11131 @kindex enable display
11132 @item enable display @var{dnums}@dots{}
11133 Enable display of item numbers @var{dnums}. It becomes effective once
11134 again in auto display of its expression, until you specify otherwise.
11135 Specify the numbers of the displays that you want affected with the
11136 command argument @var{dnums}. It can be a single display number, one
11137 of the numbers shown in the first field of the @samp{info display}
11138 display; or it could be a range of display numbers, as in @code{2-4}.
11141 Display the current values of the expressions on the list, just as is
11142 done when your program stops.
11144 @kindex info display
11146 Print the list of expressions previously set up to display
11147 automatically, each one with its item number, but without showing the
11148 values. This includes disabled expressions, which are marked as such.
11149 It also includes expressions which would not be displayed right now
11150 because they refer to automatic variables not currently available.
11153 @cindex display disabled out of scope
11154 If a display expression refers to local variables, then it does not make
11155 sense outside the lexical context for which it was set up. Such an
11156 expression is disabled when execution enters a context where one of its
11157 variables is not defined. For example, if you give the command
11158 @code{display last_char} while inside a function with an argument
11159 @code{last_char}, @value{GDBN} displays this argument while your program
11160 continues to stop inside that function. When it stops elsewhere---where
11161 there is no variable @code{last_char}---the display is disabled
11162 automatically. The next time your program stops where @code{last_char}
11163 is meaningful, you can enable the display expression once again.
11165 @node Print Settings
11166 @section Print Settings
11168 @cindex format options
11169 @cindex print settings
11170 @value{GDBN} provides the following ways to control how arrays, structures,
11171 and symbols are printed.
11174 These settings are useful for debugging programs in any language:
11178 @anchor{set print address}
11179 @item set print address
11180 @itemx set print address on
11181 @cindex print/don't print memory addresses
11182 @value{GDBN} prints memory addresses showing the location of stack
11183 traces, structure values, pointer values, breakpoints, and so forth,
11184 even when it also displays the contents of those addresses. The default
11185 is @code{on}. For example, this is what a stack frame display looks like with
11186 @code{set print address on}:
11191 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11193 530 if (lquote != def_lquote)
11197 @item set print address off
11198 Do not print addresses when displaying their contents. For example,
11199 this is the same stack frame displayed with @code{set print address off}:
11203 (@value{GDBP}) set print addr off
11205 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11206 530 if (lquote != def_lquote)
11210 You can use @samp{set print address off} to eliminate all machine
11211 dependent displays from the @value{GDBN} interface. For example, with
11212 @code{print address off}, you should get the same text for backtraces on
11213 all machines---whether or not they involve pointer arguments.
11216 @item show print address
11217 Show whether or not addresses are to be printed.
11220 When @value{GDBN} prints a symbolic address, it normally prints the
11221 closest earlier symbol plus an offset. If that symbol does not uniquely
11222 identify the address (for example, it is a name whose scope is a single
11223 source file), you may need to clarify. One way to do this is with
11224 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11225 you can set @value{GDBN} to print the source file and line number when
11226 it prints a symbolic address:
11229 @item set print symbol-filename on
11230 @cindex source file and line of a symbol
11231 @cindex symbol, source file and line
11232 Tell @value{GDBN} to print the source file name and line number of a
11233 symbol in the symbolic form of an address.
11235 @item set print symbol-filename off
11236 Do not print source file name and line number of a symbol. This is the
11239 @item show print symbol-filename
11240 Show whether or not @value{GDBN} will print the source file name and
11241 line number of a symbol in the symbolic form of an address.
11244 Another situation where it is helpful to show symbol filenames and line
11245 numbers is when disassembling code; @value{GDBN} shows you the line
11246 number and source file that corresponds to each instruction.
11248 Also, you may wish to see the symbolic form only if the address being
11249 printed is reasonably close to the closest earlier symbol:
11252 @item set print max-symbolic-offset @var{max-offset}
11253 @itemx set print max-symbolic-offset unlimited
11254 @cindex maximum value for offset of closest symbol
11255 Tell @value{GDBN} to only display the symbolic form of an address if the
11256 offset between the closest earlier symbol and the address is less than
11257 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11258 to always print the symbolic form of an address if any symbol precedes
11259 it. Zero is equivalent to @code{unlimited}.
11261 @item show print max-symbolic-offset
11262 Ask how large the maximum offset is that @value{GDBN} prints in a
11266 @cindex wild pointer, interpreting
11267 @cindex pointer, finding referent
11268 If you have a pointer and you are not sure where it points, try
11269 @samp{set print symbol-filename on}. Then you can determine the name
11270 and source file location of the variable where it points, using
11271 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11272 For example, here @value{GDBN} shows that a variable @code{ptt} points
11273 at another variable @code{t}, defined in @file{hi2.c}:
11276 (@value{GDBP}) set print symbol-filename on
11277 (@value{GDBP}) p/a ptt
11278 $4 = 0xe008 <t in hi2.c>
11282 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11283 does not show the symbol name and filename of the referent, even with
11284 the appropriate @code{set print} options turned on.
11287 You can also enable @samp{/a}-like formatting all the time using
11288 @samp{set print symbol on}:
11290 @anchor{set print symbol}
11292 @item set print symbol on
11293 Tell @value{GDBN} to print the symbol corresponding to an address, if
11296 @item set print symbol off
11297 Tell @value{GDBN} not to print the symbol corresponding to an
11298 address. In this mode, @value{GDBN} will still print the symbol
11299 corresponding to pointers to functions. This is the default.
11301 @item show print symbol
11302 Show whether @value{GDBN} will display the symbol corresponding to an
11306 Other settings control how different kinds of objects are printed:
11309 @anchor{set print array}
11310 @item set print array
11311 @itemx set print array on
11312 @cindex pretty print arrays
11313 Pretty print arrays. This format is more convenient to read,
11314 but uses more space. The default is off.
11316 @item set print array off
11317 Return to compressed format for arrays.
11319 @item show print array
11320 Show whether compressed or pretty format is selected for displaying
11323 @cindex print array indexes
11324 @anchor{set print array-indexes}
11325 @item set print array-indexes
11326 @itemx set print array-indexes on
11327 Print the index of each element when displaying arrays. May be more
11328 convenient to locate a given element in the array or quickly find the
11329 index of a given element in that printed array. The default is off.
11331 @item set print array-indexes off
11332 Stop printing element indexes when displaying arrays.
11334 @item show print array-indexes
11335 Show whether the index of each element is printed when displaying
11338 @anchor{set print elements}
11339 @item set print elements @var{number-of-elements}
11340 @itemx set print elements unlimited
11341 @cindex number of array elements to print
11342 @cindex limit on number of printed array elements
11343 Set a limit on how many elements of an array @value{GDBN} will print.
11344 If @value{GDBN} is printing a large array, it stops printing after it has
11345 printed the number of elements set by the @code{set print elements} command.
11346 This limit also applies to the display of strings.
11347 When @value{GDBN} starts, this limit is set to 200.
11348 Setting @var{number-of-elements} to @code{unlimited} or zero means
11349 that the number of elements to print is unlimited.
11351 @item show print elements
11352 Display the number of elements of a large array that @value{GDBN} will print.
11353 If the number is 0, then the printing is unlimited.
11355 @anchor{set print frame-arguments}
11356 @item set print frame-arguments @var{value}
11357 @kindex set print frame-arguments
11358 @cindex printing frame argument values
11359 @cindex print all frame argument values
11360 @cindex print frame argument values for scalars only
11361 @cindex do not print frame arguments
11362 This command allows to control how the values of arguments are printed
11363 when the debugger prints a frame (@pxref{Frames}). The possible
11368 The values of all arguments are printed.
11371 Print the value of an argument only if it is a scalar. The value of more
11372 complex arguments such as arrays, structures, unions, etc, is replaced
11373 by @code{@dots{}}. This is the default. Here is an example where
11374 only scalar arguments are shown:
11377 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11382 None of the argument values are printed. Instead, the value of each argument
11383 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11386 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11391 Only the presence of arguments is indicated by @code{@dots{}}.
11392 The @code{@dots{}} are not printed for function without any arguments.
11393 None of the argument names and values are printed.
11394 In this case, the example above now becomes:
11397 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11402 By default, only scalar arguments are printed. This command can be used
11403 to configure the debugger to print the value of all arguments, regardless
11404 of their type. However, it is often advantageous to not print the value
11405 of more complex parameters. For instance, it reduces the amount of
11406 information printed in each frame, making the backtrace more readable.
11407 Also, it improves performance when displaying Ada frames, because
11408 the computation of large arguments can sometimes be CPU-intensive,
11409 especially in large applications. Setting @code{print frame-arguments}
11410 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11411 this computation, thus speeding up the display of each Ada frame.
11413 @item show print frame-arguments
11414 Show how the value of arguments should be displayed when printing a frame.
11416 @anchor{set print raw-frame-arguments}
11417 @item set print raw-frame-arguments on
11418 Print frame arguments in raw, non pretty-printed, form.
11420 @item set print raw-frame-arguments off
11421 Print frame arguments in pretty-printed form, if there is a pretty-printer
11422 for the value (@pxref{Pretty Printing}),
11423 otherwise print the value in raw form.
11424 This is the default.
11426 @item show print raw-frame-arguments
11427 Show whether to print frame arguments in raw form.
11429 @anchor{set print entry-values}
11430 @item set print entry-values @var{value}
11431 @kindex set print entry-values
11432 Set printing of frame argument values at function entry. In some cases
11433 @value{GDBN} can determine the value of function argument which was passed by
11434 the function caller, even if the value was modified inside the called function
11435 and therefore is different. With optimized code, the current value could be
11436 unavailable, but the entry value may still be known.
11438 The default value is @code{default} (see below for its description). Older
11439 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11440 this feature will behave in the @code{default} setting the same way as with the
11443 This functionality is currently supported only by DWARF 2 debugging format and
11444 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11445 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11448 The @var{value} parameter can be one of the following:
11452 Print only actual parameter values, never print values from function entry
11456 #0 different (val=6)
11457 #0 lost (val=<optimized out>)
11459 #0 invalid (val=<optimized out>)
11463 Print only parameter values from function entry point. The actual parameter
11464 values are never printed.
11466 #0 equal (val@@entry=5)
11467 #0 different (val@@entry=5)
11468 #0 lost (val@@entry=5)
11469 #0 born (val@@entry=<optimized out>)
11470 #0 invalid (val@@entry=<optimized out>)
11474 Print only parameter values from function entry point. If value from function
11475 entry point is not known while the actual value is known, print the actual
11476 value for such parameter.
11478 #0 equal (val@@entry=5)
11479 #0 different (val@@entry=5)
11480 #0 lost (val@@entry=5)
11482 #0 invalid (val@@entry=<optimized out>)
11486 Print actual parameter values. If actual parameter value is not known while
11487 value from function entry point is known, print the entry point value for such
11491 #0 different (val=6)
11492 #0 lost (val@@entry=5)
11494 #0 invalid (val=<optimized out>)
11498 Always print both the actual parameter value and its value from function entry
11499 point, even if values of one or both are not available due to compiler
11502 #0 equal (val=5, val@@entry=5)
11503 #0 different (val=6, val@@entry=5)
11504 #0 lost (val=<optimized out>, val@@entry=5)
11505 #0 born (val=10, val@@entry=<optimized out>)
11506 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11510 Print the actual parameter value if it is known and also its value from
11511 function entry point if it is known. If neither is known, print for the actual
11512 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11513 values are known and identical, print the shortened
11514 @code{param=param@@entry=VALUE} notation.
11516 #0 equal (val=val@@entry=5)
11517 #0 different (val=6, val@@entry=5)
11518 #0 lost (val@@entry=5)
11520 #0 invalid (val=<optimized out>)
11524 Always print the actual parameter value. Print also its value from function
11525 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11526 if both values are known and identical, print the shortened
11527 @code{param=param@@entry=VALUE} notation.
11529 #0 equal (val=val@@entry=5)
11530 #0 different (val=6, val@@entry=5)
11531 #0 lost (val=<optimized out>, val@@entry=5)
11533 #0 invalid (val=<optimized out>)
11537 For analysis messages on possible failures of frame argument values at function
11538 entry resolution see @ref{set debug entry-values}.
11540 @item show print entry-values
11541 Show the method being used for printing of frame argument values at function
11544 @anchor{set print frame-info}
11545 @item set print frame-info @var{value}
11546 @kindex set print frame-info
11547 @cindex printing frame information
11548 @cindex frame information, printing
11549 This command allows to control the information printed when
11550 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11551 for a general explanation about frames and frame information.
11552 Note that some other settings (such as @code{set print frame-arguments}
11553 and @code{set print address}) are also influencing if and how some frame
11554 information is displayed. In particular, the frame program counter is never
11555 printed if @code{set print address} is off.
11557 The possible values for @code{set print frame-info} are:
11559 @item short-location
11560 Print the frame level, the program counter (if not at the
11561 beginning of the location source line), the function, the function
11564 Same as @code{short-location} but also print the source file and source line
11566 @item location-and-address
11567 Same as @code{location} but print the program counter even if located at the
11568 beginning of the location source line.
11570 Print the program counter (if not at the beginning of the location
11571 source line), the line number and the source line.
11572 @item source-and-location
11573 Print what @code{location} and @code{source-line} are printing.
11575 The information printed for a frame is decided automatically
11576 by the @value{GDBN} command that prints a frame.
11577 For example, @code{frame} prints the information printed by
11578 @code{source-and-location} while @code{stepi} will switch between
11579 @code{source-line} and @code{source-and-location} depending on the program
11581 The default value is @code{auto}.
11584 @anchor{set print repeats}
11585 @item set print repeats @var{number-of-repeats}
11586 @itemx set print repeats unlimited
11587 @cindex repeated array elements
11588 Set the threshold for suppressing display of repeated array
11589 elements. When the number of consecutive identical elements of an
11590 array exceeds the threshold, @value{GDBN} prints the string
11591 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11592 identical repetitions, instead of displaying the identical elements
11593 themselves. Setting the threshold to @code{unlimited} or zero will
11594 cause all elements to be individually printed. The default threshold
11597 @item show print repeats
11598 Display the current threshold for printing repeated identical
11601 @anchor{set print max-depth}
11602 @item set print max-depth @var{depth}
11603 @item set print max-depth unlimited
11604 @cindex printing nested structures
11605 Set the threshold after which nested structures are replaced with
11606 ellipsis, this can make visualising deeply nested structures easier.
11608 For example, given this C code
11611 typedef struct s1 @{ int a; @} s1;
11612 typedef struct s2 @{ s1 b; @} s2;
11613 typedef struct s3 @{ s2 c; @} s3;
11614 typedef struct s4 @{ s3 d; @} s4;
11616 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11619 The following table shows how different values of @var{depth} will
11620 effect how @code{var} is printed by @value{GDBN}:
11622 @multitable @columnfractions .3 .7
11623 @headitem @var{depth} setting @tab Result of @samp{p var}
11625 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11627 @tab @code{$1 = @{...@}}
11629 @tab @code{$1 = @{d = @{...@}@}}
11631 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11633 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11635 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11638 To see the contents of structures that have been hidden the user can
11639 either increase the print max-depth, or they can print the elements of
11640 the structure that are visible, for example
11643 (gdb) set print max-depth 2
11645 $1 = @{d = @{c = @{...@}@}@}
11647 $2 = @{c = @{b = @{...@}@}@}
11649 $3 = @{b = @{a = 3@}@}
11652 The pattern used to replace nested structures varies based on
11653 language, for most languages @code{@{...@}} is used, but Fortran uses
11656 @item show print max-depth
11657 Display the current threshold after which nested structures are
11658 replaces with ellipsis.
11660 @anchor{set print memory-tag-violations}
11661 @cindex printing memory tag violation information
11662 @item set print memory-tag-violations
11663 @itemx set print memory-tag-violations on
11664 Cause @value{GDBN} to display additional information about memory tag violations
11665 when printing pointers and addresses.
11667 @item set print memory-tag-violations off
11668 Stop printing memory tag violation information.
11670 @item show print memory-tag-violations
11671 Show whether memory tag violation information is displayed when printing
11672 pointers and addresses.
11674 @anchor{set print null-stop}
11675 @item set print null-stop
11676 @cindex @sc{null} elements in arrays
11677 Cause @value{GDBN} to stop printing the characters of an array when the first
11678 @sc{null} is encountered. This is useful when large arrays actually
11679 contain only short strings.
11680 The default is off.
11682 @item show print null-stop
11683 Show whether @value{GDBN} stops printing an array on the first
11684 @sc{null} character.
11686 @anchor{set print pretty}
11687 @item set print pretty on
11688 @cindex print structures in indented form
11689 @cindex indentation in structure display
11690 Cause @value{GDBN} to print structures in an indented format with one member
11691 per line, like this:
11706 @item set print pretty off
11707 Cause @value{GDBN} to print structures in a compact format, like this:
11711 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11712 meat = 0x54 "Pork"@}
11717 This is the default format.
11719 @item show print pretty
11720 Show which format @value{GDBN} is using to print structures.
11722 @anchor{set print raw-values}
11723 @item set print raw-values on
11724 Print values in raw form, without applying the pretty
11725 printers for the value.
11727 @item set print raw-values off
11728 Print values in pretty-printed form, if there is a pretty-printer
11729 for the value (@pxref{Pretty Printing}),
11730 otherwise print the value in raw form.
11732 The default setting is ``off''.
11734 @item show print raw-values
11735 Show whether to print values in raw form.
11737 @item set print sevenbit-strings on
11738 @cindex eight-bit characters in strings
11739 @cindex octal escapes in strings
11740 Print using only seven-bit characters; if this option is set,
11741 @value{GDBN} displays any eight-bit characters (in strings or
11742 character values) using the notation @code{\}@var{nnn}. This setting is
11743 best if you are working in English (@sc{ascii}) and you use the
11744 high-order bit of characters as a marker or ``meta'' bit.
11746 @item set print sevenbit-strings off
11747 Print full eight-bit characters. This allows the use of more
11748 international character sets, and is the default.
11750 @item show print sevenbit-strings
11751 Show whether or not @value{GDBN} is printing only seven-bit characters.
11753 @anchor{set print union}
11754 @item set print union on
11755 @cindex unions in structures, printing
11756 Tell @value{GDBN} to print unions which are contained in structures
11757 and other unions. This is the default setting.
11759 @item set print union off
11760 Tell @value{GDBN} not to print unions which are contained in
11761 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11764 @item show print union
11765 Ask @value{GDBN} whether or not it will print unions which are contained in
11766 structures and other unions.
11768 For example, given the declarations
11771 typedef enum @{Tree, Bug@} Species;
11772 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11773 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11784 struct thing foo = @{Tree, @{Acorn@}@};
11788 with @code{set print union on} in effect @samp{p foo} would print
11791 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11795 and with @code{set print union off} in effect it would print
11798 $1 = @{it = Tree, form = @{...@}@}
11802 @code{set print union} affects programs written in C-like languages
11808 These settings are of interest when debugging C@t{++} programs:
11811 @cindex demangling C@t{++} names
11812 @item set print demangle
11813 @itemx set print demangle on
11814 Print C@t{++} names in their source form rather than in the encoded
11815 (``mangled'') form passed to the assembler and linker for type-safe
11816 linkage. The default is on.
11818 @item show print demangle
11819 Show whether C@t{++} names are printed in mangled or demangled form.
11821 @item set print asm-demangle
11822 @itemx set print asm-demangle on
11823 Print C@t{++} names in their source form rather than their mangled form, even
11824 in assembler code printouts such as instruction disassemblies.
11825 The default is off.
11827 @item show print asm-demangle
11828 Show whether C@t{++} names in assembly listings are printed in mangled
11831 @cindex C@t{++} symbol decoding style
11832 @cindex symbol decoding style, C@t{++}
11833 @kindex set demangle-style
11834 @item set demangle-style @var{style}
11835 Choose among several encoding schemes used by different compilers to represent
11836 C@t{++} names. If you omit @var{style}, you will see a list of possible
11837 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11838 decoding style by inspecting your program.
11840 @item show demangle-style
11841 Display the encoding style currently in use for decoding C@t{++} symbols.
11843 @anchor{set print object}
11844 @item set print object
11845 @itemx set print object on
11846 @cindex derived type of an object, printing
11847 @cindex display derived types
11848 When displaying a pointer to an object, identify the @emph{actual}
11849 (derived) type of the object rather than the @emph{declared} type, using
11850 the virtual function table. Note that the virtual function table is
11851 required---this feature can only work for objects that have run-time
11852 type identification; a single virtual method in the object's declared
11853 type is sufficient. Note that this setting is also taken into account when
11854 working with variable objects via MI (@pxref{GDB/MI}).
11856 @item set print object off
11857 Display only the declared type of objects, without reference to the
11858 virtual function table. This is the default setting.
11860 @item show print object
11861 Show whether actual, or declared, object types are displayed.
11863 @anchor{set print static-members}
11864 @item set print static-members
11865 @itemx set print static-members on
11866 @cindex static members of C@t{++} objects
11867 Print static members when displaying a C@t{++} object. The default is on.
11869 @item set print static-members off
11870 Do not print static members when displaying a C@t{++} object.
11872 @item show print static-members
11873 Show whether C@t{++} static members are printed or not.
11875 @item set print pascal_static-members
11876 @itemx set print pascal_static-members on
11877 @cindex static members of Pascal objects
11878 @cindex Pascal objects, static members display
11879 Print static members when displaying a Pascal object. The default is on.
11881 @item set print pascal_static-members off
11882 Do not print static members when displaying a Pascal object.
11884 @item show print pascal_static-members
11885 Show whether Pascal static members are printed or not.
11887 @c These don't work with HP ANSI C++ yet.
11888 @anchor{set print vtbl}
11889 @item set print vtbl
11890 @itemx set print vtbl on
11891 @cindex pretty print C@t{++} virtual function tables
11892 @cindex virtual functions (C@t{++}) display
11893 @cindex VTBL display
11894 Pretty print C@t{++} virtual function tables. The default is off.
11895 (The @code{vtbl} commands do not work on programs compiled with the HP
11896 ANSI C@t{++} compiler (@code{aCC}).)
11898 @item set print vtbl off
11899 Do not pretty print C@t{++} virtual function tables.
11901 @item show print vtbl
11902 Show whether C@t{++} virtual function tables are pretty printed, or not.
11905 @node Pretty Printing
11906 @section Pretty Printing
11908 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11909 Python code. It greatly simplifies the display of complex objects. This
11910 mechanism works for both MI and the CLI.
11913 * Pretty-Printer Introduction:: Introduction to pretty-printers
11914 * Pretty-Printer Example:: An example pretty-printer
11915 * Pretty-Printer Commands:: Pretty-printer commands
11918 @node Pretty-Printer Introduction
11919 @subsection Pretty-Printer Introduction
11921 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11922 registered for the value. If there is then @value{GDBN} invokes the
11923 pretty-printer to print the value. Otherwise the value is printed normally.
11925 Pretty-printers are normally named. This makes them easy to manage.
11926 The @samp{info pretty-printer} command will list all the installed
11927 pretty-printers with their names.
11928 If a pretty-printer can handle multiple data types, then its
11929 @dfn{subprinters} are the printers for the individual data types.
11930 Each such subprinter has its own name.
11931 The format of the name is @var{printer-name};@var{subprinter-name}.
11933 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11934 Typically they are automatically loaded and registered when the corresponding
11935 debug information is loaded, thus making them available without having to
11936 do anything special.
11938 There are three places where a pretty-printer can be registered.
11942 Pretty-printers registered globally are available when debugging
11946 Pretty-printers registered with a program space are available only
11947 when debugging that program.
11948 @xref{Progspaces In Python}, for more details on program spaces in Python.
11951 Pretty-printers registered with an objfile are loaded and unloaded
11952 with the corresponding objfile (e.g., shared library).
11953 @xref{Objfiles In Python}, for more details on objfiles in Python.
11956 @xref{Selecting Pretty-Printers}, for further information on how
11957 pretty-printers are selected,
11959 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11962 @node Pretty-Printer Example
11963 @subsection Pretty-Printer Example
11965 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11968 (@value{GDBP}) print s
11970 static npos = 4294967295,
11972 <std::allocator<char>> = @{
11973 <__gnu_cxx::new_allocator<char>> = @{
11974 <No data fields>@}, <No data fields>
11976 members of std::basic_string<char, std::char_traits<char>,
11977 std::allocator<char> >::_Alloc_hider:
11978 _M_p = 0x804a014 "abcd"
11983 With a pretty-printer for @code{std::string} only the contents are printed:
11986 (@value{GDBP}) print s
11990 @node Pretty-Printer Commands
11991 @subsection Pretty-Printer Commands
11992 @cindex pretty-printer commands
11995 @kindex info pretty-printer
11996 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11997 Print the list of installed pretty-printers.
11998 This includes disabled pretty-printers, which are marked as such.
12000 @var{object-regexp} is a regular expression matching the objects
12001 whose pretty-printers to list.
12002 Objects can be @code{global}, the program space's file
12003 (@pxref{Progspaces In Python}),
12004 and the object files within that program space (@pxref{Objfiles In Python}).
12005 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12006 looks up a printer from these three objects.
12008 @var{name-regexp} is a regular expression matching the name of the printers
12011 @kindex disable pretty-printer
12012 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12013 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12014 A disabled pretty-printer is not forgotten, it may be enabled again later.
12016 @kindex enable pretty-printer
12017 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12018 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12023 Suppose we have three pretty-printers installed: one from library1.so
12024 named @code{foo} that prints objects of type @code{foo}, and
12025 another from library2.so named @code{bar} that prints two types of objects,
12026 @code{bar1} and @code{bar2}.
12029 (gdb) info pretty-printer
12036 (gdb) info pretty-printer library2
12041 (gdb) disable pretty-printer library1
12043 2 of 3 printers enabled
12044 (gdb) info pretty-printer
12051 (gdb) disable pretty-printer library2 bar;bar1
12053 1 of 3 printers enabled
12054 (gdb) info pretty-printer library2
12061 (gdb) disable pretty-printer library2 bar
12063 0 of 3 printers enabled
12064 (gdb) info pretty-printer library2
12073 Note that for @code{bar} the entire printer can be disabled,
12074 as can each individual subprinter.
12076 Printing values and frame arguments is done by default using
12077 the enabled pretty printers.
12079 The print option @code{-raw-values} and @value{GDBN} setting
12080 @code{set print raw-values} (@pxref{set print raw-values}) can be
12081 used to print values without applying the enabled pretty printers.
12083 Similarly, the backtrace option @code{-raw-frame-arguments} and
12084 @value{GDBN} setting @code{set print raw-frame-arguments}
12085 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12086 enabled pretty printers when printing frame argument values.
12088 @node Value History
12089 @section Value History
12091 @cindex value history
12092 @cindex history of values printed by @value{GDBN}
12093 Values printed by the @code{print} command are saved in the @value{GDBN}
12094 @dfn{value history}. This allows you to refer to them in other expressions.
12095 Values are kept until the symbol table is re-read or discarded
12096 (for example with the @code{file} or @code{symbol-file} commands).
12097 When the symbol table changes, the value history is discarded,
12098 since the values may contain pointers back to the types defined in the
12103 @cindex history number
12104 The values printed are given @dfn{history numbers} by which you can
12105 refer to them. These are successive integers starting with one.
12106 @code{print} shows you the history number assigned to a value by
12107 printing @samp{$@var{num} = } before the value; here @var{num} is the
12110 To refer to any previous value, use @samp{$} followed by the value's
12111 history number. The way @code{print} labels its output is designed to
12112 remind you of this. Just @code{$} refers to the most recent value in
12113 the history, and @code{$$} refers to the value before that.
12114 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12115 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12116 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12118 For example, suppose you have just printed a pointer to a structure and
12119 want to see the contents of the structure. It suffices to type
12125 If you have a chain of structures where the component @code{next} points
12126 to the next one, you can print the contents of the next one with this:
12133 You can print successive links in the chain by repeating this
12134 command---which you can do by just typing @key{RET}.
12136 Note that the history records values, not expressions. If the value of
12137 @code{x} is 4 and you type these commands:
12145 then the value recorded in the value history by the @code{print} command
12146 remains 4 even though the value of @code{x} has changed.
12149 @kindex show values
12151 Print the last ten values in the value history, with their item numbers.
12152 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12153 values} does not change the history.
12155 @item show values @var{n}
12156 Print ten history values centered on history item number @var{n}.
12158 @item show values +
12159 Print ten history values just after the values last printed. If no more
12160 values are available, @code{show values +} produces no display.
12163 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12164 same effect as @samp{show values +}.
12166 @node Convenience Vars
12167 @section Convenience Variables
12169 @cindex convenience variables
12170 @cindex user-defined variables
12171 @value{GDBN} provides @dfn{convenience variables} that you can use within
12172 @value{GDBN} to hold on to a value and refer to it later. These variables
12173 exist entirely within @value{GDBN}; they are not part of your program, and
12174 setting a convenience variable has no direct effect on further execution
12175 of your program. That is why you can use them freely.
12177 Convenience variables are prefixed with @samp{$}. Any name preceded by
12178 @samp{$} can be used for a convenience variable, unless it is one of
12179 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12180 (Value history references, in contrast, are @emph{numbers} preceded
12181 by @samp{$}. @xref{Value History, ,Value History}.)
12183 You can save a value in a convenience variable with an assignment
12184 expression, just as you would set a variable in your program.
12188 set $foo = *object_ptr
12192 would save in @code{$foo} the value contained in the object pointed to by
12195 Using a convenience variable for the first time creates it, but its
12196 value is @code{void} until you assign a new value. You can alter the
12197 value with another assignment at any time.
12199 Convenience variables have no fixed types. You can assign a convenience
12200 variable any type of value, including structures and arrays, even if
12201 that variable already has a value of a different type. The convenience
12202 variable, when used as an expression, has the type of its current value.
12205 @kindex show convenience
12206 @cindex show all user variables and functions
12207 @item show convenience
12208 Print a list of convenience variables used so far, and their values,
12209 as well as a list of the convenience functions.
12210 Abbreviated @code{show conv}.
12212 @kindex init-if-undefined
12213 @cindex convenience variables, initializing
12214 @item init-if-undefined $@var{variable} = @var{expression}
12215 Set a convenience variable if it has not already been set. This is useful
12216 for user-defined commands that keep some state. It is similar, in concept,
12217 to using local static variables with initializers in C (except that
12218 convenience variables are global). It can also be used to allow users to
12219 override default values used in a command script.
12221 If the variable is already defined then the expression is not evaluated so
12222 any side-effects do not occur.
12225 One of the ways to use a convenience variable is as a counter to be
12226 incremented or a pointer to be advanced. For example, to print
12227 a field from successive elements of an array of structures:
12231 print bar[$i++]->contents
12235 Repeat that command by typing @key{RET}.
12237 Some convenience variables are created automatically by @value{GDBN} and given
12238 values likely to be useful.
12241 @vindex $_@r{, convenience variable}
12243 The variable @code{$_} is automatically set by the @code{x} command to
12244 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12245 commands which provide a default address for @code{x} to examine also
12246 set @code{$_} to that address; these commands include @code{info line}
12247 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12248 except when set by the @code{x} command, in which case it is a pointer
12249 to the type of @code{$__}.
12251 @vindex $__@r{, convenience variable}
12253 The variable @code{$__} is automatically set by the @code{x} command
12254 to the value found in the last address examined. Its type is chosen
12255 to match the format in which the data was printed.
12258 @vindex $_exitcode@r{, convenience variable}
12259 When the program being debugged terminates normally, @value{GDBN}
12260 automatically sets this variable to the exit code of the program, and
12261 resets @code{$_exitsignal} to @code{void}.
12264 @vindex $_exitsignal@r{, convenience variable}
12265 When the program being debugged dies due to an uncaught signal,
12266 @value{GDBN} automatically sets this variable to that signal's number,
12267 and resets @code{$_exitcode} to @code{void}.
12269 To distinguish between whether the program being debugged has exited
12270 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12271 @code{$_exitsignal} is not @code{void}), the convenience function
12272 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12273 Functions}). For example, considering the following source code:
12276 #include <signal.h>
12279 main (int argc, char *argv[])
12286 A valid way of telling whether the program being debugged has exited
12287 or signalled would be:
12290 (@value{GDBP}) define has_exited_or_signalled
12291 Type commands for definition of ``has_exited_or_signalled''.
12292 End with a line saying just ``end''.
12293 >if $_isvoid ($_exitsignal)
12294 >echo The program has exited\n
12296 >echo The program has signalled\n
12302 Program terminated with signal SIGALRM, Alarm clock.
12303 The program no longer exists.
12304 (@value{GDBP}) has_exited_or_signalled
12305 The program has signalled
12308 As can be seen, @value{GDBN} correctly informs that the program being
12309 debugged has signalled, since it calls @code{raise} and raises a
12310 @code{SIGALRM} signal. If the program being debugged had not called
12311 @code{raise}, then @value{GDBN} would report a normal exit:
12314 (@value{GDBP}) has_exited_or_signalled
12315 The program has exited
12319 The variable @code{$_exception} is set to the exception object being
12320 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12322 @item $_ada_exception
12323 The variable @code{$_ada_exception} is set to the address of the
12324 exception being caught or thrown at an Ada exception-related
12325 catchpoint. @xref{Set Catchpoints}.
12328 @itemx $_probe_arg0@dots{}$_probe_arg11
12329 Arguments to a static probe. @xref{Static Probe Points}.
12332 @vindex $_sdata@r{, inspect, convenience variable}
12333 The variable @code{$_sdata} contains extra collected static tracepoint
12334 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12335 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12336 if extra static tracepoint data has not been collected.
12339 @vindex $_siginfo@r{, convenience variable}
12340 The variable @code{$_siginfo} contains extra signal information
12341 (@pxref{extra signal information}). Note that @code{$_siginfo}
12342 could be empty, if the application has not yet received any signals.
12343 For example, it will be empty before you execute the @code{run} command.
12346 @vindex $_tlb@r{, convenience variable}
12347 The variable @code{$_tlb} is automatically set when debugging
12348 applications running on MS-Windows in native mode or connected to
12349 gdbserver that supports the @code{qGetTIBAddr} request.
12350 @xref{General Query Packets}.
12351 This variable contains the address of the thread information block.
12354 The number of the current inferior. @xref{Inferiors Connections and
12355 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12358 The thread number of the current thread. @xref{thread numbers}.
12361 The global number of the current thread. @xref{global thread numbers}.
12365 @vindex $_gdb_major@r{, convenience variable}
12366 @vindex $_gdb_minor@r{, convenience variable}
12367 The major and minor version numbers of the running @value{GDBN}.
12368 Development snapshots and pretest versions have their minor version
12369 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12370 the value 12 for @code{$_gdb_minor}. These variables allow you to
12371 write scripts that work with different versions of @value{GDBN}
12372 without errors caused by features unavailable in some of those
12375 @item $_shell_exitcode
12376 @itemx $_shell_exitsignal
12377 @vindex $_shell_exitcode@r{, convenience variable}
12378 @vindex $_shell_exitsignal@r{, convenience variable}
12379 @cindex shell command, exit code
12380 @cindex shell command, exit signal
12381 @cindex exit status of shell commands
12382 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12383 shell commands. When a launched command terminates, @value{GDBN}
12384 automatically maintains the variables @code{$_shell_exitcode}
12385 and @code{$_shell_exitsignal} according to the exit status of the last
12386 launched command. These variables are set and used similarly to
12387 the variables @code{$_exitcode} and @code{$_exitsignal}.
12391 @node Convenience Funs
12392 @section Convenience Functions
12394 @cindex convenience functions
12395 @value{GDBN} also supplies some @dfn{convenience functions}. These
12396 have a syntax similar to convenience variables. A convenience
12397 function can be used in an expression just like an ordinary function;
12398 however, a convenience function is implemented internally to
12401 These functions do not require @value{GDBN} to be configured with
12402 @code{Python} support, which means that they are always available.
12406 @item $_isvoid (@var{expr})
12407 @findex $_isvoid@r{, convenience function}
12408 Return one if the expression @var{expr} is @code{void}. Otherwise it
12411 A @code{void} expression is an expression where the type of the result
12412 is @code{void}. For example, you can examine a convenience variable
12413 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12417 (@value{GDBP}) print $_exitcode
12419 (@value{GDBP}) print $_isvoid ($_exitcode)
12422 Starting program: ./a.out
12423 [Inferior 1 (process 29572) exited normally]
12424 (@value{GDBP}) print $_exitcode
12426 (@value{GDBP}) print $_isvoid ($_exitcode)
12430 In the example above, we used @code{$_isvoid} to check whether
12431 @code{$_exitcode} is @code{void} before and after the execution of the
12432 program being debugged. Before the execution there is no exit code to
12433 be examined, therefore @code{$_exitcode} is @code{void}. After the
12434 execution the program being debugged returned zero, therefore
12435 @code{$_exitcode} is zero, which means that it is not @code{void}
12438 The @code{void} expression can also be a call of a function from the
12439 program being debugged. For example, given the following function:
12448 The result of calling it inside @value{GDBN} is @code{void}:
12451 (@value{GDBP}) print foo ()
12453 (@value{GDBP}) print $_isvoid (foo ())
12455 (@value{GDBP}) set $v = foo ()
12456 (@value{GDBP}) print $v
12458 (@value{GDBP}) print $_isvoid ($v)
12462 @item $_gdb_setting_str (@var{setting})
12463 @findex $_gdb_setting_str@r{, convenience function}
12464 Return the value of the @value{GDBN} @var{setting} as a string.
12465 @var{setting} is any setting that can be used in a @code{set} or
12466 @code{show} command (@pxref{Controlling GDB}).
12469 (@value{GDBP}) show print frame-arguments
12470 Printing of non-scalar frame arguments is "scalars".
12471 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12473 (@value{GDBP}) p $_gdb_setting_str("height")
12478 @item $_gdb_setting (@var{setting})
12479 @findex $_gdb_setting@r{, convenience function}
12480 Return the value of the @value{GDBN} @var{setting}.
12481 The type of the returned value depends on the setting.
12483 The value type for boolean and auto boolean settings is @code{int}.
12484 The boolean values @code{off} and @code{on} are converted to
12485 the integer values @code{0} and @code{1}. The value @code{auto} is
12486 converted to the value @code{-1}.
12488 The value type for integer settings is either @code{unsigned int}
12489 or @code{int}, depending on the setting.
12491 Some integer settings accept an @code{unlimited} value.
12492 Depending on the setting, the @code{set} command also accepts
12493 the value @code{0} or the value @code{@minus{}1} as a synonym for
12495 For example, @code{set height unlimited} is equivalent to
12496 @code{set height 0}.
12498 Some other settings that accept the @code{unlimited} value
12499 use the value @code{0} to literally mean zero.
12500 For example, @code{set history size 0} indicates to not
12501 record any @value{GDBN} commands in the command history.
12502 For such settings, @code{@minus{}1} is the synonym
12503 for @code{unlimited}.
12505 See the documentation of the corresponding @code{set} command for
12506 the numerical value equivalent to @code{unlimited}.
12508 The @code{$_gdb_setting} function converts the unlimited value
12509 to a @code{0} or a @code{@minus{}1} value according to what the
12510 @code{set} command uses.
12514 (@value{GDBP}) p $_gdb_setting_str("height")
12516 (@value{GDBP}) p $_gdb_setting("height")
12518 (@value{GDBP}) set height unlimited
12519 (@value{GDBP}) p $_gdb_setting_str("height")
12521 (@value{GDBP}) p $_gdb_setting("height")
12525 (@value{GDBP}) p $_gdb_setting_str("history size")
12527 (@value{GDBP}) p $_gdb_setting("history size")
12529 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12531 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12537 Other setting types (enum, filename, optional filename, string, string noescape)
12538 are returned as string values.
12541 @item $_gdb_maint_setting_str (@var{setting})
12542 @findex $_gdb_maint_setting_str@r{, convenience function}
12543 Like the @code{$_gdb_setting_str} function, but works with
12544 @code{maintenance set} variables.
12546 @item $_gdb_maint_setting (@var{setting})
12547 @findex $_gdb_maint_setting@r{, convenience function}
12548 Like the @code{$_gdb_setting} function, but works with
12549 @code{maintenance set} variables.
12553 The following functions require @value{GDBN} to be configured with
12554 @code{Python} support.
12558 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12559 @findex $_memeq@r{, convenience function}
12560 Returns one if the @var{length} bytes at the addresses given by
12561 @var{buf1} and @var{buf2} are equal.
12562 Otherwise it returns zero.
12564 @item $_regex(@var{str}, @var{regex})
12565 @findex $_regex@r{, convenience function}
12566 Returns one if the string @var{str} matches the regular expression
12567 @var{regex}. Otherwise it returns zero.
12568 The syntax of the regular expression is that specified by @code{Python}'s
12569 regular expression support.
12571 @item $_streq(@var{str1}, @var{str2})
12572 @findex $_streq@r{, convenience function}
12573 Returns one if the strings @var{str1} and @var{str2} are equal.
12574 Otherwise it returns zero.
12576 @item $_strlen(@var{str})
12577 @findex $_strlen@r{, convenience function}
12578 Returns the length of string @var{str}.
12580 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12581 @findex $_caller_is@r{, convenience function}
12582 Returns one if the calling function's name is equal to @var{name}.
12583 Otherwise it returns zero.
12585 If the optional argument @var{number_of_frames} is provided,
12586 it is the number of frames up in the stack to look.
12594 at testsuite/gdb.python/py-caller-is.c:21
12595 #1 0x00000000004005a0 in middle_func ()
12596 at testsuite/gdb.python/py-caller-is.c:27
12597 #2 0x00000000004005ab in top_func ()
12598 at testsuite/gdb.python/py-caller-is.c:33
12599 #3 0x00000000004005b6 in main ()
12600 at testsuite/gdb.python/py-caller-is.c:39
12601 (gdb) print $_caller_is ("middle_func")
12603 (gdb) print $_caller_is ("top_func", 2)
12607 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12608 @findex $_caller_matches@r{, convenience function}
12609 Returns one if the calling function's name matches the regular expression
12610 @var{regexp}. Otherwise it returns zero.
12612 If the optional argument @var{number_of_frames} is provided,
12613 it is the number of frames up in the stack to look.
12616 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12617 @findex $_any_caller_is@r{, convenience function}
12618 Returns one if any calling function's name is equal to @var{name}.
12619 Otherwise it returns zero.
12621 If the optional argument @var{number_of_frames} is provided,
12622 it is the number of frames up in the stack to look.
12625 This function differs from @code{$_caller_is} in that this function
12626 checks all stack frames from the immediate caller to the frame specified
12627 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12628 frame specified by @var{number_of_frames}.
12630 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12631 @findex $_any_caller_matches@r{, convenience function}
12632 Returns one if any calling function's name matches the regular expression
12633 @var{regexp}. Otherwise it returns zero.
12635 If the optional argument @var{number_of_frames} is provided,
12636 it is the number of frames up in the stack to look.
12639 This function differs from @code{$_caller_matches} in that this function
12640 checks all stack frames from the immediate caller to the frame specified
12641 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12642 frame specified by @var{number_of_frames}.
12644 @item $_as_string(@var{value})
12645 @findex $_as_string@r{, convenience function}
12646 Return the string representation of @var{value}.
12648 This function is useful to obtain the textual label (enumerator) of an
12649 enumeration value. For example, assuming the variable @var{node} is of
12650 an enumerated type:
12653 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12654 Visiting node of type NODE_INTEGER
12657 @item $_cimag(@var{value})
12658 @itemx $_creal(@var{value})
12659 @findex $_cimag@r{, convenience function}
12660 @findex $_creal@r{, convenience function}
12661 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12662 the complex number @var{value}.
12664 The type of the imaginary or real part depends on the type of the
12665 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12666 will return an imaginary part of type @code{float}.
12670 @value{GDBN} provides the ability to list and get help on
12671 convenience functions.
12674 @item help function
12675 @kindex help function
12676 @cindex show all convenience functions
12677 Print a list of all convenience functions.
12684 You can refer to machine register contents, in expressions, as variables
12685 with names starting with @samp{$}. The names of registers are different
12686 for each machine; use @code{info registers} to see the names used on
12690 @kindex info registers
12691 @item info registers
12692 Print the names and values of all registers except floating-point
12693 and vector registers (in the selected stack frame).
12695 @kindex info all-registers
12696 @cindex floating point registers
12697 @item info all-registers
12698 Print the names and values of all registers, including floating-point
12699 and vector registers (in the selected stack frame).
12701 @anchor{info_registers_reggroup}
12702 @item info registers @var{reggroup} @dots{}
12703 Print the name and value of the registers in each of the specified
12704 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12705 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12707 @item info registers @var{regname} @dots{}
12708 Print the @dfn{relativized} value of each specified register @var{regname}.
12709 As discussed in detail below, register values are normally relative to
12710 the selected stack frame. The @var{regname} may be any register name valid on
12711 the machine you are using, with or without the initial @samp{$}.
12714 @anchor{standard registers}
12715 @cindex stack pointer register
12716 @cindex program counter register
12717 @cindex process status register
12718 @cindex frame pointer register
12719 @cindex standard registers
12720 @value{GDBN} has four ``standard'' register names that are available (in
12721 expressions) on most machines---whenever they do not conflict with an
12722 architecture's canonical mnemonics for registers. The register names
12723 @code{$pc} and @code{$sp} are used for the program counter register and
12724 the stack pointer. @code{$fp} is used for a register that contains a
12725 pointer to the current stack frame, and @code{$ps} is used for a
12726 register that contains the processor status. For example,
12727 you could print the program counter in hex with
12734 or print the instruction to be executed next with
12741 or add four to the stack pointer@footnote{This is a way of removing
12742 one word from the stack, on machines where stacks grow downward in
12743 memory (most machines, nowadays). This assumes that the innermost
12744 stack frame is selected; setting @code{$sp} is not allowed when other
12745 stack frames are selected. To pop entire frames off the stack,
12746 regardless of machine architecture, use @code{return};
12747 see @ref{Returning, ,Returning from a Function}.} with
12753 Whenever possible, these four standard register names are available on
12754 your machine even though the machine has different canonical mnemonics,
12755 so long as there is no conflict. The @code{info registers} command
12756 shows the canonical names. For example, on the SPARC, @code{info
12757 registers} displays the processor status register as @code{$psr} but you
12758 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12759 is an alias for the @sc{eflags} register.
12761 @value{GDBN} always considers the contents of an ordinary register as an
12762 integer when the register is examined in this way. Some machines have
12763 special registers which can hold nothing but floating point; these
12764 registers are considered to have floating point values. There is no way
12765 to refer to the contents of an ordinary register as floating point value
12766 (although you can @emph{print} it as a floating point value with
12767 @samp{print/f $@var{regname}}).
12769 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12770 means that the data format in which the register contents are saved by
12771 the operating system is not the same one that your program normally
12772 sees. For example, the registers of the 68881 floating point
12773 coprocessor are always saved in ``extended'' (raw) format, but all C
12774 programs expect to work with ``double'' (virtual) format. In such
12775 cases, @value{GDBN} normally works with the virtual format only (the format
12776 that makes sense for your program), but the @code{info registers} command
12777 prints the data in both formats.
12779 @cindex SSE registers (x86)
12780 @cindex MMX registers (x86)
12781 Some machines have special registers whose contents can be interpreted
12782 in several different ways. For example, modern x86-based machines
12783 have SSE and MMX registers that can hold several values packed
12784 together in several different formats. @value{GDBN} refers to such
12785 registers in @code{struct} notation:
12788 (@value{GDBP}) print $xmm1
12790 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12791 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12792 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12793 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12794 v4_int32 = @{0, 20657912, 11, 13@},
12795 v2_int64 = @{88725056443645952, 55834574859@},
12796 uint128 = 0x0000000d0000000b013b36f800000000
12801 To set values of such registers, you need to tell @value{GDBN} which
12802 view of the register you wish to change, as if you were assigning
12803 value to a @code{struct} member:
12806 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12809 Normally, register values are relative to the selected stack frame
12810 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12811 value that the register would contain if all stack frames farther in
12812 were exited and their saved registers restored. In order to see the
12813 true contents of hardware registers, you must select the innermost
12814 frame (with @samp{frame 0}).
12816 @cindex caller-saved registers
12817 @cindex call-clobbered registers
12818 @cindex volatile registers
12819 @cindex <not saved> values
12820 Usually ABIs reserve some registers as not needed to be saved by the
12821 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12822 registers). It may therefore not be possible for @value{GDBN} to know
12823 the value a register had before the call (in other words, in the outer
12824 frame), if the register value has since been changed by the callee.
12825 @value{GDBN} tries to deduce where the inner frame saved
12826 (``callee-saved'') registers, from the debug info, unwind info, or the
12827 machine code generated by your compiler. If some register is not
12828 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12829 its own knowledge of the ABI, or because the debug/unwind info
12830 explicitly says the register's value is undefined), @value{GDBN}
12831 displays @w{@samp{<not saved>}} as the register's value. With targets
12832 that @value{GDBN} has no knowledge of the register saving convention,
12833 if a register was not saved by the callee, then its value and location
12834 in the outer frame are assumed to be the same of the inner frame.
12835 This is usually harmless, because if the register is call-clobbered,
12836 the caller either does not care what is in the register after the
12837 call, or has code to restore the value that it does care about. Note,
12838 however, that if you change such a register in the outer frame, you
12839 may also be affecting the inner frame. Also, the more ``outer'' the
12840 frame is you're looking at, the more likely a call-clobbered
12841 register's value is to be wrong, in the sense that it doesn't actually
12842 represent the value the register had just before the call.
12844 @node Floating Point Hardware
12845 @section Floating Point Hardware
12846 @cindex floating point
12848 Depending on the configuration, @value{GDBN} may be able to give
12849 you more information about the status of the floating point hardware.
12854 Display hardware-dependent information about the floating
12855 point unit. The exact contents and layout vary depending on the
12856 floating point chip. Currently, @samp{info float} is supported on
12857 the ARM and x86 machines.
12861 @section Vector Unit
12862 @cindex vector unit
12864 Depending on the configuration, @value{GDBN} may be able to give you
12865 more information about the status of the vector unit.
12868 @kindex info vector
12870 Display information about the vector unit. The exact contents and
12871 layout vary depending on the hardware.
12874 @node OS Information
12875 @section Operating System Auxiliary Information
12876 @cindex OS information
12878 @value{GDBN} provides interfaces to useful OS facilities that can help
12879 you debug your program.
12881 @cindex auxiliary vector
12882 @cindex vector, auxiliary
12883 Some operating systems supply an @dfn{auxiliary vector} to programs at
12884 startup. This is akin to the arguments and environment that you
12885 specify for a program, but contains a system-dependent variety of
12886 binary values that tell system libraries important details about the
12887 hardware, operating system, and process. Each value's purpose is
12888 identified by an integer tag; the meanings are well-known but system-specific.
12889 Depending on the configuration and operating system facilities,
12890 @value{GDBN} may be able to show you this information. For remote
12891 targets, this functionality may further depend on the remote stub's
12892 support of the @samp{qXfer:auxv:read} packet, see
12893 @ref{qXfer auxiliary vector read}.
12898 Display the auxiliary vector of the inferior, which can be either a
12899 live process or a core dump file. @value{GDBN} prints each tag value
12900 numerically, and also shows names and text descriptions for recognized
12901 tags. Some values in the vector are numbers, some bit masks, and some
12902 pointers to strings or other data. @value{GDBN} displays each value in the
12903 most appropriate form for a recognized tag, and in hexadecimal for
12904 an unrecognized tag.
12907 On some targets, @value{GDBN} can access operating system-specific
12908 information and show it to you. The types of information available
12909 will differ depending on the type of operating system running on the
12910 target. The mechanism used to fetch the data is described in
12911 @ref{Operating System Information}. For remote targets, this
12912 functionality depends on the remote stub's support of the
12913 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12917 @item info os @var{infotype}
12919 Display OS information of the requested type.
12921 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12923 @anchor{linux info os infotypes}
12925 @kindex info os cpus
12927 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12928 the available fields from /proc/cpuinfo. For each supported architecture
12929 different fields are available. Two common entries are processor which gives
12930 CPU number and bogomips; a system constant that is calculated during
12931 kernel initialization.
12933 @kindex info os files
12935 Display the list of open file descriptors on the target. For each
12936 file descriptor, @value{GDBN} prints the identifier of the process
12937 owning the descriptor, the command of the owning process, the value
12938 of the descriptor, and the target of the descriptor.
12940 @kindex info os modules
12942 Display the list of all loaded kernel modules on the target. For each
12943 module, @value{GDBN} prints the module name, the size of the module in
12944 bytes, the number of times the module is used, the dependencies of the
12945 module, the status of the module, and the address of the loaded module
12948 @kindex info os msg
12950 Display the list of all System V message queues on the target. For each
12951 message queue, @value{GDBN} prints the message queue key, the message
12952 queue identifier, the access permissions, the current number of bytes
12953 on the queue, the current number of messages on the queue, the processes
12954 that last sent and received a message on the queue, the user and group
12955 of the owner and creator of the message queue, the times at which a
12956 message was last sent and received on the queue, and the time at which
12957 the message queue was last changed.
12959 @kindex info os processes
12961 Display the list of processes on the target. For each process,
12962 @value{GDBN} prints the process identifier, the name of the user, the
12963 command corresponding to the process, and the list of processor cores
12964 that the process is currently running on. (To understand what these
12965 properties mean, for this and the following info types, please consult
12966 the general @sc{gnu}/Linux documentation.)
12968 @kindex info os procgroups
12970 Display the list of process groups on the target. For each process,
12971 @value{GDBN} prints the identifier of the process group that it belongs
12972 to, the command corresponding to the process group leader, the process
12973 identifier, and the command line of the process. The list is sorted
12974 first by the process group identifier, then by the process identifier,
12975 so that processes belonging to the same process group are grouped together
12976 and the process group leader is listed first.
12978 @kindex info os semaphores
12980 Display the list of all System V semaphore sets on the target. For each
12981 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12982 set identifier, the access permissions, the number of semaphores in the
12983 set, the user and group of the owner and creator of the semaphore set,
12984 and the times at which the semaphore set was operated upon and changed.
12986 @kindex info os shm
12988 Display the list of all System V shared-memory regions on the target.
12989 For each shared-memory region, @value{GDBN} prints the region key,
12990 the shared-memory identifier, the access permissions, the size of the
12991 region, the process that created the region, the process that last
12992 attached to or detached from the region, the current number of live
12993 attaches to the region, and the times at which the region was last
12994 attached to, detach from, and changed.
12996 @kindex info os sockets
12998 Display the list of Internet-domain sockets on the target. For each
12999 socket, @value{GDBN} prints the address and port of the local and
13000 remote endpoints, the current state of the connection, the creator of
13001 the socket, the IP address family of the socket, and the type of the
13004 @kindex info os threads
13006 Display the list of threads running on the target. For each thread,
13007 @value{GDBN} prints the identifier of the process that the thread
13008 belongs to, the command of the process, the thread identifier, and the
13009 processor core that it is currently running on. The main thread of a
13010 process is not listed.
13014 If @var{infotype} is omitted, then list the possible values for
13015 @var{infotype} and the kind of OS information available for each
13016 @var{infotype}. If the target does not return a list of possible
13017 types, this command will report an error.
13020 @node Memory Region Attributes
13021 @section Memory Region Attributes
13022 @cindex memory region attributes
13024 @dfn{Memory region attributes} allow you to describe special handling
13025 required by regions of your target's memory. @value{GDBN} uses
13026 attributes to determine whether to allow certain types of memory
13027 accesses; whether to use specific width accesses; and whether to cache
13028 target memory. By default the description of memory regions is
13029 fetched from the target (if the current target supports this), but the
13030 user can override the fetched regions.
13032 Defined memory regions can be individually enabled and disabled. When a
13033 memory region is disabled, @value{GDBN} uses the default attributes when
13034 accessing memory in that region. Similarly, if no memory regions have
13035 been defined, @value{GDBN} uses the default attributes when accessing
13038 When a memory region is defined, it is given a number to identify it;
13039 to enable, disable, or remove a memory region, you specify that number.
13043 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13044 Define a memory region bounded by @var{lower} and @var{upper} with
13045 attributes @var{attributes}@dots{}, and add it to the list of regions
13046 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13047 case: it is treated as the target's maximum memory address.
13048 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13051 Discard any user changes to the memory regions and use target-supplied
13052 regions, if available, or no regions if the target does not support.
13055 @item delete mem @var{nums}@dots{}
13056 Remove memory regions @var{nums}@dots{} from the list of regions
13057 monitored by @value{GDBN}.
13059 @kindex disable mem
13060 @item disable mem @var{nums}@dots{}
13061 Disable monitoring of memory regions @var{nums}@dots{}.
13062 A disabled memory region is not forgotten.
13063 It may be enabled again later.
13066 @item enable mem @var{nums}@dots{}
13067 Enable monitoring of memory regions @var{nums}@dots{}.
13071 Print a table of all defined memory regions, with the following columns
13075 @item Memory Region Number
13076 @item Enabled or Disabled.
13077 Enabled memory regions are marked with @samp{y}.
13078 Disabled memory regions are marked with @samp{n}.
13081 The address defining the inclusive lower bound of the memory region.
13084 The address defining the exclusive upper bound of the memory region.
13087 The list of attributes set for this memory region.
13092 @subsection Attributes
13094 @subsubsection Memory Access Mode
13095 The access mode attributes set whether @value{GDBN} may make read or
13096 write accesses to a memory region.
13098 While these attributes prevent @value{GDBN} from performing invalid
13099 memory accesses, they do nothing to prevent the target system, I/O DMA,
13100 etc.@: from accessing memory.
13104 Memory is read only.
13106 Memory is write only.
13108 Memory is read/write. This is the default.
13111 @subsubsection Memory Access Size
13112 The access size attribute tells @value{GDBN} to use specific sized
13113 accesses in the memory region. Often memory mapped device registers
13114 require specific sized accesses. If no access size attribute is
13115 specified, @value{GDBN} may use accesses of any size.
13119 Use 8 bit memory accesses.
13121 Use 16 bit memory accesses.
13123 Use 32 bit memory accesses.
13125 Use 64 bit memory accesses.
13128 @c @subsubsection Hardware/Software Breakpoints
13129 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13130 @c will use hardware or software breakpoints for the internal breakpoints
13131 @c used by the step, next, finish, until, etc. commands.
13135 @c Always use hardware breakpoints
13136 @c @item swbreak (default)
13139 @subsubsection Data Cache
13140 The data cache attributes set whether @value{GDBN} will cache target
13141 memory. While this generally improves performance by reducing debug
13142 protocol overhead, it can lead to incorrect results because @value{GDBN}
13143 does not know about volatile variables or memory mapped device
13148 Enable @value{GDBN} to cache target memory.
13150 Disable @value{GDBN} from caching target memory. This is the default.
13153 @subsection Memory Access Checking
13154 @value{GDBN} can be instructed to refuse accesses to memory that is
13155 not explicitly described. This can be useful if accessing such
13156 regions has undesired effects for a specific target, or to provide
13157 better error checking. The following commands control this behaviour.
13160 @kindex set mem inaccessible-by-default
13161 @item set mem inaccessible-by-default [on|off]
13162 If @code{on} is specified, make @value{GDBN} treat memory not
13163 explicitly described by the memory ranges as non-existent and refuse accesses
13164 to such memory. The checks are only performed if there's at least one
13165 memory range defined. If @code{off} is specified, make @value{GDBN}
13166 treat the memory not explicitly described by the memory ranges as RAM.
13167 The default value is @code{on}.
13168 @kindex show mem inaccessible-by-default
13169 @item show mem inaccessible-by-default
13170 Show the current handling of accesses to unknown memory.
13174 @c @subsubsection Memory Write Verification
13175 @c The memory write verification attributes set whether @value{GDBN}
13176 @c will re-reads data after each write to verify the write was successful.
13180 @c @item noverify (default)
13183 @node Dump/Restore Files
13184 @section Copy Between Memory and a File
13185 @cindex dump/restore files
13186 @cindex append data to a file
13187 @cindex dump data to a file
13188 @cindex restore data from a file
13190 You can use the commands @code{dump}, @code{append}, and
13191 @code{restore} to copy data between target memory and a file. The
13192 @code{dump} and @code{append} commands write data to a file, and the
13193 @code{restore} command reads data from a file back into the inferior's
13194 memory. Files may be in binary, Motorola S-record, Intel hex,
13195 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13196 append to binary files, and cannot read from Verilog Hex files.
13201 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13202 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13203 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13204 or the value of @var{expr}, to @var{filename} in the given format.
13206 The @var{format} parameter may be any one of:
13213 Motorola S-record format.
13215 Tektronix Hex format.
13217 Verilog Hex format.
13220 @value{GDBN} uses the same definitions of these formats as the
13221 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13222 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13226 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13227 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13228 Append the contents of memory from @var{start_addr} to @var{end_addr},
13229 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13230 (@value{GDBN} can only append data to files in raw binary form.)
13233 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13234 Restore the contents of file @var{filename} into memory. The
13235 @code{restore} command can automatically recognize any known @sc{bfd}
13236 file format, except for raw binary. To restore a raw binary file you
13237 must specify the optional keyword @code{binary} after the filename.
13239 If @var{bias} is non-zero, its value will be added to the addresses
13240 contained in the file. Binary files always start at address zero, so
13241 they will be restored at address @var{bias}. Other bfd files have
13242 a built-in location; they will be restored at offset @var{bias}
13243 from that location.
13245 If @var{start} and/or @var{end} are non-zero, then only data between
13246 file offset @var{start} and file offset @var{end} will be restored.
13247 These offsets are relative to the addresses in the file, before
13248 the @var{bias} argument is applied.
13252 @node Core File Generation
13253 @section How to Produce a Core File from Your Program
13254 @cindex dump core from inferior
13256 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13257 image of a running process and its process status (register values
13258 etc.). Its primary use is post-mortem debugging of a program that
13259 crashed while it ran outside a debugger. A program that crashes
13260 automatically produces a core file, unless this feature is disabled by
13261 the user. @xref{Files}, for information on invoking @value{GDBN} in
13262 the post-mortem debugging mode.
13264 Occasionally, you may wish to produce a core file of the program you
13265 are debugging in order to preserve a snapshot of its state.
13266 @value{GDBN} has a special command for that.
13270 @kindex generate-core-file
13271 @item generate-core-file [@var{file}]
13272 @itemx gcore [@var{file}]
13273 Produce a core dump of the inferior process. The optional argument
13274 @var{file} specifies the file name where to put the core dump. If not
13275 specified, the file name defaults to @file{core.@var{pid}}, where
13276 @var{pid} is the inferior process ID.
13278 Note that this command is implemented only for some systems (as of
13279 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13281 On @sc{gnu}/Linux, this command can take into account the value of the
13282 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13283 dump (@pxref{set use-coredump-filter}), and by default honors the
13284 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13285 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13287 @kindex set use-coredump-filter
13288 @anchor{set use-coredump-filter}
13289 @item set use-coredump-filter on
13290 @itemx set use-coredump-filter off
13291 Enable or disable the use of the file
13292 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13293 files. This file is used by the Linux kernel to decide what types of
13294 memory mappings will be dumped or ignored when generating a core dump
13295 file. @var{pid} is the process ID of a currently running process.
13297 To make use of this feature, you have to write in the
13298 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13299 which is a bit mask representing the memory mapping types. If a bit
13300 is set in the bit mask, then the memory mappings of the corresponding
13301 types will be dumped; otherwise, they will be ignored. This
13302 configuration is inherited by child processes. For more information
13303 about the bits that can be set in the
13304 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13305 manpage of @code{core(5)}.
13307 By default, this option is @code{on}. If this option is turned
13308 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13309 and instead uses the same default value as the Linux kernel in order
13310 to decide which pages will be dumped in the core dump file. This
13311 value is currently @code{0x33}, which means that bits @code{0}
13312 (anonymous private mappings), @code{1} (anonymous shared mappings),
13313 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13314 This will cause these memory mappings to be dumped automatically.
13316 @kindex set dump-excluded-mappings
13317 @anchor{set dump-excluded-mappings}
13318 @item set dump-excluded-mappings on
13319 @itemx set dump-excluded-mappings off
13320 If @code{on} is specified, @value{GDBN} will dump memory mappings
13321 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13322 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13324 The default value is @code{off}.
13327 @node Character Sets
13328 @section Character Sets
13329 @cindex character sets
13331 @cindex translating between character sets
13332 @cindex host character set
13333 @cindex target character set
13335 If the program you are debugging uses a different character set to
13336 represent characters and strings than the one @value{GDBN} uses itself,
13337 @value{GDBN} can automatically translate between the character sets for
13338 you. The character set @value{GDBN} uses we call the @dfn{host
13339 character set}; the one the inferior program uses we call the
13340 @dfn{target character set}.
13342 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13343 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13344 remote protocol (@pxref{Remote Debugging}) to debug a program
13345 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13346 then the host character set is Latin-1, and the target character set is
13347 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13348 target-charset EBCDIC-US}, then @value{GDBN} translates between
13349 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13350 character and string literals in expressions.
13352 @value{GDBN} has no way to automatically recognize which character set
13353 the inferior program uses; you must tell it, using the @code{set
13354 target-charset} command, described below.
13356 Here are the commands for controlling @value{GDBN}'s character set
13360 @item set target-charset @var{charset}
13361 @kindex set target-charset
13362 Set the current target character set to @var{charset}. To display the
13363 list of supported target character sets, type
13364 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13366 @item set host-charset @var{charset}
13367 @kindex set host-charset
13368 Set the current host character set to @var{charset}.
13370 By default, @value{GDBN} uses a host character set appropriate to the
13371 system it is running on; you can override that default using the
13372 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13373 automatically determine the appropriate host character set. In this
13374 case, @value{GDBN} uses @samp{UTF-8}.
13376 @value{GDBN} can only use certain character sets as its host character
13377 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13378 @value{GDBN} will list the host character sets it supports.
13380 @item set charset @var{charset}
13381 @kindex set charset
13382 Set the current host and target character sets to @var{charset}. As
13383 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13384 @value{GDBN} will list the names of the character sets that can be used
13385 for both host and target.
13388 @kindex show charset
13389 Show the names of the current host and target character sets.
13391 @item show host-charset
13392 @kindex show host-charset
13393 Show the name of the current host character set.
13395 @item show target-charset
13396 @kindex show target-charset
13397 Show the name of the current target character set.
13399 @item set target-wide-charset @var{charset}
13400 @kindex set target-wide-charset
13401 Set the current target's wide character set to @var{charset}. This is
13402 the character set used by the target's @code{wchar_t} type. To
13403 display the list of supported wide character sets, type
13404 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13406 @item show target-wide-charset
13407 @kindex show target-wide-charset
13408 Show the name of the current target's wide character set.
13411 Here is an example of @value{GDBN}'s character set support in action.
13412 Assume that the following source code has been placed in the file
13413 @file{charset-test.c}:
13419 = @{72, 101, 108, 108, 111, 44, 32, 119,
13420 111, 114, 108, 100, 33, 10, 0@};
13421 char ibm1047_hello[]
13422 = @{200, 133, 147, 147, 150, 107, 64, 166,
13423 150, 153, 147, 132, 90, 37, 0@};
13427 printf ("Hello, world!\n");
13431 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13432 containing the string @samp{Hello, world!} followed by a newline,
13433 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13435 We compile the program, and invoke the debugger on it:
13438 $ gcc -g charset-test.c -o charset-test
13439 $ gdb -nw charset-test
13440 GNU gdb 2001-12-19-cvs
13441 Copyright 2001 Free Software Foundation, Inc.
13446 We can use the @code{show charset} command to see what character sets
13447 @value{GDBN} is currently using to interpret and display characters and
13451 (@value{GDBP}) show charset
13452 The current host and target character set is `ISO-8859-1'.
13456 For the sake of printing this manual, let's use @sc{ascii} as our
13457 initial character set:
13459 (@value{GDBP}) set charset ASCII
13460 (@value{GDBP}) show charset
13461 The current host and target character set is `ASCII'.
13465 Let's assume that @sc{ascii} is indeed the correct character set for our
13466 host system --- in other words, let's assume that if @value{GDBN} prints
13467 characters using the @sc{ascii} character set, our terminal will display
13468 them properly. Since our current target character set is also
13469 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13472 (@value{GDBP}) print ascii_hello
13473 $1 = 0x401698 "Hello, world!\n"
13474 (@value{GDBP}) print ascii_hello[0]
13479 @value{GDBN} uses the target character set for character and string
13480 literals you use in expressions:
13483 (@value{GDBP}) print '+'
13488 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13491 @value{GDBN} relies on the user to tell it which character set the
13492 target program uses. If we print @code{ibm1047_hello} while our target
13493 character set is still @sc{ascii}, we get jibberish:
13496 (@value{GDBP}) print ibm1047_hello
13497 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13498 (@value{GDBP}) print ibm1047_hello[0]
13503 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13504 @value{GDBN} tells us the character sets it supports:
13507 (@value{GDBP}) set target-charset
13508 ASCII EBCDIC-US IBM1047 ISO-8859-1
13509 (@value{GDBP}) set target-charset
13512 We can select @sc{ibm1047} as our target character set, and examine the
13513 program's strings again. Now the @sc{ascii} string is wrong, but
13514 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13515 target character set, @sc{ibm1047}, to the host character set,
13516 @sc{ascii}, and they display correctly:
13519 (@value{GDBP}) set target-charset IBM1047
13520 (@value{GDBP}) show charset
13521 The current host character set is `ASCII'.
13522 The current target character set is `IBM1047'.
13523 (@value{GDBP}) print ascii_hello
13524 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13525 (@value{GDBP}) print ascii_hello[0]
13527 (@value{GDBP}) print ibm1047_hello
13528 $8 = 0x4016a8 "Hello, world!\n"
13529 (@value{GDBP}) print ibm1047_hello[0]
13534 As above, @value{GDBN} uses the target character set for character and
13535 string literals you use in expressions:
13538 (@value{GDBP}) print '+'
13543 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13546 @node Caching Target Data
13547 @section Caching Data of Targets
13548 @cindex caching data of targets
13550 @value{GDBN} caches data exchanged between the debugger and a target.
13551 Each cache is associated with the address space of the inferior.
13552 @xref{Inferiors Connections and Programs}, about inferior and address space.
13553 Such caching generally improves performance in remote debugging
13554 (@pxref{Remote Debugging}), because it reduces the overhead of the
13555 remote protocol by bundling memory reads and writes into large chunks.
13556 Unfortunately, simply caching everything would lead to incorrect results,
13557 since @value{GDBN} does not necessarily know anything about volatile
13558 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13559 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13561 Therefore, by default, @value{GDBN} only caches data
13562 known to be on the stack@footnote{In non-stop mode, it is moderately
13563 rare for a running thread to modify the stack of a stopped thread
13564 in a way that would interfere with a backtrace, and caching of
13565 stack reads provides a significant speed up of remote backtraces.} or
13566 in the code segment.
13567 Other regions of memory can be explicitly marked as
13568 cacheable; @pxref{Memory Region Attributes}.
13571 @kindex set remotecache
13572 @item set remotecache on
13573 @itemx set remotecache off
13574 This option no longer does anything; it exists for compatibility
13577 @kindex show remotecache
13578 @item show remotecache
13579 Show the current state of the obsolete remotecache flag.
13581 @kindex set stack-cache
13582 @item set stack-cache on
13583 @itemx set stack-cache off
13584 Enable or disable caching of stack accesses. When @code{on}, use
13585 caching. By default, this option is @code{on}.
13587 @kindex show stack-cache
13588 @item show stack-cache
13589 Show the current state of data caching for memory accesses.
13591 @kindex set code-cache
13592 @item set code-cache on
13593 @itemx set code-cache off
13594 Enable or disable caching of code segment accesses. When @code{on},
13595 use caching. By default, this option is @code{on}. This improves
13596 performance of disassembly in remote debugging.
13598 @kindex show code-cache
13599 @item show code-cache
13600 Show the current state of target memory cache for code segment
13603 @kindex info dcache
13604 @item info dcache @r{[}line@r{]}
13605 Print the information about the performance of data cache of the
13606 current inferior's address space. The information displayed
13607 includes the dcache width and depth, and for each cache line, its
13608 number, address, and how many times it was referenced. This
13609 command is useful for debugging the data cache operation.
13611 If a line number is specified, the contents of that line will be
13614 @item set dcache size @var{size}
13615 @cindex dcache size
13616 @kindex set dcache size
13617 Set maximum number of entries in dcache (dcache depth above).
13619 @item set dcache line-size @var{line-size}
13620 @cindex dcache line-size
13621 @kindex set dcache line-size
13622 Set number of bytes each dcache entry caches (dcache width above).
13623 Must be a power of 2.
13625 @item show dcache size
13626 @kindex show dcache size
13627 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13629 @item show dcache line-size
13630 @kindex show dcache line-size
13631 Show default size of dcache lines.
13633 @item maint flush dcache
13634 @cindex dcache, flushing
13635 @kindex maint flush dcache
13636 Flush the contents (if any) of the dcache. This maintainer command is
13637 useful when debugging the dcache implementation.
13641 @node Searching Memory
13642 @section Search Memory
13643 @cindex searching memory
13645 Memory can be searched for a particular sequence of bytes with the
13646 @code{find} command.
13650 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13651 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13652 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13653 etc. The search begins at address @var{start_addr} and continues for either
13654 @var{len} bytes or through to @var{end_addr} inclusive.
13657 @var{s} and @var{n} are optional parameters.
13658 They may be specified in either order, apart or together.
13661 @item @var{s}, search query size
13662 The size of each search query value.
13668 halfwords (two bytes)
13672 giant words (eight bytes)
13675 All values are interpreted in the current language.
13676 This means, for example, that if the current source language is C/C@t{++}
13677 then searching for the string ``hello'' includes the trailing '\0'.
13678 The null terminator can be removed from searching by using casts,
13679 e.g.: @samp{@{char[5]@}"hello"}.
13681 If the value size is not specified, it is taken from the
13682 value's type in the current language.
13683 This is useful when one wants to specify the search
13684 pattern as a mixture of types.
13685 Note that this means, for example, that in the case of C-like languages
13686 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13687 which is typically four bytes.
13689 @item @var{n}, maximum number of finds
13690 The maximum number of matches to print. The default is to print all finds.
13693 You can use strings as search values. Quote them with double-quotes
13695 The string value is copied into the search pattern byte by byte,
13696 regardless of the endianness of the target and the size specification.
13698 The address of each match found is printed as well as a count of the
13699 number of matches found.
13701 The address of the last value found is stored in convenience variable
13703 A count of the number of matches is stored in @samp{$numfound}.
13705 For example, if stopped at the @code{printf} in this function:
13711 static char hello[] = "hello-hello";
13712 static struct @{ char c; short s; int i; @}
13713 __attribute__ ((packed)) mixed
13714 = @{ 'c', 0x1234, 0x87654321 @};
13715 printf ("%s\n", hello);
13720 you get during debugging:
13723 (gdb) find &hello[0], +sizeof(hello), "hello"
13724 0x804956d <hello.1620+6>
13726 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13727 0x8049567 <hello.1620>
13728 0x804956d <hello.1620+6>
13730 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13731 0x8049567 <hello.1620>
13732 0x804956d <hello.1620+6>
13734 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13735 0x8049567 <hello.1620>
13737 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13738 0x8049560 <mixed.1625>
13740 (gdb) print $numfound
13743 $2 = (void *) 0x8049560
13747 @section Value Sizes
13749 Whenever @value{GDBN} prints a value memory will be allocated within
13750 @value{GDBN} to hold the contents of the value. It is possible in
13751 some languages with dynamic typing systems, that an invalid program
13752 may indicate a value that is incorrectly large, this in turn may cause
13753 @value{GDBN} to try and allocate an overly large amount of memory.
13756 @kindex set max-value-size
13757 @item set max-value-size @var{bytes}
13758 @itemx set max-value-size unlimited
13759 Set the maximum size of memory that @value{GDBN} will allocate for the
13760 contents of a value to @var{bytes}, trying to display a value that
13761 requires more memory than that will result in an error.
13763 Setting this variable does not effect values that have already been
13764 allocated within @value{GDBN}, only future allocations.
13766 There's a minimum size that @code{max-value-size} can be set to in
13767 order that @value{GDBN} can still operate correctly, this minimum is
13768 currently 16 bytes.
13770 The limit applies to the results of some subexpressions as well as to
13771 complete expressions. For example, an expression denoting a simple
13772 integer component, such as @code{x.y.z}, may fail if the size of
13773 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13774 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13775 @var{A} is an array variable with non-constant size, will generally
13776 succeed regardless of the bounds on @var{A}, as long as the component
13777 size is less than @var{bytes}.
13779 The default value of @code{max-value-size} is currently 64k.
13781 @kindex show max-value-size
13782 @item show max-value-size
13783 Show the maximum size of memory, in bytes, that @value{GDBN} will
13784 allocate for the contents of a value.
13787 @node Optimized Code
13788 @chapter Debugging Optimized Code
13789 @cindex optimized code, debugging
13790 @cindex debugging optimized code
13792 Almost all compilers support optimization. With optimization
13793 disabled, the compiler generates assembly code that corresponds
13794 directly to your source code, in a simplistic way. As the compiler
13795 applies more powerful optimizations, the generated assembly code
13796 diverges from your original source code. With help from debugging
13797 information generated by the compiler, @value{GDBN} can map from
13798 the running program back to constructs from your original source.
13800 @value{GDBN} is more accurate with optimization disabled. If you
13801 can recompile without optimization, it is easier to follow the
13802 progress of your program during debugging. But, there are many cases
13803 where you may need to debug an optimized version.
13805 When you debug a program compiled with @samp{-g -O}, remember that the
13806 optimizer has rearranged your code; the debugger shows you what is
13807 really there. Do not be too surprised when the execution path does not
13808 exactly match your source file! An extreme example: if you define a
13809 variable, but never use it, @value{GDBN} never sees that
13810 variable---because the compiler optimizes it out of existence.
13812 Some things do not work as well with @samp{-g -O} as with just
13813 @samp{-g}, particularly on machines with instruction scheduling. If in
13814 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13815 please report it to us as a bug (including a test case!).
13816 @xref{Variables}, for more information about debugging optimized code.
13819 * Inline Functions:: How @value{GDBN} presents inlining
13820 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13823 @node Inline Functions
13824 @section Inline Functions
13825 @cindex inline functions, debugging
13827 @dfn{Inlining} is an optimization that inserts a copy of the function
13828 body directly at each call site, instead of jumping to a shared
13829 routine. @value{GDBN} displays inlined functions just like
13830 non-inlined functions. They appear in backtraces. You can view their
13831 arguments and local variables, step into them with @code{step}, skip
13832 them with @code{next}, and escape from them with @code{finish}.
13833 You can check whether a function was inlined by using the
13834 @code{info frame} command.
13836 For @value{GDBN} to support inlined functions, the compiler must
13837 record information about inlining in the debug information ---
13838 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13839 other compilers do also. @value{GDBN} only supports inlined functions
13840 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13841 do not emit two required attributes (@samp{DW_AT_call_file} and
13842 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13843 function calls with earlier versions of @value{NGCC}. It instead
13844 displays the arguments and local variables of inlined functions as
13845 local variables in the caller.
13847 The body of an inlined function is directly included at its call site;
13848 unlike a non-inlined function, there are no instructions devoted to
13849 the call. @value{GDBN} still pretends that the call site and the
13850 start of the inlined function are different instructions. Stepping to
13851 the call site shows the call site, and then stepping again shows
13852 the first line of the inlined function, even though no additional
13853 instructions are executed.
13855 This makes source-level debugging much clearer; you can see both the
13856 context of the call and then the effect of the call. Only stepping by
13857 a single instruction using @code{stepi} or @code{nexti} does not do
13858 this; single instruction steps always show the inlined body.
13860 There are some ways that @value{GDBN} does not pretend that inlined
13861 function calls are the same as normal calls:
13865 Setting breakpoints at the call site of an inlined function may not
13866 work, because the call site does not contain any code. @value{GDBN}
13867 may incorrectly move the breakpoint to the next line of the enclosing
13868 function, after the call. This limitation will be removed in a future
13869 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13870 or inside the inlined function instead.
13873 @value{GDBN} cannot locate the return value of inlined calls after
13874 using the @code{finish} command. This is a limitation of compiler-generated
13875 debugging information; after @code{finish}, you can step to the next line
13876 and print a variable where your program stored the return value.
13880 @node Tail Call Frames
13881 @section Tail Call Frames
13882 @cindex tail call frames, debugging
13884 Function @code{B} can call function @code{C} in its very last statement. In
13885 unoptimized compilation the call of @code{C} is immediately followed by return
13886 instruction at the end of @code{B} code. Optimizing compiler may replace the
13887 call and return in function @code{B} into one jump to function @code{C}
13888 instead. Such use of a jump instruction is called @dfn{tail call}.
13890 During execution of function @code{C}, there will be no indication in the
13891 function call stack frames that it was tail-called from @code{B}. If function
13892 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13893 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13894 some cases @value{GDBN} can determine that @code{C} was tail-called from
13895 @code{B}, and it will then create fictitious call frame for that, with the
13896 return address set up as if @code{B} called @code{C} normally.
13898 This functionality is currently supported only by DWARF 2 debugging format and
13899 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13900 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13903 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13904 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13908 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13910 Stack level 1, frame at 0x7fffffffda30:
13911 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13912 tail call frame, caller of frame at 0x7fffffffda30
13913 source language c++.
13914 Arglist at unknown address.
13915 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13918 The detection of all the possible code path executions can find them ambiguous.
13919 There is no execution history stored (possible @ref{Reverse Execution} is never
13920 used for this purpose) and the last known caller could have reached the known
13921 callee by multiple different jump sequences. In such case @value{GDBN} still
13922 tries to show at least all the unambiguous top tail callers and all the
13923 unambiguous bottom tail calees, if any.
13926 @anchor{set debug entry-values}
13927 @item set debug entry-values
13928 @kindex set debug entry-values
13929 When set to on, enables printing of analysis messages for both frame argument
13930 values at function entry and tail calls. It will show all the possible valid
13931 tail calls code paths it has considered. It will also print the intersection
13932 of them with the final unambiguous (possibly partial or even empty) code path
13935 @item show debug entry-values
13936 @kindex show debug entry-values
13937 Show the current state of analysis messages printing for both frame argument
13938 values at function entry and tail calls.
13941 The analysis messages for tail calls can for example show why the virtual tail
13942 call frame for function @code{c} has not been recognized (due to the indirect
13943 reference by variable @code{x}):
13946 static void __attribute__((noinline, noclone)) c (void);
13947 void (*x) (void) = c;
13948 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13949 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13950 int main (void) @{ x (); return 0; @}
13952 Breakpoint 1, DW_OP_entry_value resolving cannot find
13953 DW_TAG_call_site 0x40039a in main
13955 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13958 #1 0x000000000040039a in main () at t.c:5
13961 Another possibility is an ambiguous virtual tail call frames resolution:
13965 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13966 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13967 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13968 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13969 static void __attribute__((noinline, noclone)) b (void)
13970 @{ if (i) c (); else e (); @}
13971 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13972 int main (void) @{ a (); return 0; @}
13974 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13975 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13976 tailcall: reduced: 0x4004d2(a) |
13979 #1 0x00000000004004d2 in a () at t.c:8
13980 #2 0x0000000000400395 in main () at t.c:9
13983 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13984 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13986 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13987 @ifset HAVE_MAKEINFO_CLICK
13988 @set ARROW @click{}
13989 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13990 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13992 @ifclear HAVE_MAKEINFO_CLICK
13994 @set CALLSEQ1B @value{CALLSEQ1A}
13995 @set CALLSEQ2B @value{CALLSEQ2A}
13998 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13999 The code can have possible execution paths @value{CALLSEQ1B} or
14000 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14002 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14003 has found. It then finds another possible calling sequence - that one is
14004 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14005 printed as the @code{reduced:} calling sequence. That one could have many
14006 further @code{compare:} and @code{reduced:} statements as long as there remain
14007 any non-ambiguous sequence entries.
14009 For the frame of function @code{b} in both cases there are different possible
14010 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14011 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14012 therefore this one is displayed to the user while the ambiguous frames are
14015 There can be also reasons why printing of frame argument values at function
14020 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14021 static void __attribute__((noinline, noclone)) a (int i);
14022 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14023 static void __attribute__((noinline, noclone)) a (int i)
14024 @{ if (i) b (i - 1); else c (0); @}
14025 int main (void) @{ a (5); return 0; @}
14028 #0 c (i=i@@entry=0) at t.c:2
14029 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14030 function "a" at 0x400420 can call itself via tail calls
14031 i=<optimized out>) at t.c:6
14032 #2 0x000000000040036e in main () at t.c:7
14035 @value{GDBN} cannot find out from the inferior state if and how many times did
14036 function @code{a} call itself (via function @code{b}) as these calls would be
14037 tail calls. Such tail calls would modify the @code{i} variable, therefore
14038 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14039 prints @code{<optimized out>} instead.
14042 @chapter C Preprocessor Macros
14044 Some languages, such as C and C@t{++}, provide a way to define and invoke
14045 ``preprocessor macros'' which expand into strings of tokens.
14046 @value{GDBN} can evaluate expressions containing macro invocations, show
14047 the result of macro expansion, and show a macro's definition, including
14048 where it was defined.
14050 You may need to compile your program specially to provide @value{GDBN}
14051 with information about preprocessor macros. Most compilers do not
14052 include macros in their debugging information, even when you compile
14053 with the @option{-g} flag. @xref{Compilation}.
14055 A program may define a macro at one point, remove that definition later,
14056 and then provide a different definition after that. Thus, at different
14057 points in the program, a macro may have different definitions, or have
14058 no definition at all. If there is a current stack frame, @value{GDBN}
14059 uses the macros in scope at that frame's source code line. Otherwise,
14060 @value{GDBN} uses the macros in scope at the current listing location;
14063 Whenever @value{GDBN} evaluates an expression, it always expands any
14064 macro invocations present in the expression. @value{GDBN} also provides
14065 the following commands for working with macros explicitly.
14069 @kindex macro expand
14070 @cindex macro expansion, showing the results of preprocessor
14071 @cindex preprocessor macro expansion, showing the results of
14072 @cindex expanding preprocessor macros
14073 @item macro expand @var{expression}
14074 @itemx macro exp @var{expression}
14075 Show the results of expanding all preprocessor macro invocations in
14076 @var{expression}. Since @value{GDBN} simply expands macros, but does
14077 not parse the result, @var{expression} need not be a valid expression;
14078 it can be any string of tokens.
14081 @item macro expand-once @var{expression}
14082 @itemx macro exp1 @var{expression}
14083 @cindex expand macro once
14084 @i{(This command is not yet implemented.)} Show the results of
14085 expanding those preprocessor macro invocations that appear explicitly in
14086 @var{expression}. Macro invocations appearing in that expansion are
14087 left unchanged. This command allows you to see the effect of a
14088 particular macro more clearly, without being confused by further
14089 expansions. Since @value{GDBN} simply expands macros, but does not
14090 parse the result, @var{expression} need not be a valid expression; it
14091 can be any string of tokens.
14094 @cindex macro definition, showing
14095 @cindex definition of a macro, showing
14096 @cindex macros, from debug info
14097 @item info macro [-a|-all] [--] @var{macro}
14098 Show the current definition or all definitions of the named @var{macro},
14099 and describe the source location or compiler command-line where that
14100 definition was established. The optional double dash is to signify the end of
14101 argument processing and the beginning of @var{macro} for non C-like macros where
14102 the macro may begin with a hyphen.
14104 @kindex info macros
14105 @item info macros @var{location}
14106 Show all macro definitions that are in effect at the location specified
14107 by @var{location}, and describe the source location or compiler
14108 command-line where those definitions were established.
14110 @kindex macro define
14111 @cindex user-defined macros
14112 @cindex defining macros interactively
14113 @cindex macros, user-defined
14114 @item macro define @var{macro} @var{replacement-list}
14115 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14116 Introduce a definition for a preprocessor macro named @var{macro},
14117 invocations of which are replaced by the tokens given in
14118 @var{replacement-list}. The first form of this command defines an
14119 ``object-like'' macro, which takes no arguments; the second form
14120 defines a ``function-like'' macro, which takes the arguments given in
14123 A definition introduced by this command is in scope in every
14124 expression evaluated in @value{GDBN}, until it is removed with the
14125 @code{macro undef} command, described below. The definition overrides
14126 all definitions for @var{macro} present in the program being debugged,
14127 as well as any previous user-supplied definition.
14129 @kindex macro undef
14130 @item macro undef @var{macro}
14131 Remove any user-supplied definition for the macro named @var{macro}.
14132 This command only affects definitions provided with the @code{macro
14133 define} command, described above; it cannot remove definitions present
14134 in the program being debugged.
14138 List all the macros defined using the @code{macro define} command.
14141 @cindex macros, example of debugging with
14142 Here is a transcript showing the above commands in action. First, we
14143 show our source files:
14148 #include "sample.h"
14151 #define ADD(x) (M + x)
14156 printf ("Hello, world!\n");
14158 printf ("We're so creative.\n");
14160 printf ("Goodbye, world!\n");
14167 Now, we compile the program using the @sc{gnu} C compiler,
14168 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14169 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14170 and @option{-gdwarf-4}; we recommend always choosing the most recent
14171 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14172 includes information about preprocessor macros in the debugging
14176 $ gcc -gdwarf-2 -g3 sample.c -o sample
14180 Now, we start @value{GDBN} on our sample program:
14184 GNU gdb 2002-05-06-cvs
14185 Copyright 2002 Free Software Foundation, Inc.
14186 GDB is free software, @dots{}
14190 We can expand macros and examine their definitions, even when the
14191 program is not running. @value{GDBN} uses the current listing position
14192 to decide which macro definitions are in scope:
14195 (@value{GDBP}) list main
14198 5 #define ADD(x) (M + x)
14203 10 printf ("Hello, world!\n");
14205 12 printf ("We're so creative.\n");
14206 (@value{GDBP}) info macro ADD
14207 Defined at /home/jimb/gdb/macros/play/sample.c:5
14208 #define ADD(x) (M + x)
14209 (@value{GDBP}) info macro Q
14210 Defined at /home/jimb/gdb/macros/play/sample.h:1
14211 included at /home/jimb/gdb/macros/play/sample.c:2
14213 (@value{GDBP}) macro expand ADD(1)
14214 expands to: (42 + 1)
14215 (@value{GDBP}) macro expand-once ADD(1)
14216 expands to: once (M + 1)
14220 In the example above, note that @code{macro expand-once} expands only
14221 the macro invocation explicit in the original text --- the invocation of
14222 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14223 which was introduced by @code{ADD}.
14225 Once the program is running, @value{GDBN} uses the macro definitions in
14226 force at the source line of the current stack frame:
14229 (@value{GDBP}) break main
14230 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14232 Starting program: /home/jimb/gdb/macros/play/sample
14234 Breakpoint 1, main () at sample.c:10
14235 10 printf ("Hello, world!\n");
14239 At line 10, the definition of the macro @code{N} at line 9 is in force:
14242 (@value{GDBP}) info macro N
14243 Defined at /home/jimb/gdb/macros/play/sample.c:9
14245 (@value{GDBP}) macro expand N Q M
14246 expands to: 28 < 42
14247 (@value{GDBP}) print N Q M
14252 As we step over directives that remove @code{N}'s definition, and then
14253 give it a new definition, @value{GDBN} finds the definition (or lack
14254 thereof) in force at each point:
14257 (@value{GDBP}) next
14259 12 printf ("We're so creative.\n");
14260 (@value{GDBP}) info macro N
14261 The symbol `N' has no definition as a C/C++ preprocessor macro
14262 at /home/jimb/gdb/macros/play/sample.c:12
14263 (@value{GDBP}) next
14265 14 printf ("Goodbye, world!\n");
14266 (@value{GDBP}) info macro N
14267 Defined at /home/jimb/gdb/macros/play/sample.c:13
14269 (@value{GDBP}) macro expand N Q M
14270 expands to: 1729 < 42
14271 (@value{GDBP}) print N Q M
14276 In addition to source files, macros can be defined on the compilation command
14277 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14278 such a way, @value{GDBN} displays the location of their definition as line zero
14279 of the source file submitted to the compiler.
14282 (@value{GDBP}) info macro __STDC__
14283 Defined at /home/jimb/gdb/macros/play/sample.c:0
14290 @chapter Tracepoints
14291 @c This chapter is based on the documentation written by Michael
14292 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14294 @cindex tracepoints
14295 In some applications, it is not feasible for the debugger to interrupt
14296 the program's execution long enough for the developer to learn
14297 anything helpful about its behavior. If the program's correctness
14298 depends on its real-time behavior, delays introduced by a debugger
14299 might cause the program to change its behavior drastically, or perhaps
14300 fail, even when the code itself is correct. It is useful to be able
14301 to observe the program's behavior without interrupting it.
14303 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14304 specify locations in the program, called @dfn{tracepoints}, and
14305 arbitrary expressions to evaluate when those tracepoints are reached.
14306 Later, using the @code{tfind} command, you can examine the values
14307 those expressions had when the program hit the tracepoints. The
14308 expressions may also denote objects in memory---structures or arrays,
14309 for example---whose values @value{GDBN} should record; while visiting
14310 a particular tracepoint, you may inspect those objects as if they were
14311 in memory at that moment. However, because @value{GDBN} records these
14312 values without interacting with you, it can do so quickly and
14313 unobtrusively, hopefully not disturbing the program's behavior.
14315 The tracepoint facility is currently available only for remote
14316 targets. @xref{Targets}. In addition, your remote target must know
14317 how to collect trace data. This functionality is implemented in the
14318 remote stub; however, none of the stubs distributed with @value{GDBN}
14319 support tracepoints as of this writing. The format of the remote
14320 packets used to implement tracepoints are described in @ref{Tracepoint
14323 It is also possible to get trace data from a file, in a manner reminiscent
14324 of corefiles; you specify the filename, and use @code{tfind} to search
14325 through the file. @xref{Trace Files}, for more details.
14327 This chapter describes the tracepoint commands and features.
14330 * Set Tracepoints::
14331 * Analyze Collected Data::
14332 * Tracepoint Variables::
14336 @node Set Tracepoints
14337 @section Commands to Set Tracepoints
14339 Before running such a @dfn{trace experiment}, an arbitrary number of
14340 tracepoints can be set. A tracepoint is actually a special type of
14341 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14342 standard breakpoint commands. For instance, as with breakpoints,
14343 tracepoint numbers are successive integers starting from one, and many
14344 of the commands associated with tracepoints take the tracepoint number
14345 as their argument, to identify which tracepoint to work on.
14347 For each tracepoint, you can specify, in advance, some arbitrary set
14348 of data that you want the target to collect in the trace buffer when
14349 it hits that tracepoint. The collected data can include registers,
14350 local variables, or global data. Later, you can use @value{GDBN}
14351 commands to examine the values these data had at the time the
14352 tracepoint was hit.
14354 Tracepoints do not support every breakpoint feature. Ignore counts on
14355 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14356 commands when they are hit. Tracepoints may not be thread-specific
14359 @cindex fast tracepoints
14360 Some targets may support @dfn{fast tracepoints}, which are inserted in
14361 a different way (such as with a jump instead of a trap), that is
14362 faster but possibly restricted in where they may be installed.
14364 @cindex static tracepoints
14365 @cindex markers, static tracepoints
14366 @cindex probing markers, static tracepoints
14367 Regular and fast tracepoints are dynamic tracing facilities, meaning
14368 that they can be used to insert tracepoints at (almost) any location
14369 in the target. Some targets may also support controlling @dfn{static
14370 tracepoints} from @value{GDBN}. With static tracing, a set of
14371 instrumentation points, also known as @dfn{markers}, are embedded in
14372 the target program, and can be activated or deactivated by name or
14373 address. These are usually placed at locations which facilitate
14374 investigating what the target is actually doing. @value{GDBN}'s
14375 support for static tracing includes being able to list instrumentation
14376 points, and attach them with @value{GDBN} defined high level
14377 tracepoints that expose the whole range of convenience of
14378 @value{GDBN}'s tracepoints support. Namely, support for collecting
14379 registers values and values of global or local (to the instrumentation
14380 point) variables; tracepoint conditions and trace state variables.
14381 The act of installing a @value{GDBN} static tracepoint on an
14382 instrumentation point, or marker, is referred to as @dfn{probing} a
14383 static tracepoint marker.
14385 @code{gdbserver} supports tracepoints on some target systems.
14386 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14388 This section describes commands to set tracepoints and associated
14389 conditions and actions.
14392 * Create and Delete Tracepoints::
14393 * Enable and Disable Tracepoints::
14394 * Tracepoint Passcounts::
14395 * Tracepoint Conditions::
14396 * Trace State Variables::
14397 * Tracepoint Actions::
14398 * Listing Tracepoints::
14399 * Listing Static Tracepoint Markers::
14400 * Starting and Stopping Trace Experiments::
14401 * Tracepoint Restrictions::
14404 @node Create and Delete Tracepoints
14405 @subsection Create and Delete Tracepoints
14408 @cindex set tracepoint
14410 @item trace @var{location}
14411 The @code{trace} command is very similar to the @code{break} command.
14412 Its argument @var{location} can be any valid location.
14413 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14414 which is a point in the target program where the debugger will briefly stop,
14415 collect some data, and then allow the program to continue. Setting a tracepoint
14416 or changing its actions takes effect immediately if the remote stub
14417 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14419 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14420 these changes don't take effect until the next @code{tstart}
14421 command, and once a trace experiment is running, further changes will
14422 not have any effect until the next trace experiment starts. In addition,
14423 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14424 address is not yet resolved. (This is similar to pending breakpoints.)
14425 Pending tracepoints are not downloaded to the target and not installed
14426 until they are resolved. The resolution of pending tracepoints requires
14427 @value{GDBN} support---when debugging with the remote target, and
14428 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14429 tracing}), pending tracepoints can not be resolved (and downloaded to
14430 the remote stub) while @value{GDBN} is disconnected.
14432 Here are some examples of using the @code{trace} command:
14435 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14437 (@value{GDBP}) @b{trace +2} // 2 lines forward
14439 (@value{GDBP}) @b{trace my_function} // first source line of function
14441 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14443 (@value{GDBP}) @b{trace *0x2117c4} // an address
14447 You can abbreviate @code{trace} as @code{tr}.
14449 @item trace @var{location} if @var{cond}
14450 Set a tracepoint with condition @var{cond}; evaluate the expression
14451 @var{cond} each time the tracepoint is reached, and collect data only
14452 if the value is nonzero---that is, if @var{cond} evaluates as true.
14453 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14454 information on tracepoint conditions.
14456 @item ftrace @var{location} [ if @var{cond} ]
14457 @cindex set fast tracepoint
14458 @cindex fast tracepoints, setting
14460 The @code{ftrace} command sets a fast tracepoint. For targets that
14461 support them, fast tracepoints will use a more efficient but possibly
14462 less general technique to trigger data collection, such as a jump
14463 instruction instead of a trap, or some sort of hardware support. It
14464 may not be possible to create a fast tracepoint at the desired
14465 location, in which case the command will exit with an explanatory
14468 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14471 On 32-bit x86-architecture systems, fast tracepoints normally need to
14472 be placed at an instruction that is 5 bytes or longer, but can be
14473 placed at 4-byte instructions if the low 64K of memory of the target
14474 program is available to install trampolines. Some Unix-type systems,
14475 such as @sc{gnu}/Linux, exclude low addresses from the program's
14476 address space; but for instance with the Linux kernel it is possible
14477 to let @value{GDBN} use this area by doing a @command{sysctl} command
14478 to set the @code{mmap_min_addr} kernel parameter, as in
14481 sudo sysctl -w vm.mmap_min_addr=32768
14485 which sets the low address to 32K, which leaves plenty of room for
14486 trampolines. The minimum address should be set to a page boundary.
14488 @item strace @var{location} [ if @var{cond} ]
14489 @cindex set static tracepoint
14490 @cindex static tracepoints, setting
14491 @cindex probe static tracepoint marker
14493 The @code{strace} command sets a static tracepoint. For targets that
14494 support it, setting a static tracepoint probes a static
14495 instrumentation point, or marker, found at @var{location}. It may not
14496 be possible to set a static tracepoint at the desired location, in
14497 which case the command will exit with an explanatory message.
14499 @value{GDBN} handles arguments to @code{strace} exactly as for
14500 @code{trace}, with the addition that the user can also specify
14501 @code{-m @var{marker}} as @var{location}. This probes the marker
14502 identified by the @var{marker} string identifier. This identifier
14503 depends on the static tracepoint backend library your program is
14504 using. You can find all the marker identifiers in the @samp{ID} field
14505 of the @code{info static-tracepoint-markers} command output.
14506 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14507 Markers}. For example, in the following small program using the UST
14513 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14518 the marker id is composed of joining the first two arguments to the
14519 @code{trace_mark} call with a slash, which translates to:
14522 (@value{GDBP}) info static-tracepoint-markers
14523 Cnt Enb ID Address What
14524 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14530 so you may probe the marker above with:
14533 (@value{GDBP}) strace -m ust/bar33
14536 Static tracepoints accept an extra collect action --- @code{collect
14537 $_sdata}. This collects arbitrary user data passed in the probe point
14538 call to the tracing library. In the UST example above, you'll see
14539 that the third argument to @code{trace_mark} is a printf-like format
14540 string. The user data is then the result of running that formatting
14541 string against the following arguments. Note that @code{info
14542 static-tracepoint-markers} command output lists that format string in
14543 the @samp{Data:} field.
14545 You can inspect this data when analyzing the trace buffer, by printing
14546 the $_sdata variable like any other variable available to
14547 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14550 @cindex last tracepoint number
14551 @cindex recent tracepoint number
14552 @cindex tracepoint number
14553 The convenience variable @code{$tpnum} records the tracepoint number
14554 of the most recently set tracepoint.
14556 @kindex delete tracepoint
14557 @cindex tracepoint deletion
14558 @item delete tracepoint @r{[}@var{num}@r{]}
14559 Permanently delete one or more tracepoints. With no argument, the
14560 default is to delete all tracepoints. Note that the regular
14561 @code{delete} command can remove tracepoints also.
14566 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14568 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14572 You can abbreviate this command as @code{del tr}.
14575 @node Enable and Disable Tracepoints
14576 @subsection Enable and Disable Tracepoints
14578 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14581 @kindex disable tracepoint
14582 @item disable tracepoint @r{[}@var{num}@r{]}
14583 Disable tracepoint @var{num}, or all tracepoints if no argument
14584 @var{num} is given. A disabled tracepoint will have no effect during
14585 a trace experiment, but it is not forgotten. You can re-enable
14586 a disabled tracepoint using the @code{enable tracepoint} command.
14587 If the command is issued during a trace experiment and the debug target
14588 has support for disabling tracepoints during a trace experiment, then the
14589 change will be effective immediately. Otherwise, it will be applied to the
14590 next trace experiment.
14592 @kindex enable tracepoint
14593 @item enable tracepoint @r{[}@var{num}@r{]}
14594 Enable tracepoint @var{num}, or all tracepoints. If this command is
14595 issued during a trace experiment and the debug target supports enabling
14596 tracepoints during a trace experiment, then the enabled tracepoints will
14597 become effective immediately. Otherwise, they will become effective the
14598 next time a trace experiment is run.
14601 @node Tracepoint Passcounts
14602 @subsection Tracepoint Passcounts
14606 @cindex tracepoint pass count
14607 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14608 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14609 automatically stop a trace experiment. If a tracepoint's passcount is
14610 @var{n}, then the trace experiment will be automatically stopped on
14611 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14612 @var{num} is not specified, the @code{passcount} command sets the
14613 passcount of the most recently defined tracepoint. If no passcount is
14614 given, the trace experiment will run until stopped explicitly by the
14620 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14621 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14623 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14624 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14625 (@value{GDBP}) @b{trace foo}
14626 (@value{GDBP}) @b{pass 3}
14627 (@value{GDBP}) @b{trace bar}
14628 (@value{GDBP}) @b{pass 2}
14629 (@value{GDBP}) @b{trace baz}
14630 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14631 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14632 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14633 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14637 @node Tracepoint Conditions
14638 @subsection Tracepoint Conditions
14639 @cindex conditional tracepoints
14640 @cindex tracepoint conditions
14642 The simplest sort of tracepoint collects data every time your program
14643 reaches a specified place. You can also specify a @dfn{condition} for
14644 a tracepoint. A condition is just a Boolean expression in your
14645 programming language (@pxref{Expressions, ,Expressions}). A
14646 tracepoint with a condition evaluates the expression each time your
14647 program reaches it, and data collection happens only if the condition
14650 Tracepoint conditions can be specified when a tracepoint is set, by
14651 using @samp{if} in the arguments to the @code{trace} command.
14652 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14653 also be set or changed at any time with the @code{condition} command,
14654 just as with breakpoints.
14656 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14657 the conditional expression itself. Instead, @value{GDBN} encodes the
14658 expression into an agent expression (@pxref{Agent Expressions})
14659 suitable for execution on the target, independently of @value{GDBN}.
14660 Global variables become raw memory locations, locals become stack
14661 accesses, and so forth.
14663 For instance, suppose you have a function that is usually called
14664 frequently, but should not be called after an error has occurred. You
14665 could use the following tracepoint command to collect data about calls
14666 of that function that happen while the error code is propagating
14667 through the program; an unconditional tracepoint could end up
14668 collecting thousands of useless trace frames that you would have to
14672 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14675 @node Trace State Variables
14676 @subsection Trace State Variables
14677 @cindex trace state variables
14679 A @dfn{trace state variable} is a special type of variable that is
14680 created and managed by target-side code. The syntax is the same as
14681 that for GDB's convenience variables (a string prefixed with ``$''),
14682 but they are stored on the target. They must be created explicitly,
14683 using a @code{tvariable} command. They are always 64-bit signed
14686 Trace state variables are remembered by @value{GDBN}, and downloaded
14687 to the target along with tracepoint information when the trace
14688 experiment starts. There are no intrinsic limits on the number of
14689 trace state variables, beyond memory limitations of the target.
14691 @cindex convenience variables, and trace state variables
14692 Although trace state variables are managed by the target, you can use
14693 them in print commands and expressions as if they were convenience
14694 variables; @value{GDBN} will get the current value from the target
14695 while the trace experiment is running. Trace state variables share
14696 the same namespace as other ``$'' variables, which means that you
14697 cannot have trace state variables with names like @code{$23} or
14698 @code{$pc}, nor can you have a trace state variable and a convenience
14699 variable with the same name.
14703 @item tvariable $@var{name} [ = @var{expression} ]
14705 The @code{tvariable} command creates a new trace state variable named
14706 @code{$@var{name}}, and optionally gives it an initial value of
14707 @var{expression}. The @var{expression} is evaluated when this command is
14708 entered; the result will be converted to an integer if possible,
14709 otherwise @value{GDBN} will report an error. A subsequent
14710 @code{tvariable} command specifying the same name does not create a
14711 variable, but instead assigns the supplied initial value to the
14712 existing variable of that name, overwriting any previous initial
14713 value. The default initial value is 0.
14715 @item info tvariables
14716 @kindex info tvariables
14717 List all the trace state variables along with their initial values.
14718 Their current values may also be displayed, if the trace experiment is
14721 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14722 @kindex delete tvariable
14723 Delete the given trace state variables, or all of them if no arguments
14728 @node Tracepoint Actions
14729 @subsection Tracepoint Action Lists
14733 @cindex tracepoint actions
14734 @item actions @r{[}@var{num}@r{]}
14735 This command will prompt for a list of actions to be taken when the
14736 tracepoint is hit. If the tracepoint number @var{num} is not
14737 specified, this command sets the actions for the one that was most
14738 recently defined (so that you can define a tracepoint and then say
14739 @code{actions} without bothering about its number). You specify the
14740 actions themselves on the following lines, one action at a time, and
14741 terminate the actions list with a line containing just @code{end}. So
14742 far, the only defined actions are @code{collect}, @code{teval}, and
14743 @code{while-stepping}.
14745 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14746 Commands, ,Breakpoint Command Lists}), except that only the defined
14747 actions are allowed; any other @value{GDBN} command is rejected.
14749 @cindex remove actions from a tracepoint
14750 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14751 and follow it immediately with @samp{end}.
14754 (@value{GDBP}) @b{collect @var{data}} // collect some data
14756 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14758 (@value{GDBP}) @b{end} // signals the end of actions.
14761 In the following example, the action list begins with @code{collect}
14762 commands indicating the things to be collected when the tracepoint is
14763 hit. Then, in order to single-step and collect additional data
14764 following the tracepoint, a @code{while-stepping} command is used,
14765 followed by the list of things to be collected after each step in a
14766 sequence of single steps. The @code{while-stepping} command is
14767 terminated by its own separate @code{end} command. Lastly, the action
14768 list is terminated by an @code{end} command.
14771 (@value{GDBP}) @b{trace foo}
14772 (@value{GDBP}) @b{actions}
14773 Enter actions for tracepoint 1, one per line:
14776 > while-stepping 12
14777 > collect $pc, arr[i]
14782 @kindex collect @r{(tracepoints)}
14783 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14784 Collect values of the given expressions when the tracepoint is hit.
14785 This command accepts a comma-separated list of any valid expressions.
14786 In addition to global, static, or local variables, the following
14787 special arguments are supported:
14791 Collect all registers.
14794 Collect all function arguments.
14797 Collect all local variables.
14800 Collect the return address. This is helpful if you want to see more
14803 @emph{Note:} The return address location can not always be reliably
14804 determined up front, and the wrong address / registers may end up
14805 collected instead. On some architectures the reliability is higher
14806 for tracepoints at function entry, while on others it's the opposite.
14807 When this happens, backtracing will stop because the return address is
14808 found unavailable (unless another collect rule happened to match it).
14811 Collects the number of arguments from the static probe at which the
14812 tracepoint is located.
14813 @xref{Static Probe Points}.
14815 @item $_probe_arg@var{n}
14816 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14817 from the static probe at which the tracepoint is located.
14818 @xref{Static Probe Points}.
14821 @vindex $_sdata@r{, collect}
14822 Collect static tracepoint marker specific data. Only available for
14823 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14824 Lists}. On the UST static tracepoints library backend, an
14825 instrumentation point resembles a @code{printf} function call. The
14826 tracing library is able to collect user specified data formatted to a
14827 character string using the format provided by the programmer that
14828 instrumented the program. Other backends have similar mechanisms.
14829 Here's an example of a UST marker call:
14832 const char master_name[] = "$your_name";
14833 trace_mark(channel1, marker1, "hello %s", master_name)
14836 In this case, collecting @code{$_sdata} collects the string
14837 @samp{hello $yourname}. When analyzing the trace buffer, you can
14838 inspect @samp{$_sdata} like any other variable available to
14842 You can give several consecutive @code{collect} commands, each one
14843 with a single argument, or one @code{collect} command with several
14844 arguments separated by commas; the effect is the same.
14846 The optional @var{mods} changes the usual handling of the arguments.
14847 @code{s} requests that pointers to chars be handled as strings, in
14848 particular collecting the contents of the memory being pointed at, up
14849 to the first zero. The upper bound is by default the value of the
14850 @code{print elements} variable; if @code{s} is followed by a decimal
14851 number, that is the upper bound instead. So for instance
14852 @samp{collect/s25 mystr} collects as many as 25 characters at
14855 The command @code{info scope} (@pxref{Symbols, info scope}) is
14856 particularly useful for figuring out what data to collect.
14858 @kindex teval @r{(tracepoints)}
14859 @item teval @var{expr1}, @var{expr2}, @dots{}
14860 Evaluate the given expressions when the tracepoint is hit. This
14861 command accepts a comma-separated list of expressions. The results
14862 are discarded, so this is mainly useful for assigning values to trace
14863 state variables (@pxref{Trace State Variables}) without adding those
14864 values to the trace buffer, as would be the case if the @code{collect}
14867 @kindex while-stepping @r{(tracepoints)}
14868 @item while-stepping @var{n}
14869 Perform @var{n} single-step instruction traces after the tracepoint,
14870 collecting new data after each step. The @code{while-stepping}
14871 command is followed by the list of what to collect while stepping
14872 (followed by its own @code{end} command):
14875 > while-stepping 12
14876 > collect $regs, myglobal
14882 Note that @code{$pc} is not automatically collected by
14883 @code{while-stepping}; you need to explicitly collect that register if
14884 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14887 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14888 @kindex set default-collect
14889 @cindex default collection action
14890 This variable is a list of expressions to collect at each tracepoint
14891 hit. It is effectively an additional @code{collect} action prepended
14892 to every tracepoint action list. The expressions are parsed
14893 individually for each tracepoint, so for instance a variable named
14894 @code{xyz} may be interpreted as a global for one tracepoint, and a
14895 local for another, as appropriate to the tracepoint's location.
14897 @item show default-collect
14898 @kindex show default-collect
14899 Show the list of expressions that are collected by default at each
14904 @node Listing Tracepoints
14905 @subsection Listing Tracepoints
14908 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14909 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14910 @cindex information about tracepoints
14911 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14912 Display information about the tracepoint @var{num}. If you don't
14913 specify a tracepoint number, displays information about all the
14914 tracepoints defined so far. The format is similar to that used for
14915 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14916 command, simply restricting itself to tracepoints.
14918 A tracepoint's listing may include additional information specific to
14923 its passcount as given by the @code{passcount @var{n}} command
14926 the state about installed on target of each location
14930 (@value{GDBP}) @b{info trace}
14931 Num Type Disp Enb Address What
14932 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14934 collect globfoo, $regs
14939 2 tracepoint keep y <MULTIPLE>
14941 2.1 y 0x0804859c in func4 at change-loc.h:35
14942 installed on target
14943 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14944 installed on target
14945 2.3 y <PENDING> set_tracepoint
14946 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14947 not installed on target
14952 This command can be abbreviated @code{info tp}.
14955 @node Listing Static Tracepoint Markers
14956 @subsection Listing Static Tracepoint Markers
14959 @kindex info static-tracepoint-markers
14960 @cindex information about static tracepoint markers
14961 @item info static-tracepoint-markers
14962 Display information about all static tracepoint markers defined in the
14965 For each marker, the following columns are printed:
14969 An incrementing counter, output to help readability. This is not a
14972 The marker ID, as reported by the target.
14973 @item Enabled or Disabled
14974 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14975 that are not enabled.
14977 Where the marker is in your program, as a memory address.
14979 Where the marker is in the source for your program, as a file and line
14980 number. If the debug information included in the program does not
14981 allow @value{GDBN} to locate the source of the marker, this column
14982 will be left blank.
14986 In addition, the following information may be printed for each marker:
14990 User data passed to the tracing library by the marker call. In the
14991 UST backend, this is the format string passed as argument to the
14993 @item Static tracepoints probing the marker
14994 The list of static tracepoints attached to the marker.
14998 (@value{GDBP}) info static-tracepoint-markers
14999 Cnt ID Enb Address What
15000 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15001 Data: number1 %d number2 %d
15002 Probed by static tracepoints: #2
15003 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15009 @node Starting and Stopping Trace Experiments
15010 @subsection Starting and Stopping Trace Experiments
15013 @kindex tstart [ @var{notes} ]
15014 @cindex start a new trace experiment
15015 @cindex collected data discarded
15017 This command starts the trace experiment, and begins collecting data.
15018 It has the side effect of discarding all the data collected in the
15019 trace buffer during the previous trace experiment. If any arguments
15020 are supplied, they are taken as a note and stored with the trace
15021 experiment's state. The notes may be arbitrary text, and are
15022 especially useful with disconnected tracing in a multi-user context;
15023 the notes can explain what the trace is doing, supply user contact
15024 information, and so forth.
15026 @kindex tstop [ @var{notes} ]
15027 @cindex stop a running trace experiment
15029 This command stops the trace experiment. If any arguments are
15030 supplied, they are recorded with the experiment as a note. This is
15031 useful if you are stopping a trace started by someone else, for
15032 instance if the trace is interfering with the system's behavior and
15033 needs to be stopped quickly.
15035 @strong{Note}: a trace experiment and data collection may stop
15036 automatically if any tracepoint's passcount is reached
15037 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15040 @cindex status of trace data collection
15041 @cindex trace experiment, status of
15043 This command displays the status of the current trace data
15047 Here is an example of the commands we described so far:
15050 (@value{GDBP}) @b{trace gdb_c_test}
15051 (@value{GDBP}) @b{actions}
15052 Enter actions for tracepoint #1, one per line.
15053 > collect $regs,$locals,$args
15054 > while-stepping 11
15058 (@value{GDBP}) @b{tstart}
15059 [time passes @dots{}]
15060 (@value{GDBP}) @b{tstop}
15063 @anchor{disconnected tracing}
15064 @cindex disconnected tracing
15065 You can choose to continue running the trace experiment even if
15066 @value{GDBN} disconnects from the target, voluntarily or
15067 involuntarily. For commands such as @code{detach}, the debugger will
15068 ask what you want to do with the trace. But for unexpected
15069 terminations (@value{GDBN} crash, network outage), it would be
15070 unfortunate to lose hard-won trace data, so the variable
15071 @code{disconnected-tracing} lets you decide whether the trace should
15072 continue running without @value{GDBN}.
15075 @item set disconnected-tracing on
15076 @itemx set disconnected-tracing off
15077 @kindex set disconnected-tracing
15078 Choose whether a tracing run should continue to run if @value{GDBN}
15079 has disconnected from the target. Note that @code{detach} or
15080 @code{quit} will ask you directly what to do about a running trace no
15081 matter what this variable's setting, so the variable is mainly useful
15082 for handling unexpected situations, such as loss of the network.
15084 @item show disconnected-tracing
15085 @kindex show disconnected-tracing
15086 Show the current choice for disconnected tracing.
15090 When you reconnect to the target, the trace experiment may or may not
15091 still be running; it might have filled the trace buffer in the
15092 meantime, or stopped for one of the other reasons. If it is running,
15093 it will continue after reconnection.
15095 Upon reconnection, the target will upload information about the
15096 tracepoints in effect. @value{GDBN} will then compare that
15097 information to the set of tracepoints currently defined, and attempt
15098 to match them up, allowing for the possibility that the numbers may
15099 have changed due to creation and deletion in the meantime. If one of
15100 the target's tracepoints does not match any in @value{GDBN}, the
15101 debugger will create a new tracepoint, so that you have a number with
15102 which to specify that tracepoint. This matching-up process is
15103 necessarily heuristic, and it may result in useless tracepoints being
15104 created; you may simply delete them if they are of no use.
15106 @cindex circular trace buffer
15107 If your target agent supports a @dfn{circular trace buffer}, then you
15108 can run a trace experiment indefinitely without filling the trace
15109 buffer; when space runs out, the agent deletes already-collected trace
15110 frames, oldest first, until there is enough room to continue
15111 collecting. This is especially useful if your tracepoints are being
15112 hit too often, and your trace gets terminated prematurely because the
15113 buffer is full. To ask for a circular trace buffer, simply set
15114 @samp{circular-trace-buffer} to on. You can set this at any time,
15115 including during tracing; if the agent can do it, it will change
15116 buffer handling on the fly, otherwise it will not take effect until
15120 @item set circular-trace-buffer on
15121 @itemx set circular-trace-buffer off
15122 @kindex set circular-trace-buffer
15123 Choose whether a tracing run should use a linear or circular buffer
15124 for trace data. A linear buffer will not lose any trace data, but may
15125 fill up prematurely, while a circular buffer will discard old trace
15126 data, but it will have always room for the latest tracepoint hits.
15128 @item show circular-trace-buffer
15129 @kindex show circular-trace-buffer
15130 Show the current choice for the trace buffer. Note that this may not
15131 match the agent's current buffer handling, nor is it guaranteed to
15132 match the setting that might have been in effect during a past run,
15133 for instance if you are looking at frames from a trace file.
15138 @item set trace-buffer-size @var{n}
15139 @itemx set trace-buffer-size unlimited
15140 @kindex set trace-buffer-size
15141 Request that the target use a trace buffer of @var{n} bytes. Not all
15142 targets will honor the request; they may have a compiled-in size for
15143 the trace buffer, or some other limitation. Set to a value of
15144 @code{unlimited} or @code{-1} to let the target use whatever size it
15145 likes. This is also the default.
15147 @item show trace-buffer-size
15148 @kindex show trace-buffer-size
15149 Show the current requested size for the trace buffer. Note that this
15150 will only match the actual size if the target supports size-setting,
15151 and was able to handle the requested size. For instance, if the
15152 target can only change buffer size between runs, this variable will
15153 not reflect the change until the next run starts. Use @code{tstatus}
15154 to get a report of the actual buffer size.
15158 @item set trace-user @var{text}
15159 @kindex set trace-user
15161 @item show trace-user
15162 @kindex show trace-user
15164 @item set trace-notes @var{text}
15165 @kindex set trace-notes
15166 Set the trace run's notes.
15168 @item show trace-notes
15169 @kindex show trace-notes
15170 Show the trace run's notes.
15172 @item set trace-stop-notes @var{text}
15173 @kindex set trace-stop-notes
15174 Set the trace run's stop notes. The handling of the note is as for
15175 @code{tstop} arguments; the set command is convenient way to fix a
15176 stop note that is mistaken or incomplete.
15178 @item show trace-stop-notes
15179 @kindex show trace-stop-notes
15180 Show the trace run's stop notes.
15184 @node Tracepoint Restrictions
15185 @subsection Tracepoint Restrictions
15187 @cindex tracepoint restrictions
15188 There are a number of restrictions on the use of tracepoints. As
15189 described above, tracepoint data gathering occurs on the target
15190 without interaction from @value{GDBN}. Thus the full capabilities of
15191 the debugger are not available during data gathering, and then at data
15192 examination time, you will be limited by only having what was
15193 collected. The following items describe some common problems, but it
15194 is not exhaustive, and you may run into additional difficulties not
15200 Tracepoint expressions are intended to gather objects (lvalues). Thus
15201 the full flexibility of GDB's expression evaluator is not available.
15202 You cannot call functions, cast objects to aggregate types, access
15203 convenience variables or modify values (except by assignment to trace
15204 state variables). Some language features may implicitly call
15205 functions (for instance Objective-C fields with accessors), and therefore
15206 cannot be collected either.
15209 Collection of local variables, either individually or in bulk with
15210 @code{$locals} or @code{$args}, during @code{while-stepping} may
15211 behave erratically. The stepping action may enter a new scope (for
15212 instance by stepping into a function), or the location of the variable
15213 may change (for instance it is loaded into a register). The
15214 tracepoint data recorded uses the location information for the
15215 variables that is correct for the tracepoint location. When the
15216 tracepoint is created, it is not possible, in general, to determine
15217 where the steps of a @code{while-stepping} sequence will advance the
15218 program---particularly if a conditional branch is stepped.
15221 Collection of an incompletely-initialized or partially-destroyed object
15222 may result in something that @value{GDBN} cannot display, or displays
15223 in a misleading way.
15226 When @value{GDBN} displays a pointer to character it automatically
15227 dereferences the pointer to also display characters of the string
15228 being pointed to. However, collecting the pointer during tracing does
15229 not automatically collect the string. You need to explicitly
15230 dereference the pointer and provide size information if you want to
15231 collect not only the pointer, but the memory pointed to. For example,
15232 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15236 It is not possible to collect a complete stack backtrace at a
15237 tracepoint. Instead, you may collect the registers and a few hundred
15238 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15239 (adjust to use the name of the actual stack pointer register on your
15240 target architecture, and the amount of stack you wish to capture).
15241 Then the @code{backtrace} command will show a partial backtrace when
15242 using a trace frame. The number of stack frames that can be examined
15243 depends on the sizes of the frames in the collected stack. Note that
15244 if you ask for a block so large that it goes past the bottom of the
15245 stack, the target agent may report an error trying to read from an
15249 If you do not collect registers at a tracepoint, @value{GDBN} can
15250 infer that the value of @code{$pc} must be the same as the address of
15251 the tracepoint and use that when you are looking at a trace frame
15252 for that tracepoint. However, this cannot work if the tracepoint has
15253 multiple locations (for instance if it was set in a function that was
15254 inlined), or if it has a @code{while-stepping} loop. In those cases
15255 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15260 @node Analyze Collected Data
15261 @section Using the Collected Data
15263 After the tracepoint experiment ends, you use @value{GDBN} commands
15264 for examining the trace data. The basic idea is that each tracepoint
15265 collects a trace @dfn{snapshot} every time it is hit and another
15266 snapshot every time it single-steps. All these snapshots are
15267 consecutively numbered from zero and go into a buffer, and you can
15268 examine them later. The way you examine them is to @dfn{focus} on a
15269 specific trace snapshot. When the remote stub is focused on a trace
15270 snapshot, it will respond to all @value{GDBN} requests for memory and
15271 registers by reading from the buffer which belongs to that snapshot,
15272 rather than from @emph{real} memory or registers of the program being
15273 debugged. This means that @strong{all} @value{GDBN} commands
15274 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15275 behave as if we were currently debugging the program state as it was
15276 when the tracepoint occurred. Any requests for data that are not in
15277 the buffer will fail.
15280 * tfind:: How to select a trace snapshot
15281 * tdump:: How to display all data for a snapshot
15282 * save tracepoints:: How to save tracepoints for a future run
15286 @subsection @code{tfind @var{n}}
15289 @cindex select trace snapshot
15290 @cindex find trace snapshot
15291 The basic command for selecting a trace snapshot from the buffer is
15292 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15293 counting from zero. If no argument @var{n} is given, the next
15294 snapshot is selected.
15296 Here are the various forms of using the @code{tfind} command.
15300 Find the first snapshot in the buffer. This is a synonym for
15301 @code{tfind 0} (since 0 is the number of the first snapshot).
15304 Stop debugging trace snapshots, resume @emph{live} debugging.
15307 Same as @samp{tfind none}.
15310 No argument means find the next trace snapshot or find the first
15311 one if no trace snapshot is selected.
15314 Find the previous trace snapshot before the current one. This permits
15315 retracing earlier steps.
15317 @item tfind tracepoint @var{num}
15318 Find the next snapshot associated with tracepoint @var{num}. Search
15319 proceeds forward from the last examined trace snapshot. If no
15320 argument @var{num} is given, it means find the next snapshot collected
15321 for the same tracepoint as the current snapshot.
15323 @item tfind pc @var{addr}
15324 Find the next snapshot associated with the value @var{addr} of the
15325 program counter. Search proceeds forward from the last examined trace
15326 snapshot. If no argument @var{addr} is given, it means find the next
15327 snapshot with the same value of PC as the current snapshot.
15329 @item tfind outside @var{addr1}, @var{addr2}
15330 Find the next snapshot whose PC is outside the given range of
15331 addresses (exclusive).
15333 @item tfind range @var{addr1}, @var{addr2}
15334 Find the next snapshot whose PC is between @var{addr1} and
15335 @var{addr2} (inclusive).
15337 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15338 Find the next snapshot associated with the source line @var{n}. If
15339 the optional argument @var{file} is given, refer to line @var{n} in
15340 that source file. Search proceeds forward from the last examined
15341 trace snapshot. If no argument @var{n} is given, it means find the
15342 next line other than the one currently being examined; thus saying
15343 @code{tfind line} repeatedly can appear to have the same effect as
15344 stepping from line to line in a @emph{live} debugging session.
15347 The default arguments for the @code{tfind} commands are specifically
15348 designed to make it easy to scan through the trace buffer. For
15349 instance, @code{tfind} with no argument selects the next trace
15350 snapshot, and @code{tfind -} with no argument selects the previous
15351 trace snapshot. So, by giving one @code{tfind} command, and then
15352 simply hitting @key{RET} repeatedly you can examine all the trace
15353 snapshots in order. Or, by saying @code{tfind -} and then hitting
15354 @key{RET} repeatedly you can examine the snapshots in reverse order.
15355 The @code{tfind line} command with no argument selects the snapshot
15356 for the next source line executed. The @code{tfind pc} command with
15357 no argument selects the next snapshot with the same program counter
15358 (PC) as the current frame. The @code{tfind tracepoint} command with
15359 no argument selects the next trace snapshot collected by the same
15360 tracepoint as the current one.
15362 In addition to letting you scan through the trace buffer manually,
15363 these commands make it easy to construct @value{GDBN} scripts that
15364 scan through the trace buffer and print out whatever collected data
15365 you are interested in. Thus, if we want to examine the PC, FP, and SP
15366 registers from each trace frame in the buffer, we can say this:
15369 (@value{GDBP}) @b{tfind start}
15370 (@value{GDBP}) @b{while ($trace_frame != -1)}
15371 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15372 $trace_frame, $pc, $sp, $fp
15376 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15377 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15378 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15379 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15380 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15381 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15382 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15383 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15384 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15385 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15386 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15389 Or, if we want to examine the variable @code{X} at each source line in
15393 (@value{GDBP}) @b{tfind start}
15394 (@value{GDBP}) @b{while ($trace_frame != -1)}
15395 > printf "Frame %d, X == %d\n", $trace_frame, X
15405 @subsection @code{tdump}
15407 @cindex dump all data collected at tracepoint
15408 @cindex tracepoint data, display
15410 This command takes no arguments. It prints all the data collected at
15411 the current trace snapshot.
15414 (@value{GDBP}) @b{trace 444}
15415 (@value{GDBP}) @b{actions}
15416 Enter actions for tracepoint #2, one per line:
15417 > collect $regs, $locals, $args, gdb_long_test
15420 (@value{GDBP}) @b{tstart}
15422 (@value{GDBP}) @b{tfind line 444}
15423 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15425 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15427 (@value{GDBP}) @b{tdump}
15428 Data collected at tracepoint 2, trace frame 1:
15429 d0 0xc4aa0085 -995491707
15433 d4 0x71aea3d 119204413
15436 d7 0x380035 3670069
15437 a0 0x19e24a 1696330
15438 a1 0x3000668 50333288
15440 a3 0x322000 3284992
15441 a4 0x3000698 50333336
15442 a5 0x1ad3cc 1758156
15443 fp 0x30bf3c 0x30bf3c
15444 sp 0x30bf34 0x30bf34
15446 pc 0x20b2c8 0x20b2c8
15450 p = 0x20e5b4 "gdb-test"
15457 gdb_long_test = 17 '\021'
15462 @code{tdump} works by scanning the tracepoint's current collection
15463 actions and printing the value of each expression listed. So
15464 @code{tdump} can fail, if after a run, you change the tracepoint's
15465 actions to mention variables that were not collected during the run.
15467 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15468 uses the collected value of @code{$pc} to distinguish between trace
15469 frames that were collected at the tracepoint hit, and frames that were
15470 collected while stepping. This allows it to correctly choose whether
15471 to display the basic list of collections, or the collections from the
15472 body of the while-stepping loop. However, if @code{$pc} was not collected,
15473 then @code{tdump} will always attempt to dump using the basic collection
15474 list, and may fail if a while-stepping frame does not include all the
15475 same data that is collected at the tracepoint hit.
15476 @c This is getting pretty arcane, example would be good.
15478 @node save tracepoints
15479 @subsection @code{save tracepoints @var{filename}}
15480 @kindex save tracepoints
15481 @kindex save-tracepoints
15482 @cindex save tracepoints for future sessions
15484 This command saves all current tracepoint definitions together with
15485 their actions and passcounts, into a file @file{@var{filename}}
15486 suitable for use in a later debugging session. To read the saved
15487 tracepoint definitions, use the @code{source} command (@pxref{Command
15488 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15489 alias for @w{@code{save tracepoints}}
15491 @node Tracepoint Variables
15492 @section Convenience Variables for Tracepoints
15493 @cindex tracepoint variables
15494 @cindex convenience variables for tracepoints
15497 @vindex $trace_frame
15498 @item (int) $trace_frame
15499 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15500 snapshot is selected.
15502 @vindex $tracepoint
15503 @item (int) $tracepoint
15504 The tracepoint for the current trace snapshot.
15506 @vindex $trace_line
15507 @item (int) $trace_line
15508 The line number for the current trace snapshot.
15510 @vindex $trace_file
15511 @item (char []) $trace_file
15512 The source file for the current trace snapshot.
15514 @vindex $trace_func
15515 @item (char []) $trace_func
15516 The name of the function containing @code{$tracepoint}.
15519 Note: @code{$trace_file} is not suitable for use in @code{printf},
15520 use @code{output} instead.
15522 Here's a simple example of using these convenience variables for
15523 stepping through all the trace snapshots and printing some of their
15524 data. Note that these are not the same as trace state variables,
15525 which are managed by the target.
15528 (@value{GDBP}) @b{tfind start}
15530 (@value{GDBP}) @b{while $trace_frame != -1}
15531 > output $trace_file
15532 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15538 @section Using Trace Files
15539 @cindex trace files
15541 In some situations, the target running a trace experiment may no
15542 longer be available; perhaps it crashed, or the hardware was needed
15543 for a different activity. To handle these cases, you can arrange to
15544 dump the trace data into a file, and later use that file as a source
15545 of trace data, via the @code{target tfile} command.
15550 @item tsave [ -r ] @var{filename}
15551 @itemx tsave [-ctf] @var{dirname}
15552 Save the trace data to @var{filename}. By default, this command
15553 assumes that @var{filename} refers to the host filesystem, so if
15554 necessary @value{GDBN} will copy raw trace data up from the target and
15555 then save it. If the target supports it, you can also supply the
15556 optional argument @code{-r} (``remote'') to direct the target to save
15557 the data directly into @var{filename} in its own filesystem, which may be
15558 more efficient if the trace buffer is very large. (Note, however, that
15559 @code{target tfile} can only read from files accessible to the host.)
15560 By default, this command will save trace frame in tfile format.
15561 You can supply the optional argument @code{-ctf} to save data in CTF
15562 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15563 that can be shared by multiple debugging and tracing tools. Please go to
15564 @indicateurl{http://www.efficios.com/ctf} to get more information.
15566 @kindex target tfile
15570 @item target tfile @var{filename}
15571 @itemx target ctf @var{dirname}
15572 Use the file named @var{filename} or directory named @var{dirname} as
15573 a source of trace data. Commands that examine data work as they do with
15574 a live target, but it is not possible to run any new trace experiments.
15575 @code{tstatus} will report the state of the trace run at the moment
15576 the data was saved, as well as the current trace frame you are examining.
15577 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15581 (@value{GDBP}) target ctf ctf.ctf
15582 (@value{GDBP}) tfind
15583 Found trace frame 0, tracepoint 2
15584 39 ++a; /* set tracepoint 1 here */
15585 (@value{GDBP}) tdump
15586 Data collected at tracepoint 2, trace frame 0:
15590 c = @{"123", "456", "789", "123", "456", "789"@}
15591 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15599 @chapter Debugging Programs That Use Overlays
15602 If your program is too large to fit completely in your target system's
15603 memory, you can sometimes use @dfn{overlays} to work around this
15604 problem. @value{GDBN} provides some support for debugging programs that
15608 * How Overlays Work:: A general explanation of overlays.
15609 * Overlay Commands:: Managing overlays in @value{GDBN}.
15610 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15611 mapped by asking the inferior.
15612 * Overlay Sample Program:: A sample program using overlays.
15615 @node How Overlays Work
15616 @section How Overlays Work
15617 @cindex mapped overlays
15618 @cindex unmapped overlays
15619 @cindex load address, overlay's
15620 @cindex mapped address
15621 @cindex overlay area
15623 Suppose you have a computer whose instruction address space is only 64
15624 kilobytes long, but which has much more memory which can be accessed by
15625 other means: special instructions, segment registers, or memory
15626 management hardware, for example. Suppose further that you want to
15627 adapt a program which is larger than 64 kilobytes to run on this system.
15629 One solution is to identify modules of your program which are relatively
15630 independent, and need not call each other directly; call these modules
15631 @dfn{overlays}. Separate the overlays from the main program, and place
15632 their machine code in the larger memory. Place your main program in
15633 instruction memory, but leave at least enough space there to hold the
15634 largest overlay as well.
15636 Now, to call a function located in an overlay, you must first copy that
15637 overlay's machine code from the large memory into the space set aside
15638 for it in the instruction memory, and then jump to its entry point
15641 @c NB: In the below the mapped area's size is greater or equal to the
15642 @c size of all overlays. This is intentional to remind the developer
15643 @c that overlays don't necessarily need to be the same size.
15647 Data Instruction Larger
15648 Address Space Address Space Address Space
15649 +-----------+ +-----------+ +-----------+
15651 +-----------+ +-----------+ +-----------+<-- overlay 1
15652 | program | | main | .----| overlay 1 | load address
15653 | variables | | program | | +-----------+
15654 | and heap | | | | | |
15655 +-----------+ | | | +-----------+<-- overlay 2
15656 | | +-----------+ | | | load address
15657 +-----------+ | | | .-| overlay 2 |
15659 mapped --->+-----------+ | | +-----------+
15660 address | | | | | |
15661 | overlay | <-' | | |
15662 | area | <---' +-----------+<-- overlay 3
15663 | | <---. | | load address
15664 +-----------+ `--| overlay 3 |
15671 @anchor{A code overlay}A code overlay
15675 The diagram (@pxref{A code overlay}) shows a system with separate data
15676 and instruction address spaces. To map an overlay, the program copies
15677 its code from the larger address space to the instruction address space.
15678 Since the overlays shown here all use the same mapped address, only one
15679 may be mapped at a time. For a system with a single address space for
15680 data and instructions, the diagram would be similar, except that the
15681 program variables and heap would share an address space with the main
15682 program and the overlay area.
15684 An overlay loaded into instruction memory and ready for use is called a
15685 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15686 instruction memory. An overlay not present (or only partially present)
15687 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15688 is its address in the larger memory. The mapped address is also called
15689 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15690 called the @dfn{load memory address}, or @dfn{LMA}.
15692 Unfortunately, overlays are not a completely transparent way to adapt a
15693 program to limited instruction memory. They introduce a new set of
15694 global constraints you must keep in mind as you design your program:
15699 Before calling or returning to a function in an overlay, your program
15700 must make sure that overlay is actually mapped. Otherwise, the call or
15701 return will transfer control to the right address, but in the wrong
15702 overlay, and your program will probably crash.
15705 If the process of mapping an overlay is expensive on your system, you
15706 will need to choose your overlays carefully to minimize their effect on
15707 your program's performance.
15710 The executable file you load onto your system must contain each
15711 overlay's instructions, appearing at the overlay's load address, not its
15712 mapped address. However, each overlay's instructions must be relocated
15713 and its symbols defined as if the overlay were at its mapped address.
15714 You can use GNU linker scripts to specify different load and relocation
15715 addresses for pieces of your program; see @ref{Overlay Description,,,
15716 ld.info, Using ld: the GNU linker}.
15719 The procedure for loading executable files onto your system must be able
15720 to load their contents into the larger address space as well as the
15721 instruction and data spaces.
15725 The overlay system described above is rather simple, and could be
15726 improved in many ways:
15731 If your system has suitable bank switch registers or memory management
15732 hardware, you could use those facilities to make an overlay's load area
15733 contents simply appear at their mapped address in instruction space.
15734 This would probably be faster than copying the overlay to its mapped
15735 area in the usual way.
15738 If your overlays are small enough, you could set aside more than one
15739 overlay area, and have more than one overlay mapped at a time.
15742 You can use overlays to manage data, as well as instructions. In
15743 general, data overlays are even less transparent to your design than
15744 code overlays: whereas code overlays only require care when you call or
15745 return to functions, data overlays require care every time you access
15746 the data. Also, if you change the contents of a data overlay, you
15747 must copy its contents back out to its load address before you can copy a
15748 different data overlay into the same mapped area.
15753 @node Overlay Commands
15754 @section Overlay Commands
15756 To use @value{GDBN}'s overlay support, each overlay in your program must
15757 correspond to a separate section of the executable file. The section's
15758 virtual memory address and load memory address must be the overlay's
15759 mapped and load addresses. Identifying overlays with sections allows
15760 @value{GDBN} to determine the appropriate address of a function or
15761 variable, depending on whether the overlay is mapped or not.
15763 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15764 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15769 Disable @value{GDBN}'s overlay support. When overlay support is
15770 disabled, @value{GDBN} assumes that all functions and variables are
15771 always present at their mapped addresses. By default, @value{GDBN}'s
15772 overlay support is disabled.
15774 @item overlay manual
15775 @cindex manual overlay debugging
15776 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15777 relies on you to tell it which overlays are mapped, and which are not,
15778 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15779 commands described below.
15781 @item overlay map-overlay @var{overlay}
15782 @itemx overlay map @var{overlay}
15783 @cindex map an overlay
15784 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15785 be the name of the object file section containing the overlay. When an
15786 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15787 functions and variables at their mapped addresses. @value{GDBN} assumes
15788 that any other overlays whose mapped ranges overlap that of
15789 @var{overlay} are now unmapped.
15791 @item overlay unmap-overlay @var{overlay}
15792 @itemx overlay unmap @var{overlay}
15793 @cindex unmap an overlay
15794 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15795 must be the name of the object file section containing the overlay.
15796 When an overlay is unmapped, @value{GDBN} assumes it can find the
15797 overlay's functions and variables at their load addresses.
15800 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15801 consults a data structure the overlay manager maintains in the inferior
15802 to see which overlays are mapped. For details, see @ref{Automatic
15803 Overlay Debugging}.
15805 @item overlay load-target
15806 @itemx overlay load
15807 @cindex reloading the overlay table
15808 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15809 re-reads the table @value{GDBN} automatically each time the inferior
15810 stops, so this command should only be necessary if you have changed the
15811 overlay mapping yourself using @value{GDBN}. This command is only
15812 useful when using automatic overlay debugging.
15814 @item overlay list-overlays
15815 @itemx overlay list
15816 @cindex listing mapped overlays
15817 Display a list of the overlays currently mapped, along with their mapped
15818 addresses, load addresses, and sizes.
15822 Normally, when @value{GDBN} prints a code address, it includes the name
15823 of the function the address falls in:
15826 (@value{GDBP}) print main
15827 $3 = @{int ()@} 0x11a0 <main>
15830 When overlay debugging is enabled, @value{GDBN} recognizes code in
15831 unmapped overlays, and prints the names of unmapped functions with
15832 asterisks around them. For example, if @code{foo} is a function in an
15833 unmapped overlay, @value{GDBN} prints it this way:
15836 (@value{GDBP}) overlay list
15837 No sections are mapped.
15838 (@value{GDBP}) print foo
15839 $5 = @{int (int)@} 0x100000 <*foo*>
15842 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15846 (@value{GDBP}) overlay list
15847 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15848 mapped at 0x1016 - 0x104a
15849 (@value{GDBP}) print foo
15850 $6 = @{int (int)@} 0x1016 <foo>
15853 When overlay debugging is enabled, @value{GDBN} can find the correct
15854 address for functions and variables in an overlay, whether or not the
15855 overlay is mapped. This allows most @value{GDBN} commands, like
15856 @code{break} and @code{disassemble}, to work normally, even on unmapped
15857 code. However, @value{GDBN}'s breakpoint support has some limitations:
15861 @cindex breakpoints in overlays
15862 @cindex overlays, setting breakpoints in
15863 You can set breakpoints in functions in unmapped overlays, as long as
15864 @value{GDBN} can write to the overlay at its load address.
15866 @value{GDBN} can not set hardware or simulator-based breakpoints in
15867 unmapped overlays. However, if you set a breakpoint at the end of your
15868 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15869 you are using manual overlay management), @value{GDBN} will re-set its
15870 breakpoints properly.
15874 @node Automatic Overlay Debugging
15875 @section Automatic Overlay Debugging
15876 @cindex automatic overlay debugging
15878 @value{GDBN} can automatically track which overlays are mapped and which
15879 are not, given some simple co-operation from the overlay manager in the
15880 inferior. If you enable automatic overlay debugging with the
15881 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15882 looks in the inferior's memory for certain variables describing the
15883 current state of the overlays.
15885 Here are the variables your overlay manager must define to support
15886 @value{GDBN}'s automatic overlay debugging:
15890 @item @code{_ovly_table}:
15891 This variable must be an array of the following structures:
15896 /* The overlay's mapped address. */
15899 /* The size of the overlay, in bytes. */
15900 unsigned long size;
15902 /* The overlay's load address. */
15905 /* Non-zero if the overlay is currently mapped;
15907 unsigned long mapped;
15911 @item @code{_novlys}:
15912 This variable must be a four-byte signed integer, holding the total
15913 number of elements in @code{_ovly_table}.
15917 To decide whether a particular overlay is mapped or not, @value{GDBN}
15918 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15919 @code{lma} members equal the VMA and LMA of the overlay's section in the
15920 executable file. When @value{GDBN} finds a matching entry, it consults
15921 the entry's @code{mapped} member to determine whether the overlay is
15924 In addition, your overlay manager may define a function called
15925 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15926 will silently set a breakpoint there. If the overlay manager then
15927 calls this function whenever it has changed the overlay table, this
15928 will enable @value{GDBN} to accurately keep track of which overlays
15929 are in program memory, and update any breakpoints that may be set
15930 in overlays. This will allow breakpoints to work even if the
15931 overlays are kept in ROM or other non-writable memory while they
15932 are not being executed.
15934 @node Overlay Sample Program
15935 @section Overlay Sample Program
15936 @cindex overlay example program
15938 When linking a program which uses overlays, you must place the overlays
15939 at their load addresses, while relocating them to run at their mapped
15940 addresses. To do this, you must write a linker script (@pxref{Overlay
15941 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15942 since linker scripts are specific to a particular host system, target
15943 architecture, and target memory layout, this manual cannot provide
15944 portable sample code demonstrating @value{GDBN}'s overlay support.
15946 However, the @value{GDBN} source distribution does contain an overlaid
15947 program, with linker scripts for a few systems, as part of its test
15948 suite. The program consists of the following files from
15949 @file{gdb/testsuite/gdb.base}:
15953 The main program file.
15955 A simple overlay manager, used by @file{overlays.c}.
15960 Overlay modules, loaded and used by @file{overlays.c}.
15963 Linker scripts for linking the test program on the @code{d10v-elf}
15964 and @code{m32r-elf} targets.
15967 You can build the test program using the @code{d10v-elf} GCC
15968 cross-compiler like this:
15971 $ d10v-elf-gcc -g -c overlays.c
15972 $ d10v-elf-gcc -g -c ovlymgr.c
15973 $ d10v-elf-gcc -g -c foo.c
15974 $ d10v-elf-gcc -g -c bar.c
15975 $ d10v-elf-gcc -g -c baz.c
15976 $ d10v-elf-gcc -g -c grbx.c
15977 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15978 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15981 The build process is identical for any other architecture, except that
15982 you must substitute the appropriate compiler and linker script for the
15983 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15987 @chapter Using @value{GDBN} with Different Languages
15990 Although programming languages generally have common aspects, they are
15991 rarely expressed in the same manner. For instance, in ANSI C,
15992 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15993 Modula-2, it is accomplished by @code{p^}. Values can also be
15994 represented (and displayed) differently. Hex numbers in C appear as
15995 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15997 @cindex working language
15998 Language-specific information is built into @value{GDBN} for some languages,
15999 allowing you to express operations like the above in your program's
16000 native language, and allowing @value{GDBN} to output values in a manner
16001 consistent with the syntax of your program's native language. The
16002 language you use to build expressions is called the @dfn{working
16006 * Setting:: Switching between source languages
16007 * Show:: Displaying the language
16008 * Checks:: Type and range checks
16009 * Supported Languages:: Supported languages
16010 * Unsupported Languages:: Unsupported languages
16014 @section Switching Between Source Languages
16016 There are two ways to control the working language---either have @value{GDBN}
16017 set it automatically, or select it manually yourself. You can use the
16018 @code{set language} command for either purpose. On startup, @value{GDBN}
16019 defaults to setting the language automatically. The working language is
16020 used to determine how expressions you type are interpreted, how values
16023 In addition to the working language, every source file that
16024 @value{GDBN} knows about has its own working language. For some object
16025 file formats, the compiler might indicate which language a particular
16026 source file is in. However, most of the time @value{GDBN} infers the
16027 language from the name of the file. The language of a source file
16028 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16029 show each frame appropriately for its own language. There is no way to
16030 set the language of a source file from within @value{GDBN}, but you can
16031 set the language associated with a filename extension. @xref{Show, ,
16032 Displaying the Language}.
16034 This is most commonly a problem when you use a program, such
16035 as @code{cfront} or @code{f2c}, that generates C but is written in
16036 another language. In that case, make the
16037 program use @code{#line} directives in its C output; that way
16038 @value{GDBN} will know the correct language of the source code of the original
16039 program, and will display that source code, not the generated C code.
16042 * Filenames:: Filename extensions and languages.
16043 * Manually:: Setting the working language manually
16044 * Automatically:: Having @value{GDBN} infer the source language
16048 @subsection List of Filename Extensions and Languages
16050 If a source file name ends in one of the following extensions, then
16051 @value{GDBN} infers that its language is the one indicated.
16069 C@t{++} source file
16075 Objective-C source file
16079 Fortran source file
16082 Modula-2 source file
16086 Assembler source file. This actually behaves almost like C, but
16087 @value{GDBN} does not skip over function prologues when stepping.
16090 In addition, you may set the language associated with a filename
16091 extension. @xref{Show, , Displaying the Language}.
16094 @subsection Setting the Working Language
16096 If you allow @value{GDBN} to set the language automatically,
16097 expressions are interpreted the same way in your debugging session and
16100 @kindex set language
16101 If you wish, you may set the language manually. To do this, issue the
16102 command @samp{set language @var{lang}}, where @var{lang} is the name of
16103 a language, such as
16104 @code{c} or @code{modula-2}.
16105 For a list of the supported languages, type @samp{set language}.
16107 Setting the language manually prevents @value{GDBN} from updating the working
16108 language automatically. This can lead to confusion if you try
16109 to debug a program when the working language is not the same as the
16110 source language, when an expression is acceptable to both
16111 languages---but means different things. For instance, if the current
16112 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16120 might not have the effect you intended. In C, this means to add
16121 @code{b} and @code{c} and place the result in @code{a}. The result
16122 printed would be the value of @code{a}. In Modula-2, this means to compare
16123 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16125 @node Automatically
16126 @subsection Having @value{GDBN} Infer the Source Language
16128 To have @value{GDBN} set the working language automatically, use
16129 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16130 then infers the working language. That is, when your program stops in a
16131 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16132 working language to the language recorded for the function in that
16133 frame. If the language for a frame is unknown (that is, if the function
16134 or block corresponding to the frame was defined in a source file that
16135 does not have a recognized extension), the current working language is
16136 not changed, and @value{GDBN} issues a warning.
16138 This may not seem necessary for most programs, which are written
16139 entirely in one source language. However, program modules and libraries
16140 written in one source language can be used by a main program written in
16141 a different source language. Using @samp{set language auto} in this
16142 case frees you from having to set the working language manually.
16145 @section Displaying the Language
16147 The following commands help you find out which language is the
16148 working language, and also what language source files were written in.
16151 @item show language
16152 @anchor{show language}
16153 @kindex show language
16154 Display the current working language. This is the
16155 language you can use with commands such as @code{print} to
16156 build and compute expressions that may involve variables in your program.
16159 @kindex info frame@r{, show the source language}
16160 Display the source language for this frame. This language becomes the
16161 working language if you use an identifier from this frame.
16162 @xref{Frame Info, ,Information about a Frame}, to identify the other
16163 information listed here.
16166 @kindex info source@r{, show the source language}
16167 Display the source language of this source file.
16168 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16169 information listed here.
16172 In unusual circumstances, you may have source files with extensions
16173 not in the standard list. You can then set the extension associated
16174 with a language explicitly:
16177 @item set extension-language @var{ext} @var{language}
16178 @kindex set extension-language
16179 Tell @value{GDBN} that source files with extension @var{ext} are to be
16180 assumed as written in the source language @var{language}.
16182 @item info extensions
16183 @kindex info extensions
16184 List all the filename extensions and the associated languages.
16188 @section Type and Range Checking
16190 Some languages are designed to guard you against making seemingly common
16191 errors through a series of compile- and run-time checks. These include
16192 checking the type of arguments to functions and operators and making
16193 sure mathematical overflows are caught at run time. Checks such as
16194 these help to ensure a program's correctness once it has been compiled
16195 by eliminating type mismatches and providing active checks for range
16196 errors when your program is running.
16198 By default @value{GDBN} checks for these errors according to the
16199 rules of the current source language. Although @value{GDBN} does not check
16200 the statements in your program, it can check expressions entered directly
16201 into @value{GDBN} for evaluation via the @code{print} command, for example.
16204 * Type Checking:: An overview of type checking
16205 * Range Checking:: An overview of range checking
16208 @cindex type checking
16209 @cindex checks, type
16210 @node Type Checking
16211 @subsection An Overview of Type Checking
16213 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16214 arguments to operators and functions have to be of the correct type,
16215 otherwise an error occurs. These checks prevent type mismatch
16216 errors from ever causing any run-time problems. For example,
16219 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16221 (@value{GDBP}) print obj.my_method (0)
16224 (@value{GDBP}) print obj.my_method (0x1234)
16225 Cannot resolve method klass::my_method to any overloaded instance
16228 The second example fails because in C@t{++} the integer constant
16229 @samp{0x1234} is not type-compatible with the pointer parameter type.
16231 For the expressions you use in @value{GDBN} commands, you can tell
16232 @value{GDBN} to not enforce strict type checking or
16233 to treat any mismatches as errors and abandon the expression;
16234 When type checking is disabled, @value{GDBN} successfully evaluates
16235 expressions like the second example above.
16237 Even if type checking is off, there may be other reasons
16238 related to type that prevent @value{GDBN} from evaluating an expression.
16239 For instance, @value{GDBN} does not know how to add an @code{int} and
16240 a @code{struct foo}. These particular type errors have nothing to do
16241 with the language in use and usually arise from expressions which make
16242 little sense to evaluate anyway.
16244 @value{GDBN} provides some additional commands for controlling type checking:
16246 @kindex set check type
16247 @kindex show check type
16249 @item set check type on
16250 @itemx set check type off
16251 Set strict type checking on or off. If any type mismatches occur in
16252 evaluating an expression while type checking is on, @value{GDBN} prints a
16253 message and aborts evaluation of the expression.
16255 @item show check type
16256 Show the current setting of type checking and whether @value{GDBN}
16257 is enforcing strict type checking rules.
16260 @cindex range checking
16261 @cindex checks, range
16262 @node Range Checking
16263 @subsection An Overview of Range Checking
16265 In some languages (such as Modula-2), it is an error to exceed the
16266 bounds of a type; this is enforced with run-time checks. Such range
16267 checking is meant to ensure program correctness by making sure
16268 computations do not overflow, or indices on an array element access do
16269 not exceed the bounds of the array.
16271 For expressions you use in @value{GDBN} commands, you can tell
16272 @value{GDBN} to treat range errors in one of three ways: ignore them,
16273 always treat them as errors and abandon the expression, or issue
16274 warnings but evaluate the expression anyway.
16276 A range error can result from numerical overflow, from exceeding an
16277 array index bound, or when you type a constant that is not a member
16278 of any type. Some languages, however, do not treat overflows as an
16279 error. In many implementations of C, mathematical overflow causes the
16280 result to ``wrap around'' to lower values---for example, if @var{m} is
16281 the largest integer value, and @var{s} is the smallest, then
16284 @var{m} + 1 @result{} @var{s}
16287 This, too, is specific to individual languages, and in some cases
16288 specific to individual compilers or machines. @xref{Supported Languages, ,
16289 Supported Languages}, for further details on specific languages.
16291 @value{GDBN} provides some additional commands for controlling the range checker:
16293 @kindex set check range
16294 @kindex show check range
16296 @item set check range auto
16297 Set range checking on or off based on the current working language.
16298 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16301 @item set check range on
16302 @itemx set check range off
16303 Set range checking on or off, overriding the default setting for the
16304 current working language. A warning is issued if the setting does not
16305 match the language default. If a range error occurs and range checking is on,
16306 then a message is printed and evaluation of the expression is aborted.
16308 @item set check range warn
16309 Output messages when the @value{GDBN} range checker detects a range error,
16310 but attempt to evaluate the expression anyway. Evaluating the
16311 expression may still be impossible for other reasons, such as accessing
16312 memory that the process does not own (a typical example from many Unix
16315 @item show check range
16316 Show the current setting of the range checker, and whether or not it is
16317 being set automatically by @value{GDBN}.
16320 @node Supported Languages
16321 @section Supported Languages
16323 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16324 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16325 @c This is false ...
16326 Some @value{GDBN} features may be used in expressions regardless of the
16327 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16328 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16329 ,Expressions}) can be used with the constructs of any supported
16332 The following sections detail to what degree each source language is
16333 supported by @value{GDBN}. These sections are not meant to be language
16334 tutorials or references, but serve only as a reference guide to what the
16335 @value{GDBN} expression parser accepts, and what input and output
16336 formats should look like for different languages. There are many good
16337 books written on each of these languages; please look to these for a
16338 language reference or tutorial.
16341 * C:: C and C@t{++}
16344 * Objective-C:: Objective-C
16345 * OpenCL C:: OpenCL C
16346 * Fortran:: Fortran
16349 * Modula-2:: Modula-2
16354 @subsection C and C@t{++}
16356 @cindex C and C@t{++}
16357 @cindex expressions in C or C@t{++}
16359 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16360 to both languages. Whenever this is the case, we discuss those languages
16364 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16365 @cindex @sc{gnu} C@t{++}
16366 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16367 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16368 effectively, you must compile your C@t{++} programs with a supported
16369 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16370 compiler (@code{aCC}).
16373 * C Operators:: C and C@t{++} operators
16374 * C Constants:: C and C@t{++} constants
16375 * C Plus Plus Expressions:: C@t{++} expressions
16376 * C Defaults:: Default settings for C and C@t{++}
16377 * C Checks:: C and C@t{++} type and range checks
16378 * Debugging C:: @value{GDBN} and C
16379 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16380 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16384 @subsubsection C and C@t{++} Operators
16386 @cindex C and C@t{++} operators
16388 Operators must be defined on values of specific types. For instance,
16389 @code{+} is defined on numbers, but not on structures. Operators are
16390 often defined on groups of types.
16392 For the purposes of C and C@t{++}, the following definitions hold:
16397 @emph{Integral types} include @code{int} with any of its storage-class
16398 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16401 @emph{Floating-point types} include @code{float}, @code{double}, and
16402 @code{long double} (if supported by the target platform).
16405 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16408 @emph{Scalar types} include all of the above.
16413 The following operators are supported. They are listed here
16414 in order of increasing precedence:
16418 The comma or sequencing operator. Expressions in a comma-separated list
16419 are evaluated from left to right, with the result of the entire
16420 expression being the last expression evaluated.
16423 Assignment. The value of an assignment expression is the value
16424 assigned. Defined on scalar types.
16427 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16428 and translated to @w{@code{@var{a} = @var{a op b}}}.
16429 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16430 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16431 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16434 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16435 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16436 should be of an integral type.
16439 Logical @sc{or}. Defined on integral types.
16442 Logical @sc{and}. Defined on integral types.
16445 Bitwise @sc{or}. Defined on integral types.
16448 Bitwise exclusive-@sc{or}. Defined on integral types.
16451 Bitwise @sc{and}. Defined on integral types.
16454 Equality and inequality. Defined on scalar types. The value of these
16455 expressions is 0 for false and non-zero for true.
16457 @item <@r{, }>@r{, }<=@r{, }>=
16458 Less than, greater than, less than or equal, greater than or equal.
16459 Defined on scalar types. The value of these expressions is 0 for false
16460 and non-zero for true.
16463 left shift, and right shift. Defined on integral types.
16466 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16469 Addition and subtraction. Defined on integral types, floating-point types and
16472 @item *@r{, }/@r{, }%
16473 Multiplication, division, and modulus. Multiplication and division are
16474 defined on integral and floating-point types. Modulus is defined on
16478 Increment and decrement. When appearing before a variable, the
16479 operation is performed before the variable is used in an expression;
16480 when appearing after it, the variable's value is used before the
16481 operation takes place.
16484 Pointer dereferencing. Defined on pointer types. Same precedence as
16488 Address operator. Defined on variables. Same precedence as @code{++}.
16490 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16491 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16492 to examine the address
16493 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16497 Negative. Defined on integral and floating-point types. Same
16498 precedence as @code{++}.
16501 Logical negation. Defined on integral types. Same precedence as
16505 Bitwise complement operator. Defined on integral types. Same precedence as
16510 Structure member, and pointer-to-structure member. For convenience,
16511 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16512 pointer based on the stored type information.
16513 Defined on @code{struct} and @code{union} data.
16516 Dereferences of pointers to members.
16519 Array indexing. @code{@var{a}[@var{i}]} is defined as
16520 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16523 Function parameter list. Same precedence as @code{->}.
16526 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16527 and @code{class} types.
16530 Doubled colons also represent the @value{GDBN} scope operator
16531 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16535 If an operator is redefined in the user code, @value{GDBN} usually
16536 attempts to invoke the redefined version instead of using the operator's
16537 predefined meaning.
16540 @subsubsection C and C@t{++} Constants
16542 @cindex C and C@t{++} constants
16544 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16549 Integer constants are a sequence of digits. Octal constants are
16550 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16551 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16552 @samp{l}, specifying that the constant should be treated as a
16556 Floating point constants are a sequence of digits, followed by a decimal
16557 point, followed by a sequence of digits, and optionally followed by an
16558 exponent. An exponent is of the form:
16559 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16560 sequence of digits. The @samp{+} is optional for positive exponents.
16561 A floating-point constant may also end with a letter @samp{f} or
16562 @samp{F}, specifying that the constant should be treated as being of
16563 the @code{float} (as opposed to the default @code{double}) type; or with
16564 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16568 Enumerated constants consist of enumerated identifiers, or their
16569 integral equivalents.
16572 Character constants are a single character surrounded by single quotes
16573 (@code{'}), or a number---the ordinal value of the corresponding character
16574 (usually its @sc{ascii} value). Within quotes, the single character may
16575 be represented by a letter or by @dfn{escape sequences}, which are of
16576 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16577 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16578 @samp{@var{x}} is a predefined special character---for example,
16579 @samp{\n} for newline.
16581 Wide character constants can be written by prefixing a character
16582 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16583 form of @samp{x}. The target wide character set is used when
16584 computing the value of this constant (@pxref{Character Sets}).
16587 String constants are a sequence of character constants surrounded by
16588 double quotes (@code{"}). Any valid character constant (as described
16589 above) may appear. Double quotes within the string must be preceded by
16590 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16593 Wide string constants can be written by prefixing a string constant
16594 with @samp{L}, as in C. The target wide character set is used when
16595 computing the value of this constant (@pxref{Character Sets}).
16598 Pointer constants are an integral value. You can also write pointers
16599 to constants using the C operator @samp{&}.
16602 Array constants are comma-separated lists surrounded by braces @samp{@{}
16603 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16604 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16605 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16608 @node C Plus Plus Expressions
16609 @subsubsection C@t{++} Expressions
16611 @cindex expressions in C@t{++}
16612 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16614 @cindex debugging C@t{++} programs
16615 @cindex C@t{++} compilers
16616 @cindex debug formats and C@t{++}
16617 @cindex @value{NGCC} and C@t{++}
16619 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16620 the proper compiler and the proper debug format. Currently,
16621 @value{GDBN} works best when debugging C@t{++} code that is compiled
16622 with the most recent version of @value{NGCC} possible. The DWARF
16623 debugging format is preferred; @value{NGCC} defaults to this on most
16624 popular platforms. Other compilers and/or debug formats are likely to
16625 work badly or not at all when using @value{GDBN} to debug C@t{++}
16626 code. @xref{Compilation}.
16631 @cindex member functions
16633 Member function calls are allowed; you can use expressions like
16636 count = aml->GetOriginal(x, y)
16639 @vindex this@r{, inside C@t{++} member functions}
16640 @cindex namespace in C@t{++}
16642 While a member function is active (in the selected stack frame), your
16643 expressions have the same namespace available as the member function;
16644 that is, @value{GDBN} allows implicit references to the class instance
16645 pointer @code{this} following the same rules as C@t{++}. @code{using}
16646 declarations in the current scope are also respected by @value{GDBN}.
16648 @cindex call overloaded functions
16649 @cindex overloaded functions, calling
16650 @cindex type conversions in C@t{++}
16652 You can call overloaded functions; @value{GDBN} resolves the function
16653 call to the right definition, with some restrictions. @value{GDBN} does not
16654 perform overload resolution involving user-defined type conversions,
16655 calls to constructors, or instantiations of templates that do not exist
16656 in the program. It also cannot handle ellipsis argument lists or
16659 It does perform integral conversions and promotions, floating-point
16660 promotions, arithmetic conversions, pointer conversions, conversions of
16661 class objects to base classes, and standard conversions such as those of
16662 functions or arrays to pointers; it requires an exact match on the
16663 number of function arguments.
16665 Overload resolution is always performed, unless you have specified
16666 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16667 ,@value{GDBN} Features for C@t{++}}.
16669 You must specify @code{set overload-resolution off} in order to use an
16670 explicit function signature to call an overloaded function, as in
16672 p 'foo(char,int)'('x', 13)
16675 The @value{GDBN} command-completion facility can simplify this;
16676 see @ref{Completion, ,Command Completion}.
16678 @cindex reference declarations
16680 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16681 references; you can use them in expressions just as you do in C@t{++}
16682 source---they are automatically dereferenced.
16684 In the parameter list shown when @value{GDBN} displays a frame, the values of
16685 reference variables are not displayed (unlike other variables); this
16686 avoids clutter, since references are often used for large structures.
16687 The @emph{address} of a reference variable is always shown, unless
16688 you have specified @samp{set print address off}.
16691 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16692 expressions can use it just as expressions in your program do. Since
16693 one scope may be defined in another, you can use @code{::} repeatedly if
16694 necessary, for example in an expression like
16695 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16696 resolving name scope by reference to source files, in both C and C@t{++}
16697 debugging (@pxref{Variables, ,Program Variables}).
16700 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16705 @subsubsection C and C@t{++} Defaults
16707 @cindex C and C@t{++} defaults
16709 If you allow @value{GDBN} to set range checking automatically, it
16710 defaults to @code{off} whenever the working language changes to
16711 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16712 selects the working language.
16714 If you allow @value{GDBN} to set the language automatically, it
16715 recognizes source files whose names end with @file{.c}, @file{.C}, or
16716 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16717 these files, it sets the working language to C or C@t{++}.
16718 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16719 for further details.
16722 @subsubsection C and C@t{++} Type and Range Checks
16724 @cindex C and C@t{++} checks
16726 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16727 checking is used. However, if you turn type checking off, @value{GDBN}
16728 will allow certain non-standard conversions, such as promoting integer
16729 constants to pointers.
16731 Range checking, if turned on, is done on mathematical operations. Array
16732 indices are not checked, since they are often used to index a pointer
16733 that is not itself an array.
16736 @subsubsection @value{GDBN} and C
16738 The @code{set print union} and @code{show print union} commands apply to
16739 the @code{union} type. When set to @samp{on}, any @code{union} that is
16740 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16741 appears as @samp{@{...@}}.
16743 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16744 with pointers and a memory allocation function. @xref{Expressions,
16747 @node Debugging C Plus Plus
16748 @subsubsection @value{GDBN} Features for C@t{++}
16750 @cindex commands for C@t{++}
16752 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16753 designed specifically for use with C@t{++}. Here is a summary:
16756 @cindex break in overloaded functions
16757 @item @r{breakpoint menus}
16758 When you want a breakpoint in a function whose name is overloaded,
16759 @value{GDBN} has the capability to display a menu of possible breakpoint
16760 locations to help you specify which function definition you want.
16761 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16763 @cindex overloading in C@t{++}
16764 @item rbreak @var{regex}
16765 Setting breakpoints using regular expressions is helpful for setting
16766 breakpoints on overloaded functions that are not members of any special
16768 @xref{Set Breaks, ,Setting Breakpoints}.
16770 @cindex C@t{++} exception handling
16772 @itemx catch rethrow
16774 Debug C@t{++} exception handling using these commands. @xref{Set
16775 Catchpoints, , Setting Catchpoints}.
16777 @cindex inheritance
16778 @item ptype @var{typename}
16779 Print inheritance relationships as well as other information for type
16781 @xref{Symbols, ,Examining the Symbol Table}.
16783 @item info vtbl @var{expression}.
16784 The @code{info vtbl} command can be used to display the virtual
16785 method tables of the object computed by @var{expression}. This shows
16786 one entry per virtual table; there may be multiple virtual tables when
16787 multiple inheritance is in use.
16789 @cindex C@t{++} demangling
16790 @item demangle @var{name}
16791 Demangle @var{name}.
16792 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16794 @cindex C@t{++} symbol display
16795 @item set print demangle
16796 @itemx show print demangle
16797 @itemx set print asm-demangle
16798 @itemx show print asm-demangle
16799 Control whether C@t{++} symbols display in their source form, both when
16800 displaying code as C@t{++} source and when displaying disassemblies.
16801 @xref{Print Settings, ,Print Settings}.
16803 @item set print object
16804 @itemx show print object
16805 Choose whether to print derived (actual) or declared types of objects.
16806 @xref{Print Settings, ,Print Settings}.
16808 @item set print vtbl
16809 @itemx show print vtbl
16810 Control the format for printing virtual function tables.
16811 @xref{Print Settings, ,Print Settings}.
16812 (The @code{vtbl} commands do not work on programs compiled with the HP
16813 ANSI C@t{++} compiler (@code{aCC}).)
16815 @kindex set overload-resolution
16816 @cindex overloaded functions, overload resolution
16817 @item set overload-resolution on
16818 Enable overload resolution for C@t{++} expression evaluation. The default
16819 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16820 and searches for a function whose signature matches the argument types,
16821 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16822 Expressions, ,C@t{++} Expressions}, for details).
16823 If it cannot find a match, it emits a message.
16825 @item set overload-resolution off
16826 Disable overload resolution for C@t{++} expression evaluation. For
16827 overloaded functions that are not class member functions, @value{GDBN}
16828 chooses the first function of the specified name that it finds in the
16829 symbol table, whether or not its arguments are of the correct type. For
16830 overloaded functions that are class member functions, @value{GDBN}
16831 searches for a function whose signature @emph{exactly} matches the
16834 @kindex show overload-resolution
16835 @item show overload-resolution
16836 Show the current setting of overload resolution.
16838 @item @r{Overloaded symbol names}
16839 You can specify a particular definition of an overloaded symbol, using
16840 the same notation that is used to declare such symbols in C@t{++}: type
16841 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16842 also use the @value{GDBN} command-line word completion facilities to list the
16843 available choices, or to finish the type list for you.
16844 @xref{Completion,, Command Completion}, for details on how to do this.
16846 @item @r{Breakpoints in functions with ABI tags}
16848 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16849 correspond to changes in the ABI of a type, function, or variable that
16850 would not otherwise be reflected in a mangled name. See
16851 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16854 The ABI tags are visible in C@t{++} demangled names. For example, a
16855 function that returns a std::string:
16858 std::string function(int);
16862 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16863 tag, and @value{GDBN} displays the symbol like this:
16866 function[abi:cxx11](int)
16869 You can set a breakpoint on such functions simply as if they had no
16873 (gdb) b function(int)
16874 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16875 (gdb) info breakpoints
16876 Num Type Disp Enb Address What
16877 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16881 On the rare occasion you need to disambiguate between different ABI
16882 tags, you can do so by simply including the ABI tag in the function
16886 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16890 @node Decimal Floating Point
16891 @subsubsection Decimal Floating Point format
16892 @cindex decimal floating point format
16894 @value{GDBN} can examine, set and perform computations with numbers in
16895 decimal floating point format, which in the C language correspond to the
16896 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16897 specified by the extension to support decimal floating-point arithmetic.
16899 There are two encodings in use, depending on the architecture: BID (Binary
16900 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16901 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16904 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16905 to manipulate decimal floating point numbers, it is not possible to convert
16906 (using a cast, for example) integers wider than 32-bit to decimal float.
16908 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16909 point computations, error checking in decimal float operations ignores
16910 underflow, overflow and divide by zero exceptions.
16912 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16913 to inspect @code{_Decimal128} values stored in floating point registers.
16914 See @ref{PowerPC,,PowerPC} for more details.
16920 @value{GDBN} can be used to debug programs written in D and compiled with
16921 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16922 specific feature --- dynamic arrays.
16927 @cindex Go (programming language)
16928 @value{GDBN} can be used to debug programs written in Go and compiled with
16929 @file{gccgo} or @file{6g} compilers.
16931 Here is a summary of the Go-specific features and restrictions:
16934 @cindex current Go package
16935 @item The current Go package
16936 The name of the current package does not need to be specified when
16937 specifying global variables and functions.
16939 For example, given the program:
16943 var myglob = "Shall we?"
16949 When stopped inside @code{main} either of these work:
16953 (gdb) p main.myglob
16956 @cindex builtin Go types
16957 @item Builtin Go types
16958 The @code{string} type is recognized by @value{GDBN} and is printed
16961 @cindex builtin Go functions
16962 @item Builtin Go functions
16963 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16964 function and handles it internally.
16966 @cindex restrictions on Go expressions
16967 @item Restrictions on Go expressions
16968 All Go operators are supported except @code{&^}.
16969 The Go @code{_} ``blank identifier'' is not supported.
16970 Automatic dereferencing of pointers is not supported.
16974 @subsection Objective-C
16976 @cindex Objective-C
16977 This section provides information about some commands and command
16978 options that are useful for debugging Objective-C code. See also
16979 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16980 few more commands specific to Objective-C support.
16983 * Method Names in Commands::
16984 * The Print Command with Objective-C::
16987 @node Method Names in Commands
16988 @subsubsection Method Names in Commands
16990 The following commands have been extended to accept Objective-C method
16991 names as line specifications:
16993 @kindex clear@r{, and Objective-C}
16994 @kindex break@r{, and Objective-C}
16995 @kindex info line@r{, and Objective-C}
16996 @kindex jump@r{, and Objective-C}
16997 @kindex list@r{, and Objective-C}
17001 @item @code{info line}
17006 A fully qualified Objective-C method name is specified as
17009 -[@var{Class} @var{methodName}]
17012 where the minus sign is used to indicate an instance method and a
17013 plus sign (not shown) is used to indicate a class method. The class
17014 name @var{Class} and method name @var{methodName} are enclosed in
17015 brackets, similar to the way messages are specified in Objective-C
17016 source code. For example, to set a breakpoint at the @code{create}
17017 instance method of class @code{Fruit} in the program currently being
17021 break -[Fruit create]
17024 To list ten program lines around the @code{initialize} class method,
17028 list +[NSText initialize]
17031 In the current version of @value{GDBN}, the plus or minus sign is
17032 required. In future versions of @value{GDBN}, the plus or minus
17033 sign will be optional, but you can use it to narrow the search. It
17034 is also possible to specify just a method name:
17040 You must specify the complete method name, including any colons. If
17041 your program's source files contain more than one @code{create} method,
17042 you'll be presented with a numbered list of classes that implement that
17043 method. Indicate your choice by number, or type @samp{0} to exit if
17046 As another example, to clear a breakpoint established at the
17047 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17050 clear -[NSWindow makeKeyAndOrderFront:]
17053 @node The Print Command with Objective-C
17054 @subsubsection The Print Command With Objective-C
17055 @cindex Objective-C, print objects
17056 @kindex print-object
17057 @kindex po @r{(@code{print-object})}
17059 The print command has also been extended to accept methods. For example:
17062 print -[@var{object} hash]
17065 @cindex print an Objective-C object description
17066 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17068 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17069 and print the result. Also, an additional command has been added,
17070 @code{print-object} or @code{po} for short, which is meant to print
17071 the description of an object. However, this command may only work
17072 with certain Objective-C libraries that have a particular hook
17073 function, @code{_NSPrintForDebugger}, defined.
17076 @subsection OpenCL C
17079 This section provides information about @value{GDBN}s OpenCL C support.
17082 * OpenCL C Datatypes::
17083 * OpenCL C Expressions::
17084 * OpenCL C Operators::
17087 @node OpenCL C Datatypes
17088 @subsubsection OpenCL C Datatypes
17090 @cindex OpenCL C Datatypes
17091 @value{GDBN} supports the builtin scalar and vector datatypes specified
17092 by OpenCL 1.1. In addition the half- and double-precision floating point
17093 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17094 extensions are also known to @value{GDBN}.
17096 @node OpenCL C Expressions
17097 @subsubsection OpenCL C Expressions
17099 @cindex OpenCL C Expressions
17100 @value{GDBN} supports accesses to vector components including the access as
17101 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17102 supported by @value{GDBN} can be used as well.
17104 @node OpenCL C Operators
17105 @subsubsection OpenCL C Operators
17107 @cindex OpenCL C Operators
17108 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17112 @subsection Fortran
17113 @cindex Fortran-specific support in @value{GDBN}
17115 @value{GDBN} can be used to debug programs written in Fortran, but it
17116 currently supports only the features of Fortran 77 language.
17118 @cindex trailing underscore, in Fortran symbols
17119 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17120 among them) append an underscore to the names of variables and
17121 functions. When you debug programs compiled by those compilers, you
17122 will need to refer to variables and functions with a trailing
17126 * Fortran Operators:: Fortran operators and expressions
17127 * Fortran Defaults:: Default settings for Fortran
17128 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17131 @node Fortran Operators
17132 @subsubsection Fortran Operators and Expressions
17134 @cindex Fortran operators and expressions
17136 Operators must be defined on values of specific types. For instance,
17137 @code{+} is defined on numbers, but not on characters or other non-
17138 arithmetic types. Operators are often defined on groups of types.
17142 The exponentiation operator. It raises the first operand to the power
17146 The range operator. Normally used in the form of array(low:high) to
17147 represent a section of array.
17150 The access component operator. Normally used to access elements in derived
17151 types. Also suitable for unions. As unions aren't part of regular Fortran,
17152 this can only happen when accessing a register that uses a gdbarch-defined
17155 The scope operator. Normally used to access variables in modules or
17156 to set breakpoints on subroutines nested in modules or in other
17157 subroutines (internal subroutines).
17160 @node Fortran Defaults
17161 @subsubsection Fortran Defaults
17163 @cindex Fortran Defaults
17165 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17166 default uses case-insensitive matches for Fortran symbols. You can
17167 change that with the @samp{set case-insensitive} command, see
17168 @ref{Symbols}, for the details.
17170 @node Special Fortran Commands
17171 @subsubsection Special Fortran Commands
17173 @cindex Special Fortran commands
17175 @value{GDBN} has some commands to support Fortran-specific features,
17176 such as displaying common blocks.
17179 @cindex @code{COMMON} blocks, Fortran
17180 @kindex info common
17181 @item info common @r{[}@var{common-name}@r{]}
17182 This command prints the values contained in the Fortran @code{COMMON}
17183 block whose name is @var{common-name}. With no argument, the names of
17184 all @code{COMMON} blocks visible at the current program location are
17186 @cindex arrays slices (Fortran)
17187 @kindex set fortran repack-array-slices
17188 @kindex show fortran repack-array-slices
17189 @item set fortran repack-array-slices [on|off]
17190 @item show fortran repack-array-slices
17191 When taking a slice from an array, a Fortran compiler can choose to
17192 either produce an array descriptor that describes the slice in place,
17193 or it may repack the slice, copying the elements of the slice into a
17194 new region of memory.
17196 When this setting is on, then @value{GDBN} will also repack array
17197 slices in some situations. When this setting is off, then
17198 @value{GDBN} will create array descriptors for slices that reference
17199 the original data in place.
17201 @value{GDBN} will never repack an array slice if the data for the
17202 slice is contiguous within the original array.
17204 @value{GDBN} will always repack string slices if the data for the
17205 slice is non-contiguous within the original string as @value{GDBN}
17206 does not support printing non-contiguous strings.
17208 The default for this setting is @code{off}.
17214 @cindex Pascal support in @value{GDBN}, limitations
17215 Debugging Pascal programs which use sets, subranges, file variables, or
17216 nested functions does not currently work. @value{GDBN} does not support
17217 entering expressions, printing values, or similar features using Pascal
17220 The Pascal-specific command @code{set print pascal_static-members}
17221 controls whether static members of Pascal objects are displayed.
17222 @xref{Print Settings, pascal_static-members}.
17227 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17228 Programming Language}. Type- and value-printing, and expression
17229 parsing, are reasonably complete. However, there are a few
17230 peculiarities and holes to be aware of.
17234 Linespecs (@pxref{Specify Location}) are never relative to the current
17235 crate. Instead, they act as if there were a global namespace of
17236 crates, somewhat similar to the way @code{extern crate} behaves.
17238 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17239 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17240 to set a breakpoint in a function named @samp{f} in a crate named
17243 As a consequence of this approach, linespecs also cannot refer to
17244 items using @samp{self::} or @samp{super::}.
17247 Because @value{GDBN} implements Rust name-lookup semantics in
17248 expressions, it will sometimes prepend the current crate to a name.
17249 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17250 @samp{K}, then @code{print ::x::y} will try to find the symbol
17253 However, since it is useful to be able to refer to other crates when
17254 debugging, @value{GDBN} provides the @code{extern} extension to
17255 circumvent this. To use the extension, just put @code{extern} before
17256 a path expression to refer to the otherwise unavailable ``global''
17259 In the above example, if you wanted to refer to the symbol @samp{y} in
17260 the crate @samp{x}, you would use @code{print extern x::y}.
17263 The Rust expression evaluator does not support ``statement-like''
17264 expressions such as @code{if} or @code{match}, or lambda expressions.
17267 Tuple expressions are not implemented.
17270 The Rust expression evaluator does not currently implement the
17271 @code{Drop} trait. Objects that may be created by the evaluator will
17272 never be destroyed.
17275 @value{GDBN} does not implement type inference for generics. In order
17276 to call generic functions or otherwise refer to generic items, you
17277 will have to specify the type parameters manually.
17280 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17281 cases this does not cause any problems. However, in an expression
17282 context, completing a generic function name will give syntactically
17283 invalid results. This happens because Rust requires the @samp{::}
17284 operator between the function name and its generic arguments. For
17285 example, @value{GDBN} might provide a completion like
17286 @code{crate::f<u32>}, where the parser would require
17287 @code{crate::f::<u32>}.
17290 As of this writing, the Rust compiler (version 1.8) has a few holes in
17291 the debugging information it generates. These holes prevent certain
17292 features from being implemented by @value{GDBN}:
17296 Method calls cannot be made via traits.
17299 Operator overloading is not implemented.
17302 When debugging in a monomorphized function, you cannot use the generic
17306 The type @code{Self} is not available.
17309 @code{use} statements are not available, so some names may not be
17310 available in the crate.
17315 @subsection Modula-2
17317 @cindex Modula-2, @value{GDBN} support
17319 The extensions made to @value{GDBN} to support Modula-2 only support
17320 output from the @sc{gnu} Modula-2 compiler (which is currently being
17321 developed). Other Modula-2 compilers are not currently supported, and
17322 attempting to debug executables produced by them is most likely
17323 to give an error as @value{GDBN} reads in the executable's symbol
17326 @cindex expressions in Modula-2
17328 * M2 Operators:: Built-in operators
17329 * Built-In Func/Proc:: Built-in functions and procedures
17330 * M2 Constants:: Modula-2 constants
17331 * M2 Types:: Modula-2 types
17332 * M2 Defaults:: Default settings for Modula-2
17333 * Deviations:: Deviations from standard Modula-2
17334 * M2 Checks:: Modula-2 type and range checks
17335 * M2 Scope:: The scope operators @code{::} and @code{.}
17336 * GDB/M2:: @value{GDBN} and Modula-2
17340 @subsubsection Operators
17341 @cindex Modula-2 operators
17343 Operators must be defined on values of specific types. For instance,
17344 @code{+} is defined on numbers, but not on structures. Operators are
17345 often defined on groups of types. For the purposes of Modula-2, the
17346 following definitions hold:
17351 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17355 @emph{Character types} consist of @code{CHAR} and its subranges.
17358 @emph{Floating-point types} consist of @code{REAL}.
17361 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17365 @emph{Scalar types} consist of all of the above.
17368 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17371 @emph{Boolean types} consist of @code{BOOLEAN}.
17375 The following operators are supported, and appear in order of
17376 increasing precedence:
17380 Function argument or array index separator.
17383 Assignment. The value of @var{var} @code{:=} @var{value} is
17387 Less than, greater than on integral, floating-point, or enumerated
17391 Less than or equal to, greater than or equal to
17392 on integral, floating-point and enumerated types, or set inclusion on
17393 set types. Same precedence as @code{<}.
17395 @item =@r{, }<>@r{, }#
17396 Equality and two ways of expressing inequality, valid on scalar types.
17397 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17398 available for inequality, since @code{#} conflicts with the script
17402 Set membership. Defined on set types and the types of their members.
17403 Same precedence as @code{<}.
17406 Boolean disjunction. Defined on boolean types.
17409 Boolean conjunction. Defined on boolean types.
17412 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17415 Addition and subtraction on integral and floating-point types, or union
17416 and difference on set types.
17419 Multiplication on integral and floating-point types, or set intersection
17423 Division on floating-point types, or symmetric set difference on set
17424 types. Same precedence as @code{*}.
17427 Integer division and remainder. Defined on integral types. Same
17428 precedence as @code{*}.
17431 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17434 Pointer dereferencing. Defined on pointer types.
17437 Boolean negation. Defined on boolean types. Same precedence as
17441 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17442 precedence as @code{^}.
17445 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17448 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17452 @value{GDBN} and Modula-2 scope operators.
17456 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17457 treats the use of the operator @code{IN}, or the use of operators
17458 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17459 @code{<=}, and @code{>=} on sets as an error.
17463 @node Built-In Func/Proc
17464 @subsubsection Built-in Functions and Procedures
17465 @cindex Modula-2 built-ins
17467 Modula-2 also makes available several built-in procedures and functions.
17468 In describing these, the following metavariables are used:
17473 represents an @code{ARRAY} variable.
17476 represents a @code{CHAR} constant or variable.
17479 represents a variable or constant of integral type.
17482 represents an identifier that belongs to a set. Generally used in the
17483 same function with the metavariable @var{s}. The type of @var{s} should
17484 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17487 represents a variable or constant of integral or floating-point type.
17490 represents a variable or constant of floating-point type.
17496 represents a variable.
17499 represents a variable or constant of one of many types. See the
17500 explanation of the function for details.
17503 All Modula-2 built-in procedures also return a result, described below.
17507 Returns the absolute value of @var{n}.
17510 If @var{c} is a lower case letter, it returns its upper case
17511 equivalent, otherwise it returns its argument.
17514 Returns the character whose ordinal value is @var{i}.
17517 Decrements the value in the variable @var{v} by one. Returns the new value.
17519 @item DEC(@var{v},@var{i})
17520 Decrements the value in the variable @var{v} by @var{i}. Returns the
17523 @item EXCL(@var{m},@var{s})
17524 Removes the element @var{m} from the set @var{s}. Returns the new
17527 @item FLOAT(@var{i})
17528 Returns the floating point equivalent of the integer @var{i}.
17530 @item HIGH(@var{a})
17531 Returns the index of the last member of @var{a}.
17534 Increments the value in the variable @var{v} by one. Returns the new value.
17536 @item INC(@var{v},@var{i})
17537 Increments the value in the variable @var{v} by @var{i}. Returns the
17540 @item INCL(@var{m},@var{s})
17541 Adds the element @var{m} to the set @var{s} if it is not already
17542 there. Returns the new set.
17545 Returns the maximum value of the type @var{t}.
17548 Returns the minimum value of the type @var{t}.
17551 Returns boolean TRUE if @var{i} is an odd number.
17554 Returns the ordinal value of its argument. For example, the ordinal
17555 value of a character is its @sc{ascii} value (on machines supporting
17556 the @sc{ascii} character set). The argument @var{x} must be of an
17557 ordered type, which include integral, character and enumerated types.
17559 @item SIZE(@var{x})
17560 Returns the size of its argument. The argument @var{x} can be a
17561 variable or a type.
17563 @item TRUNC(@var{r})
17564 Returns the integral part of @var{r}.
17566 @item TSIZE(@var{x})
17567 Returns the size of its argument. The argument @var{x} can be a
17568 variable or a type.
17570 @item VAL(@var{t},@var{i})
17571 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17575 @emph{Warning:} Sets and their operations are not yet supported, so
17576 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17580 @cindex Modula-2 constants
17582 @subsubsection Constants
17584 @value{GDBN} allows you to express the constants of Modula-2 in the following
17590 Integer constants are simply a sequence of digits. When used in an
17591 expression, a constant is interpreted to be type-compatible with the
17592 rest of the expression. Hexadecimal integers are specified by a
17593 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17596 Floating point constants appear as a sequence of digits, followed by a
17597 decimal point and another sequence of digits. An optional exponent can
17598 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17599 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17600 digits of the floating point constant must be valid decimal (base 10)
17604 Character constants consist of a single character enclosed by a pair of
17605 like quotes, either single (@code{'}) or double (@code{"}). They may
17606 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17607 followed by a @samp{C}.
17610 String constants consist of a sequence of characters enclosed by a
17611 pair of like quotes, either single (@code{'}) or double (@code{"}).
17612 Escape sequences in the style of C are also allowed. @xref{C
17613 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17617 Enumerated constants consist of an enumerated identifier.
17620 Boolean constants consist of the identifiers @code{TRUE} and
17624 Pointer constants consist of integral values only.
17627 Set constants are not yet supported.
17631 @subsubsection Modula-2 Types
17632 @cindex Modula-2 types
17634 Currently @value{GDBN} can print the following data types in Modula-2
17635 syntax: array types, record types, set types, pointer types, procedure
17636 types, enumerated types, subrange types and base types. You can also
17637 print the contents of variables declared using these type.
17638 This section gives a number of simple source code examples together with
17639 sample @value{GDBN} sessions.
17641 The first example contains the following section of code:
17650 and you can request @value{GDBN} to interrogate the type and value of
17651 @code{r} and @code{s}.
17654 (@value{GDBP}) print s
17656 (@value{GDBP}) ptype s
17658 (@value{GDBP}) print r
17660 (@value{GDBP}) ptype r
17665 Likewise if your source code declares @code{s} as:
17669 s: SET ['A'..'Z'] ;
17673 then you may query the type of @code{s} by:
17676 (@value{GDBP}) ptype s
17677 type = SET ['A'..'Z']
17681 Note that at present you cannot interactively manipulate set
17682 expressions using the debugger.
17684 The following example shows how you might declare an array in Modula-2
17685 and how you can interact with @value{GDBN} to print its type and contents:
17689 s: ARRAY [-10..10] OF CHAR ;
17693 (@value{GDBP}) ptype s
17694 ARRAY [-10..10] OF CHAR
17697 Note that the array handling is not yet complete and although the type
17698 is printed correctly, expression handling still assumes that all
17699 arrays have a lower bound of zero and not @code{-10} as in the example
17702 Here are some more type related Modula-2 examples:
17706 colour = (blue, red, yellow, green) ;
17707 t = [blue..yellow] ;
17715 The @value{GDBN} interaction shows how you can query the data type
17716 and value of a variable.
17719 (@value{GDBP}) print s
17721 (@value{GDBP}) ptype t
17722 type = [blue..yellow]
17726 In this example a Modula-2 array is declared and its contents
17727 displayed. Observe that the contents are written in the same way as
17728 their @code{C} counterparts.
17732 s: ARRAY [1..5] OF CARDINAL ;
17738 (@value{GDBP}) print s
17739 $1 = @{1, 0, 0, 0, 0@}
17740 (@value{GDBP}) ptype s
17741 type = ARRAY [1..5] OF CARDINAL
17744 The Modula-2 language interface to @value{GDBN} also understands
17745 pointer types as shown in this example:
17749 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17756 and you can request that @value{GDBN} describes the type of @code{s}.
17759 (@value{GDBP}) ptype s
17760 type = POINTER TO ARRAY [1..5] OF CARDINAL
17763 @value{GDBN} handles compound types as we can see in this example.
17764 Here we combine array types, record types, pointer types and subrange
17775 myarray = ARRAY myrange OF CARDINAL ;
17776 myrange = [-2..2] ;
17778 s: POINTER TO ARRAY myrange OF foo ;
17782 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17786 (@value{GDBP}) ptype s
17787 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17790 f3 : ARRAY [-2..2] OF CARDINAL;
17795 @subsubsection Modula-2 Defaults
17796 @cindex Modula-2 defaults
17798 If type and range checking are set automatically by @value{GDBN}, they
17799 both default to @code{on} whenever the working language changes to
17800 Modula-2. This happens regardless of whether you or @value{GDBN}
17801 selected the working language.
17803 If you allow @value{GDBN} to set the language automatically, then entering
17804 code compiled from a file whose name ends with @file{.mod} sets the
17805 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17806 Infer the Source Language}, for further details.
17809 @subsubsection Deviations from Standard Modula-2
17810 @cindex Modula-2, deviations from
17812 A few changes have been made to make Modula-2 programs easier to debug.
17813 This is done primarily via loosening its type strictness:
17817 Unlike in standard Modula-2, pointer constants can be formed by
17818 integers. This allows you to modify pointer variables during
17819 debugging. (In standard Modula-2, the actual address contained in a
17820 pointer variable is hidden from you; it can only be modified
17821 through direct assignment to another pointer variable or expression that
17822 returned a pointer.)
17825 C escape sequences can be used in strings and characters to represent
17826 non-printable characters. @value{GDBN} prints out strings with these
17827 escape sequences embedded. Single non-printable characters are
17828 printed using the @samp{CHR(@var{nnn})} format.
17831 The assignment operator (@code{:=}) returns the value of its right-hand
17835 All built-in procedures both modify @emph{and} return their argument.
17839 @subsubsection Modula-2 Type and Range Checks
17840 @cindex Modula-2 checks
17843 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17846 @c FIXME remove warning when type/range checks added
17848 @value{GDBN} considers two Modula-2 variables type equivalent if:
17852 They are of types that have been declared equivalent via a @code{TYPE
17853 @var{t1} = @var{t2}} statement
17856 They have been declared on the same line. (Note: This is true of the
17857 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17860 As long as type checking is enabled, any attempt to combine variables
17861 whose types are not equivalent is an error.
17863 Range checking is done on all mathematical operations, assignment, array
17864 index bounds, and all built-in functions and procedures.
17867 @subsubsection The Scope Operators @code{::} and @code{.}
17869 @cindex @code{.}, Modula-2 scope operator
17870 @cindex colon, doubled as scope operator
17872 @vindex colon-colon@r{, in Modula-2}
17873 @c Info cannot handle :: but TeX can.
17876 @vindex ::@r{, in Modula-2}
17879 There are a few subtle differences between the Modula-2 scope operator
17880 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17885 @var{module} . @var{id}
17886 @var{scope} :: @var{id}
17890 where @var{scope} is the name of a module or a procedure,
17891 @var{module} the name of a module, and @var{id} is any declared
17892 identifier within your program, except another module.
17894 Using the @code{::} operator makes @value{GDBN} search the scope
17895 specified by @var{scope} for the identifier @var{id}. If it is not
17896 found in the specified scope, then @value{GDBN} searches all scopes
17897 enclosing the one specified by @var{scope}.
17899 Using the @code{.} operator makes @value{GDBN} search the current scope for
17900 the identifier specified by @var{id} that was imported from the
17901 definition module specified by @var{module}. With this operator, it is
17902 an error if the identifier @var{id} was not imported from definition
17903 module @var{module}, or if @var{id} is not an identifier in
17907 @subsubsection @value{GDBN} and Modula-2
17909 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17910 Five subcommands of @code{set print} and @code{show print} apply
17911 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17912 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17913 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17914 analogue in Modula-2.
17916 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17917 with any language, is not useful with Modula-2. Its
17918 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17919 created in Modula-2 as they can in C or C@t{++}. However, because an
17920 address can be specified by an integral constant, the construct
17921 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17923 @cindex @code{#} in Modula-2
17924 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17925 interpreted as the beginning of a comment. Use @code{<>} instead.
17931 The extensions made to @value{GDBN} for Ada only support
17932 output from the @sc{gnu} Ada (GNAT) compiler.
17933 Other Ada compilers are not currently supported, and
17934 attempting to debug executables produced by them is most likely
17938 @cindex expressions in Ada
17940 * Ada Mode Intro:: General remarks on the Ada syntax
17941 and semantics supported by Ada mode
17943 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17944 * Additions to Ada:: Extensions of the Ada expression syntax.
17945 * Overloading support for Ada:: Support for expressions involving overloaded
17947 * Stopping Before Main Program:: Debugging the program during elaboration.
17948 * Ada Exceptions:: Ada Exceptions
17949 * Ada Tasks:: Listing and setting breakpoints in tasks.
17950 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17951 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17953 * Ada Settings:: New settable GDB parameters for Ada.
17954 * Ada Glitches:: Known peculiarities of Ada mode.
17957 @node Ada Mode Intro
17958 @subsubsection Introduction
17959 @cindex Ada mode, general
17961 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17962 syntax, with some extensions.
17963 The philosophy behind the design of this subset is
17967 That @value{GDBN} should provide basic literals and access to operations for
17968 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17969 leaving more sophisticated computations to subprograms written into the
17970 program (which therefore may be called from @value{GDBN}).
17973 That type safety and strict adherence to Ada language restrictions
17974 are not particularly important to the @value{GDBN} user.
17977 That brevity is important to the @value{GDBN} user.
17980 Thus, for brevity, the debugger acts as if all names declared in
17981 user-written packages are directly visible, even if they are not visible
17982 according to Ada rules, thus making it unnecessary to fully qualify most
17983 names with their packages, regardless of context. Where this causes
17984 ambiguity, @value{GDBN} asks the user's intent.
17986 The debugger will start in Ada mode if it detects an Ada main program.
17987 As for other languages, it will enter Ada mode when stopped in a program that
17988 was translated from an Ada source file.
17990 While in Ada mode, you may use `@t{--}' for comments. This is useful
17991 mostly for documenting command files. The standard @value{GDBN} comment
17992 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17993 middle (to allow based literals).
17995 @node Omissions from Ada
17996 @subsubsection Omissions from Ada
17997 @cindex Ada, omissions from
17999 Here are the notable omissions from the subset:
18003 Only a subset of the attributes are supported:
18007 @t{'First}, @t{'Last}, and @t{'Length}
18008 on array objects (not on types and subtypes).
18011 @t{'Min} and @t{'Max}.
18014 @t{'Pos} and @t{'Val}.
18020 @t{'Range} on array objects (not subtypes), but only as the right
18021 operand of the membership (@code{in}) operator.
18024 @t{'Access}, @t{'Unchecked_Access}, and
18025 @t{'Unrestricted_Access} (a GNAT extension).
18033 @code{Characters.Latin_1} are not available and
18034 concatenation is not implemented. Thus, escape characters in strings are
18035 not currently available.
18038 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18039 equality of representations. They will generally work correctly
18040 for strings and arrays whose elements have integer or enumeration types.
18041 They may not work correctly for arrays whose element
18042 types have user-defined equality, for arrays of real values
18043 (in particular, IEEE-conformant floating point, because of negative
18044 zeroes and NaNs), and for arrays whose elements contain unused bits with
18045 indeterminate values.
18048 The other component-by-component array operations (@code{and}, @code{or},
18049 @code{xor}, @code{not}, and relational tests other than equality)
18050 are not implemented.
18053 @cindex array aggregates (Ada)
18054 @cindex record aggregates (Ada)
18055 @cindex aggregates (Ada)
18056 There is limited support for array and record aggregates. They are
18057 permitted only on the right sides of assignments, as in these examples:
18060 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18061 (@value{GDBP}) set An_Array := (1, others => 0)
18062 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18063 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18064 (@value{GDBP}) set A_Record := (1, "Peter", True);
18065 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18069 discriminant's value by assigning an aggregate has an
18070 undefined effect if that discriminant is used within the record.
18071 However, you can first modify discriminants by directly assigning to
18072 them (which normally would not be allowed in Ada), and then performing an
18073 aggregate assignment. For example, given a variable @code{A_Rec}
18074 declared to have a type such as:
18077 type Rec (Len : Small_Integer := 0) is record
18079 Vals : IntArray (1 .. Len);
18083 you can assign a value with a different size of @code{Vals} with two
18087 (@value{GDBP}) set A_Rec.Len := 4
18088 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18091 As this example also illustrates, @value{GDBN} is very loose about the usual
18092 rules concerning aggregates. You may leave out some of the
18093 components of an array or record aggregate (such as the @code{Len}
18094 component in the assignment to @code{A_Rec} above); they will retain their
18095 original values upon assignment. You may freely use dynamic values as
18096 indices in component associations. You may even use overlapping or
18097 redundant component associations, although which component values are
18098 assigned in such cases is not defined.
18101 Calls to dispatching subprograms are not implemented.
18104 The overloading algorithm is much more limited (i.e., less selective)
18105 than that of real Ada. It makes only limited use of the context in
18106 which a subexpression appears to resolve its meaning, and it is much
18107 looser in its rules for allowing type matches. As a result, some
18108 function calls will be ambiguous, and the user will be asked to choose
18109 the proper resolution.
18112 The @code{new} operator is not implemented.
18115 Entry calls are not implemented.
18118 Aside from printing, arithmetic operations on the native VAX floating-point
18119 formats are not supported.
18122 It is not possible to slice a packed array.
18125 The names @code{True} and @code{False}, when not part of a qualified name,
18126 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18128 Should your program
18129 redefine these names in a package or procedure (at best a dubious practice),
18130 you will have to use fully qualified names to access their new definitions.
18133 @node Additions to Ada
18134 @subsubsection Additions to Ada
18135 @cindex Ada, deviations from
18137 As it does for other languages, @value{GDBN} makes certain generic
18138 extensions to Ada (@pxref{Expressions}):
18142 If the expression @var{E} is a variable residing in memory (typically
18143 a local variable or array element) and @var{N} is a positive integer,
18144 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18145 @var{N}-1 adjacent variables following it in memory as an array. In
18146 Ada, this operator is generally not necessary, since its prime use is
18147 in displaying parts of an array, and slicing will usually do this in
18148 Ada. However, there are occasional uses when debugging programs in
18149 which certain debugging information has been optimized away.
18152 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18153 appears in function or file @var{B}.'' When @var{B} is a file name,
18154 you must typically surround it in single quotes.
18157 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18158 @var{type} that appears at address @var{addr}.''
18161 A name starting with @samp{$} is a convenience variable
18162 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18165 In addition, @value{GDBN} provides a few other shortcuts and outright
18166 additions specific to Ada:
18170 The assignment statement is allowed as an expression, returning
18171 its right-hand operand as its value. Thus, you may enter
18174 (@value{GDBP}) set x := y + 3
18175 (@value{GDBP}) print A(tmp := y + 1)
18179 The semicolon is allowed as an ``operator,'' returning as its value
18180 the value of its right-hand operand.
18181 This allows, for example,
18182 complex conditional breaks:
18185 (@value{GDBP}) break f
18186 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18190 Rather than use catenation and symbolic character names to introduce special
18191 characters into strings, one may instead use a special bracket notation,
18192 which is also used to print strings. A sequence of characters of the form
18193 @samp{["@var{XX}"]} within a string or character literal denotes the
18194 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18195 sequence of characters @samp{["""]} also denotes a single quotation mark
18196 in strings. For example,
18198 "One line.["0a"]Next line.["0a"]"
18201 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18205 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18206 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18210 (@value{GDBP}) print 'max(x, y)
18214 When printing arrays, @value{GDBN} uses positional notation when the
18215 array has a lower bound of 1, and uses a modified named notation otherwise.
18216 For example, a one-dimensional array of three integers with a lower bound
18217 of 3 might print as
18224 That is, in contrast to valid Ada, only the first component has a @code{=>}
18228 You may abbreviate attributes in expressions with any unique,
18229 multi-character subsequence of
18230 their names (an exact match gets preference).
18231 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18232 in place of @t{a'length}.
18235 @cindex quoting Ada internal identifiers
18236 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18237 to lower case. The GNAT compiler uses upper-case characters for
18238 some of its internal identifiers, which are normally of no interest to users.
18239 For the rare occasions when you actually have to look at them,
18240 enclose them in angle brackets to avoid the lower-case mapping.
18243 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18247 Printing an object of class-wide type or dereferencing an
18248 access-to-class-wide value will display all the components of the object's
18249 specific type (as indicated by its run-time tag). Likewise, component
18250 selection on such a value will operate on the specific type of the
18255 @node Overloading support for Ada
18256 @subsubsection Overloading support for Ada
18257 @cindex overloading, Ada
18259 The debugger supports limited overloading. Given a subprogram call in which
18260 the function symbol has multiple definitions, it will use the number of
18261 actual parameters and some information about their types to attempt to narrow
18262 the set of definitions. It also makes very limited use of context, preferring
18263 procedures to functions in the context of the @code{call} command, and
18264 functions to procedures elsewhere.
18266 If, after narrowing, the set of matching definitions still contains more than
18267 one definition, @value{GDBN} will display a menu to query which one it should
18271 (@value{GDBP}) print f(1)
18272 Multiple matches for f
18274 [1] foo.f (integer) return boolean at foo.adb:23
18275 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18279 In this case, just select one menu entry either to cancel expression evaluation
18280 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18281 instance (type the corresponding number and press @key{RET}).
18283 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18288 @kindex set ada print-signatures
18289 @item set ada print-signatures
18290 Control whether parameter types and return types are displayed in overloads
18291 selection menus. It is @code{on} by default.
18292 @xref{Overloading support for Ada}.
18294 @kindex show ada print-signatures
18295 @item show ada print-signatures
18296 Show the current setting for displaying parameter types and return types in
18297 overloads selection menu.
18298 @xref{Overloading support for Ada}.
18302 @node Stopping Before Main Program
18303 @subsubsection Stopping at the Very Beginning
18305 @cindex breakpointing Ada elaboration code
18306 It is sometimes necessary to debug the program during elaboration, and
18307 before reaching the main procedure.
18308 As defined in the Ada Reference
18309 Manual, the elaboration code is invoked from a procedure called
18310 @code{adainit}. To run your program up to the beginning of
18311 elaboration, simply use the following two commands:
18312 @code{tbreak adainit} and @code{run}.
18314 @node Ada Exceptions
18315 @subsubsection Ada Exceptions
18317 A command is provided to list all Ada exceptions:
18320 @kindex info exceptions
18321 @item info exceptions
18322 @itemx info exceptions @var{regexp}
18323 The @code{info exceptions} command allows you to list all Ada exceptions
18324 defined within the program being debugged, as well as their addresses.
18325 With a regular expression, @var{regexp}, as argument, only those exceptions
18326 whose names match @var{regexp} are listed.
18329 Below is a small example, showing how the command can be used, first
18330 without argument, and next with a regular expression passed as an
18334 (@value{GDBP}) info exceptions
18335 All defined Ada exceptions:
18336 constraint_error: 0x613da0
18337 program_error: 0x613d20
18338 storage_error: 0x613ce0
18339 tasking_error: 0x613ca0
18340 const.aint_global_e: 0x613b00
18341 (@value{GDBP}) info exceptions const.aint
18342 All Ada exceptions matching regular expression "const.aint":
18343 constraint_error: 0x613da0
18344 const.aint_global_e: 0x613b00
18347 It is also possible to ask @value{GDBN} to stop your program's execution
18348 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18351 @subsubsection Extensions for Ada Tasks
18352 @cindex Ada, tasking
18354 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18355 @value{GDBN} provides the following task-related commands:
18360 This command shows a list of current Ada tasks, as in the following example:
18367 (@value{GDBP}) info tasks
18368 ID TID P-ID Pri State Name
18369 1 8088000 0 15 Child Activation Wait main_task
18370 2 80a4000 1 15 Accept Statement b
18371 3 809a800 1 15 Child Activation Wait a
18372 * 4 80ae800 3 15 Runnable c
18377 In this listing, the asterisk before the last task indicates it to be the
18378 task currently being inspected.
18382 Represents @value{GDBN}'s internal task number.
18388 The parent's task ID (@value{GDBN}'s internal task number).
18391 The base priority of the task.
18394 Current state of the task.
18398 The task has been created but has not been activated. It cannot be
18402 The task is not blocked for any reason known to Ada. (It may be waiting
18403 for a mutex, though.) It is conceptually "executing" in normal mode.
18406 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18407 that were waiting on terminate alternatives have been awakened and have
18408 terminated themselves.
18410 @item Child Activation Wait
18411 The task is waiting for created tasks to complete activation.
18413 @item Accept Statement
18414 The task is waiting on an accept or selective wait statement.
18416 @item Waiting on entry call
18417 The task is waiting on an entry call.
18419 @item Async Select Wait
18420 The task is waiting to start the abortable part of an asynchronous
18424 The task is waiting on a select statement with only a delay
18427 @item Child Termination Wait
18428 The task is sleeping having completed a master within itself, and is
18429 waiting for the tasks dependent on that master to become terminated or
18430 waiting on a terminate Phase.
18432 @item Wait Child in Term Alt
18433 The task is sleeping waiting for tasks on terminate alternatives to
18434 finish terminating.
18436 @item Accepting RV with @var{taskno}
18437 The task is accepting a rendez-vous with the task @var{taskno}.
18441 Name of the task in the program.
18445 @kindex info task @var{taskno}
18446 @item info task @var{taskno}
18447 This command shows detailed informations on the specified task, as in
18448 the following example:
18453 (@value{GDBP}) info tasks
18454 ID TID P-ID Pri State Name
18455 1 8077880 0 15 Child Activation Wait main_task
18456 * 2 807c468 1 15 Runnable task_1
18457 (@value{GDBP}) info task 2
18458 Ada Task: 0x807c468
18462 Parent: 1 ("main_task")
18468 @kindex task@r{ (Ada)}
18469 @cindex current Ada task ID
18470 This command prints the ID and name of the current task.
18476 (@value{GDBP}) info tasks
18477 ID TID P-ID Pri State Name
18478 1 8077870 0 15 Child Activation Wait main_task
18479 * 2 807c458 1 15 Runnable some_task
18480 (@value{GDBP}) task
18481 [Current task is 2 "some_task"]
18484 @item task @var{taskno}
18485 @cindex Ada task switching
18486 This command is like the @code{thread @var{thread-id}}
18487 command (@pxref{Threads}). It switches the context of debugging
18488 from the current task to the given task.
18494 (@value{GDBP}) info tasks
18495 ID TID P-ID Pri State Name
18496 1 8077870 0 15 Child Activation Wait main_task
18497 * 2 807c458 1 15 Runnable some_task
18498 (@value{GDBP}) task 1
18499 [Switching to task 1 "main_task"]
18500 #0 0x8067726 in pthread_cond_wait ()
18502 #0 0x8067726 in pthread_cond_wait ()
18503 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18504 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18505 #3 0x806153e in system.tasking.stages.activate_tasks ()
18506 #4 0x804aacc in un () at un.adb:5
18509 @item break @var{location} task @var{taskno}
18510 @itemx break @var{location} task @var{taskno} if @dots{}
18511 @cindex breakpoints and tasks, in Ada
18512 @cindex task breakpoints, in Ada
18513 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18514 These commands are like the @code{break @dots{} thread @dots{}}
18515 command (@pxref{Thread Stops}). The
18516 @var{location} argument specifies source lines, as described
18517 in @ref{Specify Location}.
18519 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18520 to specify that you only want @value{GDBN} to stop the program when a
18521 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18522 numeric task identifiers assigned by @value{GDBN}, shown in the first
18523 column of the @samp{info tasks} display.
18525 If you do not specify @samp{task @var{taskno}} when you set a
18526 breakpoint, the breakpoint applies to @emph{all} tasks of your
18529 You can use the @code{task} qualifier on conditional breakpoints as
18530 well; in this case, place @samp{task @var{taskno}} before the
18531 breakpoint condition (before the @code{if}).
18539 (@value{GDBP}) info tasks
18540 ID TID P-ID Pri State Name
18541 1 140022020 0 15 Child Activation Wait main_task
18542 2 140045060 1 15 Accept/Select Wait t2
18543 3 140044840 1 15 Runnable t1
18544 * 4 140056040 1 15 Runnable t3
18545 (@value{GDBP}) b 15 task 2
18546 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18547 (@value{GDBP}) cont
18552 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18554 (@value{GDBP}) info tasks
18555 ID TID P-ID Pri State Name
18556 1 140022020 0 15 Child Activation Wait main_task
18557 * 2 140045060 1 15 Runnable t2
18558 3 140044840 1 15 Runnable t1
18559 4 140056040 1 15 Delay Sleep t3
18563 @node Ada Tasks and Core Files
18564 @subsubsection Tasking Support when Debugging Core Files
18565 @cindex Ada tasking and core file debugging
18567 When inspecting a core file, as opposed to debugging a live program,
18568 tasking support may be limited or even unavailable, depending on
18569 the platform being used.
18570 For instance, on x86-linux, the list of tasks is available, but task
18571 switching is not supported.
18573 On certain platforms, the debugger needs to perform some
18574 memory writes in order to provide Ada tasking support. When inspecting
18575 a core file, this means that the core file must be opened with read-write
18576 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18577 Under these circumstances, you should make a backup copy of the core
18578 file before inspecting it with @value{GDBN}.
18580 @node Ravenscar Profile
18581 @subsubsection Tasking Support when using the Ravenscar Profile
18582 @cindex Ravenscar Profile
18584 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18585 specifically designed for systems with safety-critical real-time
18589 @kindex set ravenscar task-switching on
18590 @cindex task switching with program using Ravenscar Profile
18591 @item set ravenscar task-switching on
18592 Allows task switching when debugging a program that uses the Ravenscar
18593 Profile. This is the default.
18595 @kindex set ravenscar task-switching off
18596 @item set ravenscar task-switching off
18597 Turn off task switching when debugging a program that uses the Ravenscar
18598 Profile. This is mostly intended to disable the code that adds support
18599 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18600 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18601 To be effective, this command should be run before the program is started.
18603 @kindex show ravenscar task-switching
18604 @item show ravenscar task-switching
18605 Show whether it is possible to switch from task to task in a program
18606 using the Ravenscar Profile.
18610 @cindex Ravenscar thread
18611 When Ravenscar task-switching is enabled, Ravenscar tasks are
18612 announced by @value{GDBN} as if they were threads:
18616 [New Ravenscar Thread 0x2b8f0]
18619 Both Ravenscar tasks and the underlying CPU threads will show up in
18620 the output of @code{info threads}:
18625 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18626 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18627 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18628 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18629 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18630 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18633 One known limitation of the Ravenscar support in @value{GDBN} is that
18634 it isn't currently possible to single-step through the runtime
18635 initialization sequence. If you need to debug this code, you should
18636 use @code{set ravenscar task-switching off}.
18639 @subsubsection Ada Settings
18640 @cindex Ada settings
18643 @kindex set varsize-limit
18644 @item set varsize-limit @var{size}
18645 Prevent @value{GDBN} from attempting to evaluate objects whose size
18646 is above the given limit (@var{size}) when those sizes are computed
18647 from run-time quantities. This is typically the case when the object
18648 has a variable size, such as an array whose bounds are not known at
18649 compile time for example. Setting @var{size} to @code{unlimited}
18650 removes the size limitation. By default, the limit is about 65KB.
18652 The purpose of having such a limit is to prevent @value{GDBN} from
18653 trying to grab enormous chunks of virtual memory when asked to evaluate
18654 a quantity whose bounds have been corrupted or have not yet been fully
18655 initialized. The limit applies to the results of some subexpressions
18656 as well as to complete expressions. For example, an expression denoting
18657 a simple integer component, such as @code{x.y.z}, may fail if the size of
18658 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18659 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18660 @code{A} is an array variable with non-constant size, will generally
18661 succeed regardless of the bounds on @code{A}, as long as the component
18662 size is less than @var{size}.
18664 @kindex show varsize-limit
18665 @item show varsize-limit
18666 Show the limit on types whose size is determined by run-time quantities.
18670 @subsubsection Known Peculiarities of Ada Mode
18671 @cindex Ada, problems
18673 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18674 we know of several problems with and limitations of Ada mode in
18676 some of which will be fixed with planned future releases of the debugger
18677 and the GNU Ada compiler.
18681 Static constants that the compiler chooses not to materialize as objects in
18682 storage are invisible to the debugger.
18685 Named parameter associations in function argument lists are ignored (the
18686 argument lists are treated as positional).
18689 Many useful library packages are currently invisible to the debugger.
18692 Fixed-point arithmetic, conversions, input, and output is carried out using
18693 floating-point arithmetic, and may give results that only approximate those on
18697 The GNAT compiler never generates the prefix @code{Standard} for any of
18698 the standard symbols defined by the Ada language. @value{GDBN} knows about
18699 this: it will strip the prefix from names when you use it, and will never
18700 look for a name you have so qualified among local symbols, nor match against
18701 symbols in other packages or subprograms. If you have
18702 defined entities anywhere in your program other than parameters and
18703 local variables whose simple names match names in @code{Standard},
18704 GNAT's lack of qualification here can cause confusion. When this happens,
18705 you can usually resolve the confusion
18706 by qualifying the problematic names with package
18707 @code{Standard} explicitly.
18710 Older versions of the compiler sometimes generate erroneous debugging
18711 information, resulting in the debugger incorrectly printing the value
18712 of affected entities. In some cases, the debugger is able to work
18713 around an issue automatically. In other cases, the debugger is able
18714 to work around the issue, but the work-around has to be specifically
18717 @kindex set ada trust-PAD-over-XVS
18718 @kindex show ada trust-PAD-over-XVS
18721 @item set ada trust-PAD-over-XVS on
18722 Configure GDB to strictly follow the GNAT encoding when computing the
18723 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18724 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18725 a complete description of the encoding used by the GNAT compiler).
18726 This is the default.
18728 @item set ada trust-PAD-over-XVS off
18729 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18730 sometimes prints the wrong value for certain entities, changing @code{ada
18731 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18732 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18733 @code{off}, but this incurs a slight performance penalty, so it is
18734 recommended to leave this setting to @code{on} unless necessary.
18738 @cindex GNAT descriptive types
18739 @cindex GNAT encoding
18740 Internally, the debugger also relies on the compiler following a number
18741 of conventions known as the @samp{GNAT Encoding}, all documented in
18742 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18743 how the debugging information should be generated for certain types.
18744 In particular, this convention makes use of @dfn{descriptive types},
18745 which are artificial types generated purely to help the debugger.
18747 These encodings were defined at a time when the debugging information
18748 format used was not powerful enough to describe some of the more complex
18749 types available in Ada. Since DWARF allows us to express nearly all
18750 Ada features, the long-term goal is to slowly replace these descriptive
18751 types by their pure DWARF equivalent. To facilitate that transition,
18752 a new maintenance option is available to force the debugger to ignore
18753 those descriptive types. It allows the user to quickly evaluate how
18754 well @value{GDBN} works without them.
18758 @kindex maint ada set ignore-descriptive-types
18759 @item maintenance ada set ignore-descriptive-types [on|off]
18760 Control whether the debugger should ignore descriptive types.
18761 The default is not to ignore descriptives types (@code{off}).
18763 @kindex maint ada show ignore-descriptive-types
18764 @item maintenance ada show ignore-descriptive-types
18765 Show if descriptive types are ignored by @value{GDBN}.
18769 @node Unsupported Languages
18770 @section Unsupported Languages
18772 @cindex unsupported languages
18773 @cindex minimal language
18774 In addition to the other fully-supported programming languages,
18775 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18776 It does not represent a real programming language, but provides a set
18777 of capabilities close to what the C or assembly languages provide.
18778 This should allow most simple operations to be performed while debugging
18779 an application that uses a language currently not supported by @value{GDBN}.
18781 If the language is set to @code{auto}, @value{GDBN} will automatically
18782 select this language if the current frame corresponds to an unsupported
18786 @chapter Examining the Symbol Table
18788 The commands described in this chapter allow you to inquire about the
18789 symbols (names of variables, functions and types) defined in your
18790 program. This information is inherent in the text of your program and
18791 does not change as your program executes. @value{GDBN} finds it in your
18792 program's symbol table, in the file indicated when you started @value{GDBN}
18793 (@pxref{File Options, ,Choosing Files}), or by one of the
18794 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18796 @cindex symbol names
18797 @cindex names of symbols
18798 @cindex quoting names
18799 @anchor{quoting names}
18800 Occasionally, you may need to refer to symbols that contain unusual
18801 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18802 most frequent case is in referring to static variables in other
18803 source files (@pxref{Variables,,Program Variables}). File names
18804 are recorded in object files as debugging symbols, but @value{GDBN} would
18805 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18806 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18807 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18814 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18817 @cindex case-insensitive symbol names
18818 @cindex case sensitivity in symbol names
18819 @kindex set case-sensitive
18820 @item set case-sensitive on
18821 @itemx set case-sensitive off
18822 @itemx set case-sensitive auto
18823 Normally, when @value{GDBN} looks up symbols, it matches their names
18824 with case sensitivity determined by the current source language.
18825 Occasionally, you may wish to control that. The command @code{set
18826 case-sensitive} lets you do that by specifying @code{on} for
18827 case-sensitive matches or @code{off} for case-insensitive ones. If
18828 you specify @code{auto}, case sensitivity is reset to the default
18829 suitable for the source language. The default is case-sensitive
18830 matches for all languages except for Fortran, for which the default is
18831 case-insensitive matches.
18833 @kindex show case-sensitive
18834 @item show case-sensitive
18835 This command shows the current setting of case sensitivity for symbols
18838 @kindex set print type methods
18839 @item set print type methods
18840 @itemx set print type methods on
18841 @itemx set print type methods off
18842 Normally, when @value{GDBN} prints a class, it displays any methods
18843 declared in that class. You can control this behavior either by
18844 passing the appropriate flag to @code{ptype}, or using @command{set
18845 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18846 display the methods; this is the default. Specifying @code{off} will
18847 cause @value{GDBN} to omit the methods.
18849 @kindex show print type methods
18850 @item show print type methods
18851 This command shows the current setting of method display when printing
18854 @kindex set print type nested-type-limit
18855 @item set print type nested-type-limit @var{limit}
18856 @itemx set print type nested-type-limit unlimited
18857 Set the limit of displayed nested types that the type printer will
18858 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18859 nested definitions. By default, the type printer will not show any nested
18860 types defined in classes.
18862 @kindex show print type nested-type-limit
18863 @item show print type nested-type-limit
18864 This command shows the current display limit of nested types when
18867 @kindex set print type typedefs
18868 @item set print type typedefs
18869 @itemx set print type typedefs on
18870 @itemx set print type typedefs off
18872 Normally, when @value{GDBN} prints a class, it displays any typedefs
18873 defined in that class. You can control this behavior either by
18874 passing the appropriate flag to @code{ptype}, or using @command{set
18875 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18876 display the typedef definitions; this is the default. Specifying
18877 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18878 Note that this controls whether the typedef definition itself is
18879 printed, not whether typedef names are substituted when printing other
18882 @kindex show print type typedefs
18883 @item show print type typedefs
18884 This command shows the current setting of typedef display when
18887 @kindex set print type hex
18888 @item set print type hex
18889 @itemx set print type hex on
18890 @itemx set print type hex off
18892 When @value{GDBN} prints sizes and offsets of struct members, it can use
18893 either the decimal or hexadecimal notation. You can select one or the
18894 other either by passing the appropriate flag to @code{ptype}, or by using
18895 the @command{set print type hex} command.
18897 @kindex show print type hex
18898 @item show print type hex
18899 This command shows whether the sizes and offsets of struct members are
18900 printed in decimal or hexadecimal notation.
18902 @kindex info address
18903 @cindex address of a symbol
18904 @item info address @var{symbol}
18905 Describe where the data for @var{symbol} is stored. For a register
18906 variable, this says which register it is kept in. For a non-register
18907 local variable, this prints the stack-frame offset at which the variable
18910 Note the contrast with @samp{print &@var{symbol}}, which does not work
18911 at all for a register variable, and for a stack local variable prints
18912 the exact address of the current instantiation of the variable.
18914 @kindex info symbol
18915 @cindex symbol from address
18916 @cindex closest symbol and offset for an address
18917 @item info symbol @var{addr}
18918 Print the name of a symbol which is stored at the address @var{addr}.
18919 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18920 nearest symbol and an offset from it:
18923 (@value{GDBP}) info symbol 0x54320
18924 _initialize_vx + 396 in section .text
18928 This is the opposite of the @code{info address} command. You can use
18929 it to find out the name of a variable or a function given its address.
18931 For dynamically linked executables, the name of executable or shared
18932 library containing the symbol is also printed:
18935 (@value{GDBP}) info symbol 0x400225
18936 _start + 5 in section .text of /tmp/a.out
18937 (@value{GDBP}) info symbol 0x2aaaac2811cf
18938 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18943 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18944 Demangle @var{name}.
18945 If @var{language} is provided it is the name of the language to demangle
18946 @var{name} in. Otherwise @var{name} is demangled in the current language.
18948 The @samp{--} option specifies the end of options,
18949 and is useful when @var{name} begins with a dash.
18951 The parameter @code{demangle-style} specifies how to interpret the kind
18952 of mangling used. @xref{Print Settings}.
18955 @item whatis[/@var{flags}] [@var{arg}]
18956 Print the data type of @var{arg}, which can be either an expression
18957 or a name of a data type. With no argument, print the data type of
18958 @code{$}, the last value in the value history.
18960 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18961 is not actually evaluated, and any side-effecting operations (such as
18962 assignments or function calls) inside it do not take place.
18964 If @var{arg} is a variable or an expression, @code{whatis} prints its
18965 literal type as it is used in the source code. If the type was
18966 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18967 the data type underlying the @code{typedef}. If the type of the
18968 variable or the expression is a compound data type, such as
18969 @code{struct} or @code{class}, @code{whatis} never prints their
18970 fields or methods. It just prints the @code{struct}/@code{class}
18971 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18972 such a compound data type, use @code{ptype}.
18974 If @var{arg} is a type name that was defined using @code{typedef},
18975 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18976 Unrolling means that @code{whatis} will show the underlying type used
18977 in the @code{typedef} declaration of @var{arg}. However, if that
18978 underlying type is also a @code{typedef}, @code{whatis} will not
18981 For C code, the type names may also have the form @samp{class
18982 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18983 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18985 @var{flags} can be used to modify how the type is displayed.
18986 Available flags are:
18990 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18991 parameters and typedefs defined in a class when printing the class'
18992 members. The @code{/r} flag disables this.
18995 Do not print methods defined in the class.
18998 Print methods defined in the class. This is the default, but the flag
18999 exists in case you change the default with @command{set print type methods}.
19002 Do not print typedefs defined in the class. Note that this controls
19003 whether the typedef definition itself is printed, not whether typedef
19004 names are substituted when printing other types.
19007 Print typedefs defined in the class. This is the default, but the flag
19008 exists in case you change the default with @command{set print type typedefs}.
19011 Print the offsets and sizes of fields in a struct, similar to what the
19012 @command{pahole} tool does. This option implies the @code{/tm} flags.
19015 Use hexadecimal notation when printing offsets and sizes of fields in a
19019 Use decimal notation when printing offsets and sizes of fields in a
19022 For example, given the following declarations:
19058 Issuing a @kbd{ptype /o struct tuv} command would print:
19061 (@value{GDBP}) ptype /o struct tuv
19062 /* offset | size */ type = struct tuv @{
19063 /* 0 | 4 */ int a1;
19064 /* XXX 4-byte hole */
19065 /* 8 | 8 */ char *a2;
19066 /* 16 | 4 */ int a3;
19068 /* total size (bytes): 24 */
19072 Notice the format of the first column of comments. There, you can
19073 find two parts separated by the @samp{|} character: the @emph{offset},
19074 which indicates where the field is located inside the struct, in
19075 bytes, and the @emph{size} of the field. Another interesting line is
19076 the marker of a @emph{hole} in the struct, indicating that it may be
19077 possible to pack the struct and make it use less space by reorganizing
19080 It is also possible to print offsets inside an union:
19083 (@value{GDBP}) ptype /o union qwe
19084 /* offset | size */ type = union qwe @{
19085 /* 24 */ struct tuv @{
19086 /* 0 | 4 */ int a1;
19087 /* XXX 4-byte hole */
19088 /* 8 | 8 */ char *a2;
19089 /* 16 | 4 */ int a3;
19091 /* total size (bytes): 24 */
19093 /* 40 */ struct xyz @{
19094 /* 0 | 4 */ int f1;
19095 /* 4 | 1 */ char f2;
19096 /* XXX 3-byte hole */
19097 /* 8 | 8 */ void *f3;
19098 /* 16 | 24 */ struct tuv @{
19099 /* 16 | 4 */ int a1;
19100 /* XXX 4-byte hole */
19101 /* 24 | 8 */ char *a2;
19102 /* 32 | 4 */ int a3;
19104 /* total size (bytes): 24 */
19107 /* total size (bytes): 40 */
19110 /* total size (bytes): 40 */
19114 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19115 same space (because we are dealing with an union), the offset is not
19116 printed for them. However, you can still examine the offset of each
19117 of these structures' fields.
19119 Another useful scenario is printing the offsets of a struct containing
19123 (@value{GDBP}) ptype /o struct tyu
19124 /* offset | size */ type = struct tyu @{
19125 /* 0:31 | 4 */ int a1 : 1;
19126 /* 0:28 | 4 */ int a2 : 3;
19127 /* 0: 5 | 4 */ int a3 : 23;
19128 /* 3: 3 | 1 */ signed char a4 : 2;
19129 /* XXX 3-bit hole */
19130 /* XXX 4-byte hole */
19131 /* 8 | 8 */ int64_t a5;
19132 /* 16: 0 | 4 */ int a6 : 5;
19133 /* 16: 5 | 8 */ int64_t a7 : 3;
19134 /* XXX 7-byte padding */
19136 /* total size (bytes): 24 */
19140 Note how the offset information is now extended to also include the
19141 first bit of the bitfield.
19145 @item ptype[/@var{flags}] [@var{arg}]
19146 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19147 detailed description of the type, instead of just the name of the type.
19148 @xref{Expressions, ,Expressions}.
19150 Contrary to @code{whatis}, @code{ptype} always unrolls any
19151 @code{typedef}s in its argument declaration, whether the argument is
19152 a variable, expression, or a data type. This means that @code{ptype}
19153 of a variable or an expression will not print literally its type as
19154 present in the source code---use @code{whatis} for that. @code{typedef}s at
19155 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19156 fields, methods and inner @code{class typedef}s of @code{struct}s,
19157 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19159 For example, for this variable declaration:
19162 typedef double real_t;
19163 struct complex @{ real_t real; double imag; @};
19164 typedef struct complex complex_t;
19166 real_t *real_pointer_var;
19170 the two commands give this output:
19174 (@value{GDBP}) whatis var
19176 (@value{GDBP}) ptype var
19177 type = struct complex @{
19181 (@value{GDBP}) whatis complex_t
19182 type = struct complex
19183 (@value{GDBP}) whatis struct complex
19184 type = struct complex
19185 (@value{GDBP}) ptype struct complex
19186 type = struct complex @{
19190 (@value{GDBP}) whatis real_pointer_var
19192 (@value{GDBP}) ptype real_pointer_var
19198 As with @code{whatis}, using @code{ptype} without an argument refers to
19199 the type of @code{$}, the last value in the value history.
19201 @cindex incomplete type
19202 Sometimes, programs use opaque data types or incomplete specifications
19203 of complex data structure. If the debug information included in the
19204 program does not allow @value{GDBN} to display a full declaration of
19205 the data type, it will say @samp{<incomplete type>}. For example,
19206 given these declarations:
19210 struct foo *fooptr;
19214 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19217 (@value{GDBP}) ptype foo
19218 $1 = <incomplete type>
19222 ``Incomplete type'' is C terminology for data types that are not
19223 completely specified.
19225 @cindex unknown type
19226 Othertimes, information about a variable's type is completely absent
19227 from the debug information included in the program. This most often
19228 happens when the program or library where the variable is defined
19229 includes no debug information at all. @value{GDBN} knows the variable
19230 exists from inspecting the linker/loader symbol table (e.g., the ELF
19231 dynamic symbol table), but such symbols do not contain type
19232 information. Inspecting the type of a (global) variable for which
19233 @value{GDBN} has no type information shows:
19236 (@value{GDBP}) ptype var
19237 type = <data variable, no debug info>
19240 @xref{Variables, no debug info variables}, for how to print the values
19244 @item info types [-q] [@var{regexp}]
19245 Print a brief description of all types whose names match the regular
19246 expression @var{regexp} (or all types in your program, if you supply
19247 no argument). Each complete typename is matched as though it were a
19248 complete line; thus, @samp{i type value} gives information on all
19249 types in your program whose names include the string @code{value}, but
19250 @samp{i type ^value$} gives information only on types whose complete
19251 name is @code{value}.
19253 In programs using different languages, @value{GDBN} chooses the syntax
19254 to print the type description according to the
19255 @samp{set language} value: using @samp{set language auto}
19256 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19257 language of the type, other values mean to use
19258 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19260 This command differs from @code{ptype} in two ways: first, like
19261 @code{whatis}, it does not print a detailed description; second, it
19262 lists all source files and line numbers where a type is defined.
19264 The output from @samp{into types} is proceeded with a header line
19265 describing what types are being listed. The optional flag @samp{-q},
19266 which stands for @samp{quiet}, disables printing this header
19269 @kindex info type-printers
19270 @item info type-printers
19271 Versions of @value{GDBN} that ship with Python scripting enabled may
19272 have ``type printers'' available. When using @command{ptype} or
19273 @command{whatis}, these printers are consulted when the name of a type
19274 is needed. @xref{Type Printing API}, for more information on writing
19277 @code{info type-printers} displays all the available type printers.
19279 @kindex enable type-printer
19280 @kindex disable type-printer
19281 @item enable type-printer @var{name}@dots{}
19282 @item disable type-printer @var{name}@dots{}
19283 These commands can be used to enable or disable type printers.
19286 @cindex local variables
19287 @item info scope @var{location}
19288 List all the variables local to a particular scope. This command
19289 accepts a @var{location} argument---a function name, a source line, or
19290 an address preceded by a @samp{*}, and prints all the variables local
19291 to the scope defined by that location. (@xref{Specify Location}, for
19292 details about supported forms of @var{location}.) For example:
19295 (@value{GDBP}) @b{info scope command_line_handler}
19296 Scope for command_line_handler:
19297 Symbol rl is an argument at stack/frame offset 8, length 4.
19298 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19299 Symbol linelength is in static storage at address 0x150a1c, length 4.
19300 Symbol p is a local variable in register $esi, length 4.
19301 Symbol p1 is a local variable in register $ebx, length 4.
19302 Symbol nline is a local variable in register $edx, length 4.
19303 Symbol repeat is a local variable at frame offset -8, length 4.
19307 This command is especially useful for determining what data to collect
19308 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19311 @kindex info source
19313 Show information about the current source file---that is, the source file for
19314 the function containing the current point of execution:
19317 the name of the source file, and the directory containing it,
19319 the directory it was compiled in,
19321 its length, in lines,
19323 which programming language it is written in,
19325 if the debug information provides it, the program that compiled the file
19326 (which may include, e.g., the compiler version and command line arguments),
19328 whether the executable includes debugging information for that file, and
19329 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19331 whether the debugging information includes information about
19332 preprocessor macros.
19336 @kindex info sources
19338 Print the names of all source files in your program for which there is
19339 debugging information, organized into two lists: files whose symbols
19340 have already been read, and files whose symbols will be read when needed.
19342 @item info sources [-dirname | -basename] [--] [@var{regexp}]
19343 Like @samp{info sources}, but only print the names of the files
19344 matching the provided @var{regexp}.
19345 By default, the @var{regexp} is used to match anywhere in the filename.
19346 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
19347 If @code{-basename}, only files having a basename matching @var{regexp}
19349 The matching is case-sensitive, except on operating systems that
19350 have case-insensitive filesystem (e.g., MS-Windows).
19352 @kindex info functions
19353 @item info functions [-q] [-n]
19354 Print the names and data types of all defined functions.
19355 Similarly to @samp{info types}, this command groups its output by source
19356 files and annotates each function definition with its source line
19359 In programs using different languages, @value{GDBN} chooses the syntax
19360 to print the function name and type according to the
19361 @samp{set language} value: using @samp{set language auto}
19362 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19363 language of the function, other values mean to use
19364 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19366 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19367 results. A non-debugging symbol is a symbol that comes from the
19368 executable's symbol table, not from the debug information (for
19369 example, DWARF) associated with the executable.
19371 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19372 printing header information and messages explaining why no functions
19375 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19376 Like @samp{info functions}, but only print the names and data types
19377 of the functions selected with the provided regexp(s).
19379 If @var{regexp} is provided, print only the functions whose names
19380 match the regular expression @var{regexp}.
19381 Thus, @samp{info fun step} finds all functions whose
19382 names include @code{step}; @samp{info fun ^step} finds those whose names
19383 start with @code{step}. If a function name contains characters that
19384 conflict with the regular expression language (e.g.@:
19385 @samp{operator*()}), they may be quoted with a backslash.
19387 If @var{type_regexp} is provided, print only the functions whose
19388 types, as printed by the @code{whatis} command, match
19389 the regular expression @var{type_regexp}.
19390 If @var{type_regexp} contains space(s), it should be enclosed in
19391 quote characters. If needed, use backslash to escape the meaning
19392 of special characters or quotes.
19393 Thus, @samp{info fun -t '^int ('} finds the functions that return
19394 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19395 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19396 finds the functions whose names start with @code{step} and that return
19399 If both @var{regexp} and @var{type_regexp} are provided, a function
19400 is printed only if its name matches @var{regexp} and its type matches
19404 @kindex info variables
19405 @item info variables [-q] [-n]
19406 Print the names and data types of all variables that are defined
19407 outside of functions (i.e.@: excluding local variables).
19408 The printed variables are grouped by source files and annotated with
19409 their respective source line numbers.
19411 In programs using different languages, @value{GDBN} chooses the syntax
19412 to print the variable name and type according to the
19413 @samp{set language} value: using @samp{set language auto}
19414 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19415 language of the variable, other values mean to use
19416 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19418 The @samp{-n} flag excludes non-debugging symbols from the results.
19420 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19421 printing header information and messages explaining why no variables
19424 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19425 Like @kbd{info variables}, but only print the variables selected
19426 with the provided regexp(s).
19428 If @var{regexp} is provided, print only the variables whose names
19429 match the regular expression @var{regexp}.
19431 If @var{type_regexp} is provided, print only the variables whose
19432 types, as printed by the @code{whatis} command, match
19433 the regular expression @var{type_regexp}.
19434 If @var{type_regexp} contains space(s), it should be enclosed in
19435 quote characters. If needed, use backslash to escape the meaning
19436 of special characters or quotes.
19438 If both @var{regexp} and @var{type_regexp} are provided, an argument
19439 is printed only if its name matches @var{regexp} and its type matches
19442 @kindex info modules
19444 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19445 List all Fortran modules in the program, or all modules matching the
19446 optional regular expression @var{regexp}.
19448 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19449 printing header information and messages explaining why no modules
19452 @kindex info module
19453 @cindex Fortran modules, information about
19454 @cindex functions and variables by Fortran module
19455 @cindex module functions and variables
19456 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19457 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19458 List all functions or variables within all Fortran modules. The set
19459 of functions or variables listed can be limited by providing some or
19460 all of the optional regular expressions. If @var{module-regexp} is
19461 provided, then only Fortran modules matching @var{module-regexp} will
19462 be searched. Only functions or variables whose type matches the
19463 optional regular expression @var{type-regexp} will be listed. And
19464 only functions or variables whose name matches the optional regular
19465 expression @var{regexp} will be listed.
19467 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19468 printing header information and messages explaining why no functions
19469 or variables have been printed.
19471 @kindex info classes
19472 @cindex Objective-C, classes and selectors
19474 @itemx info classes @var{regexp}
19475 Display all Objective-C classes in your program, or
19476 (with the @var{regexp} argument) all those matching a particular regular
19479 @kindex info selectors
19480 @item info selectors
19481 @itemx info selectors @var{regexp}
19482 Display all Objective-C selectors in your program, or
19483 (with the @var{regexp} argument) all those matching a particular regular
19487 This was never implemented.
19488 @kindex info methods
19490 @itemx info methods @var{regexp}
19491 The @code{info methods} command permits the user to examine all defined
19492 methods within C@t{++} program, or (with the @var{regexp} argument) a
19493 specific set of methods found in the various C@t{++} classes. Many
19494 C@t{++} classes provide a large number of methods. Thus, the output
19495 from the @code{ptype} command can be overwhelming and hard to use. The
19496 @code{info-methods} command filters the methods, printing only those
19497 which match the regular-expression @var{regexp}.
19500 @cindex opaque data types
19501 @kindex set opaque-type-resolution
19502 @item set opaque-type-resolution on
19503 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19504 declared as a pointer to a @code{struct}, @code{class}, or
19505 @code{union}---for example, @code{struct MyType *}---that is used in one
19506 source file although the full declaration of @code{struct MyType} is in
19507 another source file. The default is on.
19509 A change in the setting of this subcommand will not take effect until
19510 the next time symbols for a file are loaded.
19512 @item set opaque-type-resolution off
19513 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19514 is printed as follows:
19516 @{<no data fields>@}
19519 @kindex show opaque-type-resolution
19520 @item show opaque-type-resolution
19521 Show whether opaque types are resolved or not.
19523 @kindex set print symbol-loading
19524 @cindex print messages when symbols are loaded
19525 @item set print symbol-loading
19526 @itemx set print symbol-loading full
19527 @itemx set print symbol-loading brief
19528 @itemx set print symbol-loading off
19529 The @code{set print symbol-loading} command allows you to control the
19530 printing of messages when @value{GDBN} loads symbol information.
19531 By default a message is printed for the executable and one for each
19532 shared library, and normally this is what you want. However, when
19533 debugging apps with large numbers of shared libraries these messages
19535 When set to @code{brief} a message is printed for each executable,
19536 and when @value{GDBN} loads a collection of shared libraries at once
19537 it will only print one message regardless of the number of shared
19538 libraries. When set to @code{off} no messages are printed.
19540 @kindex show print symbol-loading
19541 @item show print symbol-loading
19542 Show whether messages will be printed when a @value{GDBN} command
19543 entered from the keyboard causes symbol information to be loaded.
19545 @kindex maint print symbols
19546 @cindex symbol dump
19547 @kindex maint print psymbols
19548 @cindex partial symbol dump
19549 @kindex maint print msymbols
19550 @cindex minimal symbol dump
19551 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19552 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19553 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19554 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19555 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19556 Write a dump of debugging symbol data into the file @var{filename} or
19557 the terminal if @var{filename} is unspecified.
19558 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19560 If @code{-pc @var{address}} is specified, only dump symbols for the file
19561 with code at that address. Note that @var{address} may be a symbol like
19563 If @code{-source @var{source}} is specified, only dump symbols for that
19566 These commands are used to debug the @value{GDBN} symbol-reading code.
19567 These commands do not modify internal @value{GDBN} state, therefore
19568 @samp{maint print symbols} will only print symbols for already expanded symbol
19570 You can use the command @code{info sources} to find out which files these are.
19571 If you use @samp{maint print psymbols} instead, the dump shows information
19572 about symbols that @value{GDBN} only knows partially---that is, symbols
19573 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19574 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19577 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19578 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19580 @kindex maint info symtabs
19581 @kindex maint info psymtabs
19582 @cindex listing @value{GDBN}'s internal symbol tables
19583 @cindex symbol tables, listing @value{GDBN}'s internal
19584 @cindex full symbol tables, listing @value{GDBN}'s internal
19585 @cindex partial symbol tables, listing @value{GDBN}'s internal
19586 @item maint info symtabs @r{[} @var{regexp} @r{]}
19587 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19589 List the @code{struct symtab} or @code{struct partial_symtab}
19590 structures whose names match @var{regexp}. If @var{regexp} is not
19591 given, list them all. The output includes expressions which you can
19592 copy into a @value{GDBN} debugging this one to examine a particular
19593 structure in more detail. For example:
19596 (@value{GDBP}) maint info psymtabs dwarf2read
19597 @{ objfile /home/gnu/build/gdb/gdb
19598 ((struct objfile *) 0x82e69d0)
19599 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19600 ((struct partial_symtab *) 0x8474b10)
19603 text addresses 0x814d3c8 -- 0x8158074
19604 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19605 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19606 dependencies (none)
19609 (@value{GDBP}) maint info symtabs
19613 We see that there is one partial symbol table whose filename contains
19614 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19615 and we see that @value{GDBN} has not read in any symtabs yet at all.
19616 If we set a breakpoint on a function, that will cause @value{GDBN} to
19617 read the symtab for the compilation unit containing that function:
19620 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19621 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19623 (@value{GDBP}) maint info symtabs
19624 @{ objfile /home/gnu/build/gdb/gdb
19625 ((struct objfile *) 0x82e69d0)
19626 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19627 ((struct symtab *) 0x86c1f38)
19630 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19631 linetable ((struct linetable *) 0x8370fa0)
19632 debugformat DWARF 2
19638 @kindex maint info line-table
19639 @cindex listing @value{GDBN}'s internal line tables
19640 @cindex line tables, listing @value{GDBN}'s internal
19641 @item maint info line-table @r{[} @var{regexp} @r{]}
19643 List the @code{struct linetable} from all @code{struct symtab}
19644 instances whose name matches @var{regexp}. If @var{regexp} is not
19645 given, list the @code{struct linetable} from all @code{struct symtab}.
19647 @kindex maint set symbol-cache-size
19648 @cindex symbol cache size
19649 @item maint set symbol-cache-size @var{size}
19650 Set the size of the symbol cache to @var{size}.
19651 The default size is intended to be good enough for debugging
19652 most applications. This option exists to allow for experimenting
19653 with different sizes.
19655 @kindex maint show symbol-cache-size
19656 @item maint show symbol-cache-size
19657 Show the size of the symbol cache.
19659 @kindex maint print symbol-cache
19660 @cindex symbol cache, printing its contents
19661 @item maint print symbol-cache
19662 Print the contents of the symbol cache.
19663 This is useful when debugging symbol cache issues.
19665 @kindex maint print symbol-cache-statistics
19666 @cindex symbol cache, printing usage statistics
19667 @item maint print symbol-cache-statistics
19668 Print symbol cache usage statistics.
19669 This helps determine how well the cache is being utilized.
19671 @kindex maint flush symbol-cache
19672 @kindex maint flush-symbol-cache
19673 @cindex symbol cache, flushing
19674 @item maint flush symbol-cache
19675 @itemx maint flush-symbol-cache
19676 Flush the contents of the symbol cache, all entries are removed. This
19677 command is useful when debugging the symbol cache. It is also useful
19678 when collecting performance data. The command @code{maint
19679 flush-symbol-cache} is deprecated in favor of @code{maint flush
19685 @chapter Altering Execution
19687 Once you think you have found an error in your program, you might want to
19688 find out for certain whether correcting the apparent error would lead to
19689 correct results in the rest of the run. You can find the answer by
19690 experiment, using the @value{GDBN} features for altering execution of the
19693 For example, you can store new values into variables or memory
19694 locations, give your program a signal, restart it at a different
19695 address, or even return prematurely from a function.
19698 * Assignment:: Assignment to variables
19699 * Jumping:: Continuing at a different address
19700 * Signaling:: Giving your program a signal
19701 * Returning:: Returning from a function
19702 * Calling:: Calling your program's functions
19703 * Patching:: Patching your program
19704 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19708 @section Assignment to Variables
19711 @cindex setting variables
19712 To alter the value of a variable, evaluate an assignment expression.
19713 @xref{Expressions, ,Expressions}. For example,
19720 stores the value 4 into the variable @code{x}, and then prints the
19721 value of the assignment expression (which is 4).
19722 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19723 information on operators in supported languages.
19725 @kindex set variable
19726 @cindex variables, setting
19727 If you are not interested in seeing the value of the assignment, use the
19728 @code{set} command instead of the @code{print} command. @code{set} is
19729 really the same as @code{print} except that the expression's value is
19730 not printed and is not put in the value history (@pxref{Value History,
19731 ,Value History}). The expression is evaluated only for its effects.
19733 If the beginning of the argument string of the @code{set} command
19734 appears identical to a @code{set} subcommand, use the @code{set
19735 variable} command instead of just @code{set}. This command is identical
19736 to @code{set} except for its lack of subcommands. For example, if your
19737 program has a variable @code{width}, you get an error if you try to set
19738 a new value with just @samp{set width=13}, because @value{GDBN} has the
19739 command @code{set width}:
19742 (@value{GDBP}) whatis width
19744 (@value{GDBP}) p width
19746 (@value{GDBP}) set width=47
19747 Invalid syntax in expression.
19751 The invalid expression, of course, is @samp{=47}. In
19752 order to actually set the program's variable @code{width}, use
19755 (@value{GDBP}) set var width=47
19758 Because the @code{set} command has many subcommands that can conflict
19759 with the names of program variables, it is a good idea to use the
19760 @code{set variable} command instead of just @code{set}. For example, if
19761 your program has a variable @code{g}, you run into problems if you try
19762 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19763 the command @code{set gnutarget}, abbreviated @code{set g}:
19767 (@value{GDBP}) whatis g
19771 (@value{GDBP}) set g=4
19775 The program being debugged has been started already.
19776 Start it from the beginning? (y or n) y
19777 Starting program: /home/smith/cc_progs/a.out
19778 "/home/smith/cc_progs/a.out": can't open to read symbols:
19779 Invalid bfd target.
19780 (@value{GDBP}) show g
19781 The current BFD target is "=4".
19786 The program variable @code{g} did not change, and you silently set the
19787 @code{gnutarget} to an invalid value. In order to set the variable
19791 (@value{GDBP}) set var g=4
19794 @value{GDBN} allows more implicit conversions in assignments than C; you can
19795 freely store an integer value into a pointer variable or vice versa,
19796 and you can convert any structure to any other structure that is the
19797 same length or shorter.
19798 @comment FIXME: how do structs align/pad in these conversions?
19799 @comment /doc@cygnus.com 18dec1990
19801 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19802 construct to generate a value of specified type at a specified address
19803 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19804 to memory location @code{0x83040} as an integer (which implies a certain size
19805 and representation in memory), and
19808 set @{int@}0x83040 = 4
19812 stores the value 4 into that memory location.
19815 @section Continuing at a Different Address
19817 Ordinarily, when you continue your program, you do so at the place where
19818 it stopped, with the @code{continue} command. You can instead continue at
19819 an address of your own choosing, with the following commands:
19823 @kindex j @r{(@code{jump})}
19824 @item jump @var{location}
19825 @itemx j @var{location}
19826 Resume execution at @var{location}. Execution stops again immediately
19827 if there is a breakpoint there. @xref{Specify Location}, for a description
19828 of the different forms of @var{location}. It is common
19829 practice to use the @code{tbreak} command in conjunction with
19830 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19832 The @code{jump} command does not change the current stack frame, or
19833 the stack pointer, or the contents of any memory location or any
19834 register other than the program counter. If @var{location} is in
19835 a different function from the one currently executing, the results may
19836 be bizarre if the two functions expect different patterns of arguments or
19837 of local variables. For this reason, the @code{jump} command requests
19838 confirmation if the specified line is not in the function currently
19839 executing. However, even bizarre results are predictable if you are
19840 well acquainted with the machine-language code of your program.
19843 On many systems, you can get much the same effect as the @code{jump}
19844 command by storing a new value into the register @code{$pc}. The
19845 difference is that this does not start your program running; it only
19846 changes the address of where it @emph{will} run when you continue. For
19854 makes the next @code{continue} command or stepping command execute at
19855 address @code{0x485}, rather than at the address where your program stopped.
19856 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19858 The most common occasion to use the @code{jump} command is to back
19859 up---perhaps with more breakpoints set---over a portion of a program
19860 that has already executed, in order to examine its execution in more
19865 @section Giving your Program a Signal
19866 @cindex deliver a signal to a program
19870 @item signal @var{signal}
19871 Resume execution where your program is stopped, but immediately give it the
19872 signal @var{signal}. The @var{signal} can be the name or the number of a
19873 signal. For example, on many systems @code{signal 2} and @code{signal
19874 SIGINT} are both ways of sending an interrupt signal.
19876 Alternatively, if @var{signal} is zero, continue execution without
19877 giving a signal. This is useful when your program stopped on account of
19878 a signal and would ordinarily see the signal when resumed with the
19879 @code{continue} command; @samp{signal 0} causes it to resume without a
19882 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19883 delivered to the currently selected thread, not the thread that last
19884 reported a stop. This includes the situation where a thread was
19885 stopped due to a signal. So if you want to continue execution
19886 suppressing the signal that stopped a thread, you should select that
19887 same thread before issuing the @samp{signal 0} command. If you issue
19888 the @samp{signal 0} command with another thread as the selected one,
19889 @value{GDBN} detects that and asks for confirmation.
19891 Invoking the @code{signal} command is not the same as invoking the
19892 @code{kill} utility from the shell. Sending a signal with @code{kill}
19893 causes @value{GDBN} to decide what to do with the signal depending on
19894 the signal handling tables (@pxref{Signals}). The @code{signal} command
19895 passes the signal directly to your program.
19897 @code{signal} does not repeat when you press @key{RET} a second time
19898 after executing the command.
19900 @kindex queue-signal
19901 @item queue-signal @var{signal}
19902 Queue @var{signal} to be delivered immediately to the current thread
19903 when execution of the thread resumes. The @var{signal} can be the name or
19904 the number of a signal. For example, on many systems @code{signal 2} and
19905 @code{signal SIGINT} are both ways of sending an interrupt signal.
19906 The handling of the signal must be set to pass the signal to the program,
19907 otherwise @value{GDBN} will report an error.
19908 You can control the handling of signals from @value{GDBN} with the
19909 @code{handle} command (@pxref{Signals}).
19911 Alternatively, if @var{signal} is zero, any currently queued signal
19912 for the current thread is discarded and when execution resumes no signal
19913 will be delivered. This is useful when your program stopped on account
19914 of a signal and would ordinarily see the signal when resumed with the
19915 @code{continue} command.
19917 This command differs from the @code{signal} command in that the signal
19918 is just queued, execution is not resumed. And @code{queue-signal} cannot
19919 be used to pass a signal whose handling state has been set to @code{nopass}
19924 @xref{stepping into signal handlers}, for information on how stepping
19925 commands behave when the thread has a signal queued.
19928 @section Returning from a Function
19931 @cindex returning from a function
19934 @itemx return @var{expression}
19935 You can cancel execution of a function call with the @code{return}
19936 command. If you give an
19937 @var{expression} argument, its value is used as the function's return
19941 When you use @code{return}, @value{GDBN} discards the selected stack frame
19942 (and all frames within it). You can think of this as making the
19943 discarded frame return prematurely. If you wish to specify a value to
19944 be returned, give that value as the argument to @code{return}.
19946 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19947 Frame}), and any other frames inside of it, leaving its caller as the
19948 innermost remaining frame. That frame becomes selected. The
19949 specified value is stored in the registers used for returning values
19952 The @code{return} command does not resume execution; it leaves the
19953 program stopped in the state that would exist if the function had just
19954 returned. In contrast, the @code{finish} command (@pxref{Continuing
19955 and Stepping, ,Continuing and Stepping}) resumes execution until the
19956 selected stack frame returns naturally.
19958 @value{GDBN} needs to know how the @var{expression} argument should be set for
19959 the inferior. The concrete registers assignment depends on the OS ABI and the
19960 type being returned by the selected stack frame. For example it is common for
19961 OS ABI to return floating point values in FPU registers while integer values in
19962 CPU registers. Still some ABIs return even floating point values in CPU
19963 registers. Larger integer widths (such as @code{long long int}) also have
19964 specific placement rules. @value{GDBN} already knows the OS ABI from its
19965 current target so it needs to find out also the type being returned to make the
19966 assignment into the right register(s).
19968 Normally, the selected stack frame has debug info. @value{GDBN} will always
19969 use the debug info instead of the implicit type of @var{expression} when the
19970 debug info is available. For example, if you type @kbd{return -1}, and the
19971 function in the current stack frame is declared to return a @code{long long
19972 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19973 into a @code{long long int}:
19976 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19978 (@value{GDBP}) return -1
19979 Make func return now? (y or n) y
19980 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19981 43 printf ("result=%lld\n", func ());
19985 However, if the selected stack frame does not have a debug info, e.g., if the
19986 function was compiled without debug info, @value{GDBN} has to find out the type
19987 to return from user. Specifying a different type by mistake may set the value
19988 in different inferior registers than the caller code expects. For example,
19989 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19990 of a @code{long long int} result for a debug info less function (on 32-bit
19991 architectures). Therefore the user is required to specify the return type by
19992 an appropriate cast explicitly:
19995 Breakpoint 2, 0x0040050b in func ()
19996 (@value{GDBP}) return -1
19997 Return value type not available for selected stack frame.
19998 Please use an explicit cast of the value to return.
19999 (@value{GDBP}) return (long long int) -1
20000 Make selected stack frame return now? (y or n) y
20001 #0 0x00400526 in main ()
20006 @section Calling Program Functions
20009 @cindex calling functions
20010 @cindex inferior functions, calling
20011 @item print @var{expr}
20012 Evaluate the expression @var{expr} and display the resulting value.
20013 The expression may include calls to functions in the program being
20017 @item call @var{expr}
20018 Evaluate the expression @var{expr} without displaying @code{void}
20021 You can use this variant of the @code{print} command if you want to
20022 execute a function from your program that does not return anything
20023 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20024 with @code{void} returned values that @value{GDBN} will otherwise
20025 print. If the result is not void, it is printed and saved in the
20029 It is possible for the function you call via the @code{print} or
20030 @code{call} command to generate a signal (e.g., if there's a bug in
20031 the function, or if you passed it incorrect arguments). What happens
20032 in that case is controlled by the @code{set unwindonsignal} command.
20034 Similarly, with a C@t{++} program it is possible for the function you
20035 call via the @code{print} or @code{call} command to generate an
20036 exception that is not handled due to the constraints of the dummy
20037 frame. In this case, any exception that is raised in the frame, but has
20038 an out-of-frame exception handler will not be found. GDB builds a
20039 dummy-frame for the inferior function call, and the unwinder cannot
20040 seek for exception handlers outside of this dummy-frame. What happens
20041 in that case is controlled by the
20042 @code{set unwind-on-terminating-exception} command.
20045 @item set unwindonsignal
20046 @kindex set unwindonsignal
20047 @cindex unwind stack in called functions
20048 @cindex call dummy stack unwinding
20049 Set unwinding of the stack if a signal is received while in a function
20050 that @value{GDBN} called in the program being debugged. If set to on,
20051 @value{GDBN} unwinds the stack it created for the call and restores
20052 the context to what it was before the call. If set to off (the
20053 default), @value{GDBN} stops in the frame where the signal was
20056 @item show unwindonsignal
20057 @kindex show unwindonsignal
20058 Show the current setting of stack unwinding in the functions called by
20061 @item set unwind-on-terminating-exception
20062 @kindex set unwind-on-terminating-exception
20063 @cindex unwind stack in called functions with unhandled exceptions
20064 @cindex call dummy stack unwinding on unhandled exception.
20065 Set unwinding of the stack if a C@t{++} exception is raised, but left
20066 unhandled while in a function that @value{GDBN} called in the program being
20067 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20068 it created for the call and restores the context to what it was before
20069 the call. If set to off, @value{GDBN} the exception is delivered to
20070 the default C@t{++} exception handler and the inferior terminated.
20072 @item show unwind-on-terminating-exception
20073 @kindex show unwind-on-terminating-exception
20074 Show the current setting of stack unwinding in the functions called by
20077 @item set may-call-functions
20078 @kindex set may-call-functions
20079 @cindex disabling calling functions in the program
20080 @cindex calling functions in the program, disabling
20081 Set permission to call functions in the program.
20082 This controls whether @value{GDBN} will attempt to call functions in
20083 the program, such as with expressions in the @code{print} command. It
20084 defaults to @code{on}.
20086 To call a function in the program, @value{GDBN} has to temporarily
20087 modify the state of the inferior. This has potentially undesired side
20088 effects. Also, having @value{GDBN} call nested functions is likely to
20089 be erroneous and may even crash the program being debugged. You can
20090 avoid such hazards by forbidding @value{GDBN} from calling functions
20091 in the program being debugged. If calling functions in the program
20092 is forbidden, GDB will throw an error when a command (such as printing
20093 an expression) starts a function call in the program.
20095 @item show may-call-functions
20096 @kindex show may-call-functions
20097 Show permission to call functions in the program.
20101 @subsection Calling functions with no debug info
20103 @cindex no debug info functions
20104 Sometimes, a function you wish to call is missing debug information.
20105 In such case, @value{GDBN} does not know the type of the function,
20106 including the types of the function's parameters. To avoid calling
20107 the inferior function incorrectly, which could result in the called
20108 function functioning erroneously and even crash, @value{GDBN} refuses
20109 to call the function unless you tell it the type of the function.
20111 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20112 to do that. The simplest is to cast the call to the function's
20113 declared return type. For example:
20116 (@value{GDBP}) p getenv ("PATH")
20117 'getenv' has unknown return type; cast the call to its declared return type
20118 (@value{GDBP}) p (char *) getenv ("PATH")
20119 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20122 Casting the return type of a no-debug function is equivalent to
20123 casting the function to a pointer to a prototyped function that has a
20124 prototype that matches the types of the passed-in arguments, and
20125 calling that. I.e., the call above is equivalent to:
20128 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20132 and given this prototyped C or C++ function with float parameters:
20135 float multiply (float v1, float v2) @{ return v1 * v2; @}
20139 these calls are equivalent:
20142 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20143 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20146 If the function you wish to call is declared as unprototyped (i.e.@:
20147 old K&R style), you must use the cast-to-function-pointer syntax, so
20148 that @value{GDBN} knows that it needs to apply default argument
20149 promotions (promote float arguments to double). @xref{ABI, float
20150 promotion}. For example, given this unprototyped C function with
20151 float parameters, and no debug info:
20155 multiply_noproto (v1, v2)
20163 you call it like this:
20166 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20170 @section Patching Programs
20172 @cindex patching binaries
20173 @cindex writing into executables
20174 @cindex writing into corefiles
20176 By default, @value{GDBN} opens the file containing your program's
20177 executable code (or the corefile) read-only. This prevents accidental
20178 alterations to machine code; but it also prevents you from intentionally
20179 patching your program's binary.
20181 If you'd like to be able to patch the binary, you can specify that
20182 explicitly with the @code{set write} command. For example, you might
20183 want to turn on internal debugging flags, or even to make emergency
20189 @itemx set write off
20190 If you specify @samp{set write on}, @value{GDBN} opens executable and
20191 core files for both reading and writing; if you specify @kbd{set write
20192 off} (the default), @value{GDBN} opens them read-only.
20194 If you have already loaded a file, you must load it again (using the
20195 @code{exec-file} or @code{core-file} command) after changing @code{set
20196 write}, for your new setting to take effect.
20200 Display whether executable files and core files are opened for writing
20201 as well as reading.
20204 @node Compiling and Injecting Code
20205 @section Compiling and injecting code in @value{GDBN}
20206 @cindex injecting code
20207 @cindex writing into executables
20208 @cindex compiling code
20210 @value{GDBN} supports on-demand compilation and code injection into
20211 programs running under @value{GDBN}. GCC 5.0 or higher built with
20212 @file{libcc1.so} must be installed for this functionality to be enabled.
20213 This functionality is implemented with the following commands.
20216 @kindex compile code
20217 @item compile code @var{source-code}
20218 @itemx compile code -raw @var{--} @var{source-code}
20219 Compile @var{source-code} with the compiler language found as the current
20220 language in @value{GDBN} (@pxref{Languages}). If compilation and
20221 injection is not supported with the current language specified in
20222 @value{GDBN}, or the compiler does not support this feature, an error
20223 message will be printed. If @var{source-code} compiles and links
20224 successfully, @value{GDBN} will load the object-code emitted,
20225 and execute it within the context of the currently selected inferior.
20226 It is important to note that the compiled code is executed immediately.
20227 After execution, the compiled code is removed from @value{GDBN} and any
20228 new types or variables you have defined will be deleted.
20230 The command allows you to specify @var{source-code} in two ways.
20231 The simplest method is to provide a single line of code to the command.
20235 compile code printf ("hello world\n");
20238 If you specify options on the command line as well as source code, they
20239 may conflict. The @samp{--} delimiter can be used to separate options
20240 from actual source code. E.g.:
20243 compile code -r -- printf ("hello world\n");
20246 Alternatively you can enter source code as multiple lines of text. To
20247 enter this mode, invoke the @samp{compile code} command without any text
20248 following the command. This will start the multiple-line editor and
20249 allow you to type as many lines of source code as required. When you
20250 have completed typing, enter @samp{end} on its own line to exit the
20255 >printf ("hello\n");
20256 >printf ("world\n");
20260 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20261 provided @var{source-code} in a callable scope. In this case, you must
20262 specify the entry point of the code by defining a function named
20263 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20264 inferior. Using @samp{-raw} option may be needed for example when
20265 @var{source-code} requires @samp{#include} lines which may conflict with
20266 inferior symbols otherwise.
20268 @kindex compile file
20269 @item compile file @var{filename}
20270 @itemx compile file -raw @var{filename}
20271 Like @code{compile code}, but take the source code from @var{filename}.
20274 compile file /home/user/example.c
20279 @item compile print [[@var{options}] --] @var{expr}
20280 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20281 Compile and execute @var{expr} with the compiler language found as the
20282 current language in @value{GDBN} (@pxref{Languages}). By default the
20283 value of @var{expr} is printed in a format appropriate to its data type;
20284 you can choose a different format by specifying @samp{/@var{f}}, where
20285 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20286 Formats}. The @code{compile print} command accepts the same options
20287 as the @code{print} command; see @ref{print options}.
20289 @item compile print [[@var{options}] --]
20290 @itemx compile print [[@var{options}] --] /@var{f}
20291 @cindex reprint the last value
20292 Alternatively you can enter the expression (source code producing it) as
20293 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20294 command without any text following the command. This will start the
20295 multiple-line editor.
20299 The process of compiling and injecting the code can be inspected using:
20302 @anchor{set debug compile}
20303 @item set debug compile
20304 @cindex compile command debugging info
20305 Turns on or off display of @value{GDBN} process of compiling and
20306 injecting the code. The default is off.
20308 @item show debug compile
20309 Displays the current state of displaying @value{GDBN} process of
20310 compiling and injecting the code.
20312 @anchor{set debug compile-cplus-types}
20313 @item set debug compile-cplus-types
20314 @cindex compile C@t{++} type conversion
20315 Turns on or off the display of C@t{++} type conversion debugging information.
20316 The default is off.
20318 @item show debug compile-cplus-types
20319 Displays the current state of displaying debugging information for
20320 C@t{++} type conversion.
20323 @subsection Compilation options for the @code{compile} command
20325 @value{GDBN} needs to specify the right compilation options for the code
20326 to be injected, in part to make its ABI compatible with the inferior
20327 and in part to make the injected code compatible with @value{GDBN}'s
20331 The options used, in increasing precedence:
20334 @item target architecture and OS options (@code{gdbarch})
20335 These options depend on target processor type and target operating
20336 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20337 (@code{-m64}) compilation option.
20339 @item compilation options recorded in the target
20340 @value{NGCC} (since version 4.7) stores the options used for compilation
20341 into @code{DW_AT_producer} part of DWARF debugging information according
20342 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20343 explicitly specify @code{-g} during inferior compilation otherwise
20344 @value{NGCC} produces no DWARF. This feature is only relevant for
20345 platforms where @code{-g} produces DWARF by default, otherwise one may
20346 try to enforce DWARF by using @code{-gdwarf-4}.
20348 @item compilation options set by @code{set compile-args}
20352 You can override compilation options using the following command:
20355 @item set compile-args
20356 @cindex compile command options override
20357 Set compilation options used for compiling and injecting code with the
20358 @code{compile} commands. These options override any conflicting ones
20359 from the target architecture and/or options stored during inferior
20362 @item show compile-args
20363 Displays the current state of compilation options override.
20364 This does not show all the options actually used during compilation,
20365 use @ref{set debug compile} for that.
20368 @subsection Caveats when using the @code{compile} command
20370 There are a few caveats to keep in mind when using the @code{compile}
20371 command. As the caveats are different per language, the table below
20372 highlights specific issues on a per language basis.
20375 @item C code examples and caveats
20376 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20377 attempt to compile the source code with a @samp{C} compiler. The source
20378 code provided to the @code{compile} command will have much the same
20379 access to variables and types as it normally would if it were part of
20380 the program currently being debugged in @value{GDBN}.
20382 Below is a sample program that forms the basis of the examples that
20383 follow. This program has been compiled and loaded into @value{GDBN},
20384 much like any other normal debugging session.
20387 void function1 (void)
20390 printf ("function 1\n");
20393 void function2 (void)
20408 For the purposes of the examples in this section, the program above has
20409 been compiled, loaded into @value{GDBN}, stopped at the function
20410 @code{main}, and @value{GDBN} is awaiting input from the user.
20412 To access variables and types for any program in @value{GDBN}, the
20413 program must be compiled and packaged with debug information. The
20414 @code{compile} command is not an exception to this rule. Without debug
20415 information, you can still use the @code{compile} command, but you will
20416 be very limited in what variables and types you can access.
20418 So with that in mind, the example above has been compiled with debug
20419 information enabled. The @code{compile} command will have access to
20420 all variables and types (except those that may have been optimized
20421 out). Currently, as @value{GDBN} has stopped the program in the
20422 @code{main} function, the @code{compile} command would have access to
20423 the variable @code{k}. You could invoke the @code{compile} command
20424 and type some source code to set the value of @code{k}. You can also
20425 read it, or do anything with that variable you would normally do in
20426 @code{C}. Be aware that changes to inferior variables in the
20427 @code{compile} command are persistent. In the following example:
20430 compile code k = 3;
20434 the variable @code{k} is now 3. It will retain that value until
20435 something else in the example program changes it, or another
20436 @code{compile} command changes it.
20438 Normal scope and access rules apply to source code compiled and
20439 injected by the @code{compile} command. In the example, the variables
20440 @code{j} and @code{k} are not accessible yet, because the program is
20441 currently stopped in the @code{main} function, where these variables
20442 are not in scope. Therefore, the following command
20445 compile code j = 3;
20449 will result in a compilation error message.
20451 Once the program is continued, execution will bring these variables in
20452 scope, and they will become accessible; then the code you specify via
20453 the @code{compile} command will be able to access them.
20455 You can create variables and types with the @code{compile} command as
20456 part of your source code. Variables and types that are created as part
20457 of the @code{compile} command are not visible to the rest of the program for
20458 the duration of its run. This example is valid:
20461 compile code int ff = 5; printf ("ff is %d\n", ff);
20464 However, if you were to type the following into @value{GDBN} after that
20465 command has completed:
20468 compile code printf ("ff is %d\n'', ff);
20472 a compiler error would be raised as the variable @code{ff} no longer
20473 exists. Object code generated and injected by the @code{compile}
20474 command is removed when its execution ends. Caution is advised
20475 when assigning to program variables values of variables created by the
20476 code submitted to the @code{compile} command. This example is valid:
20479 compile code int ff = 5; k = ff;
20482 The value of the variable @code{ff} is assigned to @code{k}. The variable
20483 @code{k} does not require the existence of @code{ff} to maintain the value
20484 it has been assigned. However, pointers require particular care in
20485 assignment. If the source code compiled with the @code{compile} command
20486 changed the address of a pointer in the example program, perhaps to a
20487 variable created in the @code{compile} command, that pointer would point
20488 to an invalid location when the command exits. The following example
20489 would likely cause issues with your debugged program:
20492 compile code int ff = 5; p = &ff;
20495 In this example, @code{p} would point to @code{ff} when the
20496 @code{compile} command is executing the source code provided to it.
20497 However, as variables in the (example) program persist with their
20498 assigned values, the variable @code{p} would point to an invalid
20499 location when the command exists. A general rule should be followed
20500 in that you should either assign @code{NULL} to any assigned pointers,
20501 or restore a valid location to the pointer before the command exits.
20503 Similar caution must be exercised with any structs, unions, and typedefs
20504 defined in @code{compile} command. Types defined in the @code{compile}
20505 command will no longer be available in the next @code{compile} command.
20506 Therefore, if you cast a variable to a type defined in the
20507 @code{compile} command, care must be taken to ensure that any future
20508 need to resolve the type can be achieved.
20511 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20512 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20513 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20514 Compilation failed.
20515 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20519 Variables that have been optimized away by the compiler are not
20520 accessible to the code submitted to the @code{compile} command.
20521 Access to those variables will generate a compiler error which @value{GDBN}
20522 will print to the console.
20525 @subsection Compiler search for the @code{compile} command
20527 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20528 which may not be obvious for remote targets of different architecture
20529 than where @value{GDBN} is running. Environment variable @env{PATH} on
20530 @value{GDBN} host is searched for @value{NGCC} binary matching the
20531 target architecture and operating system. This search can be overriden
20532 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
20533 taken from shell that executed @value{GDBN}, it is not the value set by
20534 @value{GDBN} command @code{set environment}). @xref{Environment}.
20537 Specifically @env{PATH} is searched for binaries matching regular expression
20538 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20539 debugged. @var{arch} is processor name --- multiarch is supported, so for
20540 example both @code{i386} and @code{x86_64} targets look for pattern
20541 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20542 for pattern @code{s390x?}. @var{os} is currently supported only for
20543 pattern @code{linux(-gnu)?}.
20545 On Posix hosts the compiler driver @value{GDBN} needs to find also
20546 shared library @file{libcc1.so} from the compiler. It is searched in
20547 default shared library search path (overridable with usual environment
20548 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
20549 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20550 according to the installation of the found compiler --- as possibly
20551 specified by the @code{set compile-gcc} command.
20554 @item set compile-gcc
20555 @cindex compile command driver filename override
20556 Set compilation command used for compiling and injecting code with the
20557 @code{compile} commands. If this option is not set (it is set to
20558 an empty string), the search described above will occur --- that is the
20561 @item show compile-gcc
20562 Displays the current compile command @value{NGCC} driver filename.
20563 If set, it is the main command @command{gcc}, found usually for example
20564 under name @file{x86_64-linux-gnu-gcc}.
20568 @chapter @value{GDBN} Files
20570 @value{GDBN} needs to know the file name of the program to be debugged,
20571 both in order to read its symbol table and in order to start your
20572 program. To debug a core dump of a previous run, you must also tell
20573 @value{GDBN} the name of the core dump file.
20576 * Files:: Commands to specify files
20577 * File Caching:: Information about @value{GDBN}'s file caching
20578 * Separate Debug Files:: Debugging information in separate files
20579 * MiniDebugInfo:: Debugging information in a special section
20580 * Index Files:: Index files speed up GDB
20581 * Symbol Errors:: Errors reading symbol files
20582 * Data Files:: GDB data files
20586 @section Commands to Specify Files
20588 @cindex symbol table
20589 @cindex core dump file
20591 You may want to specify executable and core dump file names. The usual
20592 way to do this is at start-up time, using the arguments to
20593 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20594 Out of @value{GDBN}}).
20596 Occasionally it is necessary to change to a different file during a
20597 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20598 specify a file you want to use. Or you are debugging a remote target
20599 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20600 Program}). In these situations the @value{GDBN} commands to specify
20601 new files are useful.
20604 @cindex executable file
20606 @item file @var{filename}
20607 Use @var{filename} as the program to be debugged. It is read for its
20608 symbols and for the contents of pure memory. It is also the program
20609 executed when you use the @code{run} command. If you do not specify a
20610 directory and the file is not found in the @value{GDBN} working directory,
20611 @value{GDBN} uses the environment variable @env{PATH} as a list of
20612 directories to search, just as the shell does when looking for a program
20613 to run. You can change the value of this variable, for both @value{GDBN}
20614 and your program, using the @code{path} command.
20616 @cindex unlinked object files
20617 @cindex patching object files
20618 You can load unlinked object @file{.o} files into @value{GDBN} using
20619 the @code{file} command. You will not be able to ``run'' an object
20620 file, but you can disassemble functions and inspect variables. Also,
20621 if the underlying BFD functionality supports it, you could use
20622 @kbd{gdb -write} to patch object files using this technique. Note
20623 that @value{GDBN} can neither interpret nor modify relocations in this
20624 case, so branches and some initialized variables will appear to go to
20625 the wrong place. But this feature is still handy from time to time.
20628 @code{file} with no argument makes @value{GDBN} discard any information it
20629 has on both executable file and the symbol table.
20632 @item exec-file @r{[} @var{filename} @r{]}
20633 Specify that the program to be run (but not the symbol table) is found
20634 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
20635 if necessary to locate your program. Omitting @var{filename} means to
20636 discard information on the executable file.
20638 @kindex symbol-file
20639 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20640 Read symbol table information from file @var{filename}. @env{PATH} is
20641 searched when necessary. Use the @code{file} command to get both symbol
20642 table and program to run from the same file.
20644 If an optional @var{offset} is specified, it is added to the start
20645 address of each section in the symbol file. This is useful if the
20646 program is relocated at runtime, such as the Linux kernel with kASLR
20649 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20650 program's symbol table.
20652 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20653 some breakpoints and auto-display expressions. This is because they may
20654 contain pointers to the internal data recording symbols and data types,
20655 which are part of the old symbol table data being discarded inside
20658 @code{symbol-file} does not repeat if you press @key{RET} again after
20661 When @value{GDBN} is configured for a particular environment, it
20662 understands debugging information in whatever format is the standard
20663 generated for that environment; you may use either a @sc{gnu} compiler, or
20664 other compilers that adhere to the local conventions.
20665 Best results are usually obtained from @sc{gnu} compilers; for example,
20666 using @code{@value{NGCC}} you can generate debugging information for
20669 For most kinds of object files, with the exception of old SVR3 systems
20670 using COFF, the @code{symbol-file} command does not normally read the
20671 symbol table in full right away. Instead, it scans the symbol table
20672 quickly to find which source files and which symbols are present. The
20673 details are read later, one source file at a time, as they are needed.
20675 The purpose of this two-stage reading strategy is to make @value{GDBN}
20676 start up faster. For the most part, it is invisible except for
20677 occasional pauses while the symbol table details for a particular source
20678 file are being read. (The @code{set verbose} command can turn these
20679 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20680 Warnings and Messages}.)
20682 We have not implemented the two-stage strategy for COFF yet. When the
20683 symbol table is stored in COFF format, @code{symbol-file} reads the
20684 symbol table data in full right away. Note that ``stabs-in-COFF''
20685 still does the two-stage strategy, since the debug info is actually
20689 @cindex reading symbols immediately
20690 @cindex symbols, reading immediately
20691 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20692 @itemx file @r{[} -readnow @r{]} @var{filename}
20693 You can override the @value{GDBN} two-stage strategy for reading symbol
20694 tables by using the @samp{-readnow} option with any of the commands that
20695 load symbol table information, if you want to be sure @value{GDBN} has the
20696 entire symbol table available.
20698 @cindex @code{-readnever}, option for symbol-file command
20699 @cindex never read symbols
20700 @cindex symbols, never read
20701 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20702 @itemx file @r{[} -readnever @r{]} @var{filename}
20703 You can instruct @value{GDBN} to never read the symbolic information
20704 contained in @var{filename} by using the @samp{-readnever} option.
20705 @xref{--readnever}.
20707 @c FIXME: for now no mention of directories, since this seems to be in
20708 @c flux. 13mar1992 status is that in theory GDB would look either in
20709 @c current dir or in same dir as myprog; but issues like competing
20710 @c GDB's, or clutter in system dirs, mean that in practice right now
20711 @c only current dir is used. FFish says maybe a special GDB hierarchy
20712 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20716 @item core-file @r{[}@var{filename}@r{]}
20718 Specify the whereabouts of a core dump file to be used as the ``contents
20719 of memory''. Traditionally, core files contain only some parts of the
20720 address space of the process that generated them; @value{GDBN} can access the
20721 executable file itself for other parts.
20723 @code{core-file} with no argument specifies that no core file is
20726 Note that the core file is ignored when your program is actually running
20727 under @value{GDBN}. So, if you have been running your program and you
20728 wish to debug a core file instead, you must kill the subprocess in which
20729 the program is running. To do this, use the @code{kill} command
20730 (@pxref{Kill Process, ,Killing the Child Process}).
20732 @kindex add-symbol-file
20733 @cindex dynamic linking
20734 @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{]}
20735 The @code{add-symbol-file} command reads additional symbol table
20736 information from the file @var{filename}. You would use this command
20737 when @var{filename} has been dynamically loaded (by some other means)
20738 into the program that is running. The @var{textaddress} parameter gives
20739 the memory address at which the file's text section has been loaded.
20740 You can additionally specify the base address of other sections using
20741 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20742 If a section is omitted, @value{GDBN} will use its default addresses
20743 as found in @var{filename}. Any @var{address} or @var{textaddress}
20744 can be given as an expression.
20746 If an optional @var{offset} is specified, it is added to the start
20747 address of each section, except those for which the address was
20748 specified explicitly.
20750 The symbol table of the file @var{filename} is added to the symbol table
20751 originally read with the @code{symbol-file} command. You can use the
20752 @code{add-symbol-file} command any number of times; the new symbol data
20753 thus read is kept in addition to the old.
20755 Changes can be reverted using the command @code{remove-symbol-file}.
20757 @cindex relocatable object files, reading symbols from
20758 @cindex object files, relocatable, reading symbols from
20759 @cindex reading symbols from relocatable object files
20760 @cindex symbols, reading from relocatable object files
20761 @cindex @file{.o} files, reading symbols from
20762 Although @var{filename} is typically a shared library file, an
20763 executable file, or some other object file which has been fully
20764 relocated for loading into a process, you can also load symbolic
20765 information from relocatable @file{.o} files, as long as:
20769 the file's symbolic information refers only to linker symbols defined in
20770 that file, not to symbols defined by other object files,
20772 every section the file's symbolic information refers to has actually
20773 been loaded into the inferior, as it appears in the file, and
20775 you can determine the address at which every section was loaded, and
20776 provide these to the @code{add-symbol-file} command.
20780 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20781 relocatable files into an already running program; such systems
20782 typically make the requirements above easy to meet. However, it's
20783 important to recognize that many native systems use complex link
20784 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20785 assembly, for example) that make the requirements difficult to meet. In
20786 general, one cannot assume that using @code{add-symbol-file} to read a
20787 relocatable object file's symbolic information will have the same effect
20788 as linking the relocatable object file into the program in the normal
20791 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20793 @kindex remove-symbol-file
20794 @item remove-symbol-file @var{filename}
20795 @item remove-symbol-file -a @var{address}
20796 Remove a symbol file added via the @code{add-symbol-file} command. The
20797 file to remove can be identified by its @var{filename} or by an @var{address}
20798 that lies within the boundaries of this symbol file in memory. Example:
20801 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20802 add symbol table from file "/home/user/gdb/mylib.so" at
20803 .text_addr = 0x7ffff7ff9480
20805 Reading symbols from /home/user/gdb/mylib.so...
20806 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20807 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20812 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20814 @kindex add-symbol-file-from-memory
20815 @cindex @code{syscall DSO}
20816 @cindex load symbols from memory
20817 @item add-symbol-file-from-memory @var{address}
20818 Load symbols from the given @var{address} in a dynamically loaded
20819 object file whose image is mapped directly into the inferior's memory.
20820 For example, the Linux kernel maps a @code{syscall DSO} into each
20821 process's address space; this DSO provides kernel-specific code for
20822 some system calls. The argument can be any expression whose
20823 evaluation yields the address of the file's shared object file header.
20824 For this command to work, you must have used @code{symbol-file} or
20825 @code{exec-file} commands in advance.
20828 @item section @var{section} @var{addr}
20829 The @code{section} command changes the base address of the named
20830 @var{section} of the exec file to @var{addr}. This can be used if the
20831 exec file does not contain section addresses, (such as in the
20832 @code{a.out} format), or when the addresses specified in the file
20833 itself are wrong. Each section must be changed separately. The
20834 @code{info files} command, described below, lists all the sections and
20838 @kindex info target
20841 @code{info files} and @code{info target} are synonymous; both print the
20842 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20843 including the names of the executable and core dump files currently in
20844 use by @value{GDBN}, and the files from which symbols were loaded. The
20845 command @code{help target} lists all possible targets rather than
20848 @kindex maint info sections
20849 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
20850 Another command that can give you extra information about program sections
20851 is @code{maint info sections}. In addition to the section information
20852 displayed by @code{info files}, this command displays the flags and file
20853 offset of each section in the executable and core dump files.
20855 When @samp{-all-objects} is passed then sections from all loaded object
20856 files, including shared libraries, are printed.
20858 The optional @var{filter-list} is a space separated list of filter
20859 keywords. Sections that match any one of the filter criteria will be
20860 printed. There are two types of filter:
20863 @item @var{section-name}
20864 Display information about any section named @var{section-name}.
20865 @item @var{section-flag}
20866 Display information for any section with @var{section-flag}. The
20867 section flags that @value{GDBN} currently knows about are:
20870 Section will have space allocated in the process when loaded.
20871 Set for all sections except those containing debug information.
20873 Section will be loaded from the file into the child process memory.
20874 Set for pre-initialized code and data, clear for @code{.bss} sections.
20876 Section needs to be relocated before loading.
20878 Section cannot be modified by the child process.
20880 Section contains executable code only.
20882 Section contains data only (no executable code).
20884 Section will reside in ROM.
20886 Section contains data for constructor/destructor lists.
20888 Section is not empty.
20890 An instruction to the linker to not output the section.
20891 @item COFF_SHARED_LIBRARY
20892 A notification to the linker that the section contains
20893 COFF shared library information.
20895 Section contains common symbols.
20899 @kindex maint info target-sections
20900 @item maint info target-sections
20901 This command prints @value{GDBN}'s internal section table. For each
20902 target @value{GDBN} maintains a table containing the allocatable
20903 sections from all currently mapped objects, along with information
20904 about where the section is mapped.
20906 @kindex set trust-readonly-sections
20907 @cindex read-only sections
20908 @item set trust-readonly-sections on
20909 Tell @value{GDBN} that readonly sections in your object file
20910 really are read-only (i.e.@: that their contents will not change).
20911 In that case, @value{GDBN} can fetch values from these sections
20912 out of the object file, rather than from the target program.
20913 For some targets (notably embedded ones), this can be a significant
20914 enhancement to debugging performance.
20916 The default is off.
20918 @item set trust-readonly-sections off
20919 Tell @value{GDBN} not to trust readonly sections. This means that
20920 the contents of the section might change while the program is running,
20921 and must therefore be fetched from the target when needed.
20923 @item show trust-readonly-sections
20924 Show the current setting of trusting readonly sections.
20927 All file-specifying commands allow both absolute and relative file names
20928 as arguments. @value{GDBN} always converts the file name to an absolute file
20929 name and remembers it that way.
20931 @cindex shared libraries
20932 @anchor{Shared Libraries}
20933 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20934 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20935 DSBT (TIC6X) shared libraries.
20937 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20938 shared libraries. @xref{Expat}.
20940 @value{GDBN} automatically loads symbol definitions from shared libraries
20941 when you use the @code{run} command, or when you examine a core file.
20942 (Before you issue the @code{run} command, @value{GDBN} does not understand
20943 references to a function in a shared library, however---unless you are
20944 debugging a core file).
20946 @c FIXME: some @value{GDBN} release may permit some refs to undef
20947 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20948 @c FIXME...lib; check this from time to time when updating manual
20950 There are times, however, when you may wish to not automatically load
20951 symbol definitions from shared libraries, such as when they are
20952 particularly large or there are many of them.
20954 To control the automatic loading of shared library symbols, use the
20958 @kindex set auto-solib-add
20959 @item set auto-solib-add @var{mode}
20960 If @var{mode} is @code{on}, symbols from all shared object libraries
20961 will be loaded automatically when the inferior begins execution, you
20962 attach to an independently started inferior, or when the dynamic linker
20963 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20964 is @code{off}, symbols must be loaded manually, using the
20965 @code{sharedlibrary} command. The default value is @code{on}.
20967 @cindex memory used for symbol tables
20968 If your program uses lots of shared libraries with debug info that
20969 takes large amounts of memory, you can decrease the @value{GDBN}
20970 memory footprint by preventing it from automatically loading the
20971 symbols from shared libraries. To that end, type @kbd{set
20972 auto-solib-add off} before running the inferior, then load each
20973 library whose debug symbols you do need with @kbd{sharedlibrary
20974 @var{regexp}}, where @var{regexp} is a regular expression that matches
20975 the libraries whose symbols you want to be loaded.
20977 @kindex show auto-solib-add
20978 @item show auto-solib-add
20979 Display the current autoloading mode.
20982 @cindex load shared library
20983 To explicitly load shared library symbols, use the @code{sharedlibrary}
20987 @kindex info sharedlibrary
20989 @item info share @var{regex}
20990 @itemx info sharedlibrary @var{regex}
20991 Print the names of the shared libraries which are currently loaded
20992 that match @var{regex}. If @var{regex} is omitted then print
20993 all shared libraries that are loaded.
20996 @item info dll @var{regex}
20997 This is an alias of @code{info sharedlibrary}.
20999 @kindex sharedlibrary
21001 @item sharedlibrary @var{regex}
21002 @itemx share @var{regex}
21003 Load shared object library symbols for files matching a
21004 Unix regular expression.
21005 As with files loaded automatically, it only loads shared libraries
21006 required by your program for a core file or after typing @code{run}. If
21007 @var{regex} is omitted all shared libraries required by your program are
21010 @item nosharedlibrary
21011 @kindex nosharedlibrary
21012 @cindex unload symbols from shared libraries
21013 Unload all shared object library symbols. This discards all symbols
21014 that have been loaded from all shared libraries. Symbols from shared
21015 libraries that were loaded by explicit user requests are not
21019 Sometimes you may wish that @value{GDBN} stops and gives you control
21020 when any of shared library events happen. The best way to do this is
21021 to use @code{catch load} and @code{catch unload} (@pxref{Set
21024 @value{GDBN} also supports the @code{set stop-on-solib-events}
21025 command for this. This command exists for historical reasons. It is
21026 less useful than setting a catchpoint, because it does not allow for
21027 conditions or commands as a catchpoint does.
21030 @item set stop-on-solib-events
21031 @kindex set stop-on-solib-events
21032 This command controls whether @value{GDBN} should give you control
21033 when the dynamic linker notifies it about some shared library event.
21034 The most common event of interest is loading or unloading of a new
21037 @item show stop-on-solib-events
21038 @kindex show stop-on-solib-events
21039 Show whether @value{GDBN} stops and gives you control when shared
21040 library events happen.
21043 Shared libraries are also supported in many cross or remote debugging
21044 configurations. @value{GDBN} needs to have access to the target's libraries;
21045 this can be accomplished either by providing copies of the libraries
21046 on the host system, or by asking @value{GDBN} to automatically retrieve the
21047 libraries from the target. If copies of the target libraries are
21048 provided, they need to be the same as the target libraries, although the
21049 copies on the target can be stripped as long as the copies on the host are
21052 @cindex where to look for shared libraries
21053 For remote debugging, you need to tell @value{GDBN} where the target
21054 libraries are, so that it can load the correct copies---otherwise, it
21055 may try to load the host's libraries. @value{GDBN} has two variables
21056 to specify the search directories for target libraries.
21059 @cindex prefix for executable and shared library file names
21060 @cindex system root, alternate
21061 @kindex set solib-absolute-prefix
21062 @kindex set sysroot
21063 @item set sysroot @var{path}
21064 Use @var{path} as the system root for the program being debugged. Any
21065 absolute shared library paths will be prefixed with @var{path}; many
21066 runtime loaders store the absolute paths to the shared library in the
21067 target program's memory. When starting processes remotely, and when
21068 attaching to already-running processes (local or remote), their
21069 executable filenames will be prefixed with @var{path} if reported to
21070 @value{GDBN} as absolute by the operating system. If you use
21071 @code{set sysroot} to find executables and shared libraries, they need
21072 to be laid out in the same way that they are on the target, with
21073 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21076 If @var{path} starts with the sequence @file{target:} and the target
21077 system is remote then @value{GDBN} will retrieve the target binaries
21078 from the remote system. This is only supported when using a remote
21079 target that supports the @code{remote get} command (@pxref{File
21080 Transfer,,Sending files to a remote system}). The part of @var{path}
21081 following the initial @file{target:} (if present) is used as system
21082 root prefix on the remote file system. If @var{path} starts with the
21083 sequence @file{remote:} this is converted to the sequence
21084 @file{target:} by @code{set sysroot}@footnote{Historically the
21085 functionality to retrieve binaries from the remote system was
21086 provided by prefixing @var{path} with @file{remote:}}. If you want
21087 to specify a local system root using a directory that happens to be
21088 named @file{target:} or @file{remote:}, you need to use some
21089 equivalent variant of the name like @file{./target:}.
21091 For targets with an MS-DOS based filesystem, such as MS-Windows,
21092 @value{GDBN} tries prefixing a few variants of the target
21093 absolute file name with @var{path}. But first, on Unix hosts,
21094 @value{GDBN} converts all backslash directory separators into forward
21095 slashes, because the backslash is not a directory separator on Unix:
21098 c:\foo\bar.dll @result{} c:/foo/bar.dll
21101 Then, @value{GDBN} attempts prefixing the target file name with
21102 @var{path}, and looks for the resulting file name in the host file
21106 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21109 If that does not find the binary, @value{GDBN} tries removing
21110 the @samp{:} character from the drive spec, both for convenience, and,
21111 for the case of the host file system not supporting file names with
21115 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21118 This makes it possible to have a system root that mirrors a target
21119 with more than one drive. E.g., you may want to setup your local
21120 copies of the target system shared libraries like so (note @samp{c} vs
21124 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21125 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21126 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21130 and point the system root at @file{/path/to/sysroot}, so that
21131 @value{GDBN} can find the correct copies of both
21132 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21134 If that still does not find the binary, @value{GDBN} tries
21135 removing the whole drive spec from the target file name:
21138 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21141 This last lookup makes it possible to not care about the drive name,
21142 if you don't want or need to.
21144 The @code{set solib-absolute-prefix} command is an alias for @code{set
21147 @cindex default system root
21148 @cindex @samp{--with-sysroot}
21149 You can set the default system root by using the configure-time
21150 @samp{--with-sysroot} option. If the system root is inside
21151 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21152 @samp{--exec-prefix}), then the default system root will be updated
21153 automatically if the installed @value{GDBN} is moved to a new
21156 @kindex show sysroot
21158 Display the current executable and shared library prefix.
21160 @kindex set solib-search-path
21161 @item set solib-search-path @var{path}
21162 If this variable is set, @var{path} is a colon-separated list of
21163 directories to search for shared libraries. @samp{solib-search-path}
21164 is used after @samp{sysroot} fails to locate the library, or if the
21165 path to the library is relative instead of absolute. If you want to
21166 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21167 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21168 finding your host's libraries. @samp{sysroot} is preferred; setting
21169 it to a nonexistent directory may interfere with automatic loading
21170 of shared library symbols.
21172 @kindex show solib-search-path
21173 @item show solib-search-path
21174 Display the current shared library search path.
21176 @cindex DOS file-name semantics of file names.
21177 @kindex set target-file-system-kind (unix|dos-based|auto)
21178 @kindex show target-file-system-kind
21179 @item set target-file-system-kind @var{kind}
21180 Set assumed file system kind for target reported file names.
21182 Shared library file names as reported by the target system may not
21183 make sense as is on the system @value{GDBN} is running on. For
21184 example, when remote debugging a target that has MS-DOS based file
21185 system semantics, from a Unix host, the target may be reporting to
21186 @value{GDBN} a list of loaded shared libraries with file names such as
21187 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21188 drive letters, so the @samp{c:\} prefix is not normally understood as
21189 indicating an absolute file name, and neither is the backslash
21190 normally considered a directory separator character. In that case,
21191 the native file system would interpret this whole absolute file name
21192 as a relative file name with no directory components. This would make
21193 it impossible to point @value{GDBN} at a copy of the remote target's
21194 shared libraries on the host using @code{set sysroot}, and impractical
21195 with @code{set solib-search-path}. Setting
21196 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21197 to interpret such file names similarly to how the target would, and to
21198 map them to file names valid on @value{GDBN}'s native file system
21199 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21200 to one of the supported file system kinds. In that case, @value{GDBN}
21201 tries to determine the appropriate file system variant based on the
21202 current target's operating system (@pxref{ABI, ,Configuring the
21203 Current ABI}). The supported file system settings are:
21207 Instruct @value{GDBN} to assume the target file system is of Unix
21208 kind. Only file names starting the forward slash (@samp{/}) character
21209 are considered absolute, and the directory separator character is also
21213 Instruct @value{GDBN} to assume the target file system is DOS based.
21214 File names starting with either a forward slash, or a drive letter
21215 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21216 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21217 considered directory separators.
21220 Instruct @value{GDBN} to use the file system kind associated with the
21221 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21222 This is the default.
21226 @cindex file name canonicalization
21227 @cindex base name differences
21228 When processing file names provided by the user, @value{GDBN}
21229 frequently needs to compare them to the file names recorded in the
21230 program's debug info. Normally, @value{GDBN} compares just the
21231 @dfn{base names} of the files as strings, which is reasonably fast
21232 even for very large programs. (The base name of a file is the last
21233 portion of its name, after stripping all the leading directories.)
21234 This shortcut in comparison is based upon the assumption that files
21235 cannot have more than one base name. This is usually true, but
21236 references to files that use symlinks or similar filesystem
21237 facilities violate that assumption. If your program records files
21238 using such facilities, or if you provide file names to @value{GDBN}
21239 using symlinks etc., you can set @code{basenames-may-differ} to
21240 @code{true} to instruct @value{GDBN} to completely canonicalize each
21241 pair of file names it needs to compare. This will make file-name
21242 comparisons accurate, but at a price of a significant slowdown.
21245 @item set basenames-may-differ
21246 @kindex set basenames-may-differ
21247 Set whether a source file may have multiple base names.
21249 @item show basenames-may-differ
21250 @kindex show basenames-may-differ
21251 Show whether a source file may have multiple base names.
21255 @section File Caching
21256 @cindex caching of opened files
21257 @cindex caching of bfd objects
21259 To speed up file loading, and reduce memory usage, @value{GDBN} will
21260 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21261 BFD, bfd, The Binary File Descriptor Library}. The following commands
21262 allow visibility and control of the caching behavior.
21265 @kindex maint info bfds
21266 @item maint info bfds
21267 This prints information about each @code{bfd} object that is known to
21270 @kindex maint set bfd-sharing
21271 @kindex maint show bfd-sharing
21272 @kindex bfd caching
21273 @item maint set bfd-sharing
21274 @item maint show bfd-sharing
21275 Control whether @code{bfd} objects can be shared. When sharing is
21276 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21277 than reopening the same file. Turning sharing off does not cause
21278 already shared @code{bfd} objects to be unshared, but all future files
21279 that are opened will create a new @code{bfd} object. Similarly,
21280 re-enabling sharing does not cause multiple existing @code{bfd}
21281 objects to be collapsed into a single shared @code{bfd} object.
21283 @kindex set debug bfd-cache @var{level}
21284 @kindex bfd caching
21285 @item set debug bfd-cache @var{level}
21286 Turns on debugging of the bfd cache, setting the level to @var{level}.
21288 @kindex show debug bfd-cache
21289 @kindex bfd caching
21290 @item show debug bfd-cache
21291 Show the current debugging level of the bfd cache.
21294 @node Separate Debug Files
21295 @section Debugging Information in Separate Files
21296 @cindex separate debugging information files
21297 @cindex debugging information in separate files
21298 @cindex @file{.debug} subdirectories
21299 @cindex debugging information directory, global
21300 @cindex global debugging information directories
21301 @cindex build ID, and separate debugging files
21302 @cindex @file{.build-id} directory
21304 @value{GDBN} allows you to put a program's debugging information in a
21305 file separate from the executable itself, in a way that allows
21306 @value{GDBN} to find and load the debugging information automatically.
21307 Since debugging information can be very large---sometimes larger
21308 than the executable code itself---some systems distribute debugging
21309 information for their executables in separate files, which users can
21310 install only when they need to debug a problem.
21312 @value{GDBN} supports two ways of specifying the separate debug info
21317 The executable contains a @dfn{debug link} that specifies the name of
21318 the separate debug info file. The separate debug file's name is
21319 usually @file{@var{executable}.debug}, where @var{executable} is the
21320 name of the corresponding executable file without leading directories
21321 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21322 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21323 checksum for the debug file, which @value{GDBN} uses to validate that
21324 the executable and the debug file came from the same build.
21328 The executable contains a @dfn{build ID}, a unique bit string that is
21329 also present in the corresponding debug info file. (This is supported
21330 only on some operating systems, when using the ELF or PE file formats
21331 for binary files and the @sc{gnu} Binutils.) For more details about
21332 this feature, see the description of the @option{--build-id}
21333 command-line option in @ref{Options, , Command Line Options, ld,
21334 The GNU Linker}. The debug info file's name is not specified
21335 explicitly by the build ID, but can be computed from the build ID, see
21339 Depending on the way the debug info file is specified, @value{GDBN}
21340 uses two different methods of looking for the debug file:
21344 For the ``debug link'' method, @value{GDBN} looks up the named file in
21345 the directory of the executable file, then in a subdirectory of that
21346 directory named @file{.debug}, and finally under each one of the
21347 global debug directories, in a subdirectory whose name is identical to
21348 the leading directories of the executable's absolute file name. (On
21349 MS-Windows/MS-DOS, the drive letter of the executable's leading
21350 directories is converted to a one-letter subdirectory, i.e.@:
21351 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21352 filesystems disallow colons in file names.)
21355 For the ``build ID'' method, @value{GDBN} looks in the
21356 @file{.build-id} subdirectory of each one of the global debug directories for
21357 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21358 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21359 are the rest of the bit string. (Real build ID strings are 32 or more
21360 hex characters, not 10.)
21363 So, for example, suppose you ask @value{GDBN} to debug
21364 @file{/usr/bin/ls}, which has a debug link that specifies the
21365 file @file{ls.debug}, and a build ID whose value in hex is
21366 @code{abcdef1234}. If the list of the global debug directories includes
21367 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21368 debug information files, in the indicated order:
21372 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21374 @file{/usr/bin/ls.debug}
21376 @file{/usr/bin/.debug/ls.debug}
21378 @file{/usr/lib/debug/usr/bin/ls.debug}.
21381 @anchor{debug-file-directory}
21382 Global debugging info directories default to what is set by @value{GDBN}
21383 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21384 you can also set the global debugging info directories, and view the list
21385 @value{GDBN} is currently using.
21389 @kindex set debug-file-directory
21390 @item set debug-file-directory @var{directories}
21391 Set the directories which @value{GDBN} searches for separate debugging
21392 information files to @var{directory}. Multiple path components can be set
21393 concatenating them by a path separator.
21395 @kindex show debug-file-directory
21396 @item show debug-file-directory
21397 Show the directories @value{GDBN} searches for separate debugging
21402 @cindex @code{.gnu_debuglink} sections
21403 @cindex debug link sections
21404 A debug link is a special section of the executable file named
21405 @code{.gnu_debuglink}. The section must contain:
21409 A filename, with any leading directory components removed, followed by
21412 zero to three bytes of padding, as needed to reach the next four-byte
21413 boundary within the section, and
21415 a four-byte CRC checksum, stored in the same endianness used for the
21416 executable file itself. The checksum is computed on the debugging
21417 information file's full contents by the function given below, passing
21418 zero as the @var{crc} argument.
21421 Any executable file format can carry a debug link, as long as it can
21422 contain a section named @code{.gnu_debuglink} with the contents
21425 @cindex @code{.note.gnu.build-id} sections
21426 @cindex build ID sections
21427 The build ID is a special section in the executable file (and in other
21428 ELF binary files that @value{GDBN} may consider). This section is
21429 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21430 It contains unique identification for the built files---the ID remains
21431 the same across multiple builds of the same build tree. The default
21432 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21433 content for the build ID string. The same section with an identical
21434 value is present in the original built binary with symbols, in its
21435 stripped variant, and in the separate debugging information file.
21437 The debugging information file itself should be an ordinary
21438 executable, containing a full set of linker symbols, sections, and
21439 debugging information. The sections of the debugging information file
21440 should have the same names, addresses, and sizes as the original file,
21441 but they need not contain any data---much like a @code{.bss} section
21442 in an ordinary executable.
21444 The @sc{gnu} binary utilities (Binutils) package includes the
21445 @samp{objcopy} utility that can produce
21446 the separated executable / debugging information file pairs using the
21447 following commands:
21450 @kbd{objcopy --only-keep-debug foo foo.debug}
21455 These commands remove the debugging
21456 information from the executable file @file{foo} and place it in the file
21457 @file{foo.debug}. You can use the first, second or both methods to link the
21462 The debug link method needs the following additional command to also leave
21463 behind a debug link in @file{foo}:
21466 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21469 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21470 a version of the @code{strip} command such that the command @kbd{strip foo -f
21471 foo.debug} has the same functionality as the two @code{objcopy} commands and
21472 the @code{ln -s} command above, together.
21475 Build ID gets embedded into the main executable using @code{ld --build-id} or
21476 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21477 compatibility fixes for debug files separation are present in @sc{gnu} binary
21478 utilities (Binutils) package since version 2.18.
21483 @cindex CRC algorithm definition
21484 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21485 IEEE 802.3 using the polynomial:
21487 @c TexInfo requires naked braces for multi-digit exponents for Tex
21488 @c output, but this causes HTML output to barf. HTML has to be set using
21489 @c raw commands. So we end up having to specify this equation in 2
21494 <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>
21495 + <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
21501 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21502 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21506 The function is computed byte at a time, taking the least
21507 significant bit of each byte first. The initial pattern
21508 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21509 the final result is inverted to ensure trailing zeros also affect the
21512 @emph{Note:} This is the same CRC polynomial as used in handling the
21513 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21514 However in the case of the Remote Serial Protocol, the CRC is computed
21515 @emph{most} significant bit first, and the result is not inverted, so
21516 trailing zeros have no effect on the CRC value.
21518 To complete the description, we show below the code of the function
21519 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21520 initially supplied @code{crc} argument means that an initial call to
21521 this function passing in zero will start computing the CRC using
21524 @kindex gnu_debuglink_crc32
21527 gnu_debuglink_crc32 (unsigned long crc,
21528 unsigned char *buf, size_t len)
21530 static const unsigned long crc32_table[256] =
21532 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21533 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21534 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21535 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21536 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21537 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21538 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21539 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21540 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21541 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21542 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21543 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21544 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21545 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21546 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21547 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21548 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21549 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21550 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21551 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21552 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21553 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21554 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21555 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21556 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21557 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21558 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21559 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21560 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21561 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21562 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21563 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21564 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21565 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21566 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21567 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21568 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21569 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21570 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21571 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21572 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21573 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21574 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21575 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21576 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21577 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21578 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21579 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21580 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21581 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21582 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21585 unsigned char *end;
21587 crc = ~crc & 0xffffffff;
21588 for (end = buf + len; buf < end; ++buf)
21589 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21590 return ~crc & 0xffffffff;
21595 This computation does not apply to the ``build ID'' method.
21597 @node MiniDebugInfo
21598 @section Debugging information in a special section
21599 @cindex separate debug sections
21600 @cindex @samp{.gnu_debugdata} section
21602 Some systems ship pre-built executables and libraries that have a
21603 special @samp{.gnu_debugdata} section. This feature is called
21604 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21605 is used to supply extra symbols for backtraces.
21607 The intent of this section is to provide extra minimal debugging
21608 information for use in simple backtraces. It is not intended to be a
21609 replacement for full separate debugging information (@pxref{Separate
21610 Debug Files}). The example below shows the intended use; however,
21611 @value{GDBN} does not currently put restrictions on what sort of
21612 debugging information might be included in the section.
21614 @value{GDBN} has support for this extension. If the section exists,
21615 then it is used provided that no other source of debugging information
21616 can be found, and that @value{GDBN} was configured with LZMA support.
21618 This section can be easily created using @command{objcopy} and other
21619 standard utilities:
21622 # Extract the dynamic symbols from the main binary, there is no need
21623 # to also have these in the normal symbol table.
21624 nm -D @var{binary} --format=posix --defined-only \
21625 | awk '@{ print $1 @}' | sort > dynsyms
21627 # Extract all the text (i.e. function) symbols from the debuginfo.
21628 # (Note that we actually also accept "D" symbols, for the benefit
21629 # of platforms like PowerPC64 that use function descriptors.)
21630 nm @var{binary} --format=posix --defined-only \
21631 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21634 # Keep all the function symbols not already in the dynamic symbol
21636 comm -13 dynsyms funcsyms > keep_symbols
21638 # Separate full debug info into debug binary.
21639 objcopy --only-keep-debug @var{binary} debug
21641 # Copy the full debuginfo, keeping only a minimal set of symbols and
21642 # removing some unnecessary sections.
21643 objcopy -S --remove-section .gdb_index --remove-section .comment \
21644 --keep-symbols=keep_symbols debug mini_debuginfo
21646 # Drop the full debug info from the original binary.
21647 strip --strip-all -R .comment @var{binary}
21649 # Inject the compressed data into the .gnu_debugdata section of the
21652 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21656 @section Index Files Speed Up @value{GDBN}
21657 @cindex index files
21658 @cindex @samp{.gdb_index} section
21660 When @value{GDBN} finds a symbol file, it scans the symbols in the
21661 file in order to construct an internal symbol table. This lets most
21662 @value{GDBN} operations work quickly---at the cost of a delay early
21663 on. For large programs, this delay can be quite lengthy, so
21664 @value{GDBN} provides a way to build an index, which speeds up
21667 For convenience, @value{GDBN} comes with a program,
21668 @command{gdb-add-index}, which can be used to add the index to a
21669 symbol file. It takes the symbol file as its only argument:
21672 $ gdb-add-index symfile
21675 @xref{gdb-add-index}.
21677 It is also possible to do the work manually. Here is what
21678 @command{gdb-add-index} does behind the curtains.
21680 The index is stored as a section in the symbol file. @value{GDBN} can
21681 write the index to a file, then you can put it into the symbol file
21682 using @command{objcopy}.
21684 To create an index file, use the @code{save gdb-index} command:
21687 @item save gdb-index [-dwarf-5] @var{directory}
21688 @kindex save gdb-index
21689 Create index files for all symbol files currently known by
21690 @value{GDBN}. For each known @var{symbol-file}, this command by
21691 default creates it produces a single file
21692 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21693 the @option{-dwarf-5} option, it produces 2 files:
21694 @file{@var{symbol-file}.debug_names} and
21695 @file{@var{symbol-file}.debug_str}. The files are created in the
21696 given @var{directory}.
21699 Once you have created an index file you can merge it into your symbol
21700 file, here named @file{symfile}, using @command{objcopy}:
21703 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21704 --set-section-flags .gdb_index=readonly symfile symfile
21707 Or for @code{-dwarf-5}:
21710 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21711 $ cat symfile.debug_str >>symfile.debug_str.new
21712 $ objcopy --add-section .debug_names=symfile.gdb-index \
21713 --set-section-flags .debug_names=readonly \
21714 --update-section .debug_str=symfile.debug_str.new symfile symfile
21717 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21718 sections that have been deprecated. Usually they are deprecated because
21719 they are missing a new feature or have performance issues.
21720 To tell @value{GDBN} to use a deprecated index section anyway
21721 specify @code{set use-deprecated-index-sections on}.
21722 The default is @code{off}.
21723 This can speed up startup, but may result in some functionality being lost.
21724 @xref{Index Section Format}.
21726 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21727 must be done before gdb reads the file. The following will not work:
21730 $ gdb -ex "set use-deprecated-index-sections on" <program>
21733 Instead you must do, for example,
21736 $ gdb -iex "set use-deprecated-index-sections on" <program>
21739 Indices only work when using DWARF debugging information, not stabs.
21741 @subsection Automatic symbol index cache
21743 @cindex automatic symbol index cache
21744 It is possible for @value{GDBN} to automatically save a copy of this index in a
21745 cache on disk and retrieve it from there when loading the same binary in the
21746 future. This feature can be turned on with @kbd{set index-cache on}. The
21747 following commands can be used to tweak the behavior of the index cache.
21751 @kindex set index-cache
21752 @item set index-cache on
21753 @itemx set index-cache off
21754 Enable or disable the use of the symbol index cache.
21756 @item set index-cache directory @var{directory}
21757 @kindex show index-cache
21758 @itemx show index-cache directory
21759 Set/show the directory where index files will be saved.
21761 The default value for this directory depends on the host platform. On
21762 most systems, the index is cached in the @file{gdb} subdirectory of
21763 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21764 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21765 of your home directory. However, on some systems, the default may
21766 differ according to local convention.
21768 There is no limit on the disk space used by index cache. It is perfectly safe
21769 to delete the content of that directory to free up disk space.
21771 @item show index-cache stats
21772 Print the number of cache hits and misses since the launch of @value{GDBN}.
21776 @node Symbol Errors
21777 @section Errors Reading Symbol Files
21779 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21780 such as symbol types it does not recognize, or known bugs in compiler
21781 output. By default, @value{GDBN} does not notify you of such problems, since
21782 they are relatively common and primarily of interest to people
21783 debugging compilers. If you are interested in seeing information
21784 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21785 only one message about each such type of problem, no matter how many
21786 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21787 to see how many times the problems occur, with the @code{set
21788 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21791 The messages currently printed, and their meanings, include:
21794 @item inner block not inside outer block in @var{symbol}
21796 The symbol information shows where symbol scopes begin and end
21797 (such as at the start of a function or a block of statements). This
21798 error indicates that an inner scope block is not fully contained
21799 in its outer scope blocks.
21801 @value{GDBN} circumvents the problem by treating the inner block as if it had
21802 the same scope as the outer block. In the error message, @var{symbol}
21803 may be shown as ``@code{(don't know)}'' if the outer block is not a
21806 @item block at @var{address} out of order
21808 The symbol information for symbol scope blocks should occur in
21809 order of increasing addresses. This error indicates that it does not
21812 @value{GDBN} does not circumvent this problem, and has trouble
21813 locating symbols in the source file whose symbols it is reading. (You
21814 can often determine what source file is affected by specifying
21815 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21818 @item bad block start address patched
21820 The symbol information for a symbol scope block has a start address
21821 smaller than the address of the preceding source line. This is known
21822 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21824 @value{GDBN} circumvents the problem by treating the symbol scope block as
21825 starting on the previous source line.
21827 @item bad string table offset in symbol @var{n}
21830 Symbol number @var{n} contains a pointer into the string table which is
21831 larger than the size of the string table.
21833 @value{GDBN} circumvents the problem by considering the symbol to have the
21834 name @code{foo}, which may cause other problems if many symbols end up
21837 @item unknown symbol type @code{0x@var{nn}}
21839 The symbol information contains new data types that @value{GDBN} does
21840 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21841 uncomprehended information, in hexadecimal.
21843 @value{GDBN} circumvents the error by ignoring this symbol information.
21844 This usually allows you to debug your program, though certain symbols
21845 are not accessible. If you encounter such a problem and feel like
21846 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21847 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21848 and examine @code{*bufp} to see the symbol.
21850 @item stub type has NULL name
21852 @value{GDBN} could not find the full definition for a struct or class.
21854 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21855 The symbol information for a C@t{++} member function is missing some
21856 information that recent versions of the compiler should have output for
21859 @item info mismatch between compiler and debugger
21861 @value{GDBN} could not parse a type specification output by the compiler.
21866 @section GDB Data Files
21868 @cindex prefix for data files
21869 @value{GDBN} will sometimes read an auxiliary data file. These files
21870 are kept in a directory known as the @dfn{data directory}.
21872 You can set the data directory's name, and view the name @value{GDBN}
21873 is currently using.
21876 @kindex set data-directory
21877 @item set data-directory @var{directory}
21878 Set the directory which @value{GDBN} searches for auxiliary data files
21879 to @var{directory}.
21881 @kindex show data-directory
21882 @item show data-directory
21883 Show the directory @value{GDBN} searches for auxiliary data files.
21886 @cindex default data directory
21887 @cindex @samp{--with-gdb-datadir}
21888 You can set the default data directory by using the configure-time
21889 @samp{--with-gdb-datadir} option. If the data directory is inside
21890 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21891 @samp{--exec-prefix}), then the default data directory will be updated
21892 automatically if the installed @value{GDBN} is moved to a new
21895 The data directory may also be specified with the
21896 @code{--data-directory} command line option.
21897 @xref{Mode Options}.
21900 @chapter Specifying a Debugging Target
21902 @cindex debugging target
21903 A @dfn{target} is the execution environment occupied by your program.
21905 Often, @value{GDBN} runs in the same host environment as your program;
21906 in that case, the debugging target is specified as a side effect when
21907 you use the @code{file} or @code{core} commands. When you need more
21908 flexibility---for example, running @value{GDBN} on a physically separate
21909 host, or controlling a standalone system over a serial port or a
21910 realtime system over a TCP/IP connection---you can use the @code{target}
21911 command to specify one of the target types configured for @value{GDBN}
21912 (@pxref{Target Commands, ,Commands for Managing Targets}).
21914 @cindex target architecture
21915 It is possible to build @value{GDBN} for several different @dfn{target
21916 architectures}. When @value{GDBN} is built like that, you can choose
21917 one of the available architectures with the @kbd{set architecture}
21921 @kindex set architecture
21922 @kindex show architecture
21923 @item set architecture @var{arch}
21924 This command sets the current target architecture to @var{arch}. The
21925 value of @var{arch} can be @code{"auto"}, in addition to one of the
21926 supported architectures.
21928 @item show architecture
21929 Show the current target architecture.
21931 @item set processor
21933 @kindex set processor
21934 @kindex show processor
21935 These are alias commands for, respectively, @code{set architecture}
21936 and @code{show architecture}.
21940 * Active Targets:: Active targets
21941 * Target Commands:: Commands for managing targets
21942 * Byte Order:: Choosing target byte order
21945 @node Active Targets
21946 @section Active Targets
21948 @cindex stacking targets
21949 @cindex active targets
21950 @cindex multiple targets
21952 There are multiple classes of targets such as: processes, executable files or
21953 recording sessions. Core files belong to the process class, making core file
21954 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21955 on multiple active targets, one in each class. This allows you to (for
21956 example) start a process and inspect its activity, while still having access to
21957 the executable file after the process finishes. Or if you start process
21958 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21959 presented a virtual layer of the recording target, while the process target
21960 remains stopped at the chronologically last point of the process execution.
21962 Use the @code{core-file} and @code{exec-file} commands to select a new core
21963 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21964 specify as a target a process that is already running, use the @code{attach}
21965 command (@pxref{Attach, ,Debugging an Already-running Process}).
21967 @node Target Commands
21968 @section Commands for Managing Targets
21971 @item target @var{type} @var{parameters}
21972 Connects the @value{GDBN} host environment to a target machine or
21973 process. A target is typically a protocol for talking to debugging
21974 facilities. You use the argument @var{type} to specify the type or
21975 protocol of the target machine.
21977 Further @var{parameters} are interpreted by the target protocol, but
21978 typically include things like device names or host names to connect
21979 with, process numbers, and baud rates.
21981 The @code{target} command does not repeat if you press @key{RET} again
21982 after executing the command.
21984 @kindex help target
21986 Displays the names of all targets available. To display targets
21987 currently selected, use either @code{info target} or @code{info files}
21988 (@pxref{Files, ,Commands to Specify Files}).
21990 @item help target @var{name}
21991 Describe a particular target, including any parameters necessary to
21994 @kindex set gnutarget
21995 @item set gnutarget @var{args}
21996 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21997 knows whether it is reading an @dfn{executable},
21998 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21999 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22000 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22003 @emph{Warning:} To specify a file format with @code{set gnutarget},
22004 you must know the actual BFD name.
22008 @xref{Files, , Commands to Specify Files}.
22010 @kindex show gnutarget
22011 @item show gnutarget
22012 Use the @code{show gnutarget} command to display what file format
22013 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22014 @value{GDBN} will determine the file format for each file automatically,
22015 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22018 @cindex common targets
22019 Here are some common targets (available, or not, depending on the GDB
22024 @item target exec @var{program}
22025 @cindex executable file target
22026 An executable file. @samp{target exec @var{program}} is the same as
22027 @samp{exec-file @var{program}}.
22029 @item target core @var{filename}
22030 @cindex core dump file target
22031 A core dump file. @samp{target core @var{filename}} is the same as
22032 @samp{core-file @var{filename}}.
22034 @item target remote @var{medium}
22035 @cindex remote target
22036 A remote system connected to @value{GDBN} via a serial line or network
22037 connection. This command tells @value{GDBN} to use its own remote
22038 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22040 For example, if you have a board connected to @file{/dev/ttya} on the
22041 machine running @value{GDBN}, you could say:
22044 target remote /dev/ttya
22047 @code{target remote} supports the @code{load} command. This is only
22048 useful if you have some other way of getting the stub to the target
22049 system, and you can put it somewhere in memory where it won't get
22050 clobbered by the download.
22052 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22053 @cindex built-in simulator target
22054 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22062 works; however, you cannot assume that a specific memory map, device
22063 drivers, or even basic I/O is available, although some simulators do
22064 provide these. For info about any processor-specific simulator details,
22065 see the appropriate section in @ref{Embedded Processors, ,Embedded
22068 @item target native
22069 @cindex native target
22070 Setup for local/native process debugging. Useful to make the
22071 @code{run} command spawn native processes (likewise @code{attach},
22072 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22073 (@pxref{set auto-connect-native-target}).
22077 Different targets are available on different configurations of @value{GDBN};
22078 your configuration may have more or fewer targets.
22080 Many remote targets require you to download the executable's code once
22081 you've successfully established a connection. You may wish to control
22082 various aspects of this process.
22087 @kindex set hash@r{, for remote monitors}
22088 @cindex hash mark while downloading
22089 This command controls whether a hash mark @samp{#} is displayed while
22090 downloading a file to the remote monitor. If on, a hash mark is
22091 displayed after each S-record is successfully downloaded to the
22095 @kindex show hash@r{, for remote monitors}
22096 Show the current status of displaying the hash mark.
22098 @item set debug monitor
22099 @kindex set debug monitor
22100 @cindex display remote monitor communications
22101 Enable or disable display of communications messages between
22102 @value{GDBN} and the remote monitor.
22104 @item show debug monitor
22105 @kindex show debug monitor
22106 Show the current status of displaying communications between
22107 @value{GDBN} and the remote monitor.
22112 @kindex load @var{filename} @var{offset}
22113 @item load @var{filename} @var{offset}
22115 Depending on what remote debugging facilities are configured into
22116 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22117 is meant to make @var{filename} (an executable) available for debugging
22118 on the remote system---by downloading, or dynamic linking, for example.
22119 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22120 the @code{add-symbol-file} command.
22122 If your @value{GDBN} does not have a @code{load} command, attempting to
22123 execute it gets the error message ``@code{You can't do that when your
22124 target is @dots{}}''
22126 The file is loaded at whatever address is specified in the executable.
22127 For some object file formats, you can specify the load address when you
22128 link the program; for other formats, like a.out, the object file format
22129 specifies a fixed address.
22130 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22132 It is also possible to tell @value{GDBN} to load the executable file at a
22133 specific offset described by the optional argument @var{offset}. When
22134 @var{offset} is provided, @var{filename} must also be provided.
22136 Depending on the remote side capabilities, @value{GDBN} may be able to
22137 load programs into flash memory.
22139 @code{load} does not repeat if you press @key{RET} again after using it.
22144 @kindex flash-erase
22146 @anchor{flash-erase}
22148 Erases all known flash memory regions on the target.
22153 @section Choosing Target Byte Order
22155 @cindex choosing target byte order
22156 @cindex target byte order
22158 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22159 offer the ability to run either big-endian or little-endian byte
22160 orders. Usually the executable or symbol will include a bit to
22161 designate the endian-ness, and you will not need to worry about
22162 which to use. However, you may still find it useful to adjust
22163 @value{GDBN}'s idea of processor endian-ness manually.
22167 @item set endian big
22168 Instruct @value{GDBN} to assume the target is big-endian.
22170 @item set endian little
22171 Instruct @value{GDBN} to assume the target is little-endian.
22173 @item set endian auto
22174 Instruct @value{GDBN} to use the byte order associated with the
22178 Display @value{GDBN}'s current idea of the target byte order.
22182 If the @code{set endian auto} mode is in effect and no executable has
22183 been selected, then the endianness used is the last one chosen either
22184 by one of the @code{set endian big} and @code{set endian little}
22185 commands or by inferring from the last executable used. If no
22186 endianness has been previously chosen, then the default for this mode
22187 is inferred from the target @value{GDBN} has been built for, and is
22188 @code{little} if the name of the target CPU has an @code{el} suffix
22189 and @code{big} otherwise.
22191 Note that these commands merely adjust interpretation of symbolic
22192 data on the host, and that they have absolutely no effect on the
22196 @node Remote Debugging
22197 @chapter Debugging Remote Programs
22198 @cindex remote debugging
22200 If you are trying to debug a program running on a machine that cannot run
22201 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22202 For example, you might use remote debugging on an operating system kernel,
22203 or on a small system which does not have a general purpose operating system
22204 powerful enough to run a full-featured debugger.
22206 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22207 to make this work with particular debugging targets. In addition,
22208 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22209 but not specific to any particular target system) which you can use if you
22210 write the remote stubs---the code that runs on the remote system to
22211 communicate with @value{GDBN}.
22213 Other remote targets may be available in your
22214 configuration of @value{GDBN}; use @code{help target} to list them.
22217 * Connecting:: Connecting to a remote target
22218 * File Transfer:: Sending files to a remote system
22219 * Server:: Using the gdbserver program
22220 * Remote Configuration:: Remote configuration
22221 * Remote Stub:: Implementing a remote stub
22225 @section Connecting to a Remote Target
22226 @cindex remote debugging, connecting
22227 @cindex @code{gdbserver}, connecting
22228 @cindex remote debugging, types of connections
22229 @cindex @code{gdbserver}, types of connections
22230 @cindex @code{gdbserver}, @code{target remote} mode
22231 @cindex @code{gdbserver}, @code{target extended-remote} mode
22233 This section describes how to connect to a remote target, including the
22234 types of connections and their differences, how to set up executable and
22235 symbol files on the host and target, and the commands used for
22236 connecting to and disconnecting from the remote target.
22238 @subsection Types of Remote Connections
22240 @value{GDBN} supports two types of remote connections, @code{target remote}
22241 mode and @code{target extended-remote} mode. Note that many remote targets
22242 support only @code{target remote} mode. There are several major
22243 differences between the two types of connections, enumerated here:
22247 @cindex remote debugging, detach and program exit
22248 @item Result of detach or program exit
22249 @strong{With target remote mode:} When the debugged program exits or you
22250 detach from it, @value{GDBN} disconnects from the target. When using
22251 @code{gdbserver}, @code{gdbserver} will exit.
22253 @strong{With target extended-remote mode:} When the debugged program exits or
22254 you detach from it, @value{GDBN} remains connected to the target, even
22255 though no program is running. You can rerun the program, attach to a
22256 running program, or use @code{monitor} commands specific to the target.
22258 When using @code{gdbserver} in this case, it does not exit unless it was
22259 invoked using the @option{--once} option. If the @option{--once} option
22260 was not used, you can ask @code{gdbserver} to exit using the
22261 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22263 @item Specifying the program to debug
22264 For both connection types you use the @code{file} command to specify the
22265 program on the host system. If you are using @code{gdbserver} there are
22266 some differences in how to specify the location of the program on the
22269 @strong{With target remote mode:} You must either specify the program to debug
22270 on the @code{gdbserver} command line or use the @option{--attach} option
22271 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22273 @cindex @option{--multi}, @code{gdbserver} option
22274 @strong{With target extended-remote mode:} You may specify the program to debug
22275 on the @code{gdbserver} command line, or you can load the program or attach
22276 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22278 @anchor{--multi Option in Types of Remote Connnections}
22279 You can start @code{gdbserver} without supplying an initial command to run
22280 or process ID to attach. To do this, use the @option{--multi} command line
22281 option. Then you can connect using @code{target extended-remote} and start
22282 the program you want to debug (see below for details on using the
22283 @code{run} command in this scenario). Note that the conditions under which
22284 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22285 (@code{target remote} or @code{target extended-remote}). The
22286 @option{--multi} option to @code{gdbserver} has no influence on that.
22288 @item The @code{run} command
22289 @strong{With target remote mode:} The @code{run} command is not
22290 supported. Once a connection has been established, you can use all
22291 the usual @value{GDBN} commands to examine and change data. The
22292 remote program is already running, so you can use commands like
22293 @kbd{step} and @kbd{continue}.
22295 @strong{With target extended-remote mode:} The @code{run} command is
22296 supported. The @code{run} command uses the value set by
22297 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22298 the program to run. Command line arguments are supported, except for
22299 wildcard expansion and I/O redirection (@pxref{Arguments}).
22301 If you specify the program to debug on the command line, then the
22302 @code{run} command is not required to start execution, and you can
22303 resume using commands like @kbd{step} and @kbd{continue} as with
22304 @code{target remote} mode.
22306 @anchor{Attaching in Types of Remote Connections}
22308 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22309 not supported. To attach to a running program using @code{gdbserver}, you
22310 must use the @option{--attach} option (@pxref{Running gdbserver}).
22312 @strong{With target extended-remote mode:} To attach to a running program,
22313 you may use the @code{attach} command after the connection has been
22314 established. If you are using @code{gdbserver}, you may also invoke
22315 @code{gdbserver} using the @option{--attach} option
22316 (@pxref{Running gdbserver}).
22318 Some remote targets allow @value{GDBN} to determine the executable file running
22319 in the process the debugger is attaching to. In such a case, @value{GDBN}
22320 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22321 between the executable file name running in the process and the name of the
22322 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22326 @anchor{Host and target files}
22327 @subsection Host and Target Files
22328 @cindex remote debugging, symbol files
22329 @cindex symbol files, remote debugging
22331 @value{GDBN}, running on the host, needs access to symbol and debugging
22332 information for your program running on the target. This requires
22333 access to an unstripped copy of your program, and possibly any associated
22334 symbol files. Note that this section applies equally to both @code{target
22335 remote} mode and @code{target extended-remote} mode.
22337 Some remote targets (@pxref{qXfer executable filename read}, and
22338 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22339 the same connection used to communicate with @value{GDBN}. With such a
22340 target, if the remote program is unstripped, the only command you need is
22341 @code{target remote} (or @code{target extended-remote}).
22343 If the remote program is stripped, or the target does not support remote
22344 program file access, start up @value{GDBN} using the name of the local
22345 unstripped copy of your program as the first argument, or use the
22346 @code{file} command. Use @code{set sysroot} to specify the location (on
22347 the host) of target libraries (unless your @value{GDBN} was compiled with
22348 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22349 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22352 The symbol file and target libraries must exactly match the executable
22353 and libraries on the target, with one exception: the files on the host
22354 system should not be stripped, even if the files on the target system
22355 are. Mismatched or missing files will lead to confusing results
22356 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22357 files may also prevent @code{gdbserver} from debugging multi-threaded
22360 @subsection Remote Connection Commands
22361 @cindex remote connection commands
22362 @value{GDBN} can communicate with the target over a serial line, a
22363 local Unix domain socket, or
22364 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22365 each case, @value{GDBN} uses the same protocol for debugging your
22366 program; only the medium carrying the debugging packets varies. The
22367 @code{target remote} and @code{target extended-remote} commands
22368 establish a connection to the target. Both commands accept the same
22369 arguments, which indicate the medium to use:
22373 @item target remote @var{serial-device}
22374 @itemx target extended-remote @var{serial-device}
22375 @cindex serial line, @code{target remote}
22376 Use @var{serial-device} to communicate with the target. For example,
22377 to use a serial line connected to the device named @file{/dev/ttyb}:
22380 target remote /dev/ttyb
22383 If you're using a serial line, you may want to give @value{GDBN} the
22384 @samp{--baud} option, or use the @code{set serial baud} command
22385 (@pxref{Remote Configuration, set serial baud}) before the
22386 @code{target} command.
22388 @item target remote @var{local-socket}
22389 @itemx target extended-remote @var{local-socket}
22390 @cindex local socket, @code{target remote}
22391 @cindex Unix domain socket
22392 Use @var{local-socket} to communicate with the target. For example,
22393 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22396 target remote /tmp/gdb-socket0
22399 Note that this command has the same form as the command to connect
22400 to a serial line. @value{GDBN} will automatically determine which
22401 kind of file you have specified and will make the appropriate kind
22403 This feature is not available if the host system does not support
22404 Unix domain sockets.
22406 @item target remote @code{@var{host}:@var{port}}
22407 @itemx target remote @code{[@var{host}]:@var{port}}
22408 @itemx target remote @code{tcp:@var{host}:@var{port}}
22409 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22410 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22411 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22412 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22413 @itemx target extended-remote @code{@var{host}:@var{port}}
22414 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22415 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22416 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22417 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22418 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22419 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22420 @cindex @acronym{TCP} port, @code{target remote}
22421 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22422 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22423 address, or a numeric @acronym{IPv6} address (with or without the
22424 square brackets to separate the address from the port); @var{port}
22425 must be a decimal number. The @var{host} could be the target machine
22426 itself, if it is directly connected to the net, or it might be a
22427 terminal server which in turn has a serial line to the target.
22429 For example, to connect to port 2828 on a terminal server named
22433 target remote manyfarms:2828
22436 To connect to port 2828 on a terminal server whose address is
22437 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22438 square bracket syntax:
22441 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22445 or explicitly specify the @acronym{IPv6} protocol:
22448 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22451 This last example may be confusing to the reader, because there is no
22452 visible separation between the hostname and the port number.
22453 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22454 using square brackets for clarity. However, it is important to
22455 mention that for @value{GDBN} there is no ambiguity: the number after
22456 the last colon is considered to be the port number.
22458 If your remote target is actually running on the same machine as your
22459 debugger session (e.g.@: a simulator for your target running on the
22460 same host), you can omit the hostname. For example, to connect to
22461 port 1234 on your local machine:
22464 target remote :1234
22468 Note that the colon is still required here.
22470 @item target remote @code{udp:@var{host}:@var{port}}
22471 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22472 @itemx target remote @code{udp4:@var{host}:@var{port}}
22473 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22474 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22475 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22476 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22477 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22478 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22479 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22480 @cindex @acronym{UDP} port, @code{target remote}
22481 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22482 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22485 target remote udp:manyfarms:2828
22488 When using a @acronym{UDP} connection for remote debugging, you should
22489 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22490 can silently drop packets on busy or unreliable networks, which will
22491 cause havoc with your debugging session.
22493 @item target remote | @var{command}
22494 @itemx target extended-remote | @var{command}
22495 @cindex pipe, @code{target remote} to
22496 Run @var{command} in the background and communicate with it using a
22497 pipe. The @var{command} is a shell command, to be parsed and expanded
22498 by the system's command shell, @code{/bin/sh}; it should expect remote
22499 protocol packets on its standard input, and send replies on its
22500 standard output. You could use this to run a stand-alone simulator
22501 that speaks the remote debugging protocol, to make net connections
22502 using programs like @code{ssh}, or for other similar tricks.
22504 If @var{command} closes its standard output (perhaps by exiting),
22505 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22506 program has already exited, this will have no effect.)
22510 @cindex interrupting remote programs
22511 @cindex remote programs, interrupting
22512 Whenever @value{GDBN} is waiting for the remote program, if you type the
22513 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22514 program. This may or may not succeed, depending in part on the hardware
22515 and the serial drivers the remote system uses. If you type the
22516 interrupt character once again, @value{GDBN} displays this prompt:
22519 Interrupted while waiting for the program.
22520 Give up (and stop debugging it)? (y or n)
22523 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22524 the remote debugging session. (If you decide you want to try again later,
22525 you can use @kbd{target remote} again to connect once more.) If you type
22526 @kbd{n}, @value{GDBN} goes back to waiting.
22528 In @code{target extended-remote} mode, typing @kbd{n} will leave
22529 @value{GDBN} connected to the target.
22532 @kindex detach (remote)
22534 When you have finished debugging the remote program, you can use the
22535 @code{detach} command to release it from @value{GDBN} control.
22536 Detaching from the target normally resumes its execution, but the results
22537 will depend on your particular remote stub. After the @code{detach}
22538 command in @code{target remote} mode, @value{GDBN} is free to connect to
22539 another target. In @code{target extended-remote} mode, @value{GDBN} is
22540 still connected to the target.
22544 The @code{disconnect} command closes the connection to the target, and
22545 the target is generally not resumed. It will wait for @value{GDBN}
22546 (this instance or another one) to connect and continue debugging. After
22547 the @code{disconnect} command, @value{GDBN} is again free to connect to
22550 @cindex send command to remote monitor
22551 @cindex extend @value{GDBN} for remote targets
22552 @cindex add new commands for external monitor
22554 @item monitor @var{cmd}
22555 This command allows you to send arbitrary commands directly to the
22556 remote monitor. Since @value{GDBN} doesn't care about the commands it
22557 sends like this, this command is the way to extend @value{GDBN}---you
22558 can add new commands that only the external monitor will understand
22562 @node File Transfer
22563 @section Sending files to a remote system
22564 @cindex remote target, file transfer
22565 @cindex file transfer
22566 @cindex sending files to remote systems
22568 Some remote targets offer the ability to transfer files over the same
22569 connection used to communicate with @value{GDBN}. This is convenient
22570 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22571 running @code{gdbserver} over a network interface. For other targets,
22572 e.g.@: embedded devices with only a single serial port, this may be
22573 the only way to upload or download files.
22575 Not all remote targets support these commands.
22579 @item remote put @var{hostfile} @var{targetfile}
22580 Copy file @var{hostfile} from the host system (the machine running
22581 @value{GDBN}) to @var{targetfile} on the target system.
22584 @item remote get @var{targetfile} @var{hostfile}
22585 Copy file @var{targetfile} from the target system to @var{hostfile}
22586 on the host system.
22588 @kindex remote delete
22589 @item remote delete @var{targetfile}
22590 Delete @var{targetfile} from the target system.
22595 @section Using the @code{gdbserver} Program
22598 @cindex remote connection without stubs
22599 @code{gdbserver} is a control program for Unix-like systems, which
22600 allows you to connect your program with a remote @value{GDBN} via
22601 @code{target remote} or @code{target extended-remote}---but without
22602 linking in the usual debugging stub.
22604 @code{gdbserver} is not a complete replacement for the debugging stubs,
22605 because it requires essentially the same operating-system facilities
22606 that @value{GDBN} itself does. In fact, a system that can run
22607 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22608 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22609 because it is a much smaller program than @value{GDBN} itself. It is
22610 also easier to port than all of @value{GDBN}, so you may be able to get
22611 started more quickly on a new system by using @code{gdbserver}.
22612 Finally, if you develop code for real-time systems, you may find that
22613 the tradeoffs involved in real-time operation make it more convenient to
22614 do as much development work as possible on another system, for example
22615 by cross-compiling. You can use @code{gdbserver} to make a similar
22616 choice for debugging.
22618 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22619 or a TCP connection, using the standard @value{GDBN} remote serial
22623 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22624 Do not run @code{gdbserver} connected to any public network; a
22625 @value{GDBN} connection to @code{gdbserver} provides access to the
22626 target system with the same privileges as the user running
22630 @anchor{Running gdbserver}
22631 @subsection Running @code{gdbserver}
22632 @cindex arguments, to @code{gdbserver}
22633 @cindex @code{gdbserver}, command-line arguments
22635 Run @code{gdbserver} on the target system. You need a copy of the
22636 program you want to debug, including any libraries it requires.
22637 @code{gdbserver} does not need your program's symbol table, so you can
22638 strip the program if necessary to save space. @value{GDBN} on the host
22639 system does all the symbol handling.
22641 To use the server, you must tell it how to communicate with @value{GDBN};
22642 the name of your program; and the arguments for your program. The usual
22646 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22649 @var{comm} is either a device name (to use a serial line), or a TCP
22650 hostname and portnumber, or @code{-} or @code{stdio} to use
22651 stdin/stdout of @code{gdbserver}.
22652 For example, to debug Emacs with the argument
22653 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22657 target> gdbserver /dev/com1 emacs foo.txt
22660 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22663 To use a TCP connection instead of a serial line:
22666 target> gdbserver host:2345 emacs foo.txt
22669 The only difference from the previous example is the first argument,
22670 specifying that you are communicating with the host @value{GDBN} via
22671 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22672 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22673 (Currently, the @samp{host} part is ignored.) You can choose any number
22674 you want for the port number as long as it does not conflict with any
22675 TCP ports already in use on the target system (for example, @code{23} is
22676 reserved for @code{telnet}).@footnote{If you choose a port number that
22677 conflicts with another service, @code{gdbserver} prints an error message
22678 and exits.} You must use the same port number with the host @value{GDBN}
22679 @code{target remote} command.
22681 The @code{stdio} connection is useful when starting @code{gdbserver}
22685 (gdb) target remote | ssh -T hostname gdbserver - hello
22688 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22689 and we don't want escape-character handling. Ssh does this by default when
22690 a command is provided, the flag is provided to make it explicit.
22691 You could elide it if you want to.
22693 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22694 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22695 display through a pipe connected to gdbserver.
22696 Both @code{stdout} and @code{stderr} use the same pipe.
22698 @anchor{Attaching to a program}
22699 @subsubsection Attaching to a Running Program
22700 @cindex attach to a program, @code{gdbserver}
22701 @cindex @option{--attach}, @code{gdbserver} option
22703 On some targets, @code{gdbserver} can also attach to running programs.
22704 This is accomplished via the @code{--attach} argument. The syntax is:
22707 target> gdbserver --attach @var{comm} @var{pid}
22710 @var{pid} is the process ID of a currently running process. It isn't
22711 necessary to point @code{gdbserver} at a binary for the running process.
22713 In @code{target extended-remote} mode, you can also attach using the
22714 @value{GDBN} attach command
22715 (@pxref{Attaching in Types of Remote Connections}).
22718 You can debug processes by name instead of process ID if your target has the
22719 @code{pidof} utility:
22722 target> gdbserver --attach @var{comm} `pidof @var{program}`
22725 In case more than one copy of @var{program} is running, or @var{program}
22726 has multiple threads, most versions of @code{pidof} support the
22727 @code{-s} option to only return the first process ID.
22729 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22731 This section applies only when @code{gdbserver} is run to listen on a TCP
22734 @code{gdbserver} normally terminates after all of its debugged processes have
22735 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22736 extended-remote}, @code{gdbserver} stays running even with no processes left.
22737 @value{GDBN} normally terminates the spawned debugged process on its exit,
22738 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22739 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22740 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22741 stays running even in the @kbd{target remote} mode.
22743 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22744 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22745 completeness, at most one @value{GDBN} can be connected at a time.
22747 @cindex @option{--once}, @code{gdbserver} option
22748 By default, @code{gdbserver} keeps the listening TCP port open, so that
22749 subsequent connections are possible. However, if you start @code{gdbserver}
22750 with the @option{--once} option, it will stop listening for any further
22751 connection attempts after connecting to the first @value{GDBN} session. This
22752 means no further connections to @code{gdbserver} will be possible after the
22753 first one. It also means @code{gdbserver} will terminate after the first
22754 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22755 connections and even in the @kbd{target extended-remote} mode. The
22756 @option{--once} option allows reusing the same port number for connecting to
22757 multiple instances of @code{gdbserver} running on the same host, since each
22758 instance closes its port after the first connection.
22760 @anchor{Other Command-Line Arguments for gdbserver}
22761 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22763 You can use the @option{--multi} option to start @code{gdbserver} without
22764 specifying a program to debug or a process to attach to. Then you can
22765 attach in @code{target extended-remote} mode and run or attach to a
22766 program. For more information,
22767 @pxref{--multi Option in Types of Remote Connnections}.
22769 @cindex @option{--debug}, @code{gdbserver} option
22770 The @option{--debug} option tells @code{gdbserver} to display extra
22771 status information about the debugging process.
22772 @cindex @option{--remote-debug}, @code{gdbserver} option
22773 The @option{--remote-debug} option tells @code{gdbserver} to display
22774 remote protocol debug output.
22775 @cindex @option{--debug-file}, @code{gdbserver} option
22776 @cindex @code{gdbserver}, send all debug output to a single file
22777 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22778 write any debug output to the given @var{filename}. These options are intended
22779 for @code{gdbserver} development and for bug reports to the developers.
22781 @cindex @option{--debug-format}, @code{gdbserver} option
22782 The @option{--debug-format=option1[,option2,...]} option tells
22783 @code{gdbserver} to include additional information in each output.
22784 Possible options are:
22788 Turn off all extra information in debugging output.
22790 Turn on all extra information in debugging output.
22792 Include a timestamp in each line of debugging output.
22795 Options are processed in order. Thus, for example, if @option{none}
22796 appears last then no additional information is added to debugging output.
22798 @cindex @option{--wrapper}, @code{gdbserver} option
22799 The @option{--wrapper} option specifies a wrapper to launch programs
22800 for debugging. The option should be followed by the name of the
22801 wrapper, then any command-line arguments to pass to the wrapper, then
22802 @kbd{--} indicating the end of the wrapper arguments.
22804 @code{gdbserver} runs the specified wrapper program with a combined
22805 command line including the wrapper arguments, then the name of the
22806 program to debug, then any arguments to the program. The wrapper
22807 runs until it executes your program, and then @value{GDBN} gains control.
22809 You can use any program that eventually calls @code{execve} with
22810 its arguments as a wrapper. Several standard Unix utilities do
22811 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22812 with @code{exec "$@@"} will also work.
22814 For example, you can use @code{env} to pass an environment variable to
22815 the debugged program, without setting the variable in @code{gdbserver}'s
22819 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22822 @cindex @option{--selftest}
22823 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22826 $ gdbserver --selftest
22827 Ran 2 unit tests, 0 failed
22830 These tests are disabled in release.
22831 @subsection Connecting to @code{gdbserver}
22833 The basic procedure for connecting to the remote target is:
22837 Run @value{GDBN} on the host system.
22840 Make sure you have the necessary symbol files
22841 (@pxref{Host and target files}).
22842 Load symbols for your application using the @code{file} command before you
22843 connect. Use @code{set sysroot} to locate target libraries (unless your
22844 @value{GDBN} was compiled with the correct sysroot using
22845 @code{--with-sysroot}).
22848 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22849 For TCP connections, you must start up @code{gdbserver} prior to using
22850 the @code{target} command. Otherwise you may get an error whose
22851 text depends on the host system, but which usually looks something like
22852 @samp{Connection refused}. Don't use the @code{load}
22853 command in @value{GDBN} when using @code{target remote} mode, since the
22854 program is already on the target.
22858 @anchor{Monitor Commands for gdbserver}
22859 @subsection Monitor Commands for @code{gdbserver}
22860 @cindex monitor commands, for @code{gdbserver}
22862 During a @value{GDBN} session using @code{gdbserver}, you can use the
22863 @code{monitor} command to send special requests to @code{gdbserver}.
22864 Here are the available commands.
22868 List the available monitor commands.
22870 @item monitor set debug 0
22871 @itemx monitor set debug 1
22872 Disable or enable general debugging messages.
22874 @item monitor set remote-debug 0
22875 @itemx monitor set remote-debug 1
22876 Disable or enable specific debugging messages associated with the remote
22877 protocol (@pxref{Remote Protocol}).
22879 @item monitor set debug-file filename
22880 @itemx monitor set debug-file
22881 Send any debug output to the given file, or to stderr.
22883 @item monitor set debug-format option1@r{[},option2,...@r{]}
22884 Specify additional text to add to debugging messages.
22885 Possible options are:
22889 Turn off all extra information in debugging output.
22891 Turn on all extra information in debugging output.
22893 Include a timestamp in each line of debugging output.
22896 Options are processed in order. Thus, for example, if @option{none}
22897 appears last then no additional information is added to debugging output.
22899 @item monitor set libthread-db-search-path [PATH]
22900 @cindex gdbserver, search path for @code{libthread_db}
22901 When this command is issued, @var{path} is a colon-separated list of
22902 directories to search for @code{libthread_db} (@pxref{Threads,,set
22903 libthread-db-search-path}). If you omit @var{path},
22904 @samp{libthread-db-search-path} will be reset to its default value.
22906 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22907 not supported in @code{gdbserver}.
22910 Tell gdbserver to exit immediately. This command should be followed by
22911 @code{disconnect} to close the debugging session. @code{gdbserver} will
22912 detach from any attached processes and kill any processes it created.
22913 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22914 of a multi-process mode debug session.
22918 @subsection Tracepoints support in @code{gdbserver}
22919 @cindex tracepoints support in @code{gdbserver}
22921 On some targets, @code{gdbserver} supports tracepoints, fast
22922 tracepoints and static tracepoints.
22924 For fast or static tracepoints to work, a special library called the
22925 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22926 This library is built and distributed as an integral part of
22927 @code{gdbserver}. In addition, support for static tracepoints
22928 requires building the in-process agent library with static tracepoints
22929 support. At present, the UST (LTTng Userspace Tracer,
22930 @url{http://lttng.org/ust}) tracing engine is supported. This support
22931 is automatically available if UST development headers are found in the
22932 standard include path when @code{gdbserver} is built, or if
22933 @code{gdbserver} was explicitly configured using @option{--with-ust}
22934 to point at such headers. You can explicitly disable the support
22935 using @option{--with-ust=no}.
22937 There are several ways to load the in-process agent in your program:
22940 @item Specifying it as dependency at link time
22942 You can link your program dynamically with the in-process agent
22943 library. On most systems, this is accomplished by adding
22944 @code{-linproctrace} to the link command.
22946 @item Using the system's preloading mechanisms
22948 You can force loading the in-process agent at startup time by using
22949 your system's support for preloading shared libraries. Many Unixes
22950 support the concept of preloading user defined libraries. In most
22951 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22952 in the environment. See also the description of @code{gdbserver}'s
22953 @option{--wrapper} command line option.
22955 @item Using @value{GDBN} to force loading the agent at run time
22957 On some systems, you can force the inferior to load a shared library,
22958 by calling a dynamic loader function in the inferior that takes care
22959 of dynamically looking up and loading a shared library. On most Unix
22960 systems, the function is @code{dlopen}. You'll use the @code{call}
22961 command for that. For example:
22964 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22967 Note that on most Unix systems, for the @code{dlopen} function to be
22968 available, the program needs to be linked with @code{-ldl}.
22971 On systems that have a userspace dynamic loader, like most Unix
22972 systems, when you connect to @code{gdbserver} using @code{target
22973 remote}, you'll find that the program is stopped at the dynamic
22974 loader's entry point, and no shared library has been loaded in the
22975 program's address space yet, including the in-process agent. In that
22976 case, before being able to use any of the fast or static tracepoints
22977 features, you need to let the loader run and load the shared
22978 libraries. The simplest way to do that is to run the program to the
22979 main procedure. E.g., if debugging a C or C@t{++} program, start
22980 @code{gdbserver} like so:
22983 $ gdbserver :9999 myprogram
22986 Start GDB and connect to @code{gdbserver} like so, and run to main:
22990 (@value{GDBP}) target remote myhost:9999
22991 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22992 (@value{GDBP}) b main
22993 (@value{GDBP}) continue
22996 The in-process tracing agent library should now be loaded into the
22997 process; you can confirm it with the @code{info sharedlibrary}
22998 command, which will list @file{libinproctrace.so} as loaded in the
22999 process. You are now ready to install fast tracepoints, list static
23000 tracepoint markers, probe static tracepoints markers, and start
23003 @node Remote Configuration
23004 @section Remote Configuration
23007 @kindex show remote
23008 This section documents the configuration options available when
23009 debugging remote programs. For the options related to the File I/O
23010 extensions of the remote protocol, see @ref{system,
23011 system-call-allowed}.
23014 @item set remoteaddresssize @var{bits}
23015 @cindex address size for remote targets
23016 @cindex bits in remote address
23017 Set the maximum size of address in a memory packet to the specified
23018 number of bits. @value{GDBN} will mask off the address bits above
23019 that number, when it passes addresses to the remote target. The
23020 default value is the number of bits in the target's address.
23022 @item show remoteaddresssize
23023 Show the current value of remote address size in bits.
23025 @item set serial baud @var{n}
23026 @cindex baud rate for remote targets
23027 Set the baud rate for the remote serial I/O to @var{n} baud. The
23028 value is used to set the speed of the serial port used for debugging
23031 @item show serial baud
23032 Show the current speed of the remote connection.
23034 @item set serial parity @var{parity}
23035 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23036 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23038 @item show serial parity
23039 Show the current parity of the serial port.
23041 @item set remotebreak
23042 @cindex interrupt remote programs
23043 @cindex BREAK signal instead of Ctrl-C
23044 @anchor{set remotebreak}
23045 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23046 when you type @kbd{Ctrl-c} to interrupt the program running
23047 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23048 character instead. The default is off, since most remote systems
23049 expect to see @samp{Ctrl-C} as the interrupt signal.
23051 @item show remotebreak
23052 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23053 interrupt the remote program.
23055 @item set remoteflow on
23056 @itemx set remoteflow off
23057 @kindex set remoteflow
23058 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23059 on the serial port used to communicate to the remote target.
23061 @item show remoteflow
23062 @kindex show remoteflow
23063 Show the current setting of hardware flow control.
23065 @item set remotelogbase @var{base}
23066 Set the base (a.k.a.@: radix) of logging serial protocol
23067 communications to @var{base}. Supported values of @var{base} are:
23068 @code{ascii}, @code{octal}, and @code{hex}. The default is
23071 @item show remotelogbase
23072 Show the current setting of the radix for logging remote serial
23075 @item set remotelogfile @var{file}
23076 @cindex record serial communications on file
23077 Record remote serial communications on the named @var{file}. The
23078 default is not to record at all.
23080 @item show remotelogfile
23081 Show the current setting of the file name on which to record the
23082 serial communications.
23084 @item set remotetimeout @var{num}
23085 @cindex timeout for serial communications
23086 @cindex remote timeout
23087 Set the timeout limit to wait for the remote target to respond to
23088 @var{num} seconds. The default is 2 seconds.
23090 @item show remotetimeout
23091 Show the current number of seconds to wait for the remote target
23094 @cindex limit hardware breakpoints and watchpoints
23095 @cindex remote target, limit break- and watchpoints
23096 @anchor{set remote hardware-watchpoint-limit}
23097 @anchor{set remote hardware-breakpoint-limit}
23098 @item set remote hardware-watchpoint-limit @var{limit}
23099 @itemx set remote hardware-breakpoint-limit @var{limit}
23100 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23101 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23102 watchpoints or breakpoints, and @code{unlimited} for unlimited
23103 watchpoints or breakpoints.
23105 @item show remote hardware-watchpoint-limit
23106 @itemx show remote hardware-breakpoint-limit
23107 Show the current limit for the number of hardware watchpoints or
23108 breakpoints that @value{GDBN} can use.
23110 @cindex limit hardware watchpoints length
23111 @cindex remote target, limit watchpoints length
23112 @anchor{set remote hardware-watchpoint-length-limit}
23113 @item set remote hardware-watchpoint-length-limit @var{limit}
23114 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23115 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23116 hardware watchpoints and @code{unlimited} allows watchpoints of any
23119 @item show remote hardware-watchpoint-length-limit
23120 Show the current limit (in bytes) of the maximum length of
23121 a remote hardware watchpoint.
23123 @item set remote exec-file @var{filename}
23124 @itemx show remote exec-file
23125 @anchor{set remote exec-file}
23126 @cindex executable file, for remote target
23127 Select the file used for @code{run} with @code{target
23128 extended-remote}. This should be set to a filename valid on the
23129 target system. If it is not set, the target will use a default
23130 filename (e.g.@: the last program run).
23132 @item set remote interrupt-sequence
23133 @cindex interrupt remote programs
23134 @cindex select Ctrl-C, BREAK or BREAK-g
23135 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23136 @samp{BREAK-g} as the
23137 sequence to the remote target in order to interrupt the execution.
23138 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23139 is high level of serial line for some certain time.
23140 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23141 It is @code{BREAK} signal followed by character @code{g}.
23143 @item show remote interrupt-sequence
23144 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23145 is sent by @value{GDBN} to interrupt the remote program.
23146 @code{BREAK-g} is BREAK signal followed by @code{g} and
23147 also known as Magic SysRq g.
23149 @item set remote interrupt-on-connect
23150 @cindex send interrupt-sequence on start
23151 Specify whether interrupt-sequence is sent to remote target when
23152 @value{GDBN} connects to it. This is mostly needed when you debug
23153 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23154 which is known as Magic SysRq g in order to connect @value{GDBN}.
23156 @item show remote interrupt-on-connect
23157 Show whether interrupt-sequence is sent
23158 to remote target when @value{GDBN} connects to it.
23162 @item set tcp auto-retry on
23163 @cindex auto-retry, for remote TCP target
23164 Enable auto-retry for remote TCP connections. This is useful if the remote
23165 debugging agent is launched in parallel with @value{GDBN}; there is a race
23166 condition because the agent may not become ready to accept the connection
23167 before @value{GDBN} attempts to connect. When auto-retry is
23168 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23169 to establish the connection using the timeout specified by
23170 @code{set tcp connect-timeout}.
23172 @item set tcp auto-retry off
23173 Do not auto-retry failed TCP connections.
23175 @item show tcp auto-retry
23176 Show the current auto-retry setting.
23178 @item set tcp connect-timeout @var{seconds}
23179 @itemx set tcp connect-timeout unlimited
23180 @cindex connection timeout, for remote TCP target
23181 @cindex timeout, for remote target connection
23182 Set the timeout for establishing a TCP connection to the remote target to
23183 @var{seconds}. The timeout affects both polling to retry failed connections
23184 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23185 that are merely slow to complete, and represents an approximate cumulative
23186 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23187 @value{GDBN} will keep attempting to establish a connection forever,
23188 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23190 @item show tcp connect-timeout
23191 Show the current connection timeout setting.
23194 @cindex remote packets, enabling and disabling
23195 The @value{GDBN} remote protocol autodetects the packets supported by
23196 your debugging stub. If you need to override the autodetection, you
23197 can use these commands to enable or disable individual packets. Each
23198 packet can be set to @samp{on} (the remote target supports this
23199 packet), @samp{off} (the remote target does not support this packet),
23200 or @samp{auto} (detect remote target support for this packet). They
23201 all default to @samp{auto}. For more information about each packet,
23202 see @ref{Remote Protocol}.
23204 During normal use, you should not have to use any of these commands.
23205 If you do, that may be a bug in your remote debugging stub, or a bug
23206 in @value{GDBN}. You may want to report the problem to the
23207 @value{GDBN} developers.
23209 For each packet @var{name}, the command to enable or disable the
23210 packet is @code{set remote @var{name}-packet}. The available settings
23213 @multitable @columnfractions 0.28 0.32 0.25
23216 @tab Related Features
23218 @item @code{fetch-register}
23220 @tab @code{info registers}
23222 @item @code{set-register}
23226 @item @code{binary-download}
23228 @tab @code{load}, @code{set}
23230 @item @code{read-aux-vector}
23231 @tab @code{qXfer:auxv:read}
23232 @tab @code{info auxv}
23234 @item @code{symbol-lookup}
23235 @tab @code{qSymbol}
23236 @tab Detecting multiple threads
23238 @item @code{attach}
23239 @tab @code{vAttach}
23242 @item @code{verbose-resume}
23244 @tab Stepping or resuming multiple threads
23250 @item @code{software-breakpoint}
23254 @item @code{hardware-breakpoint}
23258 @item @code{write-watchpoint}
23262 @item @code{read-watchpoint}
23266 @item @code{access-watchpoint}
23270 @item @code{pid-to-exec-file}
23271 @tab @code{qXfer:exec-file:read}
23272 @tab @code{attach}, @code{run}
23274 @item @code{target-features}
23275 @tab @code{qXfer:features:read}
23276 @tab @code{set architecture}
23278 @item @code{library-info}
23279 @tab @code{qXfer:libraries:read}
23280 @tab @code{info sharedlibrary}
23282 @item @code{memory-map}
23283 @tab @code{qXfer:memory-map:read}
23284 @tab @code{info mem}
23286 @item @code{read-sdata-object}
23287 @tab @code{qXfer:sdata:read}
23288 @tab @code{print $_sdata}
23290 @item @code{read-siginfo-object}
23291 @tab @code{qXfer:siginfo:read}
23292 @tab @code{print $_siginfo}
23294 @item @code{write-siginfo-object}
23295 @tab @code{qXfer:siginfo:write}
23296 @tab @code{set $_siginfo}
23298 @item @code{threads}
23299 @tab @code{qXfer:threads:read}
23300 @tab @code{info threads}
23302 @item @code{get-thread-local-@*storage-address}
23303 @tab @code{qGetTLSAddr}
23304 @tab Displaying @code{__thread} variables
23306 @item @code{get-thread-information-block-address}
23307 @tab @code{qGetTIBAddr}
23308 @tab Display MS-Windows Thread Information Block.
23310 @item @code{search-memory}
23311 @tab @code{qSearch:memory}
23314 @item @code{supported-packets}
23315 @tab @code{qSupported}
23316 @tab Remote communications parameters
23318 @item @code{catch-syscalls}
23319 @tab @code{QCatchSyscalls}
23320 @tab @code{catch syscall}
23322 @item @code{pass-signals}
23323 @tab @code{QPassSignals}
23324 @tab @code{handle @var{signal}}
23326 @item @code{program-signals}
23327 @tab @code{QProgramSignals}
23328 @tab @code{handle @var{signal}}
23330 @item @code{hostio-close-packet}
23331 @tab @code{vFile:close}
23332 @tab @code{remote get}, @code{remote put}
23334 @item @code{hostio-open-packet}
23335 @tab @code{vFile:open}
23336 @tab @code{remote get}, @code{remote put}
23338 @item @code{hostio-pread-packet}
23339 @tab @code{vFile:pread}
23340 @tab @code{remote get}, @code{remote put}
23342 @item @code{hostio-pwrite-packet}
23343 @tab @code{vFile:pwrite}
23344 @tab @code{remote get}, @code{remote put}
23346 @item @code{hostio-unlink-packet}
23347 @tab @code{vFile:unlink}
23348 @tab @code{remote delete}
23350 @item @code{hostio-readlink-packet}
23351 @tab @code{vFile:readlink}
23354 @item @code{hostio-fstat-packet}
23355 @tab @code{vFile:fstat}
23358 @item @code{hostio-setfs-packet}
23359 @tab @code{vFile:setfs}
23362 @item @code{noack-packet}
23363 @tab @code{QStartNoAckMode}
23364 @tab Packet acknowledgment
23366 @item @code{osdata}
23367 @tab @code{qXfer:osdata:read}
23368 @tab @code{info os}
23370 @item @code{query-attached}
23371 @tab @code{qAttached}
23372 @tab Querying remote process attach state.
23374 @item @code{trace-buffer-size}
23375 @tab @code{QTBuffer:size}
23376 @tab @code{set trace-buffer-size}
23378 @item @code{trace-status}
23379 @tab @code{qTStatus}
23380 @tab @code{tstatus}
23382 @item @code{traceframe-info}
23383 @tab @code{qXfer:traceframe-info:read}
23384 @tab Traceframe info
23386 @item @code{install-in-trace}
23387 @tab @code{InstallInTrace}
23388 @tab Install tracepoint in tracing
23390 @item @code{disable-randomization}
23391 @tab @code{QDisableRandomization}
23392 @tab @code{set disable-randomization}
23394 @item @code{startup-with-shell}
23395 @tab @code{QStartupWithShell}
23396 @tab @code{set startup-with-shell}
23398 @item @code{environment-hex-encoded}
23399 @tab @code{QEnvironmentHexEncoded}
23400 @tab @code{set environment}
23402 @item @code{environment-unset}
23403 @tab @code{QEnvironmentUnset}
23404 @tab @code{unset environment}
23406 @item @code{environment-reset}
23407 @tab @code{QEnvironmentReset}
23408 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23410 @item @code{set-working-dir}
23411 @tab @code{QSetWorkingDir}
23412 @tab @code{set cwd}
23414 @item @code{conditional-breakpoints-packet}
23415 @tab @code{Z0 and Z1}
23416 @tab @code{Support for target-side breakpoint condition evaluation}
23418 @item @code{multiprocess-extensions}
23419 @tab @code{multiprocess extensions}
23420 @tab Debug multiple processes and remote process PID awareness
23422 @item @code{swbreak-feature}
23423 @tab @code{swbreak stop reason}
23426 @item @code{hwbreak-feature}
23427 @tab @code{hwbreak stop reason}
23430 @item @code{fork-event-feature}
23431 @tab @code{fork stop reason}
23434 @item @code{vfork-event-feature}
23435 @tab @code{vfork stop reason}
23438 @item @code{exec-event-feature}
23439 @tab @code{exec stop reason}
23442 @item @code{thread-events}
23443 @tab @code{QThreadEvents}
23444 @tab Tracking thread lifetime.
23446 @item @code{no-resumed-stop-reply}
23447 @tab @code{no resumed thread left stop reply}
23448 @tab Tracking thread lifetime.
23453 @section Implementing a Remote Stub
23455 @cindex debugging stub, example
23456 @cindex remote stub, example
23457 @cindex stub example, remote debugging
23458 The stub files provided with @value{GDBN} implement the target side of the
23459 communication protocol, and the @value{GDBN} side is implemented in the
23460 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23461 these subroutines to communicate, and ignore the details. (If you're
23462 implementing your own stub file, you can still ignore the details: start
23463 with one of the existing stub files. @file{sparc-stub.c} is the best
23464 organized, and therefore the easiest to read.)
23466 @cindex remote serial debugging, overview
23467 To debug a program running on another machine (the debugging
23468 @dfn{target} machine), you must first arrange for all the usual
23469 prerequisites for the program to run by itself. For example, for a C
23474 A startup routine to set up the C runtime environment; these usually
23475 have a name like @file{crt0}. The startup routine may be supplied by
23476 your hardware supplier, or you may have to write your own.
23479 A C subroutine library to support your program's
23480 subroutine calls, notably managing input and output.
23483 A way of getting your program to the other machine---for example, a
23484 download program. These are often supplied by the hardware
23485 manufacturer, but you may have to write your own from hardware
23489 The next step is to arrange for your program to use a serial port to
23490 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23491 machine). In general terms, the scheme looks like this:
23495 @value{GDBN} already understands how to use this protocol; when everything
23496 else is set up, you can simply use the @samp{target remote} command
23497 (@pxref{Targets,,Specifying a Debugging Target}).
23499 @item On the target,
23500 you must link with your program a few special-purpose subroutines that
23501 implement the @value{GDBN} remote serial protocol. The file containing these
23502 subroutines is called a @dfn{debugging stub}.
23504 On certain remote targets, you can use an auxiliary program
23505 @code{gdbserver} instead of linking a stub into your program.
23506 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23509 The debugging stub is specific to the architecture of the remote
23510 machine; for example, use @file{sparc-stub.c} to debug programs on
23513 @cindex remote serial stub list
23514 These working remote stubs are distributed with @value{GDBN}:
23519 @cindex @file{i386-stub.c}
23522 For Intel 386 and compatible architectures.
23525 @cindex @file{m68k-stub.c}
23526 @cindex Motorola 680x0
23528 For Motorola 680x0 architectures.
23531 @cindex @file{sh-stub.c}
23534 For Renesas SH architectures.
23537 @cindex @file{sparc-stub.c}
23539 For @sc{sparc} architectures.
23541 @item sparcl-stub.c
23542 @cindex @file{sparcl-stub.c}
23545 For Fujitsu @sc{sparclite} architectures.
23549 The @file{README} file in the @value{GDBN} distribution may list other
23550 recently added stubs.
23553 * Stub Contents:: What the stub can do for you
23554 * Bootstrapping:: What you must do for the stub
23555 * Debug Session:: Putting it all together
23558 @node Stub Contents
23559 @subsection What the Stub Can Do for You
23561 @cindex remote serial stub
23562 The debugging stub for your architecture supplies these three
23566 @item set_debug_traps
23567 @findex set_debug_traps
23568 @cindex remote serial stub, initialization
23569 This routine arranges for @code{handle_exception} to run when your
23570 program stops. You must call this subroutine explicitly in your
23571 program's startup code.
23573 @item handle_exception
23574 @findex handle_exception
23575 @cindex remote serial stub, main routine
23576 This is the central workhorse, but your program never calls it
23577 explicitly---the setup code arranges for @code{handle_exception} to
23578 run when a trap is triggered.
23580 @code{handle_exception} takes control when your program stops during
23581 execution (for example, on a breakpoint), and mediates communications
23582 with @value{GDBN} on the host machine. This is where the communications
23583 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23584 representative on the target machine. It begins by sending summary
23585 information on the state of your program, then continues to execute,
23586 retrieving and transmitting any information @value{GDBN} needs, until you
23587 execute a @value{GDBN} command that makes your program resume; at that point,
23588 @code{handle_exception} returns control to your own code on the target
23592 @cindex @code{breakpoint} subroutine, remote
23593 Use this auxiliary subroutine to make your program contain a
23594 breakpoint. Depending on the particular situation, this may be the only
23595 way for @value{GDBN} to get control. For instance, if your target
23596 machine has some sort of interrupt button, you won't need to call this;
23597 pressing the interrupt button transfers control to
23598 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23599 simply receiving characters on the serial port may also trigger a trap;
23600 again, in that situation, you don't need to call @code{breakpoint} from
23601 your own program---simply running @samp{target remote} from the host
23602 @value{GDBN} session gets control.
23604 Call @code{breakpoint} if none of these is true, or if you simply want
23605 to make certain your program stops at a predetermined point for the
23606 start of your debugging session.
23609 @node Bootstrapping
23610 @subsection What You Must Do for the Stub
23612 @cindex remote stub, support routines
23613 The debugging stubs that come with @value{GDBN} are set up for a particular
23614 chip architecture, but they have no information about the rest of your
23615 debugging target machine.
23617 First of all you need to tell the stub how to communicate with the
23621 @item int getDebugChar()
23622 @findex getDebugChar
23623 Write this subroutine to read a single character from the serial port.
23624 It may be identical to @code{getchar} for your target system; a
23625 different name is used to allow you to distinguish the two if you wish.
23627 @item void putDebugChar(int)
23628 @findex putDebugChar
23629 Write this subroutine to write a single character to the serial port.
23630 It may be identical to @code{putchar} for your target system; a
23631 different name is used to allow you to distinguish the two if you wish.
23634 @cindex control C, and remote debugging
23635 @cindex interrupting remote targets
23636 If you want @value{GDBN} to be able to stop your program while it is
23637 running, you need to use an interrupt-driven serial driver, and arrange
23638 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23639 character). That is the character which @value{GDBN} uses to tell the
23640 remote system to stop.
23642 Getting the debugging target to return the proper status to @value{GDBN}
23643 probably requires changes to the standard stub; one quick and dirty way
23644 is to just execute a breakpoint instruction (the ``dirty'' part is that
23645 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23647 Other routines you need to supply are:
23650 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23651 @findex exceptionHandler
23652 Write this function to install @var{exception_address} in the exception
23653 handling tables. You need to do this because the stub does not have any
23654 way of knowing what the exception handling tables on your target system
23655 are like (for example, the processor's table might be in @sc{rom},
23656 containing entries which point to a table in @sc{ram}).
23657 The @var{exception_number} specifies the exception which should be changed;
23658 its meaning is architecture-dependent (for example, different numbers
23659 might represent divide by zero, misaligned access, etc). When this
23660 exception occurs, control should be transferred directly to
23661 @var{exception_address}, and the processor state (stack, registers,
23662 and so on) should be just as it is when a processor exception occurs. So if
23663 you want to use a jump instruction to reach @var{exception_address}, it
23664 should be a simple jump, not a jump to subroutine.
23666 For the 386, @var{exception_address} should be installed as an interrupt
23667 gate so that interrupts are masked while the handler runs. The gate
23668 should be at privilege level 0 (the most privileged level). The
23669 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23670 help from @code{exceptionHandler}.
23672 @item void flush_i_cache()
23673 @findex flush_i_cache
23674 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23675 instruction cache, if any, on your target machine. If there is no
23676 instruction cache, this subroutine may be a no-op.
23678 On target machines that have instruction caches, @value{GDBN} requires this
23679 function to make certain that the state of your program is stable.
23683 You must also make sure this library routine is available:
23686 @item void *memset(void *, int, int)
23688 This is the standard library function @code{memset} that sets an area of
23689 memory to a known value. If you have one of the free versions of
23690 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23691 either obtain it from your hardware manufacturer, or write your own.
23694 If you do not use the GNU C compiler, you may need other standard
23695 library subroutines as well; this varies from one stub to another,
23696 but in general the stubs are likely to use any of the common library
23697 subroutines which @code{@value{NGCC}} generates as inline code.
23700 @node Debug Session
23701 @subsection Putting it All Together
23703 @cindex remote serial debugging summary
23704 In summary, when your program is ready to debug, you must follow these
23709 Make sure you have defined the supporting low-level routines
23710 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23712 @code{getDebugChar}, @code{putDebugChar},
23713 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23717 Insert these lines in your program's startup code, before the main
23718 procedure is called:
23725 On some machines, when a breakpoint trap is raised, the hardware
23726 automatically makes the PC point to the instruction after the
23727 breakpoint. If your machine doesn't do that, you may need to adjust
23728 @code{handle_exception} to arrange for it to return to the instruction
23729 after the breakpoint on this first invocation, so that your program
23730 doesn't keep hitting the initial breakpoint instead of making
23734 For the 680x0 stub only, you need to provide a variable called
23735 @code{exceptionHook}. Normally you just use:
23738 void (*exceptionHook)() = 0;
23742 but if before calling @code{set_debug_traps}, you set it to point to a
23743 function in your program, that function is called when
23744 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23745 error). The function indicated by @code{exceptionHook} is called with
23746 one parameter: an @code{int} which is the exception number.
23749 Compile and link together: your program, the @value{GDBN} debugging stub for
23750 your target architecture, and the supporting subroutines.
23753 Make sure you have a serial connection between your target machine and
23754 the @value{GDBN} host, and identify the serial port on the host.
23757 @c The "remote" target now provides a `load' command, so we should
23758 @c document that. FIXME.
23759 Download your program to your target machine (or get it there by
23760 whatever means the manufacturer provides), and start it.
23763 Start @value{GDBN} on the host, and connect to the target
23764 (@pxref{Connecting,,Connecting to a Remote Target}).
23768 @node Configurations
23769 @chapter Configuration-Specific Information
23771 While nearly all @value{GDBN} commands are available for all native and
23772 cross versions of the debugger, there are some exceptions. This chapter
23773 describes things that are only available in certain configurations.
23775 There are three major categories of configurations: native
23776 configurations, where the host and target are the same, embedded
23777 operating system configurations, which are usually the same for several
23778 different processor architectures, and bare embedded processors, which
23779 are quite different from each other.
23784 * Embedded Processors::
23791 This section describes details specific to particular native
23795 * BSD libkvm Interface:: Debugging BSD kernel memory images
23796 * Process Information:: Process information
23797 * DJGPP Native:: Features specific to the DJGPP port
23798 * Cygwin Native:: Features specific to the Cygwin port
23799 * Hurd Native:: Features specific to @sc{gnu} Hurd
23800 * Darwin:: Features specific to Darwin
23801 * FreeBSD:: Features specific to FreeBSD
23804 @node BSD libkvm Interface
23805 @subsection BSD libkvm Interface
23808 @cindex kernel memory image
23809 @cindex kernel crash dump
23811 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23812 interface that provides a uniform interface for accessing kernel virtual
23813 memory images, including live systems and crash dumps. @value{GDBN}
23814 uses this interface to allow you to debug live kernels and kernel crash
23815 dumps on many native BSD configurations. This is implemented as a
23816 special @code{kvm} debugging target. For debugging a live system, load
23817 the currently running kernel into @value{GDBN} and connect to the
23821 (@value{GDBP}) @b{target kvm}
23824 For debugging crash dumps, provide the file name of the crash dump as an
23828 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23831 Once connected to the @code{kvm} target, the following commands are
23837 Set current context from the @dfn{Process Control Block} (PCB) address.
23840 Set current context from proc address. This command isn't available on
23841 modern FreeBSD systems.
23844 @node Process Information
23845 @subsection Process Information
23847 @cindex examine process image
23848 @cindex process info via @file{/proc}
23850 Some operating systems provide interfaces to fetch additional
23851 information about running processes beyond memory and per-thread
23852 register state. If @value{GDBN} is configured for an operating system
23853 with a supported interface, the command @code{info proc} is available
23854 to report information about the process running your program, or about
23855 any process running on your system.
23857 One supported interface is a facility called @samp{/proc} that can be
23858 used to examine the image of a running process using file-system
23859 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23862 On FreeBSD and NetBSD systems, system control nodes are used to query
23863 process information.
23865 In addition, some systems may provide additional process information
23866 in core files. Note that a core file may include a subset of the
23867 information available from a live process. Process information is
23868 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23875 @itemx info proc @var{process-id}
23876 Summarize available information about a process. If a
23877 process ID is specified by @var{process-id}, display information about
23878 that process; otherwise display information about the program being
23879 debugged. The summary includes the debugged process ID, the command
23880 line used to invoke it, its current working directory, and its
23881 executable file's absolute file name.
23883 On some systems, @var{process-id} can be of the form
23884 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23885 within a process. If the optional @var{pid} part is missing, it means
23886 a thread from the process being debugged (the leading @samp{/} still
23887 needs to be present, or else @value{GDBN} will interpret the number as
23888 a process ID rather than a thread ID).
23890 @item info proc cmdline
23891 @cindex info proc cmdline
23892 Show the original command line of the process. This command is
23893 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23895 @item info proc cwd
23896 @cindex info proc cwd
23897 Show the current working directory of the process. This command is
23898 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23900 @item info proc exe
23901 @cindex info proc exe
23902 Show the name of executable of the process. This command is supported
23903 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23905 @item info proc files
23906 @cindex info proc files
23907 Show the file descriptors open by the process. For each open file
23908 descriptor, @value{GDBN} shows its number, type (file, directory,
23909 character device, socket), file pointer offset, and the name of the
23910 resource open on the descriptor. The resource name can be a file name
23911 (for files, directories, and devices) or a protocol followed by socket
23912 address (for network connections). This command is supported on
23915 This example shows the open file descriptors for a process using a
23916 tty for standard input and output as well as two network sockets:
23919 (gdb) info proc files 22136
23923 FD Type Offset Flags Name
23924 text file - r-------- /usr/bin/ssh
23925 ctty chr - rw------- /dev/pts/20
23926 cwd dir - r-------- /usr/home/john
23927 root dir - r-------- /
23928 0 chr 0x32933a4 rw------- /dev/pts/20
23929 1 chr 0x32933a4 rw------- /dev/pts/20
23930 2 chr 0x32933a4 rw------- /dev/pts/20
23931 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23932 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23935 @item info proc mappings
23936 @cindex memory address space mappings
23937 Report the memory address space ranges accessible in a process. On
23938 Solaris, FreeBSD and NetBSD systems, each memory range includes information
23939 on whether the process has read, write, or execute access rights to each
23940 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
23941 includes the object file which is mapped to that range.
23943 @item info proc stat
23944 @itemx info proc status
23945 @cindex process detailed status information
23946 Show additional process-related information, including the user ID and
23947 group ID; virtual memory usage; the signals that are pending, blocked,
23948 and ignored; its TTY; its consumption of system and user time; its
23949 stack size; its @samp{nice} value; etc. These commands are supported
23950 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23952 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23953 information (type @kbd{man 5 proc} from your shell prompt).
23955 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
23956 @code{info proc status}.
23958 @item info proc all
23959 Show all the information about the process described under all of the
23960 above @code{info proc} subcommands.
23963 @comment These sub-options of 'info proc' were not included when
23964 @comment procfs.c was re-written. Keep their descriptions around
23965 @comment against the day when someone finds the time to put them back in.
23966 @kindex info proc times
23967 @item info proc times
23968 Starting time, user CPU time, and system CPU time for your program and
23971 @kindex info proc id
23973 Report on the process IDs related to your program: its own process ID,
23974 the ID of its parent, the process group ID, and the session ID.
23977 @item set procfs-trace
23978 @kindex set procfs-trace
23979 @cindex @code{procfs} API calls
23980 This command enables and disables tracing of @code{procfs} API calls.
23982 @item show procfs-trace
23983 @kindex show procfs-trace
23984 Show the current state of @code{procfs} API call tracing.
23986 @item set procfs-file @var{file}
23987 @kindex set procfs-file
23988 Tell @value{GDBN} to write @code{procfs} API trace to the named
23989 @var{file}. @value{GDBN} appends the trace info to the previous
23990 contents of the file. The default is to display the trace on the
23993 @item show procfs-file
23994 @kindex show procfs-file
23995 Show the file to which @code{procfs} API trace is written.
23997 @item proc-trace-entry
23998 @itemx proc-trace-exit
23999 @itemx proc-untrace-entry
24000 @itemx proc-untrace-exit
24001 @kindex proc-trace-entry
24002 @kindex proc-trace-exit
24003 @kindex proc-untrace-entry
24004 @kindex proc-untrace-exit
24005 These commands enable and disable tracing of entries into and exits
24006 from the @code{syscall} interface.
24009 @kindex info pidlist
24010 @cindex process list, QNX Neutrino
24011 For QNX Neutrino only, this command displays the list of all the
24012 processes and all the threads within each process.
24015 @kindex info meminfo
24016 @cindex mapinfo list, QNX Neutrino
24017 For QNX Neutrino only, this command displays the list of all mapinfos.
24021 @subsection Features for Debugging @sc{djgpp} Programs
24022 @cindex @sc{djgpp} debugging
24023 @cindex native @sc{djgpp} debugging
24024 @cindex MS-DOS-specific commands
24027 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24028 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24029 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24030 top of real-mode DOS systems and their emulations.
24032 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24033 defines a few commands specific to the @sc{djgpp} port. This
24034 subsection describes those commands.
24039 This is a prefix of @sc{djgpp}-specific commands which print
24040 information about the target system and important OS structures.
24043 @cindex MS-DOS system info
24044 @cindex free memory information (MS-DOS)
24045 @item info dos sysinfo
24046 This command displays assorted information about the underlying
24047 platform: the CPU type and features, the OS version and flavor, the
24048 DPMI version, and the available conventional and DPMI memory.
24053 @cindex segment descriptor tables
24054 @cindex descriptor tables display
24056 @itemx info dos ldt
24057 @itemx info dos idt
24058 These 3 commands display entries from, respectively, Global, Local,
24059 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24060 tables are data structures which store a descriptor for each segment
24061 that is currently in use. The segment's selector is an index into a
24062 descriptor table; the table entry for that index holds the
24063 descriptor's base address and limit, and its attributes and access
24066 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24067 segment (used for both data and the stack), and a DOS segment (which
24068 allows access to DOS/BIOS data structures and absolute addresses in
24069 conventional memory). However, the DPMI host will usually define
24070 additional segments in order to support the DPMI environment.
24072 @cindex garbled pointers
24073 These commands allow to display entries from the descriptor tables.
24074 Without an argument, all entries from the specified table are
24075 displayed. An argument, which should be an integer expression, means
24076 display a single entry whose index is given by the argument. For
24077 example, here's a convenient way to display information about the
24078 debugged program's data segment:
24081 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24082 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24086 This comes in handy when you want to see whether a pointer is outside
24087 the data segment's limit (i.e.@: @dfn{garbled}).
24089 @cindex page tables display (MS-DOS)
24091 @itemx info dos pte
24092 These two commands display entries from, respectively, the Page
24093 Directory and the Page Tables. Page Directories and Page Tables are
24094 data structures which control how virtual memory addresses are mapped
24095 into physical addresses. A Page Table includes an entry for every
24096 page of memory that is mapped into the program's address space; there
24097 may be several Page Tables, each one holding up to 4096 entries. A
24098 Page Directory has up to 4096 entries, one each for every Page Table
24099 that is currently in use.
24101 Without an argument, @kbd{info dos pde} displays the entire Page
24102 Directory, and @kbd{info dos pte} displays all the entries in all of
24103 the Page Tables. An argument, an integer expression, given to the
24104 @kbd{info dos pde} command means display only that entry from the Page
24105 Directory table. An argument given to the @kbd{info dos pte} command
24106 means display entries from a single Page Table, the one pointed to by
24107 the specified entry in the Page Directory.
24109 @cindex direct memory access (DMA) on MS-DOS
24110 These commands are useful when your program uses @dfn{DMA} (Direct
24111 Memory Access), which needs physical addresses to program the DMA
24114 These commands are supported only with some DPMI servers.
24116 @cindex physical address from linear address
24117 @item info dos address-pte @var{addr}
24118 This command displays the Page Table entry for a specified linear
24119 address. The argument @var{addr} is a linear address which should
24120 already have the appropriate segment's base address added to it,
24121 because this command accepts addresses which may belong to @emph{any}
24122 segment. For example, here's how to display the Page Table entry for
24123 the page where a variable @code{i} is stored:
24126 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24127 @exdent @code{Page Table entry for address 0x11a00d30:}
24128 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24132 This says that @code{i} is stored at offset @code{0xd30} from the page
24133 whose physical base address is @code{0x02698000}, and shows all the
24134 attributes of that page.
24136 Note that you must cast the addresses of variables to a @code{char *},
24137 since otherwise the value of @code{__djgpp_base_address}, the base
24138 address of all variables and functions in a @sc{djgpp} program, will
24139 be added using the rules of C pointer arithmetics: if @code{i} is
24140 declared an @code{int}, @value{GDBN} will add 4 times the value of
24141 @code{__djgpp_base_address} to the address of @code{i}.
24143 Here's another example, it displays the Page Table entry for the
24147 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24148 @exdent @code{Page Table entry for address 0x29110:}
24149 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24153 (The @code{+ 3} offset is because the transfer buffer's address is the
24154 3rd member of the @code{_go32_info_block} structure.) The output
24155 clearly shows that this DPMI server maps the addresses in conventional
24156 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24157 linear (@code{0x29110}) addresses are identical.
24159 This command is supported only with some DPMI servers.
24162 @cindex DOS serial data link, remote debugging
24163 In addition to native debugging, the DJGPP port supports remote
24164 debugging via a serial data link. The following commands are specific
24165 to remote serial debugging in the DJGPP port of @value{GDBN}.
24168 @kindex set com1base
24169 @kindex set com1irq
24170 @kindex set com2base
24171 @kindex set com2irq
24172 @kindex set com3base
24173 @kindex set com3irq
24174 @kindex set com4base
24175 @kindex set com4irq
24176 @item set com1base @var{addr}
24177 This command sets the base I/O port address of the @file{COM1} serial
24180 @item set com1irq @var{irq}
24181 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24182 for the @file{COM1} serial port.
24184 There are similar commands @samp{set com2base}, @samp{set com3irq},
24185 etc.@: for setting the port address and the @code{IRQ} lines for the
24188 @kindex show com1base
24189 @kindex show com1irq
24190 @kindex show com2base
24191 @kindex show com2irq
24192 @kindex show com3base
24193 @kindex show com3irq
24194 @kindex show com4base
24195 @kindex show com4irq
24196 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24197 display the current settings of the base address and the @code{IRQ}
24198 lines used by the COM ports.
24201 @kindex info serial
24202 @cindex DOS serial port status
24203 This command prints the status of the 4 DOS serial ports. For each
24204 port, it prints whether it's active or not, its I/O base address and
24205 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24206 counts of various errors encountered so far.
24210 @node Cygwin Native
24211 @subsection Features for Debugging MS Windows PE Executables
24212 @cindex MS Windows debugging
24213 @cindex native Cygwin debugging
24214 @cindex Cygwin-specific commands
24216 @value{GDBN} supports native debugging of MS Windows programs, including
24217 DLLs with and without symbolic debugging information.
24219 @cindex Ctrl-BREAK, MS-Windows
24220 @cindex interrupt debuggee on MS-Windows
24221 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24222 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24223 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24224 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24225 sequence, which can be used to interrupt the debuggee even if it
24228 There are various additional Cygwin-specific commands, described in
24229 this section. Working with DLLs that have no debugging symbols is
24230 described in @ref{Non-debug DLL Symbols}.
24235 This is a prefix of MS Windows-specific commands which print
24236 information about the target system and important OS structures.
24238 @item info w32 selector
24239 This command displays information returned by
24240 the Win32 API @code{GetThreadSelectorEntry} function.
24241 It takes an optional argument that is evaluated to
24242 a long value to give the information about this given selector.
24243 Without argument, this command displays information
24244 about the six segment registers.
24246 @item info w32 thread-information-block
24247 This command displays thread specific information stored in the
24248 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24249 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24251 @kindex signal-event
24252 @item signal-event @var{id}
24253 This command signals an event with user-provided @var{id}. Used to resume
24254 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24256 To use it, create or edit the following keys in
24257 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24258 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24259 (for x86_64 versions):
24263 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24264 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24265 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24267 The first @code{%ld} will be replaced by the process ID of the
24268 crashing process, the second @code{%ld} will be replaced by the ID of
24269 the event that blocks the crashing process, waiting for @value{GDBN}
24273 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24274 make the system run debugger specified by the Debugger key
24275 automatically, @code{0} will cause a dialog box with ``OK'' and
24276 ``Cancel'' buttons to appear, which allows the user to either
24277 terminate the crashing process (OK) or debug it (Cancel).
24280 @kindex set cygwin-exceptions
24281 @cindex debugging the Cygwin DLL
24282 @cindex Cygwin DLL, debugging
24283 @item set cygwin-exceptions @var{mode}
24284 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24285 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24286 @value{GDBN} will delay recognition of exceptions, and may ignore some
24287 exceptions which seem to be caused by internal Cygwin DLL
24288 ``bookkeeping''. This option is meant primarily for debugging the
24289 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24290 @value{GDBN} users with false @code{SIGSEGV} signals.
24292 @kindex show cygwin-exceptions
24293 @item show cygwin-exceptions
24294 Displays whether @value{GDBN} will break on exceptions that happen
24295 inside the Cygwin DLL itself.
24297 @kindex set new-console
24298 @item set new-console @var{mode}
24299 If @var{mode} is @code{on} the debuggee will
24300 be started in a new console on next start.
24301 If @var{mode} is @code{off}, the debuggee will
24302 be started in the same console as the debugger.
24304 @kindex show new-console
24305 @item show new-console
24306 Displays whether a new console is used
24307 when the debuggee is started.
24309 @kindex set new-group
24310 @item set new-group @var{mode}
24311 This boolean value controls whether the debuggee should
24312 start a new group or stay in the same group as the debugger.
24313 This affects the way the Windows OS handles
24316 @kindex show new-group
24317 @item show new-group
24318 Displays current value of new-group boolean.
24320 @kindex set debugevents
24321 @item set debugevents
24322 This boolean value adds debug output concerning kernel events related
24323 to the debuggee seen by the debugger. This includes events that
24324 signal thread and process creation and exit, DLL loading and
24325 unloading, console interrupts, and debugging messages produced by the
24326 Windows @code{OutputDebugString} API call.
24328 @kindex set debugexec
24329 @item set debugexec
24330 This boolean value adds debug output concerning execute events
24331 (such as resume thread) seen by the debugger.
24333 @kindex set debugexceptions
24334 @item set debugexceptions
24335 This boolean value adds debug output concerning exceptions in the
24336 debuggee seen by the debugger.
24338 @kindex set debugmemory
24339 @item set debugmemory
24340 This boolean value adds debug output concerning debuggee memory reads
24341 and writes by the debugger.
24345 This boolean values specifies whether the debuggee is called
24346 via a shell or directly (default value is on).
24350 Displays if the debuggee will be started with a shell.
24355 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24358 @node Non-debug DLL Symbols
24359 @subsubsection Support for DLLs without Debugging Symbols
24360 @cindex DLLs with no debugging symbols
24361 @cindex Minimal symbols and DLLs
24363 Very often on windows, some of the DLLs that your program relies on do
24364 not include symbolic debugging information (for example,
24365 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24366 symbols in a DLL, it relies on the minimal amount of symbolic
24367 information contained in the DLL's export table. This section
24368 describes working with such symbols, known internally to @value{GDBN} as
24369 ``minimal symbols''.
24371 Note that before the debugged program has started execution, no DLLs
24372 will have been loaded. The easiest way around this problem is simply to
24373 start the program --- either by setting a breakpoint or letting the
24374 program run once to completion.
24376 @subsubsection DLL Name Prefixes
24378 In keeping with the naming conventions used by the Microsoft debugging
24379 tools, DLL export symbols are made available with a prefix based on the
24380 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24381 also entered into the symbol table, so @code{CreateFileA} is often
24382 sufficient. In some cases there will be name clashes within a program
24383 (particularly if the executable itself includes full debugging symbols)
24384 necessitating the use of the fully qualified name when referring to the
24385 contents of the DLL. Use single-quotes around the name to avoid the
24386 exclamation mark (``!'') being interpreted as a language operator.
24388 Note that the internal name of the DLL may be all upper-case, even
24389 though the file name of the DLL is lower-case, or vice-versa. Since
24390 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24391 some confusion. If in doubt, try the @code{info functions} and
24392 @code{info variables} commands or even @code{maint print msymbols}
24393 (@pxref{Symbols}). Here's an example:
24396 (@value{GDBP}) info function CreateFileA
24397 All functions matching regular expression "CreateFileA":
24399 Non-debugging symbols:
24400 0x77e885f4 CreateFileA
24401 0x77e885f4 KERNEL32!CreateFileA
24405 (@value{GDBP}) info function !
24406 All functions matching regular expression "!":
24408 Non-debugging symbols:
24409 0x6100114c cygwin1!__assert
24410 0x61004034 cygwin1!_dll_crt0@@0
24411 0x61004240 cygwin1!dll_crt0(per_process *)
24415 @subsubsection Working with Minimal Symbols
24417 Symbols extracted from a DLL's export table do not contain very much
24418 type information. All that @value{GDBN} can do is guess whether a symbol
24419 refers to a function or variable depending on the linker section that
24420 contains the symbol. Also note that the actual contents of the memory
24421 contained in a DLL are not available unless the program is running. This
24422 means that you cannot examine the contents of a variable or disassemble
24423 a function within a DLL without a running program.
24425 Variables are generally treated as pointers and dereferenced
24426 automatically. For this reason, it is often necessary to prefix a
24427 variable name with the address-of operator (``&'') and provide explicit
24428 type information in the command. Here's an example of the type of
24432 (@value{GDBP}) print 'cygwin1!__argv'
24433 'cygwin1!__argv' has unknown type; cast it to its declared type
24437 (@value{GDBP}) x 'cygwin1!__argv'
24438 'cygwin1!__argv' has unknown type; cast it to its declared type
24441 And two possible solutions:
24444 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24445 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24449 (@value{GDBP}) x/2x &'cygwin1!__argv'
24450 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24451 (@value{GDBP}) x/x 0x10021608
24452 0x10021608: 0x0022fd98
24453 (@value{GDBP}) x/s 0x0022fd98
24454 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24457 Setting a break point within a DLL is possible even before the program
24458 starts execution. However, under these circumstances, @value{GDBN} can't
24459 examine the initial instructions of the function in order to skip the
24460 function's frame set-up code. You can work around this by using ``*&''
24461 to set the breakpoint at a raw memory address:
24464 (@value{GDBP}) break *&'python22!PyOS_Readline'
24465 Breakpoint 1 at 0x1e04eff0
24468 The author of these extensions is not entirely convinced that setting a
24469 break point within a shared DLL like @file{kernel32.dll} is completely
24473 @subsection Commands Specific to @sc{gnu} Hurd Systems
24474 @cindex @sc{gnu} Hurd debugging
24476 This subsection describes @value{GDBN} commands specific to the
24477 @sc{gnu} Hurd native debugging.
24482 @kindex set signals@r{, Hurd command}
24483 @kindex set sigs@r{, Hurd command}
24484 This command toggles the state of inferior signal interception by
24485 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24486 affected by this command. @code{sigs} is a shorthand alias for
24491 @kindex show signals@r{, Hurd command}
24492 @kindex show sigs@r{, Hurd command}
24493 Show the current state of intercepting inferior's signals.
24495 @item set signal-thread
24496 @itemx set sigthread
24497 @kindex set signal-thread
24498 @kindex set sigthread
24499 This command tells @value{GDBN} which thread is the @code{libc} signal
24500 thread. That thread is run when a signal is delivered to a running
24501 process. @code{set sigthread} is the shorthand alias of @code{set
24504 @item show signal-thread
24505 @itemx show sigthread
24506 @kindex show signal-thread
24507 @kindex show sigthread
24508 These two commands show which thread will run when the inferior is
24509 delivered a signal.
24512 @kindex set stopped@r{, Hurd command}
24513 This commands tells @value{GDBN} that the inferior process is stopped,
24514 as with the @code{SIGSTOP} signal. The stopped process can be
24515 continued by delivering a signal to it.
24518 @kindex show stopped@r{, Hurd command}
24519 This command shows whether @value{GDBN} thinks the debuggee is
24522 @item set exceptions
24523 @kindex set exceptions@r{, Hurd command}
24524 Use this command to turn off trapping of exceptions in the inferior.
24525 When exception trapping is off, neither breakpoints nor
24526 single-stepping will work. To restore the default, set exception
24529 @item show exceptions
24530 @kindex show exceptions@r{, Hurd command}
24531 Show the current state of trapping exceptions in the inferior.
24533 @item set task pause
24534 @kindex set task@r{, Hurd commands}
24535 @cindex task attributes (@sc{gnu} Hurd)
24536 @cindex pause current task (@sc{gnu} Hurd)
24537 This command toggles task suspension when @value{GDBN} has control.
24538 Setting it to on takes effect immediately, and the task is suspended
24539 whenever @value{GDBN} gets control. Setting it to off will take
24540 effect the next time the inferior is continued. If this option is set
24541 to off, you can use @code{set thread default pause on} or @code{set
24542 thread pause on} (see below) to pause individual threads.
24544 @item show task pause
24545 @kindex show task@r{, Hurd commands}
24546 Show the current state of task suspension.
24548 @item set task detach-suspend-count
24549 @cindex task suspend count
24550 @cindex detach from task, @sc{gnu} Hurd
24551 This command sets the suspend count the task will be left with when
24552 @value{GDBN} detaches from it.
24554 @item show task detach-suspend-count
24555 Show the suspend count the task will be left with when detaching.
24557 @item set task exception-port
24558 @itemx set task excp
24559 @cindex task exception port, @sc{gnu} Hurd
24560 This command sets the task exception port to which @value{GDBN} will
24561 forward exceptions. The argument should be the value of the @dfn{send
24562 rights} of the task. @code{set task excp} is a shorthand alias.
24564 @item set noninvasive
24565 @cindex noninvasive task options
24566 This command switches @value{GDBN} to a mode that is the least
24567 invasive as far as interfering with the inferior is concerned. This
24568 is the same as using @code{set task pause}, @code{set exceptions}, and
24569 @code{set signals} to values opposite to the defaults.
24571 @item info send-rights
24572 @itemx info receive-rights
24573 @itemx info port-rights
24574 @itemx info port-sets
24575 @itemx info dead-names
24578 @cindex send rights, @sc{gnu} Hurd
24579 @cindex receive rights, @sc{gnu} Hurd
24580 @cindex port rights, @sc{gnu} Hurd
24581 @cindex port sets, @sc{gnu} Hurd
24582 @cindex dead names, @sc{gnu} Hurd
24583 These commands display information about, respectively, send rights,
24584 receive rights, port rights, port sets, and dead names of a task.
24585 There are also shorthand aliases: @code{info ports} for @code{info
24586 port-rights} and @code{info psets} for @code{info port-sets}.
24588 @item set thread pause
24589 @kindex set thread@r{, Hurd command}
24590 @cindex thread properties, @sc{gnu} Hurd
24591 @cindex pause current thread (@sc{gnu} Hurd)
24592 This command toggles current thread suspension when @value{GDBN} has
24593 control. Setting it to on takes effect immediately, and the current
24594 thread is suspended whenever @value{GDBN} gets control. Setting it to
24595 off will take effect the next time the inferior is continued.
24596 Normally, this command has no effect, since when @value{GDBN} has
24597 control, the whole task is suspended. However, if you used @code{set
24598 task pause off} (see above), this command comes in handy to suspend
24599 only the current thread.
24601 @item show thread pause
24602 @kindex show thread@r{, Hurd command}
24603 This command shows the state of current thread suspension.
24605 @item set thread run
24606 This command sets whether the current thread is allowed to run.
24608 @item show thread run
24609 Show whether the current thread is allowed to run.
24611 @item set thread detach-suspend-count
24612 @cindex thread suspend count, @sc{gnu} Hurd
24613 @cindex detach from thread, @sc{gnu} Hurd
24614 This command sets the suspend count @value{GDBN} will leave on a
24615 thread when detaching. This number is relative to the suspend count
24616 found by @value{GDBN} when it notices the thread; use @code{set thread
24617 takeover-suspend-count} to force it to an absolute value.
24619 @item show thread detach-suspend-count
24620 Show the suspend count @value{GDBN} will leave on the thread when
24623 @item set thread exception-port
24624 @itemx set thread excp
24625 Set the thread exception port to which to forward exceptions. This
24626 overrides the port set by @code{set task exception-port} (see above).
24627 @code{set thread excp} is the shorthand alias.
24629 @item set thread takeover-suspend-count
24630 Normally, @value{GDBN}'s thread suspend counts are relative to the
24631 value @value{GDBN} finds when it notices each thread. This command
24632 changes the suspend counts to be absolute instead.
24634 @item set thread default
24635 @itemx show thread default
24636 @cindex thread default settings, @sc{gnu} Hurd
24637 Each of the above @code{set thread} commands has a @code{set thread
24638 default} counterpart (e.g., @code{set thread default pause}, @code{set
24639 thread default exception-port}, etc.). The @code{thread default}
24640 variety of commands sets the default thread properties for all
24641 threads; you can then change the properties of individual threads with
24642 the non-default commands.
24649 @value{GDBN} provides the following commands specific to the Darwin target:
24652 @item set debug darwin @var{num}
24653 @kindex set debug darwin
24654 When set to a non zero value, enables debugging messages specific to
24655 the Darwin support. Higher values produce more verbose output.
24657 @item show debug darwin
24658 @kindex show debug darwin
24659 Show the current state of Darwin messages.
24661 @item set debug mach-o @var{num}
24662 @kindex set debug mach-o
24663 When set to a non zero value, enables debugging messages while
24664 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24665 file format used on Darwin for object and executable files.) Higher
24666 values produce more verbose output. This is a command to diagnose
24667 problems internal to @value{GDBN} and should not be needed in normal
24670 @item show debug mach-o
24671 @kindex show debug mach-o
24672 Show the current state of Mach-O file messages.
24674 @item set mach-exceptions on
24675 @itemx set mach-exceptions off
24676 @kindex set mach-exceptions
24677 On Darwin, faults are first reported as a Mach exception and are then
24678 mapped to a Posix signal. Use this command to turn on trapping of
24679 Mach exceptions in the inferior. This might be sometimes useful to
24680 better understand the cause of a fault. The default is off.
24682 @item show mach-exceptions
24683 @kindex show mach-exceptions
24684 Show the current state of exceptions trapping.
24688 @subsection FreeBSD
24691 When the ABI of a system call is changed in the FreeBSD kernel, this
24692 is implemented by leaving a compatibility system call using the old
24693 ABI at the existing number and allocating a new system call number for
24694 the version using the new ABI. As a convenience, when a system call
24695 is caught by name (@pxref{catch syscall}), compatibility system calls
24698 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24699 system call and catching the @code{kevent} system call by name catches
24703 (@value{GDBP}) catch syscall kevent
24704 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24710 @section Embedded Operating Systems
24712 This section describes configurations involving the debugging of
24713 embedded operating systems that are available for several different
24716 @value{GDBN} includes the ability to debug programs running on
24717 various real-time operating systems.
24719 @node Embedded Processors
24720 @section Embedded Processors
24722 This section goes into details specific to particular embedded
24725 @cindex send command to simulator
24726 Whenever a specific embedded processor has a simulator, @value{GDBN}
24727 allows to send an arbitrary command to the simulator.
24730 @item sim @var{command}
24731 @kindex sim@r{, a command}
24732 Send an arbitrary @var{command} string to the simulator. Consult the
24733 documentation for the specific simulator in use for information about
24734 acceptable commands.
24739 * ARC:: Synopsys ARC
24742 * M68K:: Motorola M68K
24743 * MicroBlaze:: Xilinx MicroBlaze
24744 * MIPS Embedded:: MIPS Embedded
24745 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24746 * PowerPC Embedded:: PowerPC Embedded
24749 * Super-H:: Renesas Super-H
24753 @subsection Synopsys ARC
24754 @cindex Synopsys ARC
24755 @cindex ARC specific commands
24761 @value{GDBN} provides the following ARC-specific commands:
24764 @item set debug arc
24765 @kindex set debug arc
24766 Control the level of ARC specific debug messages. Use 0 for no messages (the
24767 default), 1 for debug messages, and 2 for even more debug messages.
24769 @item show debug arc
24770 @kindex show debug arc
24771 Show the level of ARC specific debugging in operation.
24773 @item maint print arc arc-instruction @var{address}
24774 @kindex maint print arc arc-instruction
24775 Print internal disassembler information about instruction at a given address.
24782 @value{GDBN} provides the following ARM-specific commands:
24785 @item set arm disassembler
24787 This commands selects from a list of disassembly styles. The
24788 @code{"std"} style is the standard style.
24790 @item show arm disassembler
24792 Show the current disassembly style.
24794 @item set arm apcs32
24795 @cindex ARM 32-bit mode
24796 This command toggles ARM operation mode between 32-bit and 26-bit.
24798 @item show arm apcs32
24799 Display the current usage of the ARM 32-bit mode.
24801 @item set arm fpu @var{fputype}
24802 This command sets the ARM floating-point unit (FPU) type. The
24803 argument @var{fputype} can be one of these:
24807 Determine the FPU type by querying the OS ABI.
24809 Software FPU, with mixed-endian doubles on little-endian ARM
24812 GCC-compiled FPA co-processor.
24814 Software FPU with pure-endian doubles.
24820 Show the current type of the FPU.
24823 This command forces @value{GDBN} to use the specified ABI.
24826 Show the currently used ABI.
24828 @item set arm fallback-mode (arm|thumb|auto)
24829 @value{GDBN} uses the symbol table, when available, to determine
24830 whether instructions are ARM or Thumb. This command controls
24831 @value{GDBN}'s default behavior when the symbol table is not
24832 available. The default is @samp{auto}, which causes @value{GDBN} to
24833 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24836 @item show arm fallback-mode
24837 Show the current fallback instruction mode.
24839 @item set arm force-mode (arm|thumb|auto)
24840 This command overrides use of the symbol table to determine whether
24841 instructions are ARM or Thumb. The default is @samp{auto}, which
24842 causes @value{GDBN} to use the symbol table and then the setting
24843 of @samp{set arm fallback-mode}.
24845 @item show arm force-mode
24846 Show the current forced instruction mode.
24848 @item set debug arm
24849 Toggle whether to display ARM-specific debugging messages from the ARM
24850 target support subsystem.
24852 @item show debug arm
24853 Show whether ARM-specific debugging messages are enabled.
24857 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24858 The @value{GDBN} ARM simulator accepts the following optional arguments.
24861 @item --swi-support=@var{type}
24862 Tell the simulator which SWI interfaces to support. The argument
24863 @var{type} may be a comma separated list of the following values.
24864 The default value is @code{all}.
24880 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24881 The @value{GDBN} BPF simulator accepts the following optional arguments.
24884 @item --skb-data-offset=@var{offset}
24885 Tell the simulator the offset, measured in bytes, of the
24886 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
24887 This offset is used by some BPF specific-purpose load/store
24888 instructions. Defaults to 0.
24895 The Motorola m68k configuration includes ColdFire support.
24898 @subsection MicroBlaze
24899 @cindex Xilinx MicroBlaze
24900 @cindex XMD, Xilinx Microprocessor Debugger
24902 The MicroBlaze is a soft-core processor supported on various Xilinx
24903 FPGAs, such as Spartan or Virtex series. Boards with these processors
24904 usually have JTAG ports which connect to a host system running the Xilinx
24905 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24906 This host system is used to download the configuration bitstream to
24907 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24908 communicates with the target board using the JTAG interface and
24909 presents a @code{gdbserver} interface to the board. By default
24910 @code{xmd} uses port @code{1234}. (While it is possible to change
24911 this default port, it requires the use of undocumented @code{xmd}
24912 commands. Contact Xilinx support if you need to do this.)
24914 Use these GDB commands to connect to the MicroBlaze target processor.
24917 @item target remote :1234
24918 Use this command to connect to the target if you are running @value{GDBN}
24919 on the same system as @code{xmd}.
24921 @item target remote @var{xmd-host}:1234
24922 Use this command to connect to the target if it is connected to @code{xmd}
24923 running on a different system named @var{xmd-host}.
24926 Use this command to download a program to the MicroBlaze target.
24928 @item set debug microblaze @var{n}
24929 Enable MicroBlaze-specific debugging messages if non-zero.
24931 @item show debug microblaze @var{n}
24932 Show MicroBlaze-specific debugging level.
24935 @node MIPS Embedded
24936 @subsection @acronym{MIPS} Embedded
24939 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24942 @item set mipsfpu double
24943 @itemx set mipsfpu single
24944 @itemx set mipsfpu none
24945 @itemx set mipsfpu auto
24946 @itemx show mipsfpu
24947 @kindex set mipsfpu
24948 @kindex show mipsfpu
24949 @cindex @acronym{MIPS} remote floating point
24950 @cindex floating point, @acronym{MIPS} remote
24951 If your target board does not support the @acronym{MIPS} floating point
24952 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24953 need this, you may wish to put the command in your @value{GDBN} init
24954 file). This tells @value{GDBN} how to find the return value of
24955 functions which return floating point values. It also allows
24956 @value{GDBN} to avoid saving the floating point registers when calling
24957 functions on the board. If you are using a floating point coprocessor
24958 with only single precision floating point support, as on the @sc{r4650}
24959 processor, use the command @samp{set mipsfpu single}. The default
24960 double precision floating point coprocessor may be selected using
24961 @samp{set mipsfpu double}.
24963 In previous versions the only choices were double precision or no
24964 floating point, so @samp{set mipsfpu on} will select double precision
24965 and @samp{set mipsfpu off} will select no floating point.
24967 As usual, you can inquire about the @code{mipsfpu} variable with
24968 @samp{show mipsfpu}.
24971 @node OpenRISC 1000
24972 @subsection OpenRISC 1000
24973 @cindex OpenRISC 1000
24976 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24977 mainly provided as a soft-core which can run on Xilinx, Altera and other
24980 @value{GDBN} for OpenRISC supports the below commands when connecting to
24988 Runs the builtin CPU simulator which can run very basic
24989 programs but does not support most hardware functions like MMU.
24990 For more complex use cases the user is advised to run an external
24991 target, and connect using @samp{target remote}.
24993 Example: @code{target sim}
24995 @item set debug or1k
24996 Toggle whether to display OpenRISC-specific debugging messages from the
24997 OpenRISC target support subsystem.
24999 @item show debug or1k
25000 Show whether OpenRISC-specific debugging messages are enabled.
25003 @node PowerPC Embedded
25004 @subsection PowerPC Embedded
25006 @cindex DVC register
25007 @value{GDBN} supports using the DVC (Data Value Compare) register to
25008 implement in hardware simple hardware watchpoint conditions of the form:
25011 (@value{GDBP}) watch @var{address|variable} \
25012 if @var{address|variable} == @var{constant expression}
25015 The DVC register will be automatically used when @value{GDBN} detects
25016 such pattern in a condition expression, and the created watchpoint uses one
25017 debug register (either the @code{exact-watchpoints} option is on and the
25018 variable is scalar, or the variable has a length of one byte). This feature
25019 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25022 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25023 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25024 in which case watchpoints using only one debug register are created when
25025 watching variables of scalar types.
25027 You can create an artificial array to watch an arbitrary memory
25028 region using one of the following commands (@pxref{Expressions}):
25031 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25032 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25035 PowerPC embedded processors support masked watchpoints. See the discussion
25036 about the @code{mask} argument in @ref{Set Watchpoints}.
25038 @cindex ranged breakpoint
25039 PowerPC embedded processors support hardware accelerated
25040 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25041 the inferior whenever it executes an instruction at any address within
25042 the range it specifies. To set a ranged breakpoint in @value{GDBN},
25043 use the @code{break-range} command.
25045 @value{GDBN} provides the following PowerPC-specific commands:
25048 @kindex break-range
25049 @item break-range @var{start-location}, @var{end-location}
25050 Set a breakpoint for an address range given by
25051 @var{start-location} and @var{end-location}, which can specify a function name,
25052 a line number, an offset of lines from the current line or from the start
25053 location, or an address of an instruction (see @ref{Specify Location},
25054 for a list of all the possible ways to specify a @var{location}.)
25055 The breakpoint will stop execution of the inferior whenever it
25056 executes an instruction at any address within the specified range,
25057 (including @var{start-location} and @var{end-location}.)
25059 @kindex set powerpc
25060 @item set powerpc soft-float
25061 @itemx show powerpc soft-float
25062 Force @value{GDBN} to use (or not use) a software floating point calling
25063 convention. By default, @value{GDBN} selects the calling convention based
25064 on the selected architecture and the provided executable file.
25066 @item set powerpc vector-abi
25067 @itemx show powerpc vector-abi
25068 Force @value{GDBN} to use the specified calling convention for vector
25069 arguments and return values. The valid options are @samp{auto};
25070 @samp{generic}, to avoid vector registers even if they are present;
25071 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25072 registers. By default, @value{GDBN} selects the calling convention
25073 based on the selected architecture and the provided executable file.
25075 @item set powerpc exact-watchpoints
25076 @itemx show powerpc exact-watchpoints
25077 Allow @value{GDBN} to use only one debug register when watching a variable
25078 of scalar type, thus assuming that the variable is accessed through the
25079 address of its first byte.
25084 @subsection Atmel AVR
25087 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25088 following AVR-specific commands:
25091 @item info io_registers
25092 @kindex info io_registers@r{, AVR}
25093 @cindex I/O registers (Atmel AVR)
25094 This command displays information about the AVR I/O registers. For
25095 each register, @value{GDBN} prints its number and value.
25102 When configured for debugging CRIS, @value{GDBN} provides the
25103 following CRIS-specific commands:
25106 @item set cris-version @var{ver}
25107 @cindex CRIS version
25108 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25109 The CRIS version affects register names and sizes. This command is useful in
25110 case autodetection of the CRIS version fails.
25112 @item show cris-version
25113 Show the current CRIS version.
25115 @item set cris-dwarf2-cfi
25116 @cindex DWARF-2 CFI and CRIS
25117 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25118 Change to @samp{off} when using @code{gcc-cris} whose version is below
25121 @item show cris-dwarf2-cfi
25122 Show the current state of using DWARF-2 CFI.
25124 @item set cris-mode @var{mode}
25126 Set the current CRIS mode to @var{mode}. It should only be changed when
25127 debugging in guru mode, in which case it should be set to
25128 @samp{guru} (the default is @samp{normal}).
25130 @item show cris-mode
25131 Show the current CRIS mode.
25135 @subsection Renesas Super-H
25138 For the Renesas Super-H processor, @value{GDBN} provides these
25142 @item set sh calling-convention @var{convention}
25143 @kindex set sh calling-convention
25144 Set the calling-convention used when calling functions from @value{GDBN}.
25145 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25146 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25147 convention. If the DWARF-2 information of the called function specifies
25148 that the function follows the Renesas calling convention, the function
25149 is called using the Renesas calling convention. If the calling convention
25150 is set to @samp{renesas}, the Renesas calling convention is always used,
25151 regardless of the DWARF-2 information. This can be used to override the
25152 default of @samp{gcc} if debug information is missing, or the compiler
25153 does not emit the DWARF-2 calling convention entry for a function.
25155 @item show sh calling-convention
25156 @kindex show sh calling-convention
25157 Show the current calling convention setting.
25162 @node Architectures
25163 @section Architectures
25165 This section describes characteristics of architectures that affect
25166 all uses of @value{GDBN} with the architecture, both native and cross.
25173 * HPPA:: HP PA architecture
25181 @subsection AArch64
25182 @cindex AArch64 support
25184 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25185 following special commands:
25188 @item set debug aarch64
25189 @kindex set debug aarch64
25190 This command determines whether AArch64 architecture-specific debugging
25191 messages are to be displayed.
25193 @item show debug aarch64
25194 Show whether AArch64 debugging messages are displayed.
25198 @subsubsection AArch64 SVE.
25199 @cindex AArch64 SVE.
25201 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25202 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25203 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25204 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25205 @code{$vg} will be provided. This is the vector granule for the current thread
25206 and represents the number of 64-bit chunks in an SVE @code{z} register.
25208 If the vector length changes, then the @code{$vg} register will be updated,
25209 but the lengths of the @code{z} and @code{p} registers will not change. This
25210 is a known limitation of @value{GDBN} and does not affect the execution of the
25213 @subsubsection AArch64 Pointer Authentication.
25214 @cindex AArch64 Pointer Authentication.
25216 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25217 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25218 register @code{$lr} is pointing to an PAC function its value will be masked.
25219 When GDB prints a backtrace, any addresses that required unmasking will be
25220 postfixed with the marker [PAC]. When using the MI, this is printed as part
25221 of the @code{addr_flags} field.
25223 @subsubsection AArch64 Memory Tagging Extension.
25224 @cindex AArch64 Memory Tagging Extension.
25226 When @value{GDBN} is debugging the AArch64 architecture, the program is
25227 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25228 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25229 available for inspection and editing of logical and allocation tags.
25230 @xref{Memory Tagging}.
25232 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25233 signals are generated as a result of memory tag failures.
25235 If the tag violation is synchronous, the following will be shown:
25238 Program received signal SIGSEGV, Segmentation fault
25239 Memory tag violation while accessing address 0x0500fffff7ff8000
25244 If the tag violation is asynchronous, the fault address is not available.
25245 In this case @value{GDBN} will show the following:
25248 Program received signal SIGSEGV, Segmentation fault
25249 Memory tag violation
25250 Fault address unavailable.
25253 A special register, @code{tag_ctl}, is made available through the
25254 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25255 options that can be controlled at runtime and emulates the @code{prctl}
25256 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25257 documentation in the Linux kernel.
25260 @subsection x86 Architecture-specific Issues
25263 @item set struct-convention @var{mode}
25264 @kindex set struct-convention
25265 @cindex struct return convention
25266 @cindex struct/union returned in registers
25267 Set the convention used by the inferior to return @code{struct}s and
25268 @code{union}s from functions to @var{mode}. Possible values of
25269 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25270 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25271 are returned on the stack, while @code{"reg"} means that a
25272 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25273 be returned in a register.
25275 @item show struct-convention
25276 @kindex show struct-convention
25277 Show the current setting of the convention to return @code{struct}s
25282 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25283 @cindex Intel Memory Protection Extensions (MPX).
25285 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25286 @footnote{The register named with capital letters represent the architecture
25287 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25288 which are the lower bound and upper bound. Bounds are effective addresses or
25289 memory locations. The upper bounds are architecturally represented in 1's
25290 complement form. A bound having lower bound = 0, and upper bound = 0
25291 (1's complement of all bits set) will allow access to the entire address space.
25293 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25294 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25295 display the upper bound performing the complement of one operation on the
25296 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25297 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25298 can also be noted that the upper bounds are inclusive.
25300 As an example, assume that the register BND0 holds bounds for a pointer having
25301 access allowed for the range between 0x32 and 0x71. The values present on
25302 bnd0raw and bnd registers are presented as follows:
25305 bnd0raw = @{0x32, 0xffffffff8e@}
25306 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25309 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25310 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25311 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25312 Python, the display includes the memory size, in bits, accessible to
25315 Bounds can also be stored in bounds tables, which are stored in
25316 application memory. These tables store bounds for pointers by specifying
25317 the bounds pointer's value along with its bounds. Evaluating and changing
25318 bounds located in bound tables is therefore interesting while investigating
25319 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25322 @item show mpx bound @var{pointer}
25323 @kindex show mpx bound
25324 Display bounds of the given @var{pointer}.
25326 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25327 @kindex set mpx bound
25328 Set the bounds of a pointer in the bound table.
25329 This command takes three parameters: @var{pointer} is the pointers
25330 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25331 for lower and upper bounds respectively.
25334 When you call an inferior function on an Intel MPX enabled program,
25335 GDB sets the inferior's bound registers to the init (disabled) state
25336 before calling the function. As a consequence, bounds checks for the
25337 pointer arguments passed to the function will always pass.
25339 This is necessary because when you call an inferior function, the
25340 program is usually in the middle of the execution of other function.
25341 Since at that point bound registers are in an arbitrary state, not
25342 clearing them would lead to random bound violations in the called
25345 You can still examine the influence of the bound registers on the
25346 execution of the called function by stopping the execution of the
25347 called function at its prologue, setting bound registers, and
25348 continuing the execution. For example:
25352 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25353 $ print upper (a, b, c, d, 1)
25354 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25356 @{lbound = 0x0, ubound = ffffffff@} : size -1
25359 At this last step the value of bnd0 can be changed for investigation of bound
25360 violations caused along the execution of the call. In order to know how to
25361 set the bound registers or bound table for the call consult the ABI.
25366 See the following section.
25369 @subsection @acronym{MIPS}
25371 @cindex stack on Alpha
25372 @cindex stack on @acronym{MIPS}
25373 @cindex Alpha stack
25374 @cindex @acronym{MIPS} stack
25375 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25376 sometimes requires @value{GDBN} to search backward in the object code to
25377 find the beginning of a function.
25379 @cindex response time, @acronym{MIPS} debugging
25380 To improve response time (especially for embedded applications, where
25381 @value{GDBN} may be restricted to a slow serial line for this search)
25382 you may want to limit the size of this search, using one of these
25386 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25387 @item set heuristic-fence-post @var{limit}
25388 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25389 search for the beginning of a function. A value of @var{0} (the
25390 default) means there is no limit. However, except for @var{0}, the
25391 larger the limit the more bytes @code{heuristic-fence-post} must search
25392 and therefore the longer it takes to run. You should only need to use
25393 this command when debugging a stripped executable.
25395 @item show heuristic-fence-post
25396 Display the current limit.
25400 These commands are available @emph{only} when @value{GDBN} is configured
25401 for debugging programs on Alpha or @acronym{MIPS} processors.
25403 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25407 @item set mips abi @var{arg}
25408 @kindex set mips abi
25409 @cindex set ABI for @acronym{MIPS}
25410 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25411 values of @var{arg} are:
25415 The default ABI associated with the current binary (this is the
25425 @item show mips abi
25426 @kindex show mips abi
25427 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25429 @item set mips compression @var{arg}
25430 @kindex set mips compression
25431 @cindex code compression, @acronym{MIPS}
25432 Tell @value{GDBN} which @acronym{MIPS} compressed
25433 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25434 inferior. @value{GDBN} uses this for code disassembly and other
25435 internal interpretation purposes. This setting is only referred to
25436 when no executable has been associated with the debugging session or
25437 the executable does not provide information about the encoding it uses.
25438 Otherwise this setting is automatically updated from information
25439 provided by the executable.
25441 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25442 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25443 executables containing @acronym{MIPS16} code frequently are not
25444 identified as such.
25446 This setting is ``sticky''; that is, it retains its value across
25447 debugging sessions until reset either explicitly with this command or
25448 implicitly from an executable.
25450 The compiler and/or assembler typically add symbol table annotations to
25451 identify functions compiled for the @acronym{MIPS16} or
25452 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25453 are present, @value{GDBN} uses them in preference to the global
25454 compressed @acronym{ISA} encoding setting.
25456 @item show mips compression
25457 @kindex show mips compression
25458 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25459 @value{GDBN} to debug the inferior.
25462 @itemx show mipsfpu
25463 @xref{MIPS Embedded, set mipsfpu}.
25465 @item set mips mask-address @var{arg}
25466 @kindex set mips mask-address
25467 @cindex @acronym{MIPS} addresses, masking
25468 This command determines whether the most-significant 32 bits of 64-bit
25469 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25470 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25471 setting, which lets @value{GDBN} determine the correct value.
25473 @item show mips mask-address
25474 @kindex show mips mask-address
25475 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25478 @item set remote-mips64-transfers-32bit-regs
25479 @kindex set remote-mips64-transfers-32bit-regs
25480 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25481 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25482 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25483 and 64 bits for other registers, set this option to @samp{on}.
25485 @item show remote-mips64-transfers-32bit-regs
25486 @kindex show remote-mips64-transfers-32bit-regs
25487 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25489 @item set debug mips
25490 @kindex set debug mips
25491 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25492 target code in @value{GDBN}.
25494 @item show debug mips
25495 @kindex show debug mips
25496 Show the current setting of @acronym{MIPS} debugging messages.
25502 @cindex HPPA support
25504 When @value{GDBN} is debugging the HP PA architecture, it provides the
25505 following special commands:
25508 @item set debug hppa
25509 @kindex set debug hppa
25510 This command determines whether HPPA architecture-specific debugging
25511 messages are to be displayed.
25513 @item show debug hppa
25514 Show whether HPPA debugging messages are displayed.
25516 @item maint print unwind @var{address}
25517 @kindex maint print unwind@r{, HPPA}
25518 This command displays the contents of the unwind table entry at the
25519 given @var{address}.
25525 @subsection PowerPC
25526 @cindex PowerPC architecture
25528 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25529 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25530 numbers stored in the floating point registers. These values must be stored
25531 in two consecutive registers, always starting at an even register like
25532 @code{f0} or @code{f2}.
25534 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25535 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25536 @code{f2} and @code{f3} for @code{$dl1} and so on.
25538 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25539 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25542 @subsection Nios II
25543 @cindex Nios II architecture
25545 When @value{GDBN} is debugging the Nios II architecture,
25546 it provides the following special commands:
25550 @item set debug nios2
25551 @kindex set debug nios2
25552 This command turns on and off debugging messages for the Nios II
25553 target code in @value{GDBN}.
25555 @item show debug nios2
25556 @kindex show debug nios2
25557 Show the current setting of Nios II debugging messages.
25561 @subsection Sparc64
25562 @cindex Sparc64 support
25563 @cindex Application Data Integrity
25564 @subsubsection ADI Support
25566 The M7 processor supports an Application Data Integrity (ADI) feature that
25567 detects invalid data accesses. When software allocates memory and enables
25568 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25569 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25570 the 4-bit version in every cacheline of that data. Hardware saves the latter
25571 in spare bits in the cache and memory hierarchy. On each load and store,
25572 the processor compares the upper 4 VA (virtual address) bits to the
25573 cacheline's version. If there is a mismatch, the processor generates a
25574 version mismatch trap which can be either precise or disrupting. The trap
25575 is an error condition which the kernel delivers to the process as a SIGSEGV
25578 Note that only 64-bit applications can use ADI and need to be built with
25581 Values of the ADI version tags, which are in granularity of a
25582 cacheline (64 bytes), can be viewed or modified.
25586 @kindex adi examine
25587 @item adi (examine | x) [ / @var{n} ] @var{addr}
25589 The @code{adi examine} command displays the value of one ADI version tag per
25592 @var{n} is a decimal integer specifying the number in bytes; the default
25593 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25594 block size, to display.
25596 @var{addr} is the address in user address space where you want @value{GDBN}
25597 to begin displaying the ADI version tags.
25599 Below is an example of displaying ADI versions of variable "shmaddr".
25602 (@value{GDBP}) adi x/100 shmaddr
25603 0xfff800010002c000: 0 0
25607 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25609 The @code{adi assign} command is used to assign new ADI version tag
25612 @var{n} is a decimal integer specifying the number in bytes;
25613 the default is 1. It specifies how much ADI version information, at the
25614 ratio of 1:ADI block size, to modify.
25616 @var{addr} is the address in user address space where you want @value{GDBN}
25617 to begin modifying the ADI version tags.
25619 @var{tag} is the new ADI version tag.
25621 For example, do the following to modify then verify ADI versions of
25622 variable "shmaddr":
25625 (@value{GDBP}) adi a/100 shmaddr = 7
25626 (@value{GDBP}) adi x/100 shmaddr
25627 0xfff800010002c000: 7 7
25634 @cindex S12Z support
25636 When @value{GDBN} is debugging the S12Z architecture,
25637 it provides the following special command:
25640 @item maint info bdccsr
25641 @kindex maint info bdccsr@r{, S12Z}
25642 This command displays the current value of the microprocessor's
25647 @node Controlling GDB
25648 @chapter Controlling @value{GDBN}
25650 You can alter the way @value{GDBN} interacts with you by using the
25651 @code{set} command. For commands controlling how @value{GDBN} displays
25652 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25657 * Editing:: Command editing
25658 * Command History:: Command history
25659 * Screen Size:: Screen size
25660 * Output Styling:: Output styling
25661 * Numbers:: Numbers
25662 * ABI:: Configuring the current ABI
25663 * Auto-loading:: Automatically loading associated files
25664 * Messages/Warnings:: Optional warnings and messages
25665 * Debugging Output:: Optional messages about internal happenings
25666 * Other Misc Settings:: Other Miscellaneous Settings
25674 @value{GDBN} indicates its readiness to read a command by printing a string
25675 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25676 can change the prompt string with the @code{set prompt} command. For
25677 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25678 the prompt in one of the @value{GDBN} sessions so that you can always tell
25679 which one you are talking to.
25681 @emph{Note:} @code{set prompt} does not add a space for you after the
25682 prompt you set. This allows you to set a prompt which ends in a space
25683 or a prompt that does not.
25687 @item set prompt @var{newprompt}
25688 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25690 @kindex show prompt
25692 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25695 Versions of @value{GDBN} that ship with Python scripting enabled have
25696 prompt extensions. The commands for interacting with these extensions
25700 @kindex set extended-prompt
25701 @item set extended-prompt @var{prompt}
25702 Set an extended prompt that allows for substitutions.
25703 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25704 substitution. Any escape sequences specified as part of the prompt
25705 string are replaced with the corresponding strings each time the prompt
25711 set extended-prompt Current working directory: \w (gdb)
25714 Note that when an extended-prompt is set, it takes control of the
25715 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25717 @kindex show extended-prompt
25718 @item show extended-prompt
25719 Prints the extended prompt. Any escape sequences specified as part of
25720 the prompt string with @code{set extended-prompt}, are replaced with the
25721 corresponding strings each time the prompt is displayed.
25725 @section Command Editing
25727 @cindex command line editing
25729 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25730 @sc{gnu} library provides consistent behavior for programs which provide a
25731 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25732 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25733 substitution, and a storage and recall of command history across
25734 debugging sessions.
25736 You may control the behavior of command line editing in @value{GDBN} with the
25737 command @code{set}.
25740 @kindex set editing
25743 @itemx set editing on
25744 Enable command line editing (enabled by default).
25746 @item set editing off
25747 Disable command line editing.
25749 @kindex show editing
25751 Show whether command line editing is enabled.
25754 @ifset SYSTEM_READLINE
25755 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25757 @ifclear SYSTEM_READLINE
25758 @xref{Command Line Editing},
25760 for more details about the Readline
25761 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25762 encouraged to read that chapter.
25764 @cindex Readline application name
25765 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25766 is useful for conditions in @file{.inputrc}.
25768 @cindex operate-and-get-next
25769 @value{GDBN} defines a bindable Readline command,
25770 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25771 This command accepts the current line for execution and fetches the
25772 next line relative to the current line from the history for editing.
25773 Any argument is ignored.
25775 @node Command History
25776 @section Command History
25777 @cindex command history
25779 @value{GDBN} can keep track of the commands you type during your
25780 debugging sessions, so that you can be certain of precisely what
25781 happened. Use these commands to manage the @value{GDBN} command
25784 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25785 package, to provide the history facility.
25786 @ifset SYSTEM_READLINE
25787 @xref{Using History Interactively, , , history, GNU History Library},
25789 @ifclear SYSTEM_READLINE
25790 @xref{Using History Interactively},
25792 for the detailed description of the History library.
25794 To issue a command to @value{GDBN} without affecting certain aspects of
25795 the state which is seen by users, prefix it with @samp{server }
25796 (@pxref{Server Prefix}). This
25797 means that this command will not affect the command history, nor will it
25798 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25799 pressed on a line by itself.
25801 @cindex @code{server}, command prefix
25802 The server prefix does not affect the recording of values into the value
25803 history; to print a value without recording it into the value history,
25804 use the @code{output} command instead of the @code{print} command.
25806 Here is the description of @value{GDBN} commands related to command
25810 @cindex history substitution
25811 @cindex history file
25812 @kindex set history filename
25813 @cindex @env{GDBHISTFILE}, environment variable
25814 @item set history filename @r{[}@var{fname}@r{]}
25815 Set the name of the @value{GDBN} command history file to @var{fname}.
25816 This is the file where @value{GDBN} reads an initial command history
25817 list, and where it writes the command history from this session when it
25818 exits. You can access this list through history expansion or through
25819 the history command editing characters listed below. This file defaults
25820 to the value of the environment variable @env{GDBHISTFILE}, or to
25821 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25824 The @env{GDBHISTFILE} environment variable is read after processing
25825 any @value{GDBN} initialization files (@pxref{Startup}) and after
25826 processing any commands passed using command line options (for
25827 example, @code{-ex}).
25829 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
25830 is the empty string then @value{GDBN} will neither try to load an
25831 existing history file, nor will it try to save the history on exit.
25833 @cindex save command history
25834 @kindex set history save
25835 @item set history save
25836 @itemx set history save on
25837 Record command history in a file, whose name may be specified with the
25838 @code{set history filename} command. By default, this option is
25839 disabled. The command history will be recorded when @value{GDBN}
25840 exits. If @code{set history filename} is set to the empty string then
25841 history saving is disabled, even when @code{set history save} is
25844 @item set history save off
25845 Don't record the command history into the file specified by @code{set
25846 history filename} when @value{GDBN} exits.
25848 @cindex history size
25849 @kindex set history size
25850 @cindex @env{GDBHISTSIZE}, environment variable
25851 @item set history size @var{size}
25852 @itemx set history size unlimited
25853 Set the number of commands which @value{GDBN} keeps in its history list.
25854 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25855 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25856 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25857 either a negative number or the empty string, then the number of commands
25858 @value{GDBN} keeps in the history list is unlimited.
25860 The @env{GDBHISTSIZE} environment variable is read after processing
25861 any @value{GDBN} initialization files (@pxref{Startup}) and after
25862 processing any commands passed using command line options (for
25863 example, @code{-ex}).
25865 @cindex remove duplicate history
25866 @kindex set history remove-duplicates
25867 @item set history remove-duplicates @var{count}
25868 @itemx set history remove-duplicates unlimited
25869 Control the removal of duplicate history entries in the command history list.
25870 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25871 history entries and remove the first entry that is a duplicate of the current
25872 entry being added to the command history list. If @var{count} is
25873 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25874 removal of duplicate history entries is disabled.
25876 Only history entries added during the current session are considered for
25877 removal. This option is set to 0 by default.
25881 History expansion assigns special meaning to the character @kbd{!}.
25882 @ifset SYSTEM_READLINE
25883 @xref{Event Designators, , , history, GNU History Library},
25885 @ifclear SYSTEM_READLINE
25886 @xref{Event Designators},
25890 @cindex history expansion, turn on/off
25891 Since @kbd{!} is also the logical not operator in C, history expansion
25892 is off by default. If you decide to enable history expansion with the
25893 @code{set history expansion on} command, you may sometimes need to
25894 follow @kbd{!} (when it is used as logical not, in an expression) with
25895 a space or a tab to prevent it from being expanded. The readline
25896 history facilities do not attempt substitution on the strings
25897 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25899 The commands to control history expansion are:
25902 @item set history expansion on
25903 @itemx set history expansion
25904 @kindex set history expansion
25905 Enable history expansion. History expansion is off by default.
25907 @item set history expansion off
25908 Disable history expansion.
25911 @kindex show history
25913 @itemx show history filename
25914 @itemx show history save
25915 @itemx show history size
25916 @itemx show history expansion
25917 These commands display the state of the @value{GDBN} history parameters.
25918 @code{show history} by itself displays all four states.
25923 @kindex show commands
25924 @cindex show last commands
25925 @cindex display command history
25926 @item show commands
25927 Display the last ten commands in the command history.
25929 @item show commands @var{n}
25930 Print ten commands centered on command number @var{n}.
25932 @item show commands +
25933 Print ten commands just after the commands last printed.
25937 @section Screen Size
25938 @cindex size of screen
25939 @cindex screen size
25942 @cindex pauses in output
25944 Certain commands to @value{GDBN} may produce large amounts of
25945 information output to the screen. To help you read all of it,
25946 @value{GDBN} pauses and asks you for input at the end of each page of
25947 output. Type @key{RET} when you want to see one more page of output,
25948 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25949 without paging for the rest of the current command. Also, the screen
25950 width setting determines when to wrap lines of output. Depending on
25951 what is being printed, @value{GDBN} tries to break the line at a
25952 readable place, rather than simply letting it overflow onto the
25955 Normally @value{GDBN} knows the size of the screen from the terminal
25956 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25957 together with the value of the @env{TERM} environment variable and the
25958 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25959 you can override it with the @code{set height} and @code{set
25966 @kindex show height
25967 @item set height @var{lpp}
25968 @itemx set height unlimited
25970 @itemx set width @var{cpl}
25971 @itemx set width unlimited
25973 These @code{set} commands specify a screen height of @var{lpp} lines and
25974 a screen width of @var{cpl} characters. The associated @code{show}
25975 commands display the current settings.
25977 If you specify a height of either @code{unlimited} or zero lines,
25978 @value{GDBN} does not pause during output no matter how long the
25979 output is. This is useful if output is to a file or to an editor
25982 Likewise, you can specify @samp{set width unlimited} or @samp{set
25983 width 0} to prevent @value{GDBN} from wrapping its output.
25985 @item set pagination on
25986 @itemx set pagination off
25987 @kindex set pagination
25988 Turn the output pagination on or off; the default is on. Turning
25989 pagination off is the alternative to @code{set height unlimited}. Note that
25990 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25991 Options, -batch}) also automatically disables pagination.
25993 @item show pagination
25994 @kindex show pagination
25995 Show the current pagination mode.
25998 @node Output Styling
25999 @section Output Styling
26005 @value{GDBN} can style its output on a capable terminal. This is
26006 enabled by default on most systems, but disabled by default when in
26007 batch mode (@pxref{Mode Options}). Various style settings are available;
26008 and styles can also be disabled entirely.
26011 @item set style enabled @samp{on|off}
26012 Enable or disable all styling. The default is host-dependent, with
26013 most hosts defaulting to @samp{on}.
26015 @item show style enabled
26016 Show the current state of styling.
26018 @item set style sources @samp{on|off}
26019 Enable or disable source code styling. This affects whether source
26020 code, such as the output of the @code{list} command, is styled. Note
26021 that source styling only works if styling in general is enabled, and
26022 if @value{GDBN} was linked with the GNU Source Highlight library. The
26023 default is @samp{on}.
26025 @item show style sources
26026 Show the current state of source code styling.
26029 Subcommands of @code{set style} control specific forms of styling.
26030 These subcommands all follow the same pattern: each style-able object
26031 can be styled with a foreground color, a background color, and an
26034 For example, the style of file names can be controlled using the
26035 @code{set style filename} group of commands:
26038 @item set style filename background @var{color}
26039 Set the background to @var{color}. Valid colors are @samp{none}
26040 (meaning the terminal's default color), @samp{black}, @samp{red},
26041 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26044 @item set style filename foreground @var{color}
26045 Set the foreground to @var{color}. Valid colors are @samp{none}
26046 (meaning the terminal's default color), @samp{black}, @samp{red},
26047 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26050 @item set style filename intensity @var{value}
26051 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26052 (the default), @samp{bold}, and @samp{dim}.
26055 The @code{show style} command and its subcommands are styling
26056 a style name in their output using its own style.
26057 So, use @command{show style} to see the complete list of styles,
26058 their characteristics and the visual aspect of each style.
26060 The style-able objects are:
26063 Control the styling of file names. By default, this style's
26064 foreground color is green.
26067 Control the styling of function names. These are managed with the
26068 @code{set style function} family of commands. By default, this
26069 style's foreground color is yellow.
26072 Control the styling of variable names. These are managed with the
26073 @code{set style variable} family of commands. By default, this style's
26074 foreground color is cyan.
26077 Control the styling of addresses. These are managed with the
26078 @code{set style address} family of commands. By default, this style's
26079 foreground color is blue.
26082 Control the styling of @value{GDBN}'s version number text. By
26083 default, this style's foreground color is magenta and it has bold
26084 intensity. The version number is displayed in two places, the output
26085 of @command{show version}, and when @value{GDBN} starts up.
26087 In order to control how @value{GDBN} styles the version number at
26088 startup, add the @code{set style version} family of commands to the
26089 early initialization command file (@pxref{Initialization
26093 Control the styling of titles. These are managed with the
26094 @code{set style title} family of commands. By default, this style's
26095 intensity is bold. Commands are using the title style to improve
26096 the readability of large output. For example, the commands
26097 @command{apropos} and @command{help} are using the title style
26098 for the command names.
26101 Control the styling of highlightings. These are managed with the
26102 @code{set style highlight} family of commands. By default, this style's
26103 foreground color is red. Commands are using the highlight style to draw
26104 the user attention to some specific parts of their output. For example,
26105 the command @command{apropos -v REGEXP} uses the highlight style to
26106 mark the documentation parts matching @var{regexp}.
26109 Control the styling of the TUI border. Note that, unlike other
26110 styling options, only the color of the border can be controlled via
26111 @code{set style}. This was done for compatibility reasons, as TUI
26112 controls to set the border's intensity predated the addition of
26113 general styling to @value{GDBN}. @xref{TUI Configuration}.
26115 @item tui-active-border
26116 Control the styling of the active TUI border; that is, the TUI window
26117 that has the focus.
26123 @cindex number representation
26124 @cindex entering numbers
26126 You can always enter numbers in octal, decimal, or hexadecimal in
26127 @value{GDBN} by the usual conventions: octal numbers begin with
26128 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26129 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26130 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26131 10; likewise, the default display for numbers---when no particular
26132 format is specified---is base 10. You can change the default base for
26133 both input and output with the commands described below.
26136 @kindex set input-radix
26137 @item set input-radix @var{base}
26138 Set the default base for numeric input. Supported choices
26139 for @var{base} are decimal 8, 10, or 16. The base must itself be
26140 specified either unambiguously or using the current input radix; for
26144 set input-radix 012
26145 set input-radix 10.
26146 set input-radix 0xa
26150 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26151 leaves the input radix unchanged, no matter what it was, since
26152 @samp{10}, being without any leading or trailing signs of its base, is
26153 interpreted in the current radix. Thus, if the current radix is 16,
26154 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26157 @kindex set output-radix
26158 @item set output-radix @var{base}
26159 Set the default base for numeric display. Supported choices
26160 for @var{base} are decimal 8, 10, or 16. The base must itself be
26161 specified either unambiguously or using the current input radix.
26163 @kindex show input-radix
26164 @item show input-radix
26165 Display the current default base for numeric input.
26167 @kindex show output-radix
26168 @item show output-radix
26169 Display the current default base for numeric display.
26171 @item set radix @r{[}@var{base}@r{]}
26175 These commands set and show the default base for both input and output
26176 of numbers. @code{set radix} sets the radix of input and output to
26177 the same base; without an argument, it resets the radix back to its
26178 default value of 10.
26183 @section Configuring the Current ABI
26185 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26186 application automatically. However, sometimes you need to override its
26187 conclusions. Use these commands to manage @value{GDBN}'s view of the
26193 @cindex Newlib OS ABI and its influence on the longjmp handling
26195 One @value{GDBN} configuration can debug binaries for multiple operating
26196 system targets, either via remote debugging or native emulation.
26197 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26198 but you can override its conclusion using the @code{set osabi} command.
26199 One example where this is useful is in debugging of binaries which use
26200 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26201 not have the same identifying marks that the standard C library for your
26204 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26205 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26206 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26207 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26211 Show the OS ABI currently in use.
26214 With no argument, show the list of registered available OS ABI's.
26216 @item set osabi @var{abi}
26217 Set the current OS ABI to @var{abi}.
26220 @cindex float promotion
26222 Generally, the way that an argument of type @code{float} is passed to a
26223 function depends on whether the function is prototyped. For a prototyped
26224 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26225 according to the architecture's convention for @code{float}. For unprototyped
26226 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26227 @code{double} and then passed.
26229 Unfortunately, some forms of debug information do not reliably indicate whether
26230 a function is prototyped. If @value{GDBN} calls a function that is not marked
26231 as prototyped, it consults @kbd{set coerce-float-to-double}.
26234 @kindex set coerce-float-to-double
26235 @item set coerce-float-to-double
26236 @itemx set coerce-float-to-double on
26237 Arguments of type @code{float} will be promoted to @code{double} when passed
26238 to an unprototyped function. This is the default setting.
26240 @item set coerce-float-to-double off
26241 Arguments of type @code{float} will be passed directly to unprototyped
26244 @kindex show coerce-float-to-double
26245 @item show coerce-float-to-double
26246 Show the current setting of promoting @code{float} to @code{double}.
26250 @kindex show cp-abi
26251 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26252 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26253 used to build your application. @value{GDBN} only fully supports
26254 programs with a single C@t{++} ABI; if your program contains code using
26255 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26256 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26257 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26258 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26259 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26260 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26265 Show the C@t{++} ABI currently in use.
26268 With no argument, show the list of supported C@t{++} ABI's.
26270 @item set cp-abi @var{abi}
26271 @itemx set cp-abi auto
26272 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26276 @section Automatically loading associated files
26277 @cindex auto-loading
26279 @value{GDBN} sometimes reads files with commands and settings automatically,
26280 without being explicitly told so by the user. We call this feature
26281 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26282 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26283 results or introduce security risks (e.g., if the file comes from untrusted
26286 There are various kinds of files @value{GDBN} can automatically load.
26287 In addition to these files, @value{GDBN} supports auto-loading code written
26288 in various extension languages. @xref{Auto-loading extensions}.
26290 Note that loading of these associated files (including the local @file{.gdbinit}
26291 file) requires accordingly configured @code{auto-load safe-path}
26292 (@pxref{Auto-loading safe path}).
26294 For these reasons, @value{GDBN} includes commands and options to let you
26295 control when to auto-load files and which files should be auto-loaded.
26298 @anchor{set auto-load off}
26299 @kindex set auto-load off
26300 @item set auto-load off
26301 Globally disable loading of all auto-loaded files.
26302 You may want to use this command with the @samp{-iex} option
26303 (@pxref{Option -init-eval-command}) such as:
26305 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26308 Be aware that system init file (@pxref{System-wide configuration})
26309 and init files from your home directory (@pxref{Home Directory Init File})
26310 still get read (as they come from generally trusted directories).
26311 To prevent @value{GDBN} from auto-loading even those init files, use the
26312 @option{-nx} option (@pxref{Mode Options}), in addition to
26313 @code{set auto-load no}.
26315 @anchor{show auto-load}
26316 @kindex show auto-load
26317 @item show auto-load
26318 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26322 (gdb) show auto-load
26323 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26324 libthread-db: Auto-loading of inferior specific libthread_db is on.
26325 local-gdbinit: Auto-loading of .gdbinit script from current directory
26327 python-scripts: Auto-loading of Python scripts is on.
26328 safe-path: List of directories from which it is safe to auto-load files
26329 is $debugdir:$datadir/auto-load.
26330 scripts-directory: List of directories from which to load auto-loaded scripts
26331 is $debugdir:$datadir/auto-load.
26334 @anchor{info auto-load}
26335 @kindex info auto-load
26336 @item info auto-load
26337 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26341 (gdb) info auto-load
26344 Yes /home/user/gdb/gdb-gdb.gdb
26345 libthread-db: No auto-loaded libthread-db.
26346 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26350 Yes /home/user/gdb/gdb-gdb.py
26354 These are @value{GDBN} control commands for the auto-loading:
26356 @multitable @columnfractions .5 .5
26357 @item @xref{set auto-load off}.
26358 @tab Disable auto-loading globally.
26359 @item @xref{show auto-load}.
26360 @tab Show setting of all kinds of files.
26361 @item @xref{info auto-load}.
26362 @tab Show state of all kinds of files.
26363 @item @xref{set auto-load gdb-scripts}.
26364 @tab Control for @value{GDBN} command scripts.
26365 @item @xref{show auto-load gdb-scripts}.
26366 @tab Show setting of @value{GDBN} command scripts.
26367 @item @xref{info auto-load gdb-scripts}.
26368 @tab Show state of @value{GDBN} command scripts.
26369 @item @xref{set auto-load python-scripts}.
26370 @tab Control for @value{GDBN} Python scripts.
26371 @item @xref{show auto-load python-scripts}.
26372 @tab Show setting of @value{GDBN} Python scripts.
26373 @item @xref{info auto-load python-scripts}.
26374 @tab Show state of @value{GDBN} Python scripts.
26375 @item @xref{set auto-load guile-scripts}.
26376 @tab Control for @value{GDBN} Guile scripts.
26377 @item @xref{show auto-load guile-scripts}.
26378 @tab Show setting of @value{GDBN} Guile scripts.
26379 @item @xref{info auto-load guile-scripts}.
26380 @tab Show state of @value{GDBN} Guile scripts.
26381 @item @xref{set auto-load scripts-directory}.
26382 @tab Control for @value{GDBN} auto-loaded scripts location.
26383 @item @xref{show auto-load scripts-directory}.
26384 @tab Show @value{GDBN} auto-loaded scripts location.
26385 @item @xref{add-auto-load-scripts-directory}.
26386 @tab Add directory for auto-loaded scripts location list.
26387 @item @xref{set auto-load local-gdbinit}.
26388 @tab Control for init file in the current directory.
26389 @item @xref{show auto-load local-gdbinit}.
26390 @tab Show setting of init file in the current directory.
26391 @item @xref{info auto-load local-gdbinit}.
26392 @tab Show state of init file in the current directory.
26393 @item @xref{set auto-load libthread-db}.
26394 @tab Control for thread debugging library.
26395 @item @xref{show auto-load libthread-db}.
26396 @tab Show setting of thread debugging library.
26397 @item @xref{info auto-load libthread-db}.
26398 @tab Show state of thread debugging library.
26399 @item @xref{set auto-load safe-path}.
26400 @tab Control directories trusted for automatic loading.
26401 @item @xref{show auto-load safe-path}.
26402 @tab Show directories trusted for automatic loading.
26403 @item @xref{add-auto-load-safe-path}.
26404 @tab Add directory trusted for automatic loading.
26408 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26409 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26411 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26412 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26415 @node Init File in the Current Directory
26416 @subsection Automatically loading init file in the current directory
26417 @cindex auto-loading init file in the current directory
26419 By default, @value{GDBN} reads and executes the canned sequences of commands
26420 from init file (if any) in the current working directory,
26421 see @ref{Init File in the Current Directory during Startup}.
26423 Note that loading of this local @file{.gdbinit} file also requires accordingly
26424 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26427 @anchor{set auto-load local-gdbinit}
26428 @kindex set auto-load local-gdbinit
26429 @item set auto-load local-gdbinit [on|off]
26430 Enable or disable the auto-loading of canned sequences of commands
26431 (@pxref{Sequences}) found in init file in the current directory.
26433 @anchor{show auto-load local-gdbinit}
26434 @kindex show auto-load local-gdbinit
26435 @item show auto-load local-gdbinit
26436 Show whether auto-loading of canned sequences of commands from init file in the
26437 current directory is enabled or disabled.
26439 @anchor{info auto-load local-gdbinit}
26440 @kindex info auto-load local-gdbinit
26441 @item info auto-load local-gdbinit
26442 Print whether canned sequences of commands from init file in the
26443 current directory have been auto-loaded.
26446 @node libthread_db.so.1 file
26447 @subsection Automatically loading thread debugging library
26448 @cindex auto-loading libthread_db.so.1
26450 This feature is currently present only on @sc{gnu}/Linux native hosts.
26452 @value{GDBN} reads in some cases thread debugging library from places specific
26453 to the inferior (@pxref{set libthread-db-search-path}).
26455 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26456 without checking this @samp{set auto-load libthread-db} switch as system
26457 libraries have to be trusted in general. In all other cases of
26458 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26459 auto-load libthread-db} is enabled before trying to open such thread debugging
26462 Note that loading of this debugging library also requires accordingly configured
26463 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26466 @anchor{set auto-load libthread-db}
26467 @kindex set auto-load libthread-db
26468 @item set auto-load libthread-db [on|off]
26469 Enable or disable the auto-loading of inferior specific thread debugging library.
26471 @anchor{show auto-load libthread-db}
26472 @kindex show auto-load libthread-db
26473 @item show auto-load libthread-db
26474 Show whether auto-loading of inferior specific thread debugging library is
26475 enabled or disabled.
26477 @anchor{info auto-load libthread-db}
26478 @kindex info auto-load libthread-db
26479 @item info auto-load libthread-db
26480 Print the list of all loaded inferior specific thread debugging libraries and
26481 for each such library print list of inferior @var{pid}s using it.
26484 @node Auto-loading safe path
26485 @subsection Security restriction for auto-loading
26486 @cindex auto-loading safe-path
26488 As the files of inferior can come from untrusted source (such as submitted by
26489 an application user) @value{GDBN} does not always load any files automatically.
26490 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26491 directories trusted for loading files not explicitly requested by user.
26492 Each directory can also be a shell wildcard pattern.
26494 If the path is not set properly you will see a warning and the file will not
26499 Reading symbols from /home/user/gdb/gdb...
26500 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26501 declined by your `auto-load safe-path' set
26502 to "$debugdir:$datadir/auto-load".
26503 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26504 declined by your `auto-load safe-path' set
26505 to "$debugdir:$datadir/auto-load".
26509 To instruct @value{GDBN} to go ahead and use the init files anyway,
26510 invoke @value{GDBN} like this:
26513 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26516 The list of trusted directories is controlled by the following commands:
26519 @anchor{set auto-load safe-path}
26520 @kindex set auto-load safe-path
26521 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26522 Set the list of directories (and their subdirectories) trusted for automatic
26523 loading and execution of scripts. You can also enter a specific trusted file.
26524 Each directory can also be a shell wildcard pattern; wildcards do not match
26525 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26526 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26527 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26528 its default value as specified during @value{GDBN} compilation.
26530 The list of directories uses path separator (@samp{:} on GNU and Unix
26531 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26532 to the @env{PATH} environment variable.
26534 @anchor{show auto-load safe-path}
26535 @kindex show auto-load safe-path
26536 @item show auto-load safe-path
26537 Show the list of directories trusted for automatic loading and execution of
26540 @anchor{add-auto-load-safe-path}
26541 @kindex add-auto-load-safe-path
26542 @item add-auto-load-safe-path
26543 Add an entry (or list of entries) to the list of directories trusted for
26544 automatic loading and execution of scripts. Multiple entries may be delimited
26545 by the host platform path separator in use.
26548 This variable defaults to what @code{--with-auto-load-dir} has been configured
26549 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26550 substitution applies the same as for @ref{set auto-load scripts-directory}.
26551 The default @code{set auto-load safe-path} value can be also overriden by
26552 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26554 Setting this variable to @file{/} disables this security protection,
26555 corresponding @value{GDBN} configuration option is
26556 @option{--without-auto-load-safe-path}.
26557 This variable is supposed to be set to the system directories writable by the
26558 system superuser only. Users can add their source directories in init files in
26559 their home directories (@pxref{Home Directory Init File}). See also deprecated
26560 init file in the current directory
26561 (@pxref{Init File in the Current Directory during Startup}).
26563 To force @value{GDBN} to load the files it declined to load in the previous
26564 example, you could use one of the following ways:
26567 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26568 Specify this trusted directory (or a file) as additional component of the list.
26569 You have to specify also any existing directories displayed by
26570 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26572 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26573 Specify this directory as in the previous case but just for a single
26574 @value{GDBN} session.
26576 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26577 Disable auto-loading safety for a single @value{GDBN} session.
26578 This assumes all the files you debug during this @value{GDBN} session will come
26579 from trusted sources.
26581 @item @kbd{./configure --without-auto-load-safe-path}
26582 During compilation of @value{GDBN} you may disable any auto-loading safety.
26583 This assumes all the files you will ever debug with this @value{GDBN} come from
26587 On the other hand you can also explicitly forbid automatic files loading which
26588 also suppresses any such warning messages:
26591 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26592 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26594 @item @file{~/.gdbinit}: @samp{set auto-load no}
26595 Disable auto-loading globally for the user
26596 (@pxref{Home Directory Init File}). While it is improbable, you could also
26597 use system init file instead (@pxref{System-wide configuration}).
26600 This setting applies to the file names as entered by user. If no entry matches
26601 @value{GDBN} tries as a last resort to also resolve all the file names into
26602 their canonical form (typically resolving symbolic links) and compare the
26603 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26604 own before starting the comparison so a canonical form of directories is
26605 recommended to be entered.
26607 @node Auto-loading verbose mode
26608 @subsection Displaying files tried for auto-load
26609 @cindex auto-loading verbose mode
26611 For better visibility of all the file locations where you can place scripts to
26612 be auto-loaded with inferior --- or to protect yourself against accidental
26613 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26614 all the files attempted to be loaded. Both existing and non-existing files may
26617 For example the list of directories from which it is safe to auto-load files
26618 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26619 may not be too obvious while setting it up.
26622 (gdb) set debug auto-load on
26623 (gdb) file ~/src/t/true
26624 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26625 for objfile "/tmp/true".
26626 auto-load: Updating directories of "/usr:/opt".
26627 auto-load: Using directory "/usr".
26628 auto-load: Using directory "/opt".
26629 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26630 by your `auto-load safe-path' set to "/usr:/opt".
26634 @anchor{set debug auto-load}
26635 @kindex set debug auto-load
26636 @item set debug auto-load [on|off]
26637 Set whether to print the filenames attempted to be auto-loaded.
26639 @anchor{show debug auto-load}
26640 @kindex show debug auto-load
26641 @item show debug auto-load
26642 Show whether printing of the filenames attempted to be auto-loaded is turned
26646 @node Messages/Warnings
26647 @section Optional Warnings and Messages
26649 @cindex verbose operation
26650 @cindex optional warnings
26651 By default, @value{GDBN} is silent about its inner workings. If you are
26652 running on a slow machine, you may want to use the @code{set verbose}
26653 command. This makes @value{GDBN} tell you when it does a lengthy
26654 internal operation, so you will not think it has crashed.
26656 Currently, the messages controlled by @code{set verbose} are those
26657 which announce that the symbol table for a source file is being read;
26658 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26661 @kindex set verbose
26662 @item set verbose on
26663 Enables @value{GDBN} output of certain informational messages.
26665 @item set verbose off
26666 Disables @value{GDBN} output of certain informational messages.
26668 @kindex show verbose
26670 Displays whether @code{set verbose} is on or off.
26673 By default, if @value{GDBN} encounters bugs in the symbol table of an
26674 object file, it is silent; but if you are debugging a compiler, you may
26675 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26680 @kindex set complaints
26681 @item set complaints @var{limit}
26682 Permits @value{GDBN} to output @var{limit} complaints about each type of
26683 unusual symbols before becoming silent about the problem. Set
26684 @var{limit} to zero to suppress all complaints; set it to a large number
26685 to prevent complaints from being suppressed.
26687 @kindex show complaints
26688 @item show complaints
26689 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26693 @anchor{confirmation requests}
26694 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26695 lot of stupid questions to confirm certain commands. For example, if
26696 you try to run a program which is already running:
26700 The program being debugged has been started already.
26701 Start it from the beginning? (y or n)
26704 If you are willing to unflinchingly face the consequences of your own
26705 commands, you can disable this ``feature'':
26709 @kindex set confirm
26711 @cindex confirmation
26712 @cindex stupid questions
26713 @item set confirm off
26714 Disables confirmation requests. Note that running @value{GDBN} with
26715 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26716 automatically disables confirmation requests.
26718 @item set confirm on
26719 Enables confirmation requests (the default).
26721 @kindex show confirm
26723 Displays state of confirmation requests.
26727 @cindex command tracing
26728 If you need to debug user-defined commands or sourced files you may find it
26729 useful to enable @dfn{command tracing}. In this mode each command will be
26730 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26731 quantity denoting the call depth of each command.
26734 @kindex set trace-commands
26735 @cindex command scripts, debugging
26736 @item set trace-commands on
26737 Enable command tracing.
26738 @item set trace-commands off
26739 Disable command tracing.
26740 @item show trace-commands
26741 Display the current state of command tracing.
26744 @node Debugging Output
26745 @section Optional Messages about Internal Happenings
26746 @cindex optional debugging messages
26748 @value{GDBN} has commands that enable optional debugging messages from
26749 various @value{GDBN} subsystems; normally these commands are of
26750 interest to @value{GDBN} maintainers, or when reporting a bug. This
26751 section documents those commands.
26754 @kindex set exec-done-display
26755 @item set exec-done-display
26756 Turns on or off the notification of asynchronous commands'
26757 completion. When on, @value{GDBN} will print a message when an
26758 asynchronous command finishes its execution. The default is off.
26759 @kindex show exec-done-display
26760 @item show exec-done-display
26761 Displays the current setting of asynchronous command completion
26765 @cindex ARM AArch64
26766 @item set debug aarch64
26767 Turns on or off display of debugging messages related to ARM AArch64.
26768 The default is off.
26770 @item show debug aarch64
26771 Displays the current state of displaying debugging messages related to
26774 @cindex gdbarch debugging info
26775 @cindex architecture debugging info
26776 @item set debug arch
26777 Turns on or off display of gdbarch debugging info. The default is off
26778 @item show debug arch
26779 Displays the current state of displaying gdbarch debugging info.
26781 @item set debug aix-solib
26782 @cindex AIX shared library debugging
26783 Control display of debugging messages from the AIX shared library
26784 support module. The default is off.
26785 @item show debug aix-solib
26786 Show the current state of displaying AIX shared library debugging messages.
26788 @item set debug aix-thread
26789 @cindex AIX threads
26790 Display debugging messages about inner workings of the AIX thread
26792 @item show debug aix-thread
26793 Show the current state of AIX thread debugging info display.
26795 @item set debug check-physname
26797 Check the results of the ``physname'' computation. When reading DWARF
26798 debugging information for C@t{++}, @value{GDBN} attempts to compute
26799 each entity's name. @value{GDBN} can do this computation in two
26800 different ways, depending on exactly what information is present.
26801 When enabled, this setting causes @value{GDBN} to compute the names
26802 both ways and display any discrepancies.
26803 @item show debug check-physname
26804 Show the current state of ``physname'' checking.
26806 @item set debug coff-pe-read
26807 @cindex COFF/PE exported symbols
26808 Control display of debugging messages related to reading of COFF/PE
26809 exported symbols. The default is off.
26810 @item show debug coff-pe-read
26811 Displays the current state of displaying debugging messages related to
26812 reading of COFF/PE exported symbols.
26814 @item set debug dwarf-die
26816 Dump DWARF DIEs after they are read in.
26817 The value is the number of nesting levels to print.
26818 A value of zero turns off the display.
26819 @item show debug dwarf-die
26820 Show the current state of DWARF DIE debugging.
26822 @item set debug dwarf-line
26823 @cindex DWARF Line Tables
26824 Turns on or off display of debugging messages related to reading
26825 DWARF line tables. The default is 0 (off).
26826 A value of 1 provides basic information.
26827 A value greater than 1 provides more verbose information.
26828 @item show debug dwarf-line
26829 Show the current state of DWARF line table debugging.
26831 @item set debug dwarf-read
26832 @cindex DWARF Reading
26833 Turns on or off display of debugging messages related to reading
26834 DWARF debug info. The default is 0 (off).
26835 A value of 1 provides basic information.
26836 A value greater than 1 provides more verbose information.
26837 @item show debug dwarf-read
26838 Show the current state of DWARF reader debugging.
26840 @item set debug displaced
26841 @cindex displaced stepping debugging info
26842 Turns on or off display of @value{GDBN} debugging info for the
26843 displaced stepping support. The default is off.
26844 @item show debug displaced
26845 Displays the current state of displaying @value{GDBN} debugging info
26846 related to displaced stepping.
26848 @item set debug event
26849 @cindex event debugging info
26850 Turns on or off display of @value{GDBN} event debugging info. The
26852 @item show debug event
26853 Displays the current state of displaying @value{GDBN} event debugging
26856 @item set debug event-loop
26857 @cindex event-loop debugging
26858 Controls output of debugging info about the event loop. The possible
26859 values are @samp{off}, @samp{all} (shows all debugging info) and
26860 @samp{all-except-ui} (shows all debugging info except those about
26861 UI-related events).
26862 @item show debug event-loop
26863 Shows the current state of displaying debugging info about the event
26866 @item set debug expression
26867 @cindex expression debugging info
26868 Turns on or off display of debugging info about @value{GDBN}
26869 expression parsing. The default is off.
26870 @item show debug expression
26871 Displays the current state of displaying debugging info about
26872 @value{GDBN} expression parsing.
26874 @item set debug fbsd-lwp
26875 @cindex FreeBSD LWP debug messages
26876 Turns on or off debugging messages from the FreeBSD LWP debug support.
26877 @item show debug fbsd-lwp
26878 Show the current state of FreeBSD LWP debugging messages.
26880 @item set debug fbsd-nat
26881 @cindex FreeBSD native target debug messages
26882 Turns on or off debugging messages from the FreeBSD native target.
26883 @item show debug fbsd-nat
26884 Show the current state of FreeBSD native target debugging messages.
26886 @item set debug fortran-array-slicing
26887 @cindex fortran array slicing debugging info
26888 Turns on or off display of @value{GDBN} Fortran array slicing
26889 debugging info. The default is off.
26891 @item show debug fortran-array-slicing
26892 Displays the current state of displaying @value{GDBN} Fortran array
26893 slicing debugging info.
26895 @item set debug frame
26896 @cindex frame debugging info
26897 Turns on or off display of @value{GDBN} frame debugging info. The
26899 @item show debug frame
26900 Displays the current state of displaying @value{GDBN} frame debugging
26903 @item set debug gnu-nat
26904 @cindex @sc{gnu}/Hurd debug messages
26905 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26906 @item show debug gnu-nat
26907 Show the current state of @sc{gnu}/Hurd debugging messages.
26909 @item set debug infrun
26910 @cindex inferior debugging info
26911 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26912 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26913 for implementing operations such as single-stepping the inferior.
26914 @item show debug infrun
26915 Displays the current state of @value{GDBN} inferior debugging.
26917 @item set debug jit
26918 @cindex just-in-time compilation, debugging messages
26919 Turn on or off debugging messages from JIT debug support.
26920 @item show debug jit
26921 Displays the current state of @value{GDBN} JIT debugging.
26923 @item set debug lin-lwp
26924 @cindex @sc{gnu}/Linux LWP debug messages
26925 @cindex Linux lightweight processes
26926 Turn on or off debugging messages from the Linux LWP debug support.
26927 @item show debug lin-lwp
26928 Show the current state of Linux LWP debugging messages.
26930 @item set debug linux-namespaces
26931 @cindex @sc{gnu}/Linux namespaces debug messages
26932 Turn on or off debugging messages from the Linux namespaces debug support.
26933 @item show debug linux-namespaces
26934 Show the current state of Linux namespaces debugging messages.
26936 @item set debug mach-o
26937 @cindex Mach-O symbols processing
26938 Control display of debugging messages related to Mach-O symbols
26939 processing. The default is off.
26940 @item show debug mach-o
26941 Displays the current state of displaying debugging messages related to
26942 reading of COFF/PE exported symbols.
26944 @item set debug notification
26945 @cindex remote async notification debugging info
26946 Turn on or off debugging messages about remote async notification.
26947 The default is off.
26948 @item show debug notification
26949 Displays the current state of remote async notification debugging messages.
26951 @item set debug observer
26952 @cindex observer debugging info
26953 Turns on or off display of @value{GDBN} observer debugging. This
26954 includes info such as the notification of observable events.
26955 @item show debug observer
26956 Displays the current state of observer debugging.
26958 @item set debug overload
26959 @cindex C@t{++} overload debugging info
26960 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26961 info. This includes info such as ranking of functions, etc. The default
26963 @item show debug overload
26964 Displays the current state of displaying @value{GDBN} C@t{++} overload
26967 @cindex expression parser, debugging info
26968 @cindex debug expression parser
26969 @item set debug parser
26970 Turns on or off the display of expression parser debugging output.
26971 Internally, this sets the @code{yydebug} variable in the expression
26972 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26973 details. The default is off.
26974 @item show debug parser
26975 Show the current state of expression parser debugging.
26977 @cindex packets, reporting on stdout
26978 @cindex serial connections, debugging
26979 @cindex debug remote protocol
26980 @cindex remote protocol debugging
26981 @cindex display remote packets
26982 @item set debug remote
26983 Turns on or off display of reports on all packets sent back and forth across
26984 the serial line to the remote machine. The info is printed on the
26985 @value{GDBN} standard output stream. The default is off.
26986 @item show debug remote
26987 Displays the state of display of remote packets.
26989 @item set debug remote-packet-max-chars
26990 Sets the maximum number of characters to display for each remote packet when
26991 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
26992 displaying lengthy remote packets and polluting the console.
26994 The default value is @code{512}, which means @value{GDBN} will truncate each
26995 remote packet after 512 bytes.
26997 Setting this option to @code{unlimited} will disable truncation and will output
26998 the full length of the remote packets.
26999 @item show debug remote-packet-max-chars
27000 Displays the number of bytes to output for remote packet debugging.
27002 @item set debug separate-debug-file
27003 Turns on or off display of debug output about separate debug file search.
27004 @item show debug separate-debug-file
27005 Displays the state of separate debug file search debug output.
27007 @item set debug serial
27008 Turns on or off display of @value{GDBN} serial debugging info. The
27010 @item show debug serial
27011 Displays the current state of displaying @value{GDBN} serial debugging
27014 @item set debug solib-frv
27015 @cindex FR-V shared-library debugging
27016 Turn on or off debugging messages for FR-V shared-library code.
27017 @item show debug solib-frv
27018 Display the current state of FR-V shared-library code debugging
27021 @item set debug symbol-lookup
27022 @cindex symbol lookup
27023 Turns on or off display of debugging messages related to symbol lookup.
27024 The default is 0 (off).
27025 A value of 1 provides basic information.
27026 A value greater than 1 provides more verbose information.
27027 @item show debug symbol-lookup
27028 Show the current state of symbol lookup debugging messages.
27030 @item set debug symfile
27031 @cindex symbol file functions
27032 Turns on or off display of debugging messages related to symbol file functions.
27033 The default is off. @xref{Files}.
27034 @item show debug symfile
27035 Show the current state of symbol file debugging messages.
27037 @item set debug symtab-create
27038 @cindex symbol table creation
27039 Turns on or off display of debugging messages related to symbol table creation.
27040 The default is 0 (off).
27041 A value of 1 provides basic information.
27042 A value greater than 1 provides more verbose information.
27043 @item show debug symtab-create
27044 Show the current state of symbol table creation debugging.
27046 @item set debug target
27047 @cindex target debugging info
27048 Turns on or off display of @value{GDBN} target debugging info. This info
27049 includes what is going on at the target level of GDB, as it happens. The
27050 default is 0. Set it to 1 to track events, and to 2 to also track the
27051 value of large memory transfers.
27052 @item show debug target
27053 Displays the current state of displaying @value{GDBN} target debugging
27056 @item set debug timestamp
27057 @cindex timestamping debugging info
27058 Turns on or off display of timestamps with @value{GDBN} debugging info.
27059 When enabled, seconds and microseconds are displayed before each debugging
27061 @item show debug timestamp
27062 Displays the current state of displaying timestamps with @value{GDBN}
27065 @item set debug varobj
27066 @cindex variable object debugging info
27067 Turns on or off display of @value{GDBN} variable object debugging
27068 info. The default is off.
27069 @item show debug varobj
27070 Displays the current state of displaying @value{GDBN} variable object
27073 @item set debug xml
27074 @cindex XML parser debugging
27075 Turn on or off debugging messages for built-in XML parsers.
27076 @item show debug xml
27077 Displays the current state of XML debugging messages.
27080 @node Other Misc Settings
27081 @section Other Miscellaneous Settings
27082 @cindex miscellaneous settings
27085 @kindex set interactive-mode
27086 @item set interactive-mode
27087 If @code{on}, forces @value{GDBN} to assume that GDB was started
27088 in a terminal. In practice, this means that @value{GDBN} should wait
27089 for the user to answer queries generated by commands entered at
27090 the command prompt. If @code{off}, forces @value{GDBN} to operate
27091 in the opposite mode, and it uses the default answers to all queries.
27092 If @code{auto} (the default), @value{GDBN} tries to determine whether
27093 its standard input is a terminal, and works in interactive-mode if it
27094 is, non-interactively otherwise.
27096 In the vast majority of cases, the debugger should be able to guess
27097 correctly which mode should be used. But this setting can be useful
27098 in certain specific cases, such as running a MinGW @value{GDBN}
27099 inside a cygwin window.
27101 @kindex show interactive-mode
27102 @item show interactive-mode
27103 Displays whether the debugger is operating in interactive mode or not.
27106 @node Extending GDB
27107 @chapter Extending @value{GDBN}
27108 @cindex extending GDB
27110 @value{GDBN} provides several mechanisms for extension.
27111 @value{GDBN} also provides the ability to automatically load
27112 extensions when it reads a file for debugging. This allows the
27113 user to automatically customize @value{GDBN} for the program
27116 To facilitate the use of extension languages, @value{GDBN} is capable
27117 of evaluating the contents of a file. When doing so, @value{GDBN}
27118 can recognize which extension language is being used by looking at
27119 the filename extension. Files with an unrecognized filename extension
27120 are always treated as a @value{GDBN} Command Files.
27121 @xref{Command Files,, Command files}.
27123 You can control how @value{GDBN} evaluates these files with the following
27127 @kindex set script-extension
27128 @kindex show script-extension
27129 @item set script-extension off
27130 All scripts are always evaluated as @value{GDBN} Command Files.
27132 @item set script-extension soft
27133 The debugger determines the scripting language based on filename
27134 extension. If this scripting language is supported, @value{GDBN}
27135 evaluates the script using that language. Otherwise, it evaluates
27136 the file as a @value{GDBN} Command File.
27138 @item set script-extension strict
27139 The debugger determines the scripting language based on filename
27140 extension, and evaluates the script using that language. If the
27141 language is not supported, then the evaluation fails.
27143 @item show script-extension
27144 Display the current value of the @code{script-extension} option.
27148 @ifset SYSTEM_GDBINIT_DIR
27149 This setting is not used for files in the system-wide gdbinit directory.
27150 Files in that directory must have an extension matching their language,
27151 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27152 commands. @xref{Startup}.
27156 * Sequences:: Canned Sequences of @value{GDBN} Commands
27157 * Aliases:: Command Aliases
27158 * Python:: Extending @value{GDBN} using Python
27159 * Guile:: Extending @value{GDBN} using Guile
27160 * Auto-loading extensions:: Automatically loading extensions
27161 * Multiple Extension Languages:: Working with multiple extension languages
27165 @section Canned Sequences of Commands
27167 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27168 Command Lists}), @value{GDBN} provides two ways to store sequences of
27169 commands for execution as a unit: user-defined commands and command
27173 * Define:: How to define your own commands
27174 * Hooks:: Hooks for user-defined commands
27175 * Command Files:: How to write scripts of commands to be stored in a file
27176 * Output:: Commands for controlled output
27177 * Auto-loading sequences:: Controlling auto-loaded command files
27181 @subsection User-defined Commands
27183 @cindex user-defined command
27184 @cindex arguments, to user-defined commands
27185 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27186 which you assign a new name as a command. This is done with the
27187 @code{define} command. User commands may accept an unlimited number of arguments
27188 separated by whitespace. Arguments are accessed within the user command
27189 via @code{$arg0@dots{}$argN}. A trivial example:
27193 print $arg0 + $arg1 + $arg2
27198 To execute the command use:
27205 This defines the command @code{adder}, which prints the sum of
27206 its three arguments. Note the arguments are text substitutions, so they may
27207 reference variables, use complex expressions, or even perform inferior
27210 @cindex argument count in user-defined commands
27211 @cindex how many arguments (user-defined commands)
27212 In addition, @code{$argc} may be used to find out how many arguments have
27218 print $arg0 + $arg1
27221 print $arg0 + $arg1 + $arg2
27226 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27227 to process a variable number of arguments:
27234 eval "set $sum = $sum + $arg%d", $i
27244 @item define @var{commandname}
27245 Define a command named @var{commandname}. If there is already a command
27246 by that name, you are asked to confirm that you want to redefine it.
27247 The argument @var{commandname} may be a bare command name consisting of letters,
27248 numbers, dashes, dots, and underscores. It may also start with any
27249 predefined or user-defined prefix command.
27250 For example, @samp{define target my-target} creates
27251 a user-defined @samp{target my-target} command.
27253 The definition of the command is made up of other @value{GDBN} command lines,
27254 which are given following the @code{define} command. The end of these
27255 commands is marked by a line containing @code{end}.
27258 @kindex end@r{ (user-defined commands)}
27259 @item document @var{commandname}
27260 Document the user-defined command @var{commandname}, so that it can be
27261 accessed by @code{help}. The command @var{commandname} must already be
27262 defined. This command reads lines of documentation just as @code{define}
27263 reads the lines of the command definition, ending with @code{end}.
27264 After the @code{document} command is finished, @code{help} on command
27265 @var{commandname} displays the documentation you have written.
27267 You may use the @code{document} command again to change the
27268 documentation of a command. Redefining the command with @code{define}
27269 does not change the documentation.
27271 @kindex define-prefix
27272 @item define-prefix @var{commandname}
27273 Define or mark the command @var{commandname} as a user-defined prefix
27274 command. Once marked, @var{commandname} can be used as prefix command
27275 by the @code{define} command.
27276 Note that @code{define-prefix} can be used with a not yet defined
27277 @var{commandname}. In such a case, @var{commandname} is defined as
27278 an empty user-defined command.
27279 In case you redefine a command that was marked as a user-defined
27280 prefix command, the subcommands of the redefined command are kept
27281 (and @value{GDBN} indicates so to the user).
27285 (gdb) define-prefix abc
27286 (gdb) define-prefix abc def
27287 (gdb) define abc def
27288 Type commands for definition of "abc def".
27289 End with a line saying just "end".
27290 >echo command initial def\n
27292 (gdb) define abc def ghi
27293 Type commands for definition of "abc def ghi".
27294 End with a line saying just "end".
27295 >echo command ghi\n
27297 (gdb) define abc def
27298 Keeping subcommands of prefix command "def".
27299 Redefine command "def"? (y or n) y
27300 Type commands for definition of "abc def".
27301 End with a line saying just "end".
27302 >echo command def\n
27311 @kindex dont-repeat
27312 @cindex don't repeat command
27314 Used inside a user-defined command, this tells @value{GDBN} that this
27315 command should not be repeated when the user hits @key{RET}
27316 (@pxref{Command Syntax, repeat last command}).
27318 @kindex help user-defined
27319 @item help user-defined
27320 List all user-defined commands and all python commands defined in class
27321 COMMAND_USER. The first line of the documentation or docstring is
27326 @itemx show user @var{commandname}
27327 Display the @value{GDBN} commands used to define @var{commandname} (but
27328 not its documentation). If no @var{commandname} is given, display the
27329 definitions for all user-defined commands.
27330 This does not work for user-defined python commands.
27332 @cindex infinite recursion in user-defined commands
27333 @kindex show max-user-call-depth
27334 @kindex set max-user-call-depth
27335 @item show max-user-call-depth
27336 @itemx set max-user-call-depth
27337 The value of @code{max-user-call-depth} controls how many recursion
27338 levels are allowed in user-defined commands before @value{GDBN} suspects an
27339 infinite recursion and aborts the command.
27340 This does not apply to user-defined python commands.
27343 In addition to the above commands, user-defined commands frequently
27344 use control flow commands, described in @ref{Command Files}.
27346 When user-defined commands are executed, the
27347 commands of the definition are not printed. An error in any command
27348 stops execution of the user-defined command.
27350 If used interactively, commands that would ask for confirmation proceed
27351 without asking when used inside a user-defined command. Many @value{GDBN}
27352 commands that normally print messages to say what they are doing omit the
27353 messages when used in a user-defined command.
27356 @subsection User-defined Command Hooks
27357 @cindex command hooks
27358 @cindex hooks, for commands
27359 @cindex hooks, pre-command
27362 You may define @dfn{hooks}, which are a special kind of user-defined
27363 command. Whenever you run the command @samp{foo}, if the user-defined
27364 command @samp{hook-foo} exists, it is executed (with no arguments)
27365 before that command.
27367 @cindex hooks, post-command
27369 A hook may also be defined which is run after the command you executed.
27370 Whenever you run the command @samp{foo}, if the user-defined command
27371 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27372 that command. Post-execution hooks may exist simultaneously with
27373 pre-execution hooks, for the same command.
27375 It is valid for a hook to call the command which it hooks. If this
27376 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27378 @c It would be nice if hookpost could be passed a parameter indicating
27379 @c if the command it hooks executed properly or not. FIXME!
27381 @kindex stop@r{, a pseudo-command}
27382 In addition, a pseudo-command, @samp{stop} exists. Defining
27383 (@samp{hook-stop}) makes the associated commands execute every time
27384 execution stops in your program: before breakpoint commands are run,
27385 displays are printed, or the stack frame is printed.
27387 For example, to ignore @code{SIGALRM} signals while
27388 single-stepping, but treat them normally during normal execution,
27393 handle SIGALRM nopass
27397 handle SIGALRM pass
27400 define hook-continue
27401 handle SIGALRM pass
27405 As a further example, to hook at the beginning and end of the @code{echo}
27406 command, and to add extra text to the beginning and end of the message,
27414 define hookpost-echo
27418 (@value{GDBP}) echo Hello World
27419 <<<---Hello World--->>>
27424 You can define a hook for any single-word command in @value{GDBN}, but
27425 not for command aliases; you should define a hook for the basic command
27426 name, e.g.@: @code{backtrace} rather than @code{bt}.
27427 @c FIXME! So how does Joe User discover whether a command is an alias
27429 You can hook a multi-word command by adding @code{hook-} or
27430 @code{hookpost-} to the last word of the command, e.g.@:
27431 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27433 If an error occurs during the execution of your hook, execution of
27434 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27435 (before the command that you actually typed had a chance to run).
27437 If you try to define a hook which does not match any known command, you
27438 get a warning from the @code{define} command.
27440 @node Command Files
27441 @subsection Command Files
27443 @cindex command files
27444 @cindex scripting commands
27445 A command file for @value{GDBN} is a text file made of lines that are
27446 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27447 also be included. An empty line in a command file does nothing; it
27448 does not mean to repeat the last command, as it would from the
27451 You can request the execution of a command file with the @code{source}
27452 command. Note that the @code{source} command is also used to evaluate
27453 scripts that are not Command Files. The exact behavior can be configured
27454 using the @code{script-extension} setting.
27455 @xref{Extending GDB,, Extending GDB}.
27459 @cindex execute commands from a file
27460 @item source [-s] [-v] @var{filename}
27461 Execute the command file @var{filename}.
27464 The lines in a command file are generally executed sequentially,
27465 unless the order of execution is changed by one of the
27466 @emph{flow-control commands} described below. The commands are not
27467 printed as they are executed. An error in any command terminates
27468 execution of the command file and control is returned to the console.
27470 @value{GDBN} first searches for @var{filename} in the current directory.
27471 If the file is not found there, and @var{filename} does not specify a
27472 directory, then @value{GDBN} also looks for the file on the source search path
27473 (specified with the @samp{directory} command);
27474 except that @file{$cdir} is not searched because the compilation directory
27475 is not relevant to scripts.
27477 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27478 on the search path even if @var{filename} specifies a directory.
27479 The search is done by appending @var{filename} to each element of the
27480 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27481 and the search path contains @file{/home/user} then @value{GDBN} will
27482 look for the script @file{/home/user/mylib/myscript}.
27483 The search is also done if @var{filename} is an absolute path.
27484 For example, if @var{filename} is @file{/tmp/myscript} and
27485 the search path contains @file{/home/user} then @value{GDBN} will
27486 look for the script @file{/home/user/tmp/myscript}.
27487 For DOS-like systems, if @var{filename} contains a drive specification,
27488 it is stripped before concatenation. For example, if @var{filename} is
27489 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27490 will look for the script @file{c:/tmp/myscript}.
27492 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27493 each command as it is executed. The option must be given before
27494 @var{filename}, and is interpreted as part of the filename anywhere else.
27496 Commands that would ask for confirmation if used interactively proceed
27497 without asking when used in a command file. Many @value{GDBN} commands that
27498 normally print messages to say what they are doing omit the messages
27499 when called from command files.
27501 @value{GDBN} also accepts command input from standard input. In this
27502 mode, normal output goes to standard output and error output goes to
27503 standard error. Errors in a command file supplied on standard input do
27504 not terminate execution of the command file---execution continues with
27508 gdb < cmds > log 2>&1
27511 (The syntax above will vary depending on the shell used.) This example
27512 will execute commands from the file @file{cmds}. All output and errors
27513 would be directed to @file{log}.
27515 Since commands stored on command files tend to be more general than
27516 commands typed interactively, they frequently need to deal with
27517 complicated situations, such as different or unexpected values of
27518 variables and symbols, changes in how the program being debugged is
27519 built, etc. @value{GDBN} provides a set of flow-control commands to
27520 deal with these complexities. Using these commands, you can write
27521 complex scripts that loop over data structures, execute commands
27522 conditionally, etc.
27529 This command allows to include in your script conditionally executed
27530 commands. The @code{if} command takes a single argument, which is an
27531 expression to evaluate. It is followed by a series of commands that
27532 are executed only if the expression is true (its value is nonzero).
27533 There can then optionally be an @code{else} line, followed by a series
27534 of commands that are only executed if the expression was false. The
27535 end of the list is marked by a line containing @code{end}.
27539 This command allows to write loops. Its syntax is similar to
27540 @code{if}: the command takes a single argument, which is an expression
27541 to evaluate, and must be followed by the commands to execute, one per
27542 line, terminated by an @code{end}. These commands are called the
27543 @dfn{body} of the loop. The commands in the body of @code{while} are
27544 executed repeatedly as long as the expression evaluates to true.
27548 This command exits the @code{while} loop in whose body it is included.
27549 Execution of the script continues after that @code{while}s @code{end}
27552 @kindex loop_continue
27553 @item loop_continue
27554 This command skips the execution of the rest of the body of commands
27555 in the @code{while} loop in whose body it is included. Execution
27556 branches to the beginning of the @code{while} loop, where it evaluates
27557 the controlling expression.
27559 @kindex end@r{ (if/else/while commands)}
27561 Terminate the block of commands that are the body of @code{if},
27562 @code{else}, or @code{while} flow-control commands.
27567 @subsection Commands for Controlled Output
27569 During the execution of a command file or a user-defined command, normal
27570 @value{GDBN} output is suppressed; the only output that appears is what is
27571 explicitly printed by the commands in the definition. This section
27572 describes three commands useful for generating exactly the output you
27577 @item echo @var{text}
27578 @c I do not consider backslash-space a standard C escape sequence
27579 @c because it is not in ANSI.
27580 Print @var{text}. Nonprinting characters can be included in
27581 @var{text} using C escape sequences, such as @samp{\n} to print a
27582 newline. @strong{No newline is printed unless you specify one.}
27583 In addition to the standard C escape sequences, a backslash followed
27584 by a space stands for a space. This is useful for displaying a
27585 string with spaces at the beginning or the end, since leading and
27586 trailing spaces are otherwise trimmed from all arguments.
27587 To print @samp{@w{ }and foo =@w{ }}, use the command
27588 @samp{echo \@w{ }and foo = \@w{ }}.
27590 A backslash at the end of @var{text} can be used, as in C, to continue
27591 the command onto subsequent lines. For example,
27594 echo This is some text\n\
27595 which is continued\n\
27596 onto several lines.\n
27599 produces the same output as
27602 echo This is some text\n
27603 echo which is continued\n
27604 echo onto several lines.\n
27608 @item output @var{expression}
27609 Print the value of @var{expression} and nothing but that value: no
27610 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27611 value history either. @xref{Expressions, ,Expressions}, for more information
27614 @item output/@var{fmt} @var{expression}
27615 Print the value of @var{expression} in format @var{fmt}. You can use
27616 the same formats as for @code{print}. @xref{Output Formats,,Output
27617 Formats}, for more information.
27620 @item printf @var{template}, @var{expressions}@dots{}
27621 Print the values of one or more @var{expressions} under the control of
27622 the string @var{template}. To print several values, make
27623 @var{expressions} be a comma-separated list of individual expressions,
27624 which may be either numbers or pointers. Their values are printed as
27625 specified by @var{template}, exactly as a C program would do by
27626 executing the code below:
27629 printf (@var{template}, @var{expressions}@dots{});
27632 As in @code{C} @code{printf}, ordinary characters in @var{template}
27633 are printed verbatim, while @dfn{conversion specification} introduced
27634 by the @samp{%} character cause subsequent @var{expressions} to be
27635 evaluated, their values converted and formatted according to type and
27636 style information encoded in the conversion specifications, and then
27639 For example, you can print two values in hex like this:
27642 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27645 @code{printf} supports all the standard @code{C} conversion
27646 specifications, including the flags and modifiers between the @samp{%}
27647 character and the conversion letter, with the following exceptions:
27651 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27654 The modifier @samp{*} is not supported for specifying precision or
27658 The @samp{'} flag (for separation of digits into groups according to
27659 @code{LC_NUMERIC'}) is not supported.
27662 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27666 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27669 The conversion letters @samp{a} and @samp{A} are not supported.
27673 Note that the @samp{ll} type modifier is supported only if the
27674 underlying @code{C} implementation used to build @value{GDBN} supports
27675 the @code{long long int} type, and the @samp{L} type modifier is
27676 supported only if @code{long double} type is available.
27678 As in @code{C}, @code{printf} supports simple backslash-escape
27679 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27680 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27681 single character. Octal and hexadecimal escape sequences are not
27684 Additionally, @code{printf} supports conversion specifications for DFP
27685 (@dfn{Decimal Floating Point}) types using the following length modifiers
27686 together with a floating point specifier.
27691 @samp{H} for printing @code{Decimal32} types.
27694 @samp{D} for printing @code{Decimal64} types.
27697 @samp{DD} for printing @code{Decimal128} types.
27700 If the underlying @code{C} implementation used to build @value{GDBN} has
27701 support for the three length modifiers for DFP types, other modifiers
27702 such as width and precision will also be available for @value{GDBN} to use.
27704 In case there is no such @code{C} support, no additional modifiers will be
27705 available and the value will be printed in the standard way.
27707 Here's an example of printing DFP types using the above conversion letters:
27709 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27714 @item eval @var{template}, @var{expressions}@dots{}
27715 Convert the values of one or more @var{expressions} under the control of
27716 the string @var{template} to a command line, and call it.
27720 @node Auto-loading sequences
27721 @subsection Controlling auto-loading native @value{GDBN} scripts
27722 @cindex native script auto-loading
27724 When a new object file is read (for example, due to the @code{file}
27725 command, or because the inferior has loaded a shared library),
27726 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27727 @xref{Auto-loading extensions}.
27729 Auto-loading can be enabled or disabled,
27730 and the list of auto-loaded scripts can be printed.
27733 @anchor{set auto-load gdb-scripts}
27734 @kindex set auto-load gdb-scripts
27735 @item set auto-load gdb-scripts [on|off]
27736 Enable or disable the auto-loading of canned sequences of commands scripts.
27738 @anchor{show auto-load gdb-scripts}
27739 @kindex show auto-load gdb-scripts
27740 @item show auto-load gdb-scripts
27741 Show whether auto-loading of canned sequences of commands scripts is enabled or
27744 @anchor{info auto-load gdb-scripts}
27745 @kindex info auto-load gdb-scripts
27746 @cindex print list of auto-loaded canned sequences of commands scripts
27747 @item info auto-load gdb-scripts [@var{regexp}]
27748 Print the list of all canned sequences of commands scripts that @value{GDBN}
27752 If @var{regexp} is supplied only canned sequences of commands scripts with
27753 matching names are printed.
27756 @section Command Aliases
27757 @cindex aliases for commands
27759 Aliases allow you to define alternate spellings for existing commands.
27760 For example, if a new @value{GDBN} command defined in Python
27761 (@pxref{Python}) has a long name, it is handy to have an abbreviated
27762 version of it that involves less typing.
27764 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27765 of the @samp{step} command even though it is otherwise an ambiguous
27766 abbreviation of other commands like @samp{set} and @samp{show}.
27768 Aliases are also used to provide shortened or more common versions
27769 of multi-word commands. For example, @value{GDBN} provides the
27770 @samp{tty} alias of the @samp{set inferior-tty} command.
27772 You can define a new alias with the @samp{alias} command.
27777 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
27781 @var{alias} specifies the name of the new alias. Each word of
27782 @var{alias} must consist of letters, numbers, dashes and underscores.
27784 @var{command} specifies the name of an existing command
27785 that is being aliased.
27787 @var{command} can also be the name of an existing alias. In this
27788 case, @var{command} cannot be an alias that has default arguments.
27790 The @samp{-a} option specifies that the new alias is an abbreviation
27791 of the command. Abbreviations are not used in command completion.
27793 The @samp{--} option specifies the end of options,
27794 and is useful when @var{alias} begins with a dash.
27796 You can specify @var{default-args} for your alias. These
27797 @var{default-args} will be automatically added before the alias
27798 arguments typed explicitly on the command line.
27800 For example, the below defines an alias @code{btfullall} that shows all local
27801 variables and all frame arguments:
27803 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
27806 For more information about @var{default-args}, see @ref{Command
27807 aliases default args, ,Default Arguments}.
27809 Here is a simple example showing how to make an abbreviation of a
27810 command so that there is less to type. Suppose you were tired of
27811 typing @samp{disas}, the current shortest unambiguous abbreviation of
27812 the @samp{disassemble} command and you wanted an even shorter version
27813 named @samp{di}. The following will accomplish this.
27816 (gdb) alias -a di = disas
27819 Note that aliases are different from user-defined commands. With a
27820 user-defined command, you also need to write documentation for it with
27821 the @samp{document} command. An alias automatically picks up the
27822 documentation of the existing command.
27824 Here is an example where we make @samp{elms} an abbreviation of
27825 @samp{elements} in the @samp{set print elements} command.
27826 This is to show that you can make an abbreviation of any part
27830 (gdb) alias -a set print elms = set print elements
27831 (gdb) alias -a show print elms = show print elements
27832 (gdb) set p elms 20
27834 Limit on string chars or array elements to print is 200.
27837 Note that if you are defining an alias of a @samp{set} command,
27838 and you want to have an alias for the corresponding @samp{show}
27839 command, then you need to define the latter separately.
27841 Unambiguously abbreviated commands are allowed in @var{command} and
27842 @var{alias}, just as they are normally.
27845 (gdb) alias -a set pr elms = set p ele
27848 Finally, here is an example showing the creation of a one word
27849 alias for a more complex command.
27850 This creates alias @samp{spe} of the command @samp{set print elements}.
27853 (gdb) alias spe = set print elements
27858 * Command aliases default args:: Default arguments for aliases
27861 @node Command aliases default args
27862 @subsection Default Arguments
27863 @cindex aliases for commands, default arguments
27865 You can tell @value{GDBN} to always prepend some default arguments to
27866 the list of arguments provided explicitly by the user when using a
27867 user-defined alias.
27869 If you repeatedly use the same arguments or options for a command, you
27870 can define an alias for this command and tell @value{GDBN} to
27871 automatically prepend these arguments or options to the list of
27872 arguments you type explicitly when using the alias@footnote{@value{GDBN}
27873 could easily accept default arguments for pre-defined commands and aliases,
27874 but it was deemed this would be confusing, and so is not allowed.}.
27876 For example, if you often use the command @code{thread apply all}
27877 specifying to work on the threads in ascending order and to continue in case it
27878 encounters an error, you can tell @value{GDBN} to automatically preprend
27879 the @code{-ascending} and @code{-c} options by using:
27882 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
27885 Once you have defined this alias with its default args, any time you type
27886 the @code{thread apply asc-all} followed by @code{some arguments},
27887 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
27889 To have even less to type, you can also define a one word alias:
27891 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
27894 As usual, unambiguous abbreviations can be used for @var{alias}
27895 and @var{default-args}.
27897 The different aliases of a command do not share their default args.
27898 For example, you define a new alias @code{bt_ALL} showing all possible
27899 information and another alias @code{bt_SMALL} showing very limited information
27902 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
27903 -past-main -past-entry -full
27904 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
27905 -past-main off -past-entry off
27908 (For more on using the @code{alias} command, see @ref{Aliases}.)
27910 Default args are not limited to the arguments and options of @var{command},
27911 but can specify nested commands if @var{command} accepts such a nested command
27913 For example, the below defines @code{faalocalsoftype} that lists the
27914 frames having locals of a certain type, together with the matching
27917 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
27918 (@value{GDBP}) faalocalsoftype int
27919 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
27924 This is also very useful to define an alias for a set of nested @code{with}
27925 commands to have a particular combination of temporary settings. For example,
27926 the below defines the alias @code{pp10} that pretty prints an expression
27927 argument, with a maximum of 10 elements if the expression is a string or
27930 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
27932 This defines the alias @code{pp10} as being a sequence of 3 commands.
27933 The first part @code{with print pretty --} temporarily activates the setting
27934 @code{set print pretty}, then launches the command that follows the separator
27936 The command following the first part is also a @code{with} command that
27937 temporarily changes the setting @code{set print elements} to 10, then
27938 launches the command that follows the second separator @code{--}.
27939 The third part @code{print} is the command the @code{pp10} alias will launch,
27940 using the temporary values of the settings and the arguments explicitly given
27942 For more information about the @code{with} command usage,
27943 see @ref{Command Settings}.
27945 @c Python docs live in a separate file.
27946 @include python.texi
27948 @c Guile docs live in a separate file.
27949 @include guile.texi
27951 @node Auto-loading extensions
27952 @section Auto-loading extensions
27953 @cindex auto-loading extensions
27955 @value{GDBN} provides two mechanisms for automatically loading
27956 extensions when a new object file is read (for example, due to the
27957 @code{file} command, or because the inferior has loaded a shared
27958 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
27959 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
27960 @code{.debug_gdb_scripts} section of modern file formats like ELF
27961 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
27962 section}). For a discussion of the differences between these two
27963 approaches see @ref{Which flavor to choose?}.
27965 The auto-loading feature is useful for supplying application-specific
27966 debugging commands and features.
27968 Auto-loading can be enabled or disabled,
27969 and the list of auto-loaded scripts can be printed.
27970 See the @samp{auto-loading} section of each extension language
27971 for more information.
27972 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27973 For Python files see @ref{Python Auto-loading}.
27975 Note that loading of this script file also requires accordingly configured
27976 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27979 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
27980 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27981 * Which flavor to choose?:: Choosing between these approaches
27984 @node objfile-gdbdotext file
27985 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27986 @cindex @file{@var{objfile}-gdb.gdb}
27987 @cindex @file{@var{objfile}-gdb.py}
27988 @cindex @file{@var{objfile}-gdb.scm}
27990 When a new object file is read, @value{GDBN} looks for a file named
27991 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27992 where @var{objfile} is the object file's name and
27993 where @var{ext} is the file extension for the extension language:
27996 @item @file{@var{objfile}-gdb.gdb}
27997 GDB's own command language
27998 @item @file{@var{objfile}-gdb.py}
28000 @item @file{@var{objfile}-gdb.scm}
28004 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28005 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28006 components, and appending the @file{-gdb.@var{ext}} suffix.
28007 If this file exists and is readable, @value{GDBN} will evaluate it as a
28008 script in the specified extension language.
28010 If this file does not exist, then @value{GDBN} will look for
28011 @var{script-name} file in all of the directories as specified below.
28012 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28013 directories is converted to a one-letter subdirectory, i.e.@:
28014 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28015 filesystems disallow colons in file names.)
28017 Note that loading of these files requires an accordingly configured
28018 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28020 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28021 scripts normally according to its @file{.exe} filename. But if no scripts are
28022 found @value{GDBN} also tries script filenames matching the object file without
28023 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28024 is attempted on any platform. This makes the script filenames compatible
28025 between Unix and MS-Windows hosts.
28028 @anchor{set auto-load scripts-directory}
28029 @kindex set auto-load scripts-directory
28030 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28031 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28032 may be delimited by the host platform path separator in use
28033 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28035 Each entry here needs to be covered also by the security setting
28036 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28038 @anchor{with-auto-load-dir}
28039 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28040 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28041 configuration option @option{--with-auto-load-dir}.
28043 Any reference to @file{$debugdir} will get replaced by
28044 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28045 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28046 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28047 @file{$datadir} must be placed as a directory component --- either alone or
28048 delimited by @file{/} or @file{\} directory separators, depending on the host
28051 The list of directories uses path separator (@samp{:} on GNU and Unix
28052 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28053 to the @env{PATH} environment variable.
28055 @anchor{show auto-load scripts-directory}
28056 @kindex show auto-load scripts-directory
28057 @item show auto-load scripts-directory
28058 Show @value{GDBN} auto-loaded scripts location.
28060 @anchor{add-auto-load-scripts-directory}
28061 @kindex add-auto-load-scripts-directory
28062 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28063 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28064 Multiple entries may be delimited by the host platform path separator in use.
28067 @value{GDBN} does not track which files it has already auto-loaded this way.
28068 @value{GDBN} will load the associated script every time the corresponding
28069 @var{objfile} is opened.
28070 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28071 is evaluated more than once.
28073 @node dotdebug_gdb_scripts section
28074 @subsection The @code{.debug_gdb_scripts} section
28075 @cindex @code{.debug_gdb_scripts} section
28077 For systems using file formats like ELF and COFF,
28078 when @value{GDBN} loads a new object file
28079 it will look for a special section named @code{.debug_gdb_scripts}.
28080 If this section exists, its contents is a list of null-terminated entries
28081 specifying scripts to load. Each entry begins with a non-null prefix byte that
28082 specifies the kind of entry, typically the extension language and whether the
28083 script is in a file or inlined in @code{.debug_gdb_scripts}.
28085 The following entries are supported:
28088 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28089 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28090 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28091 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28094 @subsubsection Script File Entries
28096 If the entry specifies a file, @value{GDBN} will look for the file first
28097 in the current directory and then along the source search path
28098 (@pxref{Source Path, ,Specifying Source Directories}),
28099 except that @file{$cdir} is not searched, since the compilation
28100 directory is not relevant to scripts.
28102 File entries can be placed in section @code{.debug_gdb_scripts} with,
28103 for example, this GCC macro for Python scripts.
28106 /* Note: The "MS" section flags are to remove duplicates. */
28107 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28109 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28110 .byte 1 /* Python */\n\
28111 .asciz \"" script_name "\"\n\
28117 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28118 Then one can reference the macro in a header or source file like this:
28121 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28124 The script name may include directories if desired.
28126 Note that loading of this script file also requires accordingly configured
28127 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28129 If the macro invocation is put in a header, any application or library
28130 using this header will get a reference to the specified script,
28131 and with the use of @code{"MS"} attributes on the section, the linker
28132 will remove duplicates.
28134 @subsubsection Script Text Entries
28136 Script text entries allow to put the executable script in the entry
28137 itself instead of loading it from a file.
28138 The first line of the entry, everything after the prefix byte and up to
28139 the first newline (@code{0xa}) character, is the script name, and must not
28140 contain any kind of space character, e.g., spaces or tabs.
28141 The rest of the entry, up to the trailing null byte, is the script to
28142 execute in the specified language. The name needs to be unique among
28143 all script names, as @value{GDBN} executes each script only once based
28146 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28150 #include "symcat.h"
28151 #include "gdb/section-scripts.h"
28153 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28154 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28155 ".ascii \"gdb.inlined-script\\n\"\n"
28156 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28157 ".ascii \" def __init__ (self):\\n\"\n"
28158 ".ascii \" super (test_cmd, self).__init__ ("
28159 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28160 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28161 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28162 ".ascii \"test_cmd ()\\n\"\n"
28168 Loading of inlined scripts requires a properly configured
28169 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28170 The path to specify in @code{auto-load safe-path} is the path of the file
28171 containing the @code{.debug_gdb_scripts} section.
28173 @node Which flavor to choose?
28174 @subsection Which flavor to choose?
28176 Given the multiple ways of auto-loading extensions, it might not always
28177 be clear which one to choose. This section provides some guidance.
28180 Benefits of the @file{-gdb.@var{ext}} way:
28184 Can be used with file formats that don't support multiple sections.
28187 Ease of finding scripts for public libraries.
28189 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28190 in the source search path.
28191 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28192 isn't a source directory in which to find the script.
28195 Doesn't require source code additions.
28199 Benefits of the @code{.debug_gdb_scripts} way:
28203 Works with static linking.
28205 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28206 trigger their loading. When an application is statically linked the only
28207 objfile available is the executable, and it is cumbersome to attach all the
28208 scripts from all the input libraries to the executable's
28209 @file{-gdb.@var{ext}} script.
28212 Works with classes that are entirely inlined.
28214 Some classes can be entirely inlined, and thus there may not be an associated
28215 shared library to attach a @file{-gdb.@var{ext}} script to.
28218 Scripts needn't be copied out of the source tree.
28220 In some circumstances, apps can be built out of large collections of internal
28221 libraries, and the build infrastructure necessary to install the
28222 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28223 cumbersome. It may be easier to specify the scripts in the
28224 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28225 top of the source tree to the source search path.
28228 @node Multiple Extension Languages
28229 @section Multiple Extension Languages
28231 The Guile and Python extension languages do not share any state,
28232 and generally do not interfere with each other.
28233 There are some things to be aware of, however.
28235 @subsection Python comes first
28237 Python was @value{GDBN}'s first extension language, and to avoid breaking
28238 existing behaviour Python comes first. This is generally solved by the
28239 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28240 extension languages, and when it makes a call to an extension language,
28241 (say to pretty-print a value), it tries each in turn until an extension
28242 language indicates it has performed the request (e.g., has returned the
28243 pretty-printed form of a value).
28244 This extends to errors while performing such requests: If an error happens
28245 while, for example, trying to pretty-print an object then the error is
28246 reported and any following extension languages are not tried.
28249 @chapter Command Interpreters
28250 @cindex command interpreters
28252 @value{GDBN} supports multiple command interpreters, and some command
28253 infrastructure to allow users or user interface writers to switch
28254 between interpreters or run commands in other interpreters.
28256 @value{GDBN} currently supports two command interpreters, the console
28257 interpreter (sometimes called the command-line interpreter or @sc{cli})
28258 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28259 describes both of these interfaces in great detail.
28261 By default, @value{GDBN} will start with the console interpreter.
28262 However, the user may choose to start @value{GDBN} with another
28263 interpreter by specifying the @option{-i} or @option{--interpreter}
28264 startup options. Defined interpreters include:
28268 @cindex console interpreter
28269 The traditional console or command-line interpreter. This is the most often
28270 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28271 @value{GDBN} will use this interpreter.
28274 @cindex mi interpreter
28275 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28276 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28277 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28281 @cindex mi3 interpreter
28282 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28285 @cindex mi2 interpreter
28286 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28289 @cindex mi1 interpreter
28290 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28294 @cindex invoke another interpreter
28296 @kindex interpreter-exec
28297 You may execute commands in any interpreter from the current
28298 interpreter using the appropriate command. If you are running the
28299 console interpreter, simply use the @code{interpreter-exec} command:
28302 interpreter-exec mi "-data-list-register-names"
28305 @sc{gdb/mi} has a similar command, although it is only available in versions of
28306 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28308 Note that @code{interpreter-exec} only changes the interpreter for the
28309 duration of the specified command. It does not change the interpreter
28312 @cindex start a new independent interpreter
28314 Although you may only choose a single interpreter at startup, it is
28315 possible to run an independent interpreter on a specified input/output
28316 device (usually a tty).
28318 For example, consider a debugger GUI or IDE that wants to provide a
28319 @value{GDBN} console view. It may do so by embedding a terminal
28320 emulator widget in its GUI, starting @value{GDBN} in the traditional
28321 command-line mode with stdin/stdout/stderr redirected to that
28322 terminal, and then creating an MI interpreter running on a specified
28323 input/output device. The console interpreter created by @value{GDBN}
28324 at startup handles commands the user types in the terminal widget,
28325 while the GUI controls and synchronizes state with @value{GDBN} using
28326 the separate MI interpreter.
28328 To start a new secondary @dfn{user interface} running MI, use the
28329 @code{new-ui} command:
28332 @cindex new user interface
28334 new-ui @var{interpreter} @var{tty}
28337 The @var{interpreter} parameter specifies the interpreter to run.
28338 This accepts the same values as the @code{interpreter-exec} command.
28339 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28340 @var{tty} parameter specifies the name of the bidirectional file the
28341 interpreter uses for input/output, usually the name of a
28342 pseudoterminal slave on Unix systems. For example:
28345 (@value{GDBP}) new-ui mi /dev/pts/9
28349 runs an MI interpreter on @file{/dev/pts/9}.
28352 @chapter @value{GDBN} Text User Interface
28354 @cindex Text User Interface
28356 The @value{GDBN} Text User Interface (TUI) is a terminal
28357 interface which uses the @code{curses} library to show the source
28358 file, the assembly output, the program registers and @value{GDBN}
28359 commands in separate text windows. The TUI mode is supported only
28360 on platforms where a suitable version of the @code{curses} library
28363 The TUI mode is enabled by default when you invoke @value{GDBN} as
28364 @samp{@value{GDBP} -tui}.
28365 You can also switch in and out of TUI mode while @value{GDBN} runs by
28366 using various TUI commands and key bindings, such as @command{tui
28367 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28368 @ref{TUI Keys, ,TUI Key Bindings}.
28371 * TUI Overview:: TUI overview
28372 * TUI Keys:: TUI key bindings
28373 * TUI Single Key Mode:: TUI single key mode
28374 * TUI Commands:: TUI-specific commands
28375 * TUI Configuration:: TUI configuration variables
28379 @section TUI Overview
28381 In TUI mode, @value{GDBN} can display several text windows:
28385 This window is the @value{GDBN} command window with the @value{GDBN}
28386 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28387 managed using readline.
28390 The source window shows the source file of the program. The current
28391 line and active breakpoints are displayed in this window.
28394 The assembly window shows the disassembly output of the program.
28397 This window shows the processor registers. Registers are highlighted
28398 when their values change.
28401 The source and assembly windows show the current program position
28402 by highlighting the current line and marking it with a @samp{>} marker.
28403 Breakpoints are indicated with two markers. The first marker
28404 indicates the breakpoint type:
28408 Breakpoint which was hit at least once.
28411 Breakpoint which was never hit.
28414 Hardware breakpoint which was hit at least once.
28417 Hardware breakpoint which was never hit.
28420 The second marker indicates whether the breakpoint is enabled or not:
28424 Breakpoint is enabled.
28427 Breakpoint is disabled.
28430 The source, assembly and register windows are updated when the current
28431 thread changes, when the frame changes, or when the program counter
28434 These windows are not all visible at the same time. The command
28435 window is always visible. The others can be arranged in several
28446 source and assembly,
28449 source and registers, or
28452 assembly and registers.
28455 These are the standard layouts, but other layouts can be defined.
28457 A status line above the command window shows the following information:
28461 Indicates the current @value{GDBN} target.
28462 (@pxref{Targets, ,Specifying a Debugging Target}).
28465 Gives the current process or thread number.
28466 When no process is being debugged, this field is set to @code{No process}.
28469 Gives the current function name for the selected frame.
28470 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28471 When there is no symbol corresponding to the current program counter,
28472 the string @code{??} is displayed.
28475 Indicates the current line number for the selected frame.
28476 When the current line number is not known, the string @code{??} is displayed.
28479 Indicates the current program counter address.
28483 @section TUI Key Bindings
28484 @cindex TUI key bindings
28486 The TUI installs several key bindings in the readline keymaps
28487 @ifset SYSTEM_READLINE
28488 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28490 @ifclear SYSTEM_READLINE
28491 (@pxref{Command Line Editing}).
28493 The following key bindings are installed for both TUI mode and the
28494 @value{GDBN} standard mode.
28503 Enter or leave the TUI mode. When leaving the TUI mode,
28504 the curses window management stops and @value{GDBN} operates using
28505 its standard mode, writing on the terminal directly. When reentering
28506 the TUI mode, control is given back to the curses windows.
28507 The screen is then refreshed.
28509 This key binding uses the bindable Readline function
28510 @code{tui-switch-mode}.
28514 Use a TUI layout with only one window. The layout will
28515 either be @samp{source} or @samp{assembly}. When the TUI mode
28516 is not active, it will switch to the TUI mode.
28518 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28520 This key binding uses the bindable Readline function
28521 @code{tui-delete-other-windows}.
28525 Use a TUI layout with at least two windows. When the current
28526 layout already has two windows, the next layout with two windows is used.
28527 When a new layout is chosen, one window will always be common to the
28528 previous layout and the new one.
28530 Think of it as the Emacs @kbd{C-x 2} binding.
28532 This key binding uses the bindable Readline function
28533 @code{tui-change-windows}.
28537 Change the active window. The TUI associates several key bindings
28538 (like scrolling and arrow keys) with the active window. This command
28539 gives the focus to the next TUI window.
28541 Think of it as the Emacs @kbd{C-x o} binding.
28543 This key binding uses the bindable Readline function
28544 @code{tui-other-window}.
28548 Switch in and out of the TUI SingleKey mode that binds single
28549 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28551 This key binding uses the bindable Readline function
28552 @code{next-keymap}.
28555 The following key bindings only work in the TUI mode:
28560 Scroll the active window one page up.
28564 Scroll the active window one page down.
28568 Scroll the active window one line up.
28572 Scroll the active window one line down.
28576 Scroll the active window one column left.
28580 Scroll the active window one column right.
28584 Refresh the screen.
28587 Because the arrow keys scroll the active window in the TUI mode, they
28588 are not available for their normal use by readline unless the command
28589 window has the focus. When another window is active, you must use
28590 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28591 and @kbd{C-f} to control the command window.
28593 @node TUI Single Key Mode
28594 @section TUI Single Key Mode
28595 @cindex TUI single key mode
28597 The TUI also provides a @dfn{SingleKey} mode, which binds several
28598 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28599 switch into this mode, where the following key bindings are used:
28602 @kindex c @r{(SingleKey TUI key)}
28606 @kindex d @r{(SingleKey TUI key)}
28610 @kindex f @r{(SingleKey TUI key)}
28614 @kindex n @r{(SingleKey TUI key)}
28618 @kindex o @r{(SingleKey TUI key)}
28620 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28622 @kindex q @r{(SingleKey TUI key)}
28624 exit the SingleKey mode.
28626 @kindex r @r{(SingleKey TUI key)}
28630 @kindex s @r{(SingleKey TUI key)}
28634 @kindex i @r{(SingleKey TUI key)}
28636 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28638 @kindex u @r{(SingleKey TUI key)}
28642 @kindex v @r{(SingleKey TUI key)}
28646 @kindex w @r{(SingleKey TUI key)}
28651 Other keys temporarily switch to the @value{GDBN} command prompt.
28652 The key that was pressed is inserted in the editing buffer so that
28653 it is possible to type most @value{GDBN} commands without interaction
28654 with the TUI SingleKey mode. Once the command is entered the TUI
28655 SingleKey mode is restored. The only way to permanently leave
28656 this mode is by typing @kbd{q} or @kbd{C-x s}.
28658 @cindex SingleKey keymap name
28659 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28660 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28661 @file{.inputrc} to add additional bindings to this keymap.
28664 @section TUI-specific Commands
28665 @cindex TUI commands
28667 The TUI has specific commands to control the text windows.
28668 These commands are always available, even when @value{GDBN} is not in
28669 the TUI mode. When @value{GDBN} is in the standard mode, most
28670 of these commands will automatically switch to the TUI mode.
28672 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28673 terminal, or @value{GDBN} has been started with the machine interface
28674 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28675 these commands will fail with an error, because it would not be
28676 possible or desirable to enable curses window management.
28681 Activate TUI mode. The last active TUI window layout will be used if
28682 TUI mode has previously been used in the current debugging session,
28683 otherwise a default layout is used.
28686 @kindex tui disable
28687 Disable TUI mode, returning to the console interpreter.
28691 List and give the size of all displayed windows.
28693 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28694 @kindex tui new-layout
28695 Create a new TUI layout. The new layout will be named @var{name}, and
28696 can be accessed using the @code{layout} command (see below).
28698 Each @var{window} parameter is either the name of a window to display,
28699 or a window description. The windows will be displayed from top to
28700 bottom in the order listed.
28702 The names of the windows are the same as the ones given to the
28703 @code{focus} command (see below); additional, the @code{status}
28704 window can be specified. Note that, because it is of fixed height,
28705 the weight assigned to the status window is of no importance. It is
28706 conventional to use @samp{0} here.
28708 A window description looks a bit like an invocation of @code{tui
28709 new-layout}, and is of the form
28710 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28712 This specifies a sub-layout. If @code{-horizontal} is given, the
28713 windows in this description will be arranged side-by-side, rather than
28716 Each @var{weight} is an integer. It is the weight of this window
28717 relative to all the other windows in the layout. These numbers are
28718 used to calculate how much of the screen is given to each window.
28723 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28726 Here, the new layout is called @samp{example}. It shows the source
28727 and register windows, followed by the status window, and then finally
28728 the command window. The non-status windows all have the same weight,
28729 so the terminal will be split into three roughly equal sections.
28731 Here is a more complex example, showing a horizontal layout:
28734 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28737 This will result in side-by-side source and assembly windows; with the
28738 status and command window being beneath these, filling the entire
28739 width of the terminal. Because they have weight 2, the source and
28740 assembly windows will be twice the height of the command window.
28742 @item layout @var{name}
28744 Changes which TUI windows are displayed. The @var{name} parameter
28745 controls which layout is shown. It can be either one of the built-in
28746 layout names, or the name of a layout defined by the user using
28747 @code{tui new-layout}.
28749 The built-in layouts are as follows:
28753 Display the next layout.
28756 Display the previous layout.
28759 Display the source and command windows.
28762 Display the assembly and command windows.
28765 Display the source, assembly, and command windows.
28768 When in @code{src} layout display the register, source, and command
28769 windows. When in @code{asm} or @code{split} layout display the
28770 register, assembler, and command windows.
28773 @item focus @var{name}
28775 Changes which TUI window is currently active for scrolling. The
28776 @var{name} parameter can be any of the following:
28780 Make the next window active for scrolling.
28783 Make the previous window active for scrolling.
28786 Make the source window active for scrolling.
28789 Make the assembly window active for scrolling.
28792 Make the register window active for scrolling.
28795 Make the command window active for scrolling.
28800 Refresh the screen. This is similar to typing @kbd{C-L}.
28802 @item tui reg @var{group}
28804 Changes the register group displayed in the tui register window to
28805 @var{group}. If the register window is not currently displayed this
28806 command will cause the register window to be displayed. The list of
28807 register groups, as well as their order is target specific. The
28808 following groups are available on most targets:
28811 Repeatedly selecting this group will cause the display to cycle
28812 through all of the available register groups.
28815 Repeatedly selecting this group will cause the display to cycle
28816 through all of the available register groups in the reverse order to
28820 Display the general registers.
28822 Display the floating point registers.
28824 Display the system registers.
28826 Display the vector registers.
28828 Display all registers.
28833 Update the source window and the current execution point.
28835 @item winheight @var{name} +@var{count}
28836 @itemx winheight @var{name} -@var{count}
28838 Change the height of the window @var{name} by @var{count}
28839 lines. Positive counts increase the height, while negative counts
28840 decrease it. The @var{name} parameter can be one of @code{src} (the
28841 source window), @code{cmd} (the command window), @code{asm} (the
28842 disassembly window), or @code{regs} (the register display window).
28845 @node TUI Configuration
28846 @section TUI Configuration Variables
28847 @cindex TUI configuration variables
28849 Several configuration variables control the appearance of TUI windows.
28852 @item set tui border-kind @var{kind}
28853 @kindex set tui border-kind
28854 Select the border appearance for the source, assembly and register windows.
28855 The possible values are the following:
28858 Use a space character to draw the border.
28861 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28864 Use the Alternate Character Set to draw the border. The border is
28865 drawn using character line graphics if the terminal supports them.
28868 @item set tui border-mode @var{mode}
28869 @kindex set tui border-mode
28870 @itemx set tui active-border-mode @var{mode}
28871 @kindex set tui active-border-mode
28872 Select the display attributes for the borders of the inactive windows
28873 or the active window. The @var{mode} can be one of the following:
28876 Use normal attributes to display the border.
28882 Use reverse video mode.
28885 Use half bright mode.
28887 @item half-standout
28888 Use half bright and standout mode.
28891 Use extra bright or bold mode.
28893 @item bold-standout
28894 Use extra bright or bold and standout mode.
28897 @item set tui tab-width @var{nchars}
28898 @kindex set tui tab-width
28900 Set the width of tab stops to be @var{nchars} characters. This
28901 setting affects the display of TAB characters in the source and
28904 @item set tui compact-source @r{[}on@r{|}off@r{]}
28905 @kindex set tui compact-source
28906 Set whether the TUI source window is displayed in ``compact'' form.
28907 The default display uses more space for line numbers and starts the
28908 source text at the next tab stop; the compact display uses only as
28909 much space as is needed for the line numbers in the current file, and
28910 only a single space to separate the line numbers from the source.
28913 Note that the colors of the TUI borders can be controlled using the
28914 appropriate @code{set style} commands. @xref{Output Styling}.
28917 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28920 @cindex @sc{gnu} Emacs
28921 A special interface allows you to use @sc{gnu} Emacs to view (and
28922 edit) the source files for the program you are debugging with
28925 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28926 executable file you want to debug as an argument. This command starts
28927 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28928 created Emacs buffer.
28929 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28931 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28936 All ``terminal'' input and output goes through an Emacs buffer, called
28939 This applies both to @value{GDBN} commands and their output, and to the input
28940 and output done by the program you are debugging.
28942 This is useful because it means that you can copy the text of previous
28943 commands and input them again; you can even use parts of the output
28946 All the facilities of Emacs' Shell mode are available for interacting
28947 with your program. In particular, you can send signals the usual
28948 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28952 @value{GDBN} displays source code through Emacs.
28954 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28955 source file for that frame and puts an arrow (@samp{=>}) at the
28956 left margin of the current line. Emacs uses a separate buffer for
28957 source display, and splits the screen to show both your @value{GDBN} session
28960 Explicit @value{GDBN} @code{list} or search commands still produce output as
28961 usual, but you probably have no reason to use them from Emacs.
28964 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28965 a graphical mode, enabled by default, which provides further buffers
28966 that can control the execution and describe the state of your program.
28967 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28969 If you specify an absolute file name when prompted for the @kbd{M-x
28970 gdb} argument, then Emacs sets your current working directory to where
28971 your program resides. If you only specify the file name, then Emacs
28972 sets your current working directory to the directory associated
28973 with the previous buffer. In this case, @value{GDBN} may find your
28974 program by searching your environment's @env{PATH} variable, but on
28975 some operating systems it might not find the source. So, although the
28976 @value{GDBN} input and output session proceeds normally, the auxiliary
28977 buffer does not display the current source and line of execution.
28979 The initial working directory of @value{GDBN} is printed on the top
28980 line of the GUD buffer and this serves as a default for the commands
28981 that specify files for @value{GDBN} to operate on. @xref{Files,
28982 ,Commands to Specify Files}.
28984 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28985 need to call @value{GDBN} by a different name (for example, if you
28986 keep several configurations around, with different names) you can
28987 customize the Emacs variable @code{gud-gdb-command-name} to run the
28990 In the GUD buffer, you can use these special Emacs commands in
28991 addition to the standard Shell mode commands:
28995 Describe the features of Emacs' GUD Mode.
28998 Execute to another source line, like the @value{GDBN} @code{step} command; also
28999 update the display window to show the current file and location.
29002 Execute to next source line in this function, skipping all function
29003 calls, like the @value{GDBN} @code{next} command. Then update the display window
29004 to show the current file and location.
29007 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29008 display window accordingly.
29011 Execute until exit from the selected stack frame, like the @value{GDBN}
29012 @code{finish} command.
29015 Continue execution of your program, like the @value{GDBN} @code{continue}
29019 Go up the number of frames indicated by the numeric argument
29020 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29021 like the @value{GDBN} @code{up} command.
29024 Go down the number of frames indicated by the numeric argument, like the
29025 @value{GDBN} @code{down} command.
29028 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29029 tells @value{GDBN} to set a breakpoint on the source line point is on.
29031 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29032 separate frame which shows a backtrace when the GUD buffer is current.
29033 Move point to any frame in the stack and type @key{RET} to make it
29034 become the current frame and display the associated source in the
29035 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29036 selected frame become the current one. In graphical mode, the
29037 speedbar displays watch expressions.
29039 If you accidentally delete the source-display buffer, an easy way to get
29040 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29041 request a frame display; when you run under Emacs, this recreates
29042 the source buffer if necessary to show you the context of the current
29045 The source files displayed in Emacs are in ordinary Emacs buffers
29046 which are visiting the source files in the usual way. You can edit
29047 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29048 communicates with Emacs in terms of line numbers. If you add or
29049 delete lines from the text, the line numbers that @value{GDBN} knows cease
29050 to correspond properly with the code.
29052 A more detailed description of Emacs' interaction with @value{GDBN} is
29053 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29057 @chapter The @sc{gdb/mi} Interface
29059 @unnumberedsec Function and Purpose
29061 @cindex @sc{gdb/mi}, its purpose
29062 @sc{gdb/mi} is a line based machine oriented text interface to
29063 @value{GDBN} and is activated by specifying using the
29064 @option{--interpreter} command line option (@pxref{Mode Options}). It
29065 is specifically intended to support the development of systems which
29066 use the debugger as just one small component of a larger system.
29068 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29069 in the form of a reference manual.
29071 Note that @sc{gdb/mi} is still under construction, so some of the
29072 features described below are incomplete and subject to change
29073 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29075 @unnumberedsec Notation and Terminology
29077 @cindex notational conventions, for @sc{gdb/mi}
29078 This chapter uses the following notation:
29082 @code{|} separates two alternatives.
29085 @code{[ @var{something} ]} indicates that @var{something} is optional:
29086 it may or may not be given.
29089 @code{( @var{group} )*} means that @var{group} inside the parentheses
29090 may repeat zero or more times.
29093 @code{( @var{group} )+} means that @var{group} inside the parentheses
29094 may repeat one or more times.
29097 @code{"@var{string}"} means a literal @var{string}.
29101 @heading Dependencies
29105 * GDB/MI General Design::
29106 * GDB/MI Command Syntax::
29107 * GDB/MI Compatibility with CLI::
29108 * GDB/MI Development and Front Ends::
29109 * GDB/MI Output Records::
29110 * GDB/MI Simple Examples::
29111 * GDB/MI Command Description Format::
29112 * GDB/MI Breakpoint Commands::
29113 * GDB/MI Catchpoint Commands::
29114 * GDB/MI Program Context::
29115 * GDB/MI Thread Commands::
29116 * GDB/MI Ada Tasking Commands::
29117 * GDB/MI Program Execution::
29118 * GDB/MI Stack Manipulation::
29119 * GDB/MI Variable Objects::
29120 * GDB/MI Data Manipulation::
29121 * GDB/MI Tracepoint Commands::
29122 * GDB/MI Symbol Query::
29123 * GDB/MI File Commands::
29125 * GDB/MI Kod Commands::
29126 * GDB/MI Memory Overlay Commands::
29127 * GDB/MI Signal Handling Commands::
29129 * GDB/MI Target Manipulation::
29130 * GDB/MI File Transfer Commands::
29131 * GDB/MI Ada Exceptions Commands::
29132 * GDB/MI Support Commands::
29133 * GDB/MI Miscellaneous Commands::
29136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29137 @node GDB/MI General Design
29138 @section @sc{gdb/mi} General Design
29139 @cindex GDB/MI General Design
29141 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29142 parts---commands sent to @value{GDBN}, responses to those commands
29143 and notifications. Each command results in exactly one response,
29144 indicating either successful completion of the command, or an error.
29145 For the commands that do not resume the target, the response contains the
29146 requested information. For the commands that resume the target, the
29147 response only indicates whether the target was successfully resumed.
29148 Notifications is the mechanism for reporting changes in the state of the
29149 target, or in @value{GDBN} state, that cannot conveniently be associated with
29150 a command and reported as part of that command response.
29152 The important examples of notifications are:
29156 Exec notifications. These are used to report changes in
29157 target state---when a target is resumed, or stopped. It would not
29158 be feasible to include this information in response of resuming
29159 commands, because one resume commands can result in multiple events in
29160 different threads. Also, quite some time may pass before any event
29161 happens in the target, while a frontend needs to know whether the resuming
29162 command itself was successfully executed.
29165 Console output, and status notifications. Console output
29166 notifications are used to report output of CLI commands, as well as
29167 diagnostics for other commands. Status notifications are used to
29168 report the progress of a long-running operation. Naturally, including
29169 this information in command response would mean no output is produced
29170 until the command is finished, which is undesirable.
29173 General notifications. Commands may have various side effects on
29174 the @value{GDBN} or target state beyond their official purpose. For example,
29175 a command may change the selected thread. Although such changes can
29176 be included in command response, using notification allows for more
29177 orthogonal frontend design.
29181 There's no guarantee that whenever an MI command reports an error,
29182 @value{GDBN} or the target are in any specific state, and especially,
29183 the state is not reverted to the state before the MI command was
29184 processed. Therefore, whenever an MI command results in an error,
29185 we recommend that the frontend refreshes all the information shown in
29186 the user interface.
29190 * Context management::
29191 * Asynchronous and non-stop modes::
29195 @node Context management
29196 @subsection Context management
29198 @subsubsection Threads and Frames
29200 In most cases when @value{GDBN} accesses the target, this access is
29201 done in context of a specific thread and frame (@pxref{Frames}).
29202 Often, even when accessing global data, the target requires that a thread
29203 be specified. The CLI interface maintains the selected thread and frame,
29204 and supplies them to target on each command. This is convenient,
29205 because a command line user would not want to specify that information
29206 explicitly on each command, and because user interacts with
29207 @value{GDBN} via a single terminal, so no confusion is possible as
29208 to what thread and frame are the current ones.
29210 In the case of MI, the concept of selected thread and frame is less
29211 useful. First, a frontend can easily remember this information
29212 itself. Second, a graphical frontend can have more than one window,
29213 each one used for debugging a different thread, and the frontend might
29214 want to access additional threads for internal purposes. This
29215 increases the risk that by relying on implicitly selected thread, the
29216 frontend may be operating on a wrong one. Therefore, each MI command
29217 should explicitly specify which thread and frame to operate on. To
29218 make it possible, each MI command accepts the @samp{--thread} and
29219 @samp{--frame} options, the value to each is @value{GDBN} global
29220 identifier for thread and frame to operate on.
29222 Usually, each top-level window in a frontend allows the user to select
29223 a thread and a frame, and remembers the user selection for further
29224 operations. However, in some cases @value{GDBN} may suggest that the
29225 current thread or frame be changed. For example, when stopping on a
29226 breakpoint it is reasonable to switch to the thread where breakpoint is
29227 hit. For another example, if the user issues the CLI @samp{thread} or
29228 @samp{frame} commands via the frontend, it is desirable to change the
29229 frontend's selection to the one specified by user. @value{GDBN}
29230 communicates the suggestion to change current thread and frame using the
29231 @samp{=thread-selected} notification.
29233 Note that historically, MI shares the selected thread with CLI, so
29234 frontends used the @code{-thread-select} to execute commands in the
29235 right context. However, getting this to work right is cumbersome. The
29236 simplest way is for frontend to emit @code{-thread-select} command
29237 before every command. This doubles the number of commands that need
29238 to be sent. The alternative approach is to suppress @code{-thread-select}
29239 if the selected thread in @value{GDBN} is supposed to be identical to the
29240 thread the frontend wants to operate on. However, getting this
29241 optimization right can be tricky. In particular, if the frontend
29242 sends several commands to @value{GDBN}, and one of the commands changes the
29243 selected thread, then the behaviour of subsequent commands will
29244 change. So, a frontend should either wait for response from such
29245 problematic commands, or explicitly add @code{-thread-select} for
29246 all subsequent commands. No frontend is known to do this exactly
29247 right, so it is suggested to just always pass the @samp{--thread} and
29248 @samp{--frame} options.
29250 @subsubsection Language
29252 The execution of several commands depends on which language is selected.
29253 By default, the current language (@pxref{show language}) is used.
29254 But for commands known to be language-sensitive, it is recommended
29255 to use the @samp{--language} option. This option takes one argument,
29256 which is the name of the language to use while executing the command.
29260 -data-evaluate-expression --language c "sizeof (void*)"
29265 The valid language names are the same names accepted by the
29266 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29267 @samp{local} or @samp{unknown}.
29269 @node Asynchronous and non-stop modes
29270 @subsection Asynchronous command execution and non-stop mode
29272 On some targets, @value{GDBN} is capable of processing MI commands
29273 even while the target is running. This is called @dfn{asynchronous
29274 command execution} (@pxref{Background Execution}). The frontend may
29275 specify a preference for asynchronous execution using the
29276 @code{-gdb-set mi-async 1} command, which should be emitted before
29277 either running the executable or attaching to the target. After the
29278 frontend has started the executable or attached to the target, it can
29279 find if asynchronous execution is enabled using the
29280 @code{-list-target-features} command.
29283 @item -gdb-set mi-async on
29284 @item -gdb-set mi-async off
29285 Set whether MI is in asynchronous mode.
29287 When @code{off}, which is the default, MI execution commands (e.g.,
29288 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29289 for the program to stop before processing further commands.
29291 When @code{on}, MI execution commands are background execution
29292 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29293 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29294 MI commands even while the target is running.
29296 @item -gdb-show mi-async
29297 Show whether MI asynchronous mode is enabled.
29300 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29301 @code{target-async} instead of @code{mi-async}, and it had the effect
29302 of both putting MI in asynchronous mode and making CLI background
29303 commands possible. CLI background commands are now always possible
29304 ``out of the box'' if the target supports them. The old spelling is
29305 kept as a deprecated alias for backwards compatibility.
29307 Even if @value{GDBN} can accept a command while target is running,
29308 many commands that access the target do not work when the target is
29309 running. Therefore, asynchronous command execution is most useful
29310 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29311 it is possible to examine the state of one thread, while other threads
29314 When a given thread is running, MI commands that try to access the
29315 target in the context of that thread may not work, or may work only on
29316 some targets. In particular, commands that try to operate on thread's
29317 stack will not work, on any target. Commands that read memory, or
29318 modify breakpoints, may work or not work, depending on the target. Note
29319 that even commands that operate on global state, such as @code{print},
29320 @code{set}, and breakpoint commands, still access the target in the
29321 context of a specific thread, so frontend should try to find a
29322 stopped thread and perform the operation on that thread (using the
29323 @samp{--thread} option).
29325 Which commands will work in the context of a running thread is
29326 highly target dependent. However, the two commands
29327 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29328 to find the state of a thread, will always work.
29330 @node Thread groups
29331 @subsection Thread groups
29332 @value{GDBN} may be used to debug several processes at the same time.
29333 On some platforms, @value{GDBN} may support debugging of several
29334 hardware systems, each one having several cores with several different
29335 processes running on each core. This section describes the MI
29336 mechanism to support such debugging scenarios.
29338 The key observation is that regardless of the structure of the
29339 target, MI can have a global list of threads, because most commands that
29340 accept the @samp{--thread} option do not need to know what process that
29341 thread belongs to. Therefore, it is not necessary to introduce
29342 neither additional @samp{--process} option, nor an notion of the
29343 current process in the MI interface. The only strictly new feature
29344 that is required is the ability to find how the threads are grouped
29347 To allow the user to discover such grouping, and to support arbitrary
29348 hierarchy of machines/cores/processes, MI introduces the concept of a
29349 @dfn{thread group}. Thread group is a collection of threads and other
29350 thread groups. A thread group always has a string identifier, a type,
29351 and may have additional attributes specific to the type. A new
29352 command, @code{-list-thread-groups}, returns the list of top-level
29353 thread groups, which correspond to processes that @value{GDBN} is
29354 debugging at the moment. By passing an identifier of a thread group
29355 to the @code{-list-thread-groups} command, it is possible to obtain
29356 the members of specific thread group.
29358 To allow the user to easily discover processes, and other objects, he
29359 wishes to debug, a concept of @dfn{available thread group} is
29360 introduced. Available thread group is an thread group that
29361 @value{GDBN} is not debugging, but that can be attached to, using the
29362 @code{-target-attach} command. The list of available top-level thread
29363 groups can be obtained using @samp{-list-thread-groups --available}.
29364 In general, the content of a thread group may be only retrieved only
29365 after attaching to that thread group.
29367 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29368 Programs}). Each inferior corresponds to a thread group of a special
29369 type @samp{process}, and some additional operations are permitted on
29370 such thread groups.
29372 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29373 @node GDB/MI Command Syntax
29374 @section @sc{gdb/mi} Command Syntax
29377 * GDB/MI Input Syntax::
29378 * GDB/MI Output Syntax::
29381 @node GDB/MI Input Syntax
29382 @subsection @sc{gdb/mi} Input Syntax
29384 @cindex input syntax for @sc{gdb/mi}
29385 @cindex @sc{gdb/mi}, input syntax
29387 @item @var{command} @expansion{}
29388 @code{@var{cli-command} | @var{mi-command}}
29390 @item @var{cli-command} @expansion{}
29391 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29392 @var{cli-command} is any existing @value{GDBN} CLI command.
29394 @item @var{mi-command} @expansion{}
29395 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29396 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29398 @item @var{token} @expansion{}
29399 "any sequence of digits"
29401 @item @var{option} @expansion{}
29402 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29404 @item @var{parameter} @expansion{}
29405 @code{@var{non-blank-sequence} | @var{c-string}}
29407 @item @var{operation} @expansion{}
29408 @emph{any of the operations described in this chapter}
29410 @item @var{non-blank-sequence} @expansion{}
29411 @emph{anything, provided it doesn't contain special characters such as
29412 "-", @var{nl}, """ and of course " "}
29414 @item @var{c-string} @expansion{}
29415 @code{""" @var{seven-bit-iso-c-string-content} """}
29417 @item @var{nl} @expansion{}
29426 The CLI commands are still handled by the @sc{mi} interpreter; their
29427 output is described below.
29430 The @code{@var{token}}, when present, is passed back when the command
29434 Some @sc{mi} commands accept optional arguments as part of the parameter
29435 list. Each option is identified by a leading @samp{-} (dash) and may be
29436 followed by an optional argument parameter. Options occur first in the
29437 parameter list and can be delimited from normal parameters using
29438 @samp{--} (this is useful when some parameters begin with a dash).
29445 We want easy access to the existing CLI syntax (for debugging).
29448 We want it to be easy to spot a @sc{mi} operation.
29451 @node GDB/MI Output Syntax
29452 @subsection @sc{gdb/mi} Output Syntax
29454 @cindex output syntax of @sc{gdb/mi}
29455 @cindex @sc{gdb/mi}, output syntax
29456 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29457 followed, optionally, by a single result record. This result record
29458 is for the most recent command. The sequence of output records is
29459 terminated by @samp{(gdb)}.
29461 If an input command was prefixed with a @code{@var{token}} then the
29462 corresponding output for that command will also be prefixed by that same
29466 @item @var{output} @expansion{}
29467 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29469 @item @var{result-record} @expansion{}
29470 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29472 @item @var{out-of-band-record} @expansion{}
29473 @code{@var{async-record} | @var{stream-record}}
29475 @item @var{async-record} @expansion{}
29476 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29478 @item @var{exec-async-output} @expansion{}
29479 @code{[ @var{token} ] "*" @var{async-output nl}}
29481 @item @var{status-async-output} @expansion{}
29482 @code{[ @var{token} ] "+" @var{async-output nl}}
29484 @item @var{notify-async-output} @expansion{}
29485 @code{[ @var{token} ] "=" @var{async-output nl}}
29487 @item @var{async-output} @expansion{}
29488 @code{@var{async-class} ( "," @var{result} )*}
29490 @item @var{result-class} @expansion{}
29491 @code{"done" | "running" | "connected" | "error" | "exit"}
29493 @item @var{async-class} @expansion{}
29494 @code{"stopped" | @var{others}} (where @var{others} will be added
29495 depending on the needs---this is still in development).
29497 @item @var{result} @expansion{}
29498 @code{ @var{variable} "=" @var{value}}
29500 @item @var{variable} @expansion{}
29501 @code{ @var{string} }
29503 @item @var{value} @expansion{}
29504 @code{ @var{const} | @var{tuple} | @var{list} }
29506 @item @var{const} @expansion{}
29507 @code{@var{c-string}}
29509 @item @var{tuple} @expansion{}
29510 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29512 @item @var{list} @expansion{}
29513 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29514 @var{result} ( "," @var{result} )* "]" }
29516 @item @var{stream-record} @expansion{}
29517 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29519 @item @var{console-stream-output} @expansion{}
29520 @code{"~" @var{c-string nl}}
29522 @item @var{target-stream-output} @expansion{}
29523 @code{"@@" @var{c-string nl}}
29525 @item @var{log-stream-output} @expansion{}
29526 @code{"&" @var{c-string nl}}
29528 @item @var{nl} @expansion{}
29531 @item @var{token} @expansion{}
29532 @emph{any sequence of digits}.
29540 All output sequences end in a single line containing a period.
29543 The @code{@var{token}} is from the corresponding request. Note that
29544 for all async output, while the token is allowed by the grammar and
29545 may be output by future versions of @value{GDBN} for select async
29546 output messages, it is generally omitted. Frontends should treat
29547 all async output as reporting general changes in the state of the
29548 target and there should be no need to associate async output to any
29552 @cindex status output in @sc{gdb/mi}
29553 @var{status-async-output} contains on-going status information about the
29554 progress of a slow operation. It can be discarded. All status output is
29555 prefixed by @samp{+}.
29558 @cindex async output in @sc{gdb/mi}
29559 @var{exec-async-output} contains asynchronous state change on the target
29560 (stopped, started, disappeared). All async output is prefixed by
29564 @cindex notify output in @sc{gdb/mi}
29565 @var{notify-async-output} contains supplementary information that the
29566 client should handle (e.g., a new breakpoint information). All notify
29567 output is prefixed by @samp{=}.
29570 @cindex console output in @sc{gdb/mi}
29571 @var{console-stream-output} is output that should be displayed as is in the
29572 console. It is the textual response to a CLI command. All the console
29573 output is prefixed by @samp{~}.
29576 @cindex target output in @sc{gdb/mi}
29577 @var{target-stream-output} is the output produced by the target program.
29578 All the target output is prefixed by @samp{@@}.
29581 @cindex log output in @sc{gdb/mi}
29582 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29583 instance messages that should be displayed as part of an error log. All
29584 the log output is prefixed by @samp{&}.
29587 @cindex list output in @sc{gdb/mi}
29588 New @sc{gdb/mi} commands should only output @var{lists} containing
29594 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29595 details about the various output records.
29597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29598 @node GDB/MI Compatibility with CLI
29599 @section @sc{gdb/mi} Compatibility with CLI
29601 @cindex compatibility, @sc{gdb/mi} and CLI
29602 @cindex @sc{gdb/mi}, compatibility with CLI
29604 For the developers convenience CLI commands can be entered directly,
29605 but there may be some unexpected behaviour. For example, commands
29606 that query the user will behave as if the user replied yes, breakpoint
29607 command lists are not executed and some CLI commands, such as
29608 @code{if}, @code{when} and @code{define}, prompt for further input with
29609 @samp{>}, which is not valid MI output.
29611 This feature may be removed at some stage in the future and it is
29612 recommended that front ends use the @code{-interpreter-exec} command
29613 (@pxref{-interpreter-exec}).
29615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29616 @node GDB/MI Development and Front Ends
29617 @section @sc{gdb/mi} Development and Front Ends
29618 @cindex @sc{gdb/mi} development
29620 The application which takes the MI output and presents the state of the
29621 program being debugged to the user is called a @dfn{front end}.
29623 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29624 to the MI interface may break existing usage. This section describes how the
29625 protocol changes and how to request previous version of the protocol when it
29628 Some changes in MI need not break a carefully designed front end, and
29629 for these the MI version will remain unchanged. The following is a
29630 list of changes that may occur within one level, so front ends should
29631 parse MI output in a way that can handle them:
29635 New MI commands may be added.
29638 New fields may be added to the output of any MI command.
29641 The range of values for fields with specified values, e.g.,
29642 @code{in_scope} (@pxref{-var-update}) may be extended.
29644 @c The format of field's content e.g type prefix, may change so parse it
29645 @c at your own risk. Yes, in general?
29647 @c The order of fields may change? Shouldn't really matter but it might
29648 @c resolve inconsistencies.
29651 If the changes are likely to break front ends, the MI version level
29652 will be increased by one. The new versions of the MI protocol are not compatible
29653 with the old versions. Old versions of MI remain available, allowing front ends
29654 to keep using them until they are modified to use the latest MI version.
29656 Since @code{--interpreter=mi} always points to the latest MI version, it is
29657 recommended that front ends request a specific version of MI when launching
29658 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
29659 interpreter with the MI version they expect.
29661 The following table gives a summary of the released versions of the MI
29662 interface: the version number, the version of GDB in which it first appeared
29663 and the breaking changes compared to the previous version.
29665 @multitable @columnfractions .05 .05 .9
29666 @headitem MI version @tab GDB version @tab Breaking changes
29683 The @code{-environment-pwd}, @code{-environment-directory} and
29684 @code{-environment-path} commands now returns values using the MI output
29685 syntax, rather than CLI output syntax.
29688 @code{-var-list-children}'s @code{children} result field is now a list, rather
29692 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29704 The output of information about multi-location breakpoints has changed in the
29705 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29706 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29707 The multiple locations are now placed in a @code{locations} field, whose value
29713 If your front end cannot yet migrate to a more recent version of the
29714 MI protocol, you can nevertheless selectively enable specific features
29715 available in those recent MI versions, using the following commands:
29719 @item -fix-multi-location-breakpoint-output
29720 Use the output for multi-location breakpoints which was introduced by
29721 MI 3, even when using MI versions 2 or 1. This command has no
29722 effect when using MI version 3 or later.
29726 The best way to avoid unexpected changes in MI that might break your front
29727 end is to make your project known to @value{GDBN} developers and
29728 follow development on @email{gdb@@sourceware.org} and
29729 @email{gdb-patches@@sourceware.org}.
29730 @cindex mailing lists
29732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29733 @node GDB/MI Output Records
29734 @section @sc{gdb/mi} Output Records
29737 * GDB/MI Result Records::
29738 * GDB/MI Stream Records::
29739 * GDB/MI Async Records::
29740 * GDB/MI Breakpoint Information::
29741 * GDB/MI Frame Information::
29742 * GDB/MI Thread Information::
29743 * GDB/MI Ada Exception Information::
29746 @node GDB/MI Result Records
29747 @subsection @sc{gdb/mi} Result Records
29749 @cindex result records in @sc{gdb/mi}
29750 @cindex @sc{gdb/mi}, result records
29751 In addition to a number of out-of-band notifications, the response to a
29752 @sc{gdb/mi} command includes one of the following result indications:
29756 @item "^done" [ "," @var{results} ]
29757 The synchronous operation was successful, @code{@var{results}} are the return
29762 This result record is equivalent to @samp{^done}. Historically, it
29763 was output instead of @samp{^done} if the command has resumed the
29764 target. This behaviour is maintained for backward compatibility, but
29765 all frontends should treat @samp{^done} and @samp{^running}
29766 identically and rely on the @samp{*running} output record to determine
29767 which threads are resumed.
29771 @value{GDBN} has connected to a remote target.
29773 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29775 The operation failed. The @code{msg=@var{c-string}} variable contains
29776 the corresponding error message.
29778 If present, the @code{code=@var{c-string}} variable provides an error
29779 code on which consumers can rely on to detect the corresponding
29780 error condition. At present, only one error code is defined:
29783 @item "undefined-command"
29784 Indicates that the command causing the error does not exist.
29789 @value{GDBN} has terminated.
29793 @node GDB/MI Stream Records
29794 @subsection @sc{gdb/mi} Stream Records
29796 @cindex @sc{gdb/mi}, stream records
29797 @cindex stream records in @sc{gdb/mi}
29798 @value{GDBN} internally maintains a number of output streams: the console, the
29799 target, and the log. The output intended for each of these streams is
29800 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29802 Each stream record begins with a unique @dfn{prefix character} which
29803 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29804 Syntax}). In addition to the prefix, each stream record contains a
29805 @code{@var{string-output}}. This is either raw text (with an implicit new
29806 line) or a quoted C string (which does not contain an implicit newline).
29809 @item "~" @var{string-output}
29810 The console output stream contains text that should be displayed in the
29811 CLI console window. It contains the textual responses to CLI commands.
29813 @item "@@" @var{string-output}
29814 The target output stream contains any textual output from the running
29815 target. This is only present when GDB's event loop is truly
29816 asynchronous, which is currently only the case for remote targets.
29818 @item "&" @var{string-output}
29819 The log stream contains debugging messages being produced by @value{GDBN}'s
29823 @node GDB/MI Async Records
29824 @subsection @sc{gdb/mi} Async Records
29826 @cindex async records in @sc{gdb/mi}
29827 @cindex @sc{gdb/mi}, async records
29828 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29829 additional changes that have occurred. Those changes can either be a
29830 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29831 target activity (e.g., target stopped).
29833 The following is the list of possible async records:
29837 @item *running,thread-id="@var{thread}"
29838 The target is now running. The @var{thread} field can be the global
29839 thread ID of the thread that is now running, and it can be
29840 @samp{all} if all threads are running. The frontend should assume
29841 that no interaction with a running thread is possible after this
29842 notification is produced. The frontend should not assume that this
29843 notification is output only once for any command. @value{GDBN} may
29844 emit this notification several times, either for different threads,
29845 because it cannot resume all threads together, or even for a single
29846 thread, if the thread must be stepped though some code before letting
29849 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29850 The target has stopped. The @var{reason} field can have one of the
29854 @item breakpoint-hit
29855 A breakpoint was reached.
29856 @item watchpoint-trigger
29857 A watchpoint was triggered.
29858 @item read-watchpoint-trigger
29859 A read watchpoint was triggered.
29860 @item access-watchpoint-trigger
29861 An access watchpoint was triggered.
29862 @item function-finished
29863 An -exec-finish or similar CLI command was accomplished.
29864 @item location-reached
29865 An -exec-until or similar CLI command was accomplished.
29866 @item watchpoint-scope
29867 A watchpoint has gone out of scope.
29868 @item end-stepping-range
29869 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29870 similar CLI command was accomplished.
29871 @item exited-signalled
29872 The inferior exited because of a signal.
29874 The inferior exited.
29875 @item exited-normally
29876 The inferior exited normally.
29877 @item signal-received
29878 A signal was received by the inferior.
29880 The inferior has stopped due to a library being loaded or unloaded.
29881 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29882 set or when a @code{catch load} or @code{catch unload} catchpoint is
29883 in use (@pxref{Set Catchpoints}).
29885 The inferior has forked. This is reported when @code{catch fork}
29886 (@pxref{Set Catchpoints}) has been used.
29888 The inferior has vforked. This is reported in when @code{catch vfork}
29889 (@pxref{Set Catchpoints}) has been used.
29890 @item syscall-entry
29891 The inferior entered a system call. This is reported when @code{catch
29892 syscall} (@pxref{Set Catchpoints}) has been used.
29893 @item syscall-return
29894 The inferior returned from a system call. This is reported when
29895 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29897 The inferior called @code{exec}. This is reported when @code{catch exec}
29898 (@pxref{Set Catchpoints}) has been used.
29901 The @var{id} field identifies the global thread ID of the thread
29902 that directly caused the stop -- for example by hitting a breakpoint.
29903 Depending on whether all-stop
29904 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29905 stop all threads, or only the thread that directly triggered the stop.
29906 If all threads are stopped, the @var{stopped} field will have the
29907 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29908 field will be a list of thread identifiers. Presently, this list will
29909 always include a single thread, but frontend should be prepared to see
29910 several threads in the list. The @var{core} field reports the
29911 processor core on which the stop event has happened. This field may be absent
29912 if such information is not available.
29914 @item =thread-group-added,id="@var{id}"
29915 @itemx =thread-group-removed,id="@var{id}"
29916 A thread group was either added or removed. The @var{id} field
29917 contains the @value{GDBN} identifier of the thread group. When a thread
29918 group is added, it generally might not be associated with a running
29919 process. When a thread group is removed, its id becomes invalid and
29920 cannot be used in any way.
29922 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29923 A thread group became associated with a running program,
29924 either because the program was just started or the thread group
29925 was attached to a program. The @var{id} field contains the
29926 @value{GDBN} identifier of the thread group. The @var{pid} field
29927 contains process identifier, specific to the operating system.
29929 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29930 A thread group is no longer associated with a running program,
29931 either because the program has exited, or because it was detached
29932 from. The @var{id} field contains the @value{GDBN} identifier of the
29933 thread group. The @var{code} field is the exit code of the inferior; it exists
29934 only when the inferior exited with some code.
29936 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29937 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29938 A thread either was created, or has exited. The @var{id} field
29939 contains the global @value{GDBN} identifier of the thread. The @var{gid}
29940 field identifies the thread group this thread belongs to.
29942 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
29943 Informs that the selected thread or frame were changed. This notification
29944 is not emitted as result of the @code{-thread-select} or
29945 @code{-stack-select-frame} commands, but is emitted whenever an MI command
29946 that is not documented to change the selected thread and frame actually
29947 changes them. In particular, invoking, directly or indirectly
29948 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
29949 will generate this notification. Changing the thread or frame from another
29950 user interface (see @ref{Interpreters}) will also generate this notification.
29952 The @var{frame} field is only present if the newly selected thread is
29953 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
29955 We suggest that in response to this notification, front ends
29956 highlight the selected thread and cause subsequent commands to apply to
29959 @item =library-loaded,...
29960 Reports that a new library file was loaded by the program. This
29961 notification has 5 fields---@var{id}, @var{target-name},
29962 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
29963 opaque identifier of the library. For remote debugging case,
29964 @var{target-name} and @var{host-name} fields give the name of the
29965 library file on the target, and on the host respectively. For native
29966 debugging, both those fields have the same value. The
29967 @var{symbols-loaded} field is emitted only for backward compatibility
29968 and should not be relied on to convey any useful information. The
29969 @var{thread-group} field, if present, specifies the id of the thread
29970 group in whose context the library was loaded. If the field is
29971 absent, it means the library was loaded in the context of all present
29972 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
29975 @item =library-unloaded,...
29976 Reports that a library was unloaded by the program. This notification
29977 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29978 the same meaning as for the @code{=library-loaded} notification.
29979 The @var{thread-group} field, if present, specifies the id of the
29980 thread group in whose context the library was unloaded. If the field is
29981 absent, it means the library was unloaded in the context of all present
29984 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29985 @itemx =traceframe-changed,end
29986 Reports that the trace frame was changed and its new number is
29987 @var{tfnum}. The number of the tracepoint associated with this trace
29988 frame is @var{tpnum}.
29990 @item =tsv-created,name=@var{name},initial=@var{initial}
29991 Reports that the new trace state variable @var{name} is created with
29992 initial value @var{initial}.
29994 @item =tsv-deleted,name=@var{name}
29995 @itemx =tsv-deleted
29996 Reports that the trace state variable @var{name} is deleted or all
29997 trace state variables are deleted.
29999 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30000 Reports that the trace state variable @var{name} is modified with
30001 the initial value @var{initial}. The current value @var{current} of
30002 trace state variable is optional and is reported if the current
30003 value of trace state variable is known.
30005 @item =breakpoint-created,bkpt=@{...@}
30006 @itemx =breakpoint-modified,bkpt=@{...@}
30007 @itemx =breakpoint-deleted,id=@var{number}
30008 Reports that a breakpoint was created, modified, or deleted,
30009 respectively. Only user-visible breakpoints are reported to the MI
30012 The @var{bkpt} argument is of the same form as returned by the various
30013 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30014 @var{number} is the ordinal number of the breakpoint.
30016 Note that if a breakpoint is emitted in the result record of a
30017 command, then it will not also be emitted in an async record.
30019 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30020 @itemx =record-stopped,thread-group="@var{id}"
30021 Execution log recording was either started or stopped on an
30022 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30023 group corresponding to the affected inferior.
30025 The @var{method} field indicates the method used to record execution. If the
30026 method in use supports multiple recording formats, @var{format} will be present
30027 and contain the currently used format. @xref{Process Record and Replay},
30028 for existing method and format values.
30030 @item =cmd-param-changed,param=@var{param},value=@var{value}
30031 Reports that a parameter of the command @code{set @var{param}} is
30032 changed to @var{value}. In the multi-word @code{set} command,
30033 the @var{param} is the whole parameter list to @code{set} command.
30034 For example, In command @code{set check type on}, @var{param}
30035 is @code{check type} and @var{value} is @code{on}.
30037 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30038 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30039 written in an inferior. The @var{id} is the identifier of the
30040 thread group corresponding to the affected inferior. The optional
30041 @code{type="code"} part is reported if the memory written to holds
30045 @node GDB/MI Breakpoint Information
30046 @subsection @sc{gdb/mi} Breakpoint Information
30048 When @value{GDBN} reports information about a breakpoint, a
30049 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30054 The breakpoint number.
30057 The type of the breakpoint. For ordinary breakpoints this will be
30058 @samp{breakpoint}, but many values are possible.
30061 If the type of the breakpoint is @samp{catchpoint}, then this
30062 indicates the exact type of catchpoint.
30065 This is the breakpoint disposition---either @samp{del}, meaning that
30066 the breakpoint will be deleted at the next stop, or @samp{keep},
30067 meaning that the breakpoint will not be deleted.
30070 This indicates whether the breakpoint is enabled, in which case the
30071 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30072 Note that this is not the same as the field @code{enable}.
30075 The address of the breakpoint. This may be a hexidecimal number,
30076 giving the address; or the string @samp{<PENDING>}, for a pending
30077 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30078 multiple locations. This field will not be present if no address can
30079 be determined. For example, a watchpoint does not have an address.
30082 Optional field containing any flags related to the address. These flags are
30083 architecture-dependent; see @ref{Architectures} for their meaning for a
30087 If known, the function in which the breakpoint appears.
30088 If not known, this field is not present.
30091 The name of the source file which contains this function, if known.
30092 If not known, this field is not present.
30095 The full file name of the source file which contains this function, if
30096 known. If not known, this field is not present.
30099 The line number at which this breakpoint appears, if known.
30100 If not known, this field is not present.
30103 If the source file is not known, this field may be provided. If
30104 provided, this holds the address of the breakpoint, possibly followed
30108 If this breakpoint is pending, this field is present and holds the
30109 text used to set the breakpoint, as entered by the user.
30112 Where this breakpoint's condition is evaluated, either @samp{host} or
30116 If this is a thread-specific breakpoint, then this identifies the
30117 thread in which the breakpoint can trigger.
30120 If this breakpoint is restricted to a particular Ada task, then this
30121 field will hold the task identifier.
30124 If the breakpoint is conditional, this is the condition expression.
30127 The ignore count of the breakpoint.
30130 The enable count of the breakpoint.
30132 @item traceframe-usage
30135 @item static-tracepoint-marker-string-id
30136 For a static tracepoint, the name of the static tracepoint marker.
30139 For a masked watchpoint, this is the mask.
30142 A tracepoint's pass count.
30144 @item original-location
30145 The location of the breakpoint as originally specified by the user.
30146 This field is optional.
30149 The number of times the breakpoint has been hit.
30152 This field is only given for tracepoints. This is either @samp{y},
30153 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30157 Some extra data, the exact contents of which are type-dependent.
30160 This field is present if the breakpoint has multiple locations. It is also
30161 exceptionally present if the breakpoint is enabled and has a single, disabled
30164 The value is a list of locations. The format of a location is described below.
30168 A location in a multi-location breakpoint is represented as a tuple with the
30174 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30175 number of the parent breakpoint. The second digit is the number of the
30176 location within that breakpoint.
30179 There are three possible values, with the following meanings:
30182 The location is enabled.
30184 The location is disabled by the user.
30186 The location is disabled because the breakpoint condition is invalid
30191 The address of this location as an hexidecimal number.
30194 Optional field containing any flags related to the address. These flags are
30195 architecture-dependent; see @ref{Architectures} for their meaning for a
30199 If known, the function in which the location appears.
30200 If not known, this field is not present.
30203 The name of the source file which contains this location, if known.
30204 If not known, this field is not present.
30207 The full file name of the source file which contains this location, if
30208 known. If not known, this field is not present.
30211 The line number at which this location appears, if known.
30212 If not known, this field is not present.
30214 @item thread-groups
30215 The thread groups this location is in.
30219 For example, here is what the output of @code{-break-insert}
30220 (@pxref{GDB/MI Breakpoint Commands}) might be:
30223 -> -break-insert main
30224 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30225 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30226 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30231 @node GDB/MI Frame Information
30232 @subsection @sc{gdb/mi} Frame Information
30234 Response from many MI commands includes an information about stack
30235 frame. This information is a tuple that may have the following
30240 The level of the stack frame. The innermost frame has the level of
30241 zero. This field is always present.
30244 The name of the function corresponding to the frame. This field may
30245 be absent if @value{GDBN} is unable to determine the function name.
30248 The code address for the frame. This field is always present.
30251 Optional field containing any flags related to the address. These flags are
30252 architecture-dependent; see @ref{Architectures} for their meaning for a
30256 The name of the source files that correspond to the frame's code
30257 address. This field may be absent.
30260 The source line corresponding to the frames' code address. This field
30264 The name of the binary file (either executable or shared library) the
30265 corresponds to the frame's code address. This field may be absent.
30269 @node GDB/MI Thread Information
30270 @subsection @sc{gdb/mi} Thread Information
30272 Whenever @value{GDBN} has to report an information about a thread, it
30273 uses a tuple with the following fields. The fields are always present unless
30278 The global numeric id assigned to the thread by @value{GDBN}.
30281 The target-specific string identifying the thread.
30284 Additional information about the thread provided by the target.
30285 It is supposed to be human-readable and not interpreted by the
30286 frontend. This field is optional.
30289 The name of the thread. If the user specified a name using the
30290 @code{thread name} command, then this name is given. Otherwise, if
30291 @value{GDBN} can extract the thread name from the target, then that
30292 name is given. If @value{GDBN} cannot find the thread name, then this
30296 The execution state of the thread, either @samp{stopped} or @samp{running},
30297 depending on whether the thread is presently running.
30300 The stack frame currently executing in the thread. This field is only present
30301 if the thread is stopped. Its format is documented in
30302 @ref{GDB/MI Frame Information}.
30305 The value of this field is an integer number of the processor core the
30306 thread was last seen on. This field is optional.
30309 @node GDB/MI Ada Exception Information
30310 @subsection @sc{gdb/mi} Ada Exception Information
30312 Whenever a @code{*stopped} record is emitted because the program
30313 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30314 @value{GDBN} provides the name of the exception that was raised via
30315 the @code{exception-name} field. Also, for exceptions that were raised
30316 with an exception message, @value{GDBN} provides that message via
30317 the @code{exception-message} field.
30319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30320 @node GDB/MI Simple Examples
30321 @section Simple Examples of @sc{gdb/mi} Interaction
30322 @cindex @sc{gdb/mi}, simple examples
30324 This subsection presents several simple examples of interaction using
30325 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30326 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30327 the output received from @sc{gdb/mi}.
30329 Note the line breaks shown in the examples are here only for
30330 readability, they don't appear in the real output.
30332 @subheading Setting a Breakpoint
30334 Setting a breakpoint generates synchronous output which contains detailed
30335 information of the breakpoint.
30338 -> -break-insert main
30339 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30340 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30341 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30346 @subheading Program Execution
30348 Program execution generates asynchronous records and MI gives the
30349 reason that execution stopped.
30355 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30356 frame=@{addr="0x08048564",func="main",
30357 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30358 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30359 arch="i386:x86_64"@}
30364 <- *stopped,reason="exited-normally"
30368 @subheading Quitting @value{GDBN}
30370 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30378 Please note that @samp{^exit} is printed immediately, but it might
30379 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30380 performs necessary cleanups, including killing programs being debugged
30381 or disconnecting from debug hardware, so the frontend should wait till
30382 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30383 fails to exit in reasonable time.
30385 @subheading A Bad Command
30387 Here's what happens if you pass a non-existent command:
30391 <- ^error,msg="Undefined MI command: rubbish"
30396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30397 @node GDB/MI Command Description Format
30398 @section @sc{gdb/mi} Command Description Format
30400 The remaining sections describe blocks of commands. Each block of
30401 commands is laid out in a fashion similar to this section.
30403 @subheading Motivation
30405 The motivation for this collection of commands.
30407 @subheading Introduction
30409 A brief introduction to this collection of commands as a whole.
30411 @subheading Commands
30413 For each command in the block, the following is described:
30415 @subsubheading Synopsis
30418 -command @var{args}@dots{}
30421 @subsubheading Result
30423 @subsubheading @value{GDBN} Command
30425 The corresponding @value{GDBN} CLI command(s), if any.
30427 @subsubheading Example
30429 Example(s) formatted for readability. Some of the described commands have
30430 not been implemented yet and these are labeled N.A.@: (not available).
30433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30434 @node GDB/MI Breakpoint Commands
30435 @section @sc{gdb/mi} Breakpoint Commands
30437 @cindex breakpoint commands for @sc{gdb/mi}
30438 @cindex @sc{gdb/mi}, breakpoint commands
30439 This section documents @sc{gdb/mi} commands for manipulating
30442 @subheading The @code{-break-after} Command
30443 @findex -break-after
30445 @subsubheading Synopsis
30448 -break-after @var{number} @var{count}
30451 The breakpoint number @var{number} is not in effect until it has been
30452 hit @var{count} times. To see how this is reflected in the output of
30453 the @samp{-break-list} command, see the description of the
30454 @samp{-break-list} command below.
30456 @subsubheading @value{GDBN} Command
30458 The corresponding @value{GDBN} command is @samp{ignore}.
30460 @subsubheading Example
30465 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30466 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30467 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30475 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30476 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30477 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30478 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30479 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30480 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30481 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30482 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30483 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30484 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30489 @subheading The @code{-break-catch} Command
30490 @findex -break-catch
30493 @subheading The @code{-break-commands} Command
30494 @findex -break-commands
30496 @subsubheading Synopsis
30499 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30502 Specifies the CLI commands that should be executed when breakpoint
30503 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30504 are the commands. If no command is specified, any previously-set
30505 commands are cleared. @xref{Break Commands}. Typical use of this
30506 functionality is tracing a program, that is, printing of values of
30507 some variables whenever breakpoint is hit and then continuing.
30509 @subsubheading @value{GDBN} Command
30511 The corresponding @value{GDBN} command is @samp{commands}.
30513 @subsubheading Example
30518 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30519 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30520 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30523 -break-commands 1 "print v" "continue"
30528 @subheading The @code{-break-condition} Command
30529 @findex -break-condition
30531 @subsubheading Synopsis
30534 -break-condition [ --force ] @var{number} @var{expr}
30537 Breakpoint @var{number} will stop the program only if the condition in
30538 @var{expr} is true. The condition becomes part of the
30539 @samp{-break-list} output (see the description of the @samp{-break-list}
30540 command below). If the @samp{--force} flag is passed, the condition
30541 is forcibly defined even when it is invalid for all locations of
30542 breakpoint @var{number}.
30544 @subsubheading @value{GDBN} Command
30546 The corresponding @value{GDBN} command is @samp{condition}.
30548 @subsubheading Example
30552 -break-condition 1 1
30556 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30557 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30558 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30559 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30560 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30561 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30562 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30563 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30564 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30565 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30569 @subheading The @code{-break-delete} Command
30570 @findex -break-delete
30572 @subsubheading Synopsis
30575 -break-delete ( @var{breakpoint} )+
30578 Delete the breakpoint(s) whose number(s) are specified in the argument
30579 list. This is obviously reflected in the breakpoint list.
30581 @subsubheading @value{GDBN} Command
30583 The corresponding @value{GDBN} command is @samp{delete}.
30585 @subsubheading Example
30593 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30594 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30595 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30596 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30597 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30598 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30599 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30604 @subheading The @code{-break-disable} Command
30605 @findex -break-disable
30607 @subsubheading Synopsis
30610 -break-disable ( @var{breakpoint} )+
30613 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30614 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30616 @subsubheading @value{GDBN} Command
30618 The corresponding @value{GDBN} command is @samp{disable}.
30620 @subsubheading Example
30628 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30629 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30630 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30631 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30632 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30633 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30634 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30635 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30636 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30637 line="5",thread-groups=["i1"],times="0"@}]@}
30641 @subheading The @code{-break-enable} Command
30642 @findex -break-enable
30644 @subsubheading Synopsis
30647 -break-enable ( @var{breakpoint} )+
30650 Enable (previously disabled) @var{breakpoint}(s).
30652 @subsubheading @value{GDBN} Command
30654 The corresponding @value{GDBN} command is @samp{enable}.
30656 @subsubheading Example
30664 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30665 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30666 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30667 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30668 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30669 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30670 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30671 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30672 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30673 line="5",thread-groups=["i1"],times="0"@}]@}
30677 @subheading The @code{-break-info} Command
30678 @findex -break-info
30680 @subsubheading Synopsis
30683 -break-info @var{breakpoint}
30687 Get information about a single breakpoint.
30689 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30690 Information}, for details on the format of each breakpoint in the
30693 @subsubheading @value{GDBN} Command
30695 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30697 @subsubheading Example
30700 @subheading The @code{-break-insert} Command
30701 @findex -break-insert
30702 @anchor{-break-insert}
30704 @subsubheading Synopsis
30707 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
30708 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
30709 [ -p @var{thread-id} ] [ @var{location} ]
30713 If specified, @var{location}, can be one of:
30716 @item linespec location
30717 A linespec location. @xref{Linespec Locations}.
30719 @item explicit location
30720 An explicit location. @sc{gdb/mi} explicit locations are
30721 analogous to the CLI's explicit locations using the option names
30722 listed below. @xref{Explicit Locations}.
30725 @item --source @var{filename}
30726 The source file name of the location. This option requires the use
30727 of either @samp{--function} or @samp{--line}.
30729 @item --function @var{function}
30730 The name of a function or method.
30732 @item --label @var{label}
30733 The name of a label.
30735 @item --line @var{lineoffset}
30736 An absolute or relative line offset from the start of the location.
30739 @item address location
30740 An address location, *@var{address}. @xref{Address Locations}.
30744 The possible optional parameters of this command are:
30748 Insert a temporary breakpoint.
30750 Insert a hardware breakpoint.
30752 If @var{location} cannot be parsed (for example if it
30753 refers to unknown files or functions), create a pending
30754 breakpoint. Without this flag, @value{GDBN} will report
30755 an error, and won't create a breakpoint, if @var{location}
30758 Create a disabled breakpoint.
30760 Create a tracepoint. @xref{Tracepoints}. When this parameter
30761 is used together with @samp{-h}, a fast tracepoint is created.
30762 @item -c @var{condition}
30763 Make the breakpoint conditional on @var{condition}.
30764 @item --force-condition
30765 Forcibly define the breakpoint even if the condition is invalid at
30766 all of the breakpoint locations.
30767 @item -i @var{ignore-count}
30768 Initialize the @var{ignore-count}.
30769 @item -p @var{thread-id}
30770 Restrict the breakpoint to the thread with the specified global
30773 This option makes @value{GDBN} interpret a function name specified as
30774 a complete fully-qualified name.
30777 @subsubheading Result
30779 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30780 resulting breakpoint.
30782 Note: this format is open to change.
30783 @c An out-of-band breakpoint instead of part of the result?
30785 @subsubheading @value{GDBN} Command
30787 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30788 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30790 @subsubheading Example
30795 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30796 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30799 -break-insert -t foo
30800 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30801 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30805 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30806 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30807 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30808 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30809 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30810 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30811 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30812 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30813 addr="0x0001072c", func="main",file="recursive2.c",
30814 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30816 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30817 addr="0x00010774",func="foo",file="recursive2.c",
30818 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30821 @c -break-insert -r foo.*
30822 @c ~int foo(int, int);
30823 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30824 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30829 @subheading The @code{-dprintf-insert} Command
30830 @findex -dprintf-insert
30832 @subsubheading Synopsis
30835 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
30836 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
30837 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30842 If supplied, @var{location} and @code{--qualified} may be specified
30843 the same way as for the @code{-break-insert} command.
30844 @xref{-break-insert}.
30846 The possible optional parameters of this command are:
30850 Insert a temporary breakpoint.
30852 If @var{location} cannot be parsed (for example, if it
30853 refers to unknown files or functions), create a pending
30854 breakpoint. Without this flag, @value{GDBN} will report
30855 an error, and won't create a breakpoint, if @var{location}
30858 Create a disabled breakpoint.
30859 @item -c @var{condition}
30860 Make the breakpoint conditional on @var{condition}.
30861 @item --force-condition
30862 Forcibly define the breakpoint even if the condition is invalid at
30863 all of the breakpoint locations.
30864 @item -i @var{ignore-count}
30865 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30866 to @var{ignore-count}.
30867 @item -p @var{thread-id}
30868 Restrict the breakpoint to the thread with the specified global
30872 @subsubheading Result
30874 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30875 resulting breakpoint.
30877 @c An out-of-band breakpoint instead of part of the result?
30879 @subsubheading @value{GDBN} Command
30881 The corresponding @value{GDBN} command is @samp{dprintf}.
30883 @subsubheading Example
30887 4-dprintf-insert foo "At foo entry\n"
30888 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30889 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30890 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30891 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30892 original-location="foo"@}
30894 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30895 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30896 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30897 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30898 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30899 original-location="mi-dprintf.c:26"@}
30903 @subheading The @code{-break-list} Command
30904 @findex -break-list
30906 @subsubheading Synopsis
30912 Displays the list of inserted breakpoints, showing the following fields:
30916 number of the breakpoint
30918 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30920 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30923 is the breakpoint enabled or no: @samp{y} or @samp{n}
30925 memory location at which the breakpoint is set
30927 logical location of the breakpoint, expressed by function name, file
30929 @item Thread-groups
30930 list of thread groups to which this breakpoint applies
30932 number of times the breakpoint has been hit
30935 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30936 @code{body} field is an empty list.
30938 @subsubheading @value{GDBN} Command
30940 The corresponding @value{GDBN} command is @samp{info break}.
30942 @subsubheading Example
30947 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30948 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30949 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30950 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30951 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30952 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30953 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30954 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30955 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30957 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30958 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30959 line="13",thread-groups=["i1"],times="0"@}]@}
30963 Here's an example of the result when there are no breakpoints:
30968 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30969 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30970 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30971 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30972 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30973 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30974 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30979 @subheading The @code{-break-passcount} Command
30980 @findex -break-passcount
30982 @subsubheading Synopsis
30985 -break-passcount @var{tracepoint-number} @var{passcount}
30988 Set the passcount for tracepoint @var{tracepoint-number} to
30989 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30990 is not a tracepoint, error is emitted. This corresponds to CLI
30991 command @samp{passcount}.
30993 @subheading The @code{-break-watch} Command
30994 @findex -break-watch
30996 @subsubheading Synopsis
30999 -break-watch [ -a | -r ]
31002 Create a watchpoint. With the @samp{-a} option it will create an
31003 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31004 read from or on a write to the memory location. With the @samp{-r}
31005 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31006 trigger only when the memory location is accessed for reading. Without
31007 either of the options, the watchpoint created is a regular watchpoint,
31008 i.e., it will trigger when the memory location is accessed for writing.
31009 @xref{Set Watchpoints, , Setting Watchpoints}.
31011 Note that @samp{-break-list} will report a single list of watchpoints and
31012 breakpoints inserted.
31014 @subsubheading @value{GDBN} Command
31016 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31019 @subsubheading Example
31021 Setting a watchpoint on a variable in the @code{main} function:
31026 ^done,wpt=@{number="2",exp="x"@}
31031 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31032 value=@{old="-268439212",new="55"@},
31033 frame=@{func="main",args=[],file="recursive2.c",
31034 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31038 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31039 the program execution twice: first for the variable changing value, then
31040 for the watchpoint going out of scope.
31045 ^done,wpt=@{number="5",exp="C"@}
31050 *stopped,reason="watchpoint-trigger",
31051 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31052 frame=@{func="callee4",args=[],
31053 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31054 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31055 arch="i386:x86_64"@}
31060 *stopped,reason="watchpoint-scope",wpnum="5",
31061 frame=@{func="callee3",args=[@{name="strarg",
31062 value="0x11940 \"A string argument.\""@}],
31063 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31064 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31065 arch="i386:x86_64"@}
31069 Listing breakpoints and watchpoints, at different points in the program
31070 execution. Note that once the watchpoint goes out of scope, it is
31076 ^done,wpt=@{number="2",exp="C"@}
31079 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31080 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31081 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31082 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31083 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31084 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31085 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31086 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31087 addr="0x00010734",func="callee4",
31088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31089 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31091 bkpt=@{number="2",type="watchpoint",disp="keep",
31092 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31097 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31098 value=@{old="-276895068",new="3"@},
31099 frame=@{func="callee4",args=[],
31100 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31101 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31102 arch="i386:x86_64"@}
31105 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31112 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31113 addr="0x00010734",func="callee4",
31114 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31115 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31117 bkpt=@{number="2",type="watchpoint",disp="keep",
31118 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31122 ^done,reason="watchpoint-scope",wpnum="2",
31123 frame=@{func="callee3",args=[@{name="strarg",
31124 value="0x11940 \"A string argument.\""@}],
31125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31127 arch="i386:x86_64"@}
31130 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31137 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31138 addr="0x00010734",func="callee4",
31139 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31140 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31141 thread-groups=["i1"],times="1"@}]@}
31146 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31147 @node GDB/MI Catchpoint Commands
31148 @section @sc{gdb/mi} Catchpoint Commands
31150 This section documents @sc{gdb/mi} commands for manipulating
31154 * Shared Library GDB/MI Catchpoint Commands::
31155 * Ada Exception GDB/MI Catchpoint Commands::
31156 * C++ Exception GDB/MI Catchpoint Commands::
31159 @node Shared Library GDB/MI Catchpoint Commands
31160 @subsection Shared Library @sc{gdb/mi} Catchpoints
31162 @subheading The @code{-catch-load} Command
31163 @findex -catch-load
31165 @subsubheading Synopsis
31168 -catch-load [ -t ] [ -d ] @var{regexp}
31171 Add a catchpoint for library load events. If the @samp{-t} option is used,
31172 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31173 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31174 in a disabled state. The @samp{regexp} argument is a regular
31175 expression used to match the name of the loaded library.
31178 @subsubheading @value{GDBN} Command
31180 The corresponding @value{GDBN} command is @samp{catch load}.
31182 @subsubheading Example
31185 -catch-load -t foo.so
31186 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31187 what="load of library matching foo.so",catch-type="load",times="0"@}
31192 @subheading The @code{-catch-unload} Command
31193 @findex -catch-unload
31195 @subsubheading Synopsis
31198 -catch-unload [ -t ] [ -d ] @var{regexp}
31201 Add a catchpoint for library unload events. If the @samp{-t} option is
31202 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31203 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31204 created in a disabled state. The @samp{regexp} argument is a regular
31205 expression used to match the name of the unloaded library.
31207 @subsubheading @value{GDBN} Command
31209 The corresponding @value{GDBN} command is @samp{catch unload}.
31211 @subsubheading Example
31214 -catch-unload -d bar.so
31215 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31216 what="load of library matching bar.so",catch-type="unload",times="0"@}
31220 @node Ada Exception GDB/MI Catchpoint Commands
31221 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31223 The following @sc{gdb/mi} commands can be used to create catchpoints
31224 that stop the execution when Ada exceptions are being raised.
31226 @subheading The @code{-catch-assert} Command
31227 @findex -catch-assert
31229 @subsubheading Synopsis
31232 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31235 Add a catchpoint for failed Ada assertions.
31237 The possible optional parameters for this command are:
31240 @item -c @var{condition}
31241 Make the catchpoint conditional on @var{condition}.
31243 Create a disabled catchpoint.
31245 Create a temporary catchpoint.
31248 @subsubheading @value{GDBN} Command
31250 The corresponding @value{GDBN} command is @samp{catch assert}.
31252 @subsubheading Example
31256 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31257 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31258 thread-groups=["i1"],times="0",
31259 original-location="__gnat_debug_raise_assert_failure"@}
31263 @subheading The @code{-catch-exception} Command
31264 @findex -catch-exception
31266 @subsubheading Synopsis
31269 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31273 Add a catchpoint stopping when Ada exceptions are raised.
31274 By default, the command stops the program when any Ada exception
31275 gets raised. But it is also possible, by using some of the
31276 optional parameters described below, to create more selective
31279 The possible optional parameters for this command are:
31282 @item -c @var{condition}
31283 Make the catchpoint conditional on @var{condition}.
31285 Create a disabled catchpoint.
31286 @item -e @var{exception-name}
31287 Only stop when @var{exception-name} is raised. This option cannot
31288 be used combined with @samp{-u}.
31290 Create a temporary catchpoint.
31292 Stop only when an unhandled exception gets raised. This option
31293 cannot be used combined with @samp{-e}.
31296 @subsubheading @value{GDBN} Command
31298 The corresponding @value{GDBN} commands are @samp{catch exception}
31299 and @samp{catch exception unhandled}.
31301 @subsubheading Example
31304 -catch-exception -e Program_Error
31305 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31306 enabled="y",addr="0x0000000000404874",
31307 what="`Program_Error' Ada exception", thread-groups=["i1"],
31308 times="0",original-location="__gnat_debug_raise_exception"@}
31312 @subheading The @code{-catch-handlers} Command
31313 @findex -catch-handlers
31315 @subsubheading Synopsis
31318 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31322 Add a catchpoint stopping when Ada exceptions are handled.
31323 By default, the command stops the program when any Ada exception
31324 gets handled. But it is also possible, by using some of the
31325 optional parameters described below, to create more selective
31328 The possible optional parameters for this command are:
31331 @item -c @var{condition}
31332 Make the catchpoint conditional on @var{condition}.
31334 Create a disabled catchpoint.
31335 @item -e @var{exception-name}
31336 Only stop when @var{exception-name} is handled.
31338 Create a temporary catchpoint.
31341 @subsubheading @value{GDBN} Command
31343 The corresponding @value{GDBN} command is @samp{catch handlers}.
31345 @subsubheading Example
31348 -catch-handlers -e Constraint_Error
31349 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31350 enabled="y",addr="0x0000000000402f68",
31351 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31352 times="0",original-location="__gnat_begin_handler"@}
31356 @node C++ Exception GDB/MI Catchpoint Commands
31357 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31359 The following @sc{gdb/mi} commands can be used to create catchpoints
31360 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31363 @subheading The @code{-catch-throw} Command
31364 @findex -catch-throw
31366 @subsubheading Synopsis
31369 -catch-throw [ -t ] [ -r @var{regexp}]
31372 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31373 given, then only exceptions whose type matches the regular expression
31376 If @samp{-t} is given, then the catchpoint is enabled only for one
31377 stop, the catchpoint is automatically deleted after stopping once for
31380 @subsubheading @value{GDBN} Command
31382 The corresponding @value{GDBN} commands are @samp{catch throw}
31383 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31385 @subsubheading Example
31388 -catch-throw -r exception_type
31389 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31390 what="exception throw",catch-type="throw",
31391 thread-groups=["i1"],
31392 regexp="exception_type",times="0"@}
31398 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31399 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31400 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31401 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31402 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31403 thread-id="1",stopped-threads="all",core="6"
31407 @subheading The @code{-catch-rethrow} Command
31408 @findex -catch-rethrow
31410 @subsubheading Synopsis
31413 -catch-rethrow [ -t ] [ -r @var{regexp}]
31416 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31417 then only exceptions whose type matches the regular expression will be
31420 If @samp{-t} is given, then the catchpoint is enabled only for one
31421 stop, the catchpoint is automatically deleted after the first event is
31424 @subsubheading @value{GDBN} Command
31426 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31427 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31429 @subsubheading Example
31432 -catch-rethrow -r exception_type
31433 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31434 what="exception rethrow",catch-type="rethrow",
31435 thread-groups=["i1"],
31436 regexp="exception_type",times="0"@}
31442 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31443 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31444 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31445 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31446 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31447 thread-id="1",stopped-threads="all",core="6"
31451 @subheading The @code{-catch-catch} Command
31452 @findex -catch-catch
31454 @subsubheading Synopsis
31457 -catch-catch [ -t ] [ -r @var{regexp}]
31460 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31461 is given, then only exceptions whose type matches the regular
31462 expression will be caught.
31464 If @samp{-t} is given, then the catchpoint is enabled only for one
31465 stop, the catchpoint is automatically deleted after the first event is
31468 @subsubheading @value{GDBN} Command
31470 The corresponding @value{GDBN} commands are @samp{catch catch}
31471 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31473 @subsubheading Example
31476 -catch-catch -r exception_type
31477 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31478 what="exception catch",catch-type="catch",
31479 thread-groups=["i1"],
31480 regexp="exception_type",times="0"@}
31486 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31487 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31488 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31489 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31490 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31491 thread-id="1",stopped-threads="all",core="6"
31495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31496 @node GDB/MI Program Context
31497 @section @sc{gdb/mi} Program Context
31499 @subheading The @code{-exec-arguments} Command
31500 @findex -exec-arguments
31503 @subsubheading Synopsis
31506 -exec-arguments @var{args}
31509 Set the inferior program arguments, to be used in the next
31512 @subsubheading @value{GDBN} Command
31514 The corresponding @value{GDBN} command is @samp{set args}.
31516 @subsubheading Example
31520 -exec-arguments -v word
31527 @subheading The @code{-exec-show-arguments} Command
31528 @findex -exec-show-arguments
31530 @subsubheading Synopsis
31533 -exec-show-arguments
31536 Print the arguments of the program.
31538 @subsubheading @value{GDBN} Command
31540 The corresponding @value{GDBN} command is @samp{show args}.
31542 @subsubheading Example
31547 @subheading The @code{-environment-cd} Command
31548 @findex -environment-cd
31550 @subsubheading Synopsis
31553 -environment-cd @var{pathdir}
31556 Set @value{GDBN}'s working directory.
31558 @subsubheading @value{GDBN} Command
31560 The corresponding @value{GDBN} command is @samp{cd}.
31562 @subsubheading Example
31566 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31572 @subheading The @code{-environment-directory} Command
31573 @findex -environment-directory
31575 @subsubheading Synopsis
31578 -environment-directory [ -r ] [ @var{pathdir} ]+
31581 Add directories @var{pathdir} to beginning of search path for source files.
31582 If the @samp{-r} option is used, the search path is reset to the default
31583 search path. If directories @var{pathdir} are supplied in addition to the
31584 @samp{-r} option, the search path is first reset and then addition
31586 Multiple directories may be specified, separated by blanks. Specifying
31587 multiple directories in a single command
31588 results in the directories added to the beginning of the
31589 search path in the same order they were presented in the command.
31590 If blanks are needed as
31591 part of a directory name, double-quotes should be used around
31592 the name. In the command output, the path will show up separated
31593 by the system directory-separator character. The directory-separator
31594 character must not be used
31595 in any directory name.
31596 If no directories are specified, the current search path is displayed.
31598 @subsubheading @value{GDBN} Command
31600 The corresponding @value{GDBN} command is @samp{dir}.
31602 @subsubheading Example
31606 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31607 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31609 -environment-directory ""
31610 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31612 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31613 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31615 -environment-directory -r
31616 ^done,source-path="$cdir:$cwd"
31621 @subheading The @code{-environment-path} Command
31622 @findex -environment-path
31624 @subsubheading Synopsis
31627 -environment-path [ -r ] [ @var{pathdir} ]+
31630 Add directories @var{pathdir} to beginning of search path for object files.
31631 If the @samp{-r} option is used, the search path is reset to the original
31632 search path that existed at gdb start-up. If directories @var{pathdir} are
31633 supplied in addition to the
31634 @samp{-r} option, the search path is first reset and then addition
31636 Multiple directories may be specified, separated by blanks. Specifying
31637 multiple directories in a single command
31638 results in the directories added to the beginning of the
31639 search path in the same order they were presented in the command.
31640 If blanks are needed as
31641 part of a directory name, double-quotes should be used around
31642 the name. In the command output, the path will show up separated
31643 by the system directory-separator character. The directory-separator
31644 character must not be used
31645 in any directory name.
31646 If no directories are specified, the current path is displayed.
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{path}.
31653 @subsubheading Example
31658 ^done,path="/usr/bin"
31660 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31661 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31663 -environment-path -r /usr/local/bin
31664 ^done,path="/usr/local/bin:/usr/bin"
31669 @subheading The @code{-environment-pwd} Command
31670 @findex -environment-pwd
31672 @subsubheading Synopsis
31678 Show the current working directory.
31680 @subsubheading @value{GDBN} Command
31682 The corresponding @value{GDBN} command is @samp{pwd}.
31684 @subsubheading Example
31689 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31694 @node GDB/MI Thread Commands
31695 @section @sc{gdb/mi} Thread Commands
31698 @subheading The @code{-thread-info} Command
31699 @findex -thread-info
31701 @subsubheading Synopsis
31704 -thread-info [ @var{thread-id} ]
31707 Reports information about either a specific thread, if the
31708 @var{thread-id} parameter is present, or about all threads.
31709 @var{thread-id} is the thread's global thread ID. When printing
31710 information about all threads, also reports the global ID of the
31713 @subsubheading @value{GDBN} Command
31715 The @samp{info thread} command prints the same information
31718 @subsubheading Result
31720 The result contains the following attributes:
31724 A list of threads. The format of the elements of the list is described in
31725 @ref{GDB/MI Thread Information}.
31727 @item current-thread-id
31728 The global id of the currently selected thread. This field is omitted if there
31729 is no selected thread (for example, when the selected inferior is not running,
31730 and therefore has no threads) or if a @var{thread-id} argument was passed to
31735 @subsubheading Example
31740 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31741 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31742 args=[]@},state="running"@},
31743 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31744 frame=@{level="0",addr="0x0804891f",func="foo",
31745 args=[@{name="i",value="10"@}],
31746 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31747 state="running"@}],
31748 current-thread-id="1"
31752 @subheading The @code{-thread-list-ids} Command
31753 @findex -thread-list-ids
31755 @subsubheading Synopsis
31761 Produces a list of the currently known global @value{GDBN} thread ids.
31762 At the end of the list it also prints the total number of such
31765 This command is retained for historical reasons, the
31766 @code{-thread-info} command should be used instead.
31768 @subsubheading @value{GDBN} Command
31770 Part of @samp{info threads} supplies the same information.
31772 @subsubheading Example
31777 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31778 current-thread-id="1",number-of-threads="3"
31783 @subheading The @code{-thread-select} Command
31784 @findex -thread-select
31786 @subsubheading Synopsis
31789 -thread-select @var{thread-id}
31792 Make thread with global thread number @var{thread-id} the current
31793 thread. It prints the number of the new current thread, and the
31794 topmost frame for that thread.
31796 This command is deprecated in favor of explicitly using the
31797 @samp{--thread} option to each command.
31799 @subsubheading @value{GDBN} Command
31801 The corresponding @value{GDBN} command is @samp{thread}.
31803 @subsubheading Example
31810 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31811 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31815 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31816 number-of-threads="3"
31819 ^done,new-thread-id="3",
31820 frame=@{level="0",func="vprintf",
31821 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31822 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31826 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31827 @node GDB/MI Ada Tasking Commands
31828 @section @sc{gdb/mi} Ada Tasking Commands
31830 @subheading The @code{-ada-task-info} Command
31831 @findex -ada-task-info
31833 @subsubheading Synopsis
31836 -ada-task-info [ @var{task-id} ]
31839 Reports information about either a specific Ada task, if the
31840 @var{task-id} parameter is present, or about all Ada tasks.
31842 @subsubheading @value{GDBN} Command
31844 The @samp{info tasks} command prints the same information
31845 about all Ada tasks (@pxref{Ada Tasks}).
31847 @subsubheading Result
31849 The result is a table of Ada tasks. The following columns are
31850 defined for each Ada task:
31854 This field exists only for the current thread. It has the value @samp{*}.
31857 The identifier that @value{GDBN} uses to refer to the Ada task.
31860 The identifier that the target uses to refer to the Ada task.
31863 The global thread identifier of the thread corresponding to the Ada
31866 This field should always exist, as Ada tasks are always implemented
31867 on top of a thread. But if @value{GDBN} cannot find this corresponding
31868 thread for any reason, the field is omitted.
31871 This field exists only when the task was created by another task.
31872 In this case, it provides the ID of the parent task.
31875 The base priority of the task.
31878 The current state of the task. For a detailed description of the
31879 possible states, see @ref{Ada Tasks}.
31882 The name of the task.
31886 @subsubheading Example
31890 ^done,tasks=@{nr_rows="3",nr_cols="8",
31891 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31892 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31893 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31894 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31895 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31896 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31897 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31898 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31899 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31900 state="Child Termination Wait",name="main_task"@}]@}
31904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31905 @node GDB/MI Program Execution
31906 @section @sc{gdb/mi} Program Execution
31908 These are the asynchronous commands which generate the out-of-band
31909 record @samp{*stopped}. Currently @value{GDBN} only really executes
31910 asynchronously with remote targets and this interaction is mimicked in
31913 @subheading The @code{-exec-continue} Command
31914 @findex -exec-continue
31916 @subsubheading Synopsis
31919 -exec-continue [--reverse] [--all|--thread-group N]
31922 Resumes the execution of the inferior program, which will continue
31923 to execute until it reaches a debugger stop event. If the
31924 @samp{--reverse} option is specified, execution resumes in reverse until
31925 it reaches a stop event. Stop events may include
31928 breakpoints or watchpoints
31930 signals or exceptions
31932 the end of the process (or its beginning under @samp{--reverse})
31934 the end or beginning of a replay log if one is being used.
31936 In all-stop mode (@pxref{All-Stop
31937 Mode}), may resume only one thread, or all threads, depending on the
31938 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31939 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31940 ignored in all-stop mode. If the @samp{--thread-group} options is
31941 specified, then all threads in that thread group are resumed.
31943 @subsubheading @value{GDBN} Command
31945 The corresponding @value{GDBN} corresponding is @samp{continue}.
31947 @subsubheading Example
31954 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31955 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31956 line="13",arch="i386:x86_64"@}
31961 @subheading The @code{-exec-finish} Command
31962 @findex -exec-finish
31964 @subsubheading Synopsis
31967 -exec-finish [--reverse]
31970 Resumes the execution of the inferior program until the current
31971 function is exited. Displays the results returned by the function.
31972 If the @samp{--reverse} option is specified, resumes the reverse
31973 execution of the inferior program until the point where current
31974 function was called.
31976 @subsubheading @value{GDBN} Command
31978 The corresponding @value{GDBN} command is @samp{finish}.
31980 @subsubheading Example
31982 Function returning @code{void}.
31989 *stopped,reason="function-finished",frame=@{func="main",args=[],
31990 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
31994 Function returning other than @code{void}. The name of the internal
31995 @value{GDBN} variable storing the result is printed, together with the
32002 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32003 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32005 arch="i386:x86_64"@},
32006 gdb-result-var="$1",return-value="0"
32011 @subheading The @code{-exec-interrupt} Command
32012 @findex -exec-interrupt
32014 @subsubheading Synopsis
32017 -exec-interrupt [--all|--thread-group N]
32020 Interrupts the background execution of the target. Note how the token
32021 associated with the stop message is the one for the execution command
32022 that has been interrupted. The token for the interrupt itself only
32023 appears in the @samp{^done} output. If the user is trying to
32024 interrupt a non-running program, an error message will be printed.
32026 Note that when asynchronous execution is enabled, this command is
32027 asynchronous just like other execution commands. That is, first the
32028 @samp{^done} response will be printed, and the target stop will be
32029 reported after that using the @samp{*stopped} notification.
32031 In non-stop mode, only the context thread is interrupted by default.
32032 All threads (in all inferiors) will be interrupted if the
32033 @samp{--all} option is specified. If the @samp{--thread-group}
32034 option is specified, all threads in that group will be interrupted.
32036 @subsubheading @value{GDBN} Command
32038 The corresponding @value{GDBN} command is @samp{interrupt}.
32040 @subsubheading Example
32051 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32052 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32053 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32058 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32062 @subheading The @code{-exec-jump} Command
32065 @subsubheading Synopsis
32068 -exec-jump @var{location}
32071 Resumes execution of the inferior program at the location specified by
32072 parameter. @xref{Specify Location}, for a description of the
32073 different forms of @var{location}.
32075 @subsubheading @value{GDBN} Command
32077 The corresponding @value{GDBN} command is @samp{jump}.
32079 @subsubheading Example
32082 -exec-jump foo.c:10
32083 *running,thread-id="all"
32088 @subheading The @code{-exec-next} Command
32091 @subsubheading Synopsis
32094 -exec-next [--reverse]
32097 Resumes execution of the inferior program, stopping when the beginning
32098 of the next source line is reached.
32100 If the @samp{--reverse} option is specified, resumes reverse execution
32101 of the inferior program, stopping at the beginning of the previous
32102 source line. If you issue this command on the first line of a
32103 function, it will take you back to the caller of that function, to the
32104 source line where the function was called.
32107 @subsubheading @value{GDBN} Command
32109 The corresponding @value{GDBN} command is @samp{next}.
32111 @subsubheading Example
32117 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32122 @subheading The @code{-exec-next-instruction} Command
32123 @findex -exec-next-instruction
32125 @subsubheading Synopsis
32128 -exec-next-instruction [--reverse]
32131 Executes one machine instruction. If the instruction is a function
32132 call, continues until the function returns. If the program stops at an
32133 instruction in the middle of a source line, the address will be
32136 If the @samp{--reverse} option is specified, resumes reverse execution
32137 of the inferior program, stopping at the previous instruction. If the
32138 previously executed instruction was a return from another function,
32139 it will continue to execute in reverse until the call to that function
32140 (from the current stack frame) is reached.
32142 @subsubheading @value{GDBN} Command
32144 The corresponding @value{GDBN} command is @samp{nexti}.
32146 @subsubheading Example
32150 -exec-next-instruction
32154 *stopped,reason="end-stepping-range",
32155 addr="0x000100d4",line="5",file="hello.c"
32160 @subheading The @code{-exec-return} Command
32161 @findex -exec-return
32163 @subsubheading Synopsis
32169 Makes current function return immediately. Doesn't execute the inferior.
32170 Displays the new current frame.
32172 @subsubheading @value{GDBN} Command
32174 The corresponding @value{GDBN} command is @samp{return}.
32176 @subsubheading Example
32180 200-break-insert callee4
32181 200^done,bkpt=@{number="1",addr="0x00010734",
32182 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32187 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32188 frame=@{func="callee4",args=[],
32189 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32190 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32191 arch="i386:x86_64"@}
32197 111^done,frame=@{level="0",func="callee3",
32198 args=[@{name="strarg",
32199 value="0x11940 \"A string argument.\""@}],
32200 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32201 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32202 arch="i386:x86_64"@}
32207 @subheading The @code{-exec-run} Command
32210 @subsubheading Synopsis
32213 -exec-run [ --all | --thread-group N ] [ --start ]
32216 Starts execution of the inferior from the beginning. The inferior
32217 executes until either a breakpoint is encountered or the program
32218 exits. In the latter case the output will include an exit code, if
32219 the program has exited exceptionally.
32221 When neither the @samp{--all} nor the @samp{--thread-group} option
32222 is specified, the current inferior is started. If the
32223 @samp{--thread-group} option is specified, it should refer to a thread
32224 group of type @samp{process}, and that thread group will be started.
32225 If the @samp{--all} option is specified, then all inferiors will be started.
32227 Using the @samp{--start} option instructs the debugger to stop
32228 the execution at the start of the inferior's main subprogram,
32229 following the same behavior as the @code{start} command
32230 (@pxref{Starting}).
32232 @subsubheading @value{GDBN} Command
32234 The corresponding @value{GDBN} command is @samp{run}.
32236 @subsubheading Examples
32241 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32246 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32247 frame=@{func="main",args=[],file="recursive2.c",
32248 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32253 Program exited normally:
32261 *stopped,reason="exited-normally"
32266 Program exited exceptionally:
32274 *stopped,reason="exited",exit-code="01"
32278 Another way the program can terminate is if it receives a signal such as
32279 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32283 *stopped,reason="exited-signalled",signal-name="SIGINT",
32284 signal-meaning="Interrupt"
32288 @c @subheading -exec-signal
32291 @subheading The @code{-exec-step} Command
32294 @subsubheading Synopsis
32297 -exec-step [--reverse]
32300 Resumes execution of the inferior program, stopping when the beginning
32301 of the next source line is reached, if the next source line is not a
32302 function call. If it is, stop at the first instruction of the called
32303 function. If the @samp{--reverse} option is specified, resumes reverse
32304 execution of the inferior program, stopping at the beginning of the
32305 previously executed source line.
32307 @subsubheading @value{GDBN} Command
32309 The corresponding @value{GDBN} command is @samp{step}.
32311 @subsubheading Example
32313 Stepping into a function:
32319 *stopped,reason="end-stepping-range",
32320 frame=@{func="foo",args=[@{name="a",value="10"@},
32321 @{name="b",value="0"@}],file="recursive2.c",
32322 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32332 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32337 @subheading The @code{-exec-step-instruction} Command
32338 @findex -exec-step-instruction
32340 @subsubheading Synopsis
32343 -exec-step-instruction [--reverse]
32346 Resumes the inferior which executes one machine instruction. If the
32347 @samp{--reverse} option is specified, resumes reverse execution of the
32348 inferior program, stopping at the previously executed instruction.
32349 The output, once @value{GDBN} has stopped, will vary depending on
32350 whether we have stopped in the middle of a source line or not. In the
32351 former case, the address at which the program stopped will be printed
32354 @subsubheading @value{GDBN} Command
32356 The corresponding @value{GDBN} command is @samp{stepi}.
32358 @subsubheading Example
32362 -exec-step-instruction
32366 *stopped,reason="end-stepping-range",
32367 frame=@{func="foo",args=[],file="try.c",
32368 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32370 -exec-step-instruction
32374 *stopped,reason="end-stepping-range",
32375 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32376 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32381 @subheading The @code{-exec-until} Command
32382 @findex -exec-until
32384 @subsubheading Synopsis
32387 -exec-until [ @var{location} ]
32390 Executes the inferior until the @var{location} specified in the
32391 argument is reached. If there is no argument, the inferior executes
32392 until a source line greater than the current one is reached. The
32393 reason for stopping in this case will be @samp{location-reached}.
32395 @subsubheading @value{GDBN} Command
32397 The corresponding @value{GDBN} command is @samp{until}.
32399 @subsubheading Example
32403 -exec-until recursive2.c:6
32407 *stopped,reason="location-reached",frame=@{func="main",args=[],
32408 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32409 arch="i386:x86_64"@}
32414 @subheading -file-clear
32415 Is this going away????
32418 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32419 @node GDB/MI Stack Manipulation
32420 @section @sc{gdb/mi} Stack Manipulation Commands
32422 @subheading The @code{-enable-frame-filters} Command
32423 @findex -enable-frame-filters
32426 -enable-frame-filters
32429 @value{GDBN} allows Python-based frame filters to affect the output of
32430 the MI commands relating to stack traces. As there is no way to
32431 implement this in a fully backward-compatible way, a front end must
32432 request that this functionality be enabled.
32434 Once enabled, this feature cannot be disabled.
32436 Note that if Python support has not been compiled into @value{GDBN},
32437 this command will still succeed (and do nothing).
32439 @subheading The @code{-stack-info-frame} Command
32440 @findex -stack-info-frame
32442 @subsubheading Synopsis
32448 Get info on the selected frame.
32450 @subsubheading @value{GDBN} Command
32452 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32453 (without arguments).
32455 @subsubheading Example
32460 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32461 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32462 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32463 arch="i386:x86_64"@}
32467 @subheading The @code{-stack-info-depth} Command
32468 @findex -stack-info-depth
32470 @subsubheading Synopsis
32473 -stack-info-depth [ @var{max-depth} ]
32476 Return the depth of the stack. If the integer argument @var{max-depth}
32477 is specified, do not count beyond @var{max-depth} frames.
32479 @subsubheading @value{GDBN} Command
32481 There's no equivalent @value{GDBN} command.
32483 @subsubheading Example
32485 For a stack with frame levels 0 through 11:
32492 -stack-info-depth 4
32495 -stack-info-depth 12
32498 -stack-info-depth 11
32501 -stack-info-depth 13
32506 @anchor{-stack-list-arguments}
32507 @subheading The @code{-stack-list-arguments} Command
32508 @findex -stack-list-arguments
32510 @subsubheading Synopsis
32513 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32514 [ @var{low-frame} @var{high-frame} ]
32517 Display a list of the arguments for the frames between @var{low-frame}
32518 and @var{high-frame} (inclusive). If @var{low-frame} and
32519 @var{high-frame} are not provided, list the arguments for the whole
32520 call stack. If the two arguments are equal, show the single frame
32521 at the corresponding level. It is an error if @var{low-frame} is
32522 larger than the actual number of frames. On the other hand,
32523 @var{high-frame} may be larger than the actual number of frames, in
32524 which case only existing frames will be returned.
32526 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32527 the variables; if it is 1 or @code{--all-values}, print also their
32528 values; and if it is 2 or @code{--simple-values}, print the name,
32529 type and value for simple data types, and the name and type for arrays,
32530 structures and unions. If the option @code{--no-frame-filters} is
32531 supplied, then Python frame filters will not be executed.
32533 If the @code{--skip-unavailable} option is specified, arguments that
32534 are not available are not listed. Partially available arguments
32535 are still displayed, however.
32537 Use of this command to obtain arguments in a single frame is
32538 deprecated in favor of the @samp{-stack-list-variables} command.
32540 @subsubheading @value{GDBN} Command
32542 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32543 @samp{gdb_get_args} command which partially overlaps with the
32544 functionality of @samp{-stack-list-arguments}.
32546 @subsubheading Example
32553 frame=@{level="0",addr="0x00010734",func="callee4",
32554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32555 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32556 arch="i386:x86_64"@},
32557 frame=@{level="1",addr="0x0001076c",func="callee3",
32558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32560 arch="i386:x86_64"@},
32561 frame=@{level="2",addr="0x0001078c",func="callee2",
32562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32563 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32564 arch="i386:x86_64"@},
32565 frame=@{level="3",addr="0x000107b4",func="callee1",
32566 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32567 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32568 arch="i386:x86_64"@},
32569 frame=@{level="4",addr="0x000107e0",func="main",
32570 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32571 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32572 arch="i386:x86_64"@}]
32574 -stack-list-arguments 0
32577 frame=@{level="0",args=[]@},
32578 frame=@{level="1",args=[name="strarg"]@},
32579 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32580 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32581 frame=@{level="4",args=[]@}]
32583 -stack-list-arguments 1
32586 frame=@{level="0",args=[]@},
32588 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32589 frame=@{level="2",args=[
32590 @{name="intarg",value="2"@},
32591 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32592 @{frame=@{level="3",args=[
32593 @{name="intarg",value="2"@},
32594 @{name="strarg",value="0x11940 \"A string argument.\""@},
32595 @{name="fltarg",value="3.5"@}]@},
32596 frame=@{level="4",args=[]@}]
32598 -stack-list-arguments 0 2 2
32599 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32601 -stack-list-arguments 1 2 2
32602 ^done,stack-args=[frame=@{level="2",
32603 args=[@{name="intarg",value="2"@},
32604 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32608 @c @subheading -stack-list-exception-handlers
32611 @anchor{-stack-list-frames}
32612 @subheading The @code{-stack-list-frames} Command
32613 @findex -stack-list-frames
32615 @subsubheading Synopsis
32618 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32621 List the frames currently on the stack. For each frame it displays the
32626 The frame number, 0 being the topmost frame, i.e., the innermost function.
32628 The @code{$pc} value for that frame.
32632 File name of the source file where the function lives.
32633 @item @var{fullname}
32634 The full file name of the source file where the function lives.
32636 Line number corresponding to the @code{$pc}.
32638 The shared library where this function is defined. This is only given
32639 if the frame's function is not known.
32641 Frame's architecture.
32644 If invoked without arguments, this command prints a backtrace for the
32645 whole stack. If given two integer arguments, it shows the frames whose
32646 levels are between the two arguments (inclusive). If the two arguments
32647 are equal, it shows the single frame at the corresponding level. It is
32648 an error if @var{low-frame} is larger than the actual number of
32649 frames. On the other hand, @var{high-frame} may be larger than the
32650 actual number of frames, in which case only existing frames will be
32651 returned. If the option @code{--no-frame-filters} is supplied, then
32652 Python frame filters will not be executed.
32654 @subsubheading @value{GDBN} Command
32656 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32658 @subsubheading Example
32660 Full stack backtrace:
32666 [frame=@{level="0",addr="0x0001076c",func="foo",
32667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32668 arch="i386:x86_64"@},
32669 frame=@{level="1",addr="0x000107a4",func="foo",
32670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32671 arch="i386:x86_64"@},
32672 frame=@{level="2",addr="0x000107a4",func="foo",
32673 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32674 arch="i386:x86_64"@},
32675 frame=@{level="3",addr="0x000107a4",func="foo",
32676 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32677 arch="i386:x86_64"@},
32678 frame=@{level="4",addr="0x000107a4",func="foo",
32679 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32680 arch="i386:x86_64"@},
32681 frame=@{level="5",addr="0x000107a4",func="foo",
32682 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32683 arch="i386:x86_64"@},
32684 frame=@{level="6",addr="0x000107a4",func="foo",
32685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32686 arch="i386:x86_64"@},
32687 frame=@{level="7",addr="0x000107a4",func="foo",
32688 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32689 arch="i386:x86_64"@},
32690 frame=@{level="8",addr="0x000107a4",func="foo",
32691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32692 arch="i386:x86_64"@},
32693 frame=@{level="9",addr="0x000107a4",func="foo",
32694 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32695 arch="i386:x86_64"@},
32696 frame=@{level="10",addr="0x000107a4",func="foo",
32697 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32698 arch="i386:x86_64"@},
32699 frame=@{level="11",addr="0x00010738",func="main",
32700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32701 arch="i386:x86_64"@}]
32705 Show frames between @var{low_frame} and @var{high_frame}:
32709 -stack-list-frames 3 5
32711 [frame=@{level="3",addr="0x000107a4",func="foo",
32712 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32713 arch="i386:x86_64"@},
32714 frame=@{level="4",addr="0x000107a4",func="foo",
32715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32716 arch="i386:x86_64"@},
32717 frame=@{level="5",addr="0x000107a4",func="foo",
32718 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32719 arch="i386:x86_64"@}]
32723 Show a single frame:
32727 -stack-list-frames 3 3
32729 [frame=@{level="3",addr="0x000107a4",func="foo",
32730 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32731 arch="i386:x86_64"@}]
32736 @subheading The @code{-stack-list-locals} Command
32737 @findex -stack-list-locals
32738 @anchor{-stack-list-locals}
32740 @subsubheading Synopsis
32743 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32746 Display the local variable names for the selected frame. If
32747 @var{print-values} is 0 or @code{--no-values}, print only the names of
32748 the variables; if it is 1 or @code{--all-values}, print also their
32749 values; and if it is 2 or @code{--simple-values}, print the name,
32750 type and value for simple data types, and the name and type for arrays,
32751 structures and unions. In this last case, a frontend can immediately
32752 display the value of simple data types and create variable objects for
32753 other data types when the user wishes to explore their values in
32754 more detail. If the option @code{--no-frame-filters} is supplied, then
32755 Python frame filters will not be executed.
32757 If the @code{--skip-unavailable} option is specified, local variables
32758 that are not available are not listed. Partially available local
32759 variables are still displayed, however.
32761 This command is deprecated in favor of the
32762 @samp{-stack-list-variables} command.
32764 @subsubheading @value{GDBN} Command
32766 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32768 @subsubheading Example
32772 -stack-list-locals 0
32773 ^done,locals=[name="A",name="B",name="C"]
32775 -stack-list-locals --all-values
32776 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32777 @{name="C",value="@{1, 2, 3@}"@}]
32778 -stack-list-locals --simple-values
32779 ^done,locals=[@{name="A",type="int",value="1"@},
32780 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32784 @anchor{-stack-list-variables}
32785 @subheading The @code{-stack-list-variables} Command
32786 @findex -stack-list-variables
32788 @subsubheading Synopsis
32791 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32794 Display the names of local variables and function arguments for the selected frame. If
32795 @var{print-values} is 0 or @code{--no-values}, print only the names of
32796 the variables; if it is 1 or @code{--all-values}, print also their
32797 values; and if it is 2 or @code{--simple-values}, print the name,
32798 type and value for simple data types, and the name and type for arrays,
32799 structures and unions. If the option @code{--no-frame-filters} is
32800 supplied, then Python frame filters will not be executed.
32802 If the @code{--skip-unavailable} option is specified, local variables
32803 and arguments that are not available are not listed. Partially
32804 available arguments and local variables are still displayed, however.
32806 @subsubheading Example
32810 -stack-list-variables --thread 1 --frame 0 --all-values
32811 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32816 @subheading The @code{-stack-select-frame} Command
32817 @findex -stack-select-frame
32819 @subsubheading Synopsis
32822 -stack-select-frame @var{framenum}
32825 Change the selected frame. Select a different frame @var{framenum} on
32828 This command in deprecated in favor of passing the @samp{--frame}
32829 option to every command.
32831 @subsubheading @value{GDBN} Command
32833 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32834 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32836 @subsubheading Example
32840 -stack-select-frame 2
32845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32846 @node GDB/MI Variable Objects
32847 @section @sc{gdb/mi} Variable Objects
32851 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32853 For the implementation of a variable debugger window (locals, watched
32854 expressions, etc.), we are proposing the adaptation of the existing code
32855 used by @code{Insight}.
32857 The two main reasons for that are:
32861 It has been proven in practice (it is already on its second generation).
32864 It will shorten development time (needless to say how important it is
32868 The original interface was designed to be used by Tcl code, so it was
32869 slightly changed so it could be used through @sc{gdb/mi}. This section
32870 describes the @sc{gdb/mi} operations that will be available and gives some
32871 hints about their use.
32873 @emph{Note}: In addition to the set of operations described here, we
32874 expect the @sc{gui} implementation of a variable window to require, at
32875 least, the following operations:
32878 @item @code{-gdb-show} @code{output-radix}
32879 @item @code{-stack-list-arguments}
32880 @item @code{-stack-list-locals}
32881 @item @code{-stack-select-frame}
32886 @subheading Introduction to Variable Objects
32888 @cindex variable objects in @sc{gdb/mi}
32890 Variable objects are "object-oriented" MI interface for examining and
32891 changing values of expressions. Unlike some other MI interfaces that
32892 work with expressions, variable objects are specifically designed for
32893 simple and efficient presentation in the frontend. A variable object
32894 is identified by string name. When a variable object is created, the
32895 frontend specifies the expression for that variable object. The
32896 expression can be a simple variable, or it can be an arbitrary complex
32897 expression, and can even involve CPU registers. After creating a
32898 variable object, the frontend can invoke other variable object
32899 operations---for example to obtain or change the value of a variable
32900 object, or to change display format.
32902 Variable objects have hierarchical tree structure. Any variable object
32903 that corresponds to a composite type, such as structure in C, has
32904 a number of child variable objects, for example corresponding to each
32905 element of a structure. A child variable object can itself have
32906 children, recursively. Recursion ends when we reach
32907 leaf variable objects, which always have built-in types. Child variable
32908 objects are created only by explicit request, so if a frontend
32909 is not interested in the children of a particular variable object, no
32910 child will be created.
32912 For a leaf variable object it is possible to obtain its value as a
32913 string, or set the value from a string. String value can be also
32914 obtained for a non-leaf variable object, but it's generally a string
32915 that only indicates the type of the object, and does not list its
32916 contents. Assignment to a non-leaf variable object is not allowed.
32918 A frontend does not need to read the values of all variable objects each time
32919 the program stops. Instead, MI provides an update command that lists all
32920 variable objects whose values has changed since the last update
32921 operation. This considerably reduces the amount of data that must
32922 be transferred to the frontend. As noted above, children variable
32923 objects are created on demand, and only leaf variable objects have a
32924 real value. As result, gdb will read target memory only for leaf
32925 variables that frontend has created.
32927 The automatic update is not always desirable. For example, a frontend
32928 might want to keep a value of some expression for future reference,
32929 and never update it. For another example, fetching memory is
32930 relatively slow for embedded targets, so a frontend might want
32931 to disable automatic update for the variables that are either not
32932 visible on the screen, or ``closed''. This is possible using so
32933 called ``frozen variable objects''. Such variable objects are never
32934 implicitly updated.
32936 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32937 fixed variable object, the expression is parsed when the variable
32938 object is created, including associating identifiers to specific
32939 variables. The meaning of expression never changes. For a floating
32940 variable object the values of variables whose names appear in the
32941 expressions are re-evaluated every time in the context of the current
32942 frame. Consider this example:
32947 struct work_state state;
32954 If a fixed variable object for the @code{state} variable is created in
32955 this function, and we enter the recursive call, the variable
32956 object will report the value of @code{state} in the top-level
32957 @code{do_work} invocation. On the other hand, a floating variable
32958 object will report the value of @code{state} in the current frame.
32960 If an expression specified when creating a fixed variable object
32961 refers to a local variable, the variable object becomes bound to the
32962 thread and frame in which the variable object is created. When such
32963 variable object is updated, @value{GDBN} makes sure that the
32964 thread/frame combination the variable object is bound to still exists,
32965 and re-evaluates the variable object in context of that thread/frame.
32967 The following is the complete set of @sc{gdb/mi} operations defined to
32968 access this functionality:
32970 @multitable @columnfractions .4 .6
32971 @item @strong{Operation}
32972 @tab @strong{Description}
32974 @item @code{-enable-pretty-printing}
32975 @tab enable Python-based pretty-printing
32976 @item @code{-var-create}
32977 @tab create a variable object
32978 @item @code{-var-delete}
32979 @tab delete the variable object and/or its children
32980 @item @code{-var-set-format}
32981 @tab set the display format of this variable
32982 @item @code{-var-show-format}
32983 @tab show the display format of this variable
32984 @item @code{-var-info-num-children}
32985 @tab tells how many children this object has
32986 @item @code{-var-list-children}
32987 @tab return a list of the object's children
32988 @item @code{-var-info-type}
32989 @tab show the type of this variable object
32990 @item @code{-var-info-expression}
32991 @tab print parent-relative expression that this variable object represents
32992 @item @code{-var-info-path-expression}
32993 @tab print full expression that this variable object represents
32994 @item @code{-var-show-attributes}
32995 @tab is this variable editable? does it exist here?
32996 @item @code{-var-evaluate-expression}
32997 @tab get the value of this variable
32998 @item @code{-var-assign}
32999 @tab set the value of this variable
33000 @item @code{-var-update}
33001 @tab update the variable and its children
33002 @item @code{-var-set-frozen}
33003 @tab set frozenness attribute
33004 @item @code{-var-set-update-range}
33005 @tab set range of children to display on update
33008 In the next subsection we describe each operation in detail and suggest
33009 how it can be used.
33011 @subheading Description And Use of Operations on Variable Objects
33013 @subheading The @code{-enable-pretty-printing} Command
33014 @findex -enable-pretty-printing
33017 -enable-pretty-printing
33020 @value{GDBN} allows Python-based visualizers to affect the output of the
33021 MI variable object commands. However, because there was no way to
33022 implement this in a fully backward-compatible way, a front end must
33023 request that this functionality be enabled.
33025 Once enabled, this feature cannot be disabled.
33027 Note that if Python support has not been compiled into @value{GDBN},
33028 this command will still succeed (and do nothing).
33030 This feature is currently (as of @value{GDBN} 7.0) experimental, and
33031 may work differently in future versions of @value{GDBN}.
33033 @subheading The @code{-var-create} Command
33034 @findex -var-create
33036 @subsubheading Synopsis
33039 -var-create @{@var{name} | "-"@}
33040 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33043 This operation creates a variable object, which allows the monitoring of
33044 a variable, the result of an expression, a memory cell or a CPU
33047 The @var{name} parameter is the string by which the object can be
33048 referenced. It must be unique. If @samp{-} is specified, the varobj
33049 system will generate a string ``varNNNNNN'' automatically. It will be
33050 unique provided that one does not specify @var{name} of that format.
33051 The command fails if a duplicate name is found.
33053 The frame under which the expression should be evaluated can be
33054 specified by @var{frame-addr}. A @samp{*} indicates that the current
33055 frame should be used. A @samp{@@} indicates that a floating variable
33056 object must be created.
33058 @var{expression} is any expression valid on the current language set (must not
33059 begin with a @samp{*}), or one of the following:
33063 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33066 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33069 @samp{$@var{regname}} --- a CPU register name
33072 @cindex dynamic varobj
33073 A varobj's contents may be provided by a Python-based pretty-printer. In this
33074 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33075 have slightly different semantics in some cases. If the
33076 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33077 will never create a dynamic varobj. This ensures backward
33078 compatibility for existing clients.
33080 @subsubheading Result
33082 This operation returns attributes of the newly-created varobj. These
33087 The name of the varobj.
33090 The number of children of the varobj. This number is not necessarily
33091 reliable for a dynamic varobj. Instead, you must examine the
33092 @samp{has_more} attribute.
33095 The varobj's scalar value. For a varobj whose type is some sort of
33096 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33097 will not be interesting.
33100 The varobj's type. This is a string representation of the type, as
33101 would be printed by the @value{GDBN} CLI. If @samp{print object}
33102 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33103 @emph{actual} (derived) type of the object is shown rather than the
33104 @emph{declared} one.
33107 If a variable object is bound to a specific thread, then this is the
33108 thread's global identifier.
33111 For a dynamic varobj, this indicates whether there appear to be any
33112 children available. For a non-dynamic varobj, this will be 0.
33115 This attribute will be present and have the value @samp{1} if the
33116 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33117 then this attribute will not be present.
33120 A dynamic varobj can supply a display hint to the front end. The
33121 value comes directly from the Python pretty-printer object's
33122 @code{display_hint} method. @xref{Pretty Printing API}.
33125 Typical output will look like this:
33128 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33129 has_more="@var{has_more}"
33133 @subheading The @code{-var-delete} Command
33134 @findex -var-delete
33136 @subsubheading Synopsis
33139 -var-delete [ -c ] @var{name}
33142 Deletes a previously created variable object and all of its children.
33143 With the @samp{-c} option, just deletes the children.
33145 Returns an error if the object @var{name} is not found.
33148 @subheading The @code{-var-set-format} Command
33149 @findex -var-set-format
33151 @subsubheading Synopsis
33154 -var-set-format @var{name} @var{format-spec}
33157 Sets the output format for the value of the object @var{name} to be
33160 @anchor{-var-set-format}
33161 The syntax for the @var{format-spec} is as follows:
33164 @var{format-spec} @expansion{}
33165 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33168 The natural format is the default format choosen automatically
33169 based on the variable type (like decimal for an @code{int}, hex
33170 for pointers, etc.).
33172 The zero-hexadecimal format has a representation similar to hexadecimal
33173 but with padding zeroes to the left of the value. For example, a 32-bit
33174 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33175 zero-hexadecimal format.
33177 For a variable with children, the format is set only on the
33178 variable itself, and the children are not affected.
33180 @subheading The @code{-var-show-format} Command
33181 @findex -var-show-format
33183 @subsubheading Synopsis
33186 -var-show-format @var{name}
33189 Returns the format used to display the value of the object @var{name}.
33192 @var{format} @expansion{}
33197 @subheading The @code{-var-info-num-children} Command
33198 @findex -var-info-num-children
33200 @subsubheading Synopsis
33203 -var-info-num-children @var{name}
33206 Returns the number of children of a variable object @var{name}:
33212 Note that this number is not completely reliable for a dynamic varobj.
33213 It will return the current number of children, but more children may
33217 @subheading The @code{-var-list-children} Command
33218 @findex -var-list-children
33220 @subsubheading Synopsis
33223 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33225 @anchor{-var-list-children}
33227 Return a list of the children of the specified variable object and
33228 create variable objects for them, if they do not already exist. With
33229 a single argument or if @var{print-values} has a value of 0 or
33230 @code{--no-values}, print only the names of the variables; if
33231 @var{print-values} is 1 or @code{--all-values}, also print their
33232 values; and if it is 2 or @code{--simple-values} print the name and
33233 value for simple data types and just the name for arrays, structures
33236 @var{from} and @var{to}, if specified, indicate the range of children
33237 to report. If @var{from} or @var{to} is less than zero, the range is
33238 reset and all children will be reported. Otherwise, children starting
33239 at @var{from} (zero-based) and up to and excluding @var{to} will be
33242 If a child range is requested, it will only affect the current call to
33243 @code{-var-list-children}, but not future calls to @code{-var-update}.
33244 For this, you must instead use @code{-var-set-update-range}. The
33245 intent of this approach is to enable a front end to implement any
33246 update approach it likes; for example, scrolling a view may cause the
33247 front end to request more children with @code{-var-list-children}, and
33248 then the front end could call @code{-var-set-update-range} with a
33249 different range to ensure that future updates are restricted to just
33252 For each child the following results are returned:
33257 Name of the variable object created for this child.
33260 The expression to be shown to the user by the front end to designate this child.
33261 For example this may be the name of a structure member.
33263 For a dynamic varobj, this value cannot be used to form an
33264 expression. There is no way to do this at all with a dynamic varobj.
33266 For C/C@t{++} structures there are several pseudo children returned to
33267 designate access qualifiers. For these pseudo children @var{exp} is
33268 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33269 type and value are not present.
33271 A dynamic varobj will not report the access qualifying
33272 pseudo-children, regardless of the language. This information is not
33273 available at all with a dynamic varobj.
33276 Number of children this child has. For a dynamic varobj, this will be
33280 The type of the child. If @samp{print object}
33281 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33282 @emph{actual} (derived) type of the object is shown rather than the
33283 @emph{declared} one.
33286 If values were requested, this is the value.
33289 If this variable object is associated with a thread, this is the
33290 thread's global thread id. Otherwise this result is not present.
33293 If the variable object is frozen, this variable will be present with a value of 1.
33296 A dynamic varobj can supply a display hint to the front end. The
33297 value comes directly from the Python pretty-printer object's
33298 @code{display_hint} method. @xref{Pretty Printing API}.
33301 This attribute will be present and have the value @samp{1} if the
33302 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33303 then this attribute will not be present.
33307 The result may have its own attributes:
33311 A dynamic varobj can supply a display hint to the front end. The
33312 value comes directly from the Python pretty-printer object's
33313 @code{display_hint} method. @xref{Pretty Printing API}.
33316 This is an integer attribute which is nonzero if there are children
33317 remaining after the end of the selected range.
33320 @subsubheading Example
33324 -var-list-children n
33325 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33326 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33328 -var-list-children --all-values n
33329 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33330 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33334 @subheading The @code{-var-info-type} Command
33335 @findex -var-info-type
33337 @subsubheading Synopsis
33340 -var-info-type @var{name}
33343 Returns the type of the specified variable @var{name}. The type is
33344 returned as a string in the same format as it is output by the
33348 type=@var{typename}
33352 @subheading The @code{-var-info-expression} Command
33353 @findex -var-info-expression
33355 @subsubheading Synopsis
33358 -var-info-expression @var{name}
33361 Returns a string that is suitable for presenting this
33362 variable object in user interface. The string is generally
33363 not valid expression in the current language, and cannot be evaluated.
33365 For example, if @code{a} is an array, and variable object
33366 @code{A} was created for @code{a}, then we'll get this output:
33369 (gdb) -var-info-expression A.1
33370 ^done,lang="C",exp="1"
33374 Here, the value of @code{lang} is the language name, which can be
33375 found in @ref{Supported Languages}.
33377 Note that the output of the @code{-var-list-children} command also
33378 includes those expressions, so the @code{-var-info-expression} command
33381 @subheading The @code{-var-info-path-expression} Command
33382 @findex -var-info-path-expression
33384 @subsubheading Synopsis
33387 -var-info-path-expression @var{name}
33390 Returns an expression that can be evaluated in the current
33391 context and will yield the same value that a variable object has.
33392 Compare this with the @code{-var-info-expression} command, which
33393 result can be used only for UI presentation. Typical use of
33394 the @code{-var-info-path-expression} command is creating a
33395 watchpoint from a variable object.
33397 This command is currently not valid for children of a dynamic varobj,
33398 and will give an error when invoked on one.
33400 For example, suppose @code{C} is a C@t{++} class, derived from class
33401 @code{Base}, and that the @code{Base} class has a member called
33402 @code{m_size}. Assume a variable @code{c} is has the type of
33403 @code{C} and a variable object @code{C} was created for variable
33404 @code{c}. Then, we'll get this output:
33406 (gdb) -var-info-path-expression C.Base.public.m_size
33407 ^done,path_expr=((Base)c).m_size)
33410 @subheading The @code{-var-show-attributes} Command
33411 @findex -var-show-attributes
33413 @subsubheading Synopsis
33416 -var-show-attributes @var{name}
33419 List attributes of the specified variable object @var{name}:
33422 status=@var{attr} [ ( ,@var{attr} )* ]
33426 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33428 @subheading The @code{-var-evaluate-expression} Command
33429 @findex -var-evaluate-expression
33431 @subsubheading Synopsis
33434 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33437 Evaluates the expression that is represented by the specified variable
33438 object and returns its value as a string. The format of the string
33439 can be specified with the @samp{-f} option. The possible values of
33440 this option are the same as for @code{-var-set-format}
33441 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33442 the current display format will be used. The current display format
33443 can be changed using the @code{-var-set-format} command.
33449 Note that one must invoke @code{-var-list-children} for a variable
33450 before the value of a child variable can be evaluated.
33452 @subheading The @code{-var-assign} Command
33453 @findex -var-assign
33455 @subsubheading Synopsis
33458 -var-assign @var{name} @var{expression}
33461 Assigns the value of @var{expression} to the variable object specified
33462 by @var{name}. The object must be @samp{editable}. If the variable's
33463 value is altered by the assign, the variable will show up in any
33464 subsequent @code{-var-update} list.
33466 @subsubheading Example
33474 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33478 @subheading The @code{-var-update} Command
33479 @findex -var-update
33481 @subsubheading Synopsis
33484 -var-update [@var{print-values}] @{@var{name} | "*"@}
33487 Reevaluate the expressions corresponding to the variable object
33488 @var{name} and all its direct and indirect children, and return the
33489 list of variable objects whose values have changed; @var{name} must
33490 be a root variable object. Here, ``changed'' means that the result of
33491 @code{-var-evaluate-expression} before and after the
33492 @code{-var-update} is different. If @samp{*} is used as the variable
33493 object names, all existing variable objects are updated, except
33494 for frozen ones (@pxref{-var-set-frozen}). The option
33495 @var{print-values} determines whether both names and values, or just
33496 names are printed. The possible values of this option are the same
33497 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33498 recommended to use the @samp{--all-values} option, to reduce the
33499 number of MI commands needed on each program stop.
33501 With the @samp{*} parameter, if a variable object is bound to a
33502 currently running thread, it will not be updated, without any
33505 If @code{-var-set-update-range} was previously used on a varobj, then
33506 only the selected range of children will be reported.
33508 @code{-var-update} reports all the changed varobjs in a tuple named
33511 Each item in the change list is itself a tuple holding:
33515 The name of the varobj.
33518 If values were requested for this update, then this field will be
33519 present and will hold the value of the varobj.
33522 @anchor{-var-update}
33523 This field is a string which may take one of three values:
33527 The variable object's current value is valid.
33530 The variable object does not currently hold a valid value but it may
33531 hold one in the future if its associated expression comes back into
33535 The variable object no longer holds a valid value.
33536 This can occur when the executable file being debugged has changed,
33537 either through recompilation or by using the @value{GDBN} @code{file}
33538 command. The front end should normally choose to delete these variable
33542 In the future new values may be added to this list so the front should
33543 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33546 This is only present if the varobj is still valid. If the type
33547 changed, then this will be the string @samp{true}; otherwise it will
33550 When a varobj's type changes, its children are also likely to have
33551 become incorrect. Therefore, the varobj's children are automatically
33552 deleted when this attribute is @samp{true}. Also, the varobj's update
33553 range, when set using the @code{-var-set-update-range} command, is
33557 If the varobj's type changed, then this field will be present and will
33560 @item new_num_children
33561 For a dynamic varobj, if the number of children changed, or if the
33562 type changed, this will be the new number of children.
33564 The @samp{numchild} field in other varobj responses is generally not
33565 valid for a dynamic varobj -- it will show the number of children that
33566 @value{GDBN} knows about, but because dynamic varobjs lazily
33567 instantiate their children, this will not reflect the number of
33568 children which may be available.
33570 The @samp{new_num_children} attribute only reports changes to the
33571 number of children known by @value{GDBN}. This is the only way to
33572 detect whether an update has removed children (which necessarily can
33573 only happen at the end of the update range).
33576 The display hint, if any.
33579 This is an integer value, which will be 1 if there are more children
33580 available outside the varobj's update range.
33583 This attribute will be present and have the value @samp{1} if the
33584 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33585 then this attribute will not be present.
33588 If new children were added to a dynamic varobj within the selected
33589 update range (as set by @code{-var-set-update-range}), then they will
33590 be listed in this attribute.
33593 @subsubheading Example
33600 -var-update --all-values var1
33601 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33602 type_changed="false"@}]
33606 @subheading The @code{-var-set-frozen} Command
33607 @findex -var-set-frozen
33608 @anchor{-var-set-frozen}
33610 @subsubheading Synopsis
33613 -var-set-frozen @var{name} @var{flag}
33616 Set the frozenness flag on the variable object @var{name}. The
33617 @var{flag} parameter should be either @samp{1} to make the variable
33618 frozen or @samp{0} to make it unfrozen. If a variable object is
33619 frozen, then neither itself, nor any of its children, are
33620 implicitly updated by @code{-var-update} of
33621 a parent variable or by @code{-var-update *}. Only
33622 @code{-var-update} of the variable itself will update its value and
33623 values of its children. After a variable object is unfrozen, it is
33624 implicitly updated by all subsequent @code{-var-update} operations.
33625 Unfreezing a variable does not update it, only subsequent
33626 @code{-var-update} does.
33628 @subsubheading Example
33632 -var-set-frozen V 1
33637 @subheading The @code{-var-set-update-range} command
33638 @findex -var-set-update-range
33639 @anchor{-var-set-update-range}
33641 @subsubheading Synopsis
33644 -var-set-update-range @var{name} @var{from} @var{to}
33647 Set the range of children to be returned by future invocations of
33648 @code{-var-update}.
33650 @var{from} and @var{to} indicate the range of children to report. If
33651 @var{from} or @var{to} is less than zero, the range is reset and all
33652 children will be reported. Otherwise, children starting at @var{from}
33653 (zero-based) and up to and excluding @var{to} will be reported.
33655 @subsubheading Example
33659 -var-set-update-range V 1 2
33663 @subheading The @code{-var-set-visualizer} command
33664 @findex -var-set-visualizer
33665 @anchor{-var-set-visualizer}
33667 @subsubheading Synopsis
33670 -var-set-visualizer @var{name} @var{visualizer}
33673 Set a visualizer for the variable object @var{name}.
33675 @var{visualizer} is the visualizer to use. The special value
33676 @samp{None} means to disable any visualizer in use.
33678 If not @samp{None}, @var{visualizer} must be a Python expression.
33679 This expression must evaluate to a callable object which accepts a
33680 single argument. @value{GDBN} will call this object with the value of
33681 the varobj @var{name} as an argument (this is done so that the same
33682 Python pretty-printing code can be used for both the CLI and MI).
33683 When called, this object must return an object which conforms to the
33684 pretty-printing interface (@pxref{Pretty Printing API}).
33686 The pre-defined function @code{gdb.default_visualizer} may be used to
33687 select a visualizer by following the built-in process
33688 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33689 a varobj is created, and so ordinarily is not needed.
33691 This feature is only available if Python support is enabled. The MI
33692 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33693 can be used to check this.
33695 @subsubheading Example
33697 Resetting the visualizer:
33701 -var-set-visualizer V None
33705 Reselecting the default (type-based) visualizer:
33709 -var-set-visualizer V gdb.default_visualizer
33713 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33714 can be used to instantiate this class for a varobj:
33718 -var-set-visualizer V "lambda val: SomeClass()"
33722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33723 @node GDB/MI Data Manipulation
33724 @section @sc{gdb/mi} Data Manipulation
33726 @cindex data manipulation, in @sc{gdb/mi}
33727 @cindex @sc{gdb/mi}, data manipulation
33728 This section describes the @sc{gdb/mi} commands that manipulate data:
33729 examine memory and registers, evaluate expressions, etc.
33731 For details about what an addressable memory unit is,
33732 @pxref{addressable memory unit}.
33734 @c REMOVED FROM THE INTERFACE.
33735 @c @subheading -data-assign
33736 @c Change the value of a program variable. Plenty of side effects.
33737 @c @subsubheading GDB Command
33739 @c @subsubheading Example
33742 @subheading The @code{-data-disassemble} Command
33743 @findex -data-disassemble
33745 @subsubheading Synopsis
33749 [ -s @var{start-addr} -e @var{end-addr} ]
33750 | [ -a @var{addr} ]
33751 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33759 @item @var{start-addr}
33760 is the beginning address (or @code{$pc})
33761 @item @var{end-addr}
33764 is an address anywhere within (or the name of) the function to
33765 disassemble. If an address is specified, the whole function
33766 surrounding that address will be disassembled. If a name is
33767 specified, the whole function with that name will be disassembled.
33768 @item @var{filename}
33769 is the name of the file to disassemble
33770 @item @var{linenum}
33771 is the line number to disassemble around
33773 is the number of disassembly lines to be produced. If it is -1,
33774 the whole function will be disassembled, in case no @var{end-addr} is
33775 specified. If @var{end-addr} is specified as a non-zero value, and
33776 @var{lines} is lower than the number of disassembly lines between
33777 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33778 displayed; if @var{lines} is higher than the number of lines between
33779 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33784 @item 0 disassembly only
33785 @item 1 mixed source and disassembly (deprecated)
33786 @item 2 disassembly with raw opcodes
33787 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33788 @item 4 mixed source and disassembly
33789 @item 5 mixed source and disassembly with raw opcodes
33792 Modes 1 and 3 are deprecated. The output is ``source centric''
33793 which hasn't proved useful in practice.
33794 @xref{Machine Code}, for a discussion of the difference between
33795 @code{/m} and @code{/s} output of the @code{disassemble} command.
33798 @subsubheading Result
33800 The result of the @code{-data-disassemble} command will be a list named
33801 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33802 used with the @code{-data-disassemble} command.
33804 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33809 The address at which this instruction was disassembled.
33812 The name of the function this instruction is within.
33815 The decimal offset in bytes from the start of @samp{func-name}.
33818 The text disassembly for this @samp{address}.
33821 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33822 bytes for the @samp{inst} field.
33826 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33827 @samp{src_and_asm_line}, each of which has the following fields:
33831 The line number within @samp{file}.
33834 The file name from the compilation unit. This might be an absolute
33835 file name or a relative file name depending on the compile command
33839 Absolute file name of @samp{file}. It is converted to a canonical form
33840 using the source file search path
33841 (@pxref{Source Path, ,Specifying Source Directories})
33842 and after resolving all the symbolic links.
33844 If the source file is not found this field will contain the path as
33845 present in the debug information.
33847 @item line_asm_insn
33848 This is a list of tuples containing the disassembly for @samp{line} in
33849 @samp{file}. The fields of each tuple are the same as for
33850 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33851 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33856 Note that whatever included in the @samp{inst} field, is not
33857 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33860 @subsubheading @value{GDBN} Command
33862 The corresponding @value{GDBN} command is @samp{disassemble}.
33864 @subsubheading Example
33866 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33870 -data-disassemble -s $pc -e "$pc + 20" -- 0
33873 @{address="0x000107c0",func-name="main",offset="4",
33874 inst="mov 2, %o0"@},
33875 @{address="0x000107c4",func-name="main",offset="8",
33876 inst="sethi %hi(0x11800), %o2"@},
33877 @{address="0x000107c8",func-name="main",offset="12",
33878 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33879 @{address="0x000107cc",func-name="main",offset="16",
33880 inst="sethi %hi(0x11800), %o2"@},
33881 @{address="0x000107d0",func-name="main",offset="20",
33882 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33886 Disassemble the whole @code{main} function. Line 32 is part of
33890 -data-disassemble -f basics.c -l 32 -- 0
33892 @{address="0x000107bc",func-name="main",offset="0",
33893 inst="save %sp, -112, %sp"@},
33894 @{address="0x000107c0",func-name="main",offset="4",
33895 inst="mov 2, %o0"@},
33896 @{address="0x000107c4",func-name="main",offset="8",
33897 inst="sethi %hi(0x11800), %o2"@},
33899 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33900 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33904 Disassemble 3 instructions from the start of @code{main}:
33908 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33910 @{address="0x000107bc",func-name="main",offset="0",
33911 inst="save %sp, -112, %sp"@},
33912 @{address="0x000107c0",func-name="main",offset="4",
33913 inst="mov 2, %o0"@},
33914 @{address="0x000107c4",func-name="main",offset="8",
33915 inst="sethi %hi(0x11800), %o2"@}]
33919 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33923 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33925 src_and_asm_line=@{line="31",
33926 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33927 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33928 line_asm_insn=[@{address="0x000107bc",
33929 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33930 src_and_asm_line=@{line="32",
33931 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33932 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33933 line_asm_insn=[@{address="0x000107c0",
33934 func-name="main",offset="4",inst="mov 2, %o0"@},
33935 @{address="0x000107c4",func-name="main",offset="8",
33936 inst="sethi %hi(0x11800), %o2"@}]@}]
33941 @subheading The @code{-data-evaluate-expression} Command
33942 @findex -data-evaluate-expression
33944 @subsubheading Synopsis
33947 -data-evaluate-expression @var{expr}
33950 Evaluate @var{expr} as an expression. The expression could contain an
33951 inferior function call. The function call will execute synchronously.
33952 If the expression contains spaces, it must be enclosed in double quotes.
33954 @subsubheading @value{GDBN} Command
33956 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33957 @samp{call}. In @code{gdbtk} only, there's a corresponding
33958 @samp{gdb_eval} command.
33960 @subsubheading Example
33962 In the following example, the numbers that precede the commands are the
33963 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33964 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33968 211-data-evaluate-expression A
33971 311-data-evaluate-expression &A
33972 311^done,value="0xefffeb7c"
33974 411-data-evaluate-expression A+3
33977 511-data-evaluate-expression "A + 3"
33983 @subheading The @code{-data-list-changed-registers} Command
33984 @findex -data-list-changed-registers
33986 @subsubheading Synopsis
33989 -data-list-changed-registers
33992 Display a list of the registers that have changed.
33994 @subsubheading @value{GDBN} Command
33996 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33997 has the corresponding command @samp{gdb_changed_register_list}.
33999 @subsubheading Example
34001 On a PPC MBX board:
34009 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34010 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34011 line="5",arch="powerpc"@}
34013 -data-list-changed-registers
34014 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34015 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34016 "24","25","26","27","28","30","31","64","65","66","67","69"]
34021 @subheading The @code{-data-list-register-names} Command
34022 @findex -data-list-register-names
34024 @subsubheading Synopsis
34027 -data-list-register-names [ ( @var{regno} )+ ]
34030 Show a list of register names for the current target. If no arguments
34031 are given, it shows a list of the names of all the registers. If
34032 integer numbers are given as arguments, it will print a list of the
34033 names of the registers corresponding to the arguments. To ensure
34034 consistency between a register name and its number, the output list may
34035 include empty register names.
34037 @subsubheading @value{GDBN} Command
34039 @value{GDBN} does not have a command which corresponds to
34040 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34041 corresponding command @samp{gdb_regnames}.
34043 @subsubheading Example
34045 For the PPC MBX board:
34048 -data-list-register-names
34049 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34050 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34051 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34052 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34053 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34054 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34055 "", "pc","ps","cr","lr","ctr","xer"]
34057 -data-list-register-names 1 2 3
34058 ^done,register-names=["r1","r2","r3"]
34062 @subheading The @code{-data-list-register-values} Command
34063 @findex -data-list-register-values
34065 @subsubheading Synopsis
34068 -data-list-register-values
34069 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34072 Display the registers' contents. The format according to which the
34073 registers' contents are to be returned is given by @var{fmt}, followed
34074 by an optional list of numbers specifying the registers to display. A
34075 missing list of numbers indicates that the contents of all the
34076 registers must be returned. The @code{--skip-unavailable} option
34077 indicates that only the available registers are to be returned.
34079 Allowed formats for @var{fmt} are:
34096 @subsubheading @value{GDBN} Command
34098 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34099 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34101 @subsubheading Example
34103 For a PPC MBX board (note: line breaks are for readability only, they
34104 don't appear in the actual output):
34108 -data-list-register-values r 64 65
34109 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34110 @{number="65",value="0x00029002"@}]
34112 -data-list-register-values x
34113 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34114 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34115 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34116 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34117 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34118 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34119 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34120 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34121 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34122 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34123 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34124 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34125 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34126 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34127 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34128 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34129 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34130 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34131 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34132 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34133 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34134 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34135 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34136 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34137 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34138 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34139 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34140 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34141 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34142 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34143 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34144 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34145 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34146 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34147 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34148 @{number="69",value="0x20002b03"@}]
34153 @subheading The @code{-data-read-memory} Command
34154 @findex -data-read-memory
34156 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34158 @subsubheading Synopsis
34161 -data-read-memory [ -o @var{byte-offset} ]
34162 @var{address} @var{word-format} @var{word-size}
34163 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34170 @item @var{address}
34171 An expression specifying the address of the first memory word to be
34172 read. Complex expressions containing embedded white space should be
34173 quoted using the C convention.
34175 @item @var{word-format}
34176 The format to be used to print the memory words. The notation is the
34177 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34180 @item @var{word-size}
34181 The size of each memory word in bytes.
34183 @item @var{nr-rows}
34184 The number of rows in the output table.
34186 @item @var{nr-cols}
34187 The number of columns in the output table.
34190 If present, indicates that each row should include an @sc{ascii} dump. The
34191 value of @var{aschar} is used as a padding character when a byte is not a
34192 member of the printable @sc{ascii} character set (printable @sc{ascii}
34193 characters are those whose code is between 32 and 126, inclusively).
34195 @item @var{byte-offset}
34196 An offset to add to the @var{address} before fetching memory.
34199 This command displays memory contents as a table of @var{nr-rows} by
34200 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34201 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34202 (returned as @samp{total-bytes}). Should less than the requested number
34203 of bytes be returned by the target, the missing words are identified
34204 using @samp{N/A}. The number of bytes read from the target is returned
34205 in @samp{nr-bytes} and the starting address used to read memory in
34208 The address of the next/previous row or page is available in
34209 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34212 @subsubheading @value{GDBN} Command
34214 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34215 @samp{gdb_get_mem} memory read command.
34217 @subsubheading Example
34219 Read six bytes of memory starting at @code{bytes+6} but then offset by
34220 @code{-6} bytes. Format as three rows of two columns. One byte per
34221 word. Display each word in hex.
34225 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34226 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34227 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34228 prev-page="0x0000138a",memory=[
34229 @{addr="0x00001390",data=["0x00","0x01"]@},
34230 @{addr="0x00001392",data=["0x02","0x03"]@},
34231 @{addr="0x00001394",data=["0x04","0x05"]@}]
34235 Read two bytes of memory starting at address @code{shorts + 64} and
34236 display as a single word formatted in decimal.
34240 5-data-read-memory shorts+64 d 2 1 1
34241 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34242 next-row="0x00001512",prev-row="0x0000150e",
34243 next-page="0x00001512",prev-page="0x0000150e",memory=[
34244 @{addr="0x00001510",data=["128"]@}]
34248 Read thirty two bytes of memory starting at @code{bytes+16} and format
34249 as eight rows of four columns. Include a string encoding with @samp{x}
34250 used as the non-printable character.
34254 4-data-read-memory bytes+16 x 1 8 4 x
34255 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34256 next-row="0x000013c0",prev-row="0x0000139c",
34257 next-page="0x000013c0",prev-page="0x00001380",memory=[
34258 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34259 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34260 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34261 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34262 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34263 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34264 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34265 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34269 @subheading The @code{-data-read-memory-bytes} Command
34270 @findex -data-read-memory-bytes
34272 @subsubheading Synopsis
34275 -data-read-memory-bytes [ -o @var{offset} ]
34276 @var{address} @var{count}
34283 @item @var{address}
34284 An expression specifying the address of the first addressable memory unit
34285 to be read. Complex expressions containing embedded white space should be
34286 quoted using the C convention.
34289 The number of addressable memory units to read. This should be an integer
34293 The offset relative to @var{address} at which to start reading. This
34294 should be an integer literal. This option is provided so that a frontend
34295 is not required to first evaluate address and then perform address
34296 arithmetics itself.
34300 This command attempts to read all accessible memory regions in the
34301 specified range. First, all regions marked as unreadable in the memory
34302 map (if one is defined) will be skipped. @xref{Memory Region
34303 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34304 regions. For each one, if reading full region results in an errors,
34305 @value{GDBN} will try to read a subset of the region.
34307 In general, every single memory unit in the region may be readable or not,
34308 and the only way to read every readable unit is to try a read at
34309 every address, which is not practical. Therefore, @value{GDBN} will
34310 attempt to read all accessible memory units at either beginning or the end
34311 of the region, using a binary division scheme. This heuristic works
34312 well for reading across a memory map boundary. Note that if a region
34313 has a readable range that is neither at the beginning or the end,
34314 @value{GDBN} will not read it.
34316 The result record (@pxref{GDB/MI Result Records}) that is output of
34317 the command includes a field named @samp{memory} whose content is a
34318 list of tuples. Each tuple represent a successfully read memory block
34319 and has the following fields:
34323 The start address of the memory block, as hexadecimal literal.
34326 The end address of the memory block, as hexadecimal literal.
34329 The offset of the memory block, as hexadecimal literal, relative to
34330 the start address passed to @code{-data-read-memory-bytes}.
34333 The contents of the memory block, in hex.
34339 @subsubheading @value{GDBN} Command
34341 The corresponding @value{GDBN} command is @samp{x}.
34343 @subsubheading Example
34347 -data-read-memory-bytes &a 10
34348 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34350 contents="01000000020000000300"@}]
34355 @subheading The @code{-data-write-memory-bytes} Command
34356 @findex -data-write-memory-bytes
34358 @subsubheading Synopsis
34361 -data-write-memory-bytes @var{address} @var{contents}
34362 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34369 @item @var{address}
34370 An expression specifying the address of the first addressable memory unit
34371 to be written. Complex expressions containing embedded white space should
34372 be quoted using the C convention.
34374 @item @var{contents}
34375 The hex-encoded data to write. It is an error if @var{contents} does
34376 not represent an integral number of addressable memory units.
34379 Optional argument indicating the number of addressable memory units to be
34380 written. If @var{count} is greater than @var{contents}' length,
34381 @value{GDBN} will repeatedly write @var{contents} until it fills
34382 @var{count} memory units.
34386 @subsubheading @value{GDBN} Command
34388 There's no corresponding @value{GDBN} command.
34390 @subsubheading Example
34394 -data-write-memory-bytes &a "aabbccdd"
34401 -data-write-memory-bytes &a "aabbccdd" 16e
34406 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34407 @node GDB/MI Tracepoint Commands
34408 @section @sc{gdb/mi} Tracepoint Commands
34410 The commands defined in this section implement MI support for
34411 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34413 @subheading The @code{-trace-find} Command
34414 @findex -trace-find
34416 @subsubheading Synopsis
34419 -trace-find @var{mode} [@var{parameters}@dots{}]
34422 Find a trace frame using criteria defined by @var{mode} and
34423 @var{parameters}. The following table lists permissible
34424 modes and their parameters. For details of operation, see @ref{tfind}.
34429 No parameters are required. Stops examining trace frames.
34432 An integer is required as parameter. Selects tracepoint frame with
34435 @item tracepoint-number
34436 An integer is required as parameter. Finds next
34437 trace frame that corresponds to tracepoint with the specified number.
34440 An address is required as parameter. Finds
34441 next trace frame that corresponds to any tracepoint at the specified
34444 @item pc-inside-range
34445 Two addresses are required as parameters. Finds next trace
34446 frame that corresponds to a tracepoint at an address inside the
34447 specified range. Both bounds are considered to be inside the range.
34449 @item pc-outside-range
34450 Two addresses are required as parameters. Finds
34451 next trace frame that corresponds to a tracepoint at an address outside
34452 the specified range. Both bounds are considered to be inside the range.
34455 Line specification is required as parameter. @xref{Specify Location}.
34456 Finds next trace frame that corresponds to a tracepoint at
34457 the specified location.
34461 If @samp{none} was passed as @var{mode}, the response does not
34462 have fields. Otherwise, the response may have the following fields:
34466 This field has either @samp{0} or @samp{1} as the value, depending
34467 on whether a matching tracepoint was found.
34470 The index of the found traceframe. This field is present iff
34471 the @samp{found} field has value of @samp{1}.
34474 The index of the found tracepoint. This field is present iff
34475 the @samp{found} field has value of @samp{1}.
34478 The information about the frame corresponding to the found trace
34479 frame. This field is present only if a trace frame was found.
34480 @xref{GDB/MI Frame Information}, for description of this field.
34484 @subsubheading @value{GDBN} Command
34486 The corresponding @value{GDBN} command is @samp{tfind}.
34488 @subheading -trace-define-variable
34489 @findex -trace-define-variable
34491 @subsubheading Synopsis
34494 -trace-define-variable @var{name} [ @var{value} ]
34497 Create trace variable @var{name} if it does not exist. If
34498 @var{value} is specified, sets the initial value of the specified
34499 trace variable to that value. Note that the @var{name} should start
34500 with the @samp{$} character.
34502 @subsubheading @value{GDBN} Command
34504 The corresponding @value{GDBN} command is @samp{tvariable}.
34506 @subheading The @code{-trace-frame-collected} Command
34507 @findex -trace-frame-collected
34509 @subsubheading Synopsis
34512 -trace-frame-collected
34513 [--var-print-values @var{var_pval}]
34514 [--comp-print-values @var{comp_pval}]
34515 [--registers-format @var{regformat}]
34516 [--memory-contents]
34519 This command returns the set of collected objects, register names,
34520 trace state variable names, memory ranges and computed expressions
34521 that have been collected at a particular trace frame. The optional
34522 parameters to the command affect the output format in different ways.
34523 See the output description table below for more details.
34525 The reported names can be used in the normal manner to create
34526 varobjs and inspect the objects themselves. The items returned by
34527 this command are categorized so that it is clear which is a variable,
34528 which is a register, which is a trace state variable, which is a
34529 memory range and which is a computed expression.
34531 For instance, if the actions were
34533 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34534 collect *(int*)0xaf02bef0@@40
34538 the object collected in its entirety would be @code{myVar}. The
34539 object @code{myArray} would be partially collected, because only the
34540 element at index @code{myIndex} would be collected. The remaining
34541 objects would be computed expressions.
34543 An example output would be:
34547 -trace-frame-collected
34549 explicit-variables=[@{name="myVar",value="1"@}],
34550 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34551 @{name="myObj.field",value="0"@},
34552 @{name="myPtr->field",value="1"@},
34553 @{name="myCount + 2",value="3"@},
34554 @{name="$tvar1 + 1",value="43970027"@}],
34555 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34556 @{number="1",value="0x0"@},
34557 @{number="2",value="0x4"@},
34559 @{number="125",value="0x0"@}],
34560 tvars=[@{name="$tvar1",current="43970026"@}],
34561 memory=[@{address="0x0000000000602264",length="4"@},
34562 @{address="0x0000000000615bc0",length="4"@}]
34569 @item explicit-variables
34570 The set of objects that have been collected in their entirety (as
34571 opposed to collecting just a few elements of an array or a few struct
34572 members). For each object, its name and value are printed.
34573 The @code{--var-print-values} option affects how or whether the value
34574 field is output. If @var{var_pval} is 0, then print only the names;
34575 if it is 1, print also their values; and if it is 2, print the name,
34576 type and value for simple data types, and the name and type for
34577 arrays, structures and unions.
34579 @item computed-expressions
34580 The set of computed expressions that have been collected at the
34581 current trace frame. The @code{--comp-print-values} option affects
34582 this set like the @code{--var-print-values} option affects the
34583 @code{explicit-variables} set. See above.
34586 The registers that have been collected at the current trace frame.
34587 For each register collected, the name and current value are returned.
34588 The value is formatted according to the @code{--registers-format}
34589 option. See the @command{-data-list-register-values} command for a
34590 list of the allowed formats. The default is @samp{x}.
34593 The trace state variables that have been collected at the current
34594 trace frame. For each trace state variable collected, the name and
34595 current value are returned.
34598 The set of memory ranges that have been collected at the current trace
34599 frame. Its content is a list of tuples. Each tuple represents a
34600 collected memory range and has the following fields:
34604 The start address of the memory range, as hexadecimal literal.
34607 The length of the memory range, as decimal literal.
34610 The contents of the memory block, in hex. This field is only present
34611 if the @code{--memory-contents} option is specified.
34617 @subsubheading @value{GDBN} Command
34619 There is no corresponding @value{GDBN} command.
34621 @subsubheading Example
34623 @subheading -trace-list-variables
34624 @findex -trace-list-variables
34626 @subsubheading Synopsis
34629 -trace-list-variables
34632 Return a table of all defined trace variables. Each element of the
34633 table has the following fields:
34637 The name of the trace variable. This field is always present.
34640 The initial value. This is a 64-bit signed integer. This
34641 field is always present.
34644 The value the trace variable has at the moment. This is a 64-bit
34645 signed integer. This field is absent iff current value is
34646 not defined, for example if the trace was never run, or is
34651 @subsubheading @value{GDBN} Command
34653 The corresponding @value{GDBN} command is @samp{tvariables}.
34655 @subsubheading Example
34659 -trace-list-variables
34660 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34661 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34662 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34663 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34664 body=[variable=@{name="$trace_timestamp",initial="0"@}
34665 variable=@{name="$foo",initial="10",current="15"@}]@}
34669 @subheading -trace-save
34670 @findex -trace-save
34672 @subsubheading Synopsis
34675 -trace-save [ -r ] [ -ctf ] @var{filename}
34678 Saves the collected trace data to @var{filename}. Without the
34679 @samp{-r} option, the data is downloaded from the target and saved
34680 in a local file. With the @samp{-r} option the target is asked
34681 to perform the save.
34683 By default, this command will save the trace in the tfile format. You can
34684 supply the optional @samp{-ctf} argument to save it the CTF format. See
34685 @ref{Trace Files} for more information about CTF.
34687 @subsubheading @value{GDBN} Command
34689 The corresponding @value{GDBN} command is @samp{tsave}.
34692 @subheading -trace-start
34693 @findex -trace-start
34695 @subsubheading Synopsis
34701 Starts a tracing experiment. The result of this command does not
34704 @subsubheading @value{GDBN} Command
34706 The corresponding @value{GDBN} command is @samp{tstart}.
34708 @subheading -trace-status
34709 @findex -trace-status
34711 @subsubheading Synopsis
34717 Obtains the status of a tracing experiment. The result may include
34718 the following fields:
34723 May have a value of either @samp{0}, when no tracing operations are
34724 supported, @samp{1}, when all tracing operations are supported, or
34725 @samp{file} when examining trace file. In the latter case, examining
34726 of trace frame is possible but new tracing experiement cannot be
34727 started. This field is always present.
34730 May have a value of either @samp{0} or @samp{1} depending on whether
34731 tracing experiement is in progress on target. This field is present
34732 if @samp{supported} field is not @samp{0}.
34735 Report the reason why the tracing was stopped last time. This field
34736 may be absent iff tracing was never stopped on target yet. The
34737 value of @samp{request} means the tracing was stopped as result of
34738 the @code{-trace-stop} command. The value of @samp{overflow} means
34739 the tracing buffer is full. The value of @samp{disconnection} means
34740 tracing was automatically stopped when @value{GDBN} has disconnected.
34741 The value of @samp{passcount} means tracing was stopped when a
34742 tracepoint was passed a maximal number of times for that tracepoint.
34743 This field is present if @samp{supported} field is not @samp{0}.
34745 @item stopping-tracepoint
34746 The number of tracepoint whose passcount as exceeded. This field is
34747 present iff the @samp{stop-reason} field has the value of
34751 @itemx frames-created
34752 The @samp{frames} field is a count of the total number of trace frames
34753 in the trace buffer, while @samp{frames-created} is the total created
34754 during the run, including ones that were discarded, such as when a
34755 circular trace buffer filled up. Both fields are optional.
34759 These fields tell the current size of the tracing buffer and the
34760 remaining space. These fields are optional.
34763 The value of the circular trace buffer flag. @code{1} means that the
34764 trace buffer is circular and old trace frames will be discarded if
34765 necessary to make room, @code{0} means that the trace buffer is linear
34769 The value of the disconnected tracing flag. @code{1} means that
34770 tracing will continue after @value{GDBN} disconnects, @code{0} means
34771 that the trace run will stop.
34774 The filename of the trace file being examined. This field is
34775 optional, and only present when examining a trace file.
34779 @subsubheading @value{GDBN} Command
34781 The corresponding @value{GDBN} command is @samp{tstatus}.
34783 @subheading -trace-stop
34784 @findex -trace-stop
34786 @subsubheading Synopsis
34792 Stops a tracing experiment. The result of this command has the same
34793 fields as @code{-trace-status}, except that the @samp{supported} and
34794 @samp{running} fields are not output.
34796 @subsubheading @value{GDBN} Command
34798 The corresponding @value{GDBN} command is @samp{tstop}.
34801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34802 @node GDB/MI Symbol Query
34803 @section @sc{gdb/mi} Symbol Query Commands
34807 @subheading The @code{-symbol-info-address} Command
34808 @findex -symbol-info-address
34810 @subsubheading Synopsis
34813 -symbol-info-address @var{symbol}
34816 Describe where @var{symbol} is stored.
34818 @subsubheading @value{GDBN} Command
34820 The corresponding @value{GDBN} command is @samp{info address}.
34822 @subsubheading Example
34826 @subheading The @code{-symbol-info-file} Command
34827 @findex -symbol-info-file
34829 @subsubheading Synopsis
34835 Show the file for the symbol.
34837 @subsubheading @value{GDBN} Command
34839 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34840 @samp{gdb_find_file}.
34842 @subsubheading Example
34846 @subheading The @code{-symbol-info-functions} Command
34847 @findex -symbol-info-functions
34848 @anchor{-symbol-info-functions}
34850 @subsubheading Synopsis
34853 -symbol-info-functions [--include-nondebug]
34854 [--type @var{type_regexp}]
34855 [--name @var{name_regexp}]
34856 [--max-results @var{limit}]
34860 Return a list containing the names and types for all global functions
34861 taken from the debug information. The functions are grouped by source
34862 file, and shown with the line number on which each function is
34865 The @code{--include-nondebug} option causes the output to include
34866 code symbols from the symbol table.
34868 The options @code{--type} and @code{--name} allow the symbols returned
34869 to be filtered based on either the name of the function, or the type
34870 signature of the function.
34872 The option @code{--max-results} restricts the command to return no
34873 more than @var{limit} results. If exactly @var{limit} results are
34874 returned then there might be additional results available if a higher
34877 @subsubheading @value{GDBN} Command
34879 The corresponding @value{GDBN} command is @samp{info functions}.
34881 @subsubheading Example
34885 -symbol-info-functions
34888 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34889 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34890 symbols=[@{line="36", name="f4", type="void (int *)",
34891 description="void f4(int *);"@},
34892 @{line="42", name="main", type="int ()",
34893 description="int main();"@},
34894 @{line="30", name="f1", type="my_int_t (int, int)",
34895 description="static my_int_t f1(int, int);"@}]@},
34896 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34897 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34898 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34899 description="float f2(another_float_t);"@},
34900 @{line="39", name="f3", type="int (another_int_t)",
34901 description="int f3(another_int_t);"@},
34902 @{line="27", name="f1", type="another_float_t (int)",
34903 description="static another_float_t f1(int);"@}]@}]@}
34907 -symbol-info-functions --name f1
34910 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34911 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34912 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
34913 description="static my_int_t f1(int, int);"@}]@},
34914 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34915 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34916 symbols=[@{line="27", name="f1", type="another_float_t (int)",
34917 description="static another_float_t f1(int);"@}]@}]@}
34921 -symbol-info-functions --type void
34924 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34925 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34926 symbols=[@{line="36", name="f4", type="void (int *)",
34927 description="void f4(int *);"@}]@}]@}
34931 -symbol-info-functions --include-nondebug
34934 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34935 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34936 symbols=[@{line="36", name="f4", type="void (int *)",
34937 description="void f4(int *);"@},
34938 @{line="42", name="main", type="int ()",
34939 description="int main();"@},
34940 @{line="30", name="f1", type="my_int_t (int, int)",
34941 description="static my_int_t f1(int, int);"@}]@},
34942 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34943 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34944 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34945 description="float f2(another_float_t);"@},
34946 @{line="39", name="f3", type="int (another_int_t)",
34947 description="int f3(another_int_t);"@},
34948 @{line="27", name="f1", type="another_float_t (int)",
34949 description="static another_float_t f1(int);"@}]@}],
34951 [@{address="0x0000000000400398",name="_init"@},
34952 @{address="0x00000000004003b0",name="_start"@},
34958 @subheading The @code{-symbol-info-module-functions} Command
34959 @findex -symbol-info-module-functions
34960 @anchor{-symbol-info-module-functions}
34962 @subsubheading Synopsis
34965 -symbol-info-module-functions [--module @var{module_regexp}]
34966 [--name @var{name_regexp}]
34967 [--type @var{type_regexp}]
34971 Return a list containing the names of all known functions within all
34972 know Fortran modules. The functions are grouped by source file and
34973 containing module, and shown with the line number on which each
34974 function is defined.
34976 The option @code{--module} only returns results for modules matching
34977 @var{module_regexp}. The option @code{--name} only returns functions
34978 whose name matches @var{name_regexp}, and @code{--type} only returns
34979 functions whose type matches @var{type_regexp}.
34981 @subsubheading @value{GDBN} Command
34983 The corresponding @value{GDBN} command is @samp{info module functions}.
34985 @subsubheading Example
34990 -symbol-info-module-functions
34993 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34994 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34995 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
34996 description="void mod1::check_all(void);"@}]@}]@},
34998 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34999 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35000 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35001 description="void mod2::check_var_i(void);"@}]@}]@},
35003 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35004 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35005 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35006 description="void mod3::check_all(void);"@},
35007 @{line="27",name="mod3::check_mod2",type="void (void)",
35008 description="void mod3::check_mod2(void);"@}]@}]@},
35009 @{module="modmany",
35010 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35011 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35012 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35013 description="void modmany::check_some(void);"@}]@}]@},
35015 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35016 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35017 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35018 description="void moduse::check_all(void);"@},
35019 @{line="49",name="moduse::check_var_x",type="void (void)",
35020 description="void moduse::check_var_x(void);"@}]@}]@}]
35024 @subheading The @code{-symbol-info-module-variables} Command
35025 @findex -symbol-info-module-variables
35026 @anchor{-symbol-info-module-variables}
35028 @subsubheading Synopsis
35031 -symbol-info-module-variables [--module @var{module_regexp}]
35032 [--name @var{name_regexp}]
35033 [--type @var{type_regexp}]
35037 Return a list containing the names of all known variables within all
35038 know Fortran modules. The variables are grouped by source file and
35039 containing module, and shown with the line number on which each
35040 variable is defined.
35042 The option @code{--module} only returns results for modules matching
35043 @var{module_regexp}. The option @code{--name} only returns variables
35044 whose name matches @var{name_regexp}, and @code{--type} only returns
35045 variables whose type matches @var{type_regexp}.
35047 @subsubheading @value{GDBN} Command
35049 The corresponding @value{GDBN} command is @samp{info module variables}.
35051 @subsubheading Example
35056 -symbol-info-module-variables
35059 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35060 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35061 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35062 description="integer(kind=4) mod1::var_const;"@},
35063 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35064 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35066 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35067 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35068 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35069 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35071 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35072 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35073 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35074 description="integer(kind=4) mod3::mod1;"@},
35075 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35076 description="integer(kind=4) mod3::mod2;"@},
35077 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35078 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35079 @{module="modmany",
35080 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35081 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35082 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35083 description="integer(kind=4) modmany::var_a;"@},
35084 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35085 description="integer(kind=4) modmany::var_b;"@},
35086 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35087 description="integer(kind=4) modmany::var_c;"@},
35088 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35089 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35091 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35092 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35093 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35094 description="integer(kind=4) moduse::var_x;"@},
35095 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35096 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35100 @subheading The @code{-symbol-info-modules} Command
35101 @findex -symbol-info-modules
35102 @anchor{-symbol-info-modules}
35104 @subsubheading Synopsis
35107 -symbol-info-modules [--name @var{name_regexp}]
35108 [--max-results @var{limit}]
35113 Return a list containing the names of all known Fortran modules. The
35114 modules are grouped by source file, and shown with the line number on
35115 which each modules is defined.
35117 The option @code{--name} allows the modules returned to be filtered
35118 based the name of the module.
35120 The option @code{--max-results} restricts the command to return no
35121 more than @var{limit} results. If exactly @var{limit} results are
35122 returned then there might be additional results available if a higher
35125 @subsubheading @value{GDBN} Command
35127 The corresponding @value{GDBN} command is @samp{info modules}.
35129 @subsubheading Example
35133 -symbol-info-modules
35136 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35137 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35138 symbols=[@{line="16",name="mod1"@},
35139 @{line="22",name="mod2"@}]@},
35140 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35141 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35142 symbols=[@{line="16",name="mod3"@},
35143 @{line="22",name="modmany"@},
35144 @{line="26",name="moduse"@}]@}]@}
35148 -symbol-info-modules --name mod[123]
35151 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35152 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35153 symbols=[@{line="16",name="mod1"@},
35154 @{line="22",name="mod2"@}]@},
35155 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35156 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35157 symbols=[@{line="16",name="mod3"@}]@}]@}
35161 @subheading The @code{-symbol-info-types} Command
35162 @findex -symbol-info-types
35163 @anchor{-symbol-info-types}
35165 @subsubheading Synopsis
35168 -symbol-info-types [--name @var{name_regexp}]
35169 [--max-results @var{limit}]
35174 Return a list of all defined types. The types are grouped by source
35175 file, and shown with the line number on which each user defined type
35176 is defined. Some base types are not defined in the source code but
35177 are added to the debug information by the compiler, for example
35178 @code{int}, @code{float}, etc.; these types do not have an associated
35181 The option @code{--name} allows the list of types returned to be
35184 The option @code{--max-results} restricts the command to return no
35185 more than @var{limit} results. If exactly @var{limit} results are
35186 returned then there might be additional results available if a higher
35189 @subsubheading @value{GDBN} Command
35191 The corresponding @value{GDBN} command is @samp{info types}.
35193 @subsubheading Example
35200 [@{filename="gdb.mi/mi-sym-info-1.c",
35201 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35202 symbols=[@{name="float"@},
35204 @{line="27",name="typedef int my_int_t;"@}]@},
35205 @{filename="gdb.mi/mi-sym-info-2.c",
35206 fullname="/project/gdb.mi/mi-sym-info-2.c",
35207 symbols=[@{line="24",name="typedef float another_float_t;"@},
35208 @{line="23",name="typedef int another_int_t;"@},
35210 @{name="int"@}]@}]@}
35214 -symbol-info-types --name _int_
35217 [@{filename="gdb.mi/mi-sym-info-1.c",
35218 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35219 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35220 @{filename="gdb.mi/mi-sym-info-2.c",
35221 fullname="/project/gdb.mi/mi-sym-info-2.c",
35222 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35226 @subheading The @code{-symbol-info-variables} Command
35227 @findex -symbol-info-variables
35228 @anchor{-symbol-info-variables}
35230 @subsubheading Synopsis
35233 -symbol-info-variables [--include-nondebug]
35234 [--type @var{type_regexp}]
35235 [--name @var{name_regexp}]
35236 [--max-results @var{limit}]
35241 Return a list containing the names and types for all global variables
35242 taken from the debug information. The variables are grouped by source
35243 file, and shown with the line number on which each variable is
35246 The @code{--include-nondebug} option causes the output to include
35247 data symbols from the symbol table.
35249 The options @code{--type} and @code{--name} allow the symbols returned
35250 to be filtered based on either the name of the variable, or the type
35253 The option @code{--max-results} restricts the command to return no
35254 more than @var{limit} results. If exactly @var{limit} results are
35255 returned then there might be additional results available if a higher
35258 @subsubheading @value{GDBN} Command
35260 The corresponding @value{GDBN} command is @samp{info variables}.
35262 @subsubheading Example
35266 -symbol-info-variables
35269 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35270 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35271 symbols=[@{line="25",name="global_f1",type="float",
35272 description="static float global_f1;"@},
35273 @{line="24",name="global_i1",type="int",
35274 description="static int global_i1;"@}]@},
35275 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35276 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35277 symbols=[@{line="21",name="global_f2",type="int",
35278 description="int global_f2;"@},
35279 @{line="20",name="global_i2",type="int",
35280 description="int global_i2;"@},
35281 @{line="19",name="global_f1",type="float",
35282 description="static float global_f1;"@},
35283 @{line="18",name="global_i1",type="int",
35284 description="static int global_i1;"@}]@}]@}
35288 -symbol-info-variables --name f1
35291 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35292 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35293 symbols=[@{line="25",name="global_f1",type="float",
35294 description="static float global_f1;"@}]@},
35295 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35296 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35297 symbols=[@{line="19",name="global_f1",type="float",
35298 description="static float global_f1;"@}]@}]@}
35302 -symbol-info-variables --type float
35305 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35306 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35307 symbols=[@{line="25",name="global_f1",type="float",
35308 description="static float global_f1;"@}]@},
35309 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35310 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35311 symbols=[@{line="19",name="global_f1",type="float",
35312 description="static float global_f1;"@}]@}]@}
35316 -symbol-info-variables --include-nondebug
35319 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35320 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35321 symbols=[@{line="25",name="global_f1",type="float",
35322 description="static float global_f1;"@},
35323 @{line="24",name="global_i1",type="int",
35324 description="static int global_i1;"@}]@},
35325 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35326 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35327 symbols=[@{line="21",name="global_f2",type="int",
35328 description="int global_f2;"@},
35329 @{line="20",name="global_i2",type="int",
35330 description="int global_i2;"@},
35331 @{line="19",name="global_f1",type="float",
35332 description="static float global_f1;"@},
35333 @{line="18",name="global_i1",type="int",
35334 description="static int global_i1;"@}]@}],
35336 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35337 @{address="0x00000000004005d8",name="__dso_handle"@}
35344 @subheading The @code{-symbol-info-line} Command
35345 @findex -symbol-info-line
35347 @subsubheading Synopsis
35353 Show the core addresses of the code for a source line.
35355 @subsubheading @value{GDBN} Command
35357 The corresponding @value{GDBN} command is @samp{info line}.
35358 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35360 @subsubheading Example
35364 @subheading The @code{-symbol-info-symbol} Command
35365 @findex -symbol-info-symbol
35367 @subsubheading Synopsis
35370 -symbol-info-symbol @var{addr}
35373 Describe what symbol is at location @var{addr}.
35375 @subsubheading @value{GDBN} Command
35377 The corresponding @value{GDBN} command is @samp{info symbol}.
35379 @subsubheading Example
35383 @subheading The @code{-symbol-list-functions} Command
35384 @findex -symbol-list-functions
35386 @subsubheading Synopsis
35389 -symbol-list-functions
35392 List the functions in the executable.
35394 @subsubheading @value{GDBN} Command
35396 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35397 @samp{gdb_search} in @code{gdbtk}.
35399 @subsubheading Example
35404 @subheading The @code{-symbol-list-lines} Command
35405 @findex -symbol-list-lines
35407 @subsubheading Synopsis
35410 -symbol-list-lines @var{filename}
35413 Print the list of lines that contain code and their associated program
35414 addresses for the given source filename. The entries are sorted in
35415 ascending PC order.
35417 @subsubheading @value{GDBN} Command
35419 There is no corresponding @value{GDBN} command.
35421 @subsubheading Example
35424 -symbol-list-lines basics.c
35425 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35431 @subheading The @code{-symbol-list-types} Command
35432 @findex -symbol-list-types
35434 @subsubheading Synopsis
35440 List all the type names.
35442 @subsubheading @value{GDBN} Command
35444 The corresponding commands are @samp{info types} in @value{GDBN},
35445 @samp{gdb_search} in @code{gdbtk}.
35447 @subsubheading Example
35451 @subheading The @code{-symbol-list-variables} Command
35452 @findex -symbol-list-variables
35454 @subsubheading Synopsis
35457 -symbol-list-variables
35460 List all the global and static variable names.
35462 @subsubheading @value{GDBN} Command
35464 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35466 @subsubheading Example
35470 @subheading The @code{-symbol-locate} Command
35471 @findex -symbol-locate
35473 @subsubheading Synopsis
35479 @subsubheading @value{GDBN} Command
35481 @samp{gdb_loc} in @code{gdbtk}.
35483 @subsubheading Example
35487 @subheading The @code{-symbol-type} Command
35488 @findex -symbol-type
35490 @subsubheading Synopsis
35493 -symbol-type @var{variable}
35496 Show type of @var{variable}.
35498 @subsubheading @value{GDBN} Command
35500 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35501 @samp{gdb_obj_variable}.
35503 @subsubheading Example
35508 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35509 @node GDB/MI File Commands
35510 @section @sc{gdb/mi} File Commands
35512 This section describes the GDB/MI commands to specify executable file names
35513 and to read in and obtain symbol table information.
35515 @subheading The @code{-file-exec-and-symbols} Command
35516 @findex -file-exec-and-symbols
35518 @subsubheading Synopsis
35521 -file-exec-and-symbols @var{file}
35524 Specify the executable file to be debugged. This file is the one from
35525 which the symbol table is also read. If no file is specified, the
35526 command clears the executable and symbol information. If breakpoints
35527 are set when using this command with no arguments, @value{GDBN} will produce
35528 error messages. Otherwise, no output is produced, except a completion
35531 @subsubheading @value{GDBN} Command
35533 The corresponding @value{GDBN} command is @samp{file}.
35535 @subsubheading Example
35539 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35545 @subheading The @code{-file-exec-file} Command
35546 @findex -file-exec-file
35548 @subsubheading Synopsis
35551 -file-exec-file @var{file}
35554 Specify the executable file to be debugged. Unlike
35555 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35556 from this file. If used without argument, @value{GDBN} clears the information
35557 about the executable file. No output is produced, except a completion
35560 @subsubheading @value{GDBN} Command
35562 The corresponding @value{GDBN} command is @samp{exec-file}.
35564 @subsubheading Example
35568 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35575 @subheading The @code{-file-list-exec-sections} Command
35576 @findex -file-list-exec-sections
35578 @subsubheading Synopsis
35581 -file-list-exec-sections
35584 List the sections of the current executable file.
35586 @subsubheading @value{GDBN} Command
35588 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35589 information as this command. @code{gdbtk} has a corresponding command
35590 @samp{gdb_load_info}.
35592 @subsubheading Example
35597 @subheading The @code{-file-list-exec-source-file} Command
35598 @findex -file-list-exec-source-file
35600 @subsubheading Synopsis
35603 -file-list-exec-source-file
35606 List the line number, the current source file, and the absolute path
35607 to the current source file for the current executable. The macro
35608 information field has a value of @samp{1} or @samp{0} depending on
35609 whether or not the file includes preprocessor macro information.
35611 @subsubheading @value{GDBN} Command
35613 The @value{GDBN} equivalent is @samp{info source}
35615 @subsubheading Example
35619 123-file-list-exec-source-file
35620 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35625 @subheading The @code{-file-list-exec-source-files} Command
35626 @kindex info sources
35627 @findex -file-list-exec-source-files
35629 @subsubheading Synopsis
35632 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
35633 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
35635 @r{[} @var{regexp} @r{]}
35638 This command returns information about the source files @value{GDBN}
35639 knows about, it will output both the filename and fullname (absolute
35640 file name) of a source file, though the fullname can be elided if this
35641 information is not known to @value{GDBN}.
35643 With no arguments this command returns a list of source files. Each
35644 source file is represented by a tuple with the fields; @var{file},
35645 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
35646 display name for the file, while @var{fullname} is the absolute name
35647 of the file. The @var{fullname} field can be elided if the absolute
35648 name of the source file can't be computed. The field
35649 @var{debug-fully-read} will be a string, either @code{true} or
35650 @code{false}. When @code{true}, this indicates the full debug
35651 information for the compilation unit describing this file has been
35652 read in. When @code{false}, the full debug information has not yet
35653 been read in. While reading in the full debug information it is
35654 possible that @value{GDBN} could become aware of additional source
35657 The optional @var{regexp} can be used to filter the list of source
35658 files returned. The @var{regexp} will be matched against the full
35659 source file name. The matching is case-sensitive, except on operating
35660 systems that have case-insensitive filesystem (e.g.,
35661 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
35662 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
35663 @var{regexp} starts with @samp{-}).
35665 If @code{--dirname} is provided, then @var{regexp} is matched only
35666 against the directory name of each source file. If @code{--basename}
35667 is provided, then @var{regexp} is matched against the basename of each
35668 source file. Only one of @code{--dirname} or @code{--basename} may be
35669 given, and if either is given then @var{regexp} is required.
35671 If @code{--group-by-objfile} is used then the format of the results is
35672 changed. The results will now be a list of tuples, with each tuple
35673 representing an object file (executable or shared library) loaded into
35674 @value{GDBN}. The fields of these tuples are; @var{filename},
35675 @var{debug-info}, and @var{sources}. The @var{filename} is the
35676 absolute name of the object file, @var{debug-info} is a string with
35677 one of the following values:
35681 This object file has no debug information.
35682 @item partially-read
35683 This object file has debug information, but it is not fully read in
35684 yet. When it is read in later, GDB might become aware of additional
35687 This object file has debug information, and this information is fully
35688 read into GDB. The list of source files is complete.
35691 The @var{sources} is a list or tuples, with each tuple describing a
35692 single source file with the same fields as described previously. The
35693 @var{sources} list can be empty for object files that have no debug
35696 @subsubheading @value{GDBN} Command
35698 The @value{GDBN} equivalent is @samp{info sources}.
35699 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35701 @subsubheading Example
35704 -file-list-exec-source-files
35705 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
35706 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
35707 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
35709 -file-list-exec-source-files
35710 ^done,files=[@{file="test.c",
35711 fullname="/tmp/info-sources/test.c",
35712 debug-fully-read="true"@},
35713 @{file="/usr/include/stdc-predef.h",
35714 fullname="/usr/include/stdc-predef.h",
35715 debug-fully-read="true"@},
35717 fullname="/tmp/info-sources/header.h",
35718 debug-fully-read="true"@},
35720 fullname="/tmp/info-sources/helper.c",
35721 debug-fully-read="true"@}]
35723 -file-list-exec-source-files -- \\.c
35724 ^done,files=[@{file="test.c",
35725 fullname="/tmp/info-sources/test.c",
35726 debug-fully-read="true"@},
35728 fullname="/tmp/info-sources/helper.c",
35729 debug-fully-read="true"@}]
35731 -file-list-exec-source-files --group-by-objfile
35732 ^done,files=[@{filename="/tmp/info-sources/test.x",
35733 debug-info="fully-read",
35734 sources=[@{file="test.c",
35735 fullname="/tmp/info-sources/test.c",
35736 debug-fully-read="true"@},
35737 @{file="/usr/include/stdc-predef.h",
35738 fullname="/usr/include/stdc-predef.h",
35739 debug-fully-read="true"@},
35741 fullname="/tmp/info-sources/header.h",
35742 debug-fully-read="true"@}]@},
35743 @{filename="/lib64/ld-linux-x86-64.so.2",
35746 @{filename="system-supplied DSO at 0x7ffff7fcf000",
35749 @{filename="/tmp/info-sources/libhelper.so",
35750 debug-info="fully-read",
35751 sources=[@{file="helper.c",
35752 fullname="/tmp/info-sources/helper.c",
35753 debug-fully-read="true"@},
35754 @{file="/usr/include/stdc-predef.h",
35755 fullname="/usr/include/stdc-predef.h",
35756 debug-fully-read="true"@},
35758 fullname="/tmp/info-sources/header.h",
35759 debug-fully-read="true"@}]@},
35760 @{filename="/lib64/libc.so.6",
35765 @subheading The @code{-file-list-shared-libraries} Command
35766 @findex -file-list-shared-libraries
35768 @subsubheading Synopsis
35771 -file-list-shared-libraries [ @var{regexp} ]
35774 List the shared libraries in the program.
35775 With a regular expression @var{regexp}, only those libraries whose
35776 names match @var{regexp} are listed.
35778 @subsubheading @value{GDBN} Command
35780 The corresponding @value{GDBN} command is @samp{info shared}. The fields
35781 have a similar meaning to the @code{=library-loaded} notification.
35782 The @code{ranges} field specifies the multiple segments belonging to this
35783 library. Each range has the following fields:
35787 The address defining the inclusive lower bound of the segment.
35789 The address defining the exclusive upper bound of the segment.
35792 @subsubheading Example
35795 -file-list-exec-source-files
35796 ^done,shared-libraries=[
35797 @{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"@}]@},
35798 @{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"@}]@}]
35804 @subheading The @code{-file-list-symbol-files} Command
35805 @findex -file-list-symbol-files
35807 @subsubheading Synopsis
35810 -file-list-symbol-files
35815 @subsubheading @value{GDBN} Command
35817 The corresponding @value{GDBN} command is @samp{info file} (part of it).
35819 @subsubheading Example
35824 @subheading The @code{-file-symbol-file} Command
35825 @findex -file-symbol-file
35827 @subsubheading Synopsis
35830 -file-symbol-file @var{file}
35833 Read symbol table info from the specified @var{file} argument. When
35834 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35835 produced, except for a completion notification.
35837 @subsubheading @value{GDBN} Command
35839 The corresponding @value{GDBN} command is @samp{symbol-file}.
35841 @subsubheading Example
35845 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35852 @node GDB/MI Memory Overlay Commands
35853 @section @sc{gdb/mi} Memory Overlay Commands
35855 The memory overlay commands are not implemented.
35857 @c @subheading -overlay-auto
35859 @c @subheading -overlay-list-mapping-state
35861 @c @subheading -overlay-list-overlays
35863 @c @subheading -overlay-map
35865 @c @subheading -overlay-off
35867 @c @subheading -overlay-on
35869 @c @subheading -overlay-unmap
35871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35872 @node GDB/MI Signal Handling Commands
35873 @section @sc{gdb/mi} Signal Handling Commands
35875 Signal handling commands are not implemented.
35877 @c @subheading -signal-handle
35879 @c @subheading -signal-list-handle-actions
35881 @c @subheading -signal-list-signal-types
35885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35886 @node GDB/MI Target Manipulation
35887 @section @sc{gdb/mi} Target Manipulation Commands
35890 @subheading The @code{-target-attach} Command
35891 @findex -target-attach
35893 @subsubheading Synopsis
35896 -target-attach @var{pid} | @var{gid} | @var{file}
35899 Attach to a process @var{pid} or a file @var{file} outside of
35900 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
35901 group, the id previously returned by
35902 @samp{-list-thread-groups --available} must be used.
35904 @subsubheading @value{GDBN} Command
35906 The corresponding @value{GDBN} command is @samp{attach}.
35908 @subsubheading Example
35912 =thread-created,id="1"
35913 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
35919 @subheading The @code{-target-compare-sections} Command
35920 @findex -target-compare-sections
35922 @subsubheading Synopsis
35925 -target-compare-sections [ @var{section} ]
35928 Compare data of section @var{section} on target to the exec file.
35929 Without the argument, all sections are compared.
35931 @subsubheading @value{GDBN} Command
35933 The @value{GDBN} equivalent is @samp{compare-sections}.
35935 @subsubheading Example
35940 @subheading The @code{-target-detach} Command
35941 @findex -target-detach
35943 @subsubheading Synopsis
35946 -target-detach [ @var{pid} | @var{gid} ]
35949 Detach from the remote target which normally resumes its execution.
35950 If either @var{pid} or @var{gid} is specified, detaches from either
35951 the specified process, or specified thread group. There's no output.
35953 @subsubheading @value{GDBN} Command
35955 The corresponding @value{GDBN} command is @samp{detach}.
35957 @subsubheading Example
35967 @subheading The @code{-target-disconnect} Command
35968 @findex -target-disconnect
35970 @subsubheading Synopsis
35976 Disconnect from the remote target. There's no output and the target is
35977 generally not resumed.
35979 @subsubheading @value{GDBN} Command
35981 The corresponding @value{GDBN} command is @samp{disconnect}.
35983 @subsubheading Example
35993 @subheading The @code{-target-download} Command
35994 @findex -target-download
35996 @subsubheading Synopsis
36002 Loads the executable onto the remote target.
36003 It prints out an update message every half second, which includes the fields:
36007 The name of the section.
36009 The size of what has been sent so far for that section.
36011 The size of the section.
36013 The total size of what was sent so far (the current and the previous sections).
36015 The size of the overall executable to download.
36019 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36020 @sc{gdb/mi} Output Syntax}).
36022 In addition, it prints the name and size of the sections, as they are
36023 downloaded. These messages include the following fields:
36027 The name of the section.
36029 The size of the section.
36031 The size of the overall executable to download.
36035 At the end, a summary is printed.
36037 @subsubheading @value{GDBN} Command
36039 The corresponding @value{GDBN} command is @samp{load}.
36041 @subsubheading Example
36043 Note: each status message appears on a single line. Here the messages
36044 have been broken down so that they can fit onto a page.
36049 +download,@{section=".text",section-size="6668",total-size="9880"@}
36050 +download,@{section=".text",section-sent="512",section-size="6668",
36051 total-sent="512",total-size="9880"@}
36052 +download,@{section=".text",section-sent="1024",section-size="6668",
36053 total-sent="1024",total-size="9880"@}
36054 +download,@{section=".text",section-sent="1536",section-size="6668",
36055 total-sent="1536",total-size="9880"@}
36056 +download,@{section=".text",section-sent="2048",section-size="6668",
36057 total-sent="2048",total-size="9880"@}
36058 +download,@{section=".text",section-sent="2560",section-size="6668",
36059 total-sent="2560",total-size="9880"@}
36060 +download,@{section=".text",section-sent="3072",section-size="6668",
36061 total-sent="3072",total-size="9880"@}
36062 +download,@{section=".text",section-sent="3584",section-size="6668",
36063 total-sent="3584",total-size="9880"@}
36064 +download,@{section=".text",section-sent="4096",section-size="6668",
36065 total-sent="4096",total-size="9880"@}
36066 +download,@{section=".text",section-sent="4608",section-size="6668",
36067 total-sent="4608",total-size="9880"@}
36068 +download,@{section=".text",section-sent="5120",section-size="6668",
36069 total-sent="5120",total-size="9880"@}
36070 +download,@{section=".text",section-sent="5632",section-size="6668",
36071 total-sent="5632",total-size="9880"@}
36072 +download,@{section=".text",section-sent="6144",section-size="6668",
36073 total-sent="6144",total-size="9880"@}
36074 +download,@{section=".text",section-sent="6656",section-size="6668",
36075 total-sent="6656",total-size="9880"@}
36076 +download,@{section=".init",section-size="28",total-size="9880"@}
36077 +download,@{section=".fini",section-size="28",total-size="9880"@}
36078 +download,@{section=".data",section-size="3156",total-size="9880"@}
36079 +download,@{section=".data",section-sent="512",section-size="3156",
36080 total-sent="7236",total-size="9880"@}
36081 +download,@{section=".data",section-sent="1024",section-size="3156",
36082 total-sent="7748",total-size="9880"@}
36083 +download,@{section=".data",section-sent="1536",section-size="3156",
36084 total-sent="8260",total-size="9880"@}
36085 +download,@{section=".data",section-sent="2048",section-size="3156",
36086 total-sent="8772",total-size="9880"@}
36087 +download,@{section=".data",section-sent="2560",section-size="3156",
36088 total-sent="9284",total-size="9880"@}
36089 +download,@{section=".data",section-sent="3072",section-size="3156",
36090 total-sent="9796",total-size="9880"@}
36091 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36098 @subheading The @code{-target-exec-status} Command
36099 @findex -target-exec-status
36101 @subsubheading Synopsis
36104 -target-exec-status
36107 Provide information on the state of the target (whether it is running or
36108 not, for instance).
36110 @subsubheading @value{GDBN} Command
36112 There's no equivalent @value{GDBN} command.
36114 @subsubheading Example
36118 @subheading The @code{-target-list-available-targets} Command
36119 @findex -target-list-available-targets
36121 @subsubheading Synopsis
36124 -target-list-available-targets
36127 List the possible targets to connect to.
36129 @subsubheading @value{GDBN} Command
36131 The corresponding @value{GDBN} command is @samp{help target}.
36133 @subsubheading Example
36137 @subheading The @code{-target-list-current-targets} Command
36138 @findex -target-list-current-targets
36140 @subsubheading Synopsis
36143 -target-list-current-targets
36146 Describe the current target.
36148 @subsubheading @value{GDBN} Command
36150 The corresponding information is printed by @samp{info file} (among
36153 @subsubheading Example
36157 @subheading The @code{-target-list-parameters} Command
36158 @findex -target-list-parameters
36160 @subsubheading Synopsis
36163 -target-list-parameters
36169 @subsubheading @value{GDBN} Command
36173 @subsubheading Example
36176 @subheading The @code{-target-flash-erase} Command
36177 @findex -target-flash-erase
36179 @subsubheading Synopsis
36182 -target-flash-erase
36185 Erases all known flash memory regions on the target.
36187 The corresponding @value{GDBN} command is @samp{flash-erase}.
36189 The output is a list of flash regions that have been erased, with starting
36190 addresses and memory region sizes.
36194 -target-flash-erase
36195 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36199 @subheading The @code{-target-select} Command
36200 @findex -target-select
36202 @subsubheading Synopsis
36205 -target-select @var{type} @var{parameters @dots{}}
36208 Connect @value{GDBN} to the remote target. This command takes two args:
36212 The type of target, for instance @samp{remote}, etc.
36213 @item @var{parameters}
36214 Device names, host names and the like. @xref{Target Commands, ,
36215 Commands for Managing Targets}, for more details.
36218 The output is a connection notification, followed by the address at
36219 which the target program is, in the following form:
36222 ^connected,addr="@var{address}",func="@var{function name}",
36223 args=[@var{arg list}]
36226 @subsubheading @value{GDBN} Command
36228 The corresponding @value{GDBN} command is @samp{target}.
36230 @subsubheading Example
36234 -target-select remote /dev/ttya
36235 ^connected,addr="0xfe00a300",func="??",args=[]
36239 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36240 @node GDB/MI File Transfer Commands
36241 @section @sc{gdb/mi} File Transfer Commands
36244 @subheading The @code{-target-file-put} Command
36245 @findex -target-file-put
36247 @subsubheading Synopsis
36250 -target-file-put @var{hostfile} @var{targetfile}
36253 Copy file @var{hostfile} from the host system (the machine running
36254 @value{GDBN}) to @var{targetfile} on the target system.
36256 @subsubheading @value{GDBN} Command
36258 The corresponding @value{GDBN} command is @samp{remote put}.
36260 @subsubheading Example
36264 -target-file-put localfile remotefile
36270 @subheading The @code{-target-file-get} Command
36271 @findex -target-file-get
36273 @subsubheading Synopsis
36276 -target-file-get @var{targetfile} @var{hostfile}
36279 Copy file @var{targetfile} from the target system to @var{hostfile}
36280 on the host system.
36282 @subsubheading @value{GDBN} Command
36284 The corresponding @value{GDBN} command is @samp{remote get}.
36286 @subsubheading Example
36290 -target-file-get remotefile localfile
36296 @subheading The @code{-target-file-delete} Command
36297 @findex -target-file-delete
36299 @subsubheading Synopsis
36302 -target-file-delete @var{targetfile}
36305 Delete @var{targetfile} from the target system.
36307 @subsubheading @value{GDBN} Command
36309 The corresponding @value{GDBN} command is @samp{remote delete}.
36311 @subsubheading Example
36315 -target-file-delete remotefile
36321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36322 @node GDB/MI Ada Exceptions Commands
36323 @section Ada Exceptions @sc{gdb/mi} Commands
36325 @subheading The @code{-info-ada-exceptions} Command
36326 @findex -info-ada-exceptions
36328 @subsubheading Synopsis
36331 -info-ada-exceptions [ @var{regexp}]
36334 List all Ada exceptions defined within the program being debugged.
36335 With a regular expression @var{regexp}, only those exceptions whose
36336 names match @var{regexp} are listed.
36338 @subsubheading @value{GDBN} Command
36340 The corresponding @value{GDBN} command is @samp{info exceptions}.
36342 @subsubheading Result
36344 The result is a table of Ada exceptions. The following columns are
36345 defined for each exception:
36349 The name of the exception.
36352 The address of the exception.
36356 @subsubheading Example
36359 -info-ada-exceptions aint
36360 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
36361 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
36362 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
36363 body=[@{name="constraint_error",address="0x0000000000613da0"@},
36364 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
36367 @subheading Catching Ada Exceptions
36369 The commands describing how to ask @value{GDBN} to stop when a program
36370 raises an exception are described at @ref{Ada Exception GDB/MI
36371 Catchpoint Commands}.
36374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36375 @node GDB/MI Support Commands
36376 @section @sc{gdb/mi} Support Commands
36378 Since new commands and features get regularly added to @sc{gdb/mi},
36379 some commands are available to help front-ends query the debugger
36380 about support for these capabilities. Similarly, it is also possible
36381 to query @value{GDBN} about target support of certain features.
36383 @subheading The @code{-info-gdb-mi-command} Command
36384 @cindex @code{-info-gdb-mi-command}
36385 @findex -info-gdb-mi-command
36387 @subsubheading Synopsis
36390 -info-gdb-mi-command @var{cmd_name}
36393 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
36395 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
36396 is technically not part of the command name (@pxref{GDB/MI Input
36397 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36398 for ease of use, this command also accepts the form with the leading
36401 @subsubheading @value{GDBN} Command
36403 There is no corresponding @value{GDBN} command.
36405 @subsubheading Result
36407 The result is a tuple. There is currently only one field:
36411 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36412 @code{"false"} otherwise.
36416 @subsubheading Example
36418 Here is an example where the @sc{gdb/mi} command does not exist:
36421 -info-gdb-mi-command unsupported-command
36422 ^done,command=@{exists="false"@}
36426 And here is an example where the @sc{gdb/mi} command is known
36430 -info-gdb-mi-command symbol-list-lines
36431 ^done,command=@{exists="true"@}
36434 @subheading The @code{-list-features} Command
36435 @findex -list-features
36436 @cindex supported @sc{gdb/mi} features, list
36438 Returns a list of particular features of the MI protocol that
36439 this version of gdb implements. A feature can be a command,
36440 or a new field in an output of some command, or even an
36441 important bugfix. While a frontend can sometimes detect presence
36442 of a feature at runtime, it is easier to perform detection at debugger
36445 The command returns a list of strings, with each string naming an
36446 available feature. Each returned string is just a name, it does not
36447 have any internal structure. The list of possible feature names
36453 (gdb) -list-features
36454 ^done,result=["feature1","feature2"]
36457 The current list of features is:
36460 @item frozen-varobjs
36461 Indicates support for the @code{-var-set-frozen} command, as well
36462 as possible presence of the @code{frozen} field in the output
36463 of @code{-varobj-create}.
36464 @item pending-breakpoints
36465 Indicates support for the @option{-f} option to the @code{-break-insert}
36468 Indicates Python scripting support, Python-based
36469 pretty-printing commands, and possible presence of the
36470 @samp{display_hint} field in the output of @code{-var-list-children}
36472 Indicates support for the @code{-thread-info} command.
36473 @item data-read-memory-bytes
36474 Indicates support for the @code{-data-read-memory-bytes} and the
36475 @code{-data-write-memory-bytes} commands.
36476 @item breakpoint-notifications
36477 Indicates that changes to breakpoints and breakpoints created via the
36478 CLI will be announced via async records.
36479 @item ada-task-info
36480 Indicates support for the @code{-ada-task-info} command.
36481 @item language-option
36482 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36483 option (@pxref{Context management}).
36484 @item info-gdb-mi-command
36485 Indicates support for the @code{-info-gdb-mi-command} command.
36486 @item undefined-command-error-code
36487 Indicates support for the "undefined-command" error code in error result
36488 records, produced when trying to execute an undefined @sc{gdb/mi} command
36489 (@pxref{GDB/MI Result Records}).
36490 @item exec-run-start-option
36491 Indicates that the @code{-exec-run} command supports the @option{--start}
36492 option (@pxref{GDB/MI Program Execution}).
36493 @item data-disassemble-a-option
36494 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36495 option (@pxref{GDB/MI Data Manipulation}).
36498 @subheading The @code{-list-target-features} Command
36499 @findex -list-target-features
36501 Returns a list of particular features that are supported by the
36502 target. Those features affect the permitted MI commands, but
36503 unlike the features reported by the @code{-list-features} command, the
36504 features depend on which target GDB is using at the moment. Whenever
36505 a target can change, due to commands such as @code{-target-select},
36506 @code{-target-attach} or @code{-exec-run}, the list of target features
36507 may change, and the frontend should obtain it again.
36511 (gdb) -list-target-features
36512 ^done,result=["async"]
36515 The current list of features is:
36519 Indicates that the target is capable of asynchronous command
36520 execution, which means that @value{GDBN} will accept further commands
36521 while the target is running.
36524 Indicates that the target is capable of reverse execution.
36525 @xref{Reverse Execution}, for more information.
36529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36530 @node GDB/MI Miscellaneous Commands
36531 @section Miscellaneous @sc{gdb/mi} Commands
36533 @c @subheading -gdb-complete
36535 @subheading The @code{-gdb-exit} Command
36538 @subsubheading Synopsis
36544 Exit @value{GDBN} immediately.
36546 @subsubheading @value{GDBN} Command
36548 Approximately corresponds to @samp{quit}.
36550 @subsubheading Example
36560 @subheading The @code{-exec-abort} Command
36561 @findex -exec-abort
36563 @subsubheading Synopsis
36569 Kill the inferior running program.
36571 @subsubheading @value{GDBN} Command
36573 The corresponding @value{GDBN} command is @samp{kill}.
36575 @subsubheading Example
36580 @subheading The @code{-gdb-set} Command
36583 @subsubheading Synopsis
36589 Set an internal @value{GDBN} variable.
36590 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
36592 @subsubheading @value{GDBN} Command
36594 The corresponding @value{GDBN} command is @samp{set}.
36596 @subsubheading Example
36606 @subheading The @code{-gdb-show} Command
36609 @subsubheading Synopsis
36615 Show the current value of a @value{GDBN} variable.
36617 @subsubheading @value{GDBN} Command
36619 The corresponding @value{GDBN} command is @samp{show}.
36621 @subsubheading Example
36630 @c @subheading -gdb-source
36633 @subheading The @code{-gdb-version} Command
36634 @findex -gdb-version
36636 @subsubheading Synopsis
36642 Show version information for @value{GDBN}. Used mostly in testing.
36644 @subsubheading @value{GDBN} Command
36646 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36647 default shows this information when you start an interactive session.
36649 @subsubheading Example
36651 @c This example modifies the actual output from GDB to avoid overfull
36657 ~Copyright 2000 Free Software Foundation, Inc.
36658 ~GDB is free software, covered by the GNU General Public License, and
36659 ~you are welcome to change it and/or distribute copies of it under
36660 ~ certain conditions.
36661 ~Type "show copying" to see the conditions.
36662 ~There is absolutely no warranty for GDB. Type "show warranty" for
36664 ~This GDB was configured as
36665 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36670 @subheading The @code{-list-thread-groups} Command
36671 @findex -list-thread-groups
36673 @subheading Synopsis
36676 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36679 Lists thread groups (@pxref{Thread groups}). When a single thread
36680 group is passed as the argument, lists the children of that group.
36681 When several thread group are passed, lists information about those
36682 thread groups. Without any parameters, lists information about all
36683 top-level thread groups.
36685 Normally, thread groups that are being debugged are reported.
36686 With the @samp{--available} option, @value{GDBN} reports thread groups
36687 available on the target.
36689 The output of this command may have either a @samp{threads} result or
36690 a @samp{groups} result. The @samp{thread} result has a list of tuples
36691 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
36692 Information}). The @samp{groups} result has a list of tuples as value,
36693 each tuple describing a thread group. If top-level groups are
36694 requested (that is, no parameter is passed), or when several groups
36695 are passed, the output always has a @samp{groups} result. The format
36696 of the @samp{group} result is described below.
36698 To reduce the number of roundtrips it's possible to list thread groups
36699 together with their children, by passing the @samp{--recurse} option
36700 and the recursion depth. Presently, only recursion depth of 1 is
36701 permitted. If this option is present, then every reported thread group
36702 will also include its children, either as @samp{group} or
36703 @samp{threads} field.
36705 In general, any combination of option and parameters is permitted, with
36706 the following caveats:
36710 When a single thread group is passed, the output will typically
36711 be the @samp{threads} result. Because threads may not contain
36712 anything, the @samp{recurse} option will be ignored.
36715 When the @samp{--available} option is passed, limited information may
36716 be available. In particular, the list of threads of a process might
36717 be inaccessible. Further, specifying specific thread groups might
36718 not give any performance advantage over listing all thread groups.
36719 The frontend should assume that @samp{-list-thread-groups --available}
36720 is always an expensive operation and cache the results.
36724 The @samp{groups} result is a list of tuples, where each tuple may
36725 have the following fields:
36729 Identifier of the thread group. This field is always present.
36730 The identifier is an opaque string; frontends should not try to
36731 convert it to an integer, even though it might look like one.
36734 The type of the thread group. At present, only @samp{process} is a
36738 The target-specific process identifier. This field is only present
36739 for thread groups of type @samp{process} and only if the process exists.
36742 The exit code of this group's last exited thread, formatted in octal.
36743 This field is only present for thread groups of type @samp{process} and
36744 only if the process is not running.
36747 The number of children this thread group has. This field may be
36748 absent for an available thread group.
36751 This field has a list of tuples as value, each tuple describing a
36752 thread. It may be present if the @samp{--recurse} option is
36753 specified, and it's actually possible to obtain the threads.
36756 This field is a list of integers, each identifying a core that one
36757 thread of the group is running on. This field may be absent if
36758 such information is not available.
36761 The name of the executable file that corresponds to this thread group.
36762 The field is only present for thread groups of type @samp{process},
36763 and only if there is a corresponding executable file.
36767 @subheading Example
36771 -list-thread-groups
36772 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
36773 -list-thread-groups 17
36774 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
36775 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
36776 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
36777 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
36778 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
36779 -list-thread-groups --available
36780 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
36781 -list-thread-groups --available --recurse 1
36782 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36783 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36784 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
36785 -list-thread-groups --available --recurse 1 17 18
36786 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36787 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36788 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
36791 @subheading The @code{-info-os} Command
36794 @subsubheading Synopsis
36797 -info-os [ @var{type} ]
36800 If no argument is supplied, the command returns a table of available
36801 operating-system-specific information types. If one of these types is
36802 supplied as an argument @var{type}, then the command returns a table
36803 of data of that type.
36805 The types of information available depend on the target operating
36808 @subsubheading @value{GDBN} Command
36810 The corresponding @value{GDBN} command is @samp{info os}.
36812 @subsubheading Example
36814 When run on a @sc{gnu}/Linux system, the output will look something
36820 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
36821 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
36822 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
36823 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
36824 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36826 item=@{col0="files",col1="Listing of all file descriptors",
36827 col2="File descriptors"@},
36828 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36829 col2="Kernel modules"@},
36830 item=@{col0="msg",col1="Listing of all message queues",
36831 col2="Message queues"@},
36832 item=@{col0="processes",col1="Listing of all processes",
36833 col2="Processes"@},
36834 item=@{col0="procgroups",col1="Listing of all process groups",
36835 col2="Process groups"@},
36836 item=@{col0="semaphores",col1="Listing of all semaphores",
36837 col2="Semaphores"@},
36838 item=@{col0="shm",col1="Listing of all shared-memory regions",
36839 col2="Shared-memory regions"@},
36840 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36842 item=@{col0="threads",col1="Listing of all threads",
36846 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36847 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36848 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36849 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36850 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36851 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36852 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36853 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36855 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36856 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36860 (Note that the MI output here includes a @code{"Title"} column that
36861 does not appear in command-line @code{info os}; this column is useful
36862 for MI clients that want to enumerate the types of data, such as in a
36863 popup menu, but is needless clutter on the command line, and
36864 @code{info os} omits it.)
36866 @subheading The @code{-add-inferior} Command
36867 @findex -add-inferior
36869 @subheading Synopsis
36875 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36876 inferior is not associated with any executable. Such association may
36877 be established with the @samp{-file-exec-and-symbols} command
36878 (@pxref{GDB/MI File Commands}). The command response has a single
36879 field, @samp{inferior}, whose value is the identifier of the
36880 thread group corresponding to the new inferior.
36882 @subheading Example
36887 ^done,inferior="i3"
36890 @subheading The @code{-interpreter-exec} Command
36891 @findex -interpreter-exec
36893 @subheading Synopsis
36896 -interpreter-exec @var{interpreter} @var{command}
36898 @anchor{-interpreter-exec}
36900 Execute the specified @var{command} in the given @var{interpreter}.
36902 @subheading @value{GDBN} Command
36904 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
36906 @subheading Example
36910 -interpreter-exec console "break main"
36911 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
36912 &"During symbol reading, bad structure-type format.\n"
36913 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
36918 @subheading The @code{-inferior-tty-set} Command
36919 @findex -inferior-tty-set
36921 @subheading Synopsis
36924 -inferior-tty-set /dev/pts/1
36927 Set terminal for future runs of the program being debugged.
36929 @subheading @value{GDBN} Command
36931 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
36933 @subheading Example
36937 -inferior-tty-set /dev/pts/1
36942 @subheading The @code{-inferior-tty-show} Command
36943 @findex -inferior-tty-show
36945 @subheading Synopsis
36951 Show terminal for future runs of program being debugged.
36953 @subheading @value{GDBN} Command
36955 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
36957 @subheading Example
36961 -inferior-tty-set /dev/pts/1
36965 ^done,inferior_tty_terminal="/dev/pts/1"
36969 @subheading The @code{-enable-timings} Command
36970 @findex -enable-timings
36972 @subheading Synopsis
36975 -enable-timings [yes | no]
36978 Toggle the printing of the wallclock, user and system times for an MI
36979 command as a field in its output. This command is to help frontend
36980 developers optimize the performance of their code. No argument is
36981 equivalent to @samp{yes}.
36983 @subheading @value{GDBN} Command
36987 @subheading Example
36995 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
36996 addr="0x080484ed",func="main",file="myprog.c",
36997 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
36999 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37007 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37008 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37009 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37010 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37014 @subheading The @code{-complete} Command
37017 @subheading Synopsis
37020 -complete @var{command}
37023 Show a list of completions for partially typed CLI @var{command}.
37025 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37026 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37027 because @value{GDBN} is used remotely via a SSH connection.
37031 The result consists of two or three fields:
37035 This field contains the completed @var{command}. If @var{command}
37036 has no known completions, this field is omitted.
37039 This field contains a (possibly empty) array of matches. It is always present.
37041 @item max_completions_reached
37042 This field contains @code{1} if number of known completions is above
37043 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37044 @code{0}. It is always present.
37048 @subheading @value{GDBN} Command
37050 The corresponding @value{GDBN} command is @samp{complete}.
37052 @subheading Example
37057 ^done,completion="break",
37058 matches=["break","break-range"],
37059 max_completions_reached="0"
37062 ^done,completion="b ma",
37063 matches=["b madvise","b main"],max_completions_reached="0"
37065 -complete "b push_b"
37066 ^done,completion="b push_back(",
37068 "b A::push_back(void*)",
37069 "b std::string::push_back(char)",
37070 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37071 max_completions_reached="0"
37073 -complete "nonexist"
37074 ^done,matches=[],max_completions_reached="0"
37080 @chapter @value{GDBN} Annotations
37082 This chapter describes annotations in @value{GDBN}. Annotations were
37083 designed to interface @value{GDBN} to graphical user interfaces or other
37084 similar programs which want to interact with @value{GDBN} at a
37085 relatively high level.
37087 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37091 This is Edition @value{EDITION}, @value{DATE}.
37095 * Annotations Overview:: What annotations are; the general syntax.
37096 * Server Prefix:: Issuing a command without affecting user state.
37097 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37098 * Errors:: Annotations for error messages.
37099 * Invalidation:: Some annotations describe things now invalid.
37100 * Annotations for Running::
37101 Whether the program is running, how it stopped, etc.
37102 * Source Annotations:: Annotations describing source code.
37105 @node Annotations Overview
37106 @section What is an Annotation?
37107 @cindex annotations
37109 Annotations start with a newline character, two @samp{control-z}
37110 characters, and the name of the annotation. If there is no additional
37111 information associated with this annotation, the name of the annotation
37112 is followed immediately by a newline. If there is additional
37113 information, the name of the annotation is followed by a space, the
37114 additional information, and a newline. The additional information
37115 cannot contain newline characters.
37117 Any output not beginning with a newline and two @samp{control-z}
37118 characters denotes literal output from @value{GDBN}. Currently there is
37119 no need for @value{GDBN} to output a newline followed by two
37120 @samp{control-z} characters, but if there was such a need, the
37121 annotations could be extended with an @samp{escape} annotation which
37122 means those three characters as output.
37124 The annotation @var{level}, which is specified using the
37125 @option{--annotate} command line option (@pxref{Mode Options}), controls
37126 how much information @value{GDBN} prints together with its prompt,
37127 values of expressions, source lines, and other types of output. Level 0
37128 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37129 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37130 for programs that control @value{GDBN}, and level 2 annotations have
37131 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37132 Interface, annotate, GDB's Obsolete Annotations}).
37135 @kindex set annotate
37136 @item set annotate @var{level}
37137 The @value{GDBN} command @code{set annotate} sets the level of
37138 annotations to the specified @var{level}.
37140 @item show annotate
37141 @kindex show annotate
37142 Show the current annotation level.
37145 This chapter describes level 3 annotations.
37147 A simple example of starting up @value{GDBN} with annotations is:
37150 $ @kbd{gdb --annotate=3}
37152 Copyright 2003 Free Software Foundation, Inc.
37153 GDB is free software, covered by the GNU General Public License,
37154 and you are welcome to change it and/or distribute copies of it
37155 under certain conditions.
37156 Type "show copying" to see the conditions.
37157 There is absolutely no warranty for GDB. Type "show warranty"
37159 This GDB was configured as "i386-pc-linux-gnu"
37170 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37171 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37172 denotes a @samp{control-z} character) are annotations; the rest is
37173 output from @value{GDBN}.
37175 @node Server Prefix
37176 @section The Server Prefix
37177 @cindex server prefix
37179 If you prefix a command with @samp{server } then it will not affect
37180 the command history, nor will it affect @value{GDBN}'s notion of which
37181 command to repeat if @key{RET} is pressed on a line by itself. This
37182 means that commands can be run behind a user's back by a front-end in
37183 a transparent manner.
37185 The @code{server } prefix does not affect the recording of values into
37186 the value history; to print a value without recording it into the
37187 value history, use the @code{output} command instead of the
37188 @code{print} command.
37190 Using this prefix also disables confirmation requests
37191 (@pxref{confirmation requests}).
37194 @section Annotation for @value{GDBN} Input
37196 @cindex annotations for prompts
37197 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37198 to know when to send output, when the output from a given command is
37201 Different kinds of input each have a different @dfn{input type}. Each
37202 input type has three annotations: a @code{pre-} annotation, which
37203 denotes the beginning of any prompt which is being output, a plain
37204 annotation, which denotes the end of the prompt, and then a @code{post-}
37205 annotation which denotes the end of any echo which may (or may not) be
37206 associated with the input. For example, the @code{prompt} input type
37207 features the following annotations:
37215 The input types are
37218 @findex pre-prompt annotation
37219 @findex prompt annotation
37220 @findex post-prompt annotation
37222 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37224 @findex pre-commands annotation
37225 @findex commands annotation
37226 @findex post-commands annotation
37228 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37229 command. The annotations are repeated for each command which is input.
37231 @findex pre-overload-choice annotation
37232 @findex overload-choice annotation
37233 @findex post-overload-choice annotation
37234 @item overload-choice
37235 When @value{GDBN} wants the user to select between various overloaded functions.
37237 @findex pre-query annotation
37238 @findex query annotation
37239 @findex post-query annotation
37241 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37243 @findex pre-prompt-for-continue annotation
37244 @findex prompt-for-continue annotation
37245 @findex post-prompt-for-continue annotation
37246 @item prompt-for-continue
37247 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37248 expect this to work well; instead use @code{set height 0} to disable
37249 prompting. This is because the counting of lines is buggy in the
37250 presence of annotations.
37255 @cindex annotations for errors, warnings and interrupts
37257 @findex quit annotation
37262 This annotation occurs right before @value{GDBN} responds to an interrupt.
37264 @findex error annotation
37269 This annotation occurs right before @value{GDBN} responds to an error.
37271 Quit and error annotations indicate that any annotations which @value{GDBN} was
37272 in the middle of may end abruptly. For example, if a
37273 @code{value-history-begin} annotation is followed by a @code{error}, one
37274 cannot expect to receive the matching @code{value-history-end}. One
37275 cannot expect not to receive it either, however; an error annotation
37276 does not necessarily mean that @value{GDBN} is immediately returning all the way
37279 @findex error-begin annotation
37280 A quit or error annotation may be preceded by
37286 Any output between that and the quit or error annotation is the error
37289 Warning messages are not yet annotated.
37290 @c If we want to change that, need to fix warning(), type_error(),
37291 @c range_error(), and possibly other places.
37294 @section Invalidation Notices
37296 @cindex annotations for invalidation messages
37297 The following annotations say that certain pieces of state may have
37301 @findex frames-invalid annotation
37302 @item ^Z^Zframes-invalid
37304 The frames (for example, output from the @code{backtrace} command) may
37307 @findex breakpoints-invalid annotation
37308 @item ^Z^Zbreakpoints-invalid
37310 The breakpoints may have changed. For example, the user just added or
37311 deleted a breakpoint.
37314 @node Annotations for Running
37315 @section Running the Program
37316 @cindex annotations for running programs
37318 @findex starting annotation
37319 @findex stopping annotation
37320 When the program starts executing due to a @value{GDBN} command such as
37321 @code{step} or @code{continue},
37327 is output. When the program stops,
37333 is output. Before the @code{stopped} annotation, a variety of
37334 annotations describe how the program stopped.
37337 @findex exited annotation
37338 @item ^Z^Zexited @var{exit-status}
37339 The program exited, and @var{exit-status} is the exit status (zero for
37340 successful exit, otherwise nonzero).
37342 @findex signalled annotation
37343 @findex signal-name annotation
37344 @findex signal-name-end annotation
37345 @findex signal-string annotation
37346 @findex signal-string-end annotation
37347 @item ^Z^Zsignalled
37348 The program exited with a signal. After the @code{^Z^Zsignalled}, the
37349 annotation continues:
37355 ^Z^Zsignal-name-end
37359 ^Z^Zsignal-string-end
37364 where @var{name} is the name of the signal, such as @code{SIGILL} or
37365 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
37366 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
37367 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
37368 user's benefit and have no particular format.
37370 @findex signal annotation
37372 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
37373 just saying that the program received the signal, not that it was
37374 terminated with it.
37376 @findex breakpoint annotation
37377 @item ^Z^Zbreakpoint @var{number}
37378 The program hit breakpoint number @var{number}.
37380 @findex watchpoint annotation
37381 @item ^Z^Zwatchpoint @var{number}
37382 The program hit watchpoint number @var{number}.
37385 @node Source Annotations
37386 @section Displaying Source
37387 @cindex annotations for source display
37389 @findex source annotation
37390 The following annotation is used instead of displaying source code:
37393 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
37396 where @var{filename} is an absolute file name indicating which source
37397 file, @var{line} is the line number within that file (where 1 is the
37398 first line in the file), @var{character} is the character position
37399 within the file (where 0 is the first character in the file) (for most
37400 debug formats this will necessarily point to the beginning of a line),
37401 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37402 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37403 @var{addr} is the address in the target program associated with the
37404 source which is being displayed. The @var{addr} is in the form @samp{0x}
37405 followed by one or more lowercase hex digits (note that this does not
37406 depend on the language).
37408 @node JIT Interface
37409 @chapter JIT Compilation Interface
37410 @cindex just-in-time compilation
37411 @cindex JIT compilation interface
37413 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37414 interface. A JIT compiler is a program or library that generates native
37415 executable code at runtime and executes it, usually in order to achieve good
37416 performance while maintaining platform independence.
37418 Programs that use JIT compilation are normally difficult to debug because
37419 portions of their code are generated at runtime, instead of being loaded from
37420 object files, which is where @value{GDBN} normally finds the program's symbols
37421 and debug information. In order to debug programs that use JIT compilation,
37422 @value{GDBN} has an interface that allows the program to register in-memory
37423 symbol files with @value{GDBN} at runtime.
37425 If you are using @value{GDBN} to debug a program that uses this interface, then
37426 it should work transparently so long as you have not stripped the binary. If
37427 you are developing a JIT compiler, then the interface is documented in the rest
37428 of this chapter. At this time, the only known client of this interface is the
37431 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37432 JIT compiler communicates with @value{GDBN} by writing data into a global
37433 variable and calling a function at a well-known symbol. When @value{GDBN}
37434 attaches, it reads a linked list of symbol files from the global variable to
37435 find existing code, and puts a breakpoint in the function so that it can find
37436 out about additional code.
37439 * Declarations:: Relevant C struct declarations
37440 * Registering Code:: Steps to register code
37441 * Unregistering Code:: Steps to unregister code
37442 * Custom Debug Info:: Emit debug information in a custom format
37446 @section JIT Declarations
37448 These are the relevant struct declarations that a C program should include to
37449 implement the interface:
37459 struct jit_code_entry
37461 struct jit_code_entry *next_entry;
37462 struct jit_code_entry *prev_entry;
37463 const char *symfile_addr;
37464 uint64_t symfile_size;
37467 struct jit_descriptor
37470 /* This type should be jit_actions_t, but we use uint32_t
37471 to be explicit about the bitwidth. */
37472 uint32_t action_flag;
37473 struct jit_code_entry *relevant_entry;
37474 struct jit_code_entry *first_entry;
37477 /* GDB puts a breakpoint in this function. */
37478 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37480 /* Make sure to specify the version statically, because the
37481 debugger may check the version before we can set it. */
37482 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37485 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37486 modifications to this global data properly, which can easily be done by putting
37487 a global mutex around modifications to these structures.
37489 @node Registering Code
37490 @section Registering Code
37492 To register code with @value{GDBN}, the JIT should follow this protocol:
37496 Generate an object file in memory with symbols and other desired debug
37497 information. The file must include the virtual addresses of the sections.
37500 Create a code entry for the file, which gives the start and size of the symbol
37504 Add it to the linked list in the JIT descriptor.
37507 Point the relevant_entry field of the descriptor at the entry.
37510 Set @code{action_flag} to @code{JIT_REGISTER} and call
37511 @code{__jit_debug_register_code}.
37514 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37515 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37516 new code. However, the linked list must still be maintained in order to allow
37517 @value{GDBN} to attach to a running process and still find the symbol files.
37519 @node Unregistering Code
37520 @section Unregistering Code
37522 If code is freed, then the JIT should use the following protocol:
37526 Remove the code entry corresponding to the code from the linked list.
37529 Point the @code{relevant_entry} field of the descriptor at the code entry.
37532 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
37533 @code{__jit_debug_register_code}.
37536 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
37537 and the JIT will leak the memory used for the associated symbol files.
37539 @node Custom Debug Info
37540 @section Custom Debug Info
37541 @cindex custom JIT debug info
37542 @cindex JIT debug info reader
37544 Generating debug information in platform-native file formats (like ELF
37545 or COFF) may be an overkill for JIT compilers; especially if all the
37546 debug info is used for is displaying a meaningful backtrace. The
37547 issue can be resolved by having the JIT writers decide on a debug info
37548 format and also provide a reader that parses the debug info generated
37549 by the JIT compiler. This section gives a brief overview on writing
37550 such a parser. More specific details can be found in the source file
37551 @file{gdb/jit-reader.in}, which is also installed as a header at
37552 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
37554 The reader is implemented as a shared object (so this functionality is
37555 not available on platforms which don't allow loading shared objects at
37556 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
37557 @code{jit-reader-unload} are provided, to be used to load and unload
37558 the readers from a preconfigured directory. Once loaded, the shared
37559 object is used the parse the debug information emitted by the JIT
37563 * Using JIT Debug Info Readers:: How to use supplied readers correctly
37564 * Writing JIT Debug Info Readers:: Creating a debug-info reader
37567 @node Using JIT Debug Info Readers
37568 @subsection Using JIT Debug Info Readers
37569 @kindex jit-reader-load
37570 @kindex jit-reader-unload
37572 Readers can be loaded and unloaded using the @code{jit-reader-load}
37573 and @code{jit-reader-unload} commands.
37576 @item jit-reader-load @var{reader}
37577 Load the JIT reader named @var{reader}, which is a shared
37578 object specified as either an absolute or a relative file name. In
37579 the latter case, @value{GDBN} will try to load the reader from a
37580 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
37581 system (here @var{libdir} is the system library directory, often
37582 @file{/usr/local/lib}).
37584 Only one reader can be active at a time; trying to load a second
37585 reader when one is already loaded will result in @value{GDBN}
37586 reporting an error. A new JIT reader can be loaded by first unloading
37587 the current one using @code{jit-reader-unload} and then invoking
37588 @code{jit-reader-load}.
37590 @item jit-reader-unload
37591 Unload the currently loaded JIT reader.
37595 @node Writing JIT Debug Info Readers
37596 @subsection Writing JIT Debug Info Readers
37597 @cindex writing JIT debug info readers
37599 As mentioned, a reader is essentially a shared object conforming to a
37600 certain ABI. This ABI is described in @file{jit-reader.h}.
37602 @file{jit-reader.h} defines the structures, macros and functions
37603 required to write a reader. It is installed (along with
37604 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
37605 the system include directory.
37607 Readers need to be released under a GPL compatible license. A reader
37608 can be declared as released under such a license by placing the macro
37609 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37611 The entry point for readers is the symbol @code{gdb_init_reader},
37612 which is expected to be a function with the prototype
37614 @findex gdb_init_reader
37616 extern struct gdb_reader_funcs *gdb_init_reader (void);
37619 @cindex @code{struct gdb_reader_funcs}
37621 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37622 functions. These functions are executed to read the debug info
37623 generated by the JIT compiler (@code{read}), to unwind stack frames
37624 (@code{unwind}) and to create canonical frame IDs
37625 (@code{get_frame_id}). It also has a callback that is called when the
37626 reader is being unloaded (@code{destroy}). The struct looks like this
37629 struct gdb_reader_funcs
37631 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37632 int reader_version;
37634 /* For use by the reader. */
37637 gdb_read_debug_info *read;
37638 gdb_unwind_frame *unwind;
37639 gdb_get_frame_id *get_frame_id;
37640 gdb_destroy_reader *destroy;
37644 @cindex @code{struct gdb_symbol_callbacks}
37645 @cindex @code{struct gdb_unwind_callbacks}
37647 The callbacks are provided with another set of callbacks by
37648 @value{GDBN} to do their job. For @code{read}, these callbacks are
37649 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37650 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37651 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37652 files and new symbol tables inside those object files. @code{struct
37653 gdb_unwind_callbacks} has callbacks to read registers off the current
37654 frame and to write out the values of the registers in the previous
37655 frame. Both have a callback (@code{target_read}) to read bytes off the
37656 target's address space.
37658 @node In-Process Agent
37659 @chapter In-Process Agent
37660 @cindex debugging agent
37661 The traditional debugging model is conceptually low-speed, but works fine,
37662 because most bugs can be reproduced in debugging-mode execution. However,
37663 as multi-core or many-core processors are becoming mainstream, and
37664 multi-threaded programs become more and more popular, there should be more
37665 and more bugs that only manifest themselves at normal-mode execution, for
37666 example, thread races, because debugger's interference with the program's
37667 timing may conceal the bugs. On the other hand, in some applications,
37668 it is not feasible for the debugger to interrupt the program's execution
37669 long enough for the developer to learn anything helpful about its behavior.
37670 If the program's correctness depends on its real-time behavior, delays
37671 introduced by a debugger might cause the program to fail, even when the
37672 code itself is correct. It is useful to be able to observe the program's
37673 behavior without interrupting it.
37675 Therefore, traditional debugging model is too intrusive to reproduce
37676 some bugs. In order to reduce the interference with the program, we can
37677 reduce the number of operations performed by debugger. The
37678 @dfn{In-Process Agent}, a shared library, is running within the same
37679 process with inferior, and is able to perform some debugging operations
37680 itself. As a result, debugger is only involved when necessary, and
37681 performance of debugging can be improved accordingly. Note that
37682 interference with program can be reduced but can't be removed completely,
37683 because the in-process agent will still stop or slow down the program.
37685 The in-process agent can interpret and execute Agent Expressions
37686 (@pxref{Agent Expressions}) during performing debugging operations. The
37687 agent expressions can be used for different purposes, such as collecting
37688 data in tracepoints, and condition evaluation in breakpoints.
37690 @anchor{Control Agent}
37691 You can control whether the in-process agent is used as an aid for
37692 debugging with the following commands:
37695 @kindex set agent on
37697 Causes the in-process agent to perform some operations on behalf of the
37698 debugger. Just which operations requested by the user will be done
37699 by the in-process agent depends on the its capabilities. For example,
37700 if you request to evaluate breakpoint conditions in the in-process agent,
37701 and the in-process agent has such capability as well, then breakpoint
37702 conditions will be evaluated in the in-process agent.
37704 @kindex set agent off
37705 @item set agent off
37706 Disables execution of debugging operations by the in-process agent. All
37707 of the operations will be performed by @value{GDBN}.
37711 Display the current setting of execution of debugging operations by
37712 the in-process agent.
37716 * In-Process Agent Protocol::
37719 @node In-Process Agent Protocol
37720 @section In-Process Agent Protocol
37721 @cindex in-process agent protocol
37723 The in-process agent is able to communicate with both @value{GDBN} and
37724 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37725 used for communications between @value{GDBN} or GDBserver and the IPA.
37726 In general, @value{GDBN} or GDBserver sends commands
37727 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37728 in-process agent replies back with the return result of the command, or
37729 some other information. The data sent to in-process agent is composed
37730 of primitive data types, such as 4-byte or 8-byte type, and composite
37731 types, which are called objects (@pxref{IPA Protocol Objects}).
37734 * IPA Protocol Objects::
37735 * IPA Protocol Commands::
37738 @node IPA Protocol Objects
37739 @subsection IPA Protocol Objects
37740 @cindex ipa protocol objects
37742 The commands sent to and results received from agent may contain some
37743 complex data types called @dfn{objects}.
37745 The in-process agent is running on the same machine with @value{GDBN}
37746 or GDBserver, so it doesn't have to handle as much differences between
37747 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
37748 However, there are still some differences of two ends in two processes:
37752 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
37753 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
37755 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
37756 GDBserver is compiled with one, and in-process agent is compiled with
37760 Here are the IPA Protocol Objects:
37764 agent expression object. It represents an agent expression
37765 (@pxref{Agent Expressions}).
37766 @anchor{agent expression object}
37768 tracepoint action object. It represents a tracepoint action
37769 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
37770 memory, static trace data and to evaluate expression.
37771 @anchor{tracepoint action object}
37773 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
37774 @anchor{tracepoint object}
37778 The following table describes important attributes of each IPA protocol
37781 @multitable @columnfractions .30 .20 .50
37782 @headitem Name @tab Size @tab Description
37783 @item @emph{agent expression object} @tab @tab
37784 @item length @tab 4 @tab length of bytes code
37785 @item byte code @tab @var{length} @tab contents of byte code
37786 @item @emph{tracepoint action for collecting memory} @tab @tab
37787 @item 'M' @tab 1 @tab type of tracepoint action
37788 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
37789 address of the lowest byte to collect, otherwise @var{addr} is the offset
37790 of @var{basereg} for memory collecting.
37791 @item len @tab 8 @tab length of memory for collecting
37792 @item basereg @tab 4 @tab the register number containing the starting
37793 memory address for collecting.
37794 @item @emph{tracepoint action for collecting registers} @tab @tab
37795 @item 'R' @tab 1 @tab type of tracepoint action
37796 @item @emph{tracepoint action for collecting static trace data} @tab @tab
37797 @item 'L' @tab 1 @tab type of tracepoint action
37798 @item @emph{tracepoint action for expression evaluation} @tab @tab
37799 @item 'X' @tab 1 @tab type of tracepoint action
37800 @item agent expression @tab length of @tab @ref{agent expression object}
37801 @item @emph{tracepoint object} @tab @tab
37802 @item number @tab 4 @tab number of tracepoint
37803 @item address @tab 8 @tab address of tracepoint inserted on
37804 @item type @tab 4 @tab type of tracepoint
37805 @item enabled @tab 1 @tab enable or disable of tracepoint
37806 @item step_count @tab 8 @tab step
37807 @item pass_count @tab 8 @tab pass
37808 @item numactions @tab 4 @tab number of tracepoint actions
37809 @item hit count @tab 8 @tab hit count
37810 @item trace frame usage @tab 8 @tab trace frame usage
37811 @item compiled_cond @tab 8 @tab compiled condition
37812 @item orig_size @tab 8 @tab orig size
37813 @item condition @tab 4 if condition is NULL otherwise length of
37814 @ref{agent expression object}
37815 @tab zero if condition is NULL, otherwise is
37816 @ref{agent expression object}
37817 @item actions @tab variable
37818 @tab numactions number of @ref{tracepoint action object}
37821 @node IPA Protocol Commands
37822 @subsection IPA Protocol Commands
37823 @cindex ipa protocol commands
37825 The spaces in each command are delimiters to ease reading this commands
37826 specification. They don't exist in real commands.
37830 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37831 Installs a new fast tracepoint described by @var{tracepoint_object}
37832 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37833 head of @dfn{jumppad}, which is used to jump to data collection routine
37838 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37839 @var{target_address} is address of tracepoint in the inferior.
37840 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37841 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37842 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37843 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37850 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37851 is about to kill inferiors.
37859 @item probe_marker_at:@var{address}
37860 Asks in-process agent to probe the marker at @var{address}.
37867 @item unprobe_marker_at:@var{address}
37868 Asks in-process agent to unprobe the marker at @var{address}.
37872 @chapter Reporting Bugs in @value{GDBN}
37873 @cindex bugs in @value{GDBN}
37874 @cindex reporting bugs in @value{GDBN}
37876 Your bug reports play an essential role in making @value{GDBN} reliable.
37878 Reporting a bug may help you by bringing a solution to your problem, or it
37879 may not. But in any case the principal function of a bug report is to help
37880 the entire community by making the next version of @value{GDBN} work better. Bug
37881 reports are your contribution to the maintenance of @value{GDBN}.
37883 In order for a bug report to serve its purpose, you must include the
37884 information that enables us to fix the bug.
37887 * Bug Criteria:: Have you found a bug?
37888 * Bug Reporting:: How to report bugs
37892 @section Have You Found a Bug?
37893 @cindex bug criteria
37895 If you are not sure whether you have found a bug, here are some guidelines:
37898 @cindex fatal signal
37899 @cindex debugger crash
37900 @cindex crash of debugger
37902 If the debugger gets a fatal signal, for any input whatever, that is a
37903 @value{GDBN} bug. Reliable debuggers never crash.
37905 @cindex error on valid input
37907 If @value{GDBN} produces an error message for valid input, that is a
37908 bug. (Note that if you're cross debugging, the problem may also be
37909 somewhere in the connection to the target.)
37911 @cindex invalid input
37913 If @value{GDBN} does not produce an error message for invalid input,
37914 that is a bug. However, you should note that your idea of
37915 ``invalid input'' might be our idea of ``an extension'' or ``support
37916 for traditional practice''.
37919 If you are an experienced user of debugging tools, your suggestions
37920 for improvement of @value{GDBN} are welcome in any case.
37923 @node Bug Reporting
37924 @section How to Report Bugs
37925 @cindex bug reports
37926 @cindex @value{GDBN} bugs, reporting
37928 A number of companies and individuals offer support for @sc{gnu} products.
37929 If you obtained @value{GDBN} from a support organization, we recommend you
37930 contact that organization first.
37932 You can find contact information for many support companies and
37933 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
37935 @c should add a web page ref...
37938 @ifset BUGURL_DEFAULT
37939 In any event, we also recommend that you submit bug reports for
37940 @value{GDBN}. The preferred method is to submit them directly using
37941 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
37942 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
37945 @strong{Do not send bug reports to @samp{info-gdb}, or to
37946 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
37947 not want to receive bug reports. Those that do have arranged to receive
37950 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
37951 serves as a repeater. The mailing list and the newsgroup carry exactly
37952 the same messages. Often people think of posting bug reports to the
37953 newsgroup instead of mailing them. This appears to work, but it has one
37954 problem which can be crucial: a newsgroup posting often lacks a mail
37955 path back to the sender. Thus, if we need to ask for more information,
37956 we may be unable to reach you. For this reason, it is better to send
37957 bug reports to the mailing list.
37959 @ifclear BUGURL_DEFAULT
37960 In any event, we also recommend that you submit bug reports for
37961 @value{GDBN} to @value{BUGURL}.
37965 The fundamental principle of reporting bugs usefully is this:
37966 @strong{report all the facts}. If you are not sure whether to state a
37967 fact or leave it out, state it!
37969 Often people omit facts because they think they know what causes the
37970 problem and assume that some details do not matter. Thus, you might
37971 assume that the name of the variable you use in an example does not matter.
37972 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
37973 stray memory reference which happens to fetch from the location where that
37974 name is stored in memory; perhaps, if the name were different, the contents
37975 of that location would fool the debugger into doing the right thing despite
37976 the bug. Play it safe and give a specific, complete example. That is the
37977 easiest thing for you to do, and the most helpful.
37979 Keep in mind that the purpose of a bug report is to enable us to fix the
37980 bug. It may be that the bug has been reported previously, but neither
37981 you nor we can know that unless your bug report is complete and
37984 Sometimes people give a few sketchy facts and ask, ``Does this ring a
37985 bell?'' Those bug reports are useless, and we urge everyone to
37986 @emph{refuse to respond to them} except to chide the sender to report
37989 To enable us to fix the bug, you should include all these things:
37993 The version of @value{GDBN}. @value{GDBN} announces it if you start
37994 with no arguments; you can also print it at any time using @code{show
37997 Without this, we will not know whether there is any point in looking for
37998 the bug in the current version of @value{GDBN}.
38001 The type of machine you are using, and the operating system name and
38005 The details of the @value{GDBN} build-time configuration.
38006 @value{GDBN} shows these details if you invoke it with the
38007 @option{--configuration} command-line option, or if you type
38008 @code{show configuration} at @value{GDBN}'s prompt.
38011 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38012 ``@value{GCC}--2.8.1''.
38015 What compiler (and its version) was used to compile the program you are
38016 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38017 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38018 to get this information; for other compilers, see the documentation for
38022 The command arguments you gave the compiler to compile your example and
38023 observe the bug. For example, did you use @samp{-O}? To guarantee
38024 you will not omit something important, list them all. A copy of the
38025 Makefile (or the output from make) is sufficient.
38027 If we were to try to guess the arguments, we would probably guess wrong
38028 and then we might not encounter the bug.
38031 A complete input script, and all necessary source files, that will
38035 A description of what behavior you observe that you believe is
38036 incorrect. For example, ``It gets a fatal signal.''
38038 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38039 will certainly notice it. But if the bug is incorrect output, we might
38040 not notice unless it is glaringly wrong. You might as well not give us
38041 a chance to make a mistake.
38043 Even if the problem you experience is a fatal signal, you should still
38044 say so explicitly. Suppose something strange is going on, such as, your
38045 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38046 the C library on your system. (This has happened!) Your copy might
38047 crash and ours would not. If you told us to expect a crash, then when
38048 ours fails to crash, we would know that the bug was not happening for
38049 us. If you had not told us to expect a crash, then we would not be able
38050 to draw any conclusion from our observations.
38053 @cindex recording a session script
38054 To collect all this information, you can use a session recording program
38055 such as @command{script}, which is available on many Unix systems.
38056 Just run your @value{GDBN} session inside @command{script} and then
38057 include the @file{typescript} file with your bug report.
38059 Another way to record a @value{GDBN} session is to run @value{GDBN}
38060 inside Emacs and then save the entire buffer to a file.
38063 If you wish to suggest changes to the @value{GDBN} source, send us context
38064 diffs. If you even discuss something in the @value{GDBN} source, refer to
38065 it by context, not by line number.
38067 The line numbers in our development sources will not match those in your
38068 sources. Your line numbers would convey no useful information to us.
38072 Here are some things that are not necessary:
38076 A description of the envelope of the bug.
38078 Often people who encounter a bug spend a lot of time investigating
38079 which changes to the input file will make the bug go away and which
38080 changes will not affect it.
38082 This is often time consuming and not very useful, because the way we
38083 will find the bug is by running a single example under the debugger
38084 with breakpoints, not by pure deduction from a series of examples.
38085 We recommend that you save your time for something else.
38087 Of course, if you can find a simpler example to report @emph{instead}
38088 of the original one, that is a convenience for us. Errors in the
38089 output will be easier to spot, running under the debugger will take
38090 less time, and so on.
38092 However, simplification is not vital; if you do not want to do this,
38093 report the bug anyway and send us the entire test case you used.
38096 A patch for the bug.
38098 A patch for the bug does help us if it is a good one. But do not omit
38099 the necessary information, such as the test case, on the assumption that
38100 a patch is all we need. We might see problems with your patch and decide
38101 to fix the problem another way, or we might not understand it at all.
38103 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38104 construct an example that will make the program follow a certain path
38105 through the code. If you do not send us the example, we will not be able
38106 to construct one, so we will not be able to verify that the bug is fixed.
38108 And if we cannot understand what bug you are trying to fix, or why your
38109 patch should be an improvement, we will not install it. A test case will
38110 help us to understand.
38113 A guess about what the bug is or what it depends on.
38115 Such guesses are usually wrong. Even we cannot guess right about such
38116 things without first using the debugger to find the facts.
38119 @c The readline documentation is distributed with the readline code
38120 @c and consists of the two following files:
38123 @c Use -I with makeinfo to point to the appropriate directory,
38124 @c environment var TEXINPUTS with TeX.
38125 @ifclear SYSTEM_READLINE
38126 @include rluser.texi
38127 @include hsuser.texi
38131 @appendix In Memoriam
38133 The @value{GDBN} project mourns the loss of the following long-time
38138 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38139 to Free Software in general. Outside of @value{GDBN}, he was known in
38140 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38142 @item Michael Snyder
38143 Michael was one of the Global Maintainers of the @value{GDBN} project,
38144 with contributions recorded as early as 1996, until 2011. In addition
38145 to his day to day participation, he was a large driving force behind
38146 adding Reverse Debugging to @value{GDBN}.
38149 Beyond their technical contributions to the project, they were also
38150 enjoyable members of the Free Software Community. We will miss them.
38152 @node Formatting Documentation
38153 @appendix Formatting Documentation
38155 @cindex @value{GDBN} reference card
38156 @cindex reference card
38157 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38158 for printing with PostScript or Ghostscript, in the @file{gdb}
38159 subdirectory of the main source directory@footnote{In
38160 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38161 release.}. If you can use PostScript or Ghostscript with your printer,
38162 you can print the reference card immediately with @file{refcard.ps}.
38164 The release also includes the source for the reference card. You
38165 can format it, using @TeX{}, by typing:
38171 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38172 mode on US ``letter'' size paper;
38173 that is, on a sheet 11 inches wide by 8.5 inches
38174 high. You will need to specify this form of printing as an option to
38175 your @sc{dvi} output program.
38177 @cindex documentation
38179 All the documentation for @value{GDBN} comes as part of the machine-readable
38180 distribution. The documentation is written in Texinfo format, which is
38181 a documentation system that uses a single source file to produce both
38182 on-line information and a printed manual. You can use one of the Info
38183 formatting commands to create the on-line version of the documentation
38184 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38186 @value{GDBN} includes an already formatted copy of the on-line Info
38187 version of this manual in the @file{gdb} subdirectory. The main Info
38188 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38189 subordinate files matching @samp{gdb.info*} in the same directory. If
38190 necessary, you can print out these files, or read them with any editor;
38191 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38192 Emacs or the standalone @code{info} program, available as part of the
38193 @sc{gnu} Texinfo distribution.
38195 If you want to format these Info files yourself, you need one of the
38196 Info formatting programs, such as @code{texinfo-format-buffer} or
38199 If you have @code{makeinfo} installed, and are in the top level
38200 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38201 version @value{GDBVN}), you can make the Info file by typing:
38208 If you want to typeset and print copies of this manual, you need @TeX{},
38209 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38210 Texinfo definitions file.
38212 @TeX{} is a typesetting program; it does not print files directly, but
38213 produces output files called @sc{dvi} files. To print a typeset
38214 document, you need a program to print @sc{dvi} files. If your system
38215 has @TeX{} installed, chances are it has such a program. The precise
38216 command to use depends on your system; @kbd{lpr -d} is common; another
38217 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38218 require a file name without any extension or a @samp{.dvi} extension.
38220 @TeX{} also requires a macro definitions file called
38221 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38222 written in Texinfo format. On its own, @TeX{} cannot either read or
38223 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38224 and is located in the @file{gdb-@var{version-number}/texinfo}
38227 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38228 typeset and print this manual. First switch to the @file{gdb}
38229 subdirectory of the main source directory (for example, to
38230 @file{gdb-@value{GDBVN}/gdb}) and type:
38236 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38238 @node Installing GDB
38239 @appendix Installing @value{GDBN}
38240 @cindex installation
38243 * Requirements:: Requirements for building @value{GDBN}
38244 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38245 * Separate Objdir:: Compiling @value{GDBN} in another directory
38246 * Config Names:: Specifying names for hosts and targets
38247 * Configure Options:: Summary of options for configure
38248 * System-wide configuration:: Having a system-wide init file
38252 @section Requirements for Building @value{GDBN}
38253 @cindex building @value{GDBN}, requirements for
38255 Building @value{GDBN} requires various tools and packages to be available.
38256 Other packages will be used only if they are found.
38258 @heading Tools/Packages Necessary for Building @value{GDBN}
38260 @item C@t{++}11 compiler
38261 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38262 recent C@t{++}11 compiler, e.g.@: GCC.
38265 @value{GDBN}'s build system relies on features only found in the GNU
38266 make program. Other variants of @code{make} will not work.
38268 @item GMP (The GNU Multiple Precision Arithmetic Library)
38269 @value{GDBN} now uses GMP to perform some of its arithmetics.
38270 This library may be included with your operating system distribution;
38271 if it is not, you can get the latest version from
38272 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38273 you can use the @option{--with-libgmp-prefix} option to specify
38278 @heading Tools/Packages Optional for Building @value{GDBN}
38282 @value{GDBN} can use the Expat XML parsing library. This library may be
38283 included with your operating system distribution; if it is not, you
38284 can get the latest version from @url{http://expat.sourceforge.net}.
38285 The @file{configure} script will search for this library in several
38286 standard locations; if it is installed in an unusual path, you can
38287 use the @option{--with-libexpat-prefix} option to specify its location.
38293 Remote protocol memory maps (@pxref{Memory Map Format})
38295 Target descriptions (@pxref{Target Descriptions})
38297 Remote shared library lists (@xref{Library List Format},
38298 or alternatively @pxref{Library List Format for SVR4 Targets})
38300 MS-Windows shared libraries (@pxref{Shared Libraries})
38302 Traceframe info (@pxref{Traceframe Info Format})
38304 Branch trace (@pxref{Branch Trace Format},
38305 @pxref{Branch Trace Configuration Format})
38309 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38310 default, @value{GDBN} will be compiled if the Guile libraries are
38311 installed and are found by @file{configure}. You can use the
38312 @code{--with-guile} option to request Guile, and pass either the Guile
38313 version number or the file name of the relevant @code{pkg-config}
38314 program to choose a particular version of Guile.
38317 @value{GDBN}'s features related to character sets (@pxref{Character
38318 Sets}) require a functioning @code{iconv} implementation. If you are
38319 on a GNU system, then this is provided by the GNU C Library. Some
38320 other systems also provide a working @code{iconv}.
38322 If @value{GDBN} is using the @code{iconv} program which is installed
38323 in a non-standard place, you will need to tell @value{GDBN} where to
38324 find it. This is done with @option{--with-iconv-bin} which specifies
38325 the directory that contains the @code{iconv} program. This program is
38326 run in order to make a list of the available character sets.
38328 On systems without @code{iconv}, you can install GNU Libiconv. If
38329 Libiconv is installed in a standard place, @value{GDBN} will
38330 automatically use it if it is needed. If you have previously
38331 installed Libiconv in a non-standard place, you can use the
38332 @option{--with-libiconv-prefix} option to @file{configure}.
38334 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
38335 arrange to build Libiconv if a directory named @file{libiconv} appears
38336 in the top-most source directory. If Libiconv is built this way, and
38337 if the operating system does not provide a suitable @code{iconv}
38338 implementation, then the just-built library will automatically be used
38339 by @value{GDBN}. One easy way to set this up is to download GNU
38340 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
38341 source tree, and then rename the directory holding the Libiconv source
38342 code to @samp{libiconv}.
38345 @value{GDBN} can support debugging sections that are compressed with
38346 the LZMA library. @xref{MiniDebugInfo}. If this library is not
38347 included with your operating system, you can find it in the xz package
38348 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
38349 the usual place, then the @file{configure} script will use it
38350 automatically. If it is installed in an unusual path, you can use the
38351 @option{--with-lzma-prefix} option to specify its location.
38355 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
38356 library. This library may be included with your operating system
38357 distribution; if it is not, you can get the latest version from
38358 @url{http://www.mpfr.org}. The @file{configure} script will search
38359 for this library in several standard locations; if it is installed
38360 in an unusual path, you can use the @option{--with-libmpfr-prefix}
38361 option to specify its location.
38363 GNU MPFR is used to emulate target floating-point arithmetic during
38364 expression evaluation when the target uses different floating-point
38365 formats than the host. If GNU MPFR it is not available, @value{GDBN}
38366 will fall back to using host floating-point arithmetic.
38369 @value{GDBN} can be scripted using Python language. @xref{Python}.
38370 By default, @value{GDBN} will be compiled if the Python libraries are
38371 installed and are found by @file{configure}. You can use the
38372 @code{--with-python} option to request Python, and pass either the
38373 file name of the relevant @code{python} executable, or the name of the
38374 directory in which Python is installed, to choose a particular
38375 installation of Python.
38378 @cindex compressed debug sections
38379 @value{GDBN} will use the @samp{zlib} library, if available, to read
38380 compressed debug sections. Some linkers, such as GNU gold, are capable
38381 of producing binaries with compressed debug sections. If @value{GDBN}
38382 is compiled with @samp{zlib}, it will be able to read the debug
38383 information in such binaries.
38385 The @samp{zlib} library is likely included with your operating system
38386 distribution; if it is not, you can get the latest version from
38387 @url{http://zlib.net}.
38390 @node Running Configure
38391 @section Invoking the @value{GDBN} @file{configure} Script
38392 @cindex configuring @value{GDBN}
38393 @value{GDBN} comes with a @file{configure} script that automates the process
38394 of preparing @value{GDBN} for installation; you can then use @code{make} to
38395 build the @code{gdb} program.
38397 @c irrelevant in info file; it's as current as the code it lives with.
38398 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38399 look at the @file{README} file in the sources; we may have improved the
38400 installation procedures since publishing this manual.}
38403 The @value{GDBN} distribution includes all the source code you need for
38404 @value{GDBN} in a single directory, whose name is usually composed by
38405 appending the version number to @samp{gdb}.
38407 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38408 @file{gdb-@value{GDBVN}} directory. That directory contains:
38411 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38412 script for configuring @value{GDBN} and all its supporting libraries
38414 @item gdb-@value{GDBVN}/gdb
38415 the source specific to @value{GDBN} itself
38417 @item gdb-@value{GDBVN}/bfd
38418 source for the Binary File Descriptor library
38420 @item gdb-@value{GDBVN}/include
38421 @sc{gnu} include files
38423 @item gdb-@value{GDBVN}/libiberty
38424 source for the @samp{-liberty} free software library
38426 @item gdb-@value{GDBVN}/opcodes
38427 source for the library of opcode tables and disassemblers
38429 @item gdb-@value{GDBVN}/readline
38430 source for the @sc{gnu} command-line interface
38433 There may be other subdirectories as well.
38435 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38436 from the @file{gdb-@var{version-number}} source directory, which in
38437 this example is the @file{gdb-@value{GDBVN}} directory.
38439 First switch to the @file{gdb-@var{version-number}} source directory
38440 if you are not already in it; then run @file{configure}. Pass the
38441 identifier for the platform on which @value{GDBN} will run as an
38447 cd gdb-@value{GDBVN}
38452 Running @samp{configure} and then running @code{make} builds the
38453 included supporting libraries, then @code{gdb} itself. The configured
38454 source files, and the binaries, are left in the corresponding source
38458 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38459 system does not recognize this automatically when you run a different
38460 shell, you may need to run @code{sh} on it explicitly:
38466 You should run the @file{configure} script from the top directory in the
38467 source tree, the @file{gdb-@var{version-number}} directory. If you run
38468 @file{configure} from one of the subdirectories, you will configure only
38469 that subdirectory. That is usually not what you want. In particular,
38470 if you run the first @file{configure} from the @file{gdb} subdirectory
38471 of the @file{gdb-@var{version-number}} directory, you will omit the
38472 configuration of @file{bfd}, @file{readline}, and other sibling
38473 directories of the @file{gdb} subdirectory. This leads to build errors
38474 about missing include files such as @file{bfd/bfd.h}.
38476 You can install @code{@value{GDBN}} anywhere. The best way to do this
38477 is to pass the @code{--prefix} option to @code{configure}, and then
38478 install it with @code{make install}.
38480 @node Separate Objdir
38481 @section Compiling @value{GDBN} in Another Directory
38483 If you want to run @value{GDBN} versions for several host or target machines,
38484 you need a different @code{gdb} compiled for each combination of
38485 host and target. @file{configure} is designed to make this easy by
38486 allowing you to generate each configuration in a separate subdirectory,
38487 rather than in the source directory. If your @code{make} program
38488 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38489 @code{make} in each of these directories builds the @code{gdb}
38490 program specified there.
38492 To build @code{gdb} in a separate directory, run @file{configure}
38493 with the @samp{--srcdir} option to specify where to find the source.
38494 (You also need to specify a path to find @file{configure}
38495 itself from your working directory. If the path to @file{configure}
38496 would be the same as the argument to @samp{--srcdir}, you can leave out
38497 the @samp{--srcdir} option; it is assumed.)
38499 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38500 separate directory for a Sun 4 like this:
38504 cd gdb-@value{GDBVN}
38507 ../gdb-@value{GDBVN}/configure
38512 When @file{configure} builds a configuration using a remote source
38513 directory, it creates a tree for the binaries with the same structure
38514 (and using the same names) as the tree under the source directory. In
38515 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38516 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38517 @file{gdb-sun4/gdb}.
38519 Make sure that your path to the @file{configure} script has just one
38520 instance of @file{gdb} in it. If your path to @file{configure} looks
38521 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38522 one subdirectory of @value{GDBN}, not the whole package. This leads to
38523 build errors about missing include files such as @file{bfd/bfd.h}.
38525 One popular reason to build several @value{GDBN} configurations in separate
38526 directories is to configure @value{GDBN} for cross-compiling (where
38527 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
38528 programs that run on another machine---the @dfn{target}).
38529 You specify a cross-debugging target by
38530 giving the @samp{--target=@var{target}} option to @file{configure}.
38532 When you run @code{make} to build a program or library, you must run
38533 it in a configured directory---whatever directory you were in when you
38534 called @file{configure} (or one of its subdirectories).
38536 The @code{Makefile} that @file{configure} generates in each source
38537 directory also runs recursively. If you type @code{make} in a source
38538 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
38539 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
38540 will build all the required libraries, and then build GDB.
38542 When you have multiple hosts or targets configured in separate
38543 directories, you can run @code{make} on them in parallel (for example,
38544 if they are NFS-mounted on each of the hosts); they will not interfere
38548 @section Specifying Names for Hosts and Targets
38550 The specifications used for hosts and targets in the @file{configure}
38551 script are based on a three-part naming scheme, but some short predefined
38552 aliases are also supported. The full naming scheme encodes three pieces
38553 of information in the following pattern:
38556 @var{architecture}-@var{vendor}-@var{os}
38559 For example, you can use the alias @code{sun4} as a @var{host} argument,
38560 or as the value for @var{target} in a @code{--target=@var{target}}
38561 option. The equivalent full name is @samp{sparc-sun-sunos4}.
38563 The @file{configure} script accompanying @value{GDBN} does not provide
38564 any query facility to list all supported host and target names or
38565 aliases. @file{configure} calls the Bourne shell script
38566 @code{config.sub} to map abbreviations to full names; you can read the
38567 script, if you wish, or you can use it to test your guesses on
38568 abbreviations---for example:
38571 % sh config.sub i386-linux
38573 % sh config.sub alpha-linux
38574 alpha-unknown-linux-gnu
38575 % sh config.sub hp9k700
38577 % sh config.sub sun4
38578 sparc-sun-sunos4.1.1
38579 % sh config.sub sun3
38580 m68k-sun-sunos4.1.1
38581 % sh config.sub i986v
38582 Invalid configuration `i986v': machine `i986v' not recognized
38586 @code{config.sub} is also distributed in the @value{GDBN} source
38587 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
38589 @node Configure Options
38590 @section @file{configure} Options
38592 Here is a summary of the @file{configure} options and arguments that
38593 are most often useful for building @value{GDBN}. @file{configure}
38594 also has several other options not listed here. @inforef{Running
38595 configure scripts,,autoconf.info}, for a full
38596 explanation of @file{configure}.
38599 configure @r{[}--help@r{]}
38600 @r{[}--prefix=@var{dir}@r{]}
38601 @r{[}--exec-prefix=@var{dir}@r{]}
38602 @r{[}--srcdir=@var{dirname}@r{]}
38603 @r{[}--target=@var{target}@r{]}
38607 You may introduce options with a single @samp{-} rather than
38608 @samp{--} if you prefer; but you may abbreviate option names if you use
38613 Display a quick summary of how to invoke @file{configure}.
38615 @item --prefix=@var{dir}
38616 Configure the source to install programs and files under directory
38619 @item --exec-prefix=@var{dir}
38620 Configure the source to install programs under directory
38623 @c avoid splitting the warning from the explanation:
38625 @item --srcdir=@var{dirname}
38626 Use this option to make configurations in directories separate from the
38627 @value{GDBN} source directories. Among other things, you can use this to
38628 build (or maintain) several configurations simultaneously, in separate
38629 directories. @file{configure} writes configuration-specific files in
38630 the current directory, but arranges for them to use the source in the
38631 directory @var{dirname}. @file{configure} creates directories under
38632 the working directory in parallel to the source directories below
38635 @item --target=@var{target}
38636 Configure @value{GDBN} for cross-debugging programs running on the specified
38637 @var{target}. Without this option, @value{GDBN} is configured to debug
38638 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38640 There is no convenient way to generate a list of all available
38641 targets. Also see the @code{--enable-targets} option, below.
38644 There are many other options that are specific to @value{GDBN}. This
38645 lists just the most common ones; there are some very specialized
38646 options not described here.
38649 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38650 @itemx --enable-targets=all
38651 Configure @value{GDBN} for cross-debugging programs running on the
38652 specified list of targets. The special value @samp{all} configures
38653 @value{GDBN} for debugging programs running on any target it supports.
38655 @item --with-gdb-datadir=@var{path}
38656 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
38657 here for certain supporting files or scripts. This defaults to the
38658 @file{gdb} subdirectory of @samp{datadir} (which can be set using
38661 @item --with-relocated-sources=@var{dir}
38662 Sets up the default source path substitution rule so that directory
38663 names recorded in debug information will be automatically adjusted for
38664 any directory under @var{dir}. @var{dir} should be a subdirectory of
38665 @value{GDBN}'s configured prefix, the one mentioned in the
38666 @code{--prefix} or @code{--exec-prefix} options to configure. This
38667 option is useful if GDB is supposed to be moved to a different place
38670 @item --enable-64-bit-bfd
38671 Enable 64-bit support in BFD on 32-bit hosts.
38673 @item --disable-gdbmi
38674 Build @value{GDBN} without the GDB/MI machine interface
38678 Build @value{GDBN} with the text-mode full-screen user interface
38679 (TUI). Requires a curses library (ncurses and cursesX are also
38682 @item --with-curses
38683 Use the curses library instead of the termcap library, for text-mode
38684 terminal operations.
38686 @item --with-debuginfod
38687 Build @value{GDBN} with libdebuginfod, the debuginfod client library.
38688 Used to automatically fetch source files and separate debug files from
38689 debuginfod servers using the associated executable's build ID. Enabled
38690 by default if libdebuginfod is installed and found at configure time.
38691 debuginfod is packaged with elfutils, starting with version 0.178. You
38692 can get the latest version from `https://sourceware.org/elfutils/'.
38694 @item --with-libunwind-ia64
38695 Use the libunwind library for unwinding function call stack on ia64
38696 target platforms. See http://www.nongnu.org/libunwind/index.html for
38699 @item --with-system-readline
38700 Use the readline library installed on the host, rather than the
38701 library supplied as part of @value{GDBN}. Readline 7 or newer is
38702 required; this is enforced by the build system.
38704 @item --with-system-zlib
38705 Use the zlib library installed on the host, rather than the library
38706 supplied as part of @value{GDBN}.
38709 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38710 default if libexpat is installed and found at configure time.) This
38711 library is used to read XML files supplied with @value{GDBN}. If it
38712 is unavailable, some features, such as remote protocol memory maps,
38713 target descriptions, and shared library lists, that are based on XML
38714 files, will not be available in @value{GDBN}. If your host does not
38715 have libexpat installed, you can get the latest version from
38716 `http://expat.sourceforge.net'.
38718 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38720 Build @value{GDBN} with GNU libiconv, a character set encoding
38721 conversion library. This is not done by default, as on GNU systems
38722 the @code{iconv} that is built in to the C library is sufficient. If
38723 your host does not have a working @code{iconv}, you can get the latest
38724 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38726 @value{GDBN}'s build system also supports building GNU libiconv as
38727 part of the overall build. @xref{Requirements}.
38730 Build @value{GDBN} with LZMA, a compression library. (Done by default
38731 if liblzma is installed and found at configure time.) LZMA is used by
38732 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38733 platforms using the ELF object file format. If your host does not
38734 have liblzma installed, you can get the latest version from
38735 `https://tukaani.org/xz/'.
38738 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38739 floating-point computation with correct rounding. (Done by default if
38740 GNU MPFR is installed and found at configure time.) This library is
38741 used to emulate target floating-point arithmetic during expression
38742 evaluation when the target uses different floating-point formats than
38743 the host. If GNU MPFR is not available, @value{GDBN} will fall back
38744 to using host floating-point arithmetic. If your host does not have
38745 GNU MPFR installed, you can get the latest version from
38746 `http://www.mpfr.org'.
38748 @item --with-python@r{[}=@var{python}@r{]}
38749 Build @value{GDBN} with Python scripting support. (Done by default if
38750 libpython is present and found at configure time.) Python makes
38751 @value{GDBN} scripting much more powerful than the restricted CLI
38752 scripting language. If your host does not have Python installed, you
38753 can find it on `http://www.python.org/download/'. The oldest version
38754 of Python supported by GDB is 2.6. The optional argument @var{python}
38755 is used to find the Python headers and libraries. It can be either
38756 the name of a Python executable, or the name of the directory in which
38757 Python is installed.
38759 @item --with-guile[=GUILE]'
38760 Build @value{GDBN} with GNU Guile scripting support. (Done by default
38761 if libguile is present and found at configure time.) If your host
38762 does not have Guile installed, you can find it at
38763 `https://www.gnu.org/software/guile/'. The optional argument GUILE
38764 can be a version number, which will cause @code{configure} to try to
38765 use that version of Guile; or the file name of a @code{pkg-config}
38766 executable, which will be queried to find the information needed to
38767 compile and link against Guile.
38769 @item --without-included-regex
38770 Don't use the regex library included with @value{GDBN} (as part of the
38771 libiberty library). This is the default on hosts with version 2 of
38774 @item --with-sysroot=@var{dir}
38775 Use @var{dir} as the default system root directory for libraries whose
38776 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
38777 @var{dir} can be modified at run time by using the @command{set
38778 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
38779 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
38780 default system root will be automatically adjusted if and when
38781 @value{GDBN} is moved to a different location.
38783 @item --with-system-gdbinit=@var{file}
38784 Configure @value{GDBN} to automatically load a system-wide init file.
38785 @var{file} should be an absolute file name. If @var{file} is in a
38786 directory under the configured prefix, and @value{GDBN} is moved to
38787 another location after being built, the location of the system-wide
38788 init file will be adjusted accordingly.
38790 @item --with-system-gdbinit-dir=@var{directory}
38791 Configure @value{GDBN} to automatically load init files from a
38792 system-wide directory. @var{directory} should be an absolute directory
38793 name. If @var{directory} is in a directory under the configured
38794 prefix, and @value{GDBN} is moved to another location after being
38795 built, the location of the system-wide init directory will be
38796 adjusted accordingly.
38798 @item --enable-build-warnings
38799 When building the @value{GDBN} sources, ask the compiler to warn about
38800 any code which looks even vaguely suspicious. It passes many
38801 different warning flags, depending on the exact version of the
38802 compiler you are using.
38804 @item --enable-werror
38805 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
38806 to the compiler, which will fail the compilation if the compiler
38807 outputs any warning messages.
38809 @item --enable-ubsan
38810 Enable the GCC undefined behavior sanitizer. This is disabled by
38811 default, but passing @code{--enable-ubsan=yes} or
38812 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
38813 undefined behavior sanitizer checks for C@t{++} undefined behavior.
38814 It has a performance cost, so if you are looking at @value{GDBN}'s
38815 performance, you should disable it. The undefined behavior sanitizer
38816 was first introduced in GCC 4.9.
38819 @node System-wide configuration
38820 @section System-wide configuration and settings
38821 @cindex system-wide init file
38823 @value{GDBN} can be configured to have a system-wide init file and a
38824 system-wide init file directory; this file and files in that directory
38825 (if they have a recognized file extension) will be read and executed at
38826 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
38828 Here are the corresponding configure options:
38831 @item --with-system-gdbinit=@var{file}
38832 Specify that the default location of the system-wide init file is
38834 @item --with-system-gdbinit-dir=@var{directory}
38835 Specify that the default location of the system-wide init file directory
38836 is @var{directory}.
38839 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
38840 they may be subject to relocation. Two possible cases:
38844 If the default location of this init file/directory contains @file{$prefix},
38845 it will be subject to relocation. Suppose that the configure options
38846 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38847 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38848 init file is looked for as @file{$install/etc/gdbinit} instead of
38849 @file{$prefix/etc/gdbinit}.
38852 By contrast, if the default location does not contain the prefix,
38853 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38854 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38855 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38856 wherever @value{GDBN} is installed.
38859 If the configured location of the system-wide init file (as given by the
38860 @option{--with-system-gdbinit} option at configure time) is in the
38861 data-directory (as specified by @option{--with-gdb-datadir} at configure
38862 time) or in one of its subdirectories, then @value{GDBN} will look for the
38863 system-wide init file in the directory specified by the
38864 @option{--data-directory} command-line option.
38865 Note that the system-wide init file is only read once, during @value{GDBN}
38866 initialization. If the data-directory is changed after @value{GDBN} has
38867 started with the @code{set data-directory} command, the file will not be
38870 This applies similarly to the system-wide directory specified in
38871 @option{--with-system-gdbinit-dir}.
38873 Any supported scripting language can be used for these init files, as long
38874 as the file extension matches the scripting language. To be interpreted
38875 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
38879 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
38882 @node System-wide Configuration Scripts
38883 @subsection Installed System-wide Configuration Scripts
38884 @cindex system-wide configuration scripts
38886 The @file{system-gdbinit} directory, located inside the data-directory
38887 (as specified by @option{--with-gdb-datadir} at configure time) contains
38888 a number of scripts which can be used as system-wide init files. To
38889 automatically source those scripts at startup, @value{GDBN} should be
38890 configured with @option{--with-system-gdbinit}. Otherwise, any user
38891 should be able to source them by hand as needed.
38893 The following scripts are currently available:
38896 @item @file{elinos.py}
38898 @cindex ELinOS system-wide configuration script
38899 This script is useful when debugging a program on an ELinOS target.
38900 It takes advantage of the environment variables defined in a standard
38901 ELinOS environment in order to determine the location of the system
38902 shared libraries, and then sets the @samp{solib-absolute-prefix}
38903 and @samp{solib-search-path} variables appropriately.
38905 @item @file{wrs-linux.py}
38906 @pindex wrs-linux.py
38907 @cindex Wind River Linux system-wide configuration script
38908 This script is useful when debugging a program on a target running
38909 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
38910 the host-side sysroot used by the target system.
38914 @node Maintenance Commands
38915 @appendix Maintenance Commands
38916 @cindex maintenance commands
38917 @cindex internal commands
38919 In addition to commands intended for @value{GDBN} users, @value{GDBN}
38920 includes a number of commands intended for @value{GDBN} developers,
38921 that are not documented elsewhere in this manual. These commands are
38922 provided here for reference. (For commands that turn on debugging
38923 messages, see @ref{Debugging Output}.)
38926 @kindex maint agent
38927 @kindex maint agent-eval
38928 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38929 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38930 Translate the given @var{expression} into remote agent bytecodes.
38931 This command is useful for debugging the Agent Expression mechanism
38932 (@pxref{Agent Expressions}). The @samp{agent} version produces an
38933 expression useful for data collection, such as by tracepoints, while
38934 @samp{maint agent-eval} produces an expression that evaluates directly
38935 to a result. For instance, a collection expression for @code{globa +
38936 globb} will include bytecodes to record four bytes of memory at each
38937 of the addresses of @code{globa} and @code{globb}, while discarding
38938 the result of the addition, while an evaluation expression will do the
38939 addition and return the sum.
38940 If @code{-at} is given, generate remote agent bytecode for @var{location}.
38941 If not, generate remote agent bytecode for current frame PC address.
38943 @kindex maint agent-printf
38944 @item maint agent-printf @var{format},@var{expr},...
38945 Translate the given format string and list of argument expressions
38946 into remote agent bytecodes and display them as a disassembled list.
38947 This command is useful for debugging the agent version of dynamic
38948 printf (@pxref{Dynamic Printf}).
38950 @kindex maint info breakpoints
38951 @item @anchor{maint info breakpoints}maint info breakpoints
38952 Using the same format as @samp{info breakpoints}, display both the
38953 breakpoints you've set explicitly, and those @value{GDBN} is using for
38954 internal purposes. Internal breakpoints are shown with negative
38955 breakpoint numbers. The type column identifies what kind of breakpoint
38960 Normal, explicitly set breakpoint.
38963 Normal, explicitly set watchpoint.
38966 Internal breakpoint, used to handle correctly stepping through
38967 @code{longjmp} calls.
38969 @item longjmp resume
38970 Internal breakpoint at the target of a @code{longjmp}.
38973 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
38976 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
38979 Shared library events.
38983 @kindex maint info btrace
38984 @item maint info btrace
38985 Pint information about raw branch tracing data.
38987 @kindex maint btrace packet-history
38988 @item maint btrace packet-history
38989 Print the raw branch trace packets that are used to compute the
38990 execution history for the @samp{record btrace} command. Both the
38991 information and the format in which it is printed depend on the btrace
38996 For the BTS recording format, print a list of blocks of sequential
38997 code. For each block, the following information is printed:
39001 Newer blocks have higher numbers. The oldest block has number zero.
39002 @item Lowest @samp{PC}
39003 @item Highest @samp{PC}
39007 For the Intel Processor Trace recording format, print a list of
39008 Intel Processor Trace packets. For each packet, the following
39009 information is printed:
39012 @item Packet number
39013 Newer packets have higher numbers. The oldest packet has number zero.
39015 The packet's offset in the trace stream.
39016 @item Packet opcode and payload
39020 @kindex maint btrace clear-packet-history
39021 @item maint btrace clear-packet-history
39022 Discards the cached packet history printed by the @samp{maint btrace
39023 packet-history} command. The history will be computed again when
39026 @kindex maint btrace clear
39027 @item maint btrace clear
39028 Discard the branch trace data. The data will be fetched anew and the
39029 branch trace will be recomputed when needed.
39031 This implicitly truncates the branch trace to a single branch trace
39032 buffer. When updating branch trace incrementally, the branch trace
39033 available to @value{GDBN} may be bigger than a single branch trace
39036 @kindex maint set btrace pt skip-pad
39037 @item maint set btrace pt skip-pad
39038 @kindex maint show btrace pt skip-pad
39039 @item maint show btrace pt skip-pad
39040 Control whether @value{GDBN} will skip PAD packets when computing the
39043 @kindex set displaced-stepping
39044 @kindex show displaced-stepping
39045 @cindex displaced stepping support
39046 @cindex out-of-line single-stepping
39047 @item set displaced-stepping
39048 @itemx show displaced-stepping
39049 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39050 if the target supports it. Displaced stepping is a way to single-step
39051 over breakpoints without removing them from the inferior, by executing
39052 an out-of-line copy of the instruction that was originally at the
39053 breakpoint location. It is also known as out-of-line single-stepping.
39056 @item set displaced-stepping on
39057 If the target architecture supports it, @value{GDBN} will use
39058 displaced stepping to step over breakpoints.
39060 @item set displaced-stepping off
39061 @value{GDBN} will not use displaced stepping to step over breakpoints,
39062 even if such is supported by the target architecture.
39064 @cindex non-stop mode, and @samp{set displaced-stepping}
39065 @item set displaced-stepping auto
39066 This is the default mode. @value{GDBN} will use displaced stepping
39067 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39068 architecture supports displaced stepping.
39071 @kindex maint check-psymtabs
39072 @item maint check-psymtabs
39073 Check the consistency of currently expanded psymtabs versus symtabs.
39074 Use this to check, for example, whether a symbol is in one but not the other.
39076 @kindex maint check-symtabs
39077 @item maint check-symtabs
39078 Check the consistency of currently expanded symtabs.
39080 @kindex maint expand-symtabs
39081 @item maint expand-symtabs [@var{regexp}]
39082 Expand symbol tables.
39083 If @var{regexp} is specified, only expand symbol tables for file
39084 names matching @var{regexp}.
39086 @kindex maint set catch-demangler-crashes
39087 @kindex maint show catch-demangler-crashes
39088 @cindex demangler crashes
39089 @item maint set catch-demangler-crashes [on|off]
39090 @itemx maint show catch-demangler-crashes
39091 Control whether @value{GDBN} should attempt to catch crashes in the
39092 symbol name demangler. The default is to attempt to catch crashes.
39093 If enabled, the first time a crash is caught, a core file is created,
39094 the offending symbol is displayed and the user is presented with the
39095 option to terminate the current session.
39097 @kindex maint cplus first_component
39098 @item maint cplus first_component @var{name}
39099 Print the first C@t{++} class/namespace component of @var{name}.
39101 @kindex maint cplus namespace
39102 @item maint cplus namespace
39103 Print the list of possible C@t{++} namespaces.
39105 @kindex maint deprecate
39106 @kindex maint undeprecate
39107 @cindex deprecated commands
39108 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39109 @itemx maint undeprecate @var{command}
39110 Deprecate or undeprecate the named @var{command}. Deprecated commands
39111 cause @value{GDBN} to issue a warning when you use them. The optional
39112 argument @var{replacement} says which newer command should be used in
39113 favor of the deprecated one; if it is given, @value{GDBN} will mention
39114 the replacement as part of the warning.
39116 @kindex maint dump-me
39117 @item maint dump-me
39118 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39119 Cause a fatal signal in the debugger and force it to dump its core.
39120 This is supported only on systems which support aborting a program
39121 with the @code{SIGQUIT} signal.
39123 @kindex maint internal-error
39124 @kindex maint internal-warning
39125 @kindex maint demangler-warning
39126 @cindex demangler crashes
39127 @item maint internal-error @r{[}@var{message-text}@r{]}
39128 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39129 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39131 Cause @value{GDBN} to call the internal function @code{internal_error},
39132 @code{internal_warning} or @code{demangler_warning} and hence behave
39133 as though an internal problem has been detected. In addition to
39134 reporting the internal problem, these functions give the user the
39135 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39136 and @code{internal_warning}) create a core file of the current
39137 @value{GDBN} session.
39139 These commands take an optional parameter @var{message-text} that is
39140 used as the text of the error or warning message.
39142 Here's an example of using @code{internal-error}:
39145 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39146 @dots{}/maint.c:121: internal-error: testing, 1, 2
39147 A problem internal to GDB has been detected. Further
39148 debugging may prove unreliable.
39149 Quit this debugging session? (y or n) @kbd{n}
39150 Create a core file? (y or n) @kbd{n}
39154 @cindex @value{GDBN} internal error
39155 @cindex internal errors, control of @value{GDBN} behavior
39156 @cindex demangler crashes
39158 @kindex maint set internal-error
39159 @kindex maint show internal-error
39160 @kindex maint set internal-warning
39161 @kindex maint show internal-warning
39162 @kindex maint set demangler-warning
39163 @kindex maint show demangler-warning
39164 @item maint set internal-error @var{action} [ask|yes|no]
39165 @itemx maint show internal-error @var{action}
39166 @itemx maint set internal-warning @var{action} [ask|yes|no]
39167 @itemx maint show internal-warning @var{action}
39168 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39169 @itemx maint show demangler-warning @var{action}
39170 When @value{GDBN} reports an internal problem (error or warning) it
39171 gives the user the opportunity to both quit @value{GDBN} and create a
39172 core file of the current @value{GDBN} session. These commands let you
39173 override the default behaviour for each particular @var{action},
39174 described in the table below.
39178 You can specify that @value{GDBN} should always (yes) or never (no)
39179 quit. The default is to ask the user what to do.
39182 You can specify that @value{GDBN} should always (yes) or never (no)
39183 create a core file. The default is to ask the user what to do. Note
39184 that there is no @code{corefile} option for @code{demangler-warning}:
39185 demangler warnings always create a core file and this cannot be
39189 @kindex maint packet
39190 @item maint packet @var{text}
39191 If @value{GDBN} is talking to an inferior via the serial protocol,
39192 then this command sends the string @var{text} to the inferior, and
39193 displays the response packet. @value{GDBN} supplies the initial
39194 @samp{$} character, the terminating @samp{#} character, and the
39197 @kindex maint print architecture
39198 @item maint print architecture @r{[}@var{file}@r{]}
39199 Print the entire architecture configuration. The optional argument
39200 @var{file} names the file where the output goes.
39202 @kindex maint print c-tdesc
39203 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39204 Print the target description (@pxref{Target Descriptions}) as
39205 a C source file. By default, the target description is for the current
39206 target, but if the optional argument @var{file} is provided, that file
39207 is used to produce the description. The @var{file} should be an XML
39208 document, of the form described in @ref{Target Description Format}.
39209 The created source file is built into @value{GDBN} when @value{GDBN} is
39210 built again. This command is used by developers after they add or
39211 modify XML target descriptions.
39213 When the optional flag @samp{-single-feature} is provided then the
39214 target description being processed (either the default, or from
39215 @var{file}) must only contain a single feature. The source file
39216 produced is different in this case.
39218 @kindex maint print xml-tdesc
39219 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39220 Print the target description (@pxref{Target Descriptions}) as an XML
39221 file. By default print the target description for the current target,
39222 but if the optional argument @var{file} is provided, then that file is
39223 read in by GDB and then used to produce the description. The
39224 @var{file} should be an XML document, of the form described in
39225 @ref{Target Description Format}.
39227 @kindex maint check xml-descriptions
39228 @item maint check xml-descriptions @var{dir}
39229 Check that the target descriptions dynamically created by @value{GDBN}
39230 equal the descriptions created from XML files found in @var{dir}.
39232 @anchor{maint check libthread-db}
39233 @kindex maint check libthread-db
39234 @item maint check libthread-db
39235 Run integrity checks on the current inferior's thread debugging
39236 library. This exercises all @code{libthread_db} functionality used by
39237 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39238 @code{proc_service} functions provided by @value{GDBN} that
39239 @code{libthread_db} uses. Note that parts of the test may be skipped
39240 on some platforms when debugging core files.
39242 @kindex maint print core-file-backed-mappings
39243 @cindex memory address space mappings
39244 @item maint print core-file-backed-mappings
39245 Print the file-backed mappings which were loaded from a core file note.
39246 This output represents state internal to @value{GDBN} and should be
39247 similar to the mappings displayed by the @code{info proc mappings}
39250 @kindex maint print dummy-frames
39251 @item maint print dummy-frames
39252 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
39255 (@value{GDBP}) @kbd{b add}
39257 (@value{GDBP}) @kbd{print add(2,3)}
39258 Breakpoint 2, add (a=2, b=3) at @dots{}
39260 The program being debugged stopped while in a function called from GDB.
39262 (@value{GDBP}) @kbd{maint print dummy-frames}
39263 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
39267 Takes an optional file parameter.
39269 @kindex maint print registers
39270 @kindex maint print raw-registers
39271 @kindex maint print cooked-registers
39272 @kindex maint print register-groups
39273 @kindex maint print remote-registers
39274 @item maint print registers @r{[}@var{file}@r{]}
39275 @itemx maint print raw-registers @r{[}@var{file}@r{]}
39276 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
39277 @itemx maint print register-groups @r{[}@var{file}@r{]}
39278 @itemx maint print remote-registers @r{[}@var{file}@r{]}
39279 Print @value{GDBN}'s internal register data structures.
39281 The command @code{maint print raw-registers} includes the contents of
39282 the raw register cache; the command @code{maint print
39283 cooked-registers} includes the (cooked) value of all registers,
39284 including registers which aren't available on the target nor visible
39285 to user; the command @code{maint print register-groups} includes the
39286 groups that each register is a member of; and the command @code{maint
39287 print remote-registers} includes the remote target's register numbers
39288 and offsets in the `G' packets.
39290 These commands take an optional parameter, a file name to which to
39291 write the information.
39293 @kindex maint print reggroups
39294 @item maint print reggroups @r{[}@var{file}@r{]}
39295 Print @value{GDBN}'s internal register group data structures. The
39296 optional argument @var{file} tells to what file to write the
39299 The register groups info looks like this:
39302 (@value{GDBP}) @kbd{maint print reggroups}
39313 @kindex maint flush register-cache
39315 @cindex register cache, flushing
39316 @item maint flush register-cache
39318 Flush the contents of the register cache and as a consequence the
39319 frame cache. This command is useful when debugging issues related to
39320 register fetching, or frame unwinding. The command @code{flushregs}
39321 is deprecated in favor of @code{maint flush register-cache}.
39323 @kindex maint print objfiles
39324 @cindex info for known object files
39325 @item maint print objfiles @r{[}@var{regexp}@r{]}
39326 Print a dump of all known object files.
39327 If @var{regexp} is specified, only print object files whose names
39328 match @var{regexp}. For each object file, this command prints its name,
39329 address in memory, and all of its psymtabs and symtabs.
39331 @kindex maint print user-registers
39332 @cindex user registers
39333 @item maint print user-registers
39334 List all currently available @dfn{user registers}. User registers
39335 typically provide alternate names for actual hardware registers. They
39336 include the four ``standard'' registers @code{$fp}, @code{$pc},
39337 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
39338 registers can be used in expressions in the same way as the canonical
39339 register names, but only the latter are listed by the @code{info
39340 registers} and @code{maint print registers} commands.
39342 @kindex maint print section-scripts
39343 @cindex info for known .debug_gdb_scripts-loaded scripts
39344 @item maint print section-scripts [@var{regexp}]
39345 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
39346 If @var{regexp} is specified, only print scripts loaded by object files
39347 matching @var{regexp}.
39348 For each script, this command prints its name as specified in the objfile,
39349 and the full path if known.
39350 @xref{dotdebug_gdb_scripts section}.
39352 @kindex maint print statistics
39353 @cindex bcache statistics
39354 @item maint print statistics
39355 This command prints, for each object file in the program, various data
39356 about that object file followed by the byte cache (@dfn{bcache})
39357 statistics for the object file. The objfile data includes the number
39358 of minimal, partial, full, and stabs symbols, the number of types
39359 defined by the objfile, the number of as yet unexpanded psym tables,
39360 the number of line tables and string tables, and the amount of memory
39361 used by the various tables. The bcache statistics include the counts,
39362 sizes, and counts of duplicates of all and unique objects, max,
39363 average, and median entry size, total memory used and its overhead and
39364 savings, and various measures of the hash table size and chain
39367 @kindex maint print target-stack
39368 @cindex target stack description
39369 @item maint print target-stack
39370 A @dfn{target} is an interface between the debugger and a particular
39371 kind of file or process. Targets can be stacked in @dfn{strata},
39372 so that more than one target can potentially respond to a request.
39373 In particular, memory accesses will walk down the stack of targets
39374 until they find a target that is interested in handling that particular
39377 This command prints a short description of each layer that was pushed on
39378 the @dfn{target stack}, starting from the top layer down to the bottom one.
39380 @kindex maint print type
39381 @cindex type chain of a data type
39382 @item maint print type @var{expr}
39383 Print the type chain for a type specified by @var{expr}. The argument
39384 can be either a type name or a symbol. If it is a symbol, the type of
39385 that symbol is described. The type chain produced by this command is
39386 a recursive definition of the data type as stored in @value{GDBN}'s
39387 data structures, including its flags and contained types.
39389 @kindex maint selftest
39391 @item maint selftest @r{[}@var{filter}@r{]}
39392 Run any self tests that were compiled in to @value{GDBN}. This will
39393 print a message showing how many tests were run, and how many failed.
39394 If a @var{filter} is passed, only the tests with @var{filter} in their
39397 @kindex maint info selftests
39399 @item maint info selftests
39400 List the selftests compiled in to @value{GDBN}.
39402 @kindex maint set dwarf always-disassemble
39403 @kindex maint show dwarf always-disassemble
39404 @item maint set dwarf always-disassemble
39405 @item maint show dwarf always-disassemble
39406 Control the behavior of @code{info address} when using DWARF debugging
39409 The default is @code{off}, which means that @value{GDBN} should try to
39410 describe a variable's location in an easily readable format. When
39411 @code{on}, @value{GDBN} will instead display the DWARF location
39412 expression in an assembly-like format. Note that some locations are
39413 too complex for @value{GDBN} to describe simply; in this case you will
39414 always see the disassembly form.
39416 Here is an example of the resulting disassembly:
39419 (gdb) info addr argc
39420 Symbol "argc" is a complex DWARF expression:
39424 For more information on these expressions, see
39425 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39427 @kindex maint set dwarf max-cache-age
39428 @kindex maint show dwarf max-cache-age
39429 @item maint set dwarf max-cache-age
39430 @itemx maint show dwarf max-cache-age
39431 Control the DWARF compilation unit cache.
39433 @cindex DWARF compilation units cache
39434 In object files with inter-compilation-unit references, such as those
39435 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39436 reader needs to frequently refer to previously read compilation units.
39437 This setting controls how long a compilation unit will remain in the
39438 cache if it is not referenced. A higher limit means that cached
39439 compilation units will be stored in memory longer, and more total
39440 memory will be used. Setting it to zero disables caching, which will
39441 slow down @value{GDBN} startup, but reduce memory consumption.
39443 @kindex maint set dwarf unwinders
39444 @kindex maint show dwarf unwinders
39445 @item maint set dwarf unwinders
39446 @itemx maint show dwarf unwinders
39447 Control use of the DWARF frame unwinders.
39449 @cindex DWARF frame unwinders
39450 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39451 frame unwinders to build the backtrace. Many of these targets will
39452 also have a second mechanism for building the backtrace for use in
39453 cases where DWARF information is not available, this second mechanism
39454 is often an analysis of a function's prologue.
39456 In order to extend testing coverage of the second level stack
39457 unwinding mechanisms it is helpful to be able to disable the DWARF
39458 stack unwinders, this can be done with this switch.
39460 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39461 advisable, there are cases that are better handled through DWARF than
39462 prologue analysis, and the debug experience is likely to be better
39463 with the DWARF frame unwinders enabled.
39465 If DWARF frame unwinders are not supported for a particular target
39466 architecture, then enabling this flag does not cause them to be used.
39468 @kindex maint set worker-threads
39469 @kindex maint show worker-threads
39470 @item maint set worker-threads
39471 @item maint show worker-threads
39472 Control the number of worker threads that may be used by @value{GDBN}.
39473 On capable hosts, @value{GDBN} may use multiple threads to speed up
39474 certain CPU-intensive operations, such as demangling symbol names.
39475 While the number of threads used by @value{GDBN} may vary, this
39476 command can be used to set an upper bound on this number. The default
39477 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39478 number. Note that this only controls worker threads started by
39479 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39482 @kindex maint set profile
39483 @kindex maint show profile
39484 @cindex profiling GDB
39485 @item maint set profile
39486 @itemx maint show profile
39487 Control profiling of @value{GDBN}.
39489 Profiling will be disabled until you use the @samp{maint set profile}
39490 command to enable it. When you enable profiling, the system will begin
39491 collecting timing and execution count data; when you disable profiling or
39492 exit @value{GDBN}, the results will be written to a log file. Remember that
39493 if you use profiling, @value{GDBN} will overwrite the profiling log file
39494 (often called @file{gmon.out}). If you have a record of important profiling
39495 data in a @file{gmon.out} file, be sure to move it to a safe location.
39497 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
39498 compiled with the @samp{-pg} compiler option.
39500 @kindex maint set show-debug-regs
39501 @kindex maint show show-debug-regs
39502 @cindex hardware debug registers
39503 @item maint set show-debug-regs
39504 @itemx maint show show-debug-regs
39505 Control whether to show variables that mirror the hardware debug
39506 registers. Use @code{on} to enable, @code{off} to disable. If
39507 enabled, the debug registers values are shown when @value{GDBN} inserts or
39508 removes a hardware breakpoint or watchpoint, and when the inferior
39509 triggers a hardware-assisted breakpoint or watchpoint.
39511 @kindex maint set show-all-tib
39512 @kindex maint show show-all-tib
39513 @item maint set show-all-tib
39514 @itemx maint show show-all-tib
39515 Control whether to show all non zero areas within a 1k block starting
39516 at thread local base, when using the @samp{info w32 thread-information-block}
39519 @kindex maint set target-async
39520 @kindex maint show target-async
39521 @item maint set target-async
39522 @itemx maint show target-async
39523 This controls whether @value{GDBN} targets operate in synchronous or
39524 asynchronous mode (@pxref{Background Execution}). Normally the
39525 default is asynchronous, if it is available; but this can be changed
39526 to more easily debug problems occurring only in synchronous mode.
39528 @kindex maint set target-non-stop @var{mode} [on|off|auto]
39529 @kindex maint show target-non-stop
39530 @item maint set target-non-stop
39531 @itemx maint show target-non-stop
39533 This controls whether @value{GDBN} targets always operate in non-stop
39534 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
39535 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
39536 if supported by the target.
39539 @item maint set target-non-stop auto
39540 This is the default mode. @value{GDBN} controls the target in
39541 non-stop mode if the target supports it.
39543 @item maint set target-non-stop on
39544 @value{GDBN} controls the target in non-stop mode even if the target
39545 does not indicate support.
39547 @item maint set target-non-stop off
39548 @value{GDBN} does not control the target in non-stop mode even if the
39549 target supports it.
39552 @kindex maint set tui-resize-message
39553 @kindex maint show tui-resize-message
39554 @item maint set tui-resize-message
39555 @item maint show tui-resize-message
39556 Control whether @value{GDBN} displays a message each time the terminal
39557 is resized when in TUI mode. The default is @code{off}, which means
39558 that @value{GDBN} is silent during resizes. When @code{on},
39559 @value{GDBN} will display a message after a resize is completed; the
39560 message will include a number indicating how many times the terminal
39561 has been resized. This setting is intended for use by the test suite,
39562 where it would otherwise be difficult to determine when a resize and
39563 refresh has been completed.
39565 @kindex maint set per-command
39566 @kindex maint show per-command
39567 @item maint set per-command
39568 @itemx maint show per-command
39569 @cindex resources used by commands
39571 @value{GDBN} can display the resources used by each command.
39572 This is useful in debugging performance problems.
39575 @item maint set per-command space [on|off]
39576 @itemx maint show per-command space
39577 Enable or disable the printing of the memory used by GDB for each command.
39578 If enabled, @value{GDBN} will display how much memory each command
39579 took, following the command's own output.
39580 This can also be requested by invoking @value{GDBN} with the
39581 @option{--statistics} command-line switch (@pxref{Mode Options}).
39583 @item maint set per-command time [on|off]
39584 @itemx maint show per-command time
39585 Enable or disable the printing of the execution time of @value{GDBN}
39587 If enabled, @value{GDBN} will display how much time it
39588 took to execute each command, following the command's own output.
39589 Both CPU time and wallclock time are printed.
39590 Printing both is useful when trying to determine whether the cost is
39591 CPU or, e.g., disk/network latency.
39592 Note that the CPU time printed is for @value{GDBN} only, it does not include
39593 the execution time of the inferior because there's no mechanism currently
39594 to compute how much time was spent by @value{GDBN} and how much time was
39595 spent by the program been debugged.
39596 This can also be requested by invoking @value{GDBN} with the
39597 @option{--statistics} command-line switch (@pxref{Mode Options}).
39599 @item maint set per-command symtab [on|off]
39600 @itemx maint show per-command symtab
39601 Enable or disable the printing of basic symbol table statistics
39603 If enabled, @value{GDBN} will display the following information:
39607 number of symbol tables
39609 number of primary symbol tables
39611 number of blocks in the blockvector
39615 @kindex maint set check-libthread-db
39616 @kindex maint show check-libthread-db
39617 @item maint set check-libthread-db [on|off]
39618 @itemx maint show check-libthread-db
39619 Control whether @value{GDBN} should run integrity checks on inferior
39620 specific thread debugging libraries as they are loaded. The default
39621 is not to perform such checks. If any check fails @value{GDBN} will
39622 unload the library and continue searching for a suitable candidate as
39623 described in @ref{set libthread-db-search-path}. For more information
39624 about the tests, see @ref{maint check libthread-db}.
39626 @kindex maint space
39627 @cindex memory used by commands
39628 @item maint space @var{value}
39629 An alias for @code{maint set per-command space}.
39630 A non-zero value enables it, zero disables it.
39633 @cindex time of command execution
39634 @item maint time @var{value}
39635 An alias for @code{maint set per-command time}.
39636 A non-zero value enables it, zero disables it.
39638 @kindex maint translate-address
39639 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
39640 Find the symbol stored at the location specified by the address
39641 @var{addr} and an optional section name @var{section}. If found,
39642 @value{GDBN} prints the name of the closest symbol and an offset from
39643 the symbol's location to the specified address. This is similar to
39644 the @code{info address} command (@pxref{Symbols}), except that this
39645 command also allows to find symbols in other sections.
39647 If section was not specified, the section in which the symbol was found
39648 is also printed. For dynamically linked executables, the name of
39649 executable or shared library containing the symbol is printed as well.
39651 @kindex maint test-options
39652 @item maint test-options require-delimiter
39653 @itemx maint test-options unknown-is-error
39654 @itemx maint test-options unknown-is-operand
39655 These commands are used by the testsuite to validate the command
39656 options framework. The @code{require-delimiter} variant requires a
39657 double-dash delimiter to indicate end of options. The
39658 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
39659 @code{unknown-is-error} variant throws an error on unknown option,
39660 while @code{unknown-is-operand} treats unknown options as the start of
39661 the command's operands. When run, the commands output the result of
39662 the processed options. When completed, the commands store the
39663 internal result of completion in a variable exposed by the @code{maint
39664 show test-options-completion-result} command.
39666 @kindex maint show test-options-completion-result
39667 @item maint show test-options-completion-result
39668 Shows the result of completing the @code{maint test-options}
39669 subcommands. This is used by the testsuite to validate completion
39670 support in the command options framework.
39672 @kindex maint set test-settings
39673 @kindex maint show test-settings
39674 @item maint set test-settings @var{kind}
39675 @itemx maint show test-settings @var{kind}
39676 These are representative commands for each @var{kind} of setting type
39677 @value{GDBN} supports. They are used by the testsuite for exercising
39678 the settings infrastructure.
39681 @item maint with @var{setting} [@var{value}] [-- @var{command}]
39682 Like the @code{with} command, but works with @code{maintenance set}
39683 variables. This is used by the testsuite to exercise the @code{with}
39684 command's infrastructure.
39688 The following command is useful for non-interactive invocations of
39689 @value{GDBN}, such as in the test suite.
39692 @item set watchdog @var{nsec}
39693 @kindex set watchdog
39694 @cindex watchdog timer
39695 @cindex timeout for commands
39696 Set the maximum number of seconds @value{GDBN} will wait for the
39697 target operation to finish. If this time expires, @value{GDBN}
39698 reports and error and the command is aborted.
39700 @item show watchdog
39701 Show the current setting of the target wait timeout.
39704 @node Remote Protocol
39705 @appendix @value{GDBN} Remote Serial Protocol
39710 * Stop Reply Packets::
39711 * General Query Packets::
39712 * Architecture-Specific Protocol Details::
39713 * Tracepoint Packets::
39714 * Host I/O Packets::
39716 * Notification Packets::
39717 * Remote Non-Stop::
39718 * Packet Acknowledgment::
39720 * File-I/O Remote Protocol Extension::
39721 * Library List Format::
39722 * Library List Format for SVR4 Targets::
39723 * Memory Map Format::
39724 * Thread List Format::
39725 * Traceframe Info Format::
39726 * Branch Trace Format::
39727 * Branch Trace Configuration Format::
39733 There may be occasions when you need to know something about the
39734 protocol---for example, if there is only one serial port to your target
39735 machine, you might want your program to do something special if it
39736 recognizes a packet meant for @value{GDBN}.
39738 In the examples below, @samp{->} and @samp{<-} are used to indicate
39739 transmitted and received data, respectively.
39741 @cindex protocol, @value{GDBN} remote serial
39742 @cindex serial protocol, @value{GDBN} remote
39743 @cindex remote serial protocol
39744 All @value{GDBN} commands and responses (other than acknowledgments
39745 and notifications, see @ref{Notification Packets}) are sent as a
39746 @var{packet}. A @var{packet} is introduced with the character
39747 @samp{$}, the actual @var{packet-data}, and the terminating character
39748 @samp{#} followed by a two-digit @var{checksum}:
39751 @code{$}@var{packet-data}@code{#}@var{checksum}
39755 @cindex checksum, for @value{GDBN} remote
39757 The two-digit @var{checksum} is computed as the modulo 256 sum of all
39758 characters between the leading @samp{$} and the trailing @samp{#} (an
39759 eight bit unsigned checksum).
39761 Implementors should note that prior to @value{GDBN} 5.0 the protocol
39762 specification also included an optional two-digit @var{sequence-id}:
39765 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
39768 @cindex sequence-id, for @value{GDBN} remote
39770 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
39771 has never output @var{sequence-id}s. Stubs that handle packets added
39772 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
39774 When either the host or the target machine receives a packet, the first
39775 response expected is an acknowledgment: either @samp{+} (to indicate
39776 the package was received correctly) or @samp{-} (to request
39780 -> @code{$}@var{packet-data}@code{#}@var{checksum}
39785 The @samp{+}/@samp{-} acknowledgments can be disabled
39786 once a connection is established.
39787 @xref{Packet Acknowledgment}, for details.
39789 The host (@value{GDBN}) sends @var{command}s, and the target (the
39790 debugging stub incorporated in your program) sends a @var{response}. In
39791 the case of step and continue @var{command}s, the response is only sent
39792 when the operation has completed, and the target has again stopped all
39793 threads in all attached processes. This is the default all-stop mode
39794 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
39795 execution mode; see @ref{Remote Non-Stop}, for details.
39797 @var{packet-data} consists of a sequence of characters with the
39798 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
39801 @cindex remote protocol, field separator
39802 Fields within the packet should be separated using @samp{,} @samp{;} or
39803 @samp{:}. Except where otherwise noted all numbers are represented in
39804 @sc{hex} with leading zeros suppressed.
39806 Implementors should note that prior to @value{GDBN} 5.0, the character
39807 @samp{:} could not appear as the third character in a packet (as it
39808 would potentially conflict with the @var{sequence-id}).
39810 @cindex remote protocol, binary data
39811 @anchor{Binary Data}
39812 Binary data in most packets is encoded either as two hexadecimal
39813 digits per byte of binary data. This allowed the traditional remote
39814 protocol to work over connections which were only seven-bit clean.
39815 Some packets designed more recently assume an eight-bit clean
39816 connection, and use a more efficient encoding to send and receive
39819 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
39820 as an escape character. Any escaped byte is transmitted as the escape
39821 character followed by the original character XORed with @code{0x20}.
39822 For example, the byte @code{0x7d} would be transmitted as the two
39823 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
39824 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
39825 @samp{@}}) must always be escaped. Responses sent by the stub
39826 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
39827 is not interpreted as the start of a run-length encoded sequence
39830 Response @var{data} can be run-length encoded to save space.
39831 Run-length encoding replaces runs of identical characters with one
39832 instance of the repeated character, followed by a @samp{*} and a
39833 repeat count. The repeat count is itself sent encoded, to avoid
39834 binary characters in @var{data}: a value of @var{n} is sent as
39835 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
39836 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
39837 code 32) for a repeat count of 3. (This is because run-length
39838 encoding starts to win for counts 3 or more.) Thus, for example,
39839 @samp{0* } is a run-length encoding of ``0000'': the space character
39840 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
39843 The printable characters @samp{#} and @samp{$} or with a numeric value
39844 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
39845 seven repeats (@samp{$}) can be expanded using a repeat count of only
39846 five (@samp{"}). For example, @samp{00000000} can be encoded as
39849 The error response returned for some packets includes a two character
39850 error number. That number is not well defined.
39852 @cindex empty response, for unsupported packets
39853 For any @var{command} not supported by the stub, an empty response
39854 (@samp{$#00}) should be returned. That way it is possible to extend the
39855 protocol. A newer @value{GDBN} can tell if a packet is supported based
39858 At a minimum, a stub is required to support the @samp{?} command to
39859 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
39860 commands for register access, and the @samp{m} and @samp{M} commands
39861 for memory access. Stubs that only control single-threaded targets
39862 can implement run control with the @samp{c} (continue) command, and if
39863 the target architecture supports hardware-assisted single-stepping,
39864 the @samp{s} (step) command. Stubs that support multi-threading
39865 targets should support the @samp{vCont} command. All other commands
39871 The following table provides a complete list of all currently defined
39872 @var{command}s and their corresponding response @var{data}.
39873 @xref{File-I/O Remote Protocol Extension}, for details about the File
39874 I/O extension of the remote protocol.
39876 Each packet's description has a template showing the packet's overall
39877 syntax, followed by an explanation of the packet's meaning. We
39878 include spaces in some of the templates for clarity; these are not
39879 part of the packet's syntax. No @value{GDBN} packet uses spaces to
39880 separate its components. For example, a template like @samp{foo
39881 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
39882 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
39883 @var{baz}. @value{GDBN} does not transmit a space character between the
39884 @samp{foo} and the @var{bar}, or between the @var{bar} and the
39887 @cindex @var{thread-id}, in remote protocol
39888 @anchor{thread-id syntax}
39889 Several packets and replies include a @var{thread-id} field to identify
39890 a thread. Normally these are positive numbers with a target-specific
39891 interpretation, formatted as big-endian hex strings. A @var{thread-id}
39892 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
39895 In addition, the remote protocol supports a multiprocess feature in
39896 which the @var{thread-id} syntax is extended to optionally include both
39897 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
39898 The @var{pid} (process) and @var{tid} (thread) components each have the
39899 format described above: a positive number with target-specific
39900 interpretation formatted as a big-endian hex string, literal @samp{-1}
39901 to indicate all processes or threads (respectively), or @samp{0} to
39902 indicate an arbitrary process or thread. Specifying just a process, as
39903 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
39904 error to specify all processes but a specific thread, such as
39905 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
39906 for those packets and replies explicitly documented to include a process
39907 ID, rather than a @var{thread-id}.
39909 The multiprocess @var{thread-id} syntax extensions are only used if both
39910 @value{GDBN} and the stub report support for the @samp{multiprocess}
39911 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
39914 Note that all packet forms beginning with an upper- or lower-case
39915 letter, other than those described here, are reserved for future use.
39917 Here are the packet descriptions.
39922 @cindex @samp{!} packet
39923 @anchor{extended mode}
39924 Enable extended mode. In extended mode, the remote server is made
39925 persistent. The @samp{R} packet is used to restart the program being
39931 The remote target both supports and has enabled extended mode.
39935 @cindex @samp{?} packet
39937 This is sent when connection is first established to query the reason
39938 the target halted. The reply is the same as for step and continue.
39939 This packet has a special interpretation when the target is in
39940 non-stop mode; see @ref{Remote Non-Stop}.
39943 @xref{Stop Reply Packets}, for the reply specifications.
39945 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
39946 @cindex @samp{A} packet
39947 Initialized @code{argv[]} array passed into program. @var{arglen}
39948 specifies the number of bytes in the hex encoded byte stream
39949 @var{arg}. See @code{gdbserver} for more details.
39954 The arguments were set.
39960 @cindex @samp{b} packet
39961 (Don't use this packet; its behavior is not well-defined.)
39962 Change the serial line speed to @var{baud}.
39964 JTC: @emph{When does the transport layer state change? When it's
39965 received, or after the ACK is transmitted. In either case, there are
39966 problems if the command or the acknowledgment packet is dropped.}
39968 Stan: @emph{If people really wanted to add something like this, and get
39969 it working for the first time, they ought to modify ser-unix.c to send
39970 some kind of out-of-band message to a specially-setup stub and have the
39971 switch happen "in between" packets, so that from remote protocol's point
39972 of view, nothing actually happened.}
39974 @item B @var{addr},@var{mode}
39975 @cindex @samp{B} packet
39976 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
39977 breakpoint at @var{addr}.
39979 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
39980 (@pxref{insert breakpoint or watchpoint packet}).
39982 @cindex @samp{bc} packet
39985 Backward continue. Execute the target system in reverse. No parameter.
39986 @xref{Reverse Execution}, for more information.
39989 @xref{Stop Reply Packets}, for the reply specifications.
39991 @cindex @samp{bs} packet
39994 Backward single step. Execute one instruction in reverse. No parameter.
39995 @xref{Reverse Execution}, for more information.
39998 @xref{Stop Reply Packets}, for the reply specifications.
40000 @item c @r{[}@var{addr}@r{]}
40001 @cindex @samp{c} packet
40002 Continue at @var{addr}, which is the address to resume. If @var{addr}
40003 is omitted, resume at current address.
40005 This packet is deprecated for multi-threading support. @xref{vCont
40009 @xref{Stop Reply Packets}, for the reply specifications.
40011 @item C @var{sig}@r{[};@var{addr}@r{]}
40012 @cindex @samp{C} packet
40013 Continue with signal @var{sig} (hex signal number). If
40014 @samp{;@var{addr}} is omitted, resume at same address.
40016 This packet is deprecated for multi-threading support. @xref{vCont
40020 @xref{Stop Reply Packets}, for the reply specifications.
40023 @cindex @samp{d} packet
40026 Don't use this packet; instead, define a general set packet
40027 (@pxref{General Query Packets}).
40031 @cindex @samp{D} packet
40032 The first form of the packet is used to detach @value{GDBN} from the
40033 remote system. It is sent to the remote target
40034 before @value{GDBN} disconnects via the @code{detach} command.
40036 The second form, including a process ID, is used when multiprocess
40037 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40038 detach only a specific process. The @var{pid} is specified as a
40039 big-endian hex string.
40049 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40050 @cindex @samp{F} packet
40051 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40052 This is part of the File-I/O protocol extension. @xref{File-I/O
40053 Remote Protocol Extension}, for the specification.
40056 @anchor{read registers packet}
40057 @cindex @samp{g} packet
40058 Read general registers.
40062 @item @var{XX@dots{}}
40063 Each byte of register data is described by two hex digits. The bytes
40064 with the register are transmitted in target byte order. The size of
40065 each register and their position within the @samp{g} packet are
40066 determined by the @value{GDBN} internal gdbarch functions
40067 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40069 When reading registers from a trace frame (@pxref{Analyze Collected
40070 Data,,Using the Collected Data}), the stub may also return a string of
40071 literal @samp{x}'s in place of the register data digits, to indicate
40072 that the corresponding register has not been collected, thus its value
40073 is unavailable. For example, for an architecture with 4 registers of
40074 4 bytes each, the following reply indicates to @value{GDBN} that
40075 registers 0 and 2 have not been collected, while registers 1 and 3
40076 have been collected, and both have zero value:
40080 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40087 @item G @var{XX@dots{}}
40088 @cindex @samp{G} packet
40089 Write general registers. @xref{read registers packet}, for a
40090 description of the @var{XX@dots{}} data.
40100 @item H @var{op} @var{thread-id}
40101 @cindex @samp{H} packet
40102 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40103 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40104 should be @samp{c} for step and continue operations (note that this
40105 is deprecated, supporting the @samp{vCont} command is a better
40106 option), and @samp{g} for other operations. The thread designator
40107 @var{thread-id} has the format and interpretation described in
40108 @ref{thread-id syntax}.
40119 @c 'H': How restrictive (or permissive) is the thread model. If a
40120 @c thread is selected and stopped, are other threads allowed
40121 @c to continue to execute? As I mentioned above, I think the
40122 @c semantics of each command when a thread is selected must be
40123 @c described. For example:
40125 @c 'g': If the stub supports threads and a specific thread is
40126 @c selected, returns the register block from that thread;
40127 @c otherwise returns current registers.
40129 @c 'G' If the stub supports threads and a specific thread is
40130 @c selected, sets the registers of the register block of
40131 @c that thread; otherwise sets current registers.
40133 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40134 @anchor{cycle step packet}
40135 @cindex @samp{i} packet
40136 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40137 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40138 step starting at that address.
40141 @cindex @samp{I} packet
40142 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40146 @cindex @samp{k} packet
40149 The exact effect of this packet is not specified.
40151 For a bare-metal target, it may power cycle or reset the target
40152 system. For that reason, the @samp{k} packet has no reply.
40154 For a single-process target, it may kill that process if possible.
40156 A multiple-process target may choose to kill just one process, or all
40157 that are under @value{GDBN}'s control. For more precise control, use
40158 the vKill packet (@pxref{vKill packet}).
40160 If the target system immediately closes the connection in response to
40161 @samp{k}, @value{GDBN} does not consider the lack of packet
40162 acknowledgment to be an error, and assumes the kill was successful.
40164 If connected using @kbd{target extended-remote}, and the target does
40165 not close the connection in response to a kill request, @value{GDBN}
40166 probes the target state as if a new connection was opened
40167 (@pxref{? packet}).
40169 @item m @var{addr},@var{length}
40170 @cindex @samp{m} packet
40171 Read @var{length} addressable memory units starting at address @var{addr}
40172 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40173 any particular boundary.
40175 The stub need not use any particular size or alignment when gathering
40176 data from memory for the response; even if @var{addr} is word-aligned
40177 and @var{length} is a multiple of the word size, the stub is free to
40178 use byte accesses, or not. For this reason, this packet may not be
40179 suitable for accessing memory-mapped I/O devices.
40180 @cindex alignment of remote memory accesses
40181 @cindex size of remote memory accesses
40182 @cindex memory, alignment and size of remote accesses
40186 @item @var{XX@dots{}}
40187 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40188 The reply may contain fewer addressable memory units than requested if the
40189 server was able to read only part of the region of memory.
40194 @item M @var{addr},@var{length}:@var{XX@dots{}}
40195 @cindex @samp{M} packet
40196 Write @var{length} addressable memory units starting at address @var{addr}
40197 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
40198 byte is transmitted as a two-digit hexadecimal number.
40205 for an error (this includes the case where only part of the data was
40210 @cindex @samp{p} packet
40211 Read the value of register @var{n}; @var{n} is in hex.
40212 @xref{read registers packet}, for a description of how the returned
40213 register value is encoded.
40217 @item @var{XX@dots{}}
40218 the register's value
40222 Indicating an unrecognized @var{query}.
40225 @item P @var{n@dots{}}=@var{r@dots{}}
40226 @anchor{write register packet}
40227 @cindex @samp{P} packet
40228 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
40229 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
40230 digits for each byte in the register (target byte order).
40240 @item q @var{name} @var{params}@dots{}
40241 @itemx Q @var{name} @var{params}@dots{}
40242 @cindex @samp{q} packet
40243 @cindex @samp{Q} packet
40244 General query (@samp{q}) and set (@samp{Q}). These packets are
40245 described fully in @ref{General Query Packets}.
40248 @cindex @samp{r} packet
40249 Reset the entire system.
40251 Don't use this packet; use the @samp{R} packet instead.
40254 @cindex @samp{R} packet
40255 Restart the program being debugged. The @var{XX}, while needed, is ignored.
40256 This packet is only available in extended mode (@pxref{extended mode}).
40258 The @samp{R} packet has no reply.
40260 @item s @r{[}@var{addr}@r{]}
40261 @cindex @samp{s} packet
40262 Single step, resuming at @var{addr}. If
40263 @var{addr} is omitted, resume at same address.
40265 This packet is deprecated for multi-threading support. @xref{vCont
40269 @xref{Stop Reply Packets}, for the reply specifications.
40271 @item S @var{sig}@r{[};@var{addr}@r{]}
40272 @anchor{step with signal packet}
40273 @cindex @samp{S} packet
40274 Step with signal. This is analogous to the @samp{C} packet, but
40275 requests a single-step, rather than a normal resumption of execution.
40277 This packet is deprecated for multi-threading support. @xref{vCont
40281 @xref{Stop Reply Packets}, for the reply specifications.
40283 @item t @var{addr}:@var{PP},@var{MM}
40284 @cindex @samp{t} packet
40285 Search backwards starting at address @var{addr} for a match with pattern
40286 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
40287 There must be at least 3 digits in @var{addr}.
40289 @item T @var{thread-id}
40290 @cindex @samp{T} packet
40291 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
40296 thread is still alive
40302 Packets starting with @samp{v} are identified by a multi-letter name,
40303 up to the first @samp{;} or @samp{?} (or the end of the packet).
40305 @item vAttach;@var{pid}
40306 @cindex @samp{vAttach} packet
40307 Attach to a new process with the specified process ID @var{pid}.
40308 The process ID is a
40309 hexadecimal integer identifying the process. In all-stop mode, all
40310 threads in the attached process are stopped; in non-stop mode, it may be
40311 attached without being stopped if that is supported by the target.
40313 @c In non-stop mode, on a successful vAttach, the stub should set the
40314 @c current thread to a thread of the newly-attached process. After
40315 @c attaching, GDB queries for the attached process's thread ID with qC.
40316 @c Also note that, from a user perspective, whether or not the
40317 @c target is stopped on attach in non-stop mode depends on whether you
40318 @c use the foreground or background version of the attach command, not
40319 @c on what vAttach does; GDB does the right thing with respect to either
40320 @c stopping or restarting threads.
40322 This packet is only available in extended mode (@pxref{extended mode}).
40328 @item @r{Any stop packet}
40329 for success in all-stop mode (@pxref{Stop Reply Packets})
40331 for success in non-stop mode (@pxref{Remote Non-Stop})
40334 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
40335 @cindex @samp{vCont} packet
40336 @anchor{vCont packet}
40337 Resume the inferior, specifying different actions for each thread.
40339 For each inferior thread, the leftmost action with a matching
40340 @var{thread-id} is applied. Threads that don't match any action
40341 remain in their current state. Thread IDs are specified using the
40342 syntax described in @ref{thread-id syntax}. If multiprocess
40343 extensions (@pxref{multiprocess extensions}) are supported, actions
40344 can be specified to match all threads in a process by using the
40345 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
40346 @var{thread-id} matches all threads. Specifying no actions is an
40349 Currently supported actions are:
40355 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
40359 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
40362 @item r @var{start},@var{end}
40363 Step once, and then keep stepping as long as the thread stops at
40364 addresses between @var{start} (inclusive) and @var{end} (exclusive).
40365 The remote stub reports a stop reply when either the thread goes out
40366 of the range or is stopped due to an unrelated reason, such as hitting
40367 a breakpoint. @xref{range stepping}.
40369 If the range is empty (@var{start} == @var{end}), then the action
40370 becomes equivalent to the @samp{s} action. In other words,
40371 single-step once, and report the stop (even if the stepped instruction
40372 jumps to @var{start}).
40374 (A stop reply may be sent at any point even if the PC is still within
40375 the stepping range; for example, it is valid to implement this packet
40376 in a degenerate way as a single instruction step operation.)
40380 The optional argument @var{addr} normally associated with the
40381 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
40382 not supported in @samp{vCont}.
40384 The @samp{t} action is only relevant in non-stop mode
40385 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
40386 A stop reply should be generated for any affected thread not already stopped.
40387 When a thread is stopped by means of a @samp{t} action,
40388 the corresponding stop reply should indicate that the thread has stopped with
40389 signal @samp{0}, regardless of whether the target uses some other signal
40390 as an implementation detail.
40392 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
40393 @samp{r} actions for threads that are already running. Conversely,
40394 the server must ignore @samp{t} actions for threads that are already
40397 @emph{Note:} In non-stop mode, a thread is considered running until
40398 @value{GDBN} acknowledges an asynchronous stop notification for it with
40399 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40401 The stub must support @samp{vCont} if it reports support for
40402 multiprocess extensions (@pxref{multiprocess extensions}).
40405 @xref{Stop Reply Packets}, for the reply specifications.
40408 @cindex @samp{vCont?} packet
40409 Request a list of actions supported by the @samp{vCont} packet.
40413 @item vCont@r{[};@var{action}@dots{}@r{]}
40414 The @samp{vCont} packet is supported. Each @var{action} is a supported
40415 command in the @samp{vCont} packet.
40417 The @samp{vCont} packet is not supported.
40420 @anchor{vCtrlC packet}
40422 @cindex @samp{vCtrlC} packet
40423 Interrupt remote target as if a control-C was pressed on the remote
40424 terminal. This is the equivalent to reacting to the @code{^C}
40425 (@samp{\003}, the control-C character) character in all-stop mode
40426 while the target is running, except this works in non-stop mode.
40427 @xref{interrupting remote targets}, for more info on the all-stop
40438 @item vFile:@var{operation}:@var{parameter}@dots{}
40439 @cindex @samp{vFile} packet
40440 Perform a file operation on the target system. For details,
40441 see @ref{Host I/O Packets}.
40443 @item vFlashErase:@var{addr},@var{length}
40444 @cindex @samp{vFlashErase} packet
40445 Direct the stub to erase @var{length} bytes of flash starting at
40446 @var{addr}. The region may enclose any number of flash blocks, but
40447 its start and end must fall on block boundaries, as indicated by the
40448 flash block size appearing in the memory map (@pxref{Memory Map
40449 Format}). @value{GDBN} groups flash memory programming operations
40450 together, and sends a @samp{vFlashDone} request after each group; the
40451 stub is allowed to delay erase operation until the @samp{vFlashDone}
40452 packet is received.
40462 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
40463 @cindex @samp{vFlashWrite} packet
40464 Direct the stub to write data to flash address @var{addr}. The data
40465 is passed in binary form using the same encoding as for the @samp{X}
40466 packet (@pxref{Binary Data}). The memory ranges specified by
40467 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
40468 not overlap, and must appear in order of increasing addresses
40469 (although @samp{vFlashErase} packets for higher addresses may already
40470 have been received; the ordering is guaranteed only between
40471 @samp{vFlashWrite} packets). If a packet writes to an address that was
40472 neither erased by a preceding @samp{vFlashErase} packet nor by some other
40473 target-specific method, the results are unpredictable.
40481 for vFlashWrite addressing non-flash memory
40487 @cindex @samp{vFlashDone} packet
40488 Indicate to the stub that flash programming operation is finished.
40489 The stub is permitted to delay or batch the effects of a group of
40490 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
40491 @samp{vFlashDone} packet is received. The contents of the affected
40492 regions of flash memory are unpredictable until the @samp{vFlashDone}
40493 request is completed.
40495 @item vKill;@var{pid}
40496 @cindex @samp{vKill} packet
40497 @anchor{vKill packet}
40498 Kill the process with the specified process ID @var{pid}, which is a
40499 hexadecimal integer identifying the process. This packet is used in
40500 preference to @samp{k} when multiprocess protocol extensions are
40501 supported; see @ref{multiprocess extensions}.
40511 @item vMustReplyEmpty
40512 @cindex @samp{vMustReplyEmpty} packet
40513 The correct reply to an unknown @samp{v} packet is to return the empty
40514 string, however, some older versions of @command{gdbserver} would
40515 incorrectly return @samp{OK} for unknown @samp{v} packets.
40517 The @samp{vMustReplyEmpty} is used as a feature test to check how
40518 @command{gdbserver} handles unknown packets, it is important that this
40519 packet be handled in the same way as other unknown @samp{v} packets.
40520 If this packet is handled differently to other unknown @samp{v}
40521 packets then it is possible that @value{GDBN} may run into problems in
40522 other areas, specifically around use of @samp{vFile:setfs:}.
40524 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
40525 @cindex @samp{vRun} packet
40526 Run the program @var{filename}, passing it each @var{argument} on its
40527 command line. The file and arguments are hex-encoded strings. If
40528 @var{filename} is an empty string, the stub may use a default program
40529 (e.g.@: the last program run). The program is created in the stopped
40532 @c FIXME: What about non-stop mode?
40534 This packet is only available in extended mode (@pxref{extended mode}).
40540 @item @r{Any stop packet}
40541 for success (@pxref{Stop Reply Packets})
40545 @cindex @samp{vStopped} packet
40546 @xref{Notification Packets}.
40548 @item X @var{addr},@var{length}:@var{XX@dots{}}
40550 @cindex @samp{X} packet
40551 Write data to memory, where the data is transmitted in binary.
40552 Memory is specified by its address @var{addr} and number of addressable memory
40553 units @var{length} (@pxref{addressable memory unit});
40554 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
40564 @item z @var{type},@var{addr},@var{kind}
40565 @itemx Z @var{type},@var{addr},@var{kind}
40566 @anchor{insert breakpoint or watchpoint packet}
40567 @cindex @samp{z} packet
40568 @cindex @samp{Z} packets
40569 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
40570 watchpoint starting at address @var{address} of kind @var{kind}.
40572 Each breakpoint and watchpoint packet @var{type} is documented
40575 @emph{Implementation notes: A remote target shall return an empty string
40576 for an unrecognized breakpoint or watchpoint packet @var{type}. A
40577 remote target shall support either both or neither of a given
40578 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
40579 avoid potential problems with duplicate packets, the operations should
40580 be implemented in an idempotent way.}
40582 @item z0,@var{addr},@var{kind}
40583 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40584 @cindex @samp{z0} packet
40585 @cindex @samp{Z0} packet
40586 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
40587 @var{addr} of type @var{kind}.
40589 A software breakpoint is implemented by replacing the instruction at
40590 @var{addr} with a software breakpoint or trap instruction. The
40591 @var{kind} is target-specific and typically indicates the size of the
40592 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
40593 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
40594 architectures have additional meanings for @var{kind}
40595 (@pxref{Architecture-Specific Protocol Details}); if no
40596 architecture-specific value is being used, it should be @samp{0}.
40597 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
40598 conditional expressions in bytecode form that should be evaluated on
40599 the target's side. These are the conditions that should be taken into
40600 consideration when deciding if the breakpoint trigger should be
40601 reported back to @value{GDBN}.
40603 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
40604 for how to best report a software breakpoint event to @value{GDBN}.
40606 The @var{cond_list} parameter is comprised of a series of expressions,
40607 concatenated without separators. Each expression has the following form:
40611 @item X @var{len},@var{expr}
40612 @var{len} is the length of the bytecode expression and @var{expr} is the
40613 actual conditional expression in bytecode form.
40617 The optional @var{cmd_list} parameter introduces commands that may be
40618 run on the target, rather than being reported back to @value{GDBN}.
40619 The parameter starts with a numeric flag @var{persist}; if the flag is
40620 nonzero, then the breakpoint may remain active and the commands
40621 continue to be run even when @value{GDBN} disconnects from the target.
40622 Following this flag is a series of expressions concatenated with no
40623 separators. Each expression has the following form:
40627 @item X @var{len},@var{expr}
40628 @var{len} is the length of the bytecode expression and @var{expr} is the
40629 actual commands expression in bytecode form.
40633 @emph{Implementation note: It is possible for a target to copy or move
40634 code that contains software breakpoints (e.g., when implementing
40635 overlays). The behavior of this packet, in the presence of such a
40636 target, is not defined.}
40648 @item z1,@var{addr},@var{kind}
40649 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40650 @cindex @samp{z1} packet
40651 @cindex @samp{Z1} packet
40652 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
40653 address @var{addr}.
40655 A hardware breakpoint is implemented using a mechanism that is not
40656 dependent on being able to modify the target's memory. The
40657 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
40658 same meaning as in @samp{Z0} packets.
40660 @emph{Implementation note: A hardware breakpoint is not affected by code
40673 @item z2,@var{addr},@var{kind}
40674 @itemx Z2,@var{addr},@var{kind}
40675 @cindex @samp{z2} packet
40676 @cindex @samp{Z2} packet
40677 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
40678 The number of bytes to watch is specified by @var{kind}.
40690 @item z3,@var{addr},@var{kind}
40691 @itemx Z3,@var{addr},@var{kind}
40692 @cindex @samp{z3} packet
40693 @cindex @samp{Z3} packet
40694 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
40695 The number of bytes to watch is specified by @var{kind}.
40707 @item z4,@var{addr},@var{kind}
40708 @itemx Z4,@var{addr},@var{kind}
40709 @cindex @samp{z4} packet
40710 @cindex @samp{Z4} packet
40711 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
40712 The number of bytes to watch is specified by @var{kind}.
40726 @node Stop Reply Packets
40727 @section Stop Reply Packets
40728 @cindex stop reply packets
40730 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
40731 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
40732 receive any of the below as a reply. Except for @samp{?}
40733 and @samp{vStopped}, that reply is only returned
40734 when the target halts. In the below the exact meaning of @dfn{signal
40735 number} is defined by the header @file{include/gdb/signals.h} in the
40736 @value{GDBN} source code.
40738 In non-stop mode, the server will simply reply @samp{OK} to commands
40739 such as @samp{vCont}; any stop will be the subject of a future
40740 notification. @xref{Remote Non-Stop}.
40742 As in the description of request packets, we include spaces in the
40743 reply templates for clarity; these are not part of the reply packet's
40744 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
40750 The program received signal number @var{AA} (a two-digit hexadecimal
40751 number). This is equivalent to a @samp{T} response with no
40752 @var{n}:@var{r} pairs.
40754 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
40755 @cindex @samp{T} packet reply
40756 The program received signal number @var{AA} (a two-digit hexadecimal
40757 number). This is equivalent to an @samp{S} response, except that the
40758 @samp{@var{n}:@var{r}} pairs can carry values of important registers
40759 and other information directly in the stop reply packet, reducing
40760 round-trip latency. Single-step and breakpoint traps are reported
40761 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
40765 If @var{n} is a hexadecimal number, it is a register number, and the
40766 corresponding @var{r} gives that register's value. The data @var{r} is a
40767 series of bytes in target byte order, with each byte given by a
40768 two-digit hex number.
40771 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
40772 the stopped thread, as specified in @ref{thread-id syntax}.
40775 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
40776 the core on which the stop event was detected.
40779 If @var{n} is a recognized @dfn{stop reason}, it describes a more
40780 specific event that stopped the target. The currently defined stop
40781 reasons are listed below. The @var{aa} should be @samp{05}, the trap
40782 signal. At most one stop reason should be present.
40785 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
40786 and go on to the next; this allows us to extend the protocol in the
40790 The currently defined stop reasons are:
40796 The packet indicates a watchpoint hit, and @var{r} is the data address, in
40799 @item syscall_entry
40800 @itemx syscall_return
40801 The packet indicates a syscall entry or return, and @var{r} is the
40802 syscall number, in hex.
40804 @cindex shared library events, remote reply
40806 The packet indicates that the loaded libraries have changed.
40807 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
40808 list of loaded libraries. The @var{r} part is ignored.
40810 @cindex replay log events, remote reply
40812 The packet indicates that the target cannot continue replaying
40813 logged execution events, because it has reached the end (or the
40814 beginning when executing backward) of the log. The value of @var{r}
40815 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
40816 for more information.
40819 @anchor{swbreak stop reason}
40820 The packet indicates a software breakpoint instruction was executed,
40821 irrespective of whether it was @value{GDBN} that planted the
40822 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
40823 part must be left empty.
40825 On some architectures, such as x86, at the architecture level, when a
40826 breakpoint instruction executes the program counter points at the
40827 breakpoint address plus an offset. On such targets, the stub is
40828 responsible for adjusting the PC to point back at the breakpoint
40831 This packet should not be sent by default; older @value{GDBN} versions
40832 did not support it. @value{GDBN} requests it, by supplying an
40833 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40834 remote stub must also supply the appropriate @samp{qSupported} feature
40835 indicating support.
40837 This packet is required for correct non-stop mode operation.
40840 The packet indicates the target stopped for a hardware breakpoint.
40841 The @var{r} part must be left empty.
40843 The same remarks about @samp{qSupported} and non-stop mode above
40846 @cindex fork events, remote reply
40848 The packet indicates that @code{fork} was called, and @var{r}
40849 is the thread ID of the new child process. Refer to
40850 @ref{thread-id syntax} for the format of the @var{thread-id}
40851 field. This packet is only applicable to targets that support
40854 This packet should not be sent by default; older @value{GDBN} versions
40855 did not support it. @value{GDBN} requests it, by supplying an
40856 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40857 remote stub must also supply the appropriate @samp{qSupported} feature
40858 indicating support.
40860 @cindex vfork events, remote reply
40862 The packet indicates that @code{vfork} was called, and @var{r}
40863 is the thread ID of the new child process. Refer to
40864 @ref{thread-id syntax} for the format of the @var{thread-id}
40865 field. This packet is only applicable to targets that support
40868 This packet should not be sent by default; older @value{GDBN} versions
40869 did not support it. @value{GDBN} requests it, by supplying an
40870 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40871 remote stub must also supply the appropriate @samp{qSupported} feature
40872 indicating support.
40874 @cindex vforkdone events, remote reply
40876 The packet indicates that a child process created by a vfork
40877 has either called @code{exec} or terminated, so that the
40878 address spaces of the parent and child process are no longer
40879 shared. The @var{r} part is ignored. This packet is only
40880 applicable to targets that support vforkdone events.
40882 This packet should not be sent by default; older @value{GDBN} versions
40883 did not support it. @value{GDBN} requests it, by supplying an
40884 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40885 remote stub must also supply the appropriate @samp{qSupported} feature
40886 indicating support.
40888 @cindex exec events, remote reply
40890 The packet indicates that @code{execve} was called, and @var{r}
40891 is the absolute pathname of the file that was executed, in hex.
40892 This packet is only applicable to targets that support exec events.
40894 This packet should not be sent by default; older @value{GDBN} versions
40895 did not support it. @value{GDBN} requests it, by supplying an
40896 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40897 remote stub must also supply the appropriate @samp{qSupported} feature
40898 indicating support.
40900 @cindex thread create event, remote reply
40901 @anchor{thread create event}
40903 The packet indicates that the thread was just created. The new thread
40904 is stopped until @value{GDBN} sets it running with a resumption packet
40905 (@pxref{vCont packet}). This packet should not be sent by default;
40906 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
40907 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
40908 @var{r} part is ignored.
40913 @itemx W @var{AA} ; process:@var{pid}
40914 The process exited, and @var{AA} is the exit status. This is only
40915 applicable to certain targets.
40917 The second form of the response, including the process ID of the
40918 exited process, can be used only when @value{GDBN} has reported
40919 support for multiprocess protocol extensions; see @ref{multiprocess
40920 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40924 @itemx X @var{AA} ; process:@var{pid}
40925 The process terminated with signal @var{AA}.
40927 The second form of the response, including the process ID of the
40928 terminated process, can be used only when @value{GDBN} has reported
40929 support for multiprocess protocol extensions; see @ref{multiprocess
40930 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40933 @anchor{thread exit event}
40934 @cindex thread exit event, remote reply
40935 @item w @var{AA} ; @var{tid}
40937 The thread exited, and @var{AA} is the exit status. This response
40938 should not be sent by default; @value{GDBN} requests it with the
40939 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
40940 @var{AA} is formatted as a big-endian hex string.
40943 There are no resumed threads left in the target. In other words, even
40944 though the process is alive, the last resumed thread has exited. For
40945 example, say the target process has two threads: thread 1 and thread
40946 2. The client leaves thread 1 stopped, and resumes thread 2, which
40947 subsequently exits. At this point, even though the process is still
40948 alive, and thus no @samp{W} stop reply is sent, no thread is actually
40949 executing either. The @samp{N} stop reply thus informs the client
40950 that it can stop waiting for stop replies. This packet should not be
40951 sent by default; older @value{GDBN} versions did not support it.
40952 @value{GDBN} requests it, by supplying an appropriate
40953 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
40954 also supply the appropriate @samp{qSupported} feature indicating
40957 @item O @var{XX}@dots{}
40958 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
40959 written as the program's console output. This can happen at any time
40960 while the program is running and the debugger should continue to wait
40961 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
40963 @item F @var{call-id},@var{parameter}@dots{}
40964 @var{call-id} is the identifier which says which host system call should
40965 be called. This is just the name of the function. Translation into the
40966 correct system call is only applicable as it's defined in @value{GDBN}.
40967 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
40970 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
40971 this very system call.
40973 The target replies with this packet when it expects @value{GDBN} to
40974 call a host system call on behalf of the target. @value{GDBN} replies
40975 with an appropriate @samp{F} packet and keeps up waiting for the next
40976 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
40977 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
40978 Protocol Extension}, for more details.
40982 @node General Query Packets
40983 @section General Query Packets
40984 @cindex remote query requests
40986 Packets starting with @samp{q} are @dfn{general query packets};
40987 packets starting with @samp{Q} are @dfn{general set packets}. General
40988 query and set packets are a semi-unified form for retrieving and
40989 sending information to and from the stub.
40991 The initial letter of a query or set packet is followed by a name
40992 indicating what sort of thing the packet applies to. For example,
40993 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
40994 definitions with the stub. These packet names follow some
40999 The name must not contain commas, colons or semicolons.
41001 Most @value{GDBN} query and set packets have a leading upper case
41004 The names of custom vendor packets should use a company prefix, in
41005 lower case, followed by a period. For example, packets designed at
41006 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41007 foos) or @samp{Qacme.bar} (for setting bars).
41010 The name of a query or set packet should be separated from any
41011 parameters by a @samp{:}; the parameters themselves should be
41012 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41013 full packet name, and check for a separator or the end of the packet,
41014 in case two packet names share a common prefix. New packets should not begin
41015 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41016 packets predate these conventions, and have arguments without any terminator
41017 for the packet name; we suspect they are in widespread use in places that
41018 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41019 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41022 Like the descriptions of the other packets, each description here
41023 has a template showing the packet's overall syntax, followed by an
41024 explanation of the packet's meaning. We include spaces in some of the
41025 templates for clarity; these are not part of the packet's syntax. No
41026 @value{GDBN} packet uses spaces to separate its components.
41028 Here are the currently defined query and set packets:
41034 Turn on or off the agent as a helper to perform some debugging operations
41035 delegated from @value{GDBN} (@pxref{Control Agent}).
41037 @item QAllow:@var{op}:@var{val}@dots{}
41038 @cindex @samp{QAllow} packet
41039 Specify which operations @value{GDBN} expects to request of the
41040 target, as a semicolon-separated list of operation name and value
41041 pairs. Possible values for @var{op} include @samp{WriteReg},
41042 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41043 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41044 indicating that @value{GDBN} will not request the operation, or 1,
41045 indicating that it may. (The target can then use this to set up its
41046 own internals optimally, for instance if the debugger never expects to
41047 insert breakpoints, it may not need to install its own trap handler.)
41050 @cindex current thread, remote request
41051 @cindex @samp{qC} packet
41052 Return the current thread ID.
41056 @item QC @var{thread-id}
41057 Where @var{thread-id} is a thread ID as documented in
41058 @ref{thread-id syntax}.
41059 @item @r{(anything else)}
41060 Any other reply implies the old thread ID.
41063 @item qCRC:@var{addr},@var{length}
41064 @cindex CRC of memory block, remote request
41065 @cindex @samp{qCRC} packet
41066 @anchor{qCRC packet}
41067 Compute the CRC checksum of a block of memory using CRC-32 defined in
41068 IEEE 802.3. The CRC is computed byte at a time, taking the most
41069 significant bit of each byte first. The initial pattern code
41070 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41072 @emph{Note:} This is the same CRC used in validating separate debug
41073 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41074 Files}). However the algorithm is slightly different. When validating
41075 separate debug files, the CRC is computed taking the @emph{least}
41076 significant bit of each byte first, and the final result is inverted to
41077 detect trailing zeros.
41082 An error (such as memory fault)
41083 @item C @var{crc32}
41084 The specified memory region's checksum is @var{crc32}.
41087 @item QDisableRandomization:@var{value}
41088 @cindex disable address space randomization, remote request
41089 @cindex @samp{QDisableRandomization} packet
41090 Some target operating systems will randomize the virtual address space
41091 of the inferior process as a security feature, but provide a feature
41092 to disable such randomization, e.g.@: to allow for a more deterministic
41093 debugging experience. On such systems, this packet with a @var{value}
41094 of 1 directs the target to disable address space randomization for
41095 processes subsequently started via @samp{vRun} packets, while a packet
41096 with a @var{value} of 0 tells the target to enable address space
41099 This packet is only available in extended mode (@pxref{extended mode}).
41104 The request succeeded.
41107 An error occurred. The error number @var{nn} is given as hex digits.
41110 An empty reply indicates that @samp{QDisableRandomization} is not supported
41114 This packet is not probed by default; the remote stub must request it,
41115 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41116 This should only be done on targets that actually support disabling
41117 address space randomization.
41119 @item QStartupWithShell:@var{value}
41120 @cindex startup with shell, remote request
41121 @cindex @samp{QStartupWithShell} packet
41122 On UNIX-like targets, it is possible to start the inferior using a
41123 shell program. This is the default behavior on both @value{GDBN} and
41124 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41125 used to inform @command{gdbserver} whether it should start the
41126 inferior using a shell or not.
41128 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41129 to start the inferior. If @var{value} is @samp{1},
41130 @command{gdbserver} will use a shell to start the inferior. All other
41131 values are considered an error.
41133 This packet is only available in extended mode (@pxref{extended
41139 The request succeeded.
41142 An error occurred. The error number @var{nn} is given as hex digits.
41145 This packet is not probed by default; the remote stub must request it,
41146 by supplying an appropriate @samp{qSupported} response
41147 (@pxref{qSupported}). This should only be done on targets that
41148 actually support starting the inferior using a shell.
41150 Use of this packet is controlled by the @code{set startup-with-shell}
41151 command; @pxref{set startup-with-shell}.
41153 @item QEnvironmentHexEncoded:@var{hex-value}
41154 @anchor{QEnvironmentHexEncoded}
41155 @cindex set environment variable, remote request
41156 @cindex @samp{QEnvironmentHexEncoded} packet
41157 On UNIX-like targets, it is possible to set environment variables that
41158 will be passed to the inferior during the startup process. This
41159 packet is used to inform @command{gdbserver} of an environment
41160 variable that has been defined by the user on @value{GDBN} (@pxref{set
41163 The packet is composed by @var{hex-value}, an hex encoded
41164 representation of the @var{name=value} format representing an
41165 environment variable. The name of the environment variable is
41166 represented by @var{name}, and the value to be assigned to the
41167 environment variable is represented by @var{value}. If the variable
41168 has no value (i.e., the value is @code{null}), then @var{value} will
41171 This packet is only available in extended mode (@pxref{extended
41177 The request succeeded.
41180 This packet is not probed by default; the remote stub must request it,
41181 by supplying an appropriate @samp{qSupported} response
41182 (@pxref{qSupported}). This should only be done on targets that
41183 actually support passing environment variables to the starting
41186 This packet is related to the @code{set environment} command;
41187 @pxref{set environment}.
41189 @item QEnvironmentUnset:@var{hex-value}
41190 @anchor{QEnvironmentUnset}
41191 @cindex unset environment variable, remote request
41192 @cindex @samp{QEnvironmentUnset} packet
41193 On UNIX-like targets, it is possible to unset environment variables
41194 before starting the inferior in the remote target. This packet is
41195 used to inform @command{gdbserver} of an environment variable that has
41196 been unset by the user on @value{GDBN} (@pxref{unset environment}).
41198 The packet is composed by @var{hex-value}, an hex encoded
41199 representation of the name of the environment variable to be unset.
41201 This packet is only available in extended mode (@pxref{extended
41207 The request succeeded.
41210 This packet is not probed by default; the remote stub must request it,
41211 by supplying an appropriate @samp{qSupported} response
41212 (@pxref{qSupported}). This should only be done on targets that
41213 actually support passing environment variables to the starting
41216 This packet is related to the @code{unset environment} command;
41217 @pxref{unset environment}.
41219 @item QEnvironmentReset
41220 @anchor{QEnvironmentReset}
41221 @cindex reset environment, remote request
41222 @cindex @samp{QEnvironmentReset} packet
41223 On UNIX-like targets, this packet is used to reset the state of
41224 environment variables in the remote target before starting the
41225 inferior. In this context, reset means unsetting all environment
41226 variables that were previously set by the user (i.e., were not
41227 initially present in the environment). It is sent to
41228 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
41229 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
41230 (@pxref{QEnvironmentUnset}) packets.
41232 This packet is only available in extended mode (@pxref{extended
41238 The request succeeded.
41241 This packet is not probed by default; the remote stub must request it,
41242 by supplying an appropriate @samp{qSupported} response
41243 (@pxref{qSupported}). This should only be done on targets that
41244 actually support passing environment variables to the starting
41247 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
41248 @anchor{QSetWorkingDir packet}
41249 @cindex set working directory, remote request
41250 @cindex @samp{QSetWorkingDir} packet
41251 This packet is used to inform the remote server of the intended
41252 current working directory for programs that are going to be executed.
41254 The packet is composed by @var{directory}, an hex encoded
41255 representation of the directory that the remote inferior will use as
41256 its current working directory. If @var{directory} is an empty string,
41257 the remote server should reset the inferior's current working
41258 directory to its original, empty value.
41260 This packet is only available in extended mode (@pxref{extended
41266 The request succeeded.
41270 @itemx qsThreadInfo
41271 @cindex list active threads, remote request
41272 @cindex @samp{qfThreadInfo} packet
41273 @cindex @samp{qsThreadInfo} packet
41274 Obtain a list of all active thread IDs from the target (OS). Since there
41275 may be too many active threads to fit into one reply packet, this query
41276 works iteratively: it may require more than one query/reply sequence to
41277 obtain the entire list of threads. The first query of the sequence will
41278 be the @samp{qfThreadInfo} query; subsequent queries in the
41279 sequence will be the @samp{qsThreadInfo} query.
41281 NOTE: This packet replaces the @samp{qL} query (see below).
41285 @item m @var{thread-id}
41287 @item m @var{thread-id},@var{thread-id}@dots{}
41288 a comma-separated list of thread IDs
41290 (lower case letter @samp{L}) denotes end of list.
41293 In response to each query, the target will reply with a list of one or
41294 more thread IDs, separated by commas.
41295 @value{GDBN} will respond to each reply with a request for more thread
41296 ids (using the @samp{qs} form of the query), until the target responds
41297 with @samp{l} (lower-case ell, for @dfn{last}).
41298 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
41301 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
41302 initial connection with the remote target, and the very first thread ID
41303 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
41304 message. Therefore, the stub should ensure that the first thread ID in
41305 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
41307 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
41308 @cindex get thread-local storage address, remote request
41309 @cindex @samp{qGetTLSAddr} packet
41310 Fetch the address associated with thread local storage specified
41311 by @var{thread-id}, @var{offset}, and @var{lm}.
41313 @var{thread-id} is the thread ID associated with the
41314 thread for which to fetch the TLS address. @xref{thread-id syntax}.
41316 @var{offset} is the (big endian, hex encoded) offset associated with the
41317 thread local variable. (This offset is obtained from the debug
41318 information associated with the variable.)
41320 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
41321 load module associated with the thread local storage. For example,
41322 a @sc{gnu}/Linux system will pass the link map address of the shared
41323 object associated with the thread local storage under consideration.
41324 Other operating environments may choose to represent the load module
41325 differently, so the precise meaning of this parameter will vary.
41329 @item @var{XX}@dots{}
41330 Hex encoded (big endian) bytes representing the address of the thread
41331 local storage requested.
41334 An error occurred. The error number @var{nn} is given as hex digits.
41337 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
41340 @item qGetTIBAddr:@var{thread-id}
41341 @cindex get thread information block address
41342 @cindex @samp{qGetTIBAddr} packet
41343 Fetch address of the Windows OS specific Thread Information Block.
41345 @var{thread-id} is the thread ID associated with the thread.
41349 @item @var{XX}@dots{}
41350 Hex encoded (big endian) bytes representing the linear address of the
41351 thread information block.
41354 An error occured. This means that either the thread was not found, or the
41355 address could not be retrieved.
41358 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
41361 @item qL @var{startflag} @var{threadcount} @var{nextthread}
41362 Obtain thread information from RTOS. Where: @var{startflag} (one hex
41363 digit) is one to indicate the first query and zero to indicate a
41364 subsequent query; @var{threadcount} (two hex digits) is the maximum
41365 number of threads the response packet can contain; and @var{nextthread}
41366 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
41367 returned in the response as @var{argthread}.
41369 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
41373 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
41374 Where: @var{count} (two hex digits) is the number of threads being
41375 returned; @var{done} (one hex digit) is zero to indicate more threads
41376 and one indicates no further threads; @var{argthreadid} (eight hex
41377 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
41378 is a sequence of thread IDs, @var{threadid} (eight hex
41379 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
41382 @item qMemTags:@var{start address},@var{length}:@var{type}
41384 @cindex fetch memory tags
41385 @cindex @samp{qMemTags} packet
41386 Fetch memory tags of type @var{type} from the address range
41387 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41388 target is responsible for calculating how many tags will be returned, as this
41389 is architecture-specific.
41391 @var{start address} is the starting address of the memory range.
41393 @var{length} is the length, in bytes, of the memory range.
41395 @var{type} is the type of tag the request wants to fetch. The type is a signed
41400 @item @var{mxx}@dots{}
41401 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
41402 tags found in the requested memory range.
41405 An error occured. This means that fetching of memory tags failed for some
41409 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
41410 although this should not happen given @value{GDBN} will only send this packet
41411 if the stub has advertised support for memory tagging via @samp{qSupported}.
41414 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
41416 @cindex store memory tags
41417 @cindex @samp{QMemTags} packet
41418 Store memory tags of type @var{type} to the address range
41419 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41420 target is responsible for interpreting the type, the tag bytes and modifying
41421 the memory tag granules accordingly, given this is architecture-specific.
41423 The interpretation of how many tags (@var{nt}) should be written to how many
41424 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
41425 implementation-specific, but the following is suggested.
41427 If the number of memory tags, @var{nt}, is greater than or equal to the
41428 number of memory tag granules, @var{ng}, only @var{ng} tags will be
41431 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
41432 and the tag bytes will be used as a pattern that will get repeated until
41433 @var{ng} tags are stored.
41435 @var{start address} is the starting address of the memory range. The address
41436 does not have any restriction on alignment or size.
41438 @var{length} is the length, in bytes, of the memory range.
41440 @var{type} is the type of tag the request wants to fetch. The type is a signed
41443 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
41444 interpreted by the target. Each pair of hex digits is interpreted as a
41450 The request was successful and the memory tag granules were modified
41454 An error occured. This means that modifying the memory tag granules failed
41458 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
41459 although this should not happen given @value{GDBN} will only send this packet
41460 if the stub has advertised support for memory tagging via @samp{qSupported}.
41464 @cindex section offsets, remote request
41465 @cindex @samp{qOffsets} packet
41466 Get section offsets that the target used when relocating the downloaded
41471 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
41472 Relocate the @code{Text} section by @var{xxx} from its original address.
41473 Relocate the @code{Data} section by @var{yyy} from its original address.
41474 If the object file format provides segment information (e.g.@: @sc{elf}
41475 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
41476 segments by the supplied offsets.
41478 @emph{Note: while a @code{Bss} offset may be included in the response,
41479 @value{GDBN} ignores this and instead applies the @code{Data} offset
41480 to the @code{Bss} section.}
41482 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
41483 Relocate the first segment of the object file, which conventionally
41484 contains program code, to a starting address of @var{xxx}. If
41485 @samp{DataSeg} is specified, relocate the second segment, which
41486 conventionally contains modifiable data, to a starting address of
41487 @var{yyy}. @value{GDBN} will report an error if the object file
41488 does not contain segment information, or does not contain at least
41489 as many segments as mentioned in the reply. Extra segments are
41490 kept at fixed offsets relative to the last relocated segment.
41493 @item qP @var{mode} @var{thread-id}
41494 @cindex thread information, remote request
41495 @cindex @samp{qP} packet
41496 Returns information on @var{thread-id}. Where: @var{mode} is a hex
41497 encoded 32 bit mode; @var{thread-id} is a thread ID
41498 (@pxref{thread-id syntax}).
41500 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
41503 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
41507 @cindex non-stop mode, remote request
41508 @cindex @samp{QNonStop} packet
41510 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
41511 @xref{Remote Non-Stop}, for more information.
41516 The request succeeded.
41519 An error occurred. The error number @var{nn} is given as hex digits.
41522 An empty reply indicates that @samp{QNonStop} is not supported by
41526 This packet is not probed by default; the remote stub must request it,
41527 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41528 Use of this packet is controlled by the @code{set non-stop} command;
41529 @pxref{Non-Stop Mode}.
41531 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
41532 @itemx QCatchSyscalls:0
41533 @cindex catch syscalls from inferior, remote request
41534 @cindex @samp{QCatchSyscalls} packet
41535 @anchor{QCatchSyscalls}
41536 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
41537 catching syscalls from the inferior process.
41539 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
41540 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
41541 is listed, every system call should be reported.
41543 Note that if a syscall not in the list is reported, @value{GDBN} will
41544 still filter the event according to its own list from all corresponding
41545 @code{catch syscall} commands. However, it is more efficient to only
41546 report the requested syscalls.
41548 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
41549 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
41551 If the inferior process execs, the state of @samp{QCatchSyscalls} is
41552 kept for the new process too. On targets where exec may affect syscall
41553 numbers, for example with exec between 32 and 64-bit processes, the
41554 client should send a new packet with the new syscall list.
41559 The request succeeded.
41562 An error occurred. @var{nn} are hex digits.
41565 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
41569 Use of this packet is controlled by the @code{set remote catch-syscalls}
41570 command (@pxref{Remote Configuration, set remote catch-syscalls}).
41571 This packet is not probed by default; the remote stub must request it,
41572 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41574 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41575 @cindex pass signals to inferior, remote request
41576 @cindex @samp{QPassSignals} packet
41577 @anchor{QPassSignals}
41578 Each listed @var{signal} should be passed directly to the inferior process.
41579 Signals are numbered identically to continue packets and stop replies
41580 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41581 strictly greater than the previous item. These signals do not need to stop
41582 the inferior, or be reported to @value{GDBN}. All other signals should be
41583 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
41584 combine; any earlier @samp{QPassSignals} list is completely replaced by the
41585 new list. This packet improves performance when using @samp{handle
41586 @var{signal} nostop noprint pass}.
41591 The request succeeded.
41594 An error occurred. The error number @var{nn} is given as hex digits.
41597 An empty reply indicates that @samp{QPassSignals} is not supported by
41601 Use of this packet is controlled by the @code{set remote pass-signals}
41602 command (@pxref{Remote Configuration, set remote pass-signals}).
41603 This packet is not probed by default; the remote stub must request it,
41604 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41606 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41607 @cindex signals the inferior may see, remote request
41608 @cindex @samp{QProgramSignals} packet
41609 @anchor{QProgramSignals}
41610 Each listed @var{signal} may be delivered to the inferior process.
41611 Others should be silently discarded.
41613 In some cases, the remote stub may need to decide whether to deliver a
41614 signal to the program or not without @value{GDBN} involvement. One
41615 example of that is while detaching --- the program's threads may have
41616 stopped for signals that haven't yet had a chance of being reported to
41617 @value{GDBN}, and so the remote stub can use the signal list specified
41618 by this packet to know whether to deliver or ignore those pending
41621 This does not influence whether to deliver a signal as requested by a
41622 resumption packet (@pxref{vCont packet}).
41624 Signals are numbered identically to continue packets and stop replies
41625 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41626 strictly greater than the previous item. Multiple
41627 @samp{QProgramSignals} packets do not combine; any earlier
41628 @samp{QProgramSignals} list is completely replaced by the new list.
41633 The request succeeded.
41636 An error occurred. The error number @var{nn} is given as hex digits.
41639 An empty reply indicates that @samp{QProgramSignals} is not supported
41643 Use of this packet is controlled by the @code{set remote program-signals}
41644 command (@pxref{Remote Configuration, set remote program-signals}).
41645 This packet is not probed by default; the remote stub must request it,
41646 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41648 @anchor{QThreadEvents}
41649 @item QThreadEvents:1
41650 @itemx QThreadEvents:0
41651 @cindex thread create/exit events, remote request
41652 @cindex @samp{QThreadEvents} packet
41654 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
41655 reporting of thread create and exit events. @xref{thread create
41656 event}, for the reply specifications. For example, this is used in
41657 non-stop mode when @value{GDBN} stops a set of threads and
41658 synchronously waits for the their corresponding stop replies. Without
41659 exit events, if one of the threads exits, @value{GDBN} would hang
41660 forever not knowing that it should no longer expect a stop for that
41661 same thread. @value{GDBN} does not enable this feature unless the
41662 stub reports that it supports it by including @samp{QThreadEvents+} in
41663 its @samp{qSupported} reply.
41668 The request succeeded.
41671 An error occurred. The error number @var{nn} is given as hex digits.
41674 An empty reply indicates that @samp{QThreadEvents} is not supported by
41678 Use of this packet is controlled by the @code{set remote thread-events}
41679 command (@pxref{Remote Configuration, set remote thread-events}).
41681 @item qRcmd,@var{command}
41682 @cindex execute remote command, remote request
41683 @cindex @samp{qRcmd} packet
41684 @var{command} (hex encoded) is passed to the local interpreter for
41685 execution. Invalid commands should be reported using the output
41686 string. Before the final result packet, the target may also respond
41687 with a number of intermediate @samp{O@var{output}} console output
41688 packets. @emph{Implementors should note that providing access to a
41689 stubs's interpreter may have security implications}.
41694 A command response with no output.
41696 A command response with the hex encoded output string @var{OUTPUT}.
41698 Indicate a badly formed request.
41700 An empty reply indicates that @samp{qRcmd} is not recognized.
41703 (Note that the @code{qRcmd} packet's name is separated from the
41704 command by a @samp{,}, not a @samp{:}, contrary to the naming
41705 conventions above. Please don't use this packet as a model for new
41708 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
41709 @cindex searching memory, in remote debugging
41711 @cindex @samp{qSearch:memory} packet
41713 @cindex @samp{qSearch memory} packet
41714 @anchor{qSearch memory}
41715 Search @var{length} bytes at @var{address} for @var{search-pattern}.
41716 Both @var{address} and @var{length} are encoded in hex;
41717 @var{search-pattern} is a sequence of bytes, also hex encoded.
41722 The pattern was not found.
41724 The pattern was found at @var{address}.
41726 A badly formed request or an error was encountered while searching memory.
41728 An empty reply indicates that @samp{qSearch:memory} is not recognized.
41731 @item QStartNoAckMode
41732 @cindex @samp{QStartNoAckMode} packet
41733 @anchor{QStartNoAckMode}
41734 Request that the remote stub disable the normal @samp{+}/@samp{-}
41735 protocol acknowledgments (@pxref{Packet Acknowledgment}).
41740 The stub has switched to no-acknowledgment mode.
41741 @value{GDBN} acknowledges this response,
41742 but neither the stub nor @value{GDBN} shall send or expect further
41743 @samp{+}/@samp{-} acknowledgments in the current connection.
41745 An empty reply indicates that the stub does not support no-acknowledgment mode.
41748 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
41749 @cindex supported packets, remote query
41750 @cindex features of the remote protocol
41751 @cindex @samp{qSupported} packet
41752 @anchor{qSupported}
41753 Tell the remote stub about features supported by @value{GDBN}, and
41754 query the stub for features it supports. This packet allows
41755 @value{GDBN} and the remote stub to take advantage of each others'
41756 features. @samp{qSupported} also consolidates multiple feature probes
41757 at startup, to improve @value{GDBN} performance---a single larger
41758 packet performs better than multiple smaller probe packets on
41759 high-latency links. Some features may enable behavior which must not
41760 be on by default, e.g.@: because it would confuse older clients or
41761 stubs. Other features may describe packets which could be
41762 automatically probed for, but are not. These features must be
41763 reported before @value{GDBN} will use them. This ``default
41764 unsupported'' behavior is not appropriate for all packets, but it
41765 helps to keep the initial connection time under control with new
41766 versions of @value{GDBN} which support increasing numbers of packets.
41770 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
41771 The stub supports or does not support each returned @var{stubfeature},
41772 depending on the form of each @var{stubfeature} (see below for the
41775 An empty reply indicates that @samp{qSupported} is not recognized,
41776 or that no features needed to be reported to @value{GDBN}.
41779 The allowed forms for each feature (either a @var{gdbfeature} in the
41780 @samp{qSupported} packet, or a @var{stubfeature} in the response)
41784 @item @var{name}=@var{value}
41785 The remote protocol feature @var{name} is supported, and associated
41786 with the specified @var{value}. The format of @var{value} depends
41787 on the feature, but it must not include a semicolon.
41789 The remote protocol feature @var{name} is supported, and does not
41790 need an associated value.
41792 The remote protocol feature @var{name} is not supported.
41794 The remote protocol feature @var{name} may be supported, and
41795 @value{GDBN} should auto-detect support in some other way when it is
41796 needed. This form will not be used for @var{gdbfeature} notifications,
41797 but may be used for @var{stubfeature} responses.
41800 Whenever the stub receives a @samp{qSupported} request, the
41801 supplied set of @value{GDBN} features should override any previous
41802 request. This allows @value{GDBN} to put the stub in a known
41803 state, even if the stub had previously been communicating with
41804 a different version of @value{GDBN}.
41806 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
41811 This feature indicates whether @value{GDBN} supports multiprocess
41812 extensions to the remote protocol. @value{GDBN} does not use such
41813 extensions unless the stub also reports that it supports them by
41814 including @samp{multiprocess+} in its @samp{qSupported} reply.
41815 @xref{multiprocess extensions}, for details.
41818 This feature indicates that @value{GDBN} supports the XML target
41819 description. If the stub sees @samp{xmlRegisters=} with target
41820 specific strings separated by a comma, it will report register
41824 This feature indicates whether @value{GDBN} supports the
41825 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
41826 instruction reply packet}).
41829 This feature indicates whether @value{GDBN} supports the swbreak stop
41830 reason in stop replies. @xref{swbreak stop reason}, for details.
41833 This feature indicates whether @value{GDBN} supports the hwbreak stop
41834 reason in stop replies. @xref{swbreak stop reason}, for details.
41837 This feature indicates whether @value{GDBN} supports fork event
41838 extensions to the remote protocol. @value{GDBN} does not use such
41839 extensions unless the stub also reports that it supports them by
41840 including @samp{fork-events+} in its @samp{qSupported} reply.
41843 This feature indicates whether @value{GDBN} supports vfork event
41844 extensions to the remote protocol. @value{GDBN} does not use such
41845 extensions unless the stub also reports that it supports them by
41846 including @samp{vfork-events+} in its @samp{qSupported} reply.
41849 This feature indicates whether @value{GDBN} supports exec event
41850 extensions to the remote protocol. @value{GDBN} does not use such
41851 extensions unless the stub also reports that it supports them by
41852 including @samp{exec-events+} in its @samp{qSupported} reply.
41854 @item vContSupported
41855 This feature indicates whether @value{GDBN} wants to know the
41856 supported actions in the reply to @samp{vCont?} packet.
41859 Stubs should ignore any unknown values for
41860 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
41861 packet supports receiving packets of unlimited length (earlier
41862 versions of @value{GDBN} may reject overly long responses). Additional values
41863 for @var{gdbfeature} may be defined in the future to let the stub take
41864 advantage of new features in @value{GDBN}, e.g.@: incompatible
41865 improvements in the remote protocol---the @samp{multiprocess} feature is
41866 an example of such a feature. The stub's reply should be independent
41867 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
41868 describes all the features it supports, and then the stub replies with
41869 all the features it supports.
41871 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
41872 responses, as long as each response uses one of the standard forms.
41874 Some features are flags. A stub which supports a flag feature
41875 should respond with a @samp{+} form response. Other features
41876 require values, and the stub should respond with an @samp{=}
41879 Each feature has a default value, which @value{GDBN} will use if
41880 @samp{qSupported} is not available or if the feature is not mentioned
41881 in the @samp{qSupported} response. The default values are fixed; a
41882 stub is free to omit any feature responses that match the defaults.
41884 Not all features can be probed, but for those which can, the probing
41885 mechanism is useful: in some cases, a stub's internal
41886 architecture may not allow the protocol layer to know some information
41887 about the underlying target in advance. This is especially common in
41888 stubs which may be configured for multiple targets.
41890 These are the currently defined stub features and their properties:
41892 @multitable @columnfractions 0.35 0.2 0.12 0.2
41893 @c NOTE: The first row should be @headitem, but we do not yet require
41894 @c a new enough version of Texinfo (4.7) to use @headitem.
41896 @tab Value Required
41900 @item @samp{PacketSize}
41905 @item @samp{qXfer:auxv:read}
41910 @item @samp{qXfer:btrace:read}
41915 @item @samp{qXfer:btrace-conf:read}
41920 @item @samp{qXfer:exec-file:read}
41925 @item @samp{qXfer:features:read}
41930 @item @samp{qXfer:libraries:read}
41935 @item @samp{qXfer:libraries-svr4:read}
41940 @item @samp{augmented-libraries-svr4-read}
41945 @item @samp{qXfer:memory-map:read}
41950 @item @samp{qXfer:sdata:read}
41955 @item @samp{qXfer:siginfo:read}
41960 @item @samp{qXfer:siginfo:write}
41965 @item @samp{qXfer:threads:read}
41970 @item @samp{qXfer:traceframe-info:read}
41975 @item @samp{qXfer:uib:read}
41980 @item @samp{qXfer:fdpic:read}
41985 @item @samp{Qbtrace:off}
41990 @item @samp{Qbtrace:bts}
41995 @item @samp{Qbtrace:pt}
42000 @item @samp{Qbtrace-conf:bts:size}
42005 @item @samp{Qbtrace-conf:pt:size}
42010 @item @samp{QNonStop}
42015 @item @samp{QCatchSyscalls}
42020 @item @samp{QPassSignals}
42025 @item @samp{QStartNoAckMode}
42030 @item @samp{multiprocess}
42035 @item @samp{ConditionalBreakpoints}
42040 @item @samp{ConditionalTracepoints}
42045 @item @samp{ReverseContinue}
42050 @item @samp{ReverseStep}
42055 @item @samp{TracepointSource}
42060 @item @samp{QAgent}
42065 @item @samp{QAllow}
42070 @item @samp{QDisableRandomization}
42075 @item @samp{EnableDisableTracepoints}
42080 @item @samp{QTBuffer:size}
42085 @item @samp{tracenz}
42090 @item @samp{BreakpointCommands}
42095 @item @samp{swbreak}
42100 @item @samp{hwbreak}
42105 @item @samp{fork-events}
42110 @item @samp{vfork-events}
42115 @item @samp{exec-events}
42120 @item @samp{QThreadEvents}
42125 @item @samp{no-resumed}
42130 @item @samp{memory-tagging}
42137 These are the currently defined stub features, in more detail:
42140 @cindex packet size, remote protocol
42141 @item PacketSize=@var{bytes}
42142 The remote stub can accept packets up to at least @var{bytes} in
42143 length. @value{GDBN} will send packets up to this size for bulk
42144 transfers, and will never send larger packets. This is a limit on the
42145 data characters in the packet, including the frame and checksum.
42146 There is no trailing NUL byte in a remote protocol packet; if the stub
42147 stores packets in a NUL-terminated format, it should allow an extra
42148 byte in its buffer for the NUL. If this stub feature is not supported,
42149 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42151 @item qXfer:auxv:read
42152 The remote stub understands the @samp{qXfer:auxv:read} packet
42153 (@pxref{qXfer auxiliary vector read}).
42155 @item qXfer:btrace:read
42156 The remote stub understands the @samp{qXfer:btrace:read}
42157 packet (@pxref{qXfer btrace read}).
42159 @item qXfer:btrace-conf:read
42160 The remote stub understands the @samp{qXfer:btrace-conf:read}
42161 packet (@pxref{qXfer btrace-conf read}).
42163 @item qXfer:exec-file:read
42164 The remote stub understands the @samp{qXfer:exec-file:read} packet
42165 (@pxref{qXfer executable filename read}).
42167 @item qXfer:features:read
42168 The remote stub understands the @samp{qXfer:features:read} packet
42169 (@pxref{qXfer target description read}).
42171 @item qXfer:libraries:read
42172 The remote stub understands the @samp{qXfer:libraries:read} packet
42173 (@pxref{qXfer library list read}).
42175 @item qXfer:libraries-svr4:read
42176 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42177 (@pxref{qXfer svr4 library list read}).
42179 @item augmented-libraries-svr4-read
42180 The remote stub understands the augmented form of the
42181 @samp{qXfer:libraries-svr4:read} packet
42182 (@pxref{qXfer svr4 library list read}).
42184 @item qXfer:memory-map:read
42185 The remote stub understands the @samp{qXfer:memory-map:read} packet
42186 (@pxref{qXfer memory map read}).
42188 @item qXfer:sdata:read
42189 The remote stub understands the @samp{qXfer:sdata:read} packet
42190 (@pxref{qXfer sdata read}).
42192 @item qXfer:siginfo:read
42193 The remote stub understands the @samp{qXfer:siginfo:read} packet
42194 (@pxref{qXfer siginfo read}).
42196 @item qXfer:siginfo:write
42197 The remote stub understands the @samp{qXfer:siginfo:write} packet
42198 (@pxref{qXfer siginfo write}).
42200 @item qXfer:threads:read
42201 The remote stub understands the @samp{qXfer:threads:read} packet
42202 (@pxref{qXfer threads read}).
42204 @item qXfer:traceframe-info:read
42205 The remote stub understands the @samp{qXfer:traceframe-info:read}
42206 packet (@pxref{qXfer traceframe info read}).
42208 @item qXfer:uib:read
42209 The remote stub understands the @samp{qXfer:uib:read}
42210 packet (@pxref{qXfer unwind info block}).
42212 @item qXfer:fdpic:read
42213 The remote stub understands the @samp{qXfer:fdpic:read}
42214 packet (@pxref{qXfer fdpic loadmap read}).
42217 The remote stub understands the @samp{QNonStop} packet
42218 (@pxref{QNonStop}).
42220 @item QCatchSyscalls
42221 The remote stub understands the @samp{QCatchSyscalls} packet
42222 (@pxref{QCatchSyscalls}).
42225 The remote stub understands the @samp{QPassSignals} packet
42226 (@pxref{QPassSignals}).
42228 @item QStartNoAckMode
42229 The remote stub understands the @samp{QStartNoAckMode} packet and
42230 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
42233 @anchor{multiprocess extensions}
42234 @cindex multiprocess extensions, in remote protocol
42235 The remote stub understands the multiprocess extensions to the remote
42236 protocol syntax. The multiprocess extensions affect the syntax of
42237 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
42238 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
42239 replies. Note that reporting this feature indicates support for the
42240 syntactic extensions only, not that the stub necessarily supports
42241 debugging of more than one process at a time. The stub must not use
42242 multiprocess extensions in packet replies unless @value{GDBN} has also
42243 indicated it supports them in its @samp{qSupported} request.
42245 @item qXfer:osdata:read
42246 The remote stub understands the @samp{qXfer:osdata:read} packet
42247 ((@pxref{qXfer osdata read}).
42249 @item ConditionalBreakpoints
42250 The target accepts and implements evaluation of conditional expressions
42251 defined for breakpoints. The target will only report breakpoint triggers
42252 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
42254 @item ConditionalTracepoints
42255 The remote stub accepts and implements conditional expressions defined
42256 for tracepoints (@pxref{Tracepoint Conditions}).
42258 @item ReverseContinue
42259 The remote stub accepts and implements the reverse continue packet
42263 The remote stub accepts and implements the reverse step packet
42266 @item TracepointSource
42267 The remote stub understands the @samp{QTDPsrc} packet that supplies
42268 the source form of tracepoint definitions.
42271 The remote stub understands the @samp{QAgent} packet.
42274 The remote stub understands the @samp{QAllow} packet.
42276 @item QDisableRandomization
42277 The remote stub understands the @samp{QDisableRandomization} packet.
42279 @item StaticTracepoint
42280 @cindex static tracepoints, in remote protocol
42281 The remote stub supports static tracepoints.
42283 @item InstallInTrace
42284 @anchor{install tracepoint in tracing}
42285 The remote stub supports installing tracepoint in tracing.
42287 @item EnableDisableTracepoints
42288 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
42289 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
42290 to be enabled and disabled while a trace experiment is running.
42292 @item QTBuffer:size
42293 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
42294 packet that allows to change the size of the trace buffer.
42297 @cindex string tracing, in remote protocol
42298 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
42299 See @ref{Bytecode Descriptions} for details about the bytecode.
42301 @item BreakpointCommands
42302 @cindex breakpoint commands, in remote protocol
42303 The remote stub supports running a breakpoint's command list itself,
42304 rather than reporting the hit to @value{GDBN}.
42307 The remote stub understands the @samp{Qbtrace:off} packet.
42310 The remote stub understands the @samp{Qbtrace:bts} packet.
42313 The remote stub understands the @samp{Qbtrace:pt} packet.
42315 @item Qbtrace-conf:bts:size
42316 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
42318 @item Qbtrace-conf:pt:size
42319 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
42322 The remote stub reports the @samp{swbreak} stop reason for memory
42326 The remote stub reports the @samp{hwbreak} stop reason for hardware
42330 The remote stub reports the @samp{fork} stop reason for fork events.
42333 The remote stub reports the @samp{vfork} stop reason for vfork events
42334 and vforkdone events.
42337 The remote stub reports the @samp{exec} stop reason for exec events.
42339 @item vContSupported
42340 The remote stub reports the supported actions in the reply to
42341 @samp{vCont?} packet.
42343 @item QThreadEvents
42344 The remote stub understands the @samp{QThreadEvents} packet.
42347 The remote stub reports the @samp{N} stop reply.
42350 @item memory-tagging
42351 The remote stub supports and implements the required memory tagging
42352 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
42353 @samp{QMemTags} (@pxref{QMemTags}) packets.
42355 For AArch64 GNU/Linux systems, this feature also requires access to the
42356 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
42357 This is done via the @samp{vFile} requests.
42362 @cindex symbol lookup, remote request
42363 @cindex @samp{qSymbol} packet
42364 Notify the target that @value{GDBN} is prepared to serve symbol lookup
42365 requests. Accept requests from the target for the values of symbols.
42370 The target does not need to look up any (more) symbols.
42371 @item qSymbol:@var{sym_name}
42372 The target requests the value of symbol @var{sym_name} (hex encoded).
42373 @value{GDBN} may provide the value by using the
42374 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
42378 @item qSymbol:@var{sym_value}:@var{sym_name}
42379 Set the value of @var{sym_name} to @var{sym_value}.
42381 @var{sym_name} (hex encoded) is the name of a symbol whose value the
42382 target has previously requested.
42384 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
42385 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
42391 The target does not need to look up any (more) symbols.
42392 @item qSymbol:@var{sym_name}
42393 The target requests the value of a new symbol @var{sym_name} (hex
42394 encoded). @value{GDBN} will continue to supply the values of symbols
42395 (if available), until the target ceases to request them.
42400 @itemx QTDisconnected
42407 @itemx qTMinFTPILen
42409 @xref{Tracepoint Packets}.
42411 @item qThreadExtraInfo,@var{thread-id}
42412 @cindex thread attributes info, remote request
42413 @cindex @samp{qThreadExtraInfo} packet
42414 Obtain from the target OS a printable string description of thread
42415 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
42416 for the forms of @var{thread-id}. This
42417 string may contain anything that the target OS thinks is interesting
42418 for @value{GDBN} to tell the user about the thread. The string is
42419 displayed in @value{GDBN}'s @code{info threads} display. Some
42420 examples of possible thread extra info strings are @samp{Runnable}, or
42421 @samp{Blocked on Mutex}.
42425 @item @var{XX}@dots{}
42426 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
42427 comprising the printable string containing the extra information about
42428 the thread's attributes.
42431 (Note that the @code{qThreadExtraInfo} packet's name is separated from
42432 the command by a @samp{,}, not a @samp{:}, contrary to the naming
42433 conventions above. Please don't use this packet as a model for new
42452 @xref{Tracepoint Packets}.
42454 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
42455 @cindex read special object, remote request
42456 @cindex @samp{qXfer} packet
42457 @anchor{qXfer read}
42458 Read uninterpreted bytes from the target's special data area
42459 identified by the keyword @var{object}. Request @var{length} bytes
42460 starting at @var{offset} bytes into the data. The content and
42461 encoding of @var{annex} is specific to @var{object}; it can supply
42462 additional details about what data to access.
42467 Data @var{data} (@pxref{Binary Data}) has been read from the
42468 target. There may be more data at a higher address (although
42469 it is permitted to return @samp{m} even for the last valid
42470 block of data, as long as at least one byte of data was read).
42471 It is possible for @var{data} to have fewer bytes than the @var{length} in the
42475 Data @var{data} (@pxref{Binary Data}) has been read from the target.
42476 There is no more data to be read. It is possible for @var{data} to
42477 have fewer bytes than the @var{length} in the request.
42480 The @var{offset} in the request is at the end of the data.
42481 There is no more data to be read.
42484 The request was malformed, or @var{annex} was invalid.
42487 The offset was invalid, or there was an error encountered reading the data.
42488 The @var{nn} part is a hex-encoded @code{errno} value.
42491 An empty reply indicates the @var{object} string was not recognized by
42492 the stub, or that the object does not support reading.
42495 Here are the specific requests of this form defined so far. All the
42496 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
42497 formats, listed above.
42500 @item qXfer:auxv:read::@var{offset},@var{length}
42501 @anchor{qXfer auxiliary vector read}
42502 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
42503 auxiliary vector}. Note @var{annex} must be empty.
42505 This packet is not probed by default; the remote stub must request it,
42506 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42508 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
42509 @anchor{qXfer btrace read}
42511 Return a description of the current branch trace.
42512 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
42513 packet may have one of the following values:
42517 Returns all available branch trace.
42520 Returns all available branch trace if the branch trace changed since
42521 the last read request.
42524 Returns the new branch trace since the last read request. Adds a new
42525 block to the end of the trace that begins at zero and ends at the source
42526 location of the first branch in the trace buffer. This extra block is
42527 used to stitch traces together.
42529 If the trace buffer overflowed, returns an error indicating the overflow.
42532 This packet is not probed by default; the remote stub must request it
42533 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42535 @item qXfer:btrace-conf:read::@var{offset},@var{length}
42536 @anchor{qXfer btrace-conf read}
42538 Return a description of the current branch trace configuration.
42539 @xref{Branch Trace Configuration Format}.
42541 This packet is not probed by default; the remote stub must request it
42542 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42544 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
42545 @anchor{qXfer executable filename read}
42546 Return the full absolute name of the file that was executed to create
42547 a process running on the remote system. The annex specifies the
42548 numeric process ID of the process to query, encoded as a hexadecimal
42549 number. If the annex part is empty the remote stub should return the
42550 filename corresponding to the currently executing process.
42552 This packet is not probed by default; the remote stub must request it,
42553 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42555 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
42556 @anchor{qXfer target description read}
42557 Access the @dfn{target description}. @xref{Target Descriptions}. The
42558 annex specifies which XML document to access. The main description is
42559 always loaded from the @samp{target.xml} annex.
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 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
42565 @anchor{qXfer library list read}
42566 Access the target's list of loaded libraries. @xref{Library List Format}.
42567 The annex part of the generic @samp{qXfer} packet must be empty
42568 (@pxref{qXfer read}).
42570 Targets which maintain a list of libraries in the program's memory do
42571 not need to implement this packet; it is designed for platforms where
42572 the operating system manages the list of loaded libraries.
42574 This packet is not probed by default; the remote stub must request it,
42575 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42577 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
42578 @anchor{qXfer svr4 library list read}
42579 Access the target's list of loaded libraries when the target is an SVR4
42580 platform. @xref{Library List Format for SVR4 Targets}. The annex part
42581 of the generic @samp{qXfer} packet must be empty unless the remote
42582 stub indicated it supports the augmented form of this packet
42583 by supplying an appropriate @samp{qSupported} response
42584 (@pxref{qXfer read}, @ref{qSupported}).
42586 This packet is optional for better performance on SVR4 targets.
42587 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
42589 This packet is not probed by default; the remote stub must request it,
42590 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42592 If the remote stub indicates it supports the augmented form of this
42593 packet then the annex part of the generic @samp{qXfer} packet may
42594 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
42595 arguments. The currently supported arguments are:
42598 @item start=@var{address}
42599 A hexadecimal number specifying the address of the @samp{struct
42600 link_map} to start reading the library list from. If unset or zero
42601 then the first @samp{struct link_map} in the library list will be
42602 chosen as the starting point.
42604 @item prev=@var{address}
42605 A hexadecimal number specifying the address of the @samp{struct
42606 link_map} immediately preceding the @samp{struct link_map}
42607 specified by the @samp{start} argument. If unset or zero then
42608 the remote stub will expect that no @samp{struct link_map}
42609 exists prior to the starting point.
42613 Arguments that are not understood by the remote stub will be silently
42616 @item qXfer:memory-map:read::@var{offset},@var{length}
42617 @anchor{qXfer memory map read}
42618 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
42619 annex part of the generic @samp{qXfer} packet must be empty
42620 (@pxref{qXfer read}).
42622 This packet is not probed by default; the remote stub must request it,
42623 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42625 @item qXfer:sdata:read::@var{offset},@var{length}
42626 @anchor{qXfer sdata read}
42628 Read contents of the extra collected static tracepoint marker
42629 information. The annex part of the generic @samp{qXfer} packet must
42630 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
42633 This packet is not probed by default; the remote stub must request it,
42634 by supplying an appropriate @samp{qSupported} response
42635 (@pxref{qSupported}).
42637 @item qXfer:siginfo:read::@var{offset},@var{length}
42638 @anchor{qXfer siginfo read}
42639 Read contents of the extra signal information on the target
42640 system. The annex part of the generic @samp{qXfer} packet must be
42641 empty (@pxref{qXfer read}).
42643 This packet is not probed by default; the remote stub must request it,
42644 by supplying an appropriate @samp{qSupported} response
42645 (@pxref{qSupported}).
42647 @item qXfer:threads:read::@var{offset},@var{length}
42648 @anchor{qXfer threads read}
42649 Access the list of threads on target. @xref{Thread List Format}. The
42650 annex part of the generic @samp{qXfer} packet must be empty
42651 (@pxref{qXfer read}).
42653 This packet is not probed by default; the remote stub must request it,
42654 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42656 @item qXfer:traceframe-info:read::@var{offset},@var{length}
42657 @anchor{qXfer traceframe info read}
42659 Return a description of the current traceframe's contents.
42660 @xref{Traceframe Info Format}. The annex part of the generic
42661 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
42663 This packet is not probed by default; the remote stub must request it,
42664 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42666 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
42667 @anchor{qXfer unwind info block}
42669 Return the unwind information block for @var{pc}. This packet is used
42670 on OpenVMS/ia64 to ask the kernel unwind information.
42672 This packet is not probed by default.
42674 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
42675 @anchor{qXfer fdpic loadmap read}
42676 Read contents of @code{loadmap}s on the target system. The
42677 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
42678 executable @code{loadmap} or interpreter @code{loadmap} to read.
42680 This packet is not probed by default; the remote stub must request it,
42681 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42683 @item qXfer:osdata:read::@var{offset},@var{length}
42684 @anchor{qXfer osdata read}
42685 Access the target's @dfn{operating system information}.
42686 @xref{Operating System Information}.
42690 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
42691 @cindex write data into object, remote request
42692 @anchor{qXfer write}
42693 Write uninterpreted bytes into the target's special data area
42694 identified by the keyword @var{object}, starting at @var{offset} bytes
42695 into the data. The binary-encoded data (@pxref{Binary Data}) to be
42696 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
42697 is specific to @var{object}; it can supply additional details about what data
42703 @var{nn} (hex encoded) is the number of bytes written.
42704 This may be fewer bytes than supplied in the request.
42707 The request was malformed, or @var{annex} was invalid.
42710 The offset was invalid, or there was an error encountered writing the data.
42711 The @var{nn} part is a hex-encoded @code{errno} value.
42714 An empty reply indicates the @var{object} string was not
42715 recognized by the stub, or that the object does not support writing.
42718 Here are the specific requests of this form defined so far. All the
42719 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
42720 formats, listed above.
42723 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
42724 @anchor{qXfer siginfo write}
42725 Write @var{data} to the extra signal information on the target system.
42726 The annex part of the generic @samp{qXfer} packet must be
42727 empty (@pxref{qXfer write}).
42729 This packet is not probed by default; the remote stub must request it,
42730 by supplying an appropriate @samp{qSupported} response
42731 (@pxref{qSupported}).
42734 @item qXfer:@var{object}:@var{operation}:@dots{}
42735 Requests of this form may be added in the future. When a stub does
42736 not recognize the @var{object} keyword, or its support for
42737 @var{object} does not recognize the @var{operation} keyword, the stub
42738 must respond with an empty packet.
42740 @item qAttached:@var{pid}
42741 @cindex query attached, remote request
42742 @cindex @samp{qAttached} packet
42743 Return an indication of whether the remote server attached to an
42744 existing process or created a new process. When the multiprocess
42745 protocol extensions are supported (@pxref{multiprocess extensions}),
42746 @var{pid} is an integer in hexadecimal format identifying the target
42747 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
42748 the query packet will be simplified as @samp{qAttached}.
42750 This query is used, for example, to know whether the remote process
42751 should be detached or killed when a @value{GDBN} session is ended with
42752 the @code{quit} command.
42757 The remote server attached to an existing process.
42759 The remote server created a new process.
42761 A badly formed request or an error was encountered.
42765 Enable branch tracing for the current thread using Branch Trace Store.
42770 Branch tracing has been enabled.
42772 A badly formed request or an error was encountered.
42776 Enable branch tracing for the current thread using Intel Processor Trace.
42781 Branch tracing has been enabled.
42783 A badly formed request or an error was encountered.
42787 Disable branch tracing for the current thread.
42792 Branch tracing has been disabled.
42794 A badly formed request or an error was encountered.
42797 @item Qbtrace-conf:bts:size=@var{value}
42798 Set the requested ring buffer size for new threads that use the
42799 btrace recording method in bts format.
42804 The ring buffer size has been set.
42806 A badly formed request or an error was encountered.
42809 @item Qbtrace-conf:pt:size=@var{value}
42810 Set the requested ring buffer size for new threads that use the
42811 btrace recording method in pt format.
42816 The ring buffer size has been set.
42818 A badly formed request or an error was encountered.
42823 @node Architecture-Specific Protocol Details
42824 @section Architecture-Specific Protocol Details
42826 This section describes how the remote protocol is applied to specific
42827 target architectures. Also see @ref{Standard Target Features}, for
42828 details of XML target descriptions for each architecture.
42831 * ARM-Specific Protocol Details::
42832 * MIPS-Specific Protocol Details::
42835 @node ARM-Specific Protocol Details
42836 @subsection @acronym{ARM}-specific Protocol Details
42839 * ARM Breakpoint Kinds::
42840 * ARM Memory Tag Types::
42843 @node ARM Breakpoint Kinds
42844 @subsubsection @acronym{ARM} Breakpoint Kinds
42845 @cindex breakpoint kinds, @acronym{ARM}
42847 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42852 16-bit Thumb mode breakpoint.
42855 32-bit Thumb mode (Thumb-2) breakpoint.
42858 32-bit @acronym{ARM} mode breakpoint.
42862 @node ARM Memory Tag Types
42863 @subsubsection @acronym{ARM} Memory Tag Types
42864 @cindex memory tag types, @acronym{ARM}
42866 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
42879 @node MIPS-Specific Protocol Details
42880 @subsection @acronym{MIPS}-specific Protocol Details
42883 * MIPS Register packet Format::
42884 * MIPS Breakpoint Kinds::
42887 @node MIPS Register packet Format
42888 @subsubsection @acronym{MIPS} Register Packet Format
42889 @cindex register packet format, @acronym{MIPS}
42891 The following @code{g}/@code{G} packets have previously been defined.
42892 In the below, some thirty-two bit registers are transferred as
42893 sixty-four bits. Those registers should be zero/sign extended (which?)
42894 to fill the space allocated. Register bytes are transferred in target
42895 byte order. The two nibbles within a register byte are transferred
42896 most-significant -- least-significant.
42901 All registers are transferred as thirty-two bit quantities in the order:
42902 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
42903 registers; fsr; fir; fp.
42906 All registers are transferred as sixty-four bit quantities (including
42907 thirty-two bit registers such as @code{sr}). The ordering is the same
42912 @node MIPS Breakpoint Kinds
42913 @subsubsection @acronym{MIPS} Breakpoint Kinds
42914 @cindex breakpoint kinds, @acronym{MIPS}
42916 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42921 16-bit @acronym{MIPS16} mode breakpoint.
42924 16-bit @acronym{microMIPS} mode breakpoint.
42927 32-bit standard @acronym{MIPS} mode breakpoint.
42930 32-bit @acronym{microMIPS} mode breakpoint.
42934 @node Tracepoint Packets
42935 @section Tracepoint Packets
42936 @cindex tracepoint packets
42937 @cindex packets, tracepoint
42939 Here we describe the packets @value{GDBN} uses to implement
42940 tracepoints (@pxref{Tracepoints}).
42944 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
42945 @cindex @samp{QTDP} packet
42946 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
42947 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
42948 the tracepoint is disabled. The @var{step} gives the tracepoint's step
42949 count, and @var{pass} gives its pass count. If an @samp{F} is present,
42950 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
42951 the number of bytes that the target should copy elsewhere to make room
42952 for the tracepoint. If an @samp{X} is present, it introduces a
42953 tracepoint condition, which consists of a hexadecimal length, followed
42954 by a comma and hex-encoded bytes, in a manner similar to action
42955 encodings as described below. If the trailing @samp{-} is present,
42956 further @samp{QTDP} packets will follow to specify this tracepoint's
42962 The packet was understood and carried out.
42964 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42966 The packet was not recognized.
42969 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
42970 Define actions to be taken when a tracepoint is hit. The @var{n} and
42971 @var{addr} must be the same as in the initial @samp{QTDP} packet for
42972 this tracepoint. This packet may only be sent immediately after
42973 another @samp{QTDP} packet that ended with a @samp{-}. If the
42974 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
42975 specifying more actions for this tracepoint.
42977 In the series of action packets for a given tracepoint, at most one
42978 can have an @samp{S} before its first @var{action}. If such a packet
42979 is sent, it and the following packets define ``while-stepping''
42980 actions. Any prior packets define ordinary actions --- that is, those
42981 taken when the tracepoint is first hit. If no action packet has an
42982 @samp{S}, then all the packets in the series specify ordinary
42983 tracepoint actions.
42985 The @samp{@var{action}@dots{}} portion of the packet is a series of
42986 actions, concatenated without separators. Each action has one of the
42992 Collect the registers whose bits are set in @var{mask},
42993 a hexadecimal number whose @var{i}'th bit is set if register number
42994 @var{i} should be collected. (The least significant bit is numbered
42995 zero.) Note that @var{mask} may be any number of digits long; it may
42996 not fit in a 32-bit word.
42998 @item M @var{basereg},@var{offset},@var{len}
42999 Collect @var{len} bytes of memory starting at the address in register
43000 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43001 @samp{-1}, then the range has a fixed address: @var{offset} is the
43002 address of the lowest byte to collect. The @var{basereg},
43003 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43004 values (the @samp{-1} value for @var{basereg} is a special case).
43006 @item X @var{len},@var{expr}
43007 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43008 it directs. The agent expression @var{expr} is as described in
43009 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43010 two-digit hex number in the packet; @var{len} is the number of bytes
43011 in the expression (and thus one-half the number of hex digits in the
43016 Any number of actions may be packed together in a single @samp{QTDP}
43017 packet, as long as the packet does not exceed the maximum packet
43018 length (400 bytes, for many stubs). There may be only one @samp{R}
43019 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43020 actions. Any registers referred to by @samp{M} and @samp{X} actions
43021 must be collected by a preceding @samp{R} action. (The
43022 ``while-stepping'' actions are treated as if they were attached to a
43023 separate tracepoint, as far as these restrictions are concerned.)
43028 The packet was understood and carried out.
43030 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43032 The packet was not recognized.
43035 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43036 @cindex @samp{QTDPsrc} packet
43037 Specify a source string of tracepoint @var{n} at address @var{addr}.
43038 This is useful to get accurate reproduction of the tracepoints
43039 originally downloaded at the beginning of the trace run. The @var{type}
43040 is the name of the tracepoint part, such as @samp{cond} for the
43041 tracepoint's conditional expression (see below for a list of types), while
43042 @var{bytes} is the string, encoded in hexadecimal.
43044 @var{start} is the offset of the @var{bytes} within the overall source
43045 string, while @var{slen} is the total length of the source string.
43046 This is intended for handling source strings that are longer than will
43047 fit in a single packet.
43048 @c Add detailed example when this info is moved into a dedicated
43049 @c tracepoint descriptions section.
43051 The available string types are @samp{at} for the location,
43052 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43053 @value{GDBN} sends a separate packet for each command in the action
43054 list, in the same order in which the commands are stored in the list.
43056 The target does not need to do anything with source strings except
43057 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43060 Although this packet is optional, and @value{GDBN} will only send it
43061 if the target replies with @samp{TracepointSource} @xref{General
43062 Query Packets}, it makes both disconnected tracing and trace files
43063 much easier to use. Otherwise the user must be careful that the
43064 tracepoints in effect while looking at trace frames are identical to
43065 the ones in effect during the trace run; even a small discrepancy
43066 could cause @samp{tdump} not to work, or a particular trace frame not
43069 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43070 @cindex define trace state variable, remote request
43071 @cindex @samp{QTDV} packet
43072 Create a new trace state variable, number @var{n}, with an initial
43073 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43074 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43075 the option of not using this packet for initial values of zero; the
43076 target should simply create the trace state variables as they are
43077 mentioned in expressions. The value @var{builtin} should be 1 (one)
43078 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43079 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43080 @samp{qTsV} packet had it set. The contents of @var{name} is the
43081 hex-encoded name (without the leading @samp{$}) of the trace state
43084 @item QTFrame:@var{n}
43085 @cindex @samp{QTFrame} packet
43086 Select the @var{n}'th tracepoint frame from the buffer, and use the
43087 register and memory contents recorded there to answer subsequent
43088 request packets from @value{GDBN}.
43090 A successful reply from the stub indicates that the stub has found the
43091 requested frame. The response is a series of parts, concatenated
43092 without separators, describing the frame we selected. Each part has
43093 one of the following forms:
43097 The selected frame is number @var{n} in the trace frame buffer;
43098 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43099 was no frame matching the criteria in the request packet.
43102 The selected trace frame records a hit of tracepoint number @var{t};
43103 @var{t} is a hexadecimal number.
43107 @item QTFrame:pc:@var{addr}
43108 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43109 currently selected frame whose PC is @var{addr};
43110 @var{addr} is a hexadecimal number.
43112 @item QTFrame:tdp:@var{t}
43113 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43114 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43115 is a hexadecimal number.
43117 @item QTFrame:range:@var{start}:@var{end}
43118 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43119 currently selected frame whose PC is between @var{start} (inclusive)
43120 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43123 @item QTFrame:outside:@var{start}:@var{end}
43124 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43125 frame @emph{outside} the given range of addresses (exclusive).
43128 @cindex @samp{qTMinFTPILen} packet
43129 This packet requests the minimum length of instruction at which a fast
43130 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43131 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43132 it depends on the target system being able to create trampolines in
43133 the first 64K of memory, which might or might not be possible for that
43134 system. So the reply to this packet will be 4 if it is able to
43141 The minimum instruction length is currently unknown.
43143 The minimum instruction length is @var{length}, where @var{length}
43144 is a hexadecimal number greater or equal to 1. A reply
43145 of 1 means that a fast tracepoint may be placed on any instruction
43146 regardless of size.
43148 An error has occurred.
43150 An empty reply indicates that the request is not supported by the stub.
43154 @cindex @samp{QTStart} packet
43155 Begin the tracepoint experiment. Begin collecting data from
43156 tracepoint hits in the trace frame buffer. This packet supports the
43157 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43158 instruction reply packet}).
43161 @cindex @samp{QTStop} packet
43162 End the tracepoint experiment. Stop collecting trace frames.
43164 @item QTEnable:@var{n}:@var{addr}
43166 @cindex @samp{QTEnable} packet
43167 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43168 experiment. If the tracepoint was previously disabled, then collection
43169 of data from it will resume.
43171 @item QTDisable:@var{n}:@var{addr}
43173 @cindex @samp{QTDisable} packet
43174 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43175 experiment. No more data will be collected from the tracepoint unless
43176 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43179 @cindex @samp{QTinit} packet
43180 Clear the table of tracepoints, and empty the trace frame buffer.
43182 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43183 @cindex @samp{QTro} packet
43184 Establish the given ranges of memory as ``transparent''. The stub
43185 will answer requests for these ranges from memory's current contents,
43186 if they were not collected as part of the tracepoint hit.
43188 @value{GDBN} uses this to mark read-only regions of memory, like those
43189 containing program code. Since these areas never change, they should
43190 still have the same contents they did when the tracepoint was hit, so
43191 there's no reason for the stub to refuse to provide their contents.
43193 @item QTDisconnected:@var{value}
43194 @cindex @samp{QTDisconnected} packet
43195 Set the choice to what to do with the tracing run when @value{GDBN}
43196 disconnects from the target. A @var{value} of 1 directs the target to
43197 continue the tracing run, while 0 tells the target to stop tracing if
43198 @value{GDBN} is no longer in the picture.
43201 @cindex @samp{qTStatus} packet
43202 Ask the stub if there is a trace experiment running right now.
43204 The reply has the form:
43208 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
43209 @var{running} is a single digit @code{1} if the trace is presently
43210 running, or @code{0} if not. It is followed by semicolon-separated
43211 optional fields that an agent may use to report additional status.
43215 If the trace is not running, the agent may report any of several
43216 explanations as one of the optional fields:
43221 No trace has been run yet.
43223 @item tstop[:@var{text}]:0
43224 The trace was stopped by a user-originated stop command. The optional
43225 @var{text} field is a user-supplied string supplied as part of the
43226 stop command (for instance, an explanation of why the trace was
43227 stopped manually). It is hex-encoded.
43230 The trace stopped because the trace buffer filled up.
43232 @item tdisconnected:0
43233 The trace stopped because @value{GDBN} disconnected from the target.
43235 @item tpasscount:@var{tpnum}
43236 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
43238 @item terror:@var{text}:@var{tpnum}
43239 The trace stopped because tracepoint @var{tpnum} had an error. The
43240 string @var{text} is available to describe the nature of the error
43241 (for instance, a divide by zero in the condition expression); it
43245 The trace stopped for some other reason.
43249 Additional optional fields supply statistical and other information.
43250 Although not required, they are extremely useful for users monitoring
43251 the progress of a trace run. If a trace has stopped, and these
43252 numbers are reported, they must reflect the state of the just-stopped
43257 @item tframes:@var{n}
43258 The number of trace frames in the buffer.
43260 @item tcreated:@var{n}
43261 The total number of trace frames created during the run. This may
43262 be larger than the trace frame count, if the buffer is circular.
43264 @item tsize:@var{n}
43265 The total size of the trace buffer, in bytes.
43267 @item tfree:@var{n}
43268 The number of bytes still unused in the buffer.
43270 @item circular:@var{n}
43271 The value of the circular trace buffer flag. @code{1} means that the
43272 trace buffer is circular and old trace frames will be discarded if
43273 necessary to make room, @code{0} means that the trace buffer is linear
43276 @item disconn:@var{n}
43277 The value of the disconnected tracing flag. @code{1} means that
43278 tracing will continue after @value{GDBN} disconnects, @code{0} means
43279 that the trace run will stop.
43283 @item qTP:@var{tp}:@var{addr}
43284 @cindex tracepoint status, remote request
43285 @cindex @samp{qTP} packet
43286 Ask the stub for the current state of tracepoint number @var{tp} at
43287 address @var{addr}.
43291 @item V@var{hits}:@var{usage}
43292 The tracepoint has been hit @var{hits} times so far during the trace
43293 run, and accounts for @var{usage} in the trace buffer. Note that
43294 @code{while-stepping} steps are not counted as separate hits, but the
43295 steps' space consumption is added into the usage number.
43299 @item qTV:@var{var}
43300 @cindex trace state variable value, remote request
43301 @cindex @samp{qTV} packet
43302 Ask the stub for the value of the trace state variable number @var{var}.
43307 The value of the variable is @var{value}. This will be the current
43308 value of the variable if the user is examining a running target, or a
43309 saved value if the variable was collected in the trace frame that the
43310 user is looking at. Note that multiple requests may result in
43311 different reply values, such as when requesting values while the
43312 program is running.
43315 The value of the variable is unknown. This would occur, for example,
43316 if the user is examining a trace frame in which the requested variable
43321 @cindex @samp{qTfP} packet
43323 @cindex @samp{qTsP} packet
43324 These packets request data about tracepoints that are being used by
43325 the target. @value{GDBN} sends @code{qTfP} to get the first piece
43326 of data, and multiple @code{qTsP} to get additional pieces. Replies
43327 to these packets generally take the form of the @code{QTDP} packets
43328 that define tracepoints. (FIXME add detailed syntax)
43331 @cindex @samp{qTfV} packet
43333 @cindex @samp{qTsV} packet
43334 These packets request data about trace state variables that are on the
43335 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
43336 and multiple @code{qTsV} to get additional variables. Replies to
43337 these packets follow the syntax of the @code{QTDV} packets that define
43338 trace state variables.
43344 @cindex @samp{qTfSTM} packet
43345 @cindex @samp{qTsSTM} packet
43346 These packets request data about static tracepoint markers that exist
43347 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
43348 first piece of data, and multiple @code{qTsSTM} to get additional
43349 pieces. Replies to these packets take the following form:
43353 @item m @var{address}:@var{id}:@var{extra}
43355 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
43356 a comma-separated list of markers
43358 (lower case letter @samp{L}) denotes end of list.
43360 An error occurred. The error number @var{nn} is given as hex digits.
43362 An empty reply indicates that the request is not supported by the
43366 The @var{address} is encoded in hex;
43367 @var{id} and @var{extra} are strings encoded in hex.
43369 In response to each query, the target will reply with a list of one or
43370 more markers, separated by commas. @value{GDBN} will respond to each
43371 reply with a request for more markers (using the @samp{qs} form of the
43372 query), until the target responds with @samp{l} (lower-case ell, for
43375 @item qTSTMat:@var{address}
43377 @cindex @samp{qTSTMat} packet
43378 This packets requests data about static tracepoint markers in the
43379 target program at @var{address}. Replies to this packet follow the
43380 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
43381 tracepoint markers.
43383 @item QTSave:@var{filename}
43384 @cindex @samp{QTSave} packet
43385 This packet directs the target to save trace data to the file name
43386 @var{filename} in the target's filesystem. The @var{filename} is encoded
43387 as a hex string; the interpretation of the file name (relative vs
43388 absolute, wild cards, etc) is up to the target.
43390 @item qTBuffer:@var{offset},@var{len}
43391 @cindex @samp{qTBuffer} packet
43392 Return up to @var{len} bytes of the current contents of trace buffer,
43393 starting at @var{offset}. The trace buffer is treated as if it were
43394 a contiguous collection of traceframes, as per the trace file format.
43395 The reply consists as many hex-encoded bytes as the target can deliver
43396 in a packet; it is not an error to return fewer than were asked for.
43397 A reply consisting of just @code{l} indicates that no bytes are
43400 @item QTBuffer:circular:@var{value}
43401 This packet directs the target to use a circular trace buffer if
43402 @var{value} is 1, or a linear buffer if the value is 0.
43404 @item QTBuffer:size:@var{size}
43405 @anchor{QTBuffer-size}
43406 @cindex @samp{QTBuffer size} packet
43407 This packet directs the target to make the trace buffer be of size
43408 @var{size} if possible. A value of @code{-1} tells the target to
43409 use whatever size it prefers.
43411 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
43412 @cindex @samp{QTNotes} packet
43413 This packet adds optional textual notes to the trace run. Allowable
43414 types include @code{user}, @code{notes}, and @code{tstop}, the
43415 @var{text} fields are arbitrary strings, hex-encoded.
43419 @subsection Relocate instruction reply packet
43420 When installing fast tracepoints in memory, the target may need to
43421 relocate the instruction currently at the tracepoint address to a
43422 different address in memory. For most instructions, a simple copy is
43423 enough, but, for example, call instructions that implicitly push the
43424 return address on the stack, and relative branches or other
43425 PC-relative instructions require offset adjustment, so that the effect
43426 of executing the instruction at a different address is the same as if
43427 it had executed in the original location.
43429 In response to several of the tracepoint packets, the target may also
43430 respond with a number of intermediate @samp{qRelocInsn} request
43431 packets before the final result packet, to have @value{GDBN} handle
43432 this relocation operation. If a packet supports this mechanism, its
43433 documentation will explicitly say so. See for example the above
43434 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
43435 format of the request is:
43438 @item qRelocInsn:@var{from};@var{to}
43440 This requests @value{GDBN} to copy instruction at address @var{from}
43441 to address @var{to}, possibly adjusted so that executing the
43442 instruction at @var{to} has the same effect as executing it at
43443 @var{from}. @value{GDBN} writes the adjusted instruction to target
43444 memory starting at @var{to}.
43449 @item qRelocInsn:@var{adjusted_size}
43450 Informs the stub the relocation is complete. The @var{adjusted_size} is
43451 the length in bytes of resulting relocated instruction sequence.
43453 A badly formed request was detected, or an error was encountered while
43454 relocating the instruction.
43457 @node Host I/O Packets
43458 @section Host I/O Packets
43459 @cindex Host I/O, remote protocol
43460 @cindex file transfer, remote protocol
43462 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
43463 operations on the far side of a remote link. For example, Host I/O is
43464 used to upload and download files to a remote target with its own
43465 filesystem. Host I/O uses the same constant values and data structure
43466 layout as the target-initiated File-I/O protocol. However, the
43467 Host I/O packets are structured differently. The target-initiated
43468 protocol relies on target memory to store parameters and buffers.
43469 Host I/O requests are initiated by @value{GDBN}, and the
43470 target's memory is not involved. @xref{File-I/O Remote Protocol
43471 Extension}, for more details on the target-initiated protocol.
43473 The Host I/O request packets all encode a single operation along with
43474 its arguments. They have this format:
43478 @item vFile:@var{operation}: @var{parameter}@dots{}
43479 @var{operation} is the name of the particular request; the target
43480 should compare the entire packet name up to the second colon when checking
43481 for a supported operation. The format of @var{parameter} depends on
43482 the operation. Numbers are always passed in hexadecimal. Negative
43483 numbers have an explicit minus sign (i.e.@: two's complement is not
43484 used). Strings (e.g.@: filenames) are encoded as a series of
43485 hexadecimal bytes. The last argument to a system call may be a
43486 buffer of escaped binary data (@pxref{Binary Data}).
43490 The valid responses to Host I/O packets are:
43494 @item F @var{result} [, @var{errno}] [; @var{attachment}]
43495 @var{result} is the integer value returned by this operation, usually
43496 non-negative for success and -1 for errors. If an error has occured,
43497 @var{errno} will be included in the result specifying a
43498 value defined by the File-I/O protocol (@pxref{Errno Values}). For
43499 operations which return data, @var{attachment} supplies the data as a
43500 binary buffer. Binary buffers in response packets are escaped in the
43501 normal way (@pxref{Binary Data}). See the individual packet
43502 documentation for the interpretation of @var{result} and
43506 An empty response indicates that this operation is not recognized.
43510 These are the supported Host I/O operations:
43513 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
43514 Open a file at @var{filename} and return a file descriptor for it, or
43515 return -1 if an error occurs. The @var{filename} is a string,
43516 @var{flags} is an integer indicating a mask of open flags
43517 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
43518 of mode bits to use if the file is created (@pxref{mode_t Values}).
43519 @xref{open}, for details of the open flags and mode values.
43521 @item vFile:close: @var{fd}
43522 Close the open file corresponding to @var{fd} and return 0, or
43523 -1 if an error occurs.
43525 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
43526 Read data from the open file corresponding to @var{fd}. Up to
43527 @var{count} bytes will be read from the file, starting at @var{offset}
43528 relative to the start of the file. The target may read fewer bytes;
43529 common reasons include packet size limits and an end-of-file
43530 condition. The number of bytes read is returned. Zero should only be
43531 returned for a successful read at the end of the file, or if
43532 @var{count} was zero.
43534 The data read should be returned as a binary attachment on success.
43535 If zero bytes were read, the response should include an empty binary
43536 attachment (i.e.@: a trailing semicolon). The return value is the
43537 number of target bytes read; the binary attachment may be longer if
43538 some characters were escaped.
43540 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
43541 Write @var{data} (a binary buffer) to the open file corresponding
43542 to @var{fd}. Start the write at @var{offset} from the start of the
43543 file. Unlike many @code{write} system calls, there is no
43544 separate @var{count} argument; the length of @var{data} in the
43545 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
43546 which may be shorter than the length of @var{data}, or -1 if an
43549 @item vFile:fstat: @var{fd}
43550 Get information about the open file corresponding to @var{fd}.
43551 On success the information is returned as a binary attachment
43552 and the return value is the size of this attachment in bytes.
43553 If an error occurs the return value is -1. The format of the
43554 returned binary attachment is as described in @ref{struct stat}.
43556 @item vFile:unlink: @var{filename}
43557 Delete the file at @var{filename} on the target. Return 0,
43558 or -1 if an error occurs. The @var{filename} is a string.
43560 @item vFile:readlink: @var{filename}
43561 Read value of symbolic link @var{filename} on the target. Return
43562 the number of bytes read, or -1 if an error occurs.
43564 The data read should be returned as a binary attachment on success.
43565 If zero bytes were read, the response should include an empty binary
43566 attachment (i.e.@: a trailing semicolon). The return value is the
43567 number of target bytes read; the binary attachment may be longer if
43568 some characters were escaped.
43570 @item vFile:setfs: @var{pid}
43571 Select the filesystem on which @code{vFile} operations with
43572 @var{filename} arguments will operate. This is required for
43573 @value{GDBN} to be able to access files on remote targets where
43574 the remote stub does not share a common filesystem with the
43577 If @var{pid} is nonzero, select the filesystem as seen by process
43578 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
43579 the remote stub. Return 0 on success, or -1 if an error occurs.
43580 If @code{vFile:setfs:} indicates success, the selected filesystem
43581 remains selected until the next successful @code{vFile:setfs:}
43587 @section Interrupts
43588 @cindex interrupts (remote protocol)
43589 @anchor{interrupting remote targets}
43591 In all-stop mode, when a program on the remote target is running,
43592 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
43593 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
43594 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
43596 The precise meaning of @code{BREAK} is defined by the transport
43597 mechanism and may, in fact, be undefined. @value{GDBN} does not
43598 currently define a @code{BREAK} mechanism for any of the network
43599 interfaces except for TCP, in which case @value{GDBN} sends the
43600 @code{telnet} BREAK sequence.
43602 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
43603 transport mechanisms. It is represented by sending the single byte
43604 @code{0x03} without any of the usual packet overhead described in
43605 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
43606 transmitted as part of a packet, it is considered to be packet data
43607 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
43608 (@pxref{X packet}), used for binary downloads, may include an unescaped
43609 @code{0x03} as part of its packet.
43611 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
43612 When Linux kernel receives this sequence from serial port,
43613 it stops execution and connects to gdb.
43615 In non-stop mode, because packet resumptions are asynchronous
43616 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
43617 command to the remote stub, even when the target is running. For that
43618 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
43619 packet}) with the usual packet framing instead of the single byte
43622 Stubs are not required to recognize these interrupt mechanisms and the
43623 precise meaning associated with receipt of the interrupt is
43624 implementation defined. If the target supports debugging of multiple
43625 threads and/or processes, it should attempt to interrupt all
43626 currently-executing threads and processes.
43627 If the stub is successful at interrupting the
43628 running program, it should send one of the stop
43629 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
43630 of successfully stopping the program in all-stop mode, and a stop reply
43631 for each stopped thread in non-stop mode.
43632 Interrupts received while the
43633 program is stopped are queued and the program will be interrupted when
43634 it is resumed next time.
43636 @node Notification Packets
43637 @section Notification Packets
43638 @cindex notification packets
43639 @cindex packets, notification
43641 The @value{GDBN} remote serial protocol includes @dfn{notifications},
43642 packets that require no acknowledgment. Both the GDB and the stub
43643 may send notifications (although the only notifications defined at
43644 present are sent by the stub). Notifications carry information
43645 without incurring the round-trip latency of an acknowledgment, and so
43646 are useful for low-impact communications where occasional packet loss
43649 A notification packet has the form @samp{% @var{data} #
43650 @var{checksum}}, where @var{data} is the content of the notification,
43651 and @var{checksum} is a checksum of @var{data}, computed and formatted
43652 as for ordinary @value{GDBN} packets. A notification's @var{data}
43653 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
43654 receiving a notification, the recipient sends no @samp{+} or @samp{-}
43655 to acknowledge the notification's receipt or to report its corruption.
43657 Every notification's @var{data} begins with a name, which contains no
43658 colon characters, followed by a colon character.
43660 Recipients should silently ignore corrupted notifications and
43661 notifications they do not understand. Recipients should restart
43662 timeout periods on receipt of a well-formed notification, whether or
43663 not they understand it.
43665 Senders should only send the notifications described here when this
43666 protocol description specifies that they are permitted. In the
43667 future, we may extend the protocol to permit existing notifications in
43668 new contexts; this rule helps older senders avoid confusing newer
43671 (Older versions of @value{GDBN} ignore bytes received until they see
43672 the @samp{$} byte that begins an ordinary packet, so new stubs may
43673 transmit notifications without fear of confusing older clients. There
43674 are no notifications defined for @value{GDBN} to send at the moment, but we
43675 assume that most older stubs would ignore them, as well.)
43677 Each notification is comprised of three parts:
43679 @item @var{name}:@var{event}
43680 The notification packet is sent by the side that initiates the
43681 exchange (currently, only the stub does that), with @var{event}
43682 carrying the specific information about the notification, and
43683 @var{name} specifying the name of the notification.
43685 The acknowledge sent by the other side, usually @value{GDBN}, to
43686 acknowledge the exchange and request the event.
43689 The purpose of an asynchronous notification mechanism is to report to
43690 @value{GDBN} that something interesting happened in the remote stub.
43692 The remote stub may send notification @var{name}:@var{event}
43693 at any time, but @value{GDBN} acknowledges the notification when
43694 appropriate. The notification event is pending before @value{GDBN}
43695 acknowledges. Only one notification at a time may be pending; if
43696 additional events occur before @value{GDBN} has acknowledged the
43697 previous notification, they must be queued by the stub for later
43698 synchronous transmission in response to @var{ack} packets from
43699 @value{GDBN}. Because the notification mechanism is unreliable,
43700 the stub is permitted to resend a notification if it believes
43701 @value{GDBN} may not have received it.
43703 Specifically, notifications may appear when @value{GDBN} is not
43704 otherwise reading input from the stub, or when @value{GDBN} is
43705 expecting to read a normal synchronous response or a
43706 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
43707 Notification packets are distinct from any other communication from
43708 the stub so there is no ambiguity.
43710 After receiving a notification, @value{GDBN} shall acknowledge it by
43711 sending a @var{ack} packet as a regular, synchronous request to the
43712 stub. Such acknowledgment is not required to happen immediately, as
43713 @value{GDBN} is permitted to send other, unrelated packets to the
43714 stub first, which the stub should process normally.
43716 Upon receiving a @var{ack} packet, if the stub has other queued
43717 events to report to @value{GDBN}, it shall respond by sending a
43718 normal @var{event}. @value{GDBN} shall then send another @var{ack}
43719 packet to solicit further responses; again, it is permitted to send
43720 other, unrelated packets as well which the stub should process
43723 If the stub receives a @var{ack} packet and there are no additional
43724 @var{event} to report, the stub shall return an @samp{OK} response.
43725 At this point, @value{GDBN} has finished processing a notification
43726 and the stub has completed sending any queued events. @value{GDBN}
43727 won't accept any new notifications until the final @samp{OK} is
43728 received . If further notification events occur, the stub shall send
43729 a new notification, @value{GDBN} shall accept the notification, and
43730 the process shall be repeated.
43732 The process of asynchronous notification can be illustrated by the
43735 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
43738 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
43740 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
43745 The following notifications are defined:
43746 @multitable @columnfractions 0.12 0.12 0.38 0.38
43755 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
43756 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
43757 for information on how these notifications are acknowledged by
43759 @tab Report an asynchronous stop event in non-stop mode.
43763 @node Remote Non-Stop
43764 @section Remote Protocol Support for Non-Stop Mode
43766 @value{GDBN}'s remote protocol supports non-stop debugging of
43767 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
43768 supports non-stop mode, it should report that to @value{GDBN} by including
43769 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
43771 @value{GDBN} typically sends a @samp{QNonStop} packet only when
43772 establishing a new connection with the stub. Entering non-stop mode
43773 does not alter the state of any currently-running threads, but targets
43774 must stop all threads in any already-attached processes when entering
43775 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
43776 probe the target state after a mode change.
43778 In non-stop mode, when an attached process encounters an event that
43779 would otherwise be reported with a stop reply, it uses the
43780 asynchronous notification mechanism (@pxref{Notification Packets}) to
43781 inform @value{GDBN}. In contrast to all-stop mode, where all threads
43782 in all processes are stopped when a stop reply is sent, in non-stop
43783 mode only the thread reporting the stop event is stopped. That is,
43784 when reporting a @samp{S} or @samp{T} response to indicate completion
43785 of a step operation, hitting a breakpoint, or a fault, only the
43786 affected thread is stopped; any other still-running threads continue
43787 to run. When reporting a @samp{W} or @samp{X} response, all running
43788 threads belonging to other attached processes continue to run.
43790 In non-stop mode, the target shall respond to the @samp{?} packet as
43791 follows. First, any incomplete stop reply notification/@samp{vStopped}
43792 sequence in progress is abandoned. The target must begin a new
43793 sequence reporting stop events for all stopped threads, whether or not
43794 it has previously reported those events to @value{GDBN}. The first
43795 stop reply is sent as a synchronous reply to the @samp{?} packet, and
43796 subsequent stop replies are sent as responses to @samp{vStopped} packets
43797 using the mechanism described above. The target must not send
43798 asynchronous stop reply notifications until the sequence is complete.
43799 If all threads are running when the target receives the @samp{?} packet,
43800 or if the target is not attached to any process, it shall respond
43803 If the stub supports non-stop mode, it should also support the
43804 @samp{swbreak} stop reason if software breakpoints are supported, and
43805 the @samp{hwbreak} stop reason if hardware breakpoints are supported
43806 (@pxref{swbreak stop reason}). This is because given the asynchronous
43807 nature of non-stop mode, between the time a thread hits a breakpoint
43808 and the time the event is finally processed by @value{GDBN}, the
43809 breakpoint may have already been removed from the target. Due to
43810 this, @value{GDBN} needs to be able to tell whether a trap stop was
43811 caused by a delayed breakpoint event, which should be ignored, as
43812 opposed to a random trap signal, which should be reported to the user.
43813 Note the @samp{swbreak} feature implies that the target is responsible
43814 for adjusting the PC when a software breakpoint triggers, if
43815 necessary, such as on the x86 architecture.
43817 @node Packet Acknowledgment
43818 @section Packet Acknowledgment
43820 @cindex acknowledgment, for @value{GDBN} remote
43821 @cindex packet acknowledgment, for @value{GDBN} remote
43822 By default, when either the host or the target machine receives a packet,
43823 the first response expected is an acknowledgment: either @samp{+} (to indicate
43824 the package was received correctly) or @samp{-} (to request retransmission).
43825 This mechanism allows the @value{GDBN} remote protocol to operate over
43826 unreliable transport mechanisms, such as a serial line.
43828 In cases where the transport mechanism is itself reliable (such as a pipe or
43829 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
43830 It may be desirable to disable them in that case to reduce communication
43831 overhead, or for other reasons. This can be accomplished by means of the
43832 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
43834 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
43835 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
43836 and response format still includes the normal checksum, as described in
43837 @ref{Overview}, but the checksum may be ignored by the receiver.
43839 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
43840 no-acknowledgment mode, it should report that to @value{GDBN}
43841 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
43842 @pxref{qSupported}.
43843 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
43844 disabled via the @code{set remote noack-packet off} command
43845 (@pxref{Remote Configuration}),
43846 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
43847 Only then may the stub actually turn off packet acknowledgments.
43848 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
43849 response, which can be safely ignored by the stub.
43851 Note that @code{set remote noack-packet} command only affects negotiation
43852 between @value{GDBN} and the stub when subsequent connections are made;
43853 it does not affect the protocol acknowledgment state for any current
43855 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
43856 new connection is established,
43857 there is also no protocol request to re-enable the acknowledgments
43858 for the current connection, once disabled.
43863 Example sequence of a target being re-started. Notice how the restart
43864 does not get any direct output:
43869 @emph{target restarts}
43872 <- @code{T001:1234123412341234}
43876 Example sequence of a target being stepped by a single instruction:
43879 -> @code{G1445@dots{}}
43884 <- @code{T001:1234123412341234}
43888 <- @code{1455@dots{}}
43892 @node File-I/O Remote Protocol Extension
43893 @section File-I/O Remote Protocol Extension
43894 @cindex File-I/O remote protocol extension
43897 * File-I/O Overview::
43898 * Protocol Basics::
43899 * The F Request Packet::
43900 * The F Reply Packet::
43901 * The Ctrl-C Message::
43903 * List of Supported Calls::
43904 * Protocol-specific Representation of Datatypes::
43906 * File-I/O Examples::
43909 @node File-I/O Overview
43910 @subsection File-I/O Overview
43911 @cindex file-i/o overview
43913 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
43914 target to use the host's file system and console I/O to perform various
43915 system calls. System calls on the target system are translated into a
43916 remote protocol packet to the host system, which then performs the needed
43917 actions and returns a response packet to the target system.
43918 This simulates file system operations even on targets that lack file systems.
43920 The protocol is defined to be independent of both the host and target systems.
43921 It uses its own internal representation of datatypes and values. Both
43922 @value{GDBN} and the target's @value{GDBN} stub are responsible for
43923 translating the system-dependent value representations into the internal
43924 protocol representations when data is transmitted.
43926 The communication is synchronous. A system call is possible only when
43927 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
43928 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
43929 the target is stopped to allow deterministic access to the target's
43930 memory. Therefore File-I/O is not interruptible by target signals. On
43931 the other hand, it is possible to interrupt File-I/O by a user interrupt
43932 (@samp{Ctrl-C}) within @value{GDBN}.
43934 The target's request to perform a host system call does not finish
43935 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
43936 after finishing the system call, the target returns to continuing the
43937 previous activity (continue, step). No additional continue or step
43938 request from @value{GDBN} is required.
43941 (@value{GDBP}) continue
43942 <- target requests 'system call X'
43943 target is stopped, @value{GDBN} executes system call
43944 -> @value{GDBN} returns result
43945 ... target continues, @value{GDBN} returns to wait for the target
43946 <- target hits breakpoint and sends a Txx packet
43949 The protocol only supports I/O on the console and to regular files on
43950 the host file system. Character or block special devices, pipes,
43951 named pipes, sockets or any other communication method on the host
43952 system are not supported by this protocol.
43954 File I/O is not supported in non-stop mode.
43956 @node Protocol Basics
43957 @subsection Protocol Basics
43958 @cindex protocol basics, file-i/o
43960 The File-I/O protocol uses the @code{F} packet as the request as well
43961 as reply packet. Since a File-I/O system call can only occur when
43962 @value{GDBN} is waiting for a response from the continuing or stepping target,
43963 the File-I/O request is a reply that @value{GDBN} has to expect as a result
43964 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
43965 This @code{F} packet contains all information needed to allow @value{GDBN}
43966 to call the appropriate host system call:
43970 A unique identifier for the requested system call.
43973 All parameters to the system call. Pointers are given as addresses
43974 in the target memory address space. Pointers to strings are given as
43975 pointer/length pair. Numerical values are given as they are.
43976 Numerical control flags are given in a protocol-specific representation.
43980 At this point, @value{GDBN} has to perform the following actions.
43984 If the parameters include pointer values to data needed as input to a
43985 system call, @value{GDBN} requests this data from the target with a
43986 standard @code{m} packet request. This additional communication has to be
43987 expected by the target implementation and is handled as any other @code{m}
43991 @value{GDBN} translates all value from protocol representation to host
43992 representation as needed. Datatypes are coerced into the host types.
43995 @value{GDBN} calls the system call.
43998 It then coerces datatypes back to protocol representation.
44001 If the system call is expected to return data in buffer space specified
44002 by pointer parameters to the call, the data is transmitted to the
44003 target using a @code{M} or @code{X} packet. This packet has to be expected
44004 by the target implementation and is handled as any other @code{M} or @code{X}
44009 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44010 necessary information for the target to continue. This at least contains
44017 @code{errno}, if has been changed by the system call.
44024 After having done the needed type and value coercion, the target continues
44025 the latest continue or step action.
44027 @node The F Request Packet
44028 @subsection The @code{F} Request Packet
44029 @cindex file-i/o request packet
44030 @cindex @code{F} request packet
44032 The @code{F} request packet has the following format:
44035 @item F@var{call-id},@var{parameter@dots{}}
44037 @var{call-id} is the identifier to indicate the host system call to be called.
44038 This is just the name of the function.
44040 @var{parameter@dots{}} are the parameters to the system call.
44041 Parameters are hexadecimal integer values, either the actual values in case
44042 of scalar datatypes, pointers to target buffer space in case of compound
44043 datatypes and unspecified memory areas, or pointer/length pairs in case
44044 of string parameters. These are appended to the @var{call-id} as a
44045 comma-delimited list. All values are transmitted in ASCII
44046 string representation, pointer/length pairs separated by a slash.
44052 @node The F Reply Packet
44053 @subsection The @code{F} Reply Packet
44054 @cindex file-i/o reply packet
44055 @cindex @code{F} reply packet
44057 The @code{F} reply packet has the following format:
44061 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44063 @var{retcode} is the return code of the system call as hexadecimal value.
44065 @var{errno} is the @code{errno} set by the call, in protocol-specific
44067 This parameter can be omitted if the call was successful.
44069 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44070 case, @var{errno} must be sent as well, even if the call was successful.
44071 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44078 or, if the call was interrupted before the host call has been performed:
44085 assuming 4 is the protocol-specific representation of @code{EINTR}.
44090 @node The Ctrl-C Message
44091 @subsection The @samp{Ctrl-C} Message
44092 @cindex ctrl-c message, in file-i/o protocol
44094 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44095 reply packet (@pxref{The F Reply Packet}),
44096 the target should behave as if it had
44097 gotten a break message. The meaning for the target is ``system call
44098 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44099 (as with a break message) and return to @value{GDBN} with a @code{T02}
44102 It's important for the target to know in which
44103 state the system call was interrupted. There are two possible cases:
44107 The system call hasn't been performed on the host yet.
44110 The system call on the host has been finished.
44114 These two states can be distinguished by the target by the value of the
44115 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44116 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44117 on POSIX systems. In any other case, the target may presume that the
44118 system call has been finished --- successfully or not --- and should behave
44119 as if the break message arrived right after the system call.
44121 @value{GDBN} must behave reliably. If the system call has not been called
44122 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44123 @code{errno} in the packet. If the system call on the host has been finished
44124 before the user requests a break, the full action must be finished by
44125 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44126 The @code{F} packet may only be sent when either nothing has happened
44127 or the full action has been completed.
44130 @subsection Console I/O
44131 @cindex console i/o as part of file-i/o
44133 By default and if not explicitly closed by the target system, the file
44134 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44135 on the @value{GDBN} console is handled as any other file output operation
44136 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44137 by @value{GDBN} so that after the target read request from file descriptor
44138 0 all following typing is buffered until either one of the following
44143 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44145 system call is treated as finished.
44148 The user presses @key{RET}. This is treated as end of input with a trailing
44152 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44153 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44157 If the user has typed more characters than fit in the buffer given to
44158 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44159 either another @code{read(0, @dots{})} is requested by the target, or debugging
44160 is stopped at the user's request.
44163 @node List of Supported Calls
44164 @subsection List of Supported Calls
44165 @cindex list of supported file-i/o calls
44182 @unnumberedsubsubsec open
44183 @cindex open, file-i/o system call
44188 int open(const char *pathname, int flags);
44189 int open(const char *pathname, int flags, mode_t mode);
44193 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
44196 @var{flags} is the bitwise @code{OR} of the following values:
44200 If the file does not exist it will be created. The host
44201 rules apply as far as file ownership and time stamps
44205 When used with @code{O_CREAT}, if the file already exists it is
44206 an error and open() fails.
44209 If the file already exists and the open mode allows
44210 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
44211 truncated to zero length.
44214 The file is opened in append mode.
44217 The file is opened for reading only.
44220 The file is opened for writing only.
44223 The file is opened for reading and writing.
44227 Other bits are silently ignored.
44231 @var{mode} is the bitwise @code{OR} of the following values:
44235 User has read permission.
44238 User has write permission.
44241 Group has read permission.
44244 Group has write permission.
44247 Others have read permission.
44250 Others have write permission.
44254 Other bits are silently ignored.
44257 @item Return value:
44258 @code{open} returns the new file descriptor or -1 if an error
44265 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
44268 @var{pathname} refers to a directory.
44271 The requested access is not allowed.
44274 @var{pathname} was too long.
44277 A directory component in @var{pathname} does not exist.
44280 @var{pathname} refers to a device, pipe, named pipe or socket.
44283 @var{pathname} refers to a file on a read-only filesystem and
44284 write access was requested.
44287 @var{pathname} is an invalid pointer value.
44290 No space on device to create the file.
44293 The process already has the maximum number of files open.
44296 The limit on the total number of files open on the system
44300 The call was interrupted by the user.
44306 @unnumberedsubsubsec close
44307 @cindex close, file-i/o system call
44316 @samp{Fclose,@var{fd}}
44318 @item Return value:
44319 @code{close} returns zero on success, or -1 if an error occurred.
44325 @var{fd} isn't a valid open file descriptor.
44328 The call was interrupted by the user.
44334 @unnumberedsubsubsec read
44335 @cindex read, file-i/o system call
44340 int read(int fd, void *buf, unsigned int count);
44344 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
44346 @item Return value:
44347 On success, the number of bytes read is returned.
44348 Zero indicates end of file. If count is zero, read
44349 returns zero as well. On error, -1 is returned.
44355 @var{fd} is not a valid file descriptor or is not open for
44359 @var{bufptr} is an invalid pointer value.
44362 The call was interrupted by the user.
44368 @unnumberedsubsubsec write
44369 @cindex write, file-i/o system call
44374 int write(int fd, const void *buf, unsigned int count);
44378 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
44380 @item Return value:
44381 On success, the number of bytes written are returned.
44382 Zero indicates nothing was written. On error, -1
44389 @var{fd} is not a valid file descriptor or is not open for
44393 @var{bufptr} is an invalid pointer value.
44396 An attempt was made to write a file that exceeds the
44397 host-specific maximum file size allowed.
44400 No space on device to write the data.
44403 The call was interrupted by the user.
44409 @unnumberedsubsubsec lseek
44410 @cindex lseek, file-i/o system call
44415 long lseek (int fd, long offset, int flag);
44419 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
44421 @var{flag} is one of:
44425 The offset is set to @var{offset} bytes.
44428 The offset is set to its current location plus @var{offset}
44432 The offset is set to the size of the file plus @var{offset}
44436 @item Return value:
44437 On success, the resulting unsigned offset in bytes from
44438 the beginning of the file is returned. Otherwise, a
44439 value of -1 is returned.
44445 @var{fd} is not a valid open file descriptor.
44448 @var{fd} is associated with the @value{GDBN} console.
44451 @var{flag} is not a proper value.
44454 The call was interrupted by the user.
44460 @unnumberedsubsubsec rename
44461 @cindex rename, file-i/o system call
44466 int rename(const char *oldpath, const char *newpath);
44470 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
44472 @item Return value:
44473 On success, zero is returned. On error, -1 is returned.
44479 @var{newpath} is an existing directory, but @var{oldpath} is not a
44483 @var{newpath} is a non-empty directory.
44486 @var{oldpath} or @var{newpath} is a directory that is in use by some
44490 An attempt was made to make a directory a subdirectory
44494 A component used as a directory in @var{oldpath} or new
44495 path is not a directory. Or @var{oldpath} is a directory
44496 and @var{newpath} exists but is not a directory.
44499 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
44502 No access to the file or the path of the file.
44506 @var{oldpath} or @var{newpath} was too long.
44509 A directory component in @var{oldpath} or @var{newpath} does not exist.
44512 The file is on a read-only filesystem.
44515 The device containing the file has no room for the new
44519 The call was interrupted by the user.
44525 @unnumberedsubsubsec unlink
44526 @cindex unlink, file-i/o system call
44531 int unlink(const char *pathname);
44535 @samp{Funlink,@var{pathnameptr}/@var{len}}
44537 @item Return value:
44538 On success, zero is returned. On error, -1 is returned.
44544 No access to the file or the path of the file.
44547 The system does not allow unlinking of directories.
44550 The file @var{pathname} cannot be unlinked because it's
44551 being used by another process.
44554 @var{pathnameptr} is an invalid pointer value.
44557 @var{pathname} was too long.
44560 A directory component in @var{pathname} does not exist.
44563 A component of the path is not a directory.
44566 The file is on a read-only filesystem.
44569 The call was interrupted by the user.
44575 @unnumberedsubsubsec stat/fstat
44576 @cindex fstat, file-i/o system call
44577 @cindex stat, file-i/o system call
44582 int stat(const char *pathname, struct stat *buf);
44583 int fstat(int fd, struct stat *buf);
44587 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
44588 @samp{Ffstat,@var{fd},@var{bufptr}}
44590 @item Return value:
44591 On success, zero is returned. On error, -1 is returned.
44597 @var{fd} is not a valid open file.
44600 A directory component in @var{pathname} does not exist or the
44601 path is an empty string.
44604 A component of the path is not a directory.
44607 @var{pathnameptr} is an invalid pointer value.
44610 No access to the file or the path of the file.
44613 @var{pathname} was too long.
44616 The call was interrupted by the user.
44622 @unnumberedsubsubsec gettimeofday
44623 @cindex gettimeofday, file-i/o system call
44628 int gettimeofday(struct timeval *tv, void *tz);
44632 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
44634 @item Return value:
44635 On success, 0 is returned, -1 otherwise.
44641 @var{tz} is a non-NULL pointer.
44644 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
44650 @unnumberedsubsubsec isatty
44651 @cindex isatty, file-i/o system call
44656 int isatty(int fd);
44660 @samp{Fisatty,@var{fd}}
44662 @item Return value:
44663 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
44669 The call was interrupted by the user.
44674 Note that the @code{isatty} call is treated as a special case: it returns
44675 1 to the target if the file descriptor is attached
44676 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
44677 would require implementing @code{ioctl} and would be more complex than
44682 @unnumberedsubsubsec system
44683 @cindex system, file-i/o system call
44688 int system(const char *command);
44692 @samp{Fsystem,@var{commandptr}/@var{len}}
44694 @item Return value:
44695 If @var{len} is zero, the return value indicates whether a shell is
44696 available. A zero return value indicates a shell is not available.
44697 For non-zero @var{len}, the value returned is -1 on error and the
44698 return status of the command otherwise. Only the exit status of the
44699 command is returned, which is extracted from the host's @code{system}
44700 return value by calling @code{WEXITSTATUS(retval)}. In case
44701 @file{/bin/sh} could not be executed, 127 is returned.
44707 The call was interrupted by the user.
44712 @value{GDBN} takes over the full task of calling the necessary host calls
44713 to perform the @code{system} call. The return value of @code{system} on
44714 the host is simplified before it's returned
44715 to the target. Any termination signal information from the child process
44716 is discarded, and the return value consists
44717 entirely of the exit status of the called command.
44719 Due to security concerns, the @code{system} call is by default refused
44720 by @value{GDBN}. The user has to allow this call explicitly with the
44721 @code{set remote system-call-allowed 1} command.
44724 @item set remote system-call-allowed
44725 @kindex set remote system-call-allowed
44726 Control whether to allow the @code{system} calls in the File I/O
44727 protocol for the remote target. The default is zero (disabled).
44729 @item show remote system-call-allowed
44730 @kindex show remote system-call-allowed
44731 Show whether the @code{system} calls are allowed in the File I/O
44735 @node Protocol-specific Representation of Datatypes
44736 @subsection Protocol-specific Representation of Datatypes
44737 @cindex protocol-specific representation of datatypes, in file-i/o protocol
44740 * Integral Datatypes::
44742 * Memory Transfer::
44747 @node Integral Datatypes
44748 @unnumberedsubsubsec Integral Datatypes
44749 @cindex integral datatypes, in file-i/o protocol
44751 The integral datatypes used in the system calls are @code{int},
44752 @code{unsigned int}, @code{long}, @code{unsigned long},
44753 @code{mode_t}, and @code{time_t}.
44755 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
44756 implemented as 32 bit values in this protocol.
44758 @code{long} and @code{unsigned long} are implemented as 64 bit types.
44760 @xref{Limits}, for corresponding MIN and MAX values (similar to those
44761 in @file{limits.h}) to allow range checking on host and target.
44763 @code{time_t} datatypes are defined as seconds since the Epoch.
44765 All integral datatypes transferred as part of a memory read or write of a
44766 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
44769 @node Pointer Values
44770 @unnumberedsubsubsec Pointer Values
44771 @cindex pointer values, in file-i/o protocol
44773 Pointers to target data are transmitted as they are. An exception
44774 is made for pointers to buffers for which the length isn't
44775 transmitted as part of the function call, namely strings. Strings
44776 are transmitted as a pointer/length pair, both as hex values, e.g.@:
44783 which is a pointer to data of length 18 bytes at position 0x1aaf.
44784 The length is defined as the full string length in bytes, including
44785 the trailing null byte. For example, the string @code{"hello world"}
44786 at address 0x123456 is transmitted as
44792 @node Memory Transfer
44793 @unnumberedsubsubsec Memory Transfer
44794 @cindex memory transfer, in file-i/o protocol
44796 Structured data which is transferred using a memory read or write (for
44797 example, a @code{struct stat}) is expected to be in a protocol-specific format
44798 with all scalar multibyte datatypes being big endian. Translation to
44799 this representation needs to be done both by the target before the @code{F}
44800 packet is sent, and by @value{GDBN} before
44801 it transfers memory to the target. Transferred pointers to structured
44802 data should point to the already-coerced data at any time.
44806 @unnumberedsubsubsec struct stat
44807 @cindex struct stat, in file-i/o protocol
44809 The buffer of type @code{struct stat} used by the target and @value{GDBN}
44810 is defined as follows:
44814 unsigned int st_dev; /* device */
44815 unsigned int st_ino; /* inode */
44816 mode_t st_mode; /* protection */
44817 unsigned int st_nlink; /* number of hard links */
44818 unsigned int st_uid; /* user ID of owner */
44819 unsigned int st_gid; /* group ID of owner */
44820 unsigned int st_rdev; /* device type (if inode device) */
44821 unsigned long st_size; /* total size, in bytes */
44822 unsigned long st_blksize; /* blocksize for filesystem I/O */
44823 unsigned long st_blocks; /* number of blocks allocated */
44824 time_t st_atime; /* time of last access */
44825 time_t st_mtime; /* time of last modification */
44826 time_t st_ctime; /* time of last change */
44830 The integral datatypes conform to the definitions given in the
44831 appropriate section (see @ref{Integral Datatypes}, for details) so this
44832 structure is of size 64 bytes.
44834 The values of several fields have a restricted meaning and/or
44840 A value of 0 represents a file, 1 the console.
44843 No valid meaning for the target. Transmitted unchanged.
44846 Valid mode bits are described in @ref{Constants}. Any other
44847 bits have currently no meaning for the target.
44852 No valid meaning for the target. Transmitted unchanged.
44857 These values have a host and file system dependent
44858 accuracy. Especially on Windows hosts, the file system may not
44859 support exact timing values.
44862 The target gets a @code{struct stat} of the above representation and is
44863 responsible for coercing it to the target representation before
44866 Note that due to size differences between the host, target, and protocol
44867 representations of @code{struct stat} members, these members could eventually
44868 get truncated on the target.
44870 @node struct timeval
44871 @unnumberedsubsubsec struct timeval
44872 @cindex struct timeval, in file-i/o protocol
44874 The buffer of type @code{struct timeval} used by the File-I/O protocol
44875 is defined as follows:
44879 time_t tv_sec; /* second */
44880 long tv_usec; /* microsecond */
44884 The integral datatypes conform to the definitions given in the
44885 appropriate section (see @ref{Integral Datatypes}, for details) so this
44886 structure is of size 8 bytes.
44889 @subsection Constants
44890 @cindex constants, in file-i/o protocol
44892 The following values are used for the constants inside of the
44893 protocol. @value{GDBN} and target are responsible for translating these
44894 values before and after the call as needed.
44905 @unnumberedsubsubsec Open Flags
44906 @cindex open flags, in file-i/o protocol
44908 All values are given in hexadecimal representation.
44920 @node mode_t Values
44921 @unnumberedsubsubsec mode_t Values
44922 @cindex mode_t values, in file-i/o protocol
44924 All values are given in octal representation.
44941 @unnumberedsubsubsec Errno Values
44942 @cindex errno values, in file-i/o protocol
44944 All values are given in decimal representation.
44969 @code{EUNKNOWN} is used as a fallback error value if a host system returns
44970 any error value not in the list of supported error numbers.
44973 @unnumberedsubsubsec Lseek Flags
44974 @cindex lseek flags, in file-i/o protocol
44983 @unnumberedsubsubsec Limits
44984 @cindex limits, in file-i/o protocol
44986 All values are given in decimal representation.
44989 INT_MIN -2147483648
44991 UINT_MAX 4294967295
44992 LONG_MIN -9223372036854775808
44993 LONG_MAX 9223372036854775807
44994 ULONG_MAX 18446744073709551615
44997 @node File-I/O Examples
44998 @subsection File-I/O Examples
44999 @cindex file-i/o examples
45001 Example sequence of a write call, file descriptor 3, buffer is at target
45002 address 0x1234, 6 bytes should be written:
45005 <- @code{Fwrite,3,1234,6}
45006 @emph{request memory read from target}
45009 @emph{return "6 bytes written"}
45013 Example sequence of a read call, file descriptor 3, buffer is at target
45014 address 0x1234, 6 bytes should be read:
45017 <- @code{Fread,3,1234,6}
45018 @emph{request memory write to target}
45019 -> @code{X1234,6:XXXXXX}
45020 @emph{return "6 bytes read"}
45024 Example sequence of a read call, call fails on the host due to invalid
45025 file descriptor (@code{EBADF}):
45028 <- @code{Fread,3,1234,6}
45032 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45036 <- @code{Fread,3,1234,6}
45041 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45045 <- @code{Fread,3,1234,6}
45046 -> @code{X1234,6:XXXXXX}
45050 @node Library List Format
45051 @section Library List Format
45052 @cindex library list format, remote protocol
45054 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45055 same process as your application to manage libraries. In this case,
45056 @value{GDBN} can use the loader's symbol table and normal memory
45057 operations to maintain a list of shared libraries. On other
45058 platforms, the operating system manages loaded libraries.
45059 @value{GDBN} can not retrieve the list of currently loaded libraries
45060 through memory operations, so it uses the @samp{qXfer:libraries:read}
45061 packet (@pxref{qXfer library list read}) instead. The remote stub
45062 queries the target's operating system and reports which libraries
45065 The @samp{qXfer:libraries:read} packet returns an XML document which
45066 lists loaded libraries and their offsets. Each library has an
45067 associated name and one or more segment or section base addresses,
45068 which report where the library was loaded in memory.
45070 For the common case of libraries that are fully linked binaries, the
45071 library should have a list of segments. If the target supports
45072 dynamic linking of a relocatable object file, its library XML element
45073 should instead include a list of allocated sections. The segment or
45074 section bases are start addresses, not relocation offsets; they do not
45075 depend on the library's link-time base addresses.
45077 @value{GDBN} must be linked with the Expat library to support XML
45078 library lists. @xref{Expat}.
45080 A simple memory map, with one loaded library relocated by a single
45081 offset, looks like this:
45085 <library name="/lib/libc.so.6">
45086 <segment address="0x10000000"/>
45091 Another simple memory map, with one loaded library with three
45092 allocated sections (.text, .data, .bss), looks like this:
45096 <library name="sharedlib.o">
45097 <section address="0x10000000"/>
45098 <section address="0x20000000"/>
45099 <section address="0x30000000"/>
45104 The format of a library list is described by this DTD:
45107 <!-- library-list: Root element with versioning -->
45108 <!ELEMENT library-list (library)*>
45109 <!ATTLIST library-list version CDATA #FIXED "1.0">
45110 <!ELEMENT library (segment*, section*)>
45111 <!ATTLIST library name CDATA #REQUIRED>
45112 <!ELEMENT segment EMPTY>
45113 <!ATTLIST segment address CDATA #REQUIRED>
45114 <!ELEMENT section EMPTY>
45115 <!ATTLIST section address CDATA #REQUIRED>
45118 In addition, segments and section descriptors cannot be mixed within a
45119 single library element, and you must supply at least one segment or
45120 section for each library.
45122 @node Library List Format for SVR4 Targets
45123 @section Library List Format for SVR4 Targets
45124 @cindex library list format, remote protocol
45126 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45127 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45128 shared libraries. Still a special library list provided by this packet is
45129 more efficient for the @value{GDBN} remote protocol.
45131 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45132 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45133 target, the following parameters are reported:
45137 @code{name}, the absolute file name from the @code{l_name} field of
45138 @code{struct link_map}.
45140 @code{lm} with address of @code{struct link_map} used for TLS
45141 (Thread Local Storage) access.
45143 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45144 @code{struct link_map}. For prelinked libraries this is not an absolute
45145 memory address. It is a displacement of absolute memory address against
45146 address the file was prelinked to during the library load.
45148 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45151 Additionally the single @code{main-lm} attribute specifies address of
45152 @code{struct link_map} used for the main executable. This parameter is used
45153 for TLS access and its presence is optional.
45155 @value{GDBN} must be linked with the Expat library to support XML
45156 SVR4 library lists. @xref{Expat}.
45158 A simple memory map, with two loaded libraries (which do not use prelink),
45162 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45163 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45165 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45167 </library-list-svr>
45170 The format of an SVR4 library list is described by this DTD:
45173 <!-- library-list-svr4: Root element with versioning -->
45174 <!ELEMENT library-list-svr4 (library)*>
45175 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45176 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45177 <!ELEMENT library EMPTY>
45178 <!ATTLIST library name CDATA #REQUIRED>
45179 <!ATTLIST library lm CDATA #REQUIRED>
45180 <!ATTLIST library l_addr CDATA #REQUIRED>
45181 <!ATTLIST library l_ld CDATA #REQUIRED>
45184 @node Memory Map Format
45185 @section Memory Map Format
45186 @cindex memory map format
45188 To be able to write into flash memory, @value{GDBN} needs to obtain a
45189 memory map from the target. This section describes the format of the
45192 The memory map is obtained using the @samp{qXfer:memory-map:read}
45193 (@pxref{qXfer memory map read}) packet and is an XML document that
45194 lists memory regions.
45196 @value{GDBN} must be linked with the Expat library to support XML
45197 memory maps. @xref{Expat}.
45199 The top-level structure of the document is shown below:
45202 <?xml version="1.0"?>
45203 <!DOCTYPE memory-map
45204 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45205 "http://sourceware.org/gdb/gdb-memory-map.dtd">
45211 Each region can be either:
45216 A region of RAM starting at @var{addr} and extending for @var{length}
45220 <memory type="ram" start="@var{addr}" length="@var{length}"/>
45225 A region of read-only memory:
45228 <memory type="rom" start="@var{addr}" length="@var{length}"/>
45233 A region of flash memory, with erasure blocks @var{blocksize}
45237 <memory type="flash" start="@var{addr}" length="@var{length}">
45238 <property name="blocksize">@var{blocksize}</property>
45244 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
45245 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
45246 packets to write to addresses in such ranges.
45248 The formal DTD for memory map format is given below:
45251 <!-- ................................................... -->
45252 <!-- Memory Map XML DTD ................................ -->
45253 <!-- File: memory-map.dtd .............................. -->
45254 <!-- .................................... .............. -->
45255 <!-- memory-map.dtd -->
45256 <!-- memory-map: Root element with versioning -->
45257 <!ELEMENT memory-map (memory)*>
45258 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
45259 <!ELEMENT memory (property)*>
45260 <!-- memory: Specifies a memory region,
45261 and its type, or device. -->
45262 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
45263 start CDATA #REQUIRED
45264 length CDATA #REQUIRED>
45265 <!-- property: Generic attribute tag -->
45266 <!ELEMENT property (#PCDATA | property)*>
45267 <!ATTLIST property name (blocksize) #REQUIRED>
45270 @node Thread List Format
45271 @section Thread List Format
45272 @cindex thread list format
45274 To efficiently update the list of threads and their attributes,
45275 @value{GDBN} issues the @samp{qXfer:threads:read} packet
45276 (@pxref{qXfer threads read}) and obtains the XML document with
45277 the following structure:
45280 <?xml version="1.0"?>
45282 <thread id="id" core="0" name="name">
45283 ... description ...
45288 Each @samp{thread} element must have the @samp{id} attribute that
45289 identifies the thread (@pxref{thread-id syntax}). The
45290 @samp{core} attribute, if present, specifies which processor core
45291 the thread was last executing on. The @samp{name} attribute, if
45292 present, specifies the human-readable name of the thread. The content
45293 of the of @samp{thread} element is interpreted as human-readable
45294 auxiliary information. The @samp{handle} attribute, if present,
45295 is a hex encoded representation of the thread handle.
45298 @node Traceframe Info Format
45299 @section Traceframe Info Format
45300 @cindex traceframe info format
45302 To be able to know which objects in the inferior can be examined when
45303 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
45304 memory ranges, registers and trace state variables that have been
45305 collected in a traceframe.
45307 This list is obtained using the @samp{qXfer:traceframe-info:read}
45308 (@pxref{qXfer traceframe info read}) packet and is an XML document.
45310 @value{GDBN} must be linked with the Expat library to support XML
45311 traceframe info discovery. @xref{Expat}.
45313 The top-level structure of the document is shown below:
45316 <?xml version="1.0"?>
45317 <!DOCTYPE traceframe-info
45318 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45319 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
45325 Each traceframe block can be either:
45330 A region of collected memory starting at @var{addr} and extending for
45331 @var{length} bytes from there:
45334 <memory start="@var{addr}" length="@var{length}"/>
45338 A block indicating trace state variable numbered @var{number} has been
45342 <tvar id="@var{number}"/>
45347 The formal DTD for the traceframe info format is given below:
45350 <!ELEMENT traceframe-info (memory | tvar)* >
45351 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
45353 <!ELEMENT memory EMPTY>
45354 <!ATTLIST memory start CDATA #REQUIRED
45355 length CDATA #REQUIRED>
45357 <!ATTLIST tvar id CDATA #REQUIRED>
45360 @node Branch Trace Format
45361 @section Branch Trace Format
45362 @cindex branch trace format
45364 In order to display the branch trace of an inferior thread,
45365 @value{GDBN} needs to obtain the list of branches. This list is
45366 represented as list of sequential code blocks that are connected via
45367 branches. The code in each block has been executed sequentially.
45369 This list is obtained using the @samp{qXfer:btrace:read}
45370 (@pxref{qXfer btrace read}) packet and is an XML document.
45372 @value{GDBN} must be linked with the Expat library to support XML
45373 traceframe info discovery. @xref{Expat}.
45375 The top-level structure of the document is shown below:
45378 <?xml version="1.0"?>
45380 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
45381 "http://sourceware.org/gdb/gdb-btrace.dtd">
45390 A block of sequentially executed instructions starting at @var{begin}
45391 and ending at @var{end}:
45394 <block begin="@var{begin}" end="@var{end}"/>
45399 The formal DTD for the branch trace format is given below:
45402 <!ELEMENT btrace (block* | pt) >
45403 <!ATTLIST btrace version CDATA #FIXED "1.0">
45405 <!ELEMENT block EMPTY>
45406 <!ATTLIST block begin CDATA #REQUIRED
45407 end CDATA #REQUIRED>
45409 <!ELEMENT pt (pt-config?, raw?)>
45411 <!ELEMENT pt-config (cpu?)>
45413 <!ELEMENT cpu EMPTY>
45414 <!ATTLIST cpu vendor CDATA #REQUIRED
45415 family CDATA #REQUIRED
45416 model CDATA #REQUIRED
45417 stepping CDATA #REQUIRED>
45419 <!ELEMENT raw (#PCDATA)>
45422 @node Branch Trace Configuration Format
45423 @section Branch Trace Configuration Format
45424 @cindex branch trace configuration format
45426 For each inferior thread, @value{GDBN} can obtain the branch trace
45427 configuration using the @samp{qXfer:btrace-conf:read}
45428 (@pxref{qXfer btrace-conf read}) packet.
45430 The configuration describes the branch trace format and configuration
45431 settings for that format. The following information is described:
45435 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
45438 The size of the @acronym{BTS} ring buffer in bytes.
45441 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
45445 The size of the @acronym{Intel PT} ring buffer in bytes.
45449 @value{GDBN} must be linked with the Expat library to support XML
45450 branch trace configuration discovery. @xref{Expat}.
45452 The formal DTD for the branch trace configuration format is given below:
45455 <!ELEMENT btrace-conf (bts?, pt?)>
45456 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
45458 <!ELEMENT bts EMPTY>
45459 <!ATTLIST bts size CDATA #IMPLIED>
45461 <!ELEMENT pt EMPTY>
45462 <!ATTLIST pt size CDATA #IMPLIED>
45465 @include agentexpr.texi
45467 @node Target Descriptions
45468 @appendix Target Descriptions
45469 @cindex target descriptions
45471 One of the challenges of using @value{GDBN} to debug embedded systems
45472 is that there are so many minor variants of each processor
45473 architecture in use. It is common practice for vendors to start with
45474 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
45475 and then make changes to adapt it to a particular market niche. Some
45476 architectures have hundreds of variants, available from dozens of
45477 vendors. This leads to a number of problems:
45481 With so many different customized processors, it is difficult for
45482 the @value{GDBN} maintainers to keep up with the changes.
45484 Since individual variants may have short lifetimes or limited
45485 audiences, it may not be worthwhile to carry information about every
45486 variant in the @value{GDBN} source tree.
45488 When @value{GDBN} does support the architecture of the embedded system
45489 at hand, the task of finding the correct architecture name to give the
45490 @command{set architecture} command can be error-prone.
45493 To address these problems, the @value{GDBN} remote protocol allows a
45494 target system to not only identify itself to @value{GDBN}, but to
45495 actually describe its own features. This lets @value{GDBN} support
45496 processor variants it has never seen before --- to the extent that the
45497 descriptions are accurate, and that @value{GDBN} understands them.
45499 @value{GDBN} must be linked with the Expat library to support XML
45500 target descriptions. @xref{Expat}.
45503 * Retrieving Descriptions:: How descriptions are fetched from a target.
45504 * Target Description Format:: The contents of a target description.
45505 * Predefined Target Types:: Standard types available for target
45507 * Enum Target Types:: How to define enum target types.
45508 * Standard Target Features:: Features @value{GDBN} knows about.
45511 @node Retrieving Descriptions
45512 @section Retrieving Descriptions
45514 Target descriptions can be read from the target automatically, or
45515 specified by the user manually. The default behavior is to read the
45516 description from the target. @value{GDBN} retrieves it via the remote
45517 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
45518 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
45519 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
45520 XML document, of the form described in @ref{Target Description
45523 Alternatively, you can specify a file to read for the target description.
45524 If a file is set, the target will not be queried. The commands to
45525 specify a file are:
45528 @cindex set tdesc filename
45529 @item set tdesc filename @var{path}
45530 Read the target description from @var{path}.
45532 @cindex unset tdesc filename
45533 @item unset tdesc filename
45534 Do not read the XML target description from a file. @value{GDBN}
45535 will use the description supplied by the current target.
45537 @cindex show tdesc filename
45538 @item show tdesc filename
45539 Show the filename to read for a target description, if any.
45543 @node Target Description Format
45544 @section Target Description Format
45545 @cindex target descriptions, XML format
45547 A target description annex is an @uref{http://www.w3.org/XML/, XML}
45548 document which complies with the Document Type Definition provided in
45549 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
45550 means you can use generally available tools like @command{xmllint} to
45551 check that your feature descriptions are well-formed and valid.
45552 However, to help people unfamiliar with XML write descriptions for
45553 their targets, we also describe the grammar here.
45555 Target descriptions can identify the architecture of the remote target
45556 and (for some architectures) provide information about custom register
45557 sets. They can also identify the OS ABI of the remote target.
45558 @value{GDBN} can use this information to autoconfigure for your
45559 target, or to warn you if you connect to an unsupported target.
45561 Here is a simple target description:
45564 <target version="1.0">
45565 <architecture>i386:x86-64</architecture>
45570 This minimal description only says that the target uses
45571 the x86-64 architecture.
45573 A target description has the following overall form, with [ ] marking
45574 optional elements and @dots{} marking repeatable elements. The elements
45575 are explained further below.
45578 <?xml version="1.0"?>
45579 <!DOCTYPE target SYSTEM "gdb-target.dtd">
45580 <target version="1.0">
45581 @r{[}@var{architecture}@r{]}
45582 @r{[}@var{osabi}@r{]}
45583 @r{[}@var{compatible}@r{]}
45584 @r{[}@var{feature}@dots{}@r{]}
45589 The description is generally insensitive to whitespace and line
45590 breaks, under the usual common-sense rules. The XML version
45591 declaration and document type declaration can generally be omitted
45592 (@value{GDBN} does not require them), but specifying them may be
45593 useful for XML validation tools. The @samp{version} attribute for
45594 @samp{<target>} may also be omitted, but we recommend
45595 including it; if future versions of @value{GDBN} use an incompatible
45596 revision of @file{gdb-target.dtd}, they will detect and report
45597 the version mismatch.
45599 @subsection Inclusion
45600 @cindex target descriptions, inclusion
45603 @cindex <xi:include>
45606 It can sometimes be valuable to split a target description up into
45607 several different annexes, either for organizational purposes, or to
45608 share files between different possible target descriptions. You can
45609 divide a description into multiple files by replacing any element of
45610 the target description with an inclusion directive of the form:
45613 <xi:include href="@var{document}"/>
45617 When @value{GDBN} encounters an element of this form, it will retrieve
45618 the named XML @var{document}, and replace the inclusion directive with
45619 the contents of that document. If the current description was read
45620 using @samp{qXfer}, then so will be the included document;
45621 @var{document} will be interpreted as the name of an annex. If the
45622 current description was read from a file, @value{GDBN} will look for
45623 @var{document} as a file in the same directory where it found the
45624 original description.
45626 @subsection Architecture
45627 @cindex <architecture>
45629 An @samp{<architecture>} element has this form:
45632 <architecture>@var{arch}</architecture>
45635 @var{arch} is one of the architectures from the set accepted by
45636 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45639 @cindex @code{<osabi>}
45641 This optional field was introduced in @value{GDBN} version 7.0.
45642 Previous versions of @value{GDBN} ignore it.
45644 An @samp{<osabi>} element has this form:
45647 <osabi>@var{abi-name}</osabi>
45650 @var{abi-name} is an OS ABI name from the same selection accepted by
45651 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
45653 @subsection Compatible Architecture
45654 @cindex @code{<compatible>}
45656 This optional field was introduced in @value{GDBN} version 7.0.
45657 Previous versions of @value{GDBN} ignore it.
45659 A @samp{<compatible>} element has this form:
45662 <compatible>@var{arch}</compatible>
45665 @var{arch} is one of the architectures from the set accepted by
45666 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45668 A @samp{<compatible>} element is used to specify that the target
45669 is able to run binaries in some other than the main target architecture
45670 given by the @samp{<architecture>} element. For example, on the
45671 Cell Broadband Engine, the main architecture is @code{powerpc:common}
45672 or @code{powerpc:common64}, but the system is able to run binaries
45673 in the @code{spu} architecture as well. The way to describe this
45674 capability with @samp{<compatible>} is as follows:
45677 <architecture>powerpc:common</architecture>
45678 <compatible>spu</compatible>
45681 @subsection Features
45684 Each @samp{<feature>} describes some logical portion of the target
45685 system. Features are currently used to describe available CPU
45686 registers and the types of their contents. A @samp{<feature>} element
45690 <feature name="@var{name}">
45691 @r{[}@var{type}@dots{}@r{]}
45697 Each feature's name should be unique within the description. The name
45698 of a feature does not matter unless @value{GDBN} has some special
45699 knowledge of the contents of that feature; if it does, the feature
45700 should have its standard name. @xref{Standard Target Features}.
45704 Any register's value is a collection of bits which @value{GDBN} must
45705 interpret. The default interpretation is a two's complement integer,
45706 but other types can be requested by name in the register description.
45707 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
45708 Target Types}), and the description can define additional composite
45711 Each type element must have an @samp{id} attribute, which gives
45712 a unique (within the containing @samp{<feature>}) name to the type.
45713 Types must be defined before they are used.
45716 Some targets offer vector registers, which can be treated as arrays
45717 of scalar elements. These types are written as @samp{<vector>} elements,
45718 specifying the array element type, @var{type}, and the number of elements,
45722 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
45726 If a register's value is usefully viewed in multiple ways, define it
45727 with a union type containing the useful representations. The
45728 @samp{<union>} element contains one or more @samp{<field>} elements,
45729 each of which has a @var{name} and a @var{type}:
45732 <union id="@var{id}">
45733 <field name="@var{name}" type="@var{type}"/>
45740 If a register's value is composed from several separate values, define
45741 it with either a structure type or a flags type.
45742 A flags type may only contain bitfields.
45743 A structure type may either contain only bitfields or contain no bitfields.
45744 If the value contains only bitfields, its total size in bytes must be
45747 Non-bitfield values have a @var{name} and @var{type}.
45750 <struct id="@var{id}">
45751 <field name="@var{name}" type="@var{type}"/>
45756 Both @var{name} and @var{type} values are required.
45757 No implicit padding is added.
45759 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
45762 <struct id="@var{id}" size="@var{size}">
45763 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45769 <flags id="@var{id}" size="@var{size}">
45770 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45775 The @var{name} value is required.
45776 Bitfield values may be named with the empty string, @samp{""},
45777 in which case the field is ``filler'' and its value is not printed.
45778 Not all bits need to be specified, so ``filler'' fields are optional.
45780 The @var{start} and @var{end} values are required, and @var{type}
45782 The field's @var{start} must be less than or equal to its @var{end},
45783 and zero represents the least significant bit.
45785 The default value of @var{type} is @code{bool} for single bit fields,
45786 and an unsigned integer otherwise.
45788 Which to choose? Structures or flags?
45790 Registers defined with @samp{flags} have these advantages over
45791 defining them with @samp{struct}:
45795 Arithmetic may be performed on them as if they were integers.
45797 They are printed in a more readable fashion.
45800 Registers defined with @samp{struct} have one advantage over
45801 defining them with @samp{flags}:
45805 One can fetch individual fields like in @samp{C}.
45808 (gdb) print $my_struct_reg.field3
45814 @subsection Registers
45817 Each register is represented as an element with this form:
45820 <reg name="@var{name}"
45821 bitsize="@var{size}"
45822 @r{[}regnum="@var{num}"@r{]}
45823 @r{[}save-restore="@var{save-restore}"@r{]}
45824 @r{[}type="@var{type}"@r{]}
45825 @r{[}group="@var{group}"@r{]}/>
45829 The components are as follows:
45834 The register's name; it must be unique within the target description.
45837 The register's size, in bits.
45840 The register's number. If omitted, a register's number is one greater
45841 than that of the previous register (either in the current feature or in
45842 a preceding feature); the first register in the target description
45843 defaults to zero. This register number is used to read or write
45844 the register; e.g.@: it is used in the remote @code{p} and @code{P}
45845 packets, and registers appear in the @code{g} and @code{G} packets
45846 in order of increasing register number.
45849 Whether the register should be preserved across inferior function
45850 calls; this must be either @code{yes} or @code{no}. The default is
45851 @code{yes}, which is appropriate for most registers except for
45852 some system control registers; this is not related to the target's
45856 The type of the register. It may be a predefined type, a type
45857 defined in the current feature, or one of the special types @code{int}
45858 and @code{float}. @code{int} is an integer type of the correct size
45859 for @var{bitsize}, and @code{float} is a floating point type (in the
45860 architecture's normal floating point format) of the correct size for
45861 @var{bitsize}. The default is @code{int}.
45864 The register group to which this register belongs. It can be one of the
45865 standard register groups @code{general}, @code{float}, @code{vector} or an
45866 arbitrary string. Group names should be limited to alphanumeric characters.
45867 If a group name is made up of multiple words the words may be separated by
45868 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
45869 @var{group} is specified, @value{GDBN} will not display the register in
45870 @code{info registers}.
45874 @node Predefined Target Types
45875 @section Predefined Target Types
45876 @cindex target descriptions, predefined types
45878 Type definitions in the self-description can build up composite types
45879 from basic building blocks, but can not define fundamental types. Instead,
45880 standard identifiers are provided by @value{GDBN} for the fundamental
45881 types. The currently supported types are:
45886 Boolean type, occupying a single bit.
45894 Signed integer types holding the specified number of bits.
45902 Unsigned integer types holding the specified number of bits.
45906 Pointers to unspecified code and data. The program counter and
45907 any dedicated return address register may be marked as code
45908 pointers; printing a code pointer converts it into a symbolic
45909 address. The stack pointer and any dedicated address registers
45910 may be marked as data pointers.
45913 Single precision IEEE floating point.
45916 Double precision IEEE floating point.
45919 The 12-byte extended precision format used by ARM FPA registers.
45922 The 10-byte extended precision format used by x87 registers.
45925 32bit @sc{eflags} register used by x86.
45928 32bit @sc{mxcsr} register used by x86.
45932 @node Enum Target Types
45933 @section Enum Target Types
45934 @cindex target descriptions, enum types
45936 Enum target types are useful in @samp{struct} and @samp{flags}
45937 register descriptions. @xref{Target Description Format}.
45939 Enum types have a name, size and a list of name/value pairs.
45942 <enum id="@var{id}" size="@var{size}">
45943 <evalue name="@var{name}" value="@var{value}"/>
45948 Enums must be defined before they are used.
45951 <enum id="levels_type" size="4">
45952 <evalue name="low" value="0"/>
45953 <evalue name="high" value="1"/>
45955 <flags id="flags_type" size="4">
45956 <field name="X" start="0"/>
45957 <field name="LEVEL" start="1" end="1" type="levels_type"/>
45959 <reg name="flags" bitsize="32" type="flags_type"/>
45962 Given that description, a value of 3 for the @samp{flags} register
45963 would be printed as:
45966 (gdb) info register flags
45967 flags 0x3 [ X LEVEL=high ]
45970 @node Standard Target Features
45971 @section Standard Target Features
45972 @cindex target descriptions, standard features
45974 A target description must contain either no registers or all the
45975 target's registers. If the description contains no registers, then
45976 @value{GDBN} will assume a default register layout, selected based on
45977 the architecture. If the description contains any registers, the
45978 default layout will not be used; the standard registers must be
45979 described in the target description, in such a way that @value{GDBN}
45980 can recognize them.
45982 This is accomplished by giving specific names to feature elements
45983 which contain standard registers. @value{GDBN} will look for features
45984 with those names and verify that they contain the expected registers;
45985 if any known feature is missing required registers, or if any required
45986 feature is missing, @value{GDBN} will reject the target
45987 description. You can add additional registers to any of the
45988 standard features --- @value{GDBN} will display them just as if
45989 they were added to an unrecognized feature.
45991 This section lists the known features and their expected contents.
45992 Sample XML documents for these features are included in the
45993 @value{GDBN} source tree, in the directory @file{gdb/features}.
45995 Names recognized by @value{GDBN} should include the name of the
45996 company or organization which selected the name, and the overall
45997 architecture to which the feature applies; so e.g.@: the feature
45998 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46000 The names of registers are not case sensitive for the purpose
46001 of recognizing standard features, but @value{GDBN} will only display
46002 registers using the capitalization used in the description.
46005 * AArch64 Features::
46009 * MicroBlaze Features::
46013 * Nios II Features::
46014 * OpenRISC 1000 Features::
46015 * PowerPC Features::
46016 * RISC-V Features::
46018 * S/390 and System z Features::
46024 @node AArch64 Features
46025 @subsection AArch64 Features
46026 @cindex target descriptions, AArch64 features
46028 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46029 targets. It should contain registers @samp{x0} through @samp{x30},
46030 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46032 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46033 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46036 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46037 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46038 through @samp{p15}, @samp{ffr} and @samp{vg}.
46040 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46041 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46044 @subsection ARC Features
46045 @cindex target descriptions, ARC Features
46047 ARC processors are so configurable that even core registers and their numbers
46048 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46049 registers, which are important to @value{GDBN}, are not ``core'' registers in
46050 ARC. Therefore, there are two features that their presence is mandatory:
46051 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46053 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46058 @samp{r0} through @samp{r25} for normal register file targets.
46060 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46061 register file targets.
46063 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46064 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46067 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46068 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46069 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46070 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46071 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46072 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46073 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46074 because of their inaccessibility during user space debugging sessions.
46076 Extension core registers @samp{r32} through @samp{r59} are optional and their
46077 existence depends on the configuration. When debugging GNU/Linux applications,
46078 i.e.@: user space debugging, these core registers are not available.
46080 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46081 is the list of registers pertinent to this feature:
46085 mandatory: @samp{pc} and @samp{status32}.
46087 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46091 @subsection ARM Features
46092 @cindex target descriptions, ARM features
46094 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46096 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46097 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46099 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46100 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46101 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46104 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46105 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46107 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46108 it should contain at least registers @samp{wR0} through @samp{wR15} and
46109 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46110 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46112 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46113 should contain at least registers @samp{d0} through @samp{d15}. If
46114 they are present, @samp{d16} through @samp{d31} should also be included.
46115 @value{GDBN} will synthesize the single-precision registers from
46116 halves of the double-precision registers.
46118 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46119 need to contain registers; it instructs @value{GDBN} to display the
46120 VFP double-precision registers as vectors and to synthesize the
46121 quad-precision registers from pairs of double-precision registers.
46122 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46123 be present and include 32 double-precision registers.
46125 @node i386 Features
46126 @subsection i386 Features
46127 @cindex target descriptions, i386 features
46129 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46130 targets. It should describe the following registers:
46134 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46136 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46138 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46139 @samp{fs}, @samp{gs}
46141 @samp{st0} through @samp{st7}
46143 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46144 @samp{foseg}, @samp{fooff} and @samp{fop}
46147 The register sets may be different, depending on the target.
46149 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46150 describe registers:
46154 @samp{xmm0} through @samp{xmm7} for i386
46156 @samp{xmm0} through @samp{xmm15} for amd64
46161 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46162 @samp{org.gnu.gdb.i386.sse} feature. It should
46163 describe the upper 128 bits of @sc{ymm} registers:
46167 @samp{ymm0h} through @samp{ymm7h} for i386
46169 @samp{ymm0h} through @samp{ymm15h} for amd64
46172 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
46173 Memory Protection Extension (MPX). It should describe the following registers:
46177 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
46179 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
46182 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
46183 describe a single register, @samp{orig_eax}.
46185 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
46186 describe two system registers: @samp{fs_base} and @samp{gs_base}.
46188 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
46189 @samp{org.gnu.gdb.i386.avx} feature. It should
46190 describe additional @sc{xmm} registers:
46194 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
46197 It should describe the upper 128 bits of additional @sc{ymm} registers:
46201 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
46205 describe the upper 256 bits of @sc{zmm} registers:
46209 @samp{zmm0h} through @samp{zmm7h} for i386.
46211 @samp{zmm0h} through @samp{zmm15h} for amd64.
46215 describe the additional @sc{zmm} registers:
46219 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
46222 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
46223 describe a single register, @samp{pkru}. It is a 32-bit register
46224 valid for i386 and amd64.
46226 @node MicroBlaze Features
46227 @subsection MicroBlaze Features
46228 @cindex target descriptions, MicroBlaze features
46230 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
46231 targets. It should contain registers @samp{r0} through @samp{r31},
46232 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
46233 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
46234 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
46236 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
46237 If present, it should contain registers @samp{rshr} and @samp{rslr}
46239 @node MIPS Features
46240 @subsection @acronym{MIPS} Features
46241 @cindex target descriptions, @acronym{MIPS} features
46243 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
46244 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
46245 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
46248 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
46249 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
46250 registers. They may be 32-bit or 64-bit depending on the target.
46252 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
46253 it may be optional in a future version of @value{GDBN}. It should
46254 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
46255 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
46257 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
46258 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
46259 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
46260 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
46262 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
46263 contain a single register, @samp{restart}, which is used by the
46264 Linux kernel to control restartable syscalls.
46266 @node M68K Features
46267 @subsection M68K Features
46268 @cindex target descriptions, M68K features
46271 @item @samp{org.gnu.gdb.m68k.core}
46272 @itemx @samp{org.gnu.gdb.coldfire.core}
46273 @itemx @samp{org.gnu.gdb.fido.core}
46274 One of those features must be always present.
46275 The feature that is present determines which flavor of m68k is
46276 used. The feature that is present should contain registers
46277 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
46278 @samp{sp}, @samp{ps} and @samp{pc}.
46280 @item @samp{org.gnu.gdb.coldfire.fp}
46281 This feature is optional. If present, it should contain registers
46282 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
46285 Note that, despite the fact that this feature's name says
46286 @samp{coldfire}, it is used to describe any floating point registers.
46287 The size of the registers must match the main m68k flavor; so, for
46288 example, if the primary feature is reported as @samp{coldfire}, then
46289 64-bit floating point registers are required.
46292 @node NDS32 Features
46293 @subsection NDS32 Features
46294 @cindex target descriptions, NDS32 features
46296 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
46297 targets. It should contain at least registers @samp{r0} through
46298 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
46301 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
46302 it should contain 64-bit double-precision floating-point registers
46303 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
46304 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
46306 @emph{Note:} The first sixteen 64-bit double-precision floating-point
46307 registers are overlapped with the thirty-two 32-bit single-precision
46308 floating-point registers. The 32-bit single-precision registers, if
46309 not being listed explicitly, will be synthesized from halves of the
46310 overlapping 64-bit double-precision registers. Listing 32-bit
46311 single-precision registers explicitly is deprecated, and the
46312 support to it could be totally removed some day.
46314 @node Nios II Features
46315 @subsection Nios II Features
46316 @cindex target descriptions, Nios II features
46318 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
46319 targets. It should contain the 32 core registers (@samp{zero},
46320 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
46321 @samp{pc}, and the 16 control registers (@samp{status} through
46324 @node OpenRISC 1000 Features
46325 @subsection Openrisc 1000 Features
46326 @cindex target descriptions, OpenRISC 1000 features
46328 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
46329 targets. It should contain the 32 general purpose registers (@samp{r0}
46330 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
46332 @node PowerPC Features
46333 @subsection PowerPC Features
46334 @cindex target descriptions, PowerPC features
46336 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
46337 targets. It should contain registers @samp{r0} through @samp{r31},
46338 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
46339 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
46341 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
46342 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
46344 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
46345 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
46346 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
46347 through @samp{v31} as aliases for the corresponding @samp{vrX}
46350 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
46351 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
46352 combine these registers with the floating point registers (@samp{f0}
46353 through @samp{f31}) and the altivec registers (@samp{vr0} through
46354 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
46355 @samp{vs63}, the set of vector-scalar registers for POWER7.
46356 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
46357 @samp{org.gnu.gdb.power.altivec}.
46359 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
46360 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
46361 @samp{spefscr}. SPE targets should provide 32-bit registers in
46362 @samp{org.gnu.gdb.power.core} and provide the upper halves in
46363 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
46364 these to present registers @samp{ev0} through @samp{ev31} to the
46367 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
46368 contain the 64-bit register @samp{ppr}.
46370 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
46371 contain the 64-bit register @samp{dscr}.
46373 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
46374 contain the 64-bit register @samp{tar}.
46376 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
46377 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
46380 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
46381 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
46382 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
46383 server PMU registers provided by @sc{gnu}/Linux.
46385 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
46386 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
46389 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
46390 contain the checkpointed general-purpose registers @samp{cr0} through
46391 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
46392 @samp{cctr}. These registers may all be either 32-bit or 64-bit
46393 depending on the target. It should also contain the checkpointed
46394 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
46397 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
46398 contain the checkpointed 64-bit floating-point registers @samp{cf0}
46399 through @samp{cf31}, as well as the checkpointed 64-bit register
46402 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
46403 should contain the checkpointed altivec registers @samp{cvr0} through
46404 @samp{cvr31}, all 128-bit wide. It should also contain the
46405 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
46408 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
46409 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
46410 will combine these registers with the checkpointed floating point
46411 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
46412 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
46413 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
46414 @samp{cvs63}. Therefore, this feature requires both
46415 @samp{org.gnu.gdb.power.htm.altivec} and
46416 @samp{org.gnu.gdb.power.htm.fpu}.
46418 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
46419 contain the 64-bit checkpointed register @samp{cppr}.
46421 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
46422 contain the 64-bit checkpointed register @samp{cdscr}.
46424 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
46425 contain the 64-bit checkpointed register @samp{ctar}.
46428 @node RISC-V Features
46429 @subsection RISC-V Features
46430 @cindex target descriptions, RISC-V Features
46432 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
46433 targets. It should contain the registers @samp{x0} through
46434 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
46435 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
46438 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
46439 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
46440 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
46441 architectural register names, or the ABI names can be used.
46443 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
46444 it should contain registers that are not backed by real registers on
46445 the target, but are instead virtual, where the register value is
46446 derived from other target state. In many ways these are like
46447 @value{GDBN}s pseudo-registers, except implemented by the target.
46448 Currently the only register expected in this set is the one byte
46449 @samp{priv} register that contains the target's privilege level in the
46450 least significant two bits.
46452 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
46453 should contain all of the target's standard CSRs. Standard CSRs are
46454 those defined in the RISC-V specification documents. There is some
46455 overlap between this feature and the fpu feature; the @samp{fflags},
46456 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
46457 expectation is that these registers will be in the fpu feature if the
46458 target has floating point hardware, but can be moved into the csr
46459 feature if the target has the floating point control registers, but no
46460 other floating point hardware.
46462 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
46463 it should contain registers @samp{v0} through @samp{v31}, all of which
46464 must be the same size. These requirements are based on the v0.10
46465 draft vector extension, as the vector extension is not yet final. In
46466 the event that the register set of the vector extension changes for
46467 the final specification, the requirements given here could change for
46468 future releases of @value{GDBN}.
46471 @subsection RX Features
46472 @cindex target descriptions, RX Features
46474 The @samp{org.gnu.gdb.rx.core} feature is required for RX
46475 targets. It should contain the registers @samp{r0} through
46476 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
46477 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
46479 @node S/390 and System z Features
46480 @subsection S/390 and System z Features
46481 @cindex target descriptions, S/390 features
46482 @cindex target descriptions, System z features
46484 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
46485 System z targets. It should contain the PSW and the 16 general
46486 registers. In particular, System z targets should provide the 64-bit
46487 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
46488 S/390 targets should provide the 32-bit versions of these registers.
46489 A System z target that runs in 31-bit addressing mode should provide
46490 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
46491 register's upper halves @samp{r0h} through @samp{r15h}, and their
46492 lower halves @samp{r0l} through @samp{r15l}.
46494 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
46495 contain the 64-bit registers @samp{f0} through @samp{f15}, and
46498 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
46499 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
46501 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
46502 contain the register @samp{orig_r2}, which is 64-bit wide on System z
46503 targets and 32-bit otherwise. In addition, the feature may contain
46504 the @samp{last_break} register, whose width depends on the addressing
46505 mode, as well as the @samp{system_call} register, which is always
46508 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
46509 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
46510 @samp{atia}, and @samp{tr0} through @samp{tr15}.
46512 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
46513 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
46514 combined by @value{GDBN} with the floating point registers @samp{f0}
46515 through @samp{f15} to present the 128-bit wide vector registers
46516 @samp{v0} through @samp{v15}. In addition, this feature should
46517 contain the 128-bit wide vector registers @samp{v16} through
46520 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
46521 the 64-bit wide guarded-storage-control registers @samp{gsd},
46522 @samp{gssm}, and @samp{gsepla}.
46524 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
46525 the 64-bit wide guarded-storage broadcast control registers
46526 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
46528 @node Sparc Features
46529 @subsection Sparc Features
46530 @cindex target descriptions, sparc32 features
46531 @cindex target descriptions, sparc64 features
46532 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
46533 targets. It should describe the following registers:
46537 @samp{g0} through @samp{g7}
46539 @samp{o0} through @samp{o7}
46541 @samp{l0} through @samp{l7}
46543 @samp{i0} through @samp{i7}
46546 They may be 32-bit or 64-bit depending on the target.
46548 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
46549 targets. It should describe the following registers:
46553 @samp{f0} through @samp{f31}
46555 @samp{f32} through @samp{f62} for sparc64
46558 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
46559 targets. It should describe the following registers:
46563 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
46564 @samp{fsr}, and @samp{csr} for sparc32
46566 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
46570 @node TIC6x Features
46571 @subsection TMS320C6x Features
46572 @cindex target descriptions, TIC6x features
46573 @cindex target descriptions, TMS320C6x features
46574 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
46575 targets. It should contain registers @samp{A0} through @samp{A15},
46576 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
46578 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
46579 contain registers @samp{A16} through @samp{A31} and @samp{B16}
46580 through @samp{B31}.
46582 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
46583 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
46585 @node Operating System Information
46586 @appendix Operating System Information
46587 @cindex operating system information
46589 Users of @value{GDBN} often wish to obtain information about the state of
46590 the operating system running on the target---for example the list of
46591 processes, or the list of open files. This section describes the
46592 mechanism that makes it possible. This mechanism is similar to the
46593 target features mechanism (@pxref{Target Descriptions}), but focuses
46594 on a different aspect of target.
46596 Operating system information is retrieved from the target via the
46597 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
46598 read}). The object name in the request should be @samp{osdata}, and
46599 the @var{annex} identifies the data to be fetched.
46606 @appendixsection Process list
46607 @cindex operating system information, process list
46609 When requesting the process list, the @var{annex} field in the
46610 @samp{qXfer} request should be @samp{processes}. The returned data is
46611 an XML document. The formal syntax of this document is defined in
46612 @file{gdb/features/osdata.dtd}.
46614 An example document is:
46617 <?xml version="1.0"?>
46618 <!DOCTYPE target SYSTEM "osdata.dtd">
46619 <osdata type="processes">
46621 <column name="pid">1</column>
46622 <column name="user">root</column>
46623 <column name="command">/sbin/init</column>
46624 <column name="cores">1,2,3</column>
46629 Each item should include a column whose name is @samp{pid}. The value
46630 of that column should identify the process on the target. The
46631 @samp{user} and @samp{command} columns are optional, and will be
46632 displayed by @value{GDBN}. The @samp{cores} column, if present,
46633 should contain a comma-separated list of cores that this process
46634 is running on. Target may provide additional columns,
46635 which @value{GDBN} currently ignores.
46637 @node Trace File Format
46638 @appendix Trace File Format
46639 @cindex trace file format
46641 The trace file comes in three parts: a header, a textual description
46642 section, and a trace frame section with binary data.
46644 The header has the form @code{\x7fTRACE0\n}. The first byte is
46645 @code{0x7f} so as to indicate that the file contains binary data,
46646 while the @code{0} is a version number that may have different values
46649 The description section consists of multiple lines of @sc{ascii} text
46650 separated by newline characters (@code{0xa}). The lines may include a
46651 variety of optional descriptive or context-setting information, such
46652 as tracepoint definitions or register set size. @value{GDBN} will
46653 ignore any line that it does not recognize. An empty line marks the end
46658 Specifies the size of a register block in bytes. This is equal to the
46659 size of a @code{g} packet payload in the remote protocol. @var{size}
46660 is an ascii decimal number. There should be only one such line in
46661 a single trace file.
46663 @item status @var{status}
46664 Trace status. @var{status} has the same format as a @code{qTStatus}
46665 remote packet reply. There should be only one such line in a single trace
46668 @item tp @var{payload}
46669 Tracepoint definition. The @var{payload} has the same format as
46670 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
46671 may take multiple lines of definition, corresponding to the multiple
46674 @item tsv @var{payload}
46675 Trace state variable definition. The @var{payload} has the same format as
46676 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
46677 may take multiple lines of definition, corresponding to the multiple
46680 @item tdesc @var{payload}
46681 Target description in XML format. The @var{payload} is a single line of
46682 the XML file. All such lines should be concatenated together to get
46683 the original XML file. This file is in the same format as @code{qXfer}
46684 @code{features} payload, and corresponds to the main @code{target.xml}
46685 file. Includes are not allowed.
46689 The trace frame section consists of a number of consecutive frames.
46690 Each frame begins with a two-byte tracepoint number, followed by a
46691 four-byte size giving the amount of data in the frame. The data in
46692 the frame consists of a number of blocks, each introduced by a
46693 character indicating its type (at least register, memory, and trace
46694 state variable). The data in this section is raw binary, not a
46695 hexadecimal or other encoding; its endianness matches the target's
46698 @c FIXME bi-arch may require endianness/arch info in description section
46701 @item R @var{bytes}
46702 Register block. The number and ordering of bytes matches that of a
46703 @code{g} packet in the remote protocol. Note that these are the
46704 actual bytes, in target order, not a hexadecimal encoding.
46706 @item M @var{address} @var{length} @var{bytes}...
46707 Memory block. This is a contiguous block of memory, at the 8-byte
46708 address @var{address}, with a 2-byte length @var{length}, followed by
46709 @var{length} bytes.
46711 @item V @var{number} @var{value}
46712 Trace state variable block. This records the 8-byte signed value
46713 @var{value} of trace state variable numbered @var{number}.
46717 Future enhancements of the trace file format may include additional types
46720 @node Index Section Format
46721 @appendix @code{.gdb_index} section format
46722 @cindex .gdb_index section format
46723 @cindex index section format
46725 This section documents the index section that is created by @code{save
46726 gdb-index} (@pxref{Index Files}). The index section is
46727 DWARF-specific; some knowledge of DWARF is assumed in this
46730 The mapped index file format is designed to be directly
46731 @code{mmap}able on any architecture. In most cases, a datum is
46732 represented using a little-endian 32-bit integer value, called an
46733 @code{offset_type}. Big endian machines must byte-swap the values
46734 before using them. Exceptions to this rule are noted. The data is
46735 laid out such that alignment is always respected.
46737 A mapped index consists of several areas, laid out in order.
46741 The file header. This is a sequence of values, of @code{offset_type}
46742 unless otherwise noted:
46746 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
46747 Version 4 uses a different hashing function from versions 5 and 6.
46748 Version 6 includes symbols for inlined functions, whereas versions 4
46749 and 5 do not. Version 7 adds attributes to the CU indices in the
46750 symbol table. Version 8 specifies that symbols from DWARF type units
46751 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
46752 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
46754 @value{GDBN} will only read version 4, 5, or 6 indices
46755 by specifying @code{set use-deprecated-index-sections on}.
46756 GDB has a workaround for potentially broken version 7 indices so it is
46757 currently not flagged as deprecated.
46760 The offset, from the start of the file, of the CU list.
46763 The offset, from the start of the file, of the types CU list. Note
46764 that this area can be empty, in which case this offset will be equal
46765 to the next offset.
46768 The offset, from the start of the file, of the address area.
46771 The offset, from the start of the file, of the symbol table.
46774 The offset, from the start of the file, of the constant pool.
46778 The CU list. This is a sequence of pairs of 64-bit little-endian
46779 values, sorted by the CU offset. The first element in each pair is
46780 the offset of a CU in the @code{.debug_info} section. The second
46781 element in each pair is the length of that CU. References to a CU
46782 elsewhere in the map are done using a CU index, which is just the
46783 0-based index into this table. Note that if there are type CUs, then
46784 conceptually CUs and type CUs form a single list for the purposes of
46788 The types CU list. This is a sequence of triplets of 64-bit
46789 little-endian values. In a triplet, the first value is the CU offset,
46790 the second value is the type offset in the CU, and the third value is
46791 the type signature. The types CU list is not sorted.
46794 The address area. The address area consists of a sequence of address
46795 entries. Each address entry has three elements:
46799 The low address. This is a 64-bit little-endian value.
46802 The high address. This is a 64-bit little-endian value. Like
46803 @code{DW_AT_high_pc}, the value is one byte beyond the end.
46806 The CU index. This is an @code{offset_type} value.
46810 The symbol table. This is an open-addressed hash table. The size of
46811 the hash table is always a power of 2.
46813 Each slot in the hash table consists of a pair of @code{offset_type}
46814 values. The first value is the offset of the symbol's name in the
46815 constant pool. The second value is the offset of the CU vector in the
46818 If both values are 0, then this slot in the hash table is empty. This
46819 is ok because while 0 is a valid constant pool index, it cannot be a
46820 valid index for both a string and a CU vector.
46822 The hash value for a table entry is computed by applying an
46823 iterative hash function to the symbol's name. Starting with an
46824 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
46825 the string is incorporated into the hash using the formula depending on the
46830 The formula is @code{r = r * 67 + c - 113}.
46832 @item Versions 5 to 7
46833 The formula is @code{r = r * 67 + tolower (c) - 113}.
46836 The terminating @samp{\0} is not incorporated into the hash.
46838 The step size used in the hash table is computed via
46839 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
46840 value, and @samp{size} is the size of the hash table. The step size
46841 is used to find the next candidate slot when handling a hash
46844 The names of C@t{++} symbols in the hash table are canonicalized. We
46845 don't currently have a simple description of the canonicalization
46846 algorithm; if you intend to create new index sections, you must read
46850 The constant pool. This is simply a bunch of bytes. It is organized
46851 so that alignment is correct: CU vectors are stored first, followed by
46854 A CU vector in the constant pool is a sequence of @code{offset_type}
46855 values. The first value is the number of CU indices in the vector.
46856 Each subsequent value is the index and symbol attributes of a CU in
46857 the CU list. This element in the hash table is used to indicate which
46858 CUs define the symbol and how the symbol is used.
46859 See below for the format of each CU index+attributes entry.
46861 A string in the constant pool is zero-terminated.
46864 Attributes were added to CU index values in @code{.gdb_index} version 7.
46865 If a symbol has multiple uses within a CU then there is one
46866 CU index+attributes value for each use.
46868 The format of each CU index+attributes entry is as follows
46874 This is the index of the CU in the CU list.
46876 These bits are reserved for future purposes and must be zero.
46878 The kind of the symbol in the CU.
46882 This value is reserved and should not be used.
46883 By reserving zero the full @code{offset_type} value is backwards compatible
46884 with previous versions of the index.
46886 The symbol is a type.
46888 The symbol is a variable or an enum value.
46890 The symbol is a function.
46892 Any other kind of symbol.
46894 These values are reserved.
46898 This bit is zero if the value is global and one if it is static.
46900 The determination of whether a symbol is global or static is complicated.
46901 The authorative reference is the file @file{dwarf2read.c} in
46902 @value{GDBN} sources.
46906 This pseudo-code describes the computation of a symbol's kind and
46907 global/static attributes in the index.
46910 is_external = get_attribute (die, DW_AT_external);
46911 language = get_attribute (cu_die, DW_AT_language);
46914 case DW_TAG_typedef:
46915 case DW_TAG_base_type:
46916 case DW_TAG_subrange_type:
46920 case DW_TAG_enumerator:
46922 is_static = language != CPLUS;
46924 case DW_TAG_subprogram:
46926 is_static = ! (is_external || language == ADA);
46928 case DW_TAG_constant:
46930 is_static = ! is_external;
46932 case DW_TAG_variable:
46934 is_static = ! is_external;
46936 case DW_TAG_namespace:
46940 case DW_TAG_class_type:
46941 case DW_TAG_interface_type:
46942 case DW_TAG_structure_type:
46943 case DW_TAG_union_type:
46944 case DW_TAG_enumeration_type:
46946 is_static = language != CPLUS;
46954 @appendix Manual pages
46958 * gdb man:: The GNU Debugger man page
46959 * gdbserver man:: Remote Server for the GNU Debugger man page
46960 * gcore man:: Generate a core file of a running program
46961 * gdbinit man:: gdbinit scripts
46962 * gdb-add-index man:: Add index files to speed up GDB
46968 @c man title gdb The GNU Debugger
46970 @c man begin SYNOPSIS gdb
46971 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
46972 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
46973 [@option{-b}@w{ }@var{bps}]
46974 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
46975 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
46976 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
46977 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
46978 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
46981 @c man begin DESCRIPTION gdb
46982 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
46983 going on ``inside'' another program while it executes -- or what another
46984 program was doing at the moment it crashed.
46986 @value{GDBN} can do four main kinds of things (plus other things in support of
46987 these) to help you catch bugs in the act:
46991 Start your program, specifying anything that might affect its behavior.
46994 Make your program stop on specified conditions.
46997 Examine what has happened, when your program has stopped.
47000 Change things in your program, so you can experiment with correcting the
47001 effects of one bug and go on to learn about another.
47004 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47007 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47008 commands from the terminal until you tell it to exit with the @value{GDBN}
47009 command @code{quit}. You can get online help from @value{GDBN} itself
47010 by using the command @code{help}.
47012 You can run @code{gdb} with no arguments or options; but the most
47013 usual way to start @value{GDBN} is with one argument or two, specifying an
47014 executable program as the argument:
47020 You can also start with both an executable program and a core file specified:
47026 You can, instead, specify a process ID as a second argument or use option
47027 @code{-p}, if you want to debug a running process:
47035 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47036 can omit the @var{program} filename.
47038 Here are some of the most frequently needed @value{GDBN} commands:
47040 @c pod2man highlights the right hand side of the @item lines.
47042 @item break [@var{file}:]@var{function}
47043 Set a breakpoint at @var{function} (in @var{file}).
47045 @item run [@var{arglist}]
47046 Start your program (with @var{arglist}, if specified).
47049 Backtrace: display the program stack.
47051 @item print @var{expr}
47052 Display the value of an expression.
47055 Continue running your program (after stopping, e.g.@: at a breakpoint).
47058 Execute next program line (after stopping); step @emph{over} any
47059 function calls in the line.
47061 @item edit [@var{file}:]@var{function}
47062 look at the program line where it is presently stopped.
47064 @item list [@var{file}:]@var{function}
47065 type the text of the program in the vicinity of where it is presently stopped.
47068 Execute next program line (after stopping); step @emph{into} any
47069 function calls in the line.
47071 @item help [@var{name}]
47072 Show information about @value{GDBN} command @var{name}, or general information
47073 about using @value{GDBN}.
47076 Exit from @value{GDBN}.
47080 For full details on @value{GDBN},
47081 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47082 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47083 as the @code{gdb} entry in the @code{info} program.
47087 @c man begin OPTIONS gdb
47088 Any arguments other than options specify an executable
47089 file and core file (or process ID); that is, the first argument
47090 encountered with no
47091 associated option flag is equivalent to a @option{-se} option, and the second,
47092 if any, is equivalent to a @option{-c} option if it's the name of a file.
47094 both long and short forms; both are shown here. The long forms are also
47095 recognized if you truncate them, so long as enough of the option is
47096 present to be unambiguous. (If you prefer, you can flag option
47097 arguments with @option{+} rather than @option{-}, though we illustrate the
47098 more usual convention.)
47100 All the options and command line arguments you give are processed
47101 in sequential order. The order makes a difference when the @option{-x}
47107 List all options, with brief explanations.
47109 @item -symbols=@var{file}
47110 @itemx -s @var{file}
47111 Read symbol table from file @var{file}.
47114 Enable writing into executable and core files.
47116 @item -exec=@var{file}
47117 @itemx -e @var{file}
47118 Use file @var{file} as the executable file to execute when
47119 appropriate, and for examining pure data in conjunction with a core
47122 @item -se=@var{file}
47123 Read symbol table from file @var{file} and use it as the executable
47126 @item -core=@var{file}
47127 @itemx -c @var{file}
47128 Use file @var{file} as a core dump to examine.
47130 @item -command=@var{file}
47131 @itemx -x @var{file}
47132 Execute @value{GDBN} commands from file @var{file}.
47134 @item -ex @var{command}
47135 Execute given @value{GDBN} @var{command}.
47137 @item -directory=@var{directory}
47138 @itemx -d @var{directory}
47139 Add @var{directory} to the path to search for source files.
47142 Do not execute commands from @file{~/.config/gdb/gdbinit},
47143 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
47144 @file{~/.gdbearlyinit}
47148 Do not execute commands from any @file{.gdbinit} or
47149 @file{.gdbearlyinit} initialization files.
47153 ``Quiet''. Do not print the introductory and copyright messages. These
47154 messages are also suppressed in batch mode.
47157 Run in batch mode. Exit with status @code{0} after processing all the command
47158 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
47159 Exit with nonzero status if an error occurs in executing the @value{GDBN}
47160 commands in the command files.
47162 Batch mode may be useful for running @value{GDBN} as a filter, for example to
47163 download and run a program on another computer; in order to make this
47164 more useful, the message
47167 Program exited normally.
47171 (which is ordinarily issued whenever a program running under @value{GDBN} control
47172 terminates) is not issued when running in batch mode.
47174 @item -cd=@var{directory}
47175 Run @value{GDBN} using @var{directory} as its working directory,
47176 instead of the current directory.
47180 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
47181 @value{GDBN} to output the full file name and line number in a standard,
47182 recognizable fashion each time a stack frame is displayed (which
47183 includes each time the program stops). This recognizable format looks
47184 like two @samp{\032} characters, followed by the file name, line number
47185 and character position separated by colons, and a newline. The
47186 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
47187 characters as a signal to display the source code for the frame.
47190 Set the line speed (baud rate or bits per second) of any serial
47191 interface used by @value{GDBN} for remote debugging.
47193 @item -tty=@var{device}
47194 Run using @var{device} for your program's standard input and output.
47198 @c man begin SEEALSO gdb
47200 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47201 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47202 documentation are properly installed at your site, the command
47209 should give you access to the complete manual.
47211 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47212 Richard M. Stallman and Roland H. Pesch, July 1991.
47216 @node gdbserver man
47217 @heading gdbserver man
47219 @c man title gdbserver Remote Server for the GNU Debugger
47221 @c man begin SYNOPSIS gdbserver
47222 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47224 gdbserver --attach @var{comm} @var{pid}
47226 gdbserver --multi @var{comm}
47230 @c man begin DESCRIPTION gdbserver
47231 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
47232 than the one which is running the program being debugged.
47235 @subheading Usage (server (target) side)
47238 Usage (server (target) side):
47241 First, you need to have a copy of the program you want to debug put onto
47242 the target system. The program can be stripped to save space if needed, as
47243 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
47244 the @value{GDBN} running on the host system.
47246 To use the server, you log on to the target system, and run the @command{gdbserver}
47247 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
47248 your program, and (c) its arguments. The general syntax is:
47251 target> gdbserver @var{comm} @var{program} [@var{args} ...]
47254 For example, using a serial port, you might say:
47258 @c @file would wrap it as F</dev/com1>.
47259 target> gdbserver /dev/com1 emacs foo.txt
47262 target> gdbserver @file{/dev/com1} emacs foo.txt
47266 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
47267 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
47268 waits patiently for the host @value{GDBN} to communicate with it.
47270 To use a TCP connection, you could say:
47273 target> gdbserver host:2345 emacs foo.txt
47276 This says pretty much the same thing as the last example, except that we are
47277 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
47278 that we are expecting to see a TCP connection from @code{host} to local TCP port
47279 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
47280 want for the port number as long as it does not conflict with any existing TCP
47281 ports on the target system. This same port number must be used in the host
47282 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
47283 you chose a port number that conflicts with another service, @command{gdbserver} will
47284 print an error message and exit.
47286 @command{gdbserver} can also attach to running programs.
47287 This is accomplished via the @option{--attach} argument. The syntax is:
47290 target> gdbserver --attach @var{comm} @var{pid}
47293 @var{pid} is the process ID of a currently running process. It isn't
47294 necessary to point @command{gdbserver} at a binary for the running process.
47296 To start @code{gdbserver} without supplying an initial command to run
47297 or process ID to attach, use the @option{--multi} command line option.
47298 In such case you should connect using @kbd{target extended-remote} to start
47299 the program you want to debug.
47302 target> gdbserver --multi @var{comm}
47306 @subheading Usage (host side)
47312 You need an unstripped copy of the target program on your host system, since
47313 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
47314 would, with the target program as the first argument. (You may need to use the
47315 @option{--baud} option if the serial line is running at anything except 9600 baud.)
47316 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
47317 new command you need to know about is @code{target remote}
47318 (or @code{target extended-remote}). Its argument is either
47319 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
47320 descriptor. For example:
47324 @c @file would wrap it as F</dev/ttyb>.
47325 (gdb) target remote /dev/ttyb
47328 (gdb) target remote @file{/dev/ttyb}
47333 communicates with the server via serial line @file{/dev/ttyb}, and:
47336 (gdb) target remote the-target:2345
47340 communicates via a TCP connection to port 2345 on host `the-target', where
47341 you previously started up @command{gdbserver} with the same port number. Note that for
47342 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
47343 command, otherwise you may get an error that looks something like
47344 `Connection refused'.
47346 @command{gdbserver} can also debug multiple inferiors at once,
47349 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
47350 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
47353 @ref{Inferiors Connections and Programs}.
47355 In such case use the @code{extended-remote} @value{GDBN} command variant:
47358 (gdb) target extended-remote the-target:2345
47361 The @command{gdbserver} option @option{--multi} may or may not be used in such
47365 @c man begin OPTIONS gdbserver
47366 There are three different modes for invoking @command{gdbserver}:
47371 Debug a specific program specified by its program name:
47374 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47377 The @var{comm} parameter specifies how should the server communicate
47378 with @value{GDBN}; it is either a device name (to use a serial line),
47379 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
47380 stdin/stdout of @code{gdbserver}. Specify the name of the program to
47381 debug in @var{prog}. Any remaining arguments will be passed to the
47382 program verbatim. When the program exits, @value{GDBN} will close the
47383 connection, and @code{gdbserver} will exit.
47386 Debug a specific program by specifying the process ID of a running
47390 gdbserver --attach @var{comm} @var{pid}
47393 The @var{comm} parameter is as described above. Supply the process ID
47394 of a running program in @var{pid}; @value{GDBN} will do everything
47395 else. Like with the previous mode, when the process @var{pid} exits,
47396 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
47399 Multi-process mode -- debug more than one program/process:
47402 gdbserver --multi @var{comm}
47405 In this mode, @value{GDBN} can instruct @command{gdbserver} which
47406 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
47407 close the connection when a process being debugged exits, so you can
47408 debug several processes in the same session.
47411 In each of the modes you may specify these options:
47416 List all options, with brief explanations.
47419 This option causes @command{gdbserver} to print its version number and exit.
47422 @command{gdbserver} will attach to a running program. The syntax is:
47425 target> gdbserver --attach @var{comm} @var{pid}
47428 @var{pid} is the process ID of a currently running process. It isn't
47429 necessary to point @command{gdbserver} at a binary for the running process.
47432 To start @code{gdbserver} without supplying an initial command to run
47433 or process ID to attach, use this command line option.
47434 Then you can connect using @kbd{target extended-remote} and start
47435 the program you want to debug. The syntax is:
47438 target> gdbserver --multi @var{comm}
47442 Instruct @code{gdbserver} to display extra status information about the debugging
47444 This option is intended for @code{gdbserver} development and for bug reports to
47447 @item --remote-debug
47448 Instruct @code{gdbserver} to display remote protocol debug output.
47449 This option is intended for @code{gdbserver} development and for bug reports to
47452 @item --debug-file=@var{filename}
47453 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
47454 This option is intended for @code{gdbserver} development and for bug reports to
47457 @item --debug-format=option1@r{[},option2,...@r{]}
47458 Instruct @code{gdbserver} to include extra information in each line
47459 of debugging output.
47460 @xref{Other Command-Line Arguments for gdbserver}.
47463 Specify a wrapper to launch programs
47464 for debugging. The option should be followed by the name of the
47465 wrapper, then any command-line arguments to pass to the wrapper, then
47466 @kbd{--} indicating the end of the wrapper arguments.
47469 By default, @command{gdbserver} keeps the listening TCP port open, so that
47470 additional connections are possible. However, if you start @code{gdbserver}
47471 with the @option{--once} option, it will stop listening for any further
47472 connection attempts after connecting to the first @value{GDBN} session.
47474 @c --disable-packet is not documented for users.
47476 @c --disable-randomization and --no-disable-randomization are superseded by
47477 @c QDisableRandomization.
47482 @c man begin SEEALSO gdbserver
47484 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47485 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47486 documentation are properly installed at your site, the command
47492 should give you access to the complete manual.
47494 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47495 Richard M. Stallman and Roland H. Pesch, July 1991.
47502 @c man title gcore Generate a core file of a running program
47505 @c man begin SYNOPSIS gcore
47506 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
47510 @c man begin DESCRIPTION gcore
47511 Generate core dumps of one or more running programs with process IDs
47512 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
47513 is equivalent to one produced by the kernel when the process crashes
47514 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
47515 limit). However, unlike after a crash, after @command{gcore} finishes
47516 its job the program remains running without any change.
47519 @c man begin OPTIONS gcore
47522 Dump all memory mappings. The actual effect of this option depends on
47523 the Operating System. On @sc{gnu}/Linux, it will disable
47524 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
47525 enable @code{dump-excluded-mappings} (@pxref{set
47526 dump-excluded-mappings}).
47528 @item -o @var{prefix}
47529 The optional argument @var{prefix} specifies the prefix to be used
47530 when composing the file names of the core dumps. The file name is
47531 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
47532 process ID of the running program being analyzed by @command{gcore}.
47533 If not specified, @var{prefix} defaults to @var{gcore}.
47537 @c man begin SEEALSO gcore
47539 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47540 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47541 documentation are properly installed at your site, the command
47548 should give you access to the complete manual.
47550 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47551 Richard M. Stallman and Roland H. Pesch, July 1991.
47558 @c man title gdbinit GDB initialization scripts
47561 @c man begin SYNOPSIS gdbinit
47562 @ifset SYSTEM_GDBINIT
47563 @value{SYSTEM_GDBINIT}
47566 @ifset SYSTEM_GDBINIT_DIR
47567 @value{SYSTEM_GDBINIT_DIR}/*
47570 ~/.config/gdb/gdbinit
47578 @c man begin DESCRIPTION gdbinit
47579 These files contain @value{GDBN} commands to automatically execute during
47580 @value{GDBN} startup. The lines of contents are canned sequences of commands,
47583 the @value{GDBN} manual in node @code{Sequences}
47584 -- shell command @code{info -f gdb -n Sequences}.
47590 Please read more in
47592 the @value{GDBN} manual in node @code{Startup}
47593 -- shell command @code{info -f gdb -n Startup}.
47600 @ifset SYSTEM_GDBINIT
47601 @item @value{SYSTEM_GDBINIT}
47603 @ifclear SYSTEM_GDBINIT
47604 @item (not enabled with @code{--with-system-gdbinit} during compilation)
47606 System-wide initialization file. It is executed unless user specified
47607 @value{GDBN} option @code{-nx} or @code{-n}.
47610 the @value{GDBN} manual in node @code{System-wide configuration}
47611 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47613 @ifset SYSTEM_GDBINIT_DIR
47614 @item @value{SYSTEM_GDBINIT_DIR}
47616 @ifclear SYSTEM_GDBINIT_DIR
47617 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
47619 System-wide initialization directory. All files in this directory are
47620 executed on startup unless user specified @value{GDBN} option @code{-nx} or
47621 @code{-n}, as long as they have a recognized file extension.
47624 the @value{GDBN} manual in node @code{System-wide configuration}
47625 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47628 @ref{System-wide configuration}.
47631 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
47632 User initialization file. It is executed unless user specified
47633 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
47635 @item @file{.gdbinit}
47636 Initialization file for current directory. It may need to be enabled with
47637 @value{GDBN} security command @code{set auto-load local-gdbinit}.
47640 the @value{GDBN} manual in node @code{Init File in the Current Directory}
47641 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
47644 @ref{Init File in the Current Directory}.
47649 @c man begin SEEALSO gdbinit
47651 gdb(1), @code{info -f gdb -n Startup}
47653 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47654 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47655 documentation are properly installed at your site, the command
47661 should give you access to the complete manual.
47663 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47664 Richard M. Stallman and Roland H. Pesch, July 1991.
47668 @node gdb-add-index man
47669 @heading gdb-add-index
47670 @pindex gdb-add-index
47671 @anchor{gdb-add-index}
47673 @c man title gdb-add-index Add index files to speed up GDB
47675 @c man begin SYNOPSIS gdb-add-index
47676 gdb-add-index @var{filename}
47679 @c man begin DESCRIPTION gdb-add-index
47680 When @value{GDBN} finds a symbol file, it scans the symbols in the
47681 file in order to construct an internal symbol table. This lets most
47682 @value{GDBN} operations work quickly--at the cost of a delay early on.
47683 For large programs, this delay can be quite lengthy, so @value{GDBN}
47684 provides a way to build an index, which speeds up startup.
47686 To determine whether a file contains such an index, use the command
47687 @kbd{readelf -S filename}: the index is stored in a section named
47688 @code{.gdb_index}. The index file can only be produced on systems
47689 which use ELF binaries and DWARF debug information (i.e., sections
47690 named @code{.debug_*}).
47692 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
47693 in the @env{PATH} environment variable. If you want to use different
47694 versions of these programs, you can specify them through the
47695 @env{GDB} and @env{OBJDUMP} environment variables.
47699 the @value{GDBN} manual in node @code{Index Files}
47700 -- shell command @kbd{info -f gdb -n "Index Files"}.
47707 @c man begin SEEALSO gdb-add-index
47709 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47710 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47711 documentation are properly installed at your site, the command
47717 should give you access to the complete manual.
47719 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47720 Richard M. Stallman and Roland H. Pesch, July 1991.
47726 @node GNU Free Documentation License
47727 @appendix GNU Free Documentation License
47730 @node Concept Index
47731 @unnumbered Concept Index
47735 @node Command and Variable Index
47736 @unnumbered Command, Variable, and Function Index
47741 % I think something like @@colophon should be in texinfo. In the
47743 \long\def\colophon{\hbox to0pt{}\vfill
47744 \centerline{The body of this manual is set in}
47745 \centerline{\fontname\tenrm,}
47746 \centerline{with headings in {\bf\fontname\tenbf}}
47747 \centerline{and examples in {\tt\fontname\tentt}.}
47748 \centerline{{\it\fontname\tenit\/},}
47749 \centerline{{\bf\fontname\tenbf}, and}
47750 \centerline{{\sl\fontname\tensl\/}}
47751 \centerline{are used for emphasis.}\vfill}
47753 % Blame: doc@@cygnus.com, 1991.